Air India Flight 171 Crash [Megathread 3]
Posted by usgapg123@reddit | aviation | View on Reddit | 1484 comments
This is the FINAL megathread for the crash of Air India Flight 171. All updates, discussion, and ongoing news should be placed here.
Thank you,
The Mod Team
Megathread 1
Megathread 2
Shoddy-Drawer-6237@reddit
About the Boeing 787 crash
Ok, the fuel switch was turned off manually. What about the lights flickering and loud bang heard by the survivor?
TheFrugalEngineer@reddit
Why are more people not talking about this?:
There are at least two instances in recorded history where these exact switches in a 767 were accidently moved (INADVERTENT ENGINE SHUTOFF PROMPTS F.A.A. ORDER ON BOEING 767'S - The New York Times). After the incident in 1987, the guards were installed to HELP prevent this (not completely avoid it).
Here's an excerpt:
"As the plane was climbing out over the ocean, a television-like display informed the pilots of a malfunction in the electronic system that was controlling the engines automatically.
The captain decided to revert to manual control and reached down to a panel of controls between the seats of the two pilots, with the evident intention of pushing the two buttons that turn off the electronic devices. Instead, he pulled two fuel levers just above the engine-control buttons, cutting off fuel to the engines.
The plane began descending toward the water as the crew quickly initiated the procedures to restart the engines. By the time they had restored normal power, the plane was 500 or 600 feet above the waves. An Earlier Incident
The Government order said that it was the second incident involving a Boeing 767 in which both engines had been briefly shut down at low altitude while the crew was evidently seeking to switch the buttons for electronic or manual engine control. After the previous incident, which occurred in March 1986, an operations bulletin was issued reinforcing crew training."
railker@reddit
Well let's get right on a summary of what we know and what we don't. Hopefully this can serve as a quick-stop for all the high-points of known topics. Please add comments and recommend additions or corrections! I'll get to them as I can.
I am a mechanic but I am not type certified on the Boeing 787, this is all just knowledge collected through the wonderfully knowledgable contributors on the other two megathreads and a copy of the FCOM from Google and what limited information it has.
Official Reports and The 'Black Boxes'
Unofficial Reports
Elements of the Flight
Technical Notes
IggyBG@reddit
Just thinking out loud here, and trying to process your summary. Can maybe TCMA be cause of this? It appears that landing gear has started to retract. Is there a slim change that malfunction in the landing gear caused them to get stuck, and then send signal that there is a weight on them?
Tslover1389@reddit
My thoughts as well. Accidental triggering of ground-mode immediately upon commanding gear retraction resulting in transient logic behavior that caused TCMA to activate simultaneously despite engine throttles not being moved.
bonoboboy@reddit
Doesn't the thrust have to be idle as well for TCMA to shut down the engines? That would be two sensors(?) misfiring, right?
Tslover1389@reddit
As designed, yes, thrust must be set to idle. But as was seen in the ANA Osaka accident, TCMA can still activate without all the logical conditions set to bool-true. Boeing calls such an event “transient logic behavior,” but in essence, the software as designed has edge cases where certain conditions can lead to unintended activation even when not all logic checks are met. In the ANA incident, engine shutdown occurred due to a rapid change in thrust position (rapid reverser activation) overriding the weight-on-wheels ground mode logic check, even though TCMA is supposed to only activate when ground mode is active. In this case, I am hypothesizing that a rapid change from ground mode on, to off, to back on again (due to sensor failure during gear retraction), could have lead to transient logic behavior that triggered TCMA without the engine throttles ever being touched.
bonoboboy@reddit
Turned out to be simpler.
Tslover1389@reddit
Yep. Occam’s Razor prevails once again.
bonoboboy@reddit
Very interesting.
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allielhoop@reddit
That would be insanely sad if that's what happened. Overengineering!
wolf_of_walmart84@reddit
Stab pos xdcr fault question. I noticed that the plane had maintenance done immediately before the tragic flight due to a “stab pos xdcr fault”. After looking at pics of the cockpit I notice that the fuel cut off switches are right next to stab switches. And lever. So, would maintenance have been tinkering with stuff right beside the fuel cut off switches several hours before there was a fuel cut off switch issue? I understand that the physical switch is impossible to inadvertently move, but those switches just have electrical contacts and wires. What are the chances the maintenance team mucked something up while fixing the fault. Leave a tool or conductive material behind… computer thinks the switches have moved because of an electrical problem. Doesn’t matter how robust the switch is if the wires they switch are damaged. Would explain why the pilot said he didn’t flick the switch…
railker@reddit
I don't know the 787 so I can't be 100% certain, but the name of it makes me believe it's a transducer (XDCR) attached to the horizontal stabilizer to relay its position to the Flight Controls display in the front of the aircraft. First place to point my flashlight with that error would be that transducer, only thing I'd touch in the cockpit would be the reset button and make sure it doesn't come back -- but there's proper Fault Isolation Manuals and steps to carry out for errors like these, and report says that was followed and the fault was cleared. But that's just speculation on my part without knowing the systems better.
wolf_of_walmart84@reddit
That’s fair, I wasn’t thinking it was likely as I haven’t read it anywhere and seems likely someone smarter than me woulda picked up on it. Thanks for taking time to explain. Must be cool fixin planes!!!
railker@reddit
It has its days. It's fun when you're changing an engine, it sucks when you're cleaning all the gunk from under the floor for 4 days so you can inspect the structure. 😅
Cheers, have a good one! And happy cake day! 🍰
PunkAssBitch2000@reddit
I believe the confusion/ misinformation about the pilots seat breaking comes from a previous Air India incident in 2018, where the pilots chair collapsed during the take off roll, resulting in a tail strike, and collision with an antenna or perimeter wall. No loss of life or hull.
DutchBlob@reddit
Wasn’t there a LATAM 787 a year or so ago that nosedived after the (co)pilot’s chair slid forward and pushed the throttle down?
Techhead7890@reddit
Looks like it yes: https://en.m.wikipedia.org/wiki/LATAM_Airlines_Flight_800
AirPleasant5311@reddit
Yes, it was confirmed the flight attendant pushed the a chair button which made the pilot press on the yoke.
Makes you wonder which button was she pressing.
Elyucateco_salsamaya@reddit
Yeah and the pilots, and everyone on the plane said, all the power went off inexplicably. That is NOT explained by the chair/yoke push. It was never addressed in the report.
railker@reddit
As the seats can be moved in/out of the at-the-controls position, and they can be electrically or manually moved, there's a rocker button on the back of the seat under a cover that can be used to move the seat. The cover over that button was reportedly broken or defective.
As part of the failsafes, as mentioned, manual override. But also there's a cutout switch I believe pilots are trained on for the very situation of 'uncontrolled seat movement'.
Hot_Net_4845@reddit
IX611 TLDR because i got interested: seat back fails, Captain falls back, instinctively grabs the yoke and throttle, throttle is reduced from 98% N1 to 77, F/O is given controls, Captain regains hiself and takes control back, 1000ft to the end of the runway the Captain rotates, the 737 suffers a tail strike, takes out some lights, the localizer, and a brick perimiter wall
https://asn.flightsafety.org/wikibase/319549
KsiShouldQuitMedia@reddit
TIL planes are way more durable than I thought. That 737 said "brick wall? I laugh at your brick wall!"
Sad-Performer957@reddit
Remember when the boeing 707 did a barrel roll in 1955? This was at a time when planes used to fall apart just from flying.
https://youtu.be/Ra_khhzuFlE?si=iaVO1DABYmtbT6bb
ALLCAPS-ONLY@reddit
My I wish I experienced a time where you could just pull a sick one-liner and get away with doing crazy shit like this on the job
Silent-Treat-6512@reddit
You need to work for Boeing for that.. what are you doing there are mechanical faults with engine... them "Selling Planes"
Sad-Performer957@reddit
You can still probably get away with it if it helps selling more stuff lol.
railker@reddit
This Fairchild Metroliner and a Cirrus SR22 had a mid-air mating ceremony a number of years ago while on approach.
SR22 had a parachute and landed safe thankfully. Pilot of this poor Metro (cargo, no pax thankfully) just thought he lost an engine and continued with his landing. Can only imagine getting out of your plane to see that.
phluidity@reddit
Despite being very light for their size, airliners are still incredibly massive.
At takeoff, an airliner can weigh over 200 tons (the 787 is over 250 tons). And it is going 160 miles an hour. Compare that to the standard benchmark for crashing through brick walls, the Sherman tank which weighs about 33 tons and has a top speed of 25 miles an hour.
losttraveller23@reddit
Check out the QR 777 that hit some airport infra after take off, iirc departing from MIA. There was a huge tear in the tail section and the damn plane flew 13-14 hours to DOH.
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professorfunkenpunk@reddit
I just saw the Mentour Pilot video of that yesterday
External_Weird_8251@reddit
I thought it came from some fake doc floating around (dated June 25, 2025 at that) blaming the seats?
KeepItPositiveBrah@reddit
There was a 787 issue as well where the seat went forward and they accidentally turned off AP and the plane rapidly decended 400 feet
railker@reddit
The seats on the 787 can move in and out of position by switches on the side like your car, but because they can be stowed into a position where you can't get into them, there's a rocker switch on the back as well, with a cover.
That cover was broken and a Flight Attendant leaned on it, in that case.
fly_awayyy@reddit
That’s cause a FA accidentally pushed the button on the back of the chair…
railker@reddit
I'd initially corrected someone the text of the claim was from the PDF posted to the Greek news site initially linked with the claim, but you're absolutely right, I need to go apologize to someone brb.
https://www.key.aero/article/air-india-express-737-hit-wall-take-after-captains-seat-reclines
SchleppyJ4@reddit
“For those not in the know, Service Bulletins are optional. Airworthiness Directives are mandatory”
Out of curiosity, how often would you say service bulletins are followed?
railker@reddit
I imagine it's probably tied to cost-benefit. AD is hazardous to the airplane and tied to safety (though it can be triggered by and/or accompanied by a service bulletin). A standalone SB only is typically just stuff like 'Hey, you know how your air conditioning pack oil is dummy hard to drain? You can modify yours with this drain adapter that makes your mechanics hate their lives a little less. If you wanna pay for it.' Often involves things that are just integrated into the production line but only when you've already delivered 200 airplanes so now you've got 2 versions of a thing.
Urmomzahaux@reddit
This reminds me of the one time I made a very small change to make a maintenance check performed periodically much easier, but the change is connected to something with a prior AD, so it automatically is AD related, and when a SB is AD related it’s mandatory, so the whole fleet had to be retrofitted with my update even though the update has zero function outside of maintenance and the only impact on the aircraft is a weight increase equivalent to the weight of my big toe. So, things are very conservative in that way.
Nice_Classroom_6459@reddit
The critical factor is regulatory: AD's can be enforced by law (including revoking the aircraft's certificate to operate). SB's cannot.
ProfessionalRub3294@reddit
Can confirm. I worked in a low cost airline and there was the case of an APU improvement that avoid a regular replacement of a piece. They preferred collect a big stock of those parts from airline that made the modification (to have spare for years at discount price) rather than go for the proposed modification.
SchleppyJ4@reddit
Gotcha, that makes sense. Thanks for the response.
Also, much love to mechanics like yourself; my grandfather was one and his love of planes lives on in me.
railker@reddit
Ay, thank you! Happy to hear, what a thing to love. Watching an airliner take off over your head never gets old. 😁
CollegeStation17155@reddit
Well, service bulletins are usually followed “eventually” at the next major overhaul, for instance. Airworthiness Directives are a “Do it NOW” kind of thing… for example Boeing issued a service bulletin last year advising 787 operators to inspect seals between the crew cabin and electronics bay below it to insure that a leak in the plumbing would not drain into the electronics and the operators just added the item to their maintenance schedules to be done over the next year or so. But probably the crash made some bureaucrats decide that the possibility that engine controls could be shorted at rotation rated an upgrade to an IMMEDIATE inspection of the entire fleet.
Numerous_Lifeguard_6@reddit
Im willing to bet it's a dual FADEC failure caused by a bus transfer failure as struts extended. A single common point for the failure which would cause the RAT to drop and engines to roll back to ground idle. No way to throttle up.
Nyungwe23@reddit
Indian TV is reporting both the cockpit voice and the flight data components of the black box ( I understand the two black boxes on the 787-8 are essentially exact duplicates of both voice and data (for redundancy) and one of them was severely damaged while the other is good) and, this is the crucial part, the data has been apparently “ successfully “ downloaded at a lab in Delhi and is now in the analysis phase. Team led by Indian authorities, and US NTSB personnel are also involved.
https://www.youtube.com/live/fDG27UMw4wg?si=tt05S1-7HY_CU-6N
SliceMountain6983@reddit
In no way, shape, or form had gear retraction begun.
Step 1 of 787 gear retraction is the main gear doors swinging down. They clearly were up in the infamous rooftop video.
I'm convinced this is an issue with the weight-on-wheels indication and its interplay with TCMA. Some corner case caused TCMA software to bring the engines back to idle.
railker@reddit
Can't find the write-up at the moment, but as I understood it as there are no sequence valves, the gear door 'opening' and the tilt of the landing gear in preparation for retraction are simultaneously initiated (at least on the 787-8, whereas the -9 and -10 automatically pop the gear doors open after rotation).
The accepted indication of the gear retraction initiated was based on a fairly clear forward tilt in the video (the one that isn't screen recorded), as visually compared to the continued aft tilt of gear that hasn't been initiated up, as when you'd see when brakes are a bit hot and crews leave the gear down for a while after takeoff. Another example, both videos of non -8s where the doors auto-open. Fuck me if I can find a -8 with hot brakes.
Watch a gear swing carefully, and note the exact moment that the tilt initiates, the doors 'pop' as they unlock. Sequence initiated.
And even watching an older video of the exact accident aircraft, the gear door opening and truck tilt appears to be simultaneous.
Or this one of another Air India aircraft, where the tilt is fully completed long before the gear doors are fully open, leaving them hanging out for a bit before they can retract. Also uneven retraction ayyy.
Or this one at 2:54, again, tilt fully completed and doors still opening, for the sake of including one not from Air India.
SliceMountain6983@reddit
Thank you for the downvote. I returned the favor.
railker@reddit
Go through your linked video slowly, 1/2 speed works nicely to watch the sequence.
The tilt happens between about 0:49-0:50 to about 0:51 when it appears they stop moving and wheels are 'level' instead of 'front up'.
The gear door is first visible at about 0:51 and the doors aren't fully open until 0:54-0:55, and retraction doesn't begin until 0:55. There is zero motion in that bogey while the doors complete their opening after that 0:51 mark.
Just to be clear we're talking about the same thing and find some common ground here, because you're not entirely wrong: Yes, the doors would have to open for the main gears to physically retract. The physical action of the gear retracting had not started, not a single person anywhere on this planet is claiming that. The retraction SEQUENCE, involving opening the doors AND tilting the bogeys, appears to have started.
I can 100% see how the visibility of the tilt could be uncertain. I think this makes it fairly clear and hopefully brings you to the same page as all the pilots and mechanics I've seen comment on it, and my own eyeball judgment in comparing one of these things to the other. Screenshot from the Air India 171 video in the middle.
I swing gear IRL on commercial aircraft, sequences can get funky. If you do too, then great, let's discuss like adults. Everything I'm seeing indicates the gear was tilted. Aft wheels closer to the wing than forwards. Why anything else happened after that, or rather why the doors DIDN'T open, is a whole other discussion reliant on acknowledging the transit position of the main gear.
exohugh@reddit
Question on Thrust Control Malfunction Accommodation (intended to shutdown runaway engines on the ground).
If the on-board software activates this TCMA shutdown... would the RAT activate? Given the RAT activation also requires software logic (something like
activate RAT IF both engines have failed OR 3 hydraulic system pressures are low OR no electrical power to flight instruments OR no EMPs OR no EMPs). But maybe they're separate logic loops?SliceMountain6983@reddit
I'm late to this discussion, but have we ruled out a faulty weight-on-wheels (WoW) indication? If the WoW signal is "in air" when the airplane is "on wheels" doesn't TCMA cut power to both engines when reverse thrust is selected? I thought that's what happened in the 2019 incident. The TCMA patent talks about what to do when the aircraft is on the ground, but it all assumes a valid WoW indication. I'm wondering about the validity of the WoW indication, per se.
I only wonder about a WoW sensor issue because it seems like whatever happened, was triggered the exact moment the WoW sensor would have switched from "on wheels" to "in air". And a faulty WoW would inhibit gear retraction.
But, I have to think there are multiple WoW sensors -- probably one in each of the three landing gear -- and a WoW miscompare will be resolved by "voting" and selecting the 2 out of 3 readings. Seems very unlikely that the FMS would have been told "on wheels" instead of "in air" but anything is possible.
My overall hunch is that TCMA and/or faulty WoW will be implicated, but I'm sure I'm wrong.
Persistant_eidolon@reddit
Interesting thoughts. It seems to me that any system with the ability to shut down both engines is a safety risk in itself, since it can lead to catastrophic failure.
phluidity@reddit
The shutdown logic is independent for each engine and runs on separate logic controllers (FADEC) built into the engine (greatly simplifying things, there are both mechanical and logic redundancies built into them). These controllers are designed such that if they lose input, they will maintain the last validated thrust command. They also have the ability to shut down the engine if they detect a fault condition that would cause a catastrophic failure if not addressed (such as an imminent engine fire as an example).
Now is it possible that there is a set of circumstances that would cause both controllers to independently think that their engine needed to be shut down? No. Yes. Maybe? We don't know. There shouldn't be one, but maybe?
SliceMountain6983@reddit
Nonetheless, the 2019 ANA incident where both engines were killed is somewhat alarming, and despite tons of Googling, I couldn't find a definitive root cause analysis. All I could find was that Boeing issued a directive telling pilots to be sure to [basically] "wait until you're definitely fully settled on the runway before selecting reverse thrust."
It seems that the TCMA killed both engines because the system determined that the pilots selected reversee thrust in the air.
What I'm wondering, specifically, is whether the WoW sensor failed to toggled from "in air" to "on wheels" and when reverse thrust was selected, TCMA killed the engines. This clearly wouldn't have been the case in the Air India crash, since reverse thrust would/should not have been a factor. But it made me wonder whether a faulty WoW signal combined with something else led to TCMA killing the engines.
phluidity@reddit
Given the timing of things appearing to go wrong as the gear was being raised would give plausibility to a faulty WoW signal. If the sensor was going bad or something else, the actuation of it might maybe cause something. But like you say, there would still need to be "something else". Of course it is also possible that it is just a huge timing coincidence.
The 2019 incident is certainly concerning. If it hadn't been for the MCAS debacle, I wouldn't have ever even considered the possibility that there could be a software issue this critical that Boeing decided to downplay because they either couldn't or didn't want to fix and just hoped it never became a problem.
There are some other really weird cases where apparently TCMA can initiate protect mode (for example if the fuel tank temperature goes over limit). Which is unlikely to be triggered in normal operations, but maybe with a sensor error. Which brigs us back to the odds against two different sets of sensor malfunctions at the same time are also astronomical. So unless all the sensors conditions triggered at the same time due to some common source it still doesn't work. Which doesn't make sense either, because all the common source faults I can think of (and more) are the things a third year electrical engineer would think of immediately (the one I've seen on other forums is that all these signals are low voltage and don't behave properly if they get a high voltage input. Which is why you make sure to design around voltage spikes.)
I have a sneaking feeling that the preliminary report is going to lead to more questions than it does answers, and it won't be until the final report that we understand what happened.
SliceMountain6983@reddit
So I gather from your comment that we are two engineers spitballing. I love Reddit.
I've worked in aero my whole career, mostly (20 years) for Lockheed. I appreciate all of the rigor that goes into testing, but I'm also fully cognizant of the fact that corner cases arise. Deep down, something tells me the Air India crash is a software bug.
phluidity@reddit
:)
I'm no longer in the industry, but there is something about the aero way of thinking that never leaves you. I still remember one of my profs telling us that our job was to make sure it wouldn't break, and then figure out how to make the whole thing keep working when it broke anyhow.
SliceMountain6983@reddit
Yep, "belt & suspenders" solutions!
phluidity@reddit
My wife still jokes that when I fix something around the house she knows it is going to take me five times longer than it needs to, but at least it won't break.
Wonderful_Present_16@reddit
This was my hunch too. Literally my argument as well with a bunch of folks. There is a particular edge case that’s not been covered in test (also a software engineer).
I still didn’t understand how having two process subsystems for redundancy but if one fails for what ever reason the other have full authority to go ahead with TCMA.
Mediocre_Address7965@reddit
But the landing gear retraction has partially begun already, before stopping for whatever reason, as the info above states?
SliceMountain6983@reddit
Step 1 of 787 gear retraction is the main gear doors swinging that. That's clearly not shown on the infamous "rooftop video." In no way, shape, or form had the "gear up" sequence begun.
Dr__KW@reddit
Dual engine flameout or power issue memory item would be RAT, right? Those guys had enough hours I'd assume the min they had issues they deployed it themselves, if not on it's own.
SliceMountain6983@reddit
I'm not a transport-rated pilot, but I'm a general aviation pilot with friends who do fly jets. My impression is that this all happened so fast that there wasn't time for emergency checklists, which is what you'd need for a manual RAT deployment. This was essentially something going wrong on rotation, and at that point it's all muscle memory and very basic "fly the airplane" stuff that they've practiced in the simulators. There wasn't time to do much more than manipulate the flight controls, manage power settings, and avoid obstacles.
lannoylannoy@reddit
Could TCMA stop engines if a hydraulic failure interrupted landing gear up and false simulates the runway - ie what type of mechanism establishes that the plane is on the ground?
DrSpaceman575@reddit
I don't know if it would have to explain that. In the event both engines shut down I would forgive nearly any action by the pilots - they could manually deploy the RAT or give commands that might create conditions for it to be deployed.
I would note the other instance of TCMA shutting down engines on a 787 happened on touchdown but they were unable to restart the engines and had to be towed off the runway after 40 minutes.
dannhah@reddit
This may be of interest.
https://patents.google.com/patent/US6704630B2/en
Nyungwe23@reddit
Why has the Cockpit Voice Recorder audio not been released as of June 21 end India time, even though the Indian authorities have had and apparently reviewed it at least 72+ hours ago. Understand the main Black box ( FDR) with all the flight details is damaged in the crash fire and discussion is on to send to the US for recovery of information. But given the growing mystery and increasingly likelihood of a technical issue possibly related to fuel contamination but many other possibilities, and the obviously critical need to release any data that might result in fixes for the existing global 787 fleet, am I missing something? How come the US and other international authorities are not demanding speeding up the process, unless the information available is already shared with them, just not the public, which is ok. At least say available data from the CVR has been analyzed and shared with FAA etc.
railker@reddit
I doubt the audio going to be released. That doesn't happen anymore. The transcript may be released, in part, with the preliminary report, but in the case of the Voepass crash in August, they only released the timestamps and notes (i.e. "PIC makes a comment about xyz").
Where and why is still a mystery, news is unreliable. Sources stating it's being sent to the US, then it's not, they're still calling them FDR and CVR even though each box is both (FDR+CVR = EAFR). I haven't seen anything saying the CVR's been opened and transcribed yet, if you have I'd love to see it so I can update the comment.
The NTSB, CAA and others are right there in India with the investigators as a team, they know exactly what's going on and want answers more than you can ever possibly want them, because they're there at ground zero and also want nothing more than to find any clue that might point to either knowing this was a one-off or if there's a widespread issue.
LankyAspect9594@reddit
I am very much convinced that it was indeed a dual engine failure. Audio and Video very much confirms this theory as well.
No other way its possible for a 787 to lose lift all of a sudden.
serrated_edge321@reddit
Dual engine failure without something like bird/hail strike or icing should be crazy unlikely (probability-wise), but I agree that it's most likely something in that direction.
It would be more likely that someone purposely or via gross negligence caused a problem with the engines/ related systems. Humans are far less reliable than the very redundant designs of the gas turbine propulsion systems.
Busy_Comedian_8165@reddit
Most airlines crash causes seem crazy until the first one happens. The BA 777 at Heathrow, German wings, Hudson, 9/11, to name a few
daern2@reddit
I always find it interesting when one (9/11 - secure cockpit doors) lead directly to another (Germanwings 9525). I was intrigued to read that the mitigation for this - always having a member of cabin crew in the cockpit if a pilot would otherwise be left alone - appears to have been abandoned in recent years. Wonder what the reasoning for this is...?
railker@reddit
I covered what I found looking into this a bit in these comments, TL;DR it's a concept that sounds nice to the general public but as with many things in aviation, it's a bit more complicated.
daern2@reddit
Yeah, I assumed it was something like that. I suppose it's one of those ideas that sounds better on paper than it works in the real world, which I completely understand.
I guess it would be nice for the purser to have an override key to get in, but a bit like with everything in security, as soon as a backdoor is present, the whole security monolith comes crashing down completely. I do still think of those poor passengers and crew trying desperately to break through an armoured door while knowing that their fate is probably sealed anyway. Bloody dreadful, and hopefully it doesn't ever happen again.
railker@reddit
And we have to treat the cockpit as the most important place to keep secure, there was a US flight on which the Captain had a mental break and by chance or convincing left the cockpit long enough for the FO to get another pilot who happened to be on board in the left seat. Then the Captain tried to get back in.
There are ways and there's airlines that do the risk analysis and either have a second person or perform other measures, but we start getting into security-sensitive information.
Absolutely hope that has and will continue to drive changes and ensure it doesn't happen again.
serrated_edge321@reddit
Well I work in the industry, so I suppose I think about it differently.
There's testing done and vehicle design / pilot / operational requirements written to try to prevent any of the situations you've heard of. So none of them seem that "crazy" when they happen again... Just some are more unlikely than others.
ECrispy@reddit
Human negligence is very unlikely to cause dual engine loss. If it can, it just means a system defect. It's like allowing your car engine to stop if you didn't wash the windows.
serrated_edge321@reddit
"Gross negligence" would include mechanics doing a really shitty job, which does happen more often than people would like to think. But for dual engine failures... It's a really curious situation. Air India is known for problematic practices in all levels of their organization, so wouldn't be too surprising if it's maintenance related.
I keep tending towards "sabotage" mentally (given today's politics), but let's see what the reports say...
Persistant_eidolon@reddit
There was some important Indian guy on the plane, right?
ignited-eyes@reddit
Chief minister of Gujarat, yes.
Phemmert@reddit
It’s worth noting that there have been multiple instances of pilots shutting down the wrong engine in the event of an engine failure. Given that, pilot training and strict adherence to checklist discipline have been a training emphasis over the years, to prevent unintended engine shut downs.
Rivet_39@reddit
The C-5 crash at Dover comes to mind, though there were other mistakes as well in that accident.
serrated_edge321@reddit
This would fall under "human error" though, not negligence.
When I said "gross negligence" this means more like failure to correctly do maintenance activities (ie doing a really shitty job, not accidentally making one action).
LankyAspect9594@reddit
I totally understand that the probability of having a dual engine failure is statistically insignificant in the modern systems. The cause of dual engine failure can be anything, most likely (still very low prob) reason is pilot suicide.
However, there is new data coming in that suggest that AI171 took almost 3.5 km for takeoff (almost full runway), so this case has become further confusing.
serrated_edge321@reddit
It's really awful to outright start by pointing fingers at pilots like that! Please don't do that in the future.
There's a lot of people involved in airline operations and maintenance, and there's many potential mechanical failures and places for human errors/intentional actions to cause such problems.
My mind goes first to sabotage by someone with access to the aircraft, given the current political situation between India and Pakistan. My second guess would be maintenance-related issues or something stupid like a pilot seat that moved suddenly, taking the pilot's hand (on the throttles) back with it.
an_actual_lawyer@reddit
I think that maintenance personnel overriding this safety feature, perhaps via disabling it if it was acting up and they couldn't fix it or didn't have a part, is a leading candidate.
Tslover1389@reddit
Maintenance personnel cannot disable TCMA. And regardless, TCMA is designed to shut engines down in the event of engine runaway. If it were disabled, it wouldn’t have impacted anything that could have led to loss of thrust from both engines (which is the leading theory at the moment).
Lost-Inevitable42@reddit
Yeah, but is 'dead fuel pump' or 'computer logic failure' (all hypothetical) considered 'dual engine failure'? Both engines were either off or not producing sufficient thrust. But, what caused that?
CATIIIDUAL@reddit
On Jun 17th 2025 an official, a former Air India Captain trained by the Captain of the accident flight, stated, that the CVR has been successfully read out, the voices on the CVR are very clear. It is becoming gradually clear from the newly emerging evidence that there was probably zero negligence in the cockpit, the crew did not give up until the very last moment. The probability of a technical cause is high. A preliminary report by India's AAIB can be expected in a few days.
-From Aviation Herald-
CrazyCletus@reddit
Wasn't Aviation Herald the site that rewrote the narrative of the Germanwings incident?
RealPutin@reddit
Yes, and they were also calling the Azerbaijan shootdown theory anti-Russian propaganda many days after most experts agreed what happened.
An unnamed biased source via another biased source without the actual CVR data should be taken with a massive grain of salt
sadChemE@reddit
They're sending the black box to the US per reports today due to damage and being unable to extract the data, so im gonna go out on a limb and say you are correct on your guidance regarding the source here.
Better-Ad6812@reddit
Oh dear
Bananasinpajaamas@reddit
So heartbreaking for those pilots, I cannot imagine. They were in an impossible situation.
throwaway-a0@reddit
I think the point here is not that Air India has somehow neglected to implement the AD, but that the 787 has a history of similar problems, so a new one of that type should not be surprising.
248 days GCU counter overflow (addressed by AD 2018-20-15)
22 days FCM counter overflow (addressed by AD 2020-20-09)
51 days CCS rounding error (interim AD 2020-06-14)
railker@reddit
I think it's fair to agree, but also note it's not a Boeing thing so much as a modern software thing. The A350 has had a few issues with similar things, I remember a 140-something day reboot cycle being mandated for it for a similar software integer type thing, and some AD about the software mistakenly thinking the elevator actuators were inop.
But absolutely, some unexpected combination of things could trigger an unexpected reaction.
Nice_Classroom_6459@reddit
It's actually un-modern software, as modern programming practices take these kinds of limits into account and use custom data types or address the overflow directly in code.
It's actually lazy programming to allow a buffer overflow; what's happening is the hardware is stopping you from exceeding the limits you asked for in your own data type. eg, you pick a 32-bit unsigned integer. The number in your variable hits 4.29... billion. You roll over the final value in the data space, and the hardware immediately halts to protect the system from your shitty code.
m-in@reddit
So, basically, those things are digital flight control engineering 101. I’ve heard about them and had a training that talked about it and I’m not even doing flight controls, just embedded software.
RealPutin@reddit
I used to do CLAW work (not at Boeing) and while yes it's flight control 101, a small handful of those do exist on most FBW aircraft in the first iteration.
Isord@reddit
"The Airworthiness Directives relating to the potential loss of all AC power due to an aircraft being powered on for 248+ days"
Is it normal for an aircraft to remain powered on for that long? That seems so strange to me.
Chen932000@reddit
No it was a robustness test case Boeing found. The AD was issued since the consequences were severe, despite there not being any evidence of this amount of time ever having occurred.
SliceMountain6983@reddit
I won't name my employer, but when we found similar bugs during multi-day stress tests in our cockpit mockup, we'd joke that it wasn't really a problem since there's "no way a flight would last that long, so ship it." (Not really, though. We'd obviously fix it.)
Chen932000@reddit
Depending on the criticality of the error I could see it being left in. This one was particularly bad so yeah they fixed it. But if it was benign and extremely improbable to occur it would be left there or fixed at next opportunity only.
Nyungwe23@reddit
Wall Street Journal in the US has a story on this today. Main point is “ Investigators believe Air India Flight 171 had an emergency-power generator operating when it crashed last week, raising questions about whether the plane’s engines functioned properly during takeoff. The preliminary finding, according to people familiar with the probe, gives investigators a new line of inquiry as they study a crash that killed all but one of the plane’s passenger”
Rest of the article repeats stuff about RAM deployment etc already known.
Nyungwe23@reddit
Wall Street Journal in the US has a story on this today. Key excerpts:“ Investigators believe Air India Flight 171 had an emergency-power generator operating when it crashed last week, raising questions about whether the plane’s engines functioned properly during takeoff. The preliminary finding, according to people familiar with the probe, gives investigators a new line of inquiry as they study a crash that killed all but one of the plane’s passenger”
“ And despite investigators’ early finding about the RAT, the people familiar with the crash cautioned that the probe is ongoing. Investigators haven’t confirmed whether engine, hydraulic or other problems triggered the emergency system.”
shinealittlelove@reddit
Interesting, that's the first time I remember seeing the TCMA mentioned anywhere
Fatal_Explorer@reddit
Some of us tech guys in the industry have been debating it quite a bit here in the recent days. We're still trying to obtain manuals on it.
railker@reddit
I just submitted a new comment to the thread to help get some extra info -- looked at the Transport Canada MMEL for the first time and the TMCA is in there, but highlighted as an RR engine system specifically. VT-ANB has GEnx-1Bs, so unless otherwise specified, likely didn't even have the TCMA. ANA had the RRs.
Fatal_Explorer@reddit
Good job!
Unusual_Ad_6612@reddit
I’ve read some theories in another Reddit threads and one some other aviation forums, which indicate the TCMA could play a major role in this accident.
First theory was basically that somehow TCMA just activated due to erroneous sensors and data, leading to the shutdown of both engines after takeoff.
The second was more far fetched: at around V1, something in the cockpit happens which alarms the pilots. One of the pilots rejects the takeoff, pulling the levels into idle and potentially trying to activate reverse thrust. The other pilot, not agreeing with the action, quickly moves the throttles back to TOGA and rotates at the same time. Potentially, the aircraft has enough speed to takeoff, but TCMA already kicked it when the throttles had been moved back to idle, as all conditions were met (weight on the wheels, throttles in idle, engines still running at takeoff speed).
This could all be very far fetched, as I’m not familiar with avionics - maybe someone could chime in and clarify?
Gay_Black_Atheist@reddit
Fascinating
Tslover1389@reddit
Could some electrical/sensor fault in the landing gear retraction system, triggered when the pilots commanded gear-up, have caused a rapid, mistaken switch from “air” to “ground” mode in the TCMA logic?
If so, and assuming thrust remains above the contour for idle (as it would under TOGA), couldn’t that then potentially lead to TCMA shutting down both engines due to faulty logic?
We know from the 2018 ANA Osaka incident that TCMA triggered despite ground-mode not yet being active due to unintended transient logic behavior in the thrust level logic system, so it’s not entirely out of question that the opposite could be true (rapid, erroneous triggering of the ground-mode logic resulting in TCMA activation without pilot throttle movement).
allielhoop@reddit
And Boeing didnt think of that possibility 😥. Public info on conclusions of ANA incident is limited!
RandomObserver13@reddit
One thing that might be worth clarifying…”Reports that the flaps were inadvertently raised appear to be false. Leading edge slat deployment appears to be visible.” Leading edge slats can be deployed without flaps at position 1 of the flap handle on a 787. So slats deployed doesn’t necessarily mean the flaps were deployed. It is my understanding that this setting should trigger a takeoff config warning. Not saying this happened in this incident.
railker@reddit
Appears you're right, source says valid entries for the takeoff ref page are 5, 15 or 20. Will do some updating when I get home, few things to update and add.
RandomObserver13@reddit
Well done for both the original post and the updates. Very impressive, and I’m sure time consuming. I had thought about trying to put something like that together but realized quickly how much effort it would take (and the odds I’d miss something) and noped. 😉
I’ve read a lot of aviation incident reports, and tried to figure out something simple here, and just…nothing. Not that I’m an expert or anything, but this is a real mind boggler. It looks like the worst possible thing happened at the worst possible time, which reminds me of the 737 rudder incidents. Hopefully this isn’t as hard to solve as that was.
railker@reddit
It's all thanks to people like you, we're all just sharing knowledge. None of it can give us proper answers until the preliminary, just the human desire to try and understand such a catastrophe. But yeah, can't possibly cover all the discussion topics but all the repetitive ones that kept coming up I wanted a spot for. It'd be nice to have it as part of the text of the Megathread post but that'd be mods keeping on top of all the information, too.
There's some accidents which are pretty obvious, and others are complete mysteries. Air France 447 and Voepass 2283 are the two I often refer to, both examples of few details and an immense mystery until a report was published that gave clarity to the events, expected or otherwise.
RandomObserver13@reddit
My “favorite” mystery incident is the SmartLynx A320 training crash. An almost impossible to predict scenario. Also a nice example of how pilots can sometimes pull off a miracle. In that way, kind of the opposite of AF 447, unfortunately.
Ener_Ji@reddit
FYI the below sub-bullet is not correct as TCMA applies to GE Genx engines as well. For example, see this official US DOT document (PDF, published on a US Gov site) regarding Boeing updating the TCMA software on 787 GE Genx engines:
https://downloads.regulations.gov/FAA-2016-7855-0005/attachment_1.pdf
railker@reddit
Someone else just called that out and made a hot edit to pull that back out. Curious what's different about RR that lets you run with one inop, but irrelevant here. Thanks for the note!
Nyungwe23@reddit
Indian Aviation Regulator releases statement on review of Air India operations including 787 fleet.
https://www.pib.gov.in/PressReleasePage.aspx?PRID=2137035
AmbidextrousRex@reddit
There were some reports about electrical problems, both from the survivor of the crash and about the previous leg flown by the plane. Do we know how credible these reports are?
railker@reddit
The ones regarding previous flights I believe are questionable - IFE systems aren't safety critical and can often be inoperative or just temporarily disabled on the ground, apparently lots of flight/airline reviews note broken IFEs on many Air India aircraft.
The poor AC could be attributed to the plane being hooked up to external air conditioning or the system trying to keep a metal tube cool in 38 degree heat. Comments in the other threads note that the all electric system on the 787 can struggle at times.
The electrical 'flickering' noted by the survivor could be power switching over to the RAT, same as when you switch between ground power and APU generator or that to engine generators. Any power loss also would automatically kick on the emergency lighting system until it was restored, that's possibly the green-white lights described.
MrFickless@reddit
Can confirm, 787 uses two identical EAFRs instead of separate CVR and DFDR. 1 of them is installed around door 1L, the other above the aft galley at the usual location.
railker@reddit
Door 1L? That's a new spot. 😂 Thanks for the info!
MrFickless@reddit
The A350 also has a similar configuration, as well as an optional deployable recorder at the base of the vert stab.
warrenslo@reddit
11A was by door 2L right? Allegedly the entire right side of the plane impacted the building directly and was obliterated.
Some1-Somewhere@reddit
Some info in the flight recorder section of the original 787 battery fire stuff: https://data.ntsb.gov/Docket/Document/docBLOB?ID=40388298&FileExtension=.PDF&FileName=Flight%20Data%20Recorder%2010%20-%20Factual%20Report%20of%20Group%20Chairman-Master.PDF
KOjustgetsit@reddit
I wish I could upvote this ten thousand times, thank you!
UnderwayWestward@reddit
Can the RAT deploy as a result of thrust being commanded to idle using the thrust levers? Asking to understand if the RAT deployment and the seat failure theory are compatible.
Some1-Somewhere@reddit
No. Engines at idle is a normal operating condition that happens on most approaches, and certainly while taxiing around. It won't deploy the RAT and barely affects how much power (hydraulic or electric) can be pulled from the engine.
Ricky_Ventura@reddit
More power can actually be pulled from the engines as less is used for thrust. This affects the 787 less since it doesnt use bleed air but on most other engines the difference is significant. On 4 engine planes it's common in emergencies to bring inboards to flt idle to ensure redundancy and reliability for electrical, hydraulic, and bleed air systems.
basilect@reddit
Probably not, since there are points where you might want to set thrust to idle during normal operation (like when you're landing the plane... or much less commonly, if the Autothrottle is off and you're trying to descend)
PengPenguin888@reddit
I'm afraid this whole crash will be because of murder suicide. Either pilot or Co-pilot may have purposely shut the fuel cut off switches at the perfect time... Knowing what the result would be. I hope I'm wrong.
bonoboboy@reddit
Unfortunately you got it.
Prior-Flamingo-1378@reddit
It certainly seems that way
airbusrules@reddit
Air India Flight 171 Preliminary Accident Analysis
Here's a summary of my analysis on the crash over from the / ACI sub, the update focuses on potential causes of the dual engine failure scenario, which is looking more likely right now. If anyone has more insights, interested to hear your opinions. See the previous post for more details and the images, etc
https://www.reddit.com/r/aircrashinvestigation/comments/1la62hn/air_india_flight_171_accident_analysis/
More evidence which strongly indicates a dual engine failure/flameout.
- The only survivor’s account in a more recent video (NDTV); He mentions that 5-10 seconds after liftoff that the plane seemed to be ‘stuck’ [I think that is referring to the obvious deceleration as seen in the CCTV video which would be fully explained by a significant loss of thrust]. Then he said that a bit later, ‘green and white’ lights came on [if correct, this would likely be the emergency lighting system, especially as he was sat at the emergency exit row with the signs close to him]. This fully tracks with a dual engine failure [the emergency lighting which would be armed at that stage of flight. would automatically switch if you lose the normal electrical system]. In this interview he does not mention the loud bang as reported earlier. The poor man is obviously in shock and I wish the media would give him some space.
- The distinctive sound of the RAT. There is a noise at the start of video 1 (on the versions with the original noise), which does not correspond to engine sound. This is almost certainly the RAT, based on another video of a 787 flying past with the RAT deployed. Based on the trigger conditions of the RAT, one or both engines and the electrical system would not have been working.
- The landing gear retraction (not considering the drag aspect, but the ability to even retract the gear). I think for a split second you can see the main gear starts to retract but then it stops, this is around the time that there is no longer positive climb. This would make sense in case of a dual engine failure and the switch to emergency systems means only a gravity gear extension would be possible (but no hydraulic power to actuate LG doors and retract the gear itself). As many have pointed out, the tilt of the gear is more evidence of interruption of the retraction sequence.
The reports of what the pilot communication with ATC was exactly, I’m not convinced is from an accurate source. But the Mayday call alone as I said before, shows the crew were aware of a desperate situation on board. And in case of a dual engine failure, they wouldn’t have had the chance to do much at that stage.
airbusrules@reddit
This would be unprecedented for a large commercial aircraft to have lost power completely on take-off. This is a catastrophic condition which would leave the crew with no option. The residual energy will only allow the aircraft to cross beyond the airport perimeter and inevitable crash land soon after, with no chance of return. The is why engines and aircraft have robust designs and interfaces to each other to avoid common mode failures. Independence is maintained between the two engines and their source of fuel and the engine feed system etc. Systems and their associated software that are involved in critical functions are designed to the highest Development Assurance Levels (DALs for those familiar) and have detailed safety assessments. So, it is difficult to comprehend how this may have occurred. The chances of both engines having some sort of internal failure event (same type or different) at a similar time is almost impossible [in the absence of a common external event like a bird strike, debris ingestion, volcanic ash etc...]. It is even more difficult to comprehend given the engines worked fine at the start of the take-off. And the aircraft had successfully completed a flight just before this sector with a 2-3 hour turn-aorund.
I tried to dive a bit deeper into some causes of dual engine flameout, but specific to this accident:
Hopefully, the flight data recorders which have now been recovered, will provide more information. If this is a case of complete loss of power on take-off [which is unprecedented for large commercial aircraft], it will be critical to understand quickly how this could happen, so operators, aircraft manufacturers and the airworthiness authorities can take the right steps to prevent this ever happening again.
graphical_molerat@reddit
As extremely unlikely as it is, that is still where my money is, though. Probably a software bug that was triggered by some corner case that no one thought would ever occur in real life: possibly caused by some weird deferred maintenance condition no one ever assumed would happen (but with Air India, it did).
No other cause (apart from suicide by the pilot flying) has as much potential to suddenly and symmetrically kill both engines like this, right after a major status change for the plane (wheels no longer on ground). Even fuel contamination would likely lead to a window of a few seconds between the two engines croaking.
artmorte@reddit
Same here, my bet would be on a software bug.
graphical_molerat@reddit
Fully agree with you re: the pilot flying doing this intentionally to commit suicide being just a very very remote possibility. I only mentioned this because this is the one other scenario that accounts for all observed facts. Short, as you say, of the Mayday call. Which I agree would almost certainly not have been made if the PF had just intentionally killed the engines.
However, an unlikely but theoretically possible scenario is if the PF had intentionally killed the fuel supply to the engines with suicidal intent, thereby shutting them down, and the captain had not actually seen him hitting those switches. Maybe because he was looking out of the window at the time. Or monitoring his instruments.
Then, him sensing the engines dying, and setting off a Mayday call, would make sense even if the PF was responsible. With the remaining struggle in the cockpit until impact only being on the CVR.
Something to consider is that if you wanted to commit suicide with an airliner these days, killing the engines right after rotation in a city airport with no fields or roads for a survivable crash landing is one of the few remaining options that are more or less guaranteed to work. What with procedures about two persons always having to be in the cockpit having been put in place after the Germanwings fiasco, and so on.
bonoboboy@reddit
Reminds me of that Arthur Conan Doyle/Sherlock Holmes quote:
CollegeStation17155@reddit
This would be supported to some extent by the direct impact on the hon the hostel… looking at google earth, note that a wingspan to the left is an empty lot while to the right are low trees and a road. Either would have given those on board and on the ground a somewhat improved chance of survival.
AmbidextrousRex@reddit
I wonder how effective the "two people in the cockpit" rule actually is in practice. Even assuming it is always followed, how effective is a flight attendant going to be at preventing a pilot from crashing the plane?
Existing-Help-3187@reddit
Its not a rule. My previous airline and the current one doesn't have this rule. I am always alone in the cockpit when the other pilot goes out.
Get_Breakfast_Done@reddit
If we're talking about something happening at cruise altitude, surely the flight attendant can let the other pilot back into the cockpit.
AmbidextrousRex@reddit
I guess on an Airbus where flight envelope protections are always active, it might make things difficult.
But what if, say, a 737 pilot disconnects all the autos, rolls the plane inverted, pushes the throttles and goes into an inverted dive. Would that happen slowly enough for the rest of the crew to stop it? Since realistically I wouldn’t see the other pilot being physically able to get back into the cockpit with those forces to contend with.
Existing-Help-3187@reddit
No it doesn't. Two button presses on the overhead panel on an A320 puts all the protections off.
Super-Handle7395@reddit
I work in networking, and even though we build in all sorts of redundancy — dual supervisors, HA pairs, failover protocols, everything — it only takes one obscure bug to bring it all down. Especially the kind that only triggers under very specific conditions, like a certain uptime or timestamp.
When all devices are powered on or rebooted at the same time, their system timers are aligned down to the millisecond. If there’s a latent bug that only surfaces after, say, 497 days of uptime or at a specific tick, you’ve now got multiple devices hitting that same bug at the same time — and redundancy doesn’t help when everything fails simultaneously.
It’s a good reminder that redundancy isn’t true resilience unless failure domains are properly isolated. Even then, if every node is running the same software version with the same flaw, your backup is just as vulnerable as your primary.
That’s the part most people don’t see: in networking, it’s not if something strange will happen — it’s when. The real question is whether your monitoring, logging, and rollback plans are strong enough when the chaos finally hits.
gargeug@reddit
It certainly seems like TCMA shut the fuel down. But I have to say reading up on AFDX all of a sudden makes me also suspicious of the networking.
When they were first developing AFDX, and specifically the 787's fiber switched version. There were serious concerns about AFDX for use in flight critical sensors due to network loading on the switches. There was a paper in IEEE suggesting that a fully loaded network that experiences some transient event could force a drop of nearly 1.6% percent of packets.
Another concern with AFDX was the fiber itself. They only have like 200 mate cycles on them, and poor maintenance (not cleaning them) when unmating and re-mating can cause a higher number of failed packets in general, if not a complete loss of data through that cable.
A huge thing unknown to me is that Boeing puts ALL of the network through the same switches. Flight critical control systems sharing the lanes with in-flight entertainment systems!
Think back to a video showing a previous flight where the entertainment systems were glitching, that was quickly discarded by most as being not related.
Suppose that this glitchy entertainment system was reported, and maintenance went and pulled and replugged fibers to fix it. Perhaps some, based on the age of the aircraft, were near the end of their mating lives. Or that foreign contaminent was introduced. Now the network is degraded.
And supposed that the wheels up signal, EEC feedback data regarding thrust and/or thrust lever position happened to be one of these dropped packets as all the in-flight entertainment systems were powering on to a degraded network. Something like that could trigger TSMC to think it's last known state was wheels down and a mismatch of the engine feedback and the thrust lever control.
That would be catastrophic for Boeing, and could explain it occurring on both GE engines AND RR engines.
It could also be bad for Airbus.
I_DRINK_URINE@reddit
Engine control signals don't pass through the AFDX network. The resolvers in the thrust levers are wired directly to the FADECs. It's all analog signals.
phluidity@reddit
My only devil's advocate comment on this theory (and I acknowledge there is some degree of scary plausibility in it) is that the circumstances you describe don't seem that rare. It would be the sort of event I'd have expected to have happened many times before in the ten years of the plane. It also seems like the sort of technical issue that would have been discovered during design and worked around.
So I don't think this can be the entire cause of the crash. But it does seem plausible that this could be at least one link in the chain of cascading failure.
gargeug@reddit
You don't really start approaching the mating cycle limit unless you have been pulling and replugging them once a month for a year, for about the age of this plane. And as this plane is one of the first ever made, it could just be that most other planes in service are not approaching this limit yet. So ignoring it based on past history is not really valid if the problem only shows itself after a long time in service.
I also would have assumed Boeing would have caught the MCAS issue from the single AOA sensor failing in basic fault testing, or even just using your brain. So I don't think I would bank my argument on Boeing's SW testing prowess. They would have no reason to have gone back and dug into the 787 code the same way they were forced to with the 737 MAX.
Everyone needs a devil's advocate and I appreciate it. I just haven't heard any other explanation yet that thoroughly explains all of the symptoms we saw occur beyond bad fuel, but even that seems like it wouldn't happen at the exact same time.
phluidity@reddit
No worries. And your comment about Boeing QA is well taken. Like you say, bad fuel makes no sense, as the odds of both engines going out like that at exactly the same time are astronomical.
Super-Handle7395@reddit
Very interesting thanks for sharing I didn’t know the inners of the plane network. Makes me a tad nervous 😬 to fly now…
gargeug@reddit
I don't claim to know it either. But I do have a lot of experience with deterministic code to know where to look for odd software bugs that rarely surface. And finding published scientific articles bemoaning AFDX as a "downgrade" in terms of latency and robustness under certain extreme circumstances is concerning. Especially when you consider that clogged networks are a driver, and that the 787 was designed in the late 2000s prior to things like inflight wifi, which is likely an added load to the switches.
More concerning is network security. Boeing has outsourced nearly 70% of the items on the 787. I'd imagine a lot of that software dev went to India, and there might be a lot of people there that made that actual network security that Boeing claims is invincible. The fact that normal entertainment software rides on top of of the same switches as flight control software is concerning. Doesn't matter if it is data diode and VPN protected, if you know what is behind that diode and VPN, you don't need responses to know exactly what type of information to send. Boeing put a lot of trust in their ability to segregate their networks, but the only surefire way is to keep them physically segregated and insecure.
Super-Handle7395@reddit
If it’s running on the same switch, they’d likely need to use a VRF to achieve segmentation beyond what a local VLAN provides. VLANs offer Layer 2 separation, but if you need true isolation at Layer 3—such as separate routing tables, overlapping IP ranges, or tighter security boundaries—a VRF would be necessary. This approach allows for more granular control and ensures traffic remains logically separated even when traversing the same physical infrastructure.
Super-Handle7395@reddit
I had Wi-Fi and full internet access on my last flight for a solid 4 hours—it honestly blew me away. It’s incredible how far in-flight connectivity has come. Just a few years ago, it was either spotty or non-existent, and now you’re streaming, messaging, or working mid-air like it’s nothing
Corona_Criminal@reddit
There seems to be a fundamental problem with the whole concept of the TCAM system and its cost-benefit analysis. If it works as designed, it automatically shuts down runaway engines on the ground. However, in such a situation, pilots would be in a relatively low stress/workload mode and perfectly able to shut down engines manually, i.e., the benefit is trivial. If TCAM goes wrong for whatever reason, it could cause total power loss in flight and a crash such as this, i.e., catastrophic consequences.
So, whether TCAM caused the crash or not, this reflects abysmally on Boeing's company culture and demonstrates its inability to have learned or changed since the 737 Max disasters.
Quaternary23@reddit
Oh look it’s one of those “aIRbuS iS pErfEct aNd dOesN’T mAkE mIsTakEs aNd dOesN’T mAkE dEsIgN fLaWs” jokes. None of this reflects Boeing’s supposed inability to have changed since the 737 max 8 crashes. They HAVE changed. Typical low IQ Boeing hater.
nuke740824@reddit
I really hope this will not show to have caused this tragedy, but it is concerning to read about a system that acts like described in the sticked post above:
A logic, presumably as unknown to the pilots as the MCAS was. If this turns out to be the cause here, Boeing really will be f***ed.
SteveD88@reddit
This has to be the most likely case, but we've 15 years of 787 operation, with 1000 hulls produced. There's enough flight hours there to have uncovered any latent issues?
thatblack147@reddit
Wild speculation on my part, but my money is on the missing link between the subsystem existing and the accident occurring being something the maintenance crew have done to circumvent an issue the tcma was causing. Bit of an oversimplification, but if the conditions for tcma deployment are: wheels weighted -> thrust generated -> throttle levers in disagreement with thrust level, then a workaround that messed with the accurate reporting of one or two of those values only leaves the reporting of one or two conditions that need to malfunction before you get an incident.
SteveD88@reddit
I'm not saying its impossible, but the FMEA should be picking stuff like that up, and after the Max crisis I can imagine it was all re-visiyed for flaws.
Nice_Classroom_6459@reddit
There's plenty of precedent for this - the 737 rudder deflection issue, eg, occurred 24 years after the aircraft was introduced. Doesn't make it more likely by any means, but there's definitely precedent for design flaws not presenting for 10+ years.
BubbleNucleator@reddit
I wonder how many 'wheel weight sensors' the aircraft had. Kind of feels like the MCAS situation all over again, Boeing's have one single sensor, and Airbus has a similar system with multiple sensors for redundancy.
DanielCofour@reddit
yeah, my money is on this as well. It's pretty telling that the engines went out just as the gear retraction was started. It is entirely possible that faulty sensors triggered weight on wheels condition, possibly combined with other factors (maybe pilots accidentally moved the thrust lever just a little bit while retracting the gear? enough for the system to consider this an on-the-ground situation), and that led the system to just shut down the engines.
Objective-Muffin6842@reddit
The TCMA only will cut the engines if the throttle is at idle but the engines are not (essentially, if there is severe disagreement between commanded vs actual thurst).
gargeug@reddit
It seems this is not entirely true. It doesn't seem like a bang bang type thing. It generates thrust profiles and it it detects a thrust profile is outside of commanded, and it sees the wheels down, it can cut the fuel.
Objective-Muffin6842@reddit
If the throttles are at idle, which would only happen if the pilots pushed them back to idle for some reason.
Chen932000@reddit
Pretty sure TCMA is from GE (engine manufacturer) not Boeing.
jceverett917@reddit
Really? That ANA flight had RR engines. Boeing has the patent on it. GE is probably only responsible for integrating it into the control systems no?
Objective-Muffin6842@reddit
TCMs (Thrust Control Modules) are not unique to Boeing and I'm actually certain they're made by the engine manufacturer (GE in this case). MCAS was just a shitty system Boeing threw in last minute, it's nowhere near the same thing.
airbusrules@reddit
Reading about TCMA gave me flashbacks to the whole MCAS debacle. I do wonder what other things are deep within the software.
graphical_molerat@reddit
Yep, that subsystem is my prime suspect as well. With the technical question being "how many wonky wheels on ground sensors, and readouts of the thrust levers, do you need for this to potentially trigger at the worst possible moment while actually being airborne?".
Flux_Aeternal@reddit
I'm as far from an expert as can be but it seems insane to me that there is a subroutine that has the ability to completely shut down both engines simultaneously by itself. Seems like an obvious disaster waiting to happen.
ChillFratBro@reddit
This is an extreme misrepresentation of that system (and really how all systems work). TCMA is designed as a safety feature on the ground when thrust reversers are deployed when the consequences of allowing an engine to run away is more severe than the consequences of shutting them down.
It could be a software bug, but pointing fingers at TCMA in particular has no basis in fact. It's no more likely to be that software system than any other. Is it possible that system was accidentally triggered? Sure. Is it likely? No. If that system could fail in flight, we probably would have seen it before.
There was an ANA plane that triggered it on the ground, but the conclusion there was it acted appropriately b/c pilots deployed thrust reversers too early. This particular system (like most others on the 787) has no history of bugs.
throwaway-a0@reddit
If TCMA is responsible, it did not necessarily activate in flight. It could have activated on the ground after reaching Vr just before rotation.
ChillFratBro@reddit
The plane wouldn't have even reached 400 ft AGL if that happened. It's quite clear from the videos that loss of thrust happened in-air.
throwaway-a0@reddit
Yeah but how long from TCMA activation at takeoff thrust, to loss of thrust, and loss of hydraulic power?
(The landing gear was only partially retracted, so the loss of hydraulic power came very shortly after takeoff at the latest.)
ChillFratBro@reddit
Well less than a second to loss of thrust, bit longer (but not much) to loss of hydraulics. TCMA stops fuel at the engine, there flat out is not enough residual thrust to allow the plane to climb. Physics do not allow it. Period. Full stop.
If somehow this was TCMA, it would have had to activate 10+ seconds after the wheels left the runway. There's no data to suggest this is any more likely than any other software bug (if it even is a software bug, which I doubt - mid-lifespan crashes are almost always maintenance or operational issues).
Uninformed people are focusing on TCMA because it sounds scary and they don't understand it. There are dozens of other systems that could also cause a catastrophic loss of thrust - all very unlikely. I'm sure they'll look at TCMA and all the others in the failure investigation. I also know that anyone who is speculating about specific software packages with the information currently available is irresponsible and has no idea what they're talking about.
CollegeStation17155@reddit
According to the ADSB data, the plane was already trading speed for altitude as the wheels came off the tarmac; 186 at rotation down to 172 70 feet over threshold
ChillFratBro@reddit
We should wait for black box data before putting too much stock in numbers - ADS-B is good, but it's not as precise as the plane's own instruments. There are valid reasons for losing ground speed that may not mean a plane is losing air speed - rotation means the plane is now flying the hypotenuse of a triangle, winds gradually get stronger as altitude increases, etc. It's also hard to say based on that data where between rotation and 70 ft AGL something might have gone wrong - the plane may or may not have had the initial problem while on the ground.
It absolutely may be true that the engines were struggling earlier than obvious loss of lift, but we don't have enough data to say for sure yet. However, if that is true, it completely exonerates TCMA - cutting fuel flow cannot lead to a gradual failure.
throwaway-a0@reddit
TCMA won't lead to immediate failure either, as there is still angular momentum in the rotating parts of the engine, which will get converted to thrust at a decreasing rate. Until they drop below idle speed at which point the engines no longer produce meaningful thrust and the RAT deploys.
ChillFratBro@reddit
This shows an extreme misunderstanding of how a jet engine works with incoming airflow. The relative speed of the incoming air works in opposition to the inertia, it's not a gradual spin down if fuel is completely cut. A turbofan requires fuel to experience a gradual failure while in flight
Statically on the ground, a jet engine might spin for a bit. With 180 knot incoming air, the inertia is dissipated extremely quickly as the air works against the inertia.
throwaway-a0@reddit
That sounds quite fast.
Others estimated from the videos that at ~10 seconds after liftoff the RAT is deployed. If that is accurate, then by that time already the conditions for RAT deployment were met (e.g. engines below idle speed).
I don't think so. They just look at which theories are viable at this point and TCMA activation is among them.
jjgoawayok@reddit
From the TCMA patent: Although software package 130 is executed while the aircraft is in flight and on the ground, software package will only cut fuel to the engine if the aircraft is on the ground. Software package 130 monitors the flight status of the aircraft using system information received by EEC 18.
s_aiph@reddit
Does the patent wording imply that there is a monitoring system that actively runs **in flight ** to determine whether to activate the TCMA?
If so, I am curious:
How does the system determine whether the plane is "on the ground"? What specific inputs does the EEC use for ground/flight determination? Weight-on-wheels only, or does it cross-reference air data, gear position, altitude, etc..?
How does the software compare different sensor readings or handle disagreements? What happens if the information is corrupted through faulty hardware or wiring?
In the case of the MAX, I read that the MCAS was programmed to read from only one angle of attack sensor at a time. In both crashes, a single sensor was faulty causing the software to kick in. Obviously with 15 years of history, this aircraft is unlikely to have a software flaw so obvious, but perhaps an ultra rare edge case?
Other than the point about the GCU integer overflow bug relating to AD 2018-20-15, are there any other software systems that can cut power to the engines?
jjgoawayok@reddit
The system is active in flight but unable to cut fuel in the air. WOW signal determines the configuration. The only inputs to the software are Airplane speed, Altitude, WOW, TRA (Thrust Resolver Angle), T/R cowl position, N1 speed.
s_aiph@reddit
We've seen that the landing gear was still extended. Is it possible there was a transient strut compression during attempted retraction, or false signal from faulty WOW sensors feeding *both* ECCs, indicating the aircraft was on ground? This would presumably have to coincide with an false "idle" reading from the throttle resolvers for both engines along with correct detection of high engine power. It seems far fetched, statistically. I wonder if a common failiure mode could have been a network failure relating to a data bus, interface units, wiring, or software...that could simultaneously corrupt both sensor readings used by the TCMA software in both EECs?
airbusrules@reddit
True, it would be shocking for Boeing to have messed this up. It just shouldn’t be possible. Analysis and development should cover all kinds of cases and design robust logic. The level of detail that engineers have to go into about failure cases for all these systems and software is a lot, so it’s crazy to me that this could happen. But could really be a sequence/alignment of things that could not have been predicted.
gargeug@reddit
Look at the AFDX networking they use. Under heavy load it can drop packets. Then realize dreamliner runs flight control systems and entertainment systems through the same fiber switches. Then remember the glitchy entertainment systems video. Perhaps a tech pulled some fibers and didn't clean them properly before reinserting, or they were near the end of their mating lifetimes. These could cause a wheels up signal to be dropped, at which point TCMA could have acted as designed..
DanielCofour@reddit
the reason why I have serious doubts about this being a fuel contamination/system issue, is that. considering all the reduncies and how separated the engines and fuel systems are for the two engines, it's statistically borderline impossible for a simultaneous failure. Don't get me wrong, it's perfectly possible for both of them to fail within a \~5 minute window, as was the case with Cathay 780, but at the same time? No, that is just not happening from a fuel contamination. And they wouldn't fail in the same way either, we'd have reports of compressor stalls/sputtering/backfiring/literal flames... something.
Simultaneous failure of both engines can only be due to electrical or software error. I think it's telling that the engines went out when the gear retraction was started. Something in that procedure, probably combined with a host of other factors, triggered a fault in either the electrical system or a software error and caused both engines to shut down. And by shut down, I do mean shut down: again, there was no evidence of engine failure from any kind of mechanical/fuel issues, those would cause issues which would be visible on the recordings and/or felt by the lone survivor of the crash. These engines just rolled back normally.
airbusrules@reddit
I’d say a software issue should also be similarly statistically impossible. Unless Boeing or its suppliers have really screwed up something. The level of rigour in development would be very high for something like this, that can cause total loss of thrust. And past experience shows that engine control technology is very mature. But again can’t fully trust the development given MCAS. It’s also surprising if this hasn’t shown up after nearly 1200 aircraft in service, starting more than a decade ago.
DanielCofour@reddit
I don't mean that a simple software bug caused this, which is why I specified a host of other factors. It is entirely probable that a failure in the weight of wheels sensors, combined with other lingering issues with the aircraft that weren't noticed so far, put this plane into a unique state where the onboard computers all determined that the plane is on the ground and at take-off thrust, so they simply turned off the engines (this is simplifying of course, the final report will probably show a series of much more complex issues resulting in the crash).
I am a software developer and I can confidently tell you that it is humanly impossible, no matter the level of rigour, to take into account all possible scenarios that a system as complex as a Boeing 787 can be in. You have 1000s of parameters and sensors that you need to keep track off, any one of which can fail.
Granted, this is all speculation, but to me it is very telling that the sequence of events started with the gear retraction, it had power until then and successfully took off. And the shutoff was simultaneous with no visible damage to the engines, so it can only be electrical/software.
LantaExile@reddit
There is some info on the TCMA - Thrust Control Malfunction Accommodation system that shut down both engines on a 787 in 2019
https://www.pprune.org/rumours-news/617426-ana-787-engines-shutdown-during-landing.html#post10366128
It's designed to trigger if an engine is at high thrust while the throttle is in the idle position and the plane is on the ground. Maybe there was a low probability combination of sensor failures which could explain why it only happened after much successful flying and maybe why it was when they raised the gear if that effected the on the ground sensor?
ThorsteinKlingenberg@reddit
Are the sensors redundant? As in, one sensor on each main gear feeding each FADEC with a separate signal? Or is there a single wheels loaded sensor on one set of gears and one sensor on the throttles, feeding both FADECS?
If so were back to single point of failure, just like the AOA vane and MCAS..
LantaExile@reddit
Personally I have no idea but maybe someone knows how the system works?
RandomObserver13@reddit
The SmartLynx A320 training crash is a good example of this. An almost impossible to predict scenario. Also a nice example of how pilots can sometimes pull off a miracle.
bonzoboy2000@reddit
Maintenance issue: Is it possible they failed to fully fuel the aircraft?
ECrispy@reddit
787 has TCMA which can and has shut off power to both engines instantly. Its happened before to ANA flight on landing. If there are faulty landing gear sensors etc, its very likley TCMA shut off both engines just before or after rotate and there is nothing pilots can do - this is by far the most likely and feasible cause and there is a known path in the system for this to happen.
airbusrules@reddit
2 of the conditions for TCMA is being on ground and thrust lever at idle. Would be crazy if both conditions were met in flight. The ANA failure was hazardous but at least the aircraft was on ground and actually the engines were at idle. Linking TCMA to AI171 is difficult unless it’s a horribly designed system.
LantaExile@reddit
There was a dual engine shutdown on ANA Flight NH-985, another 787 January 17, 2019, activated by a system called the TCMA (Thrust Control Malfunction Accommodation), intended to shutdown runaway engines on the ground. Its logic should only activate it on the ground with weight on wheels if it senses the thrust lever is at idle but the engine is not (from https://www.reddit.com/r/aviation/comments/1ld9yb8/air_india_flight_171_crash_megathread_3/)
Heiter-Sama@reddit
The fact that this has happened before on the same airplane, just during landing instead of takeoff, makes it the most likely (of still many other scenarios) ATM.
If there is somehow an error on what state the airplane and landing gear are in, this could cause it to shut down both engines instantly no?
hunglowcharlie@reddit
I don't think this would be the case since the throttles would also have to be at idle for the conditions to be met. So even if the WOW switches were giving faulty output, the thrust levers would have to be at idle.
David905@reddit
Why would the thrust levels have to be at idle? The software would simply have to 'think' they were at idle, whether due to faulty input (sensor failure), faulty wiring (water damage for example), or, most likely of all IMO, a bug in the software. The whole problem is that things didn't work as planned. 'That cannot happen' doesn't really apply at this point..
Heiter-Sama@reddit
Yes this also needs some sort of mismatch or error on the throttle/thrust, as well as on the landing gear.
But since the double engine failure coincides with the landing gear retraction, it isn't all that unlikely compared to other scenarios.
Either way this will be easy to prove/disprove with the flight data soon.
hunglowcharlie@reddit
Why would the trust levers be at idle? Its highly unlikely.
Casukarut@reddit
On this specific airplane or on the 787 line?
Heiter-Sama@reddit
The 787 line in 2019:
https://simpleflying.com/ana-dual-engine-failure-on-landing/
airbusrules@reddit
Yea it is possible but should never happen if properly designed. TCMA is restricted to ground so there should be numerous safeguards against activation in flight as it does something extreme (shutting down the engines which would be catastrophic or hazardous at best depending on altitude). It would be crazy for Boeing to have messed that up. That is very basic design logic that is critical to get right.
Heiter-Sama@reddit
Honestly I have no idea what checks the TCMA does to read a ground state. But the engine failure seems to coincide at least with the starting of landing gear retraction.
Ricky_Ventura@reddit
Fuel contamination is the least likely scenario above. Only one plane was affected and immediately. Additionally each filter contains a bypass.
stemmisc@reddit
I assume the answer is "yes", but I guess I'll ask in the off chance:
Is there a filter that would filter out physical debris at the hookup point when the fuel is being loaded into the plane? And if so, how big are the holes in the filter?
Just to be clear, I'm not asking about the fuel filters in the plane itself that filter the fuel going from the airplane's tanks to the airplane's engines. Rather, I'm asking about filters at the loading point when they put the fuel from the ground into the plane (i.e. basically asking if there's some way a bunch of small-ish debris could've gotten loaded into the plane's fuel tanks from it getting into the fuel when it was still in the ground tanks, and then clogged all of the plane's fuel filters a few minutes into things)?
trader45nj@reddit
Regarding a maintenance error affecting both engines, there was an incident decades ago where an airliner had 3 engines fail or partially fail because of a maintenance error. It was a flight from Miami to the Caribbean. After departing, the flight lost oil pressure in one engine, they shut it down and turned around to return. While returning the other two engines had the same thing happen, those they ran until they failed. At which point they restarted the first engine and made it to a safe landing. The problem? The oil had been changed on all 3 engines and the seals on the plugs had been left off all of them. So, it's rare, but possible.
RealPutin@reddit
The thing that you mention that's typical of most engine failure scenarios is one giving out before the other.
airbusrules@reddit
Ah interesting. Which flight was that? Haven’t heard of this one.
trader45nj@reddit
https://en.m.wikipedia.org/wiki/Eastern_Air_Lines_Flight_855#:~:text=On%20May%205%2C%201983%2C%20a,three%20engines%20near%20Miami%2C%20Florida.
Eastern Air Lines, L1011
airbusrules@reddit
Thanks :)
Ricky_Ventura@reddit
I've heard this talked about in maintenance circles for years -- the issue that when a procedure comes due, techs will do every instance of that procedure at once. -- for example fuel filters come due techs will do all filters on each engine at once meaning if they leave a junior tech and lie for the qa signature/inspection it's a possibility every one will be done incorrectly.
The issue is enforcement especially internationally would be impossible.
Lost-Inevitable42@reddit
> Software bug (engine control) >> Very unlikely given this is a critical function.
It's an unexpected crash. I'm not sure any issue or more unlikely than another.
This actually seems like the most likely cause to me. Software + issues related to heat + issues related to electrical systems.
CollegeStation17155@reddit
The EASA directive to inspect the seals between the potable water supply and electronic bay does suggest a remote possibility that water leaked into the bay through a bad seal sloshed into the engine controls and shut them down at around rotation.
ke1c4m@reddit
What kind of “maintenance error” would even be possible, considering that the plane only had about a three-hour layover after the flight from Delhi?
https://www.flightradar24.com/data/aircraft/vt-anb
Spa_5_Fitness_Camp@reddit
The fact that the lone survivor hasn't been sequestered from everyone except doctors and investigators is a disgrace. Anything except his initial accounts is now compromised. Add to that the delays in restricting access to the crash site and this is a really bad look for the agency in charge.
xorbe@reddit
Human memory is terribly unreliable during extreme events anyways. Just wait for the report about the various recording devices.
SliceMountain6983@reddit
Step 1 of 787 gear retraction is the main gear doors swing down. They were clearly not down in the rooftop video.
Gear retraction definitely, beyond a doubt, had not begun.
aebulbul@reddit
Isnt jt possible this was something completely different and everyone is focused on the wrong thing?
Engines lose power Pilot or first officer cuts fuel line to restart it Other pilot asks him why Pilot responds he didn’t but doesn’t elaborate
NASBIT_@reddit
I have a question:
I understand there is a locking mechanism on those field cutoff switches, how leverage is the locking mechanism reset every time it's moved or idle for a certain period of time? Meaning is there a possibility that the switches were lifted but still in "Run" position prior to takeoff (due to checklist, pilot might have lifted it twoce but kept it in Run)? If so then that makes the accidental theory of brushing against the switches in midair much more possible
Fogflyr@reddit
No, you can not accidentally ‘brush’ the switches into cut-off. You have to physically pull the switch (it is a handle actually) toward you and then move it up into the cut-off position. There is also a spring on each switch that pulls it into ‘Run’, so even you didn’t fully get in into place or the locking mechanism was broken, the spring would pull it into the Run position.
NASBIT_@reddit
Understood thank you
Admirable-Marsupial6@reddit
Hi.. just saw Captain Steve’s reading of the preliminary report. Was wondering what is everyone’s opinion on that.
I have no background or prior interest in aviation. I’m just horrified Indian frequent flier. Been haunting this sub since the accident and I remember reading some experts here stating that captain Steve is not reliable.
Personally I found his video credible but then again, I wouldn’t know.
Fogflyr@reddit
I am a commercial pilot, but I don’t fly the big iron, so take may opinion as you see fit. IMO, there is no longer any doubt this was intentionally done by one of the pilots. I haven’t seen the video yet, but I read the report. These switches are gated and cannot be turned off by accident. They were switched off one second apart, which is exactly how they are normally turned off. The sad truth is one of the pilot’s did this intentionally.
Admirable-Marsupial6@reddit
Yes, even I’m heart breakingly coming to the same conclusion basis the information released. It’s so sad for the family of the pilot (whichever of the 2 it ultimately turns out to be), to lose your loved one and also have to deal with the public outrage
Delicious_Novel_4400@reddit
Wow, I'm feeling a lot of sadness reading that one possibility of why the fuel switches were turned off is because of pilot suicide. That would really be just awful, and I don't want to say anything but no good words would come out if that ends up being true.
I did read on WSJ that "Pilots use the switches to start the jet’s engines, shut them down, or reset them in certain emergencies." Could it also be that in the moment, say the engines filed for some other reason, the pilots maybe tried to switch the engines off and on in the few seconds they knew they were going down to try to reset them, as the WSJ said they can be used for that....? Perhaps in the panic of the moment they tried to do this and in the end with no time it ended on the off position...?
I really hope it wasn't on purpose that would just be completely awful.
Lucky_Reaction_7086@reddit
Check this out. Captain Steve's video that explains in detail. https://youtu.be/MD64uYK926o?si=IZrM6O22pp8e6IUa
hiteshchopra2511@reddit
https://www.ndtv.com/india-news/air-india-crash-preliminary-report-submitted-to-aviation-ministry-8841505
Prior-Flamingo-1378@reddit
They seem to mention the position of the fuel switches a lot. Could they have found them in the off position in the wreckage?
PengPenguin888@reddit
The FDR would have recorded this as well.
Low-Computer8293@reddit
I have been wondering for some time, if both fuel cutoff switches were set to off shortly after V1, would that explain everything?
Prior-Flamingo-1378@reddit
Well shit.
https://theaircurrent.com/aviation-safety/ai171-investigation-fuel-control-switches/
WorthDues@reddit
"...details surrounding movement of the fuel of the fuel control switches will take months - if not longer". Great...
Prior-Flamingo-1378@reddit
No I think the interim report will say “the fuel switches where found in the off position.” And something along the lines “no evidence of third party presence in the cockpit” or something like that.
The details they talk about is figuring out the reasons one of the pilots did it, that’s a full criminal investigation with psychologists, forensic people, warrants etc.
AndrewHurst1112@reddit
what do people think about this talk of focus being on fuel switches? I suppose we will find out more when report released on 11th, but I'm seeing many stories mentioning this. Ofc unverifiable at this stage
allielhoop@reddit
Seems like possible curveball suggesting possible pilot problem...
Brief-Visit-8857@reddit
Found a comment on YouTube, could be possible, take it with a grain of salt:
Elyucateco_salsamaya@reddit
this guy was probably correct with the reports today of authorities looking at positions of fuel switches. We don't know where they're looking. Whether inside the cockpit. Or physical valves/switches at the engines themselves.
electrical malfunction > reset the FSOV > dual engine failure
sizziano@reddit
This is mostly BS from everything I've read about people who actually know the systems. Also referring to any hydraulic system on a Boeing by color is a red flag. This ain't an Airbus.
Brief-Visit-8857@reddit
Found this comment in the AvHearld website from the VS105 flight, seems to match the survivor’s account:
Link: https://avherald.com/h?article=5143b671
blackhawk201@reddit
You guys are geniuses
imnicexDDD@reddit
Can you link the comment
Brief-Visit-8857@reddit
Here ya go: https://youtube.com/watch?v=p07X3YR5q_s&lc=Ugwqsth1fIsVNS1Ollx4AaABAg&si=fA8kcuDyoVu_KqCI
imnicexDDD@reddit
thank you
artmorte@reddit
Doesn't make any sense to a layman like me that an electrical failure would automatically cut off fuel to the engines.
"Oh, the plane lost electrical power, well, that means there MUST be a fire, let's cut off fuel supply to all engines, even if the plane is airborne."
Why would anyone program their aircraft's software to operate like that??? I find this hard to believe.
NigroqueSimillima@reddit
It doesn't make sense because it's not true. The spar- and engine-shut-off valves are motor-operated valves (MOVs). They stay wherever they were last driven; power is required to move them in either direction.
Brief-Visit-8857@reddit
It’s Boeing we’re talking about. They programmed the MCAS to rely on ONE AoA sensor instead of 2 for redundancy.
Kobe_Wan_Ginobili@reddit
To me that wasn't even the biggest issue, it was not having any quality control on the data that sensor sent out.
The AoA sensor whilst malfunctioning was sending out absolute nonsense data claiming the AoA had changed something like 20 degrees in a few milliseconds, if that were true the whole airframe would have been torn apart and yet that data was still allowed to activate MCAS! So easy to have a few lines of code which would have discarded that nonsense data or to have some kind of kalman filter to utilizing other sensors for a better estimate
railker@reddit
Well and was it the first or second one, was a faulty sensor that made it out of the overhaul shop with certification and then onto the aircraft -- but evidently never had a function check done which is wild to me. If the manual didn't call for it then that's one thing, I'd personally do it anyways, but if it did and maintenance skipped it. Oof.
ghoonrhed@reddit
What about the training? Telling the pilots about this new system that could override their controls also would've helped.
Brief-Visit-8857@reddit
They hid it from the pilots.
Tslover1389@reddit
TCMA also has the authority to simultaneously shutoff fuel to both engines.
jofrevic@reddit
With a grain of salt, I believe this is it. I cannot find anything to contest it. The electrical actuation of the gear seems to be the cause of the major electrical failure. Question is why the RAT restoring 28V did not re-engaged the valve? The explanation could be this FSOV failed itself. Lets see, if so expect a retrofit for a manual bypassing valve for emergencies with a dedicated display or warning lamp in the cockpit. An spring loaded valve is like holding a grenade without pin in your hand.
stuntin102@reddit
on some of the 787-8, the doors open after the truck tilt. on other models it happens simultaneously and sometimes a little after. looking at youtube 787-8,9,10 takeoffs
Brief-Visit-8857@reddit
There’s actually a few milliseconds of difference… but they got the steps switched. The gear actually tilts first and then the door opens. Something catastrophic happened right after the gear was selected up.
js5180@reddit
Based on this video, tilting the wheels forward starts simultaneously with the doors opening, and finishes sooner. Not as described above. Nevertheless, the events seem to be consistent with the failure happening right as the gear-up call was made.
https://m.youtube.com/watch?v=2ZwzACp-q9U&pp=0gcJCfwAo7VqN5tD
Brief-Visit-8857@reddit
There’s actually a few milliseconds of difference… but they got the steps switched. The gear actually tilts first and then the door opens. But I agree with you, something catastrophic happened right after the gear was selected up.
fegelman@reddit
Do the GCUs shutting down lead to the engines shutting down as well?
Brief-Visit-8857@reddit
Nope, they’re not supposed to. The fuel valves run off of DC power, not AC power. This is why whatever caused this was very likely a cascading electrical failure
TOAO_Cyrus@reddit
A lot of words but the premise that the fuel shut off valves will just automatically close on a power failure makes no sense and doesn't jive with other stuff I have read. I have seen info about a system that will shut down or reduce thrust when the plane is on the ground and a discrepancy between power and throttle position is detected. The theory is a combination of electrical issues, bad timing and maybe software issues could trigger that just as the plane took off.
Brief-Visit-8857@reddit
Unfortunately, that’s how Boeing designed it. I get what you’re saying, but the thing with the 787 is that the fuel shutoff valves (FSOVs) are spring-loaded—they stay open only if they get power. If power is lost, they automatically close to prevent feeding fuel in a fire, which is part of Boeing’s safety logic.
The earlier electrical failures didn’t shut down engines because they happened at cruise, where power systems are more stable. AI171 was just lifting off, and if there was a major electrical glitch right as systems were switching loads (like gear retraction), it could’ve knocked out FSOV power.
railker@reddit
Alternatively, PPRuNe pilot indicates that they're power required both ways for opening and closing. Lacking the 787 AMM I can't absolutely verify, but every aircraft I've touched works that way. There ARE solenoid valves that do exist that failsafe open or closed, I've mostly seen them in bleed air systems.
IMO a system that just 'woops, I shut off your engines good luck' if power blips or a DC bus wants to load shed seems a stretch. Otherwise a convincing, plausible theory, barring their reference to the 248-day reboot AD as if operators are still doing that. Or anyone was ever leaving their 787 turned on for 8 months.
Brief-Visit-8857@reddit
It’s possible, the chances of that happening were probably very very low, and this could be a one off case. So it’s definitely a far stretch, but could be plausible by all means
railker@reddit
💯 In the words of Sully that I still can't absolutely ascertain if it's just from the movie or an actual quote from him, "Everything is unprecedented until it happens for the first time."
TOAO_Cyrus@reddit
I cant find anything online saying the fuel shutoff vales would automatically close when losing power.
Brief-Visit-8857@reddit
https://www.reddit.com/r/aviation/s/WE8JTIvHP5
lukekay7@reddit
Does the slow release of detail in the investigation give a clue in and of itself? I.e. no grounding of the aircraft and clearly no ‘rush’ to provide answers to the public.
DaBingeGirl@reddit
I tend to think the way they've slow-walked the investigation suggests they think it could be an isolated incident. Right after the crash, the DGCA conducted a review of airports and airlines, the details are sketchy but they found:
That investigation and the vague findings are red flags for me.
What's of interest to me is that there do not seem to be any reports of similar issues occurring on other airlines. With MCAS, the problem was pretty well known on English-speaking pilot forums, but no one seems to have an explanation for what happened in this case. If it was a software issue or something else Boeing/GE related, I think we'd see discussions about it and more pressure on India to release the black box data. Hopefully we'll know more next week, but my gut feeling is this is likely an Air India issue, not a 787 problem.
I find it extremely disturbing how this story just got swept under the carpet. While I don't think it's a major cause for concern, the first hull loss with seemingly no explanation is a huge fucking deal. The boxes should've been prioritized, as they are in every other investigation. There are too many 787s flying around for India to drag their feet like this.
drewsed@reddit
There’s nothing new to report until the prelim report comes out. What else are you hoping they’ll publish/keep it in the spotlight with? I can near guarantee that those with a vested interest/liabilities have not forgotten about it.
thefreeman06@reddit
Trust me if grounding was required it would have been done, this is something not taken lightly as the risk is far too great. The backlash - politically and in civil terms - and further repurcussions of it all, the DGCA would just ground them all.
Mrpoopybutwhole2@reddit
Well they didn't ground the 737 max after the first mcas accident... and then another accident happened due to the same issue
Brief-Visit-8857@reddit
Or… they don’t know what caused the crash.
MortimerDongle@reddit
I don't think it tells us much. Hopefully, if they had reason to think 787s should be grounded they would say so. But the relative silence could equally mean they don't know anything yet.
It isn't China, so we shouldn't assume (yet) they're hiding important information.
Tough-Candy-9455@reddit
https://www.ndtv.com/india-news/air-india-crash-simulation-pilots-recreated-ai-171s-final-moments-on-simulator-what-they-found-8812035
This article is a few days old, I had ignored it as I thought it was just the same Bloomberg article but it has quite a few additional details.
So this is about simulations conducted by three company instructor pilots in Air India 787 sims. It's not part of the AAIB probe, and it doesn't seem to be officially sanctioned by AI either, but what is interesting is that they did have access to the original load sheet of AI171.
The Bloomberg article said they were trying flap up TOs, this one goes more detailed: they tried single engine TO with flaps up and undercarriage deployed, and it still managed to gain altitude. They were also attempting to replicated unspecified electrical failures causing dual engine failure but were unable to.
So yeah, nothing new or important, but interesting nevertheless.
Prior-Flamingo-1378@reddit
I honestly don’t understand how we have no idea what happened to a plane that was recorded from 3 different angles and with both black boxes recovered since day 2 AND a survivor.
It feels like a cover up
Lazy_Ebb_2922@reddit
The NTSB and British investigators, +Boeing, +GE s are a part of the accident investigation team, which is (understandably) led by Indian authorities. They are not likely to participate in a cover up. I'm not a pilot, but do have experience with software testing. If there's a bug buried deep in the SW, it can be very difficult to find it, especially if the code is written by multiple suppliers and then interfaced in the overall system. It could take more than the stipulated 30 days for the preliminary report.
Tough-Candy-9455@reddit
I don’t know if you have followed aviation accidents much, but they take a long time to decode and get to the bottom. The final report generally takes at least a year, usually more.
Even for causes that are obvious, there is a lot to unpack, and I would be actually more suspicious if they had released a blanket cause already. For example, in the 2020 Air India Kerala crash the day after the crash the minister was saying pilot error. While the final report found that Air India was overworking the pilots, poor training, airport not following guidelines, wrong weather data etc in addition to pilot error.
In this case, it seems to be a dual engine failure from available video evidence, with no obvious external cause. What caused it? Maybe the FDR revealed something, but there have been complex cases where there was nothing on the black boxes either, like TWA800. That took four years for the final report to be published.
Prior-Flamingo-1378@reddit
Yes I know. I actually remember twa800 when it happened. And and by week three we had some news unlike this completely silence. And the thing blew up in the middle of nowhere.
Although the news we had was that it was a SAM haha. Ok ok I know what you mean but it still feels kind of weird doesn’t it? It’s probably a completely freakish accident that’s why.
Delicious_Novel_4400@reddit
I haven't checked back on this in a few days...but did any other videos of the crash from people in the city ever surface? Do we only just have that CCTV video and the other video of the crash from that guy in the city? surprised we don't have any more. In the Brazil crash within a year ago there were so many more by bystanders.
fugutoxin@reddit
Apparently plane-spotting and filming in India falls into a legal grey area. It’s not strictly illegal but filming aircraft in the open is likely to arouse the interest of the police. The police supposedly interrogated the individual who filmed the aircraft’s descent with his phone. It is illegal to listen to, record, or broadcast any ATC communications in India. Given this level of strictness, it’s possible some eyewitnesses with video evidence might be reluctant to come forward. The Indian authorities could allay peoples’ concerns by making a public plea for any and all such video material and communicate that there will be no legal repercussions.
DaBingeGirl@reddit
I had no idea India was that restrictive.
thefreeman06@reddit
Considering the demographic here + the security angle, its not restrictive rather essential. There was a time when we could park our cars on approachways to the airport and under the takeoff path on the roads and have picnics. I have fond childhood memories of sitting on the top of my car munching away and watching those giant machines land and takeoff. Every friday night! It was normal with planes circling back and being a few meters away from you. Imagine what that was to a 5 year old ... sadly cannot be done anymore.
fugutoxin@reddit
Dude, if only that was possible in the US, albeit with a much higher altitude for safety reasons…
Brief-Visit-8857@reddit
Can’t blame em, they’re surrounded by neighbors that want to destroy them lol.
GeopoliticsIndia@reddit
I mean this is objectively true and a big reason for India's paranoia. Unsure why this is downvoted. India for most part doesn't joke around with aviation security, except the inexplicable decision to have slums around Mumbai airport
thefreeman06@reddit
Yep, slums around the airport is and has been a BIG issue for years, one that was immensely tough to solve.
Keyword: was
If all moves on schedule, I would say 5 years to transform the entire land parcel of Asia's biggest slum.
How and why? Too valuable land, simply motivated and moved it all ahead.
Imagine a full clean slate, global minds and tech of 2025, entire space reimagined.
I am not affiliated to all of this in anyway btw, just a local excited by the potential of it all.
GroceryOk4471@reddit
India is arguably a shithole
fysiX_cs@reddit
If you compare to the Jeju crash: first we had just a couple of videos and no others surfaced. Then with the report we had a video collage of several cctv cameras filming almost the whole thing from bird strike to crash. There could still be more video evidence that just hasn't been made available to the public.
particle_hombre@reddit
I'm not sure if this has been asked already, but hypothetically if there had been no buildings where the plane crashed and instead just a flat, untreed field or even some flat pavement, could the pilots have landed the plane relatively safely as basically an unpowered glider? Or was it descending too fast for that?
LuminousSnow@reddit
Still would have been very very risky as the plane is fully fueled up and would be too heavy to land normally. High chances the landing gear collapses and the plane starts breaking up/cartwheeling or something. That's why planes always try to dump fuel first before attempting a landing where possible.
LuminousSnow@reddit
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LuminousSnow@reddit
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deleted_by_reddit@reddit
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lmfaonoobs@reddit
Are fully loaded down planes generally incapable of landing? Or just safe crash landings?
LuminousSnow@reddit
It's definitely not impossible but the risk is alot greater. Landing gear or other structural components breaking up is one factor and another thing is that the resultant explosion (if there is) will be alot more devastating which drastically reduces chances of survival. So dump fuel whenever you can for sure.
railker@reddit
It can be done, but the pilots would need to do a risk-benefit decision on landing and risking significant damage or waiting, and the aircraft would immediately be subject to grounding pending an overweight landing inspection. The structural components that take the loads of a landing aren't meant to take that, which is why aircraft with a significantly higher Max Takeoff Weight over a Max Landing Weight have fuel dumping capabilities. Smaller aircraft like the 737 can also exceed MLW on takeoff but not by so much you can't just burn it off, or if it's really critical, go in and land anyways.
Kobe_Wan_Ginobili@reddit
The vertical descent rate wasn't too extreme as evidenced by the guy who survived so yeah if it was a huge stretch of pavement they would have landed with no deaths imo, maybe a few injuries from harder than normal impact but they would be coming in heavy without reverse thrust and need a very long distance to stop
A huge ideal grass field is a bit more speculative and could go wrong but Its still possible for a safe outcome
Blythyvxr@reddit
If there was a flat surface in front of them, the pilots would have been able to land - field / pavement / water, any would have been fine.
Stopping however, would have been a challenge - they’re full of fuel and they have no reversers. It would take maybe 1-3 km to stop
thepriceisright__@reddit
Even if they weren’t over max landing weight, anything over than smooth, flat pavement sufficient to bear the weight of the main gears would have probably still been a hull loss, right? As soon as a wing is ruptured that fuel is going to aerosolize and find a spark.
And has there been any further discussion on the state of the landing gear? There was some speculation that the nose gear wasn’t in the down and locked position as it flew by the apartment building.
Blythyvxr@reddit
Well fine is relative. BA038 had a hard landing at landing weight, gear struts punctured the wings.
It’s entirely theoretical, but say if the incident had happened at the Edward’s lake bed, it’d probably be OK, provided a good enough flare. Over open fields, maybe some concern, but a lot better than what happened.
thepriceisright__@reddit
Yeah I agree that just about anything is better than flying into the side of a building.
srivayush@reddit
‘Boeing 787 software glitch led to AI plane crash’, claims US aviation attorney
nouuseurname@reddit
Good article, thank you for sharing. I worked on the software on this airplane. I dont disagree that this could have caused the issue. The only other thing I can conceive is a complete failure of the p100, 200 panels. But the likelihood of that happening simultaneously is pretty slim.
Chen932000@reddit
Similar articles were released about a week ago and theres really no info in them. It’s pure speculation.
Low-Computer8293@reddit
This was a new and interesting article about the crash. It was an interview with Minister of State (MoS) For Civil Aviation. The Minister said that all options, including sabotage, are being explored as causes for the crash, that the black boxes would say in India, and the report would be available within 3 months. Not much news, expect that nothing is known at this time and the report will be out in 3 months.
https://www.ndtv.com/india-news/sabotage-angle-also-being-probed-in-air-india-ahmedabad-london-plane-crash-case-union-minister-murlidhar-mohol-8788920
thefreeman06@reddit
Must say this is a very good unbiased factual article
Low-Computer8293@reddit
I personally liked the concluding paragraph of the article where it talks about how the Minister is going to reduce cost of water and food in airports. While I'm sure that is part of his job, it doesn't make sense to me to juxtapose that alongside an interview discussing an airplane crash that killed 260 people.
rebuil86@reddit
I can hear both engines running quite loudly in the video. why is everyone saying the fuel was cut off. Its quite frustrating to sit here knowing exactly waht happened, just by simply looking at previous failures of this model, and then investigating how that could lead to what happened last week. There was no engine failure.
There was a 28V DCC Bus failure, possibel in combination with a dead backup bus which is why the pilots were constantly swapping between things on the gorudn leading to no aircon and systems not wokring.
DERRRR. Get it together.
The CCS turned off and only started to reboot when the RAT had started supplying power. thats not instant. the wrost time for it to happen is on takeoff. the FADECS default not to CLIMB power, that would be stupid because aat cruise, if you got stuck wtith full power oyoud struggle to descend. Just really bad timing for a bad design.
rebuil86@reddit
bringing this back because i hve a better explanation for it now, still revolving around the lithium battery,
Ok, Facts
1. Then engines continued to make sound all through the crash video, along with the RAT. It sounded like anormal RAT down approach and landing just with a bang at the end.
2. The transponder stopped responding at the runway threshold. Indicating loss of 28V DC power to it.
3. Boeing had allready had lithium cobalt oxide battery failures, and instad of fixing the failure, they put it in a big box and said FIXED. That box makes regular inspections very annoying.
4. The FADECs contain the EECs, which take throttle input and verify it against flight information from the common core system , which is somewhat redundant, 2 cabinets left and right. However both are primarily backed up busses connected to just one freaking battery! Yes one. Dont argue, check out the schematics.
5. If the 28V supply feeding the CCS racks fails, you get:
If multiple critical inputs are missing, or the CCS link is entirely lost, hard alternate mode may be triggered.
Ram air turbine did work, providing enough AC power to be rectified to DC immedaitaely to power the radio for the captain or first office to make mayday call. Transponder is not one of those equipments listed to be powered by RAT only in flight.
I dont really care much for the downvotes, im sitting here every night emialing all the relevant authorities trying to prevent future loss of life. This battery chemistry has no place in aviation
Some1-Somewhere@reddit
The FADECs default to last set power if the thrust lever angle resolvers fail, but they have their own FADEC alternator and can read thrust lever position with no aircraft power at all.
There are four 28VDC buses on the 787, plus the four dedicated flight control buses. The aircon compressors aren't on any of those buses including the backup bus because aircon isn't critical.
rebuilder1986@reddit
Nope. The fadecs dont do that, (rever to last throttle setting) the CCS does. The CCS going offline, as it did, causes the FADECS to go to about 38% N1. Once again, its frustrating to know what happened and watch the internet speculate. It doesnt matter how many busses there are. Theres 2 batteries, and at any point in time, only one of them is powering the CCS. It takes time (a system reset) for it to switch to the backup. This bit ia stupid. But do we know if the backup rear battery was actually working???? Or could that be the reason for the videos of the malfunctioning electronics in the previous flight? Dudes switching stuff around to get enough working to get off the ground without spending any more rupees on those pesky lithium cobalt batteries. Which brings me to my next point. These businessmen at boeing are the only fools to have found themselves stuck in a certification rutt, stuck, selling the world least reliable, most dangerous, battery chemistry as the backbone of their aircrafts computers.
It funny, they even have a presentation out there, where theyve forgotten theyre talking about airplanes, entitled, lithium battery events, a guide for firefighters.
Nothing happened in 2013 to improve the reliability of the lithium batteries. They just installed a thing to make the gas go out of the plane.
Some1-Somewhere@reddit
I see nothing suggesting that the APU battery can run CCS at all.
rebuilder1986@reddit
Of course it can. Find the schematics. It just doesnt do it simultaneously, it needs to switch over. All it takes us a microsecond of no power and the brain turns off. Its stupid. Just as stupid as the multitude of people on this forum that downvote the first person that comes along and tells everyone what happened. But this isnt a surprise. Its exactly why our stupid species ended is in this mess. Theres not enough grey matter left.
Some1-Somewhere@reddit
It seems like a pretty big design hole to exist given the effort that is gone to to make flight control work with no aircraft power, and that could be fixed with four sets of direct wiring present on every other aircraft.
rebuilder1986@reddit
In fact, u know what fk it My family is worried about my safety, and thats why i havent gone and put my face out there and made a stupid video , because my case is so compelling, the fleet would be grounded immediately and it would be my fault. The current communications are between myself and Boeing, through their ethics team, and between myself and the FAA, to make sure they dont let this continue and cause more loss of life. The batteries are getting old, and the place with the hottest harshest conditions was always going to be the place to suffer the first fkn crash. Ive had enough of talking to chimps. Im here because its not safe to go live. Take it or leave it
Mr_Tiggywinkle@reddit
This is the exact wrong attitude to have when it comes to investigations. There are probabilities, and thats fine to state your view, but "knowing exactly what happened"? Mate.
rebuilder1986@reddit
Except when uve managed to completely confirm it. Why is it wrong to work it out? U dont even know what i know because i havent revealed it
Mr_Tiggywinkle@reddit
Why are you on a different account?
rebuilder1986@reddit
Sorry. On my phone.
js5180@reddit
Can you confidently state what power level the engines would have to be at to cease to support level flight? Would cruise power be insufficient for level flight?
Because you’re saying the engines worked but the obvious evidence from the video is that they weren’t producing enough thrust to prevent the descent we saw. So what level would that be?
PrincessJadey@reddit
And when the investigation report is released, you'll be here telling that you know exactly why the report is wrong and why the black box fed the investigators wrong data?
Mpmqbi@reddit
The sound you hear in the video is generally thought to come from the ram air turbine (RAT). The fact that you don't even seem to be aware of the possibility, despite it being discussed extensively in this subreddit and in many other places, is pretty amazing.
Great_Cellist8125@reddit
How true is this?
Seat Rollback Caused Crash
Tough-Candy-9455@reddit
It's AI slop, several versions of this has been debunked on this thread and by aviation media. Telltale sign is that apparently AAIB, which downloaded the data 2 days back already has a report.
But there have been at least two incidents which involved seat failure causing incidents (not crashes). One of them involved a 787, and the other one involving an Air India flight, that presumably where chatgpt got it's cues from.
Nyungwe23@reddit
Although we still have nothing definitive on the crash cause and the summary at the start of this thread is detailed I thought this article in today’s NYT summarizes well the current status of what we know.
https://www.nytimes.com/interactive/2025/06/27/world/asia/air-india-crash-cause.html?unlocked_article_code=1.SU8.NuVj.2bkjCA0qRHEz&smid=nytcore-ios-share&referringSource=articleShare
Medical_Cherry9298@reddit
Statistical analysis is extremely accurate in resolving real world problems yet I have not seen it being applied here. What is required is careful observations of all videos and adding probabilities to actuality of events observed. Next based on events observed, what are the possible failure modes with the probabilities. This will result in an answer to the most likely cause.
The statement that a disaster is due to a string of failures will always make such analysis impossible and therefore of no value for this purpose. Critical failure modes need to be identified, i.e. that which will create a disaster considering normal performance of systems and a reasonable response of a trained pilot. For example, the Sully incident is a disaster. The extraordinary vision and action of a pilot above expectations cannot be considered as part of a string of anything. The critical failure was bird strike, dual engine failure and we are all grateful as a complete separate analysis for this extraordinary person for changing the expected outcome.
I am not a statistician but understand how statistical analysis works. Considering all observations, mentally considering probabilities as per expert opinion and discounting accordingly, I believe highest probability is contaminated fuel.
For example, dual engine failure is a near impossibility so forget it. A pilot turning off the running engine on a 787 is a near impossibility so forget it.
I made an additional observation which I have not read before. The clear plume of dust appears only on the left side of the plane on take off. Despite there being a small building in the way, the shear size of the plume of dust indicates something should be visible on the right side as well. Based on that and knowing the engines did turn off (RAT), engine one fails on the runway past the point of aborting, engine two fails around 5-10 secs. after takeoff. Given all other possibilities are unlikely for this plane and with trained pilots, this is the most probable event.
Note, I do not believe there is sufficient observation of the videos which is a small point but more importantly, for non aviation experts to add their value (maybe there is a statisitician waiting for the full data), there is an insufficient list of possible critical failure modes. They are only what some pilots believe are the possible failure modes and in my view, all conclusions so far even from seasoned pilots rest on highly improbable events or ignore some observations.
Also, it does not help for anyone to post wait for the official investigation. I do not believe this is a sick interest in suffering of others. Most people fly and want peace of mind. Most people would like to know whether it was a freak incident or an issue with an airport, country, airline so as not to use or visit, etc. before their next trip.
Brief-Visit-8857@reddit
https://www.business-standard.com/amp/india-news/air-india-crash-icao-expert-joins-investigation-as-observer-125062800265_1.html
Looks like they did grant the UN (ICAO) observer status after all
Low-Computer8293@reddit
Thought this was interesting. The UN offered to send a person as an observer to assist with the investigation, but India denied them access. The article states that India has been criticized over delays relating to black box data. I'm not surprised they are being criticized but this is the first article I've read that stated this.
The more time elapses....
https://www.benzinga.com/news/politics/25/06/46133937/boeing-787-dreamliner-crash-india-shuts-door-on-un-aviation-expert-probing-plane-accident?utm_source=MarketWatch&utm_campaign=partner_feed&utm_medium=partner_feed&utm_content=site&mod=mw_quote_news
Brief-Visit-8857@reddit
In every other crash the UN was asked to provide help, they didn’t offer it. Weird that they would only do this for India.
Fantastic_Egg949@reddit
Question: Indian authorities state they have downloaded data from the black boxes, BUT will they have the equipment and the know-how to accurately analyze that data? Downloading data and being able to interpret it accurately may not be guaranteed at a month old, brand new lab. Does anyone else think these black boxes will eventually need to be sent to NTSA anyway to get all the data extrapolated accurately?
Brief-Visit-8857@reddit
There was a team of NTSB investigators providing assistance with extraction of the data. They will do the same in interpreting it.
Tough-Candy-9455@reddit
I think the actual download would have been the difficult part. But seems like they have not opened the undamaged, aft EFAR so they're probably keeping it in back-up if anywhing goes wrong.
pokachipokachi@reddit
Commenting just not to lose this thread
JournalistSpecific61@reddit
We're the wing tanks light with Gravity sloshing the fuel away from inlets after the plane pitched nose up.Starving both engines immediately of fuel especially if less than a few tonnes in each .Maybe the bulk of the 50,000kg fuel was in the centre tank with those.pumps off
chillebekk@reddit
The fuel tanks were completely full (125k litres/100 tonnes), so the point is moot.
railker@reddit
Main/wing tanks are always filled and kept full until the center tanks are empty. Main tank pumps always on, center tank pumps just have a higher output and override them until that fuel is used. If it was 50,000kg loaded on, about 16,000kg/20,000L would be in the center tank based on fuel tank capacity on the -8.
Fuel 'sloshing around' wouldn't suddenly be a big problem after 11 years of flying. The 30-year-old airplanes I work on already had that figured out, even, venturi fuel pumps constantly fill a segregated 'collector bay' containing the AC fuel pump and the fuel feed for the engine.
Simbaa0110@reddit
As per latest press release, the data has been successfully extracted in delhi lab itself
https://www.pib.gov.in/PressReleseDetailm.aspx?PRID=2139785
chillebekk@reddit
Why on earth did they keep the black boxes in Ahmedabad for 11 and 8 days, respectively?
Hawk1982@reddit
Finally some update! How soon will they be able now to analyze the extracted data?
Brief-Visit-8857@reddit
Since the data has been extracted, I assume all they have to do now is put together the sequence of events. Probably 2-3 days at the latest.
thefreeman06@reddit
https://timesofindia.indiatimes.com/india/ai-171-crash-data-from-front-black-box-downloaded-probe-on-says-government/articleshow/122087020.cms
Its on major news channels as well now
maglen69@reddit
India aviation regulator says multiple defects reappearing on aircraft
DaBingeGirl@reddit
This is worrying. The more they drag their feet on examining the boxes, the more I think the crash was caused by maintenance fuck up.
maglen69@reddit
They really seem desperate to find some way to connect this back to Boeing but that's going to be really hard when it's an 11 year old plane and the new engines are manufactured by GE.
DifferentManagement1@reddit
On the other sub with all the pilots, multiple 787 pilots speculated that they think this was a cockpit problem vs an airplane problem
DaBingeGirl@reddit
Agreed. I'm struggling to see how this is a Boeing or GE problem, but I think you're right that Indian/AI officials want to pin this on one or both of those companies.
MortimerDongle@reddit
A design flaw is possible, of course, but with a popular plane that's been around for a while you'd think it would have to be a fairly unique situation.
DaBingeGirl@reddit
That's pretty much what I'm thinking too. I'm glad they finally downloaded the data, hopefully we'll know at least a basic cause soon.
Tough-Candy-9455@reddit
When will a single government body in India be proactive for once? Check out the report of the Air India Kochi crash, AAIB has an entire section calling out recommendations that DGCA had made after the 2008 had but had never followed up on whether it's recommendations were implemented.
Hope they see that the defects are rectified even if they had nothing to do with the crash.
Tough-Candy-9455@reddit
https://www.pib.gov.in/PressReleseDetailm.aspx?PRID=2139785
Press release today. Few interesting points...
The black boxes
As mentioned elsewhere in this thread, the 787 has two EFARs, each of which can perform the function of both FDR and CVR.
Aft EFAR: Recovered from the roof on 13th June, presumably from the (relatively) undamaged tail ...... Brought to AAIB lab, Delhi on the 24th at 1715 hrs
Forward EFAR: Recovered from wreckage on 16th, arrived to AAIB lab on 24th at 1400 hrs..... Data successfully downloaded on 25th by members of AAIB and NTSB
Note that this EFAR is supposed to have a 10 min battery backup in case of power loss, which would be helpful if it was indeed a dual engine failure. (I do know that the RAT gives power to the CVR only in an A320 but no idea about here)
The investigating team
Led by DG AAIB, and includes an aviation medicine specialist, an ATC officer, and representatives from NTSB
LostBattery@reddit
https://substack.com/profile/96232296-miles-obrien/note/c-129332794
Via Miles O'Brien's substack:
NorthernEwan@reddit
This has been circulating for about a week. Its not real.
Low-Computer8293@reddit
I couldn't confirm this on any major news site, so I think you are right.
NorthernEwan@reddit
It sounded plausible! … but there are loads of errors, like the accident date was the 25th June. Also they mention AirBus specific technology instead of Boeing.
Finally, they have Airworthiness Directive already! Wow.
😂
Busy_Comedian_8165@reddit
Also the use of Emoji's doesn't scream professionalism. "Crashed due to negligence, slay 🤟🌶"
Blythyvxr@reddit
Oh for fucks sake, this bullshit again.
Velvet_Llama@reddit
Chief engineer Miles O Brien himself said that?!!?!
postusa2@reddit
I like me boxes like I like me coffee. Black and double suite.
am6502@reddit
Crazy. How long had the rainwater been draining parts of the aircraft internally? The video footage does not show rain, only maybe moderate clouds and high humidity in my possibly incorrect recollection.
railker@reddit
Nope, and by airport weather reports it hadn't rained in at least 6 hours. Haven't bothered to look back even farther. Just one of many clues that this is one of many false reports floating around. They haven't even opened the boxes yet, news reported just yesterday they were still deciding where to send them for analysis.
Velvet_Llama@reddit
The rain was just hiding, waiting to ambush that poor plane!!
Super_Forever_5850@reddit
Seems like a big design flaw to make an engine control system who automatically idles the engines when the FADECs are lost.
Maybe this makes sense if the plane was on final approach but it should be possible to make it so that this can never happen during take off?
alfcalderone@reddit
shit
WorthDues@reddit
Is there a typical timeframe for a preliminary report or is mostly case by case basis? I heard one of the aviation sites had knowledge it would be coming out in the next few days but I cant find it anymore.
DaBingeGirl@reddit
This is highly unusual, given how quickly they recovered the boxes and the fact there's no obvious reason for the crash. With the CRJ and Jeju crashes there were press briefings pretty frequently to give a timeline, ATC communication, etc. This is weird. I wouldn't be scared to fly on a 787 give this is the first ever hull loss, but it would be good to know if this was a major fuck-up by the pilots, a software issue, maintenance issues related to that specific plane, etc.
tangled-wires@reddit
I have a dreamliner flight in July (two actually) and am having trouble convincing myself that I should continue forward with the trip. You would still get on one no second thoughts?
MortimerDongle@reddit
Even if the cause of this crash is identified as a design flaw, it would most likely be a very unique situation. 787s are popular airplanes that constantly fly long haul routes all over the world, and this is the first serious crash. It's not going to be a 737 Max sort of flaw that happens fairly often.
I also have two flights on a 787 in July and am not second guessing it. The most dangerous part of our trip is the drive to the airport.
DaBingeGirl@reddit
No second thoughts. You're in more danger going to and from the airport.
Unpopular opinion, I think this is going to be an isolated incident. MCAS was a known problem that was ignored, but a lot of pilots and Boeing were aware of the issue. In this case, there's no consensus on a cause. It's possible it was a once in a million situation, but if there was something wrong with the design of the engines or a programming issue, I think it would've come up by now and pilots would be talking about it.
And I'm just gonna say it... India dragging their feet on the black boxes is weird. Investigations take time, but analyzing the data is usually done quickly to determine if it's an isolated incident or a bigger problem. It kinda makes me think there might be some evidence this was a pilot or Air India issue that they don't want to admit to yet (wait as long as possible, hope for limited media attention). I hope I'm wrong, but it's hard to understand what's taking so long.
sadChemE@reddit
Also, I agree on the unpopular opinion. Likely isolated event. I'm leaning towards maintenance. Could be wrong, but the delayed data assessment and updates is sus 🤨 also the conflicting news articles and accounts of things like ATC audio rando ppl that knew the pilot are sketchy.
fugutoxin@reddit
I’m a nervous flier and take a carefully titrated dose of a benzodiazepine before I fly, usually alprazolam. Works great and because benzodiazepines cause anterograde amnesia, even the longest flight always seems like it took no time at all.
cypherpunk00001@reddit
alprazolam also known as xanax.. that medicine does wonder but is hell if you become addicted
fugutoxin@reddit
That is correct. Which is why I carefully titrate the dose and only use it for flying.
t-poke@reddit
Thousands of Dreamliner flights are completed daily without incident. This is the first hull loss and fatal crash in over a decade of service.
The only thing preventing me from getting on one today is that I’m already on vacation and I don’t want to cut it short.
Woodnymph1312@reddit
This. I also have flight anxiety (working on it though) and even I would still step into a dreamliner with no second-guessing right now. My work around though is that I only fly with highly renowned airlines (just helps my head).
SpaceDetective@reddit
Those crashes didn't centre around a technical issue whereas this one currently looks like a higher chance of that which might lead to a more cautious approach.
Mentour Pilot says preliminary reports vary "from weeks to months".
DaBingeGirl@reddit
Correct, but communications with the tower and basic data was almost immediately, with follow-ups as they got more information. The total lack of information, plus dragging their feet on the boxes is very strange. If it wasn't human error, then they need to speed up finding out what happened. We're at nearly two weeks, that's a lot of time lost in the investigation.
SpaceDetective@reddit
Just saw the report they haven't started reading the data yet so yeah even if they had to invite some NTSB over they ought to have started the decoding by now. Still think this one will likely go slowly, there were ~1700 parameters to read on those Max 8 crashes.
DaBingeGirl@reddit
I'm stunned it's taking so long, feels like it's mostly about ego (India just opened a lab capable of examining the boxes, but they have no experience with boxes damaged this severely). It could be a complicated, long investigation, all the more reason to move fast. At least this doesn't seem to be a common problem like MCAS, but it's still worrying that there isn't an obvious cause.
fugutoxin@reddit
I think you’ve highlighted one plausible explanation for the delay. As I understand it, you get essentially one chance with the data extraction from a severely damaged black box. I can therefore understand why Indian authorities might be taking their sweet ass time making a decision about how to handle the decoding. If the lab in India does it, they might succeed or they might damage the evidence and face widespread outrage. Transferring the black box to the Americans or a European body might be the more prudent move in terms of risk mitigation since these other facilities possess more experience. However, that might come at the cost of some amount of national prestige. A reasonable compromise might be to have Indian investigators on sight in one of these foreign labs with an official designation as some kind of ad hoc joint investigative unit, with everything done under the supervision and permission of the Indians.
DaBingeGirl@reddit
Yes, I think national pride is playing a huge role here, which really upsets me. I understand them wanting to prove they can open the boxes, but this really is a job for the experts and there shouldn't be any shame in recognizing limitations. Indian officials would be present for the entire process (opening and analysis), plus it's recorded.
Baleful_Vulture@reddit
It's supposed to be within 30 days, so it might be a while yet.
Brief-Visit-8857@reddit
Today marks 10 days. And we have learned absolutely nothing new. I don’t know why they’re taking so long to decide where to send the EAFRs.
railker@reddit
Well it's the weekend, that's obviously a Monday problem.
Brief-Visit-8857@reddit
Real
railker@reddit
Looks like as of today, EAFRs are confirmed to still be in India under examination by the AAIB until a decision is made on where to send them for analysis.
Funkytadualexhaust@reddit
Amy Indians want to chime in to what is going on? Sounds political which is painful.
railker@reddit
Honestly. If you're worried about American/Boeing bias, send it to France or the UK. ez. done. Unless they're still trying to determine if they can do it themselves.
DaBingeGirl@reddit
I don't understand why they're not sending it to France or the UK, although I wouldn't be worried about the NTSB. If the cause was obvious I'd understand doing it themselves, but not in this case.
HumansNeedNotApply1@reddit
Because it's their prerrogative to do it themselves, apparently they had a logistical issue in transporting the black boxes to the lab, they only got there in the 24th of june.
thefreeman06@reddit
It's a waiting game for up to 3 months for a full prelim report, no other details are published yet for now
bam-RI@reddit
I think the AAIB needs to be sent for analysis.
railker@reddit
The AAIB has analyzed the AAIB and found no faults.
Brief-Visit-8857@reddit
Idk what they need to look at if they can’t access the data. There are hundreds of 787s flying around everyday, if this was a issue with the plane then they need to ramp thing up
stuntin102@reddit
looks like the finger pointing and face saving has already started.
fugutoxin@reddit
I didn’t realize how big Ahmedabad is - 7.5 million people. No chance one person was listening to ATC communications at the time of the accident?
Some1-Somewhere@reddit
Indian rules apparently forbid eavesdropping on radio converstations not meant for you. Same in UK and NZ.
cypherpunk00001@reddit
you'd have to be comically dumb to get caught eavesdropping on radio
fugutoxin@reddit
You can listen to ATC communications from most airports around the world: https://www.liveatc.net/.
WVVVWVWVVVVWVWVVVVVW@reddit
Thanks for sharing, it was interesting to listen to.
I heavily considered commercial aviation but I just cannot following these communications. I'd need someone to say it very slowly and clearly for me.
It took me like 5 attempts to get my amateur radio license because I couldn't keep up with the morse code part.
cypherpunk00001@reddit
yea I'm saying if you are in the UK or India or wherever it's illegal, how dumb would you have to be to get caught? It's one way reception. Even if you invited a cop into your home for a tea while you're doing it on speaker, likelihood they don't even know what it is you're listening to or even that it's illegal.
Some1-Somewhere@reddit
If you're rebroadcasting it online, triangulation would probably be pretty straightforward for the authorities if they really cared.
fugutoxin@reddit
I gotcha. Maybe some aviation nerds in Ahmedabad were listening illegally at the time. A city with 7.5 to 8.5 million people in a country with a lot of young techies? It’s within the realm of possibility. But it’d never come out publicly if they were.
Some1-Somewhere@reddit
And publishing what you eavesdropped would be the best way to speed that process up.
fugutoxin@reddit
Thanks for clarifying. I was surprised to see that LHR ATC is unavailable on www.liveatc.net.
fugutoxin@reddit
So you can’t use the Live ATC website in the UK?
thefreeman06@reddit
This culture does not exist here, we just dont get around to doing something like this. The legal aspect of it aside, if activists do do something like this, it wouldn't be public knowledge anyway. There is a separate legal process to get information out (RTI) however it takes time which for this purpose beats the whole point
fugutoxin@reddit
I didn’t realize ATC communications were off-limits to listening in India.
WispyPrincess@reddit
Plane spotting and listening to ATC are both illegal in India. Police even questioned the guy who took the mobile video.
fugutoxin@reddit
I see. That would explain why it seems no Indian airport is available on www.liveatc.net.
am6502@reddit
Just checking in for some TLDNR type updates. I'm still puzzled that a speedy black box recovery and analysis isn't providing news channels with a preliminary answer to the mystery of 787 crash. Here goes:
What are some things the black box is telling investigators, and how long did it take to recover it?
Assuming both engines flamed out. Isn't the APU still there to provide electrical power (thus preventing deployment of the rat generator)??
DaBingeGirl@reddit
They haven't analysed the data yet, they're still deciding if the boxes will stay in India or go abroad. They're badly damaged and they don't have experience, so there's a risk in damaging the data if opened incorrectly. Frankly I'm stunned there isn't more international pressure for them to send the boxes to the US or France.
PowermanDL@reddit
Take this with a grain of salt, but avherald is reporting that Indian officials have stated that the black box is staying put and being analyzed in India.
OnlyForF1@reddit
They should send one to the USA and one to France...
DaBingeGirl@reddit
It's all recorded and Indian, plus AI officials would be there, so there's really no risk of a cover-up. The NTSB also has a great reputation, they don't fuck around with their reports. At this point, I think there's more of a risk that India will try to cover-up what happened, given how they're dragging their feet.
Tough-Candy-9455@reddit
APU is switched on manually and takes around a minute. There wasn't enough time.
am6502@reddit
Aww geez. Thanks.
As part of normal procedure couldn't they keep the APU on (or restart when cleared for take-off) until the airplane more or less reaches altitude?
sizziano@reddit
No, keeping the APU on for take-off isn't normally part of SOPs but it does vary per airline.
am6502@reddit
I suppose the added drag of the RAT likely wouldn't have made much difference for such a heavy aircraft as the 787.
I was a little bit surprised the APU (which it looks must be a turbine?) would take so long to spool up to provide bare minimal electricity to run the flight control (in the age of 100% fly-by-wire). If the APU were piston engine is would take about one second to have full power.
As for the role of the RAT and the issue of sufficient redundancy (for what I'm guessing may be a 100% electronic fly-by-wire without mechanical backup of pitch and one other axis) why not have two piston engines, one of which is always at idle or power, and generating some electical power, and another to kick in for higher demand or need for redundancy. The max power requirement for one such engine would be just enough power for normal flight control.
sizziano@reddit
Piston engines are likely too heavy and unreliable. Also it would have to be a diesel to be able to run on jet fuel and that means it would need to be heavier. I can't imagine a diesel generator having better power to weight than a gas turbine. Also running at altitude would be problematic. There's probably a dozen other good reasons you'd never want a reciprocating engine as an APU on a transport category aircraft. Oh yeah while this doesn't really apply to the 787 a turbine APU made starting the engines with bleed air relatively simple.
Try starting a diesel at 30k feet lol.
am6502@reddit
Good point that diesel/kerosine engines put out so much less power (per engine weight). So to replace the ~600hp APU it would take two pretty hefty sized diesels engines---roughly, a mall shipping container sized bulky mass someone1-somewhere summarized above.
Maybe a turbo diesel assisted with oxidizer (a compressed O2 tank) could still get it started and run until the aircraft gets down to altitude.
Well.... in any case it looks like my two piston engine suggestion would be a very poor attempt at a solution. It might have to be some CODAG-like arrangement, where you have a piston engine integrated with a turbine, such that the piston engine would always be running and there to provide a minimal to sub-minimal level of power at very high efficiency, and it could assist in spooling up the turbine quickly when there is a call for demand.
Some1-Somewhere@reddit
Cartridge-start turbines exist, but there really doesn't seem to be a need. What does an engine starting in two seconds get you that a pair of 30kg batteries and a RAT doesn't?
Plus, an engine raises all the same fuel exhaustion or contamination issues.
sizziano@reddit
The 787 APU makes about 1,100 shafts horsepower FYI. But yeah reciprocating engines are not going to be a viable solution hehe.
Some1-Somewhere@reddit
Flight control on the 787 will run off the main battery, two dedicated flight control batteries, the four normal generators in the engines, three dedicated flight control generators in the engines (that will run down to lower speed than the normal engine generators), or the RAT.
And the APU will autostart.
There are no signs here that they lost flight control power.
RAT is a 1-2% fuel burn penalty I believe.
am6502@reddit
very informative, thank you so much!
I guess the RAT seems like a pretty good solution. Minor added drag that probably is unlikely to make a difference in most scenarios.
One-Work-9249@reddit
Punch News says it was the seat recliner!?
Some1-Somewhere@reddit
There was an AI slop report 'published' about that.
Completely untrue.
One-Work-9249@reddit
Thank you. Will delete comment since it’s fake news
One-Work-9249@reddit
https://punchng.com/pilots-faulty-seat-caused-air-india-crash-report-reveals/
FutureHoo@reddit
Fucking hell, captain steve released another AI171 video. He’s really milking this tragedy for views huh
Elegant_Shop_3457@reddit
Are we up in arms that aviation YouTube is covering a major passenger jet crash?
gonzxor@reddit
No. Everyone hates him because he said it was pilot error on news interviews. It was already suspected the RAT was deployed from the beginning, it was a terrible take but he did it anyways for publicity.
Max-Verstappen-33@reddit
Why didn’t they abort takeoff?
sadChemE@reddit
I had this thought as well, but I'm assuming they didn't know of any issue to abort for until beyond point of no return.
Elegant_Shop_3457@reddit
He said pilot error (retracting slats instead of gear) was one possibility.
ECrispy@reddit
are you his shill? his video was titled 'what really happened'. he went on every possible news media/interview repeating it was pilot error.
he's never apologized. no other 'expert' does this without having any data.
then he lied and claimed 'RAT was new info' when it was in every video and discussed from very beginning.
he's made $$$$, maybe 200-300k, thats why he's doing this, he's shameless
Elegant_Shop_3457@reddit
The video is titled "what really happened?" Notice the question-mark? He never said it was definitely pilot error.
moustache_disguise@reddit
I think the rush to generate revenue off a tragedy is distasteful.
Blythyvxr@reddit
More that he’s spouting uninformed speculation to make bank off of a disaster.
There’s a big difference between reporting consistently on aircraft incidents, sticking to established facts, and using professional insight to add context, vs jumping on the crash du jour, blaming the pilots for the incident with absolutely no evidence, using sensationalist thumbnails of explosions with his face looking all concerned… at the same time earning between 12k and 60k USD per video.
Snuhmeh@reddit
He's the one one really still making videos about it. If Juan Browne would finally make a deep dive video, it might matter. I suspect the news cycle has moved on though.
Efficient-Ask-4452@reddit
There’s nothing new to talk about so why would he? Literally covered everything that’s public so far
BUNNIES_ARE_FOOD@reddit
Juan Brown will probably do a deep dive when there is something to actually report on.
Efficient-Ask-4452@reddit
Don’t trust “pilots” that feel the need to make videos with fake backgrounds of airports and wear full pilot gear. It’s fucking pathetic shit, even if they’re genuine pilots.
tharmor@reddit
and increase his subscriber base !
According-Layer9383@reddit
It's been over a week since the crash why has India still not "made a decision" as to where they will send the black boxes (US, UK, etc.)?
Seems very irresponsible of India. The data needs to be extracted and analyzed ASAP, given there are so many 787s still in operation.
Brief-Visit-8857@reddit
They have to consider the implications. I believe they think that if they send it to the US there might be bias as Boeing is a US company. So they might send it to France or the UK. That’s what both Indonesia and Ethiopia did after the MAX crashes. But I agree they are taking wayy too long.
PmpsWndbg@reddit
Unfortunately, I think that is a very valid concern.
Humanist_2020@reddit
Absolutely.
ikilledtupac@reddit
They’re probably hiding evidence for Tata
AtomR@reddit
Nope
https://www.reddit.com/r/aviation/comments/1ld9yb8/air_india_flight_171_crash_megathread_3/myxbten/
Automatic4k@reddit
I think they got data from the tail black box and sending the one from the front. There were photos/videos of them carrying the orange box and didn't looked damaged. That might have been the tail black box.
railker@reddit
Which doesn't have a backup power supply, so if there was a full loss of electrical power, it would've stopped recording. Leaving only the front one having data from after that moment.
ECrispy@reddit
send it to AAIB in UK then. either way its ridiculous nothing has been done so far. Boing must be loving this, the last thing they want is to uncover yet another defect. this time its a much bigger carrier and plane.
drtywater@reddit
Agreed. There were UK citizens on the flight so its pretty easy to justify. As the engines where non Rolls Royce there won't be speculation of bias. If they have issues decoding the NTSB would assist but I doubt UK folks would have any issues. They can say they don't have the resources but since UK had second highest number of citizens/residents on the flight they can handle it and that would save face to the US as well.
NigroqueSimillima@reddit
It's extremely irresponsible, the Ethiopian government did this way faster.
stuntin102@reddit
not sure what’s going on with these delays, especially since there were two redundant black boxes and a cockpit video recorder.
zeldaxzora@reddit
if the fuel was contaminated as is being speculated, why / how would that happen?
Longjumping-Boot1886@reddit
not in any condition possible with two engines in seconds.
There is a lot of different random phisics processes happening on separate tanks, pumps and wings to make it happen in one short period of time.
bobblebob100@reddit
Fuel contamination just doesnt make sense really.
The engines were running during taxi and at full power on the runway and presumably all was fine
Mr_Tiggywinkle@reddit
Not an expert, but I can share examples?
https://en.wikipedia.org/wiki/Cathay_Pacific_Flight_780 for example had damaged fueling filters contaminate the fuel with polymer particles.
https://asn.flightsafety.org/wikibase/233878 a maintenance crew directly put in 30kg of biocide into the fuel tank when he was supposed to put in 800g. (Double engine trouble ensued (surging + 1 engine stalled), but they managed to fly it on low power to the ground).
https://skybrary.aero/sites/default/files/bookshelf/35241.pdf this one was caused by too much water in the pump that refueld the plane, they swapped to a different pump, but enough water had entered by that point that it caused surging midway through the flight.
There was also one involving ice crystals on landing, but that wasn't contamination, rather it was a peculiar set of circumstances that allowed "sticky" ice to form and then to block fuel flow, but it shows that contamination can occur during flight based on flight conditions, even if the fuel was fine before - very specific circumstance though.
zeldaxzora@reddit
thank you! very interesting & informative ☺️
Mithster18@reddit
There's one that happened to British airways. Water got into the ground tanks, and then into the plane, water froze, blocked lines, plane landed and then ice melted.
Powerful-Ad2338@reddit
There was a Jetstar 787 that had an engine rollback and RAT deployment too due to Kathon contamination
https://asn.flightsafety.org/wikibase/223675
AlphaPapaCharlie@reddit
As a PIC on the A320s I have already experienced Thrust Control Malfunction due to a faulty engine probe (on ground).
My theory is that this happened on both engines probes while the wheels sensors were still signaling “on ground” maybe just before V1 or at V1.
And the residual thrust from the fans spinning might have given them the few seconds of flight time.
This is compounded by the somotogravic illusion which the survivor noticed just after liftoff.
I fly often into AMD and this time of the year there is a ton of visible dust or particles, common for AMD in summer where round airborne seed-like pods are prevalent. Maybe this clogged up the engine probes and sensors?
I remember GEnx used to be notorious for sensor blockage and thrust rolling back especially with ice crystals.
fugutoxin@reddit
Do you have any idea what those seed-like pods in AMD might be?
AlphaPapaCharlie@reddit
Those floating pods are likely from Prosopis juliflora or similar desert shrubs common in that region of India. In summer, they dry out and break into light, fluffy seed-like structures that float around easily in hot, dry wind. They’re harmless generally, but can look dramatic near runways.
fegelman@reddit
But in this kind of a sensor malfunction, the thrust would be reduced to idle as opposed to the engines turning off entirely right? Because the latter would lead to a RAT deployment but not the former
Tslover1389@reddit
On the 787, TCMA completely shuts off fuel to the engine it suspects is in uncontrollable high thrust, not reduces to idle. It is a single point failure system from what I can tell. The FAA granted Boeing’s request for exemption of the TCMA system from the regulations against single-point failure systems in 2018: FAA Exemption Approval Notice
Past-Ad9310@reddit
Did you read the link? The exemption is kinda the exact opposite of what you are implying. It gives relief for single point of failure leading to uncommanded high thrust. The TCMA was the solution to the single point of failure leading to UHT.
AlphaPapaCharlie@reddit
Yes, It does. Atleast on the A320 Neo, the fadec drops the engine back to idle on ground and if needed even do an auto fuel cutoff to shut down the engine. There was an event in our airline where the pilots after touchdown got an engine failure. Later was found to be TCM kicking in to protect the engine as it sensed an abnormal condition when the pilots used reverse thrust. Later they realized it was due to a faulty T2 sensor probe on the engine (temperature sensor)
I am unsure how the function works on GEnx engines, any 787 pilot or someone who has experience on GEnx engines might be able to confirm.
Even if it happened in the AI171. It must be a freak incident where it happened at the exact same time. Likelihood of that happening is close to zero.
fegelman@reddit
Hmmm if what you're saying is true about the 787-8, that 2 faulty sensors can lead to 2 engines shutting down, maybe its not that unlikely, given Air India's questionable maintenance standards. And personally I've experienced phones and cameras malfunctioning at these high temperatures (even 35C+, while it was 43C when the accident happened). So it doesn't seem so far fetched for sensors to be affected as well.
AlphaPapaCharlie@reddit
Usually the sensors are rated for temperatures of much much more around 1000-1200 degrees celcius , so it usually shouldn’t cause an issue unless there is something causing a bad signal input like for example a blocked probe. In the CCTV footage of the takeoff there was a giant plume of dust upon rotation (which looks like wake vortices), which clearly says that there was dust everywhere and possibly other airborne contaminants.
There was an issue with GEnx historically back in 2014 when JAL had reduced their operations after some other GEnx operators had spurious temperature indications due to probes being blocked by icing.
clutch-cream-run@reddit
Can pilots deploy RAT manually?
AlphaPapaCharlie@reddit
Yes. You have an option to deploy it manually for a few of the abnormal procedures. On the A320 if an electrical smoke/ fire is suspected one of the action is to shut down both the engine driven electrical supply and put out the RAT so that only a few critical systems are powered, On a normal day, a pilot would not put on the rat and its not easy to do it accidentally as well because the switch is guarded and needs confirmation from both pilots before operating it.
Loose-Ad439@reddit
This may be a stupid question... And maybe asked already but if this happened in an area that wasnt so populated where the plane could have landed somewhere other than where it did (like a street or field etc) I'm assuming there would have been a different outcome? The plane most likely would have been able to land safely?
js5180@reddit
There is a river a few thousand more feet away. Unlike the Hudson River landing, this plane had gear down so it’s not clear how that would affect a water landing. But every additional foot of altitude would have led to more time and more options - roads, fields, river, etc.
c0mrade34@reddit
Also there's easily 4 - 5 bridges on the Sabarmati river which see heavy traffic during the daytime.
xorbe@reddit
Look at google map, they sadly augered into the end of a building. If they could have been a bit left, probably more survivors, but still ugly.
Baleful_Vulture@reddit
It's possible there would have been more survivors but a "safe" landing would be unlikely - the plane is full of fuel, and if it's uneven ground or there are other obstacles/structures there is a high chance of rupturing the tanks and causing a fire.
skystream434@reddit
I am wondering - would there have been clearly less casualties had the plane landed in an open field and not between buildings?
Brief-Visit-8857@reddit
Possibly. But the airplane was filled with fuel for a 8 hour flight. Obviously people on the ground won’t die, but the jet fuel will still cause a lot of casualties.
MyDespatcherDyKabel@reddit
STILL boggles my mind how that survivor escaped. Explosion and fireball was instantaneous. Saw this new angle of him escaping yesterday - https://youtu.be/hQGnqrgglrw
Spare_Math3495@reddit
There is a stewardess that survived a plane disintegration mid air and falling straight from the sky from god knows how many kilometers above the ground.
If that’s survivable, anything’s survivable.
Sometimes there’s no logical explanation it’s just incredible luck.
MyDespatcherDyKabel@reddit
Which flight was that?
fnezio@reddit
JAT Flight 367
MyDespatcherDyKabel@reddit
Thank you
fugutoxin@reddit
It is miraculous. I have a morbid curiosity in how highly-skilled individuals like pilots react under pressure and when faced with the unexpected. A horrific case of man-not-understanding-machine is the Air France 447 crash. That was a crash I hope no one survived - to be faced with drowning after crashing into the middle of the Atlantic. The Brazilian pathologist who conducted the autopsies on the bodies recovered indicated that they were too decayed to make a determination as to whether there was water in their lungs, a finding which would be consistent with drowning. I sincerely hope no one initially survived that crash.
pipic_picnip@reddit
Pilots usually don’t have time to process the incoming death because they are busy fighting the plane to save lives until their last breath. They are unsung hero who are first to be crucified until proven innocent in every crash, because it is more tangible for people to blame a person as a figurehead of the tragedy than some random fault they don’t understand.
That being said, no matter what training you get, one cannot predict how a person behaves in the moment of death, it just isn’t possible. It’s a bridge to cross only upon death from where people do not return to tell a story. If the pilot just sat there for last 2 minutes to recount their life before their imminent doom, I honestly wouldn’t blame them. There is no procedure we can train on to accept our death willingly. We can train rigorously for it for years and years, but how our mind acts in the moment when it arrives, no one knows.
David905@reddit
AF447 however was almost completely pilot error. And they had plenty of time to correct it.
fugutoxin@reddit
Agreed. Do you recall the instance where the flight computer stopped relaying stall warnings because it judged what was happening to be too far beyond the pale? Only to have the stall warnings reactivate once the AOA was directed (somewhat) down as it should have been far more aggressively from the very beginning. That crash was a warning to all airlines to reemphasize the importance of manual flying skills.
David905@reddit
Yup I do recall that. I also recall that the main captain (I don't know the proper terms/acronyms) repeatedly told the flying pilot to put the nose down to level flight. Which he did for a few seconds, then, against orders, pulled up again in a panic seeing that their altitude was still dropping, and probably thinking that less alarm noises=better. Total ineptitude of basic flying. The main captain should have removed him at the first hint of panic and failure to obey orders.
fugutoxin@reddit
Yes, a total loss of situational awareness and poor airmanship. He thought by going to TOGA thrust and massive pitch up that that would get the aircraft out of a fully developed stall. Flight school 101. Despite the “startle effect”, those actions and others point to a lack of basic flying skills. The BUSS was a simple and elegant way of compensating for that.
KnowLimits@reddit
Agree about the poor airmanship, but there's a big human factors thing in the design: in normal control law (with envelope protection working), trying to pitch up would work - in fact, in some sense, optimally. So it's easy to see how someone could pick up that awful habit in a simulator. But the accident flight was in alternate law at the time.
fugutoxin@reddit
Could you elaborate on how in normal law pitching up would work optimally in this case?
KnowLimits@reddit
In normal law, the computer will not allow you to get above the critical angle of attack (i.e., it won't let you stall). So by holding the stick fully back, the behavior you can expect is for the plane to pitch as necessary to reach the critical angle.
Suppose you're in a dive, not stalled, and you'd like to stop your descent. In a plane with purely mechanical linkage (or Airbus in alternate law), you need to pull the yoke back, but not too far - when you hear the stall horn, or feel the stick shaker, or get buffeting, that's your cue that you're right on the cusp of the lift vs AoA graph, where you want to be to arrest your descent as quickly as possible (to the first order). And of course if you pitch up further, you're stalled. But in Airbus planes in normal law, you can just hold the stick fully back, and the computer will hold you at this best lift AoA.
Suppose you're in a deep stall, and you'd like to stop your descent. In a plane with a purely mechanical linkage (or Airbus in alternate law), you need to push the stick forward to get back down to your critical AoA. That's the correct thing, and it's what they teach you, and it's even what you should do for an Airbus. But if you don't do that, in an Airbus in normal law, it's fine - the plane will pitch down at least to the best lift AoA no matter what you do.
Basically - if you're descending more than you'd like, and you want as much lift as possible, so you want to be at critical AoA, and in an Airbus in normal law, holding the stick fully back should always achieve that.
(One caveat... if you're on the back side of the power curve, as you might be at very high altitudes, in the long run it may be better to pitch down a bit so as to accelerate to your best glide speed. But this is kind of a second order effect - the airspeed is going to change more slowly than the pitch. Just focusing on the instantaneous effect, though: plane go down - pitch for AoA of most lift - plane go down less.)
fugutoxin@reddit
This makes sense. Except the pilot would be making the wrong inputs based on an incorrect understanding of the situation. In addition, it’s hard to even conceive of an Airbus aircraft in a fully-developed stall while in normal law because normal law will not permit that to happen to begin with.
fugutoxin@reddit
But I am referring to those instances where a pilot is fighting the plane until there last breath, sometimes unwittingly leading to the crash itself. Air France 447 was a tragic case of that. Had the FO simply stopped pitching up and unintentionally inducing a stall, and instead pitched down and traded speed for altitude, the accident would likely not have happened.
DifferentManagement1@reddit
It broke up upon impact, no? Hitting the water like that is like hitting concrete
fugutoxin@reddit
The force which the aircraft impacted the water’s surface was enormous. Large sections broke up. Still, the rudder was located on the surface, large sections of the fuselage were located on the ocean floor. The food service carts were partially compressed from being thrown up so violently and hitting the ceiling of their compartment. It is possible, however unlikely, that a few people did survive the initial impact. To be clear, I think it is highly unlikely anyone did survive. I certainly hope no one did. Post-mortem analyses of the bodies recovered could not conclusively prove that due to their state of decay.
Brief-Visit-8857@reddit
Air India has bought the option where there’s a Camera in the cockpit along with the FDR and CVR… so we might actually get video of what went down in the cockpit
AtomR@reddit
No way they're releasing the video of cockpit to the public. It hasn't happened before, so Indian authorities will follow the protocol.
Brief-Visit-8857@reddit
Air India has bought the option where there’s a Camera in the cockpit along with the FDR and CVR… so we might actually get video of what went down in the cockpit
Tough-Candy-9455@reddit
I think anyone would have survived AF447. That one had massive vertical speed despite being stalled.
fugutoxin@reddit
I agree and I hope that was the case. In crashes like that, where survival is worse than instantaneous death, one hopes that the end came as close to instantaneously as possible.
JuanSmittjr@reddit
this guy is fake.
no way he's been on the plane.
coming out of the garden in white tshirt, phone in hand? he has fallen from the sky and was blown, still no broken limbs, no limping,, no burning clothes, not coughing because of the smoke, no tears because of the smoke, nothing.
just walking away.
my bet he was a visitor on the campus, or the gardener or anyone who just had a nap in the garden, woken up by the falling plane and the detonation.
he's apparently in better condition on this vid than most of us reading this sub.
dahlia-7321@reddit
There is further new video which happens before this video where he is seen walking from the other side of the road, crossing the road towards the crash. I really don’t know what to think now.
https://www.facebook.com/share/r/16pkTE3WsW/?mibextid=wwXIfr
dahlia-7321@reddit
Further footage of the survivor walking towards the crash side
https://www.facebook.com/share/r/1Fc8e8B1ga/?mibextid=wwXIfr
kipperzdog@reddit
Hadn't seen that video yet, that is absolutely wild just seeing him stroll away
DifferentManagement1@reddit
In that video it looks like he exits the wreckage area a split second before a giant fireball goes up.
MyDespatcherDyKabel@reddit
Which in itself is mind boggling since you see in the other videos that fireball was instantaneous upon crash
pipic_picnip@reddit
After seeing more angles of the scene, it makes sense to me. His lottery luck still lined up in perfect 10s in every department possible, but I can now understand at least how it happened. Because the blast wasn’t straight upwards, it was in the direction of the building in forward direction, while he was in opposite direction and managed to escape in time before the fire reached there. It wasn’t that he survived the blast, it was that the blast wasn’t there to begin with because it engulfed the buildings in straight line moving forward in frontal side. The angle really provides the perspective.
DifferentManagement1@reddit
I can’t get my mind around it either.
Brief-Visit-8857@reddit
God said “it isn’t your time” cuz that’s insane
chillebekk@reddit
It had much more fuel than that. It had 125k litres (ca. 33,000 gallons). Max fuel capacity is 126k. They were doing what's called "tankering", which means you bring more fuel than you need, because fuel is cheaper where you're going from than where you're going to.
pipic_picnip@reddit
On the ground? Absolutely. 100% of all people who were not on flight would be alive. In the flight? Probably not. A full tank jet would still probably cause the blast that would be responsible for deaths. But there is a chance that through some miracle the plane would have managed to skid to a halt without the fuel exploding, except not likely.
skystream434@reddit
I have an impression that landing in open field would not create situation that would ignite the jet fuel. Some injuries would happen due to impact but a fireball would not happen.
trader45nj@reddit
With a 250 ton plane loaded with fuel landing on a field, you would have landing gear and engines shearing off, maybe a wing digs in, it cartwheels. It doesn't take much to ignite the fuel and create a fireball. The chances for those on the plane would be better than going into buildings, but still not good and a fire would still be likely.
Ok-Adhesiveness-4141@reddit
Yes, that would have turned out a lot better.
Spare_Math3495@reddit
Definitely a bigger chance than crashing into a building obviously, but not necessarily.
railker@reddit
Honestly, looking at Google Earth from the view down the runway, that was about the best spot straight ahead. Another 1/4 mile further and they would've landed in a 0.5km² sprawling hospital complex, and densely packed city before and after the relatively area with those couple of buildings. Intentional or not, hard to say.
SA1996@reddit
The news that one of the engines was new adds credibility to the flaps theory.
No way would a new engine fail suddenly.
Proud_Engine_4116@reddit
I’m sorry, but no. The flaps weren’t retracted. Unless there’s actual evidence otherwise, I think it’s a known bug (51 day, 248 day or a cascade of both) that caused this crash or a fat finger error. But I think the pilots were too experienced for a fat finger or flap error.
They were dealing with a broken plane.
Some1-Somewhere@reddit
Time bugs shouldn't have affected engines still, and should have been adequately managed.
It could be some brand new bug.
Proud_Engine_4116@reddit
The FADEC gets data from the EEC. That itself is the same data (unless shown otherwise) shown to the pilots on their displays.
If the FADEC gets bad data, couldn’t that cause it to idle the engines?
Some1-Somewhere@reddit
Full Authority Digital Engine Controller. Electronic Engine Controller. Engine Control Unit.
The FADEC is the EEC is the ECU, minus some quibbling about whether the dedicated alternator, fuel valves, and other actuators count as part of the FADEC but not part of the ECU.
Individual sensors failures can degrade the FADEC operating mode, and in the worst cases, could lead to loss of thrust or shutdown.
It is hard to see it affecting both engines simultaneously unless it's something like both engines having a sensor installed wrong or covered up - and even that usually not. Also, on ETOPS aircraft (which this was), the engines are supposed to be worked on by different people to avoid the risk of errors like those taking out all engines (like Eastern 855).
Proud_Engine_4116@reddit
Yes, you’re right.
Common Core System (CCS): The CCS is a distributed computing system on the 787 that manages various aircraft functions, including engine control, through a network of modules. It utilizes fiber optic communication for efficient and reliable data transfer between modules, offering advantages like high bandwidth and immunity to interference.
The CCS likely interfaces with the FADEC system to receive engine data and send control commands. Within the CCS, Fiber Optic Translators (FOX) are used to convert signals between electrical and optical formats, enabling communication via fiber optic cables.
The 51 day bug affects the CCS/CAN on the Dreamliner.
Some1-Somewhere@reddit
The most critical commands - go/stop and thrust - are directly hardwired from the flight deck controls to the FADECs and powered by the FADECs. CCS is almost entirely for monitoring and providing some extra non - essential sensors.
Proud_Engine_4116@reddit
lol hard wired? Not on the 787.
Some1-Somewhere@reddit
This diagram pretty clearly shows a purple TLA line going from the thrust lever resolvers to the EECs. Does not go via CCS.
Same for the engine shutoff switches.
Again, there is a certification requirement that the engines continue running and being controllable despite a total loss of main aircraft power, which would take out the CCS.
Proud_Engine_4116@reddit
That’s a high level schematic that does not show the actual connections or the digital logic.
https://oat.aero/2024/04/17/boeing-787-common-core-system-ccs/
The CCS consists of GPMs (General Processing Modules)
Functions include: 1. Remote power distribution system 2. Generator Control Units (affected by 248 day bug) 3. Landing Gear Indication & Control 4. Thrust Management Function 5. Flight Management.
Some1-Somewhere@reddit
And that's an AI generated pile of slop, full of 'generally' and 'likely'. For example, the GCUs are a hardware component, shown here:
The engines have to run and be controllable with no other aircraft power - certification requirement.
So while autothrottle and other niceties may go through CCS/CCR, there are still direct channels from the resolvers to the EECs.
Proud_Engine_4116@reddit
It wasn’t AI generated and you don’t know what you’re talking about. Stop treating the Dreamliner like a legacy plane. It’s very different to what we are all used to.
Just because I write well, does not mean I’m an AI or I am using AI.
Also, if you don’t understand how cyber-physical systems work, I suggest you start here:
https://www.ioactive.com/reverse-engineers-perspective-on-the-boeing-787-51-days-airworthiness-directive/
What you need to understand is this: the FADEC relies on sensors to correctly manage the engines. If the FADEC gets garbage data, you will get garbage output.
Garbage In = Garbage Out.
Some1-Somewhere@reddit
I was suggesting oat.aero was using AI, not you.
Again, though, they claim that the GCUs are running virtualised. GCUs certainly contain software; no doubt about that. But that does not mean that they are virtualised. The have hardware that supplies excitation current, measures phase sequence, voltage, current, frequency and the like. A VM simply can't do that.
They list a reference which does refer to the GCUs but says nothing about them being virtualised.
High-level, yes. But I think it quite explicitly shows that some commands go via CCS and some do not. Physical thrust lever position certainly seems to be a 'not via CCS'.
Overrides are a reasonable argument. You have not previously mentioned them.
If the TCM commands the thrust levers to be brought back to idle, then that certainly commands the engines back to idle unless the crew immediately notices and firewalls the throttles.
If the TCM directly tells the FADEC that the engines should be at idle, but the thrust levers are forward, then we are dependent on FADEC programming and bugs to see which it listens to. I would expect Boeing to follow the crew input (i.e. thrust lever angle) but have no evidence. Airbus appears to follow the greater of the two commands; hence alpha floor protection can operate even with the thrust levers at idle.
If the CCR and therefore TCM is dead and unpowered, then there is surely nothing to send an override command.
Proud_Engine_4116@reddit
Fair enough about your point. However these aren’t VMs. These are physical systems. The system is designed for reliability and redundancy but ultimately everything literally is computer.
We can speculate as much as we want, but as someone who works with these types of machines and systems and having also demonstrated (in my professional) life how easy it is to cause malfunctions in these types of systems, my current working theory makes sense to me.
I hope I’m wrong.
stuntin102@reddit
i haven’t seen anyone able to answer what happens to the FADEC (or EEC) if there is total electrical failure. does it default to idle? does it maintain the last thrust setting? the throttle levers are not mechanically connected to the engines. there is an electronic system in-between.
Some1-Somewhere@reddit
The throttle lever sensors are directly electrically connected to the FADEC and powered from the FADEC. There are no other systems in between.
If both the dedicated FADEC alternator and the aircraft power fail, then yes, the engine will shut down. The odds of that happening to both engines at once is astronomical.
Byzaboo_565@reddit
I’m not saying this is what happened, but experienced pilots can and do make mistakes.
Yeti 691 was brought down by a pilot with 22,000 flight hours (over 3,000 on ATR-72) who grabbed the wrong lever and feathered the props when he meant to adjust the flaps, despite levers being shaped differently and requiring different movements to actuate them
Proud_Engine_4116@reddit
Yes that can happen. The flaps weren’t retracted. The engines went into idle.
railker@reddit
Well the 248-day bug has been resolved, a subsequent AD to the one that called it out has been issued and the software update and full compliance was due years ago.
That and the whole concept of anyone leaving their aircraft powered on for that long, either 51 days or 8 fucking months, seems nuts to me but I don't know the real-world operational statistics. Both the 51-day and 248-day glitches I believe were only encountered by Boeing leaving it on that long just to see what would happen, because at no time in 11 years had anyone left their plane on that long.
Proud_Engine_4116@reddit
If you do a deep dive into the Dreamliner and is Electrical system you’ll note that there are edge cases in the electrical system that could cause “Simultaneous FADEC Protect Idle” due to DC faults.
As for your assertion that “no one has left their plane on that long”, well they better not have because those are current and active Airworthiness Directives from the FAA.
Some1-Somewhere@reddit
Ever hear of a bathtub curve?
One engine being new does not explain both engines failing within seconds when we have basically no known independent dual engine failures in a twinjet, like, ever.
Tasty-Explanation503@reddit
The odds of both failing at the same time must be 1 in billions surely?
Some1-Somewhere@reddit
Independently, yup.
AtomR@reddit
How tf are people like you so confidently wrong?
AntoniaFauci@reddit
What are the fine timeline details of RAT deployment? (Assume it must take a certain number of seconds to be invoked, to drop into place, spool up, start generating(
Some1-Somewhere@reddit
I have heard 6 seconds to hydraulics available, 10 seconds to electrics available, absolute maximum. Usually in the 2-3 seconds range for both though.
Virtually everything electric that runs on the RAT runs off battery in the interim so it shouldn't be critical.
AntoniaFauci@reddit
Good info
indiataxi-cab@reddit
The recent Air India Flight 171 tragedy in Ahmedabad has sparked a critical conversation about aviation safety in India. As an investigative journalist, I've spent time analyzing the systemic issues that may have contributed to this and other incidents.
Our latest article on Newspatron breaks down:
https://newspatron.com/india-aviation-safety/
The immediate circumstances of the Ahmedabad crash and its profound impact.
Air India's turbulent transformation and recurring technical issues.
Boeing's controversial practices and its legacy of compromise.
Critical gaps in India's aviation safety framework, including regulatory independence, optional safety features, and pilot fatigue.
Concrete recommendations for strengthening oversight and ensuring safer skies.
This isn't just about one airline or one incident; it's about the broader state of #indiaaviationsafety as the sector rapidly expands. We believe transparency and proactive reforms are essential.
I invite you to read the full article and share your thoughts, experiences, and questions. Let's discuss what needs to change to ensure the safety of every passenger.
Read the full article here: https://newspatron.com/india-aviation-safety/
What are your thoughts on flight safety standards in India? Have you experienced any issues?
aviation-ModTeam@reddit
Your post has been removed for breaking the r/aviation rules.
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ebs757@reddit
Was really incredible how many social media sleuths jumped onto the raised/ no flaps theory almost immediately. You can really tell who has watched a 787 take off and who hasn't..
Brief-Visit-8857@reddit
cough cough Captain steeeeve
OrionAldebaran@reddit
I cancelled my sub after he deleted his video about the AA crash because his company asked him to do so. Also, I noticed he is leaning more into a sensationalist coverage like Mentour Pilot. Once they start using ridiculous facial expressions on their thumbnails and introduce sponsors, you usually know it’s over. Blancolirio is the channel to go to, precise, trustworthy, professional & not incentivized by any sponsors or to make money. Trust the guy 100%.
MelTheTransceiver@reddit
I unsubscribed from Mentor Pilot after he decided to start dubbing other languages with AI instead of just using actual people to voice them. Big channels like his have the resources to have a higher level of quality, but often just end up doing it the quick and easy way to save a buck.
Illustrious_Crab1060@reddit
doesn't YouTube automatically dub using AI now?
MelTheTransceiver@reddit
No. It’s a toggle and that’s not what he’s doing either.
kussian@reddit
Why do you watch his videos not in English? The guy literally speaks English. I see no reason to switch to another language because you want to listen to the guy and not other person.
NigroqueSimillima@reddit
lmao did you not unsubscribe because of the auto generated subtitles?
twopointsisatrend@reddit
Juan Brown has a great YT channel dedicated to aircraft accidents.
RimRunningRagged@reddit
The AI usage by aviation Youtubers is getting ridiculous. The YT channel for the Mayday series has gotten absurd with the horrible AI-generated art lately -- like what in the hell is this plane supposed to be?
chak2005@reddit
the Mayday series is scummy in my view. They slightly alter episode timings or cut and swap out old episodes and repost like new with new graphic thumbnails all in order to generate add revenue for clicks while not actually putting out new content. I view their channel as just gaming the algorithm at this point using 15 year old TV shows.
Melinow@reddit
His Betterhelp sponsors rub me the wrong way, I get that YouTubers want to make a living, but it’s very common knowledge that BH is a scam company, made worse by the fact that it preys on people’s mental health of all things. The lord and ladies land buying company is also a scam, but at least with that the worst that happens is you’re out $50.
elastic_woodpecker@reddit
Nobody is perfect, including Blancolirio. He sometimes makes mistakes by being to quick and not research enough and he has a Patreon that he advertises with every crash video.
kussian@reddit
Nobody is perfect is basically Everybody sucks. Boring 😐
OrionAldebaran@reddit
Yeah, you’re right. Best thing is always to rely on the final report. He’s also made mistakes as you said, but has been honest about it and clarified it.
ebs757@reddit
All of these guys don't get it. They are 2-3 hours behind the curve when they post these initial crash videos.
bonoboboy@reddit
And Steeeeeeeeeeeeeeeeeeve just used what blancolirio said, almost word-for-word.
Busy_Comedian_8165@reddit
His two Air India video's have gotten 17 million views. Two days work made him almost $150,000. It pays to be a sellout
ronreadingpa@reddit
Juan Brown (Blancolirio channel) is slipping too sadly. Rushing videos out. Overly reliant on Youtube / Patreon income. Also, he shows a sponsor name on many of his videos. It's basically a business versus a hobby. Big change from his early days when he covered the Oroville Dam. Seem most every Youtuber who becomes popular falls into the greed trap. It's so predictable.
Don't get me wrong, Juan is still the best of the better-known aviation channels, but concerning. Hoping he stays true to his love of aviation versus succumbing to the love of money. Still watch his videos and learn a lot.
Swimming_Way_7372@reddit
Too much money in not being the first to get the videos out. If there is money involved, there is always the high possibility that one will slowly creep in the direction of the money vs accuracy.
Cumulonimbus1991@reddit
You can watch all these channels without subscribing to any of them. I would only subscribe to a channel who I think deserves and needs the money, and most of these pilots have a pretty decent paycheck anyway.
UnluckyStartingStats@reddit
Horrible account. He jumped ahead blaming the pilot then next video said we can’t be jumping to any conclusions while barely mentioning the RAT
GatotSubroto@reddit
He argued that one of the pilot flying retracted the flaps instead of the gear when the pilot monitoring went “positive rate, gear up”, but I wonder if the 787 would even allow the pilot to do that at the airspeed + altitude combination they were at.
Brief-Visit-8857@reddit
Right? And he also ignored the fact that the gear lever and flap levers are nowhere near each other. Also for a pilot to do that would be such a rookie mistake, a mistake that pilots flying 787s should not make
GatotSubroto@reddit
Yup, and the handles of the lever have different shapes and require different movement to switch on/off. It’s almost like accidentally putting your car in reverse when your intention was to turn on the blinker.
SkiTour88@reddit
On my Sprinter van, bumping the stalk on the left side of the steering wheel upwards signals to the right, bumping the nearly identical stalk on the right side of the steering wheel upwards shifts it into reverse.
The ECU won’t let you shift into reverse while moving…or at least it’s not supposed to.
I’m not a pilot, I have no idea what caused the crash. I just hope Boeing’s cockpit ergonomics team is better than Mercedes.
railker@reddit
And yet it happens, silly human errors you wouldn't think possible but you sit there and read the final report like, 'No. Yeah. They just. Alright, well fuck.'
The Yeti Air ATR I bring up -- bringing two round throttle levers back to feather past a gate versus bringing your single flap-shaped handle down. They're beside each other but they're different sizes, shapes, and require different motions.
On top of that they subsequently deployed the flaps after noticing they weren't deployed and never wondered what it was they deployed a minute ago if it wasn't the flaps.
Or shutting down the wrong engines, multiple instances of that. Or the pilots of Helios 522 who'd probably still be alive along with all their passengers if they'd ACTUALLY checked that the pressurization knob was set to Auto the 3 times it was called out on checklists before they took off. But they'd probably never seen it in any other position and were so used to glancing up and going, 'Yup knob's there.'
Some1-Somewhere@reddit
Unfortunately, even experienced people make rookie mistakes quite frequently, and this is the kind of one-in-a-million crash where such rookie mistakes can't be ruled out.
But there's enough evidence that it really doesn't look like a flap issue.
MelTheTransceiver@reddit
To be honest even if the flaps were retracted, with the weather and runway to spare they had, I wouldn't be surprised if the 787 would've been able to lift off relatively unscathed. It couldn't be that.
AWildDragon@reddit
Heat makes things worse. The air is less dense providing less lift at a given velocity so you need to compensate with more flaps and speed.
It’s a big reason why places like Phoenix are starting to see cancelled flights in the summer.
MortonRalph@reddit
The first thing I thought about when I saw this plane go down was density altitude, while I realized that it likely wasn't a contributing factor.
I live at 7,000', the same altitude as our local airport that sees daily commercial, private and military aircraft, many of the latter using it for training purposes for just this reason. It's in the mid 80Fs today, so everyone will be making their calculations in order to be able to complete that takeoff roll before running out of runway...
PoopHatMcFadden@reddit
I agree with you that we cannot rule out pilot error. However, I think it's grossly unfair (even unethical) for someone with the authority and social media reach that he has to speculate pilot error. The investigation is so far from being completed, and there are no answers yet. As someone who has as much experience in the industry as he does, he should honestly know better.
beiherhund@reddit
It has happened before, just not in 787s. How many rookie mistakes have been performed by experienced captains with thousands of flight hours and have lead to accidents?
That someone shouldn't make a mistake doesn't mean it won't happen, this should be obvious to everyone.
beiherhund@reddit
Beyond indicators on the PFD I haven't heard anyone say there is. Even if there was an alert, at that altitude you might not have a lot of time to correct it by the time you figure out what is wrong.
Not saying this theory is well-founded, only that the initial argument doesn't seem to be a bad one and it shouldn't necessarily reflect poorly on him if it's a plausible scenario and he didn't claim that is what happened or dismiss other scenarios he couldn't disprove.
phluidity@reddit
Except even if the flaps/gear scenario was possible, a cursory look at 787 specs shows that it is capable of taking off/climbing with flaps 0 under TOGA thrust. Obviously not ideal, but suddenly taking out flaps wouldn't cause what we saw.
It is one thing for people on Reddit to speculate about things like that, but an expert with his following should be expected to know better.
beiherhund@reddit
Out of interest is there any documentation for this you can share? I know some flightsim guy showed it in MSFS but that isn't exactly a great source.
Captain Steeeeeve wasn't the only one to make this mistake if so, Mentour Pilot and the guest pilot he had on both thought no flaps could cause this (both are also Boeing pilots). Granted the plane didn't necessarily take-off with TOGA but given it was a long haul flight in hot weather I imagine the Flex Temp adjusted thrust would be not far off TOGA so if you're right then I think that would disprove that theory.
phluidity@reddit
I believe it is in the flight manual somewhere. I'm not surprised Mentur especially thought that, since his Spanair video was a popular one. Certainly older planes like the 737 can't take off with no flaps, but I think both the most recent Airbus and Boeing planes are designed to be capable, but still outside operating parameters.
ebs757@reddit
Not even just that but the video of the RAT and audio were already out there. To desperately jump onto YouTube so quickly just to get some revenue is unconscionable for a guy making 350k+ already.
ratatouille400@reddit
What is the deal with this Captain Steeve? Never heard of him before and on his videos for this crash, YouTube comments are like girls in bikini photos saying you brighten my day, people saying I wish you were my dad, some stuff against haters, so much positivity is rare!! Is this genuine or are these bots?
Lost-Inevitable42@reddit
The insanity of "captain steeeve" - He was going on all sorts of indian television shows repeating the same unfounded inexcusable bullshit. It was just bizarre because there was no information to base that claim on. Not being able to see the flaps doesn't mean they weren't set/retracted. It'd be like seeing a car crash video and assuming that someone hit the gas instead of the brake on your first insight.
These weren't rookie pilots. I don't think he makes that same early conclusion if it was American Airlines.
This crash also goes to show how little pilots know about the actual airplanes -- and it makes them shitty investigators. So many of the commenting pilots had never flown the 787 and were drawing conclusions from the 737 cockpit.
I'm sure he made some good money on his videos/appearances/updates.
The glazers saying how it's good that he updated his theory ignore the conclusion that he drew from the limited information. He didn't frame it as one possibility. He framed it as the likely scenario based on his expertise and experience.
It's why we get articles like https://www.yahoo.com/news/co-pilot-error-suspected-air-151829483.html
It's awesome to speculate early on. It's a cool chance to learn and show one's expertise. But that shitty theory really shows how little he understands - or maybe how 'deep' into boeing's system he is. We are no longer at the point where their word can be taken at face value.
LantaExile@reddit
It never seemed very plausible to me - I have a PPL. Planes don't suddenly crash because you set the flaps a bit wrong.
alcohollu_akbar@reddit
I have no qualifications other than a functional brain (sometimes) but it was ridiculous that they thought they could tell the position of the flaps from that grainy footage.
Low-Computer8293@reddit
The longer this drags on, the more I'm wondering if this is an Air India problem. It seems to me that if India could point their finger somewhere else, something would be leaked by now. Thoughts?
Piranha2004@reddit
Investigations take time and are quite complex. I rather them take time than make assumptions or statements without proper analysis
PatentedSheep@reddit
Could be years until the investigation report is released. China still hasn’t released report from CES 5735 after over 3 years
DifferentManagement1@reddit
Because the cause embarrasses them
fugutoxin@reddit
Not really comparable, in my opinion. The Chinese case involves a totalitarian regime wanting to keep the lid on an unhinged pilot deliberately crashing a passenger aircraft. Would you expect anything less of the CCP?
Nice_Classroom_6459@reddit
Given how quick Boeing was to blame Ethiopian/the Pilots, I would say that their silence on the matter is more telling than Air India's.
Brief-Visit-8857@reddit
That’s because Lion Air crashed first and then Ethiopian crashed later, and both the crashes were eerily similar. So they tried to save face by blaming the Ethiopian pilots. They were silent after the first MAX crash, too.
Brief-Visit-8857@reddit
Or.. you know, they haven’t decoded the EAFRs and this crash is more complicated than just pinning the blame on one party. Maybe there were new holes in the Swiss cheese model that we have never encountered before.
Creepy-Egg-8874@reddit
True, everyday I find myself opening and searching for new info multiple times. I feel the families of people who lost their lives deserve answers and it should be a priority.
Brief-Visit-8857@reddit
So, I found a comment that says the FSOV valves are ball valves, not spring loaded. Here’s the comment, take it with a grain of salt (again):
Overall, I too also think this was an aircraft electrical system failure of some sort (unknown cause) that had unforeseen consequences that triggered and affected engine thrust and/or somehow triggered the same dual engine shutdown as in the 2019 incident you mentioned. The fact that the RAT deployed seemingly upon the weight off wheels (it cannot deploy until the aircraft is airborne) triggered some kind of fault that both EEC's interpreted the same way and either metered the engines to low power or shut them down completely. I tend to think they were metered down because the pilot did not indicate he lost both engines, just that he lost thrust power (I assume, as I haven't heard the radio call). What was the system-wide electrical failure to begin with if that's the case? This is a mystery. The 787 is the most complicated "all electric" (and really the only one) aircraft out there. With millions of line of code, this may be another 2-3-year investigation. I just wish they would update us with at least what they know...
Nice_Classroom_6459@reddit
In fairness, this kind of automation failure is exactly what skeptics/hawks warned about when introducing a ton of advanced technology in one shot in the 787. Not really any "hope" in this situation given the lives lost but where we would usually be dubious of an engineering failure I think this helps explain why so many are looking at it.
Brief-Visit-8857@reddit
Do note that the “Mayday mayday… losing thrust” call was misinformation, the pilot only declared mayday.
allielhoop@reddit
Was the exact text of the mayday call ever actually clarified? Ans what language was it in?
railker@reddit
I haven't seen anything as of yet, the 'official statement' made no quotes and only said a Mayday came over the radio and then contact was lost. Then one of the journalists who initially reported the 'full call' later issued a retraction stating, 'ATC source say this is wrong, in 32 seconds the commander had, all he could convey was “Mayday”'.
We won't know for sure until we get the transcript, likely in the Preliminary report.
KnavesMaster@reddit
Regarding the ADs.
Even if complied with the thing that worries me is the increased Exposure Time of potential faults to occur. The safety case may include as an example an average sortie time of let’s say 11 hours of flight, and the fault tree analysis uses this as the number to calculate the probability of failures according to known reliability figures. So any extension to this invalidates the safety numbers.
Let’s say it was assumed an aircraft is kept powered for a week during the design process, a 51 day power cycle to avoid Common Data Network (CDN) timeouts on the Common Core System (CCS) is still 7 times longer than that!
Not only is likelihood of failure increased but as a system is powered up it does a Power-Up Built In Test (PBIT) to assess functionality, if this is not run it could lead to latent failures that are only found following a power-cycle. If this happens mid flight, for example a power transfer, it is not inconceivable that databuses or processing resources could be allocated on subsequent start-up that were inoperable.
Not saying this is the cause, just an observation on the ADs.
One would hope complex systems were power-cycled and performing cold starts regularly/routinely to ensure faults are found in safe conditions on the ground.
railker@reddit
Are you guys feeding ADs into ChatGPT now? The fuck 😂
How does any flight's length have anything to do with specific errors coming up at precise time periods? It doesn't happen at 50 days or 52 days, AND in this case of the 51-day 'bug' only presents a problem in the remote possibility that an airplane's that's been powered for that long also has a CDN switch failure. Nowhere do I see that this was discovered in service, it's noted that it was discovered by Boeing's Analysis and Testing team as a potential issue that's described as 'extremely remote' and 'highly unlikely'.
There's a reason the fix is 'turn your plane off and back on again', your exposure time doesn't even enter into the equation for a fixed-time fault.
Aircraft are often left on overnights, but for two months? And regardless, compliance with the AD ensures there's a maintenance program task within calendar time limits to power cycle the aircraft as required for compliance, until like the 248-day issue potentially dropping the GCUs, there's a permanent fix implemented.
KnavesMaster@reddit
Completely agree with everything you say: the simpler version of my point is not related to the fixed time fault but any other errors that could be present that aren’t found during regular built in test but only during power up.
I do believe however, that CDN Switch failure was a potential outcome of the stale data monitor failing after 51 days not a pre-requisite.
Thanks for your insight, humans make errors too not just ChatGPT but just because you disagree with a point doesn’t make it all incorrect. Your first-hand info adds to the understanding 👍
railker@reddit
Sorry my dude! Always happy to be proven wrong, AI was an assumption based on some oddities and on the heels of a week of so many people wanting to be 'part of the conversation' without the experience to back it up and so having a program write up an accident cause for them. And then worse than that, like the false 'preliminary reports' being shuffled around, the general public doesn't know any better and treats it as fact. 😅
That is my understanding of the SB attached to that AD, at least. Not that it can't happen without the switch failure, but the combination of those two would let potentially bad data to the aircraft systems.
"Undetected/unannunciated loss of Common Data Network (CDN) message age validation, combined with a CDN switch failure, could lead to erroneous flight critical data being routed and displayed as valid data. [...] A single network switch failure, combined with 51 days of continuous airplane electrical power application, has been identified to be a potential scenario in which critical data may be adversely affected. While this scenario is highly unlikely in the fleet, Boeing has identified airplane power cycling requirements to eliminate the possibility of these two items happening concurrently."
Legalese is already had enough to understand, definitely don't need AI mucking it up even more. Fuck studying for those exams again. 😁 And obviously though both of these appear to be described as having never seen in service and only discovered by Boeing's team, cases like ANA's discovery of TCMA activating on landing means there's always the potential for some undiscovered corner case to be the case of this crash still. We don't know what we don't know.
Cheers for being chill. 🧡
KnavesMaster@reddit
Thanks for your clear and informative response.
The SB is certainly better worded than the AD, and I agree with your statements.
Undetected erroneous is always the danger, especially if you have redundant systems that are not utilised until they are needed, or rely solely on power up self test!
Interestingly it seems that all the discussed ADs are being incorrectly associated with the generic “Electrical System” when in fact it’s several safety-critical electronic systems also. They seem to only point to some existing examples of edge case failures that have been identified, ameliorated with crew/maintainer advice, and highly unlikely. The GCU one especially.
Appreciate the conversation.
railker@reddit
And as always, everything in ADs err on the extremities of caution -- the reset timeline on the initial 248-day GCU issue was to reset power every 120 days less than half the time it would ever take for this problem to occur. You could miss doing it once and still get it again before it happens. Ignoring human error and someone just not doing it at all.
The common problems have solid redundancies. Edge case failures are rare, but they ARE the ones to be concerned about. ANA found one after all, the second MCAS crash (I think was the one with the incorrectly calibrated AoA sensor that wasn't tested on install?), and probably many more.
Cheers, happy Monday!
Brief-Visit-8857@reddit
Why would someone even leave an airplane on for 51 days continuously? Have you thought about that? I don’t think they would do that.
KnavesMaster@reddit
They do that’s how the problem was discovered. Long Haul aircraft can be left powered during crew switchovers and overnight on GPUs whilst maintainers and cleaners service ir.
Blythyvxr@reddit
Oh ffs, still not auto sorted by new…
allielhoop@reddit
Very frustrating
Glittering-Spite234@reddit
Why are these threads getting opened again just to spout wild theories based on hearsay and no actual evidence? Just freaking wait for the investigation to finish and then open a thread to talk about that.
allielhoop@reddit
Freedom of speech!
JustHarry49@reddit
The amount of stuff I learn from the random theories people present is worth wading through all the hearsay. Eventually I will read the official reports and know the answers but let’s not pretend all this conversation and speculation is a waste of time because it’s not.
BritniPepper@reddit
Spot on. I love to see people explain - with sources - why a particular theory isn’t correct. All sorts of fascinating details emerge.
This type has been flying for fifteen years with over a thousand built. This is the first crash. Of course people are going to be concerned.
Ok-Adhesiveness-4141@reddit
The investigation will take several months and there is NO guarantee that they will reveal the truth.
The stakes are that high, If it turns out that Air-India's poor maintenance is at fault then that will lead to the company going bust. Boeing as we all know will never let anything negative about its planes come out.
Glittering-Spite234@reddit
Lol, what a load of bull.
We do know what has happened in the past with Boeing's airplanes and plenty of negative has been said about them.
We do know the cause of previous plane accidents because the people investigating them are professionals with access to all the information that chad2323 on reddit does not have.
pipic_picnip@reddit
That is why they are megathreads for people to discuss. It would not be fair not to provide any space for people for people to talk about what can only be described as the worst aviation disaster of this decade, but there aren’t enough “official” updates to warrant making new posts. They did say it’s the last one, so likely after this they might switch to posting individual updates that are relevant.
jellystones@reddit
When there is new information, it will appear in the new megathread rather than being buried in an old one
DontLookUp21@reddit
This.
jellystones@reddit
When there is new information, it will appear in the new megathread rather than being buried in an old one
twarr1@reddit
By the time the official reports come out nobody will be interested. There will be a new hot topic.
bfly1800@reddit
Yup. I’m looking forward to discussing this one once the official reports come out. I’ve seen so many theories but we have pretty limited evidence to go off at this stage so it’s all just farming for internet points with wanton speculation at this stage.
entrep@reddit
shinealittlelove@reddit
I wonder how many times TCMA has genuinely activated as intended on a 787? I can't see any literature to suggest it ever has been (but that's not to say it hasn't).
allielhoop@reddit
I read that in the 2019 incident actually TCMA activated as intended
Emotional_Two_8059@reddit
Boeing allegedly didn’t really like the feature but mitigating uncommanded high thrust on ground was mandated by the FAA
allielhoop@reddit
The same FAA who caused the recent DCA incident through their negligence.
Heiter-Sama@reddit
Not to mention it has caused a double engine failure in 2019 that was never resolved...
Emotional_Two_8059@reddit
Replying to Brief-Visit-8857...That’s what the thrust contour is there for… to account for the slow response of the engine. But I have a modified scenario:
entrep@reddit
Yes, this is more plausible.
Emotional_Two_8059@reddit
But another Redditor suggested that the TCMA might also use the agreed value between the two channels… so what I say can be BS, depending on the integration of the TCMA in the FADEC
entrep@reddit
Yes, that part is a bit unclear given public sources.
Chen932000@reddit
If the levers read idle and that idle was used as “good” wouldnt the engines also be using that idle as “good” and drive the power to idle regardless of TCMA? If the engines can detect the throttles being as idle is erroneous it will ignore them (maintaining power) but TCMA will also ignore them.
Emotional_Two_8059@reddit
No, not clear that TCMA will ignore them. I guess for safety reasons, each throttle sensor is only wired to one FADEC channel. Erroneous throttle position sensors are handled through the dual-channel operation of the FADEC!
It’s unclear to me if the TCMA logic ever communicates with the rest of the FADEC logic and gets informed of throttle position mismatch between channels.
If it was developed separately it might only have access to the single throttle signal.
According to the patented design at least, each TCMA can trigger a relay to shut down the engine independently.
Chen932000@reddit
The TCMA almost certainly uses the same accommodation for throttle position as the rest of the FADEC (the TCMA logic looks to reside in the FADEC). If it only used local unaccommodated signals it would literally be one failure away from activating which likely doesn’t meet the appropriate safety rates. But more to the point we’d have FAR more erroneous activations of TCMA on single enginesthat I can’t find any actual reports of.
Emotional_Two_8059@reddit
It does reside physically in the FADEC, but at least I have no information on the level of integration with the rest of the FADEC. If the FADEC was already developed and then TCMA was added as a functionality on top, as was needed by Boeing to satisfy FAA regulations, then maybe it’s more prone to faulty inputs or bugs in its code.
Otherwise, IF TCMA was triggered (we have no clue yet, to be fair), it must be an unknown bug or conceptual mistake in its operation.
Chen932000@reddit
I mean you’re right in everything you said here. I also have no idea if it’s fully incorporated or not but it seems like it would be even more work to incorporate it separately into the FADEC. Even with partioned software (which I also don’t know if they use) both thrust control and TCMA would almost certainly be in the DAL A partition.
entrep@reddit
Probably, but EEC would start a slow spool down, TCMA would just cut the fuel after ~0.3s.
Emotional_Two_8059@reddit
This is what the thrust contour is for in the TCMA, to account for the spool down.
Chen932000@reddit
I mean a step change to 0 throttle (due to signal malfunction) is not that much faster than a slam of the throttle to idle. There needs to be some leeway in this deceleration profile or TCMA would shut engines down constantly.
Srihari_stan@reddit
On the 787 (or any modern jetliner), the throttle lever sensor is not a single point of failure.
Firstly, there is more than one sensor. So even if one sensor fails, the system still takes the relevant data from other sensors and sends the information to fly by wire.
Secondly, even if you assume all sensors fail, it still locks the throttle at the last setting (presumably at TOGA in this case), so it wouldn’t just keep the engines at idle.
entrep@reddit
Yes, for like 0.3 seconds until the dynamic contour drops below the current actual engine power.
onmyway4k@reddit
Can you Eli5 this?
entrep@reddit
https://i.imgur.com/CFZOq1v.png
Dynamic contour is the "allowed power" / purple line. It stays above the throttle signal (red). When the signal drops to 0 the dynamic contour starts dropping and at a certain point it is below the thrust set. This trips the TCMA given weight on wheels.
Some1-Somewhere@reddit
That is where the throttle lever sensor position is known and valid. If it becomes invalid, I would expect TCMA to go out the window and the engine operates at last valid thrust command.
In automation we regularly use 4-20mA sensors where 0mA is an invalid input and implies sensor failure. A disconnected sensor should be distinguishable from a zero thrust command.
Given most things in the world of engines assume full power is the safest option (including, apparently, snapped mechanical throttle cables), I would not be surprised to find that 0V is TOGA and full output is ground idle or reverse.
In addition, note that there are two separate throttle lever angle resolvers power lever, and two throttle levers. Are you suggesting that all four failed simultaneously and in a way that could not be detected as a fault?
Emotional_Two_8059@reddit
Issue is that we don’t know how well TCMA logic is integrated with the rest of the FADEC. Each FADEC channel only connects to one throttle sensor.
Hopefully they check the input value itself properly, and then any mismatch between the two resolvers is handled by the channel disagreement.
But maybe TCMA is independent of these checks and uses the single input. Or even worse they don’t even perform the checks of the single throttle input correctly. I hope they didn’t just have (if throttle < X Volt) as the TCMA idle condition and any short triggers it….
entrep@reddit
Both throttle sensors live on the same lever and share the same four-wire harness. If that harness shorts or breaks, both sensors drop to 0 V together.
RealPutin@reddit
Don't know about the 787, but on the planes I know the details of, all throttle sensors tanking to 0V is detected as a fault that keeps the last setting, not a 0 input
Emotional_Two_8059@reddit
Yes of course. Voltage slopes have different monotonicity and slope for that reason
Emotional_Two_8059@reddit
SENSORS HAVE DIFFERENT VOLTAGE SLOPE! They’re not that dumb. If both sensors fall to 0V, the computer will know the input is implausible
onmyway4k@reddit
Can you Eli5 this?
Brief-Visit-8857@reddit
https://www.reddit.com/r/aviation/s/wRvGDbBNnh
NorthernEwan@reddit
I see the logic, but TCMA can (or should) only activate with Weight on Wheels sensors activated… ie, it’s on the ground? But I know Boeing offered a bulletin to make this less easy to activate as there was a case where a plane rolled back to idle on landing.
Emotional_Two_8059@reddit
Could have activated just before rotating. Still on ground
NigroqueSimillima@reddit
AI-171’s GEnx engines aren’t subject to the bulletin that showed a TCMA dual cut. Please stop repeating this.
Emotional_Two_8059@reddit
Their logic is likely very similar.
Brief-Visit-8857@reddit
This explains everything we see. I’ve seen the same theory passed around the one of the pilots selected reverse thrust to reject the takeoff (encountered an anomaly), but the other pilot pushes it back to full thrust but by that time TCMA kicks in and shuts down both the engines and they’ve already lifted off.
Newmania_eigo_ga@reddit
787 pilot here and this seems unlikely. Spoilers automatically deploy in a rejected takeoff, sensed by being above 85 knots and thrust levers being at idle or reverse. Secondly auto brakes would have activated RTO which is a very sudden deceleration. If that happened anywhere near V1 you would not be able to cancel the reject and get it airborne before running out of pavement.
Tiny-Plum2713@reddit
Is there a maximum speed or distance for the automation to kick in?
Newmania_eigo_ga@reddit
No maximum speed, only minimum of 85kts for both spoilers and auto brakes
SelectionForsaken466@reddit
If the thrust reversers were engaged, wouldn't that be visible on one of the videos?
Brief-Visit-8857@reddit
If you look at the video, there’s a shack that blocks the exact moment where the reverse would have tried to deploy, so you wouldn’t see it on the video anyways. https://youtu.be/1BdVzYXwVwI?si=Kj_YlM8yhBGFLflj
SelectionForsaken466@reddit
very true, but would the dust cloud be bigger than the one produced by the wing tip vortices seen in the video?
Emotional_Two_8059@reddit
Even car throttle pedals have two separate sensors with different voltage slopes exactly for this reason. The computer then checks if these two values correspond to the same throttle position. If not, the input is deemed implausible/untrusted.
Tiny-Plum2713@reddit
Famously MCAS relied on one AoA sensor. Not saying it's the case here.
Emotional_Two_8059@reddit
Yes, good point, the stupidity there was quite high. But it all stemmed from the fact that MCAS was somehow not deemed safety relevant or so… Flight controller and FADEC must be developed to very high safety standards. There was another comment somewhere, that each EEC channel gets input from one resolver.
Heiter-Sama@reddit
This theory is so much more plausible than any other possible scenario. The chances of this being relates to TCMA are very high.
And TCMA has caused a double engine failure on a 787 in 2019.
https://simpleflying.com/ana-dual-engine-failure-on-landing/
NobodyTellPoeDameron@reddit
This is the theory I would investigate first. It's a known flaw that has caused dual engine shutdown previously so it seems like a good place to start.
RealPutin@reddit
I don't know all the TCMA parameters, but would that error sequence not involve rejected takeoff procedures autodeploying instead of/together with the cutoff?
entrep@reddit
What if the TCMA tripped just before rotating?
kipperzdog@reddit
I've read elsewhere that the throttle sensors are per an engine though so that would mean both sensors failed at exactly the same time. My understanding is TCMA is isolated to only look at the sensors for an individual engine so if one side fails, the other isn't impacted.
Absolutely wild if that is what happened.
entrep@reddit
As I understand it: each engine does have its own throttle sensor, but both sensors share the same lever and wiring bundle for the first few feet. If that shared section shorts or breaks, both sensors drop to idle at the same moment. Each engine’s TCMA then shuts its own fuel valve - so one common wiring fault can kill both engines even though the computers don’t talk to each other.
entrep@reddit
Came to think about this incident when tea spill caused problems: https://www.businessinsider.com/airbus-a350-engine-shutdowns-spill-cockpit-2020-1
onmyway4k@reddit
Just 2 days ago i was contemplating that the problem must have manifested during the rotate, as they where, until then, seemingly in good conditions. Would be insane if they all got killed for a chai tee in the cockpit.
New_Visual1245@reddit
What if a technician knowingly connected both throttle lever sensors to a single functioning power bus because the second one was faulty or unavailable? That would be blatant violation of protocol but would also explain how a failure of a bus (which is no longer redundant) would engage TCMA and cut fuel to both engines.
Independent-Mix-5796@reddit
Should be impossible. The FAA 787 MEL requires at least one functioning channel per each Primary Power Distribution panel. (i.e. There are 8 channels total and min. 4 required for dispatch, provided no two inop. channels go through the same panel.)
Brief-Visit-8857@reddit
Aren’t there 4 buses on the 787 for this exact reason?
kipperzdog@reddit
I don't know enough to know if it's even possible to do that but it certainly sounds plausible.
BUNNIES_ARE_FOOD@reddit
Wild. If this is true I wonder if there is a line item buried in a risk assessment somewhere with this low probability high severity event. "sorry engineering, this risk would be too expensive to fix, so we just have to accept it and move on. Sincerely, the executive team"
Brief-Visit-8857@reddit
The odds of this happening were probably low that they didn’t pay enough attention to it. Now it seems like it has happened and Boeing is about to get a reality check.
nortoncruz@reddit
I’d abort it even after V1… insane to try to fly like this
Objective-Muffin6842@reddit
The amount of people in this sub that are certain they know what went wrong is fucking insane
---midnight_rain---@reddit
its not certainty - its technical speculation based on circumstantial evidence at this point:
Some1-Somewhere@reddit
Third entry is wrong: the engine FADECs have their own power source and are directly connected to the thrust levers with no reliance on aircraft power except during starting.
You lose autothrottle but the thrust should certainly stay as set during an electrical failure.
---midnight_rain---@reddit
that is incorrect for the 787 - it has several weak points in the elec systems where several faults can result in a complete electrical system casdade/ shut down and the RAT deployed - the dual PMAs in each engine will disconnect and there is a 60s time gap for engine control untul the APU spins up
Some1-Somewhere@reddit
Do you have a source on that? Because it seems like that would be an automatic grounding.
---midnight_rain---@reddit
Boeing 777 Complete Electrical System Failure Incident
Overview
A LATAM Boeing 777-300 (registration PT-MUG), operating as Flight LA8084 from São Paulo to London Heathrow, suffered a near-total electrical system failure en route on December 18, 2018. The incident occurred less than an hour after takeoff, with the aircraft at approximately 29,000 feet, carrying 341 passengers and 16 crew members.
Sequence of Events
Initial Failure: The electrical problems began with the failure of the right-hand backup generator. This triggered the tripping of transfer and converter circuit breakers, leaving all electrical buses without power.
Loss of Systems: The main generators and the auxiliary power unit (APU) generator became inoperative. Only critical systems connected to standby buses remained powered, such as a VHF radio, emergency lighting, and a few cockpit displays. The ram air turbine (RAT) was deployed to provide minimal electrical power to essential flight instruments and controls.
Technical Findings
Root Cause: Post-incident inspection revealed the issue was not a generator fault but a fault in power distribution. Once the engines were shut down on the ground, power was restored, and systems came back online.
Possible Factors: A phase imbalance in the power system was suggested as a possible cause, which can force all generators offline and prevent reset until the aircraft is on the ground.
Some1-Somewhere@reddit
None of that suggests that it resulted in loss of thrust, thrust control, or flight controls.
---midnight_rain---@reddit
my point was that there are serious design elec issues present on the 777 - and that its not grounded nor were there any ADs released because of this event
Some1-Somewhere@reddit
I'm still not seeing anything that contradicts the statement that:
the FADECs have their own alternator
that alternator is their primary power source
loss of main aircraft power wouldn't unpower the FADECs or interrupt their ability to directly read the thrust lever angle.
That's more or less straight out of the FCOM for every aircraft flying.
It's not the reliability of the rest of the aircraft I'm particularly concerned about; it's the engine-airframe segregation.
---midnight_rain---@reddit
ok different matter:
the 787 has 2 PMAs per engine that provide power to the EEC - but not directly as they require running through the AC bus and then down to DC
the RAT deployment indicates ALL 4 PMA systems failed, which leaves the EEC in the dark until the APU spins up
the 787 is designed without mechanical linkages to the thrust control systems and thus, even manual control is not available (777)
Some1-Somewhere@reddit
I will reply later with an actual keyboard, but are you conflating PMAs/PMGs with the VFSGs? It looks like loss of all four VFSGs would cause RAT deployment regardless of PMA/PMG/FADEC whatever.
I don't believe there's mechanical throttle cables from the cockpit on a 777...
---midnight_rain---@reddit
i definitely could be getting my terms mixed up - im versed the CF6 only - and this is decades ahead now.
and yes, I am wrong - there is no mechanical linkage on the 777
Some1-Somewhere@reddit
Apologies for the significant delay.
I have found a copy of some early 787 maintenance training - I assume everything significant is the same even if e.g. batteries are in more fireproof boxes. In particular:
TLA resolvers:
Flight controls:
The Engines section mentions the PMA for the FADEC a number of times, and shows it being directly mounted to the front of the accessory gearbox.
fugutoxin@reddit
The lack of mechanical linkages to the thrust control systems seems like a violation of Boeing’s basic design philosophy.
Quaternary23@reddit
Just admit you’re a Boeing hater. Literally zero criticism on Airbus throughout their history but “bOeInG iS tO bLamE fOr tHiS, bOeInG bAd, bOeInG eViL” ever since the 1990s/1980s. Yet there’s tons of evidence that shows Airbus is the same but no, they’re “pErfEct”.
---midnight_rain---@reddit
not direct source no - but the parts of the tech manuals have been disclosed on various groups that apply here - there are several weak points identified by people more versed than I.
A similar event (cascade ELEC failure) almost took out a 777 about 5 years ago, a 1:10,000,000 event happened to the electrical buses and the ship was nearly lost. I can find more details if you need.,
Its not an immediate grounding as you think - hull losses need to happen first. ADs are issued all the time.
Some1-Somewhere@reddit
Groundings can happen without hull losses; see the original battery fires.
It would also be relatively simple to mandate that all 787s must have the APU running (i.e. hot standby, like must occur on the 737 to enter ETOPS areas) below 5000ft AGL and remove the MEL listing of no APU. APU start is slow and not especially reliable so is rarely considered as a major backup in an emergency.
I can't see such a catastrophic failure mode being allowed to stand without well publicized ADs and mitigations until fixed.
---midnight_rain---@reddit
the battery fire would have turned into a hull loss - but the took place on the ground due to the electrical transients being introduced
but yes, if you are in the industry - you should be fully aware that failure modes are most certainly 'allowed to continue' if the OEM can demostrate that its a 1:10,000,00o chance or what have you
throwawayShrimp111@reddit
Blaming any party at this point is dumb af.
Discussing possible causes is one thing, saying that "it was pilot error, it was boeing, etc" is idiotic
Srihari_stan@reddit
Having an anonymous ID like on Reddit means they can be experts on whatever they like
Jamalala@reddit
If anyone likes maps and 3d, here's a Mymap with the CCTV location, photo triangulation of the takeoff and crash site. https://www.google.com/maps/d/u/0/edit?mid=1lSA1-PTE9SLKYJRjKfyS8A0EQPXnmIo&usp=sharing
Would be interesting to further estimate the camera and building heights to get a rough altitude in addition to the lateral movement/speed.
humble-bragging@reddit
Thanks for posting this. I've been looking for someone to have found that shed on the sat maps and do exactly this triangulation.
iambloodyfang@reddit
I would recommend watching this video :
https://youtu.be/bHTT9gIit0A?si=KeCfJ-BOboffL2rM
He very well explained the why the floating conspiracies are invalid, and gave possible explanation, since he was a captain before he got connections with air india pilots and explained the root cause.
Quitlimp05@reddit
Hi, the video is mostly in Hindi with some English sentences sporadically and there is no auto-translate option. Would you be able to provide a TLDR?
bonoboboy@reddit
Disclaimer: I am not saying I agree with any of this, just transcribing for others.
I'm not OP, but I can try my best. He goes through a bunch of theories and dismisses most of them. He talks about dual engine failure and how unlikely it is for it to happen, but that this is what he likely thinks has happened.
Then, for legal reasons (getting sued), he says he can't say things, but can only talk about some dreams he has had. He repeats that these are not real things at all, and just dreams he had. The rest of this paragraph are all the dreams he mentions. He talks about pilots complaining about equipment not functioning and flying only at Minimum Equipment Load (MEL). He talks about a Air India pilot flying with only 1 radar from somewhere in Europe (I forget where, maybe London) to India and the other radar stopped working on the way over Iran. He says the pilot said he saw another flight flying at a lower altitude and he followed him pretty much. He talks about Air India cancelling flights now saying pilots may have refused to put up with "MEL" planes any longer. He talks about pilots flying with overloaded planes and cites the example of https://en.wikipedia.org/wiki/Indian_Airlines_Flight_491. He mentions where on the runway the plane would have taken off with two engines operational v/s only one engine operational. He said the aircraft took off even beyond that so he suspects an engine failed and it was overloaded. That the puff of dust you see at takeoff indicates the plane had mostly run out of runway.
He talks about pilot error saying that if the pilot took off so far to the end of the runway, they would be startled. And due to shock they forgot to retract the landing gear. Then he says the pilot may have commanded the first officer to shut down that engine (below 400ft) and the first officer shut down the wrong engine. He says though it needs confirmation, it can happen and cited some GoAir incident as an example. In that example, they had altitude so they didn't crash.
There's also a lot of conspiracy theory type vibes around Boeing and others.
Quitlimp05@reddit
My man, that's an incredible job! Much more so than I expected! Thanks! He sounds more like a pissed ex-employee shitting on things rather than a conspiracy theorist🤪
bonoboboy@reddit
He did mention he was suspended by AirAsia possibly for raising concerns over safety: https://www.livemint.com/companies/news/dgca-suspends-two-senior-executives-of-airasia-india-over-safety-violations-11597119074686.html
jeffbell@reddit
Do we know when Mr 11A opened the emergency exit?
Brief-Visit-8857@reddit
He didn’t open anything. His seat survived and he was alive, the plane had broke apart around him. He removed his seatbelt and simply walked away
JuanSmittjr@reddit
total bullshit. just look at that video which shows him strolling off from the crash scene, phone in hand. (phone inhand!!!) not even a bent hair. no torn or burnt clothes. very very suspicious.
my bet is he was not on the plane, but he's just someone who happened to be in the garden at the time of the crash.
Brief-Visit-8857@reddit
His name was on the passenger list, and he had a boarding pass… he also had burns and injuries. Stop trying to spread conspiracy theories. He also literally lost his brother on the same flight
JuanSmittjr@reddit
this is not conteo, just terribly suspicious. have you seen the vid?
jeffbell@reddit
Oh. My mistake. Thanks for explaining.
thestrongopinionater@reddit
Just curious because I'm completely clueless but if RATs are meant for situations like these, how come it didn't help them in this scenario? Was it because of the altitude etc that it was futile?
Tough-Candy-9455@reddit
There are only two (or four) things that can move a plane forward: the engines. Everything else: the batteries, the APU, the RAT are for emergency power.
787 is a fly by wire aircraft, which means that all control inputs are routed through computer electronic circuits which then move the control surfaces. So in case of a complete power failure the pilots would lose all controls. To avoid that the ram air turbine (basically a small windmill) uses the momentum of the plane against the wind to power the basic stuff like the controls and radio of the captain and emergency lights in the cabin.
Since there were no engines the best the RAT could do was provide control over the plane to the pilots (which it did, there seemed to be massive pitch up attempt at the end) but without a landing spot or altitude there isn't much you can do.
JuanSmittjr@reddit
is there any point in the design where a deployed working RAT can't help? I mean, such a "single point of failure" that could cause the crash and prevented RAT to help even if it was deployed?
Tough-Candy-9455@reddit
Well the RAT, as I said, is simply a last ditch effort so the captain still has control over the plane in case of a complete electrical failure. It's very possible that the pilots have controls and instruments but they are of no help because the altitude is too low to attempt landing at any airport, which might have been the case here.
Some1-Somewhere@reddit
The RAT isn't really about being FBW. Conventional aircraft like the 767 and DC-10 also had a RAT.
Flight computers, radios, emergency lights, and instruments can be powered for a while on batteries, and are on smaller aircraft with controls that can be operated manually like a 737 or ATR.
The RAT is needed to push the flight control surfaces around, which normally takes hydraulics.
Extending the battery range is more of a nice bonus.
Tough-Candy-9455@reddit
Ah, didn't know that. Thanks for the info
Legal_Literature1356@reddit
Depends on what kind of help we're talking about. The RAT does provide electrical power for avionics and for the electrical hydraulic pumps, but it can't produce thrust, it's basically just a small windmill.
railker@reddit
And for clarity, RATs do differ, but in this case I believe it provides electrical power and also IS the hydraulic pump. Which is why in ground test videos of the RAT you can see big hydraulic lines hooked up to a hydraulic power cart/mule to 'drive' the RAT for the test.
ChillFratBro@reddit
A RAT doesn't provide thrust. No thrust, no fly. If a plane lost its engines at 30,000 feet, it would also start falling out of the air - but the time it takes to glide down from that altitude (tens of minutes) would hopefully give the pilots time to either find a runway in their glide radius or restart at least one engine.
At less than a thousand feet above the ground, you just don't have the time. Once that aircraft lost both engines at that altitude, it was doomed - there was absolutely nothing that could have saved it.
pipic_picnip@reddit
Not an expert either, just paraphrasing based off all the posts I have read so far in 3 threads. It’s because RATs have very limited capacity, they are meant to provide small window for crew to troubleshoot and restart engine. They aren’t powerful enough to run the entire plane by itself. Because in this case, the time from take off to crash off was so small (and from RAT deployment to crash even smaller), and presumably positive climb never reached since the plane nose is still up while descending, they had no altitude or anything else to take control of the aircraft and attempt any troubleshooting.
Brief-Visit-8857@reddit
Actually, they reached positive rate before the engines went out. The gear is tilted forward— possibly indicating that the gear was selected up when the catastrophic failure happened.
Commercial-Lemon-336@reddit
Also not an expert, I believe rat systems are designed to keep enough power on for things like radio communication as you glide down for an emergency landing.
Brief-Visit-8857@reddit
Earlier today, a news channel reported that the black boxes will be sent to the US for data extraction. Turns out that was fake news according to Reuters, India still hasn’t decided where to sent them to.
Link: https://www.reuters.com/world/india/india-send-crashed-planes-black-box-us-local-newspaper-economic-times-reports-2025-06-19/
JuanSmittjr@reddit
can the extracted data be share with different investigator groups a the same time?
Brief-Visit-8857@reddit
No
sizziano@reddit
Weird that they haven't even started the data extraction process.
Brief-Visit-8857@reddit
Gotta consider the possibilities. That’s what Ethiopia did after the MAX crash because they didn’t want bias in the data extraction. They sent it to France. I’d assume the same would be true in this case. That to me tells they still don’t know what caused the crash, so they’re being cautious.
Legal_Literature1356@reddit
So, data extraction won’t happen in India? And now it’s up to the Indian authorities to decide whether to send the black boxes to the U.S. or involve any third party for extraction?
Brief-Visit-8857@reddit
Yes, India didn’t have the required equipment, especially since they were damaged by smoke and fire. So they have to send it to a different country.
ActRevolutionary1065@reddit
Hope the future flights will be safe, nobody deserves to die like this
drtywater@reddit
Is the Indian government going to do updates before preliminary report is ready?
Brief-Visit-8857@reddit
Probably not. The FDR takes like 25 hours or something like that to decode.
JuanSmittjr@reddit
what happens with the data? is it "replayed" in some kind of simulator? or how are they analysed?
Funkytadualexhaust@reddit
Would the recorders hold up through main power loss, before RAT? Does RAT power recorders as well?
railker@reddit
At least one of them does have a RIPS (Recorder Independent Power Supply) which runs functions for the recorders for 10 minutes. I'm getting mixed messages from the documentation, but at least two of them specify the forward EAFR has it.
Some1-Somewhere@reddit
A previous NTSB report says the forward recorder has RIPS, the rear does not. Similar age aircraft.
I'm not sure whether the left/right DC buses get re-energised on RAT power.
JuanSmittjr@reddit
out of curiosity, why aren't all the recorders in their own battery?
Some1-Somewhere@reddit
The redundant recorder is already a new thing on the 787, and the requirement to have a backup battery for the recorder is only a few years older.
It's more weight/maintenance/cost.
Having one on a battery and one not means you get a slightly longer recording time (due to the overlap). Pilots unions have fought hard against more/longer recordings.
JuanSmittjr@reddit
this union opposition us very strange. thanks for the answer.
kussian@reddit
Does this relate to those past 787 problems with batteries? Report is dated by 2013 and if I am not mistaken problems with batteries happened later.
Some1-Somewhere@reddit
That's the FDR report for the second(?) 787 battery fire; the one at Boston Logan.
bkirbs13@reddit
The Recorders have their own independent power supply in case of loss of all other power sources.
fhjjjjjkkkkkkkl@reddit
I work on the black boxes for ships. Why not they just move the data to cloud.
I know it’s very hard to determine ownership of the data when it’s in cloud. But it can make progress faster. Anything related to investigation to the safety of the whole system
2FAmademe@reddit
It could make sense to have near real time diagnostic data, but we’re a long time away from having official cloud black boxes. Not nearly reliant enough to provide the reliability that current black boxes have.
ViPeR9503@reddit
With Starlink started to be deployed on a lot of airplanes I think it’ll give airlines a lot of bandwidth to work with now I guess.
fhjjjjjkkkkkkkl@reddit
But I feel it’s not about the technological bottleneck. It’s more about the sensitivity of the data.
When the data is on the vessel/plane then it’s the company internal security apparatus to prevent the data from being hacked or use it against the owner. Once the data goes to cloud ,the owner doesn’t have much control. I think lots of new framework need to be added to cut down the time to access the data.
Super_Forever_5850@reddit
Probably because transfer to the cloud is to unreliable. These gets smashed up pretty bad during a crash and also even the last milliseconds before the crash could have vital data…I’m guessing that will never reach the cloud in these crashes.
Neevk@reddit
I don't really know that much about planes but in the worst case scenario where the recorders shut down due to power loss, at least we would know that there was some kind of power loss by matching the time stamps, the crash and any sort of system failure should be easily differentiated as the crash happened 10-15 seconds after the suspected failures.
gw19x6@reddit
I am confused about the Black boxes: were on this aircraft 2 boxes of the modern type where CVR & FDR is combined in 1 box? Did they recover both? And they are not able to read out the data of 2 separate boxes?
railker@reddit
https://www.reddit.com/r/aviation/comments/1ld9yb8/comment/myq8fj6/
Reports are they have recovered both, but because of external damage to the memory module. You get 1 shot at recovering that data, especially if there was truly a full power loss as only 1 EAFR has a backup power supply. They haven't decided yet, as far as I can tell, if they're going to attempt it themselves or send it to the NTSB or elsewhere. That would appear to be the reason they're hesitating, the experience and expertise level at performing the data extraction.
But of course, these reports are all second-hand at the moment and there is no official word on the state of the boxes or where they're being sent from official sources.
DaBingeGirl@reddit
I understand wanting to do it themselves, but at the same time this sounds like a job for the NTSB.
railker@reddit
I mean, they're allowed to be there too, I don't imagine they'd just ship it off and hope, they'll be there in the lab to observe when they open it and through the process, they are still the lead investigating agency.
DaBingeGirl@reddit
They have their own lab, so initially it sounded like they wanted to handle it entirely by themselves. You're right that Indian investigators would be there even if it goes to the NTSB, so I really don't understand the "cover for Boeing" nonsense some people are posting.
Some1-Somewhere@reddit
I suspect it is less about being free of tampering and more about being seen to be free of tampering.
See: all the claims that the last few minutes of the Jeju recorders were 'erased'.
ECrispy@reddit
I asked the qn in that post, so it seems they haven't been sent yet ?!
still don't understand how there was any damage - these are built to survive far worse, and this was a best case scenario, its just a fire which was put out quickly. no sea, altitude, or extreme forces.
gw19x6@reddit
Thanks a lot
V0latyle@reddit
Someone on Facebook sent me this, so of course it's unconfirmed, but seems factual and plausible. My thoughts at the bottom.
Primary Cause – Electrical Power Transfer Interruption (PTI) During Rotation • During transition from ground to airborne electrical configuration, the aircraft experienced a cascading dual-engine FADEC (Full Authority Digital Engine Control) failure. • Root cause: Uncommanded bus transfer failure due to arcing in the main power relay box (PRB-A), traced to water ingress during pre-flight GPU disconnection in heavy rain. • This led to loss of electronic engine control at rotation, resulting in both GEnx engines rolling back to ground idle within 4–5 seconds.
Flight Data Record Timeline • +0:11 sec: Nose gear lifts off. • +0:13 sec: Sudden engine rollback begins. Thrust reduces from 92% N1 to <27% within 3 seconds.
• +0:16 sec: Master caution + ENG FAIL L/R warnings. FO calls, “Both engines dropping!”
• +0:20 sec: Autopilot and flight control reverts to Direct Mode. Pitch up attitude peaks at 18°.
• +0:25 sec: Aircraft stalls at 186 ft AGL. • +0:30 sec: Full aerodynamic stall; nose drops rapidly. • +0:38 sec: Ground impact at 54° nose-down attitude, 174 knots.
Contributing Factors • Environmental Conditions: • Torrential rain during pushback. • Moisture intrusion into PRB-A connector (P/N: HLN8471) — a known corrosion-risk component. • Latent Maintenance Issue: • Power transfer relay unit showed signs of thermal damage in a previous MEL deferral 2 weeks prior. • No replacement had been conducted; aircraft was cleared under repetitive deferral.
My thoughts: * Do the FADECs have their own dedicated Permanent Magnet Alternators, and each FADEC is at least dual channel redundant?
Does this redundancy extend to the cockpit - meaning positive engine control should be preserved even with complete electrical and instrument failure?
Is there "crossover redundancy"? For example, let's say there's two channels for both FADECs, A and B. A would be powered by the #1 PMA, and B would be powered by #2, so loss of single PMA would not result in FADEC failure.
If anyone has access to electrical bus diagrams for the 787, this would be useful in proving or eliminating this theory
Some1-Somewhere@reddit
This documentation might help: https://archive.org/details/b787-meav-type-1-training-manual/ATA%2024%20Electrical%20Power%20Systems/page/7/mode/1up?view=theater
Mpmqbi@reddit
Do people genuinely have no critical thinking skills any more? This is very obviously the complete opposite of factual and plausible. The date doesn't match and from the footage you can clearly see that there is no torrential rain
Blythyvxr@reddit
This is the bullshit AI generated report. The date is wrong for a start, and there’s no way anyone would have any information sufficient to come to any conclusion like that at this stage.
V0latyle@reddit
Fair enough, I failed to pay attention to details. Edited.
railker@reddit
This must be sourced from that AI-generated report that's been floating around, not the first time I've seen something similar. I don't see any rainclouds in the video and the METAR report for the airport for at least 4 hours before they left was clear skies.
I also have yet to see any confirmation the CVR's even been opened, let alone transcribed and almost certainly not released outside the bounds of a Preliminary Report.
V0latyle@reddit
Yeah, it seems pretty premature to me as well.
However, torrential rain is common in India, and this could be a latent failure...but even so, I have to wonder whether both FADECs would be susceptible to such a single point of failure?
the_woah_guy@reddit
Mom said it was my turn to post this now.
ECrispy@reddit
Can someone confirm about black boxes -
Lost-Inevitable42@reddit
No expert here but this is what I think I know:
Yes, despite many news stories, the 787s don’t have two separate CVR/FDR. They have the EAFRs. I think many news writers just assumed it was standard since it’s been like that for almost all other plane incidents. And I think there was some bad info coming out of the AAIB initially too.
I think only the forward EAFR has the RIPS (recorder independent power supply). That gives it like 10 mins of its own power. That could be critical if this was a loss of power issue.
It sounds like both have been recovered. It’s not clear on the damage really. Also, I believe there was DVR that captures what some of the cameras see.
The new facility may not have the specific equipment or expertise for the data extraction from these devices. They are new and niche and the systems around it cost a lot more money. I suspect that’s the real reason they’d send the boxes abroad. I think right now it’s a bit of saving face since the facility is so new. (This is all speculation).
For more info on data and extraction:
https://scaledanalytics.com/2023/04/25/arinc-767-or-what-do-you-mean-my-b787-uses-767-data/
Also you can quickly find reports around a 2012 787 incident and the process of data retrieval. I can get the links if you can’t find. While there haven’t been any fatal crashes, there have been incidents that required blackbox downloads.
I expect captain steeeeeve to shift (grift?) to talking about this soon enough.
PestyNomad@reddit
I'm surprised they don't upload some system metric data to a server while in-flight. Maybe security concerns - ?
railker@reddit
There are some aircraft and airlines that do this -- that's how we knew all the things we did about Air France 447 two years before we actually found the black boxes, a system called ACARS (Aircraft Communications Addressing and Reporting System) transmitted the error messages the pilots were seeing across the minutes of the crash, including 'AUTO FLT AP OFF (Autopilot Disconnect), F/CTL ALTN LAW (Flight control system reverted into Alternate Law), faults relating to the pitot tubes, and finally, ADVISORY CABIN VERTICAL SPEED (the pressurization in the passenger cabin was descending too quickly as the aircraft plummeted towards the ocean). The very first Preliminary Report is a good insight into how much investigators DID figure out before they had the full FDR and CVR recordings.
In this case, I'm not sure there was enough time for anything useful to be transmitted as I believe there's some time delays involved, and whether or not Air India participates in such parameter monitoring, usually more for convenience and efficiency than accident investigations. And for all the information it did give and made sure a fleet-wide pitot tube replacement on the Airbus A330 was expedited faster than it already was, nothing it transmitted could tell them that the First Officer was inexplicably trying to climb the aircraft out of a stall all the way down to the ocean, or the confusion that happened in the cockpit across those minutes.
PestyNomad@reddit
Thank you for this detailed explanation. It seemed like remote performance monitoring should be possible but the delay and / or participation make sense.
Illustrious_Crab1060@reddit
even MH370 in 2014 had sent out some parameters during its flight in the middle of the ocean
ECrispy@reddit
It was almost certainly loss of electrical and engine power, full system bus failure maybe, we have RAT to cofirm power loss. What happens in this case - do the cvr/fdr have no battery backup at all and simply stop? Why can't they have an independent battery for a few hours - 10min sounds very low
railker@reddit
I don't know if this is what the RIPS accomplishes, but the big problem with backup power for the FDR is you also have to supply power to everything feeding the data to the recorder, thousands of sensors and inputs plus flight computers, etc. Without powering those, you record nothing for 10 minutes.
ECrispy@reddit
there is a priority of systems and sensors eg in the order they will be selected for critical power delivery. So you'd imagine critical ones would still be powered, eg recording inputs/reponse to primary flight contol surfaces, FADEC etc.
Consumer UPS can supply power to a gaming rig for 30min, same for critical systems in data centers etc. 10m seems way too low and thats only in the newest aircraft?
railker@reddit
There was an initial report they were being sent to the US, but then another came out saying that wasn't the case and India was still deciding what to do. Lots of false or misleading information floating around right now.
If they do still do that, I imagine it'll be because of the high significance of a crash like this and wanting no chances of anything going wrong in the data extraction. But they also do have the NTSB and others on-site to help advise them, too.
It's been said the data extraction phase from the FDR could be up to 25 hours. And then you have 2,000+ parameters to review and make sense of. Among all the other forks of the investigation beyond those boxes. I imagine the preliminary will contain information from those boxes, but it will be only factual, not necessarily a cause.
i.e. the crash of N823KD on a highway in Florida last February. Preliminary came out later indicating what the pilots said, what warning messages came up as both their engines failed. We know the results of their preliminary inspection of the wreckage of the engines that didn't find anything damning. Almost a year and a half later the investigation as to WHY exactly that happened is still ongoing.
Proud_Engine_4116@reddit
The 787 has 2 redundant combi recorders. It has 2 combined FDR/CVRs.
I think VT-ANB also had a DVR for cameras and possibly even has cockpit video.
Finally, I think there is a third digital voice recorder as well.
https://www.flightglobal.com/boeing-787s-to-be-fitted-with-enhanced-data-recorders-/67970.article
Comprehensive_Dish_6@reddit
Fuel Shutoff Valves default to a closed position on the loss of all AC/DC power?????
This spring loaded cut off on loss of power is how we design the electronic throttle system in single engine University Formula Student Race Cars that can pull over anytime - but how is this ok for an aircraft - who on earth thought of this???
Fleet wide grounding please? I'm scheduled to get on a 787 and would rather not if it is a software electrical switch issue.
https://youtu.be/VswFVpyg5ew?si=_qzTd4sKt6TqDBrf&utm_source=ZTQxO
RB26Z@reddit
I don't get it. Why would the plane have fuel cut off to engines when electrical power is lost? What is the logic behind that action? We have loss of electrical power so now let's go ahead and cut off engine power while we're at it? Most ridiculous thing I've heard all day. Maybe with that logic they should go ahead and have all the passenger and cargo doors automatically open for fun while they're at it.
TOAO_Cyrus@reddit
Found this comment on airliners.net.
Also not definitive proof but the poster has been on that forum for 15 years and is in the industry. Looks like there is a spring involved but is not held open by electrical power at all, but by fuel pressure. Power is needed to close it with a solenoid, not hold it open. In the absence of power it will stay open as long as there is fuel pressure.
This makes way more sense then the YouTube comment but does shed some light on how a little bit of knowledge could lead to the idea, IE it is spring loaded closed but not understanding how its held open.
RB26Z@reddit
Thank you for taking the time to find that and post it here. I really appreciate it!
Comprehensive_Dish_6@reddit
Original Comment:
"Original comment from HeyFixThis
I believe the cause was a combination of Fuel Shutoff Valve (FSOV) activation due to an cascading electrical system failure. It’s not the first time a 787 has experienced electrical cascade system failure during the first minutes in flight and required RAT deployment. Let me explain my reasoning:
On the Boeing 787, the engines will keep running even if all hydraulic systems fail. Each engine has its own FADEC (Full Authority Digital Engine Control), powered by a Permanent Magnet Alternator (PMA) that’s driven by the engine itself. Once the engine is spinning, the FADEC operates independently — controlling fuel, thrust, and safety — with no need for aircraft hydraulics or external electrical power. A simultaneous FADEC failure is extremely unlikely.
So, why did the engines shut down if they are supposed to be so resilient? There is one important component that can override the FADEC: the FSOV. This spring-loaded fuel shutoff valve is not powered by the PMA, but instead by the aircraft's electrical DC system. If power is lost, the spring closes the valve instantly, cutting off fuel to the engine. FSOVs are a fail-safe, designed to protect the airframe, not the engine. In Boeing’s logic, it's safer for the engine to shut down than to keep feeding fuel into a potential fire.
In the video footage, the truck tilt actuator is in the forward position (toes down). This movement requires a hydraulic system force to overcome the wind and gravity. This forward position only happens when the landing gear retracted sequence is initiated by the pilots.
The strange thing is that it is only the second step of the main gear retraction sequence to tilt the wheel truck forward. The first step is to open the doors, and if the doors are fully open, the next step is to tilt the wheel truck. It’s unclear why the doors are closed but the truck already tilted forward.
Some1-Somewhere@reddit
It's straight up false. The valves are power-open power-closed.
Comprehensive_Dish_6@reddit
loll someone else also reposted the comment on another thread 2 days ago - go look there for other people's expertise on the 787
Comprehensive_Dish_6@reddit
Part 3:
The RAT was automatically deployed. This means there is a total loss of AC electrical power.
I suspect a scenario where a partially working or unstable electrical system triggers RAT deployment amid a power transition event. This could escalate into a full-blown electrical disruption, possibly interfering with the DC essential buses and battery backup. When switching power sources (from main buses to RAT), the system can behave unpredictably — especially if one source is competing with the RAT or is unstable.
In such a power chaos, RAT deployment might introduce transients or delays in power restoration, which could make power delivery unstable and possibly affect the digital managed power to the FSOVs. If they lose power, all fuel will be cut off.
On the 787, FSOVs don’t have guaranteed dedicated or hot battery backup, unlike the Airbus A320, which powers them directly from the battery. The 787’s battery backup supports the entire DC bus, and power management software prioritizes flight-critical systems. If power is limited or loads are erratic, less critical systems like FSOVs can be deprioritized. This is a very complex system with a lot of software rules.
This also reflects Boeing's design philosophy: in a severe power failure, airframe survivability and flight control take precedence over engine continuity. Their assumption is that it’s safer to shut off fuel than risk uncontrolled flow in to an engine on fire.
The whole idea of the posibility of losing both engines at 400 ft during takeoff feels inherently unsafe. From a thrust continuity perspective, this design approach is a vulnerability and may have played a role in Flight AI171’s dual-engine flameout.
To date, there are no documented cases of a modern Boeing experiencing a engine flameout from FSOV closure due to an electrical glitch. The 787 and other Boeing models have a history of similar electrical issues.
In 2024 an Atlantic Boeing 787 flight, VS105 during climb-out, the crew experienced a major electrical failure— engine generators dropped off-line. In response, the RAT automatically deployed to provide emergency power.
In 2015, Boeing and the FAA discovered a critical software bug in the 787’s Generator Control Units (GCUs). If left powered for 248 consecutive days, an internal counter could overflow — shutting down all four GCUs and cutting AC power entirely. The FAA issued Emergency AD 2015-08-51, requiring operators to reboot 787s every 8 months to avoid in-flight total power loss.
Two separate incidents—in Boston (JAL) and Takomatsu (ANA)—involved battery overheating and fire in the aircraft’s APU lithium-ion batteries
In December 2018, LATAM Flight LA8084, a Boeing 777-300ER, suffered a complete electrical meltdown en route from São Paulo to London. The RAT deployed to provide emergency power. Once the engines were shut down on the ground, power suddenly returned — confirming a fault in the electrical distribution system (likely a bus contactor or converter failure). The event was a textbook cascading failure: generator power was available, but a chain reaction of breaker and converter failures disconnected all major buses, including those powered by the APU and engines.
The 787 relies heavily on software-based power management, so if the root cause turns out to be a software flaw in a extremely complex electrical system, the entire fleet could soon be grounded pending investigation.
——/
I rule out vaper lock: Modern jet fuel systems are pressurized and temperature-managed, making vapor lock rare. For both engines to fail simultaneously from vapor lock would mean identical thermal, pressure, and fuel conditions in both lines — extremely unlikely."
RB26Z@reddit
Yes I read that earlier, but it is still illogical to shut off fuel to the engines to preserve the airframe when the airframe will get destroyed if engines are needed to maintain lift (not just at takeoff but any other time during flight including landing). Assuming the engine is on fire makes no sense. I have a hard time believing that was their logic and the system is made for that reason...seems like something else failed to turn off the engines rather than programmed to do that imo.
TOAO_Cyrus@reddit
It's completely made up. The last time this was posted I did a deep dive on how the shut off valves work and could not find a single reference to them being spring loaded or have any type system that would fail closed on power loss. There are discussions about failure modes with the valves on places like airliners.net with actual pilots and mechanics commenting and no one mentions this.
RB26Z@reddit
Thank you. I'm glad I'm not the only one that finds it unbelievable such a spring mechanism would exist to and the default is turn off engines if electrical lost.
Brief-Visit-8857@reddit
Probably a software error, caused by a cascading electrical failure. I believe that a we might be looking at a software bug that went undetected because they could have never imagined a situation like this
Proud_Engine_4116@reddit
It probably wasn’t fuel cut off. Maybe it was bad, stale data from the CCS (Common Core System) that was being fed to the FADEC.
Comprehensive_Dish_6@reddit
Part 2, original comment by Hey Fix This:
Most likely the pilot selected “gear up,” which triggered the retraction sequence. The truck tilt was initiated as step 2, but the doors didn’t open due to power or hydraulic failure, or the sequence froze mid-process. The aircraft lost main power (hence the RAT), and the sequence halted with the gear in a partially commanded state: truck tilted, doors closed, gear extended.
That gear retraction moment may have been the exact point when the whole system collapsed just 3-4 seconds after takeoff.(there was a positive climb rate at 600ft AMSL and 174kt ) The engines kept running briefly (3seconds), powered by the remaining fuel in the lines before flaming out.
The main landing gear hydraulics are powered by an electric-hydraulic system — if there’s no electricity, there’s no hydraulic pressure. In contrast, other hydraulic systems on the aircraft are supplied by engine-driven mechanical pumps. (20-30kw power needed to retract gear)
Since the aircraft remained stable in flight, it's likely that both engines flamed out simultaneously. Flaps, fly-by-wire, landing gear, and other systems likely froze for a moment and possibly regained functionality after the RAT deployed. The +-15kW RAT powers the electric motors on the blue hydraulic lines of a 787. This controls the key flight-control actuators for the rudder, elevators, and primary ailerons. It appears that the pilot slightly increased the nose attitude during the final phase of the flight. (landing gear retraction is not possible with a RAT)
For both FSOVs to close, the aircraft would have to lose both AC buses, both DC essential buses, and the battery backups. That requires a massive electrical failure to overcome all possible redundancy layers. This is a possibility because there are known cases where a 787 and a 777 experienced a total electrical cascading failure of most systems. So it is possible.
All signs point to fuel cutoff via the FSOVs. The big question is why did they fail? This is hard to say but as said electrical failure is a very plausible cause.
railker@reddit
Another comment with technical knowledge to counter the spring-FSOV theory.
https://youtube.com/watch?v=VswFVpyg5ew&lc=UgykSxt88Oe0U23NzpN4AaABAg
NoteChoice7719@reddit
That’s absolute and utter nonsense. No aircraft manufacturer is going to design a system which shuts off fuel to engines in a complete power loss
Brief-Visit-8857@reddit
So, the gentleman who came up with this theory was right: https://www.reddit.com/r/aviation/s/mXBMG0F2qC
twopointsisatrend@reddit
Interest seems to be converging on fuel starvation to both engines. Contamination, especially that affects both engines at the same time seems unlikely, especially since taxi and takeoff seemed fine. The engines stopped producing thrust shortly after rotation, so I wonder if there was something like a bad repair that caused some component failure, resulting in fuel starvation when the aircraft rotated for liftoff.
Cold_Flow4340@reddit
wouldn't fuel contamination would have likely effected other aircraft?
Not____007@reddit
The fact that Air India has been over the top in cancellng any 787 flights for the most minor issues is leading me to believe that it was def an airplane issue and they have no clue yet on what caused the defect. So theyre not taking any chances and ensuring maintenance is done right away. It could also be that maybe it was due to some maintenance issue:
railker@reddit
To be fair, if they knew what it was they'd know where to look.
Their inspections are covering all bases our speculations are - checking fuel, engine power assurance and fuel-driven actuators, cabin pressurization, engine EEC, hydraulic systems, and whatever' review of takeoff parameters' means. They're painting a wide brush and hoping maybe they find something systemic and not unique to this aircraft. But IMO after a decade of flying, something unique to this flight or aircraft is what my money's on, some coincidence of factors.
Not____007@reddit
“While there has not been an update on the possible cause of the crash, Indian officials have raised concerns about recent maintenance-related issues reported by the airline and advised the carrier to "strictly adhere to regulations".”
https://news.sky.com/story/british-survivor-of-air-india-crash-discharged-from-hospital-airline-confirms-13385528
ChillFratBro@reddit
It was almost certainly maintenance. Look up the "bathtub curve" - mid-lifespan failures are almost always maintenance. Now, that doesn't necessarily mean Air India fucked up - it could be that an allowed maintenance procedure causes damage in unknown ways and they followed the manual straight in to a tragedy.
If the design of the plane was flawed, this wouldn't be the first hull loss. If this specific plane were flawed off the assembly line, it wouldn't have flown safely for over a decade.
RB26Z@reddit
Didn't the 787 have an issue with metal shavings left during assembly near wiring harnesses? The FAA I think in 2017 required that issue to be addressed, but not sure how older planes had it done. The QC manager that brought up the issue has since died, but he was worried it could damage wiring well after delivery so like mid-life as you say. Not sure they could deduce that from the wreckage given how much fuel it had and burned down.
ChillFratBro@reddit
It did, but that was the Charleston SC plant. This specific plane was built in Everett WA, and no one has alleged similar negligence from the Everett facility.
Also, the catastrophic concern there would be damage to a high voltage harness, which could cause a fire - and this accident happened way too fast to be a fire on the airplane. Fires gradually take out control systems over the course of minutes - they wouldn't shut down both engines in the span of seconds, especially not without a very visible external sign.
The chances of all 4 redundant control wiring harnesses severing on metal shavings within single-digit seconds are so remote that I would put money on a unicorn popping the invisible balloon filled with fairy dust that keeps planes in the air over 4 redundant control harnesses with separate routing being simultaneously severed.
Brief-Visit-8857@reddit
They inspected all the 787s after the crash, the DGCA found that they were all in compliance with standards. So it was probably damaged caused in unknown ways
pipic_picnip@reddit
I think there are two likely aspects to consider:
all 787 fleets were inspected, found to be compliant and numerous other “to be on safe side” measures are being put into place, but nothing has suggested any movement in the fuel category like an inquiry into fuel supply etc
Flights are being grounded or reversed for the tiniest of reasons. This shows a very clear “we don’t know what we are dealing with and don’t want a repeat” kind of hysteria
Both of the above point to Swiss cheese theory that this is an unprecedented case of its own kind that has lined up multiple near impossible conditions to trigger a fatal flaw in the system, something that no one is familiar with. I do not think the way the regulators are responding seems very consistent with an open and shut case reason like fuel contamination or any other reason that can easily explain away the crash. At this point we are possibly looking at months, if both years of investigation into announcing the definitive cause.
No-Understanding-589@reddit
Yeah I spent a lot of time reading an Aviation forum last night that has a lot of 787 pilots and engineers thoughts on it. And as a group the general consensus is that it's one of 2 things
1.) An incident that we have never seen before due to a bad maintenance mistake or a software glitch. 2.) A very, very bad pilot error - along the lines of fuel switches being accidentally switched off upon takeoff
- or them setting 200 feet on the altimeter instead of 2000 feet which will make the auto throttle pull back thrust. Then they have been so far behind the plane, they haven't realised what was happening and just pitched up and sank into the floor (but this wouldn't explain the RAT noise and lack of engine noises heard so it is unlikely)
One of them even has a friend who went into a 787 simulator and tested the flaps theory with a seriously overweight plane and it was still flyable.
I think it is more likely option 1 and agree it will take a long, long time to find out how all the holes in the model lined up. A modern plane losing thrust at takeoff is supposed to be impossible - so it's definitely a unicorn situation that will take a long time to figure out
Designer_Buy_1650@reddit
2 is definitely not the problem. With an altitude capture all they would have to do is click off the auto throttles and push power up or on the capture, press toga again.
Spa_5_Fitness_Camp@reddit
That assumes they realize the problem. The panic response is real, well documented, and responsible for countless commercial aviation crashes.
Designer_Buy_1650@reddit
I guess you haven’t watched the crash videos. Absolutely all pilots would firewall the power if they saw they were about to crash because of no thrust. I’m sorry, but your comment is borderline stupid.
Spa_5_Fitness_Camp@reddit
You must not know much on historical crashes. You should try making the right point. You say yourself "because if no thrust". Your assumption is that they realize that. More than one crash has happened because they don't realize the actual problem.
Some1-Somewhere@reddit
Crew failing to do that is not likely, but a 787 crashing is not likely. It's happened on other aircraft and resulted in them getting within 60ft of the ocean, and it's not too dissimilar from Asiana 214.
There's a bunch of hints that they probably had a near-total electrical failure so it doesn't seem likely, but "the pilots should have noticed" isn't really a catch-all fix.
Funkytadualexhaust@reddit
60ft? Link?
Some1-Somewhere@reddit
Claimed here and here.
Also see EK321, though less relevant: https://www.gcaa.gov.ae/en/departments/airaccidentinvestigation/Pages/InvestigatorMagazinesView.aspx?min=gl9avmeG1v&type=ir
BubblyAvocado9@reddit
What forum is this? For my curiosity...
twopointsisatrend@reddit
Or avherald.com
Cumulonimbus1991@reddit
Probably Airliners.net
https://www.airliners.net/forum/viewtopic.php?f=3&t=1502635
bokononon@reddit
not op, but probably PPRUNE
https://www.pprune.org/accidents-close-calls/666581-air-india-ahmedabad-accident-12th-june-2025-part-2-a-24.html
Brief-Visit-8857@reddit
Yeah, this kinda feels unprecedented. I’m sad for all the lives lost. Hopefully this doesn’t happen again and we learn from it.
bobblebob100@reddit
Dont both engines run independently tho? So what effects one engine shouldnt really effect the other?
twopointsisatrend@reddit
Yes they run independently. I was thinking more like something causing all fuel pumps to fail. From what I understand though, even if that happens the engines can suction feed from the fuel lines. Keep in mind that I know nothing about the fuel system in the 787. But the engines appear to have run flawlessly until after rotation. Because of that contamination seems unlikely. So I'm thinking something failed due to the angle of attack at rotation. The aircraft remained in a nose up attitude until impact, so the failure remained.
More to the point, I'm wondering what points in the fuel system are common to both engines that could cause a failure. It might not even be the fuel system, rather something that controls the engines. There's a lot of redundancy built into the system, but maybe it required action by the crew, and they didn't have enough time to even identify the problem.
captainhaddock@reddit
I'm intrigued by the idea that an inexperienced mechanic working on both engines before flight could have made the same mistake on both of them. That's the kind of situation where both engines could experience the same problem simultaneously, without any pilot error, software error, or fuel problem.
Skyris9@reddit
the
Blythyvxr@reddit
New AVHerald update:
https://avherald.com/h?article=528f27ec&opt=0
gnorrn@reddit
Mentour Pilot made a nice video about the Titan A321 incident: https://www.youtube.com/watch?v=E4Qclymu2EA
Brief-Visit-8857@reddit
I highly doubt it was fuel contamination tough… authorities are probably looking at other dual engine failures around the world to see if they have any similarities. Also note that in the report for the Titan a321, it states:
We don’t see any of that in AI171’s crash. Link to the report: https://assets.publishing.service.gov.uk/media/6087c670e90e076ab1e3492c/1-2021_Airbus_A321-211_G-POWN.pdf
batsy71@reddit
for clarity, AAIB is a british org.
Brief-Visit-8857@reddit
Highly doubt it’s fuel contamination though… they’re probably looking at other dual engine failures around the world to see if they have any similarities.
ProgressEquivalent50@reddit
Could water in the electrical equipment bay have caused the Air India crash? If electrical failure was involved, here's a technically plausible scenario of what might have caused that failure:
Documented water leaks: Nov 24, 2023 - Video showed water leaking from overhead bins on Air India 787 flight from Gatwick. Air India confirmed and apologized. (https://www.indiatoday.in/trending-news/story/air-india-issues-statement-after-video-of-water-leakage-on-flight-goes-viral-2469532-2023-11-30)
FAA directive: AD 2025-09-12 addresses "water leakage from potable water system...leaking into electronics equipment (EE) bays...resulting in water on equipment in EE bays." (https://www.federalregister.gov/documents/2025/05/14/2025-08346/airworthiness-directives-the-boeing-company-airplanes)
Survivor's account: Sole survivor heard loud bang before crash. (https://www.ndtv.com/india-news/air-india-dreamliner-crash-heard-loud-noise-30-seconds-into-flight-says-survivor-vishwash-kumar-ramesh-8653258). Captain Scheibner suggested RAT deployment, but RAT deployment is spring-loaded and likely no louder than landing gear deployment and would probably produce a "thump" not a loud bang. No past evidence supports cabin-audible bangs from RAT deployment.
Electrical arcs on airliners cause bangs: 1985 B757 incident - pilots heard "two loud bangs" during electrical generator failure. (https://www.angelfire.com/ct3/ctenning/electrical_essays/monarch/monarch.html)
Water sloshing scenario: Pooled water in EE bay could slosh backwards during rotation, reaching 3-5 inches - the approximate standoff height of equipment. This could cause simultaneous short circuits and arc flashes. [787 EE Bay photos](https://en.wikipedia.org/wiki/Avionics_bay), [787 electrical system](https://fliphtml5.com/quwam/qhdw/Book_1_-_Introduction_to_B787_Avionics_Electrical/)
787's unique vulnerability: Carbon fiber hull (vs aluminum) lacks conductive structure for single grounding path. This creates multiple simultaneous arcing paths between equipment, making failures more chaotic. (https://cdn.glenair.com/qwikconnect/2023/jul/pdf/grounding-and-bonding-in-aircraft.pdf)
Electrical dependency: 787 relies more on electrical systems than hydraulic/mechanical, making it especially susceptible to cascading electrical failures. (https://en.sirajul.com/10/issues-with-boeing%E2%80%99s-%E2%80%98more-electric%E2%80%99-design)
This doesn't explain engine rollback but could explain why Air India 171 was particularly vulnerable to catastrophic electrical failure due to water leakage and slosh on takeoff rotation.
Brief-Visit-8857@reddit
No. If a water leak causes your entire airplane to go down, then I’m sorry but that’s literally a very critical design flaw. The airplane is supposed to have many redundancies to prevent one thing from being down the entire airplane.
railker@reddit
And the thought of the buildup of that much water ignores the existence of dozens of fuselage drain valves.
The risk in the cited AD is confined mostly to water leaking directly onto components. Could still be a factor, but also again, unless that AD is still outstanding or Air India broke the law and ignored it, it also shouldn't be an issue.
ProgressEquivalent50@reddit
The AD went into effect June 18, 2025. 6 days AFTER the crash. https://www.federalregister.gov/documents/2025/05/14/2025-08346/airworthiness-directives-the-boeing-company-airplanes
railker@reddit
VT-ANB was delivered to Air India in January of 2014, Line# 26 according to AirFleets. The earliest aircraft the AD you reference applies to Line# 548, delivered to United in January 2018.
The AD notes that the problem was "known since 2016, the omission of sealant in the airplanes added to this AD didn't occur until 2018" and references an older AD 2016-14-04. That one did appear to apply to VT-ANB, with an effective date of August 12, 2016 and a compliance date of 2 years to replace some affected lines and 5 years to do a full floor sealing, reroute wiring, drip trays, big modification.
So barring Air India ignoring ADs, that aircraft should have been in compliance by September 2021. And as noted in another comment, there's fuselage drains to mitigate any buildup of water.
Again to be clear, not saying it cannot be a factor, but these ADs don't automatically apply to every aircraft.
ProgressEquivalent50@reddit
Perhaps. However, the fact that there were two separate (but related) issues mentioned in the AD, indicates a potential systemic problem with water entering the EE bays and mistakes by Boeing around that.
Despite knowing about water ingress risks since 2016, Boeing still had a documentation error in 2018 that recreated the same hazard:
2016: Boeing discovers water can leak into EE bays, issues fix (AD 2016-14-04)
2018: While "streamlining" documentation, Boeing accidentally removes the very instructions meant to prevent this known problem
2024: Boeing discovers they've been building planes without proper sealing since 2018
ProgressEquivalent50@reddit
Also, if you look at the leak from the overhead bins on an Air India 787 Flight out of Gatwick, there is a LOT of water (not just a minor leak). https://www.instagram.com/speedbirdhd/reel/DLKS7UnxfJV/
railker@reddit
Oh no, definitely not a minor drippage. But it'd be the first aircraft I've seen that's made the design decision to route potable water lines above the ceiling.
More likely per previous discussions on that video and similar events, it's just condensation, not a leak. Yes, it can get that bad. No, it shouldn't. Apparently from the comments one of the plane's nicknames is the 'Rainliner', the higher humidity in the cabin is a feature until you forgot your umbrella I guess. 😂 And as you can imagine flying in and out of a place like India an aircraft might be prone to that. Happens on other aircraft, too.
https://www.reddit.com/r/aviation/comments/5rwfzk/condensation_issue_in_787/
https://www.reddit.com/r/aviation/comments/1ayou0u/787_dripping_water/
I think about one liter of water passed into the cabin in a period of perhaps a minute.
ProgressEquivalent50@reddit
I'm not saying a single short caused all the power to shut down. What I'm saying is that it is possible that water causing multiple simultaneous electrical equipment failures in the electric bay could have led to an unanticipated sequence of events that led to engine rollback.
Brief-Visit-8857@reddit
The whole point is that it’s not supposed to happen. The engineers think of these scenarios, especially something as simple as a water leak.
ProgressEquivalent50@reddit
The FAA Airworthiness Directive indicated that installation flaws with the water sealant has in fact allowed instances where water entered the EE bay which wasn't supposed to happen. In fact this AD requiring inspection went into effect only 1 week after the crash. And the AD specifically says "A water leak from an improperly installed potable water system coupling, or main cabin water source, if not addressed, could cause the equipment in the EE bays to become wet, resulting in an electrical short and potential loss of system functions essential for safe flight." So yes, it is a flaw that can in fact happen and cause significant damage
Brief-Visit-8857@reddit
If the AD was issued, then it was fixed, or necessary actions have been taken to prevent this from happening. All 787s were found in compliance with all the ADs
ProgressEquivalent50@reddit
Nope. The AD went into effect June 18 -- 6 days after the crash. It is newly issued.
Brief-Visit-8857@reddit
I don’t see anything about the AD that states that it will result in a potential loss of essential systems for flight
ProgressEquivalent50@reddit
This is a direct quote from the AD (page 8): ""A water leak from an improperly installed potable water system coupling, or main cabin water source, if not addressed, could cause the equipment in the EE bays to become wet, resulting in an electrical short and potential loss of system functions essential for safe flight."
ProgressEquivalent50@reddit
It also says "This AD was prompted by reports of water leakage from the potable water system due to improperly installed waterline couplings, and water leaking into the electronics equipment (EE) bays from above the floor in the main cabin, resulting in water on the equipment in the EE bays"
mrstarfish3@reddit
Could it be an engine failure due to birds strike?
MortimerDongle@reddit
Unlikely, there would typically be some more obvious evidence of that.
Thesalutaryhaptic@reddit
The day after accident I was absolutely hammered on a now closed thread for suggesting massive electrical issue leading to Fadec failure (and all the compelling evidence that backs this up). Now I see today it’s finally being put forward seriously as a possible cause
Convinced Fadec issue is reason behind crash but it’s not what air India or Boeing will want as the cause, as it’ll ground some if not all 787s for sure.
Brief-Visit-8857@reddit
If that was the cause, I think it’s in their best interest to ground the plane. I also definitely think this was a sort of catastrophic electrical failure that somehow messed with the 787’s sensors and software.
Thesalutaryhaptic@reddit
Or make a directive not to retract landing gear until much later
Snuhmeh@reddit
I've not seen any reason to believe any of this. Even if the engines somehow shut down, they would've been still spinning down and generating some electrical power.
Brief-Visit-8857@reddit
I found this, take it with a pinch of salt. It could be possible that FADEC was not the issue here, but something else: https://www.reddit.com/r/aviation/s/xUXxeyDpbK
Thesalutaryhaptic@reddit
That’s a very interesting theory actually. Was convinced it was FADEC going into idle but this also makes a lot of sense. Since the plane already had serious electrical Issues knocking out aircon etc I’m guessing an Indian electrician was bodging a fix after landing.
Blythyvxr@reddit
Please share the compelling evidence that backs this up.
Independent-Mix-5796@reddit
I’m seeing a lot of people speculating that this tragedy could have been “caused” by a TCMA issue. It needs to be stated that even if we find that TCMA was somehow activated after takeoff, the TCMA would not be the cause but rather the outcome of a multitude of other causal failures.
As far as I know, the TCMA can only activate if it detects an uncommanded high thrust and the airplane is on the ground. This translates to the failure of two separate control paths: 1) A failure in the FADEC in misinterpreting engine thrust command. Per DAL-A this probability must be less than 10^-9 failures per flight hour. 2) A failure in the plane’s altitude and weight-on-wheels (WOW) logic. AFAIK TCMA logic is only supposed to activate only if at least one radar altimeter and one WOW sensor indicate that the plane is still on the ground; assuming both are DAL-B systems, the failure rate of this logic should be in the ballpark of 10^-14 to 10^-13. Note that the probability that the FADEC receives a perfect false positive through a random bit flip or flips is also virtually impossible without component failure as well since ARINC protocols have a built-in error checking mechanism.
All in all, the combined probability of failures in both control paths simultaneously happening and thereby causing a dual engine shutdown is impossibly small… in normal conditions. The part I’m not seeing mentioned in discussions about the TCMA theory is that TCMA activation almost guarantees that there is systemic gross negligence in Air India’s maintenance, and that the real root causes would be take much longer to untangle.
SliceMountain6983@reddit
A faulty weight-on-wheels input into the TCMA could have triggered some unforeseen corner case that resulted in TCMA bringing the engines back to idle.
Note that the gear failed to retract. Step 1 of 787 gear retraction is the main gear doors swinging down, which clearly never happened, per the rooftop video. An "on wheels" WoW signal would inhibit gear retraction.
Mr_Tiggywinkle@reddit
Isn't the focus on TCMA a bit weird anyway, as there are other fault paths for the EEC to trip?
Like, its the FADEC shutting down the engines generally that's a possibility, not TCMA specifically.
ChillFratBro@reddit
Yes. TCMA is people who don't know what they're talking about zeroing in on a red herring to try to sound smart. "Just asking questions" about TCMA and then turning around arguing with someone who tells them why that's an extremely unlikely cause is a dead giveaway the person is both irresponsibly speculating and ignorant.
DrSpaceman575@reddit
We know that whatever happened has to be extremely unlikely already though. It's not like this is a common error, whatever it is.
TCMA has malfunctioned in 787's before and caused an unrecoverable dual engine shutdown, but they were landing so fatalities. It's definitely not the least likely possibility at this point.
ChillFratBro@reddit
TCMA has not malfunctioned before. That is a false statement. TCMA has acted properly to shut down the engines when a pilot applied the thrust reversers at too high a throttle point while the plane was on the ground decelerating after touchdown. That is something Boeing explicitly said not do do on a 787.
You're allowed to disagree with the design decisions, but you're not allowed to just fucking make shit up. There are NO documented incidents of TCMA not working as designed. Whether or not you like the design has no bearing on if the system works as designed.
It could be TCMA, but not because there's any concerning history with that system - only because that is a system that could interrupt the flow to the engine if about 5 other things also went wrong first.
Emotional_Two_8059@reddit
TCMA must only trigger on uncommanded high thrust, shouldn’t have anything to do with pilot inputs.
ChillFratBro@reddit
Where do you think the commands come from? In this context "uncommanded" means different from pilot inputs.
Emotional_Two_8059@reddit
Uncommanded, as in deviating from the throttle position FOR A WHILE! Of course if you move the thrust levers very quickly, the engine response will lag behind. Hence why there is a thrust contour to account for the response time.
I never read anything about the engines malfunctioning. It was a logic fault in the TCMA. It should only trigger in a runaway turbine scenario where it is stuck. It is 100% not there to correct any of the pilot inputs.
DrSpaceman575@reddit
It functioned normallly when it shut down the engines and they were unable to restart? If it’s not an intended function, it’s a malfunction. Doesn’t matter if it followed its own logic, it wasn’t intended to happen but it did. Whatever you want to call it.
“Not allowed” is funny, this is a Reddit thread not the Air Force
ChillFratBro@reddit
It was intended to happen in that case. TCMA watches the measured thrust vs. commanded thrust, and shuts down fuel flow if measured thrust greatly exceeds commanded thrust while on the ground. That happens if you deploy thrust reversers too early. I am telling you that is precisely the intended function - so correct, that is not a malfunction.
For TCMA to have been the cause of thrust termination on this flight, it would have to be told that the pilots had set the throttles to idle and that the plane was on the ground. TCMA cannot act unless it receives both of those inputs (from redundant systems). Obviously, the plane wasn't on the ground; additionally, no reports indicate the pilots cut power.
Even if I accept your premise that TCMA is the proximate cause to loss of thrust, it would have to have received multiple points of bad data from other systems independent of both TCMA and each other. The airplane believing it's in a wildly different flight regime (on the ground taxiing) than it is (taking off) would be the root cause, not TCMA - because the condition of the airplane believing that it's doing something it isn't will lead to any number of catastrophic failures as systems start freaking out.
"But TCMA!" cannot be anything other than ignorance from people who have no fucking clue what they're talking about. If you really think TCMA cut fuel flow to the engine, start asking how it might have received bad inputs. Start asking how every flight computer started to believe the plane was in a regime of flight it obviously wasn't. If you come up with a credible sequence of failures that could lead to that, maybe you're on to something.
Powerful-Ad2338@reddit
Let's not forget what happened to the Jetstar 787. The fuel servo valves got clogged with debris. If you jam up these valves (doesn't have to be Kathon like the Jetstar incident) you can cause the thrust rollback. The Jetstar incident is eerily similar to AI 171
https://jtsb.mlit.go.jp/eng-air_report/VHVKJ.pdf
Brief-Visit-8857@reddit
No, the survivor said that he “felt” like the engines were thrusting up, he didn’t hear it. That could easily be gravity, falling down feels like “thrusting up”
Brief-Visit-8857@reddit
To add to this, in the video you don’t hear the engines thrusting up at all at any point right up until the massive fireball
laymyan@reddit
The nose was pointed up, so when he “felt” the thrust, it could be that he meant he was again pinned down to the seat (like in the case of a t/o). Nevertheless, more clarity is required to be certain.
Brief-Visit-8857@reddit
IIRC there’s no FADEC on the 787, it’s a EEC. Basically the same thing, just clearing it up so people aren’t confused
Mr_Tiggywinkle@reddit
I thought EEC was a component of an overall FADEC system. EEC is a specific hardware unit, FADEC is the system (that includes the EEC as its main part).
Brief-Visit-8857@reddit
Didn’t know that! Thanks for educating me
Independent-Mix-5796@reddit
You're correct, Safran manufactures the FADEC for the 787 GE engines: Safran's contribution to the BOEING 787 DREAMLINER | Safran
Powerful-Ad2338@reddit
Let's not forget what happened to the Jetstar 787. The fuel servo valves got clogged with debris. If you jam up these valves (doesn't have to be Kathon like the Jetstar incident) you can cause the thrust rollback. The Jetstar incident is eerily similar to AI 171
https://jtsb.mlit.go.jp/eng-air_report/VHVKJ.pdf
Chen932000@reddit
TCMA is to cover a case where throttles are low and power is high. If TCMA believed the throttles were low (needed before it can trigger) it means the FADEC believed the throttles were low. If the FADEC believes the throttles are low though, that alone would have the FADEC cutting power. You dont need the rest of the TCMA logic to trigger at all for it to be a catastrophic situation.
Independent-Mix-5796@reddit
Besides the fact that that interpretation still only explains the outcome and not the root cause(s) of the accident, that interpretation fundamentally misunderstands TCMA functionality. Here are paraphrased sections directly from the patent for TCMA with bold emphasis mine:
(link: https://patentimages.storage.googleapis.com/11/c0/6b/6dcf993795046a/US6704630.pdf)
The patent makes clear that engine cutoff by the TCMA is a very deliberate action. In the case of Air India 171, for the TCMAs (plural) to have triggered there needs to be faulty signals from all four EECs (two on each engine), the throttle command, a radar altimeter, and a wheel sensor over a length of time, simultaneously.
RalfrRudi@reddit
Do we know how the redundancy of the signal from the throttle command to TCMA works?
Because while it is virtually impossible for all systems to fail at the same time, it doesn't sound like that is what needs to happen.
Scenario:
The "on ground" signal might be correct, because the plane is still on the runway, the "high thrust output" signal might be correct because we are mid take-off. Now all we would need is the TCMA to belive the throttle position to be idle and all criteria for engine shutdown are met.
Chen932000@reddit
It would need the TCMA part of the FADEC to think the throttle was at idle but it would also need the actual power governing part of the FADEC to think the throttle wasn’t at idle. If the whole FADEC thought the throttles were at idle it would pull the power back to idle. So you don’t need any of the TCMA stuff for this to be an issue. Its just quad throttle failure (both channels of both engines reading erroneous idle positions for the throttle). That is exceedingly unlikely (I would guess at least order 10^-12 if not lower like 10^-16 or even -20)
Emotional_Two_8059@reddit
The other option is a throttle sensor disagreement between channels. The rest of the FADEC will detect the disagreement and keep thrust high. The TCMA of the channel that reads the erroneous idle throttle position will trigger
Chen932000@reddit
My understanding the TCMA logic resides in the FADEC and would detect and accommodate the mismatch in the same way the rest of the FADEC control does.
Emotional_Two_8059@reddit
Ok, I hope sooo.
Emotional_Two_8059@reddit
According to the patent document, each channel can trigger the relay to shut down the engine independently. You just need a single throttle position error per engine while still on the ground. Rest of FADEC will detect throttle position mismatch between channels and power through. The TCMA of the channel connected to the faulty throttle showing idle will trigger as the thrust doesn’t decrease as predicted by the contour.
David905@reddit
3 things: 1) that part of the patent says 'Software package 130 only cut fuel while on ground..'. It doesn't preclude other parts of the design from possible cutting fuel while in air. 2) it is known to have happened to another 787 during flight, so clearly the TCMA can result in unexpected engine power loss in flight 3) we don't know for sure whether the power loss of AI171 occurred in flight on on ground
Independent-Mix-5796@reddit
My critique right now of the TCMA theory right now is that it is not a neat theory by any means, but rather an open-ended guess that presents a very, very messy can of worms.
David905@reddit
My thinking is more along the lines of this being likely software related. The simultaneous shutdown (lack of yaw), lack of smoke or apparent sputtering, combined with history of software issues (not just Boeing/787's, software everywhere in every industry) to me points to high likelihood of software rooted issue here.
You're right- the history of TCMA shutting engines was after on ground. The fact that it did result in unintended shutdown points to bugs however. We know the TCMA routine has an 'output' that results in engine shutdown, and it has happened unintended before in different circumstances, so it would seem to be a leading candidate on the software-rooted issues side.
Who knows.. maybe the whole engine control system simply BSOD'd at the worst possible moment..
Independent-Mix-5796@reddit
I mean, by the nature of the 787 being a fully fly-by-wire plane this crash certainly involves software, but it’s inconclusive if the issue is directly a software bug (that is, errors resulting from anomalous bit flips), a design blind spot, a failure in an adjacent system, or some combination thereof.
Again, I don’t dispute the possibility of a TCMA activation in the case of AI171, but that’s not the root cause of it. We still need to figure out where in the decision-making tree caused both TCMAs to activate.
To give a similar example: in February of 2018, SmartLynx Estonia flight 9001 suffered a flight control failure caused by failure of all ELACs and SECs. The actual root cause, though, was that the lubricating oil used in pitch trim microswitches was too viscous, resulting in the failure of those computers to read pilot input and enter the flight control lockout state. Going back to Air India flight 171, I’m still looking for the metaphorical lubricant that’s the cause of a hypothetical TCMA failure.
Emotional_Two_8059@reddit
Unlike the rest of the FADEC, from the patent papers at least it seems that the TCMA logic running on each channel has the authority to cutoff the engine independently.
So if there is throttle position sensor disagreement (one sensor is wired to one channel), the rest of the FADEC will detect it and keep thrust high. But the TCMA of the channel which get the false idle throttle position will trigger after a bit.
Now what are the chances that one throttle sensor per engine errored to close to idle power at the same time, on rotation? Quite low
Chen932000@reddit
The usual accommodation for a mismatch between channels would be for both channels to use an accommodated value (for throttle likely the higher value). Now there is certainly a possibility of both channels just using their own value but that leads to less deterministic operation which is why it’s less common (particularly if there’s no 3rd signal to use as tie breaker. Having both channels use their own throttle input as valid even in a mismatch is asking for huge issues. Example: active channel reads high throttle and passive channel reads low throttle. Something relatively benign happens that forces a channel switchover. Now instead of a normaly seamless transfer you have a complete reversal of the throttle on the engine in addition to whatever came about from the switchover.
NorthernEwan@reddit
Does the probability of FADEC failure include the Airworthiness Bulletin to change the FADEC due to defective solder joints? There is also another on to update the software.
Emotional_Two_8059@reddit
You’d need to have broken solder joints on both channels of both FADECs, so 4 points of failure simultaneously. Otherwise a single healthy channel of a FADEC would ~hopefully~ default to “keep flying” and maintain last good thrust command or similar
NorthernEwan@reddit
Yeah, fair point. They are pretty independent including their power supply.
Independent-Mix-5796@reddit
Bulletin or directive? If it’s a bulletin then generally yes, probability is likely unaffected because bulletins are non-mandatory recommendations that generally notify of a product improvement. If it’s a directive, then probability of failure is dependent on if said directive is implemented correctly.
NorthernEwan@reddit
Yeah it’s a bulletin:
GE Service Bulletin SB 73‑0097 R02 / FADEC International SB FADEC3/73‑092 (July 2021) • Involves hardware-level modifications to the FADEC’s main-channel board (BGA microprocessor MN4). • Addresses issues such as solder joint degradation that could result in loss of FADEC control (e.g., frozen at idle instead of flameout)
There are also a few others that are interesting:
Boeing Thrust Management Software Bulletin – B787‑81205‑SB340053‑00 RB (Issue 001; Nov 16, 2022) • Requires installation of updated thrust management software (Block Point 4.1) to correct erroneous thrust commands during critical phases like takeoff . • It’s linked to FAA AD 2024‑16‑07, reinforcing its certification and regulatory relevance.
FAA AD 2023‑10‑02 / AD 2023‑12‑10 (effective June 18, 2025) • Mandates radar altimeter upgrades to mitigate 5G interference, ensuring reliable autothrottle and FADEC performance . • Potentially relevant, since degraded FADEC/auto‑throttle behavior during takeoff can contribute to synchronization issues.
Some1-Somewhere@reddit
You need a third thing to go wrong. If it was just the engine misinterpreting the requested thrust from the pilots, then the engine would roll back to idle and sit at idle.
TCMA activation implies:
Both engines were told the aircraft is on the ground
The TCMA portion of the FADEC thought thrust set was near idle or reverse
The rest of the FADEC was controlling the engine to deliver takeoff thrust, presumably because it thought the crew wanted takeoff thrust.
Emotional_Two_8059@reddit
This can actually happen if you’re still on the ground and one of the two throttle resolvers is misinterpreted as idle. Each FADEC channel’s TCMA logic can shut down the engine independently. They don’t have to agree. If there’s a throttle sensor malfunction, the rest of the FADEC logic will detect the disagreement between the two channels and keep last valid thrust level. At some point the TCMA with the faulty reading/interpretation will trigger.
Some1-Somewhere@reddit
Yeah, I thought of that sometime later.
It still requires both engines to have exactly one of two throttle resolvers fail, in the same way.
Emotional_Two_8059@reddit
Yeah. That’s quite unlikely. Or all 4 fail/short. Just need one per engine to be interpreted as close to idle. But then for it to also happen close to rotation… what are the chances?
Heiter-Sama@reddit
But it has happened before on landing in 2019.
It could have happened still on the runway after V1 and it wouldn't require any failure of altidude or WOW reading, only some combination of throttle/thrust reading or setting errors.
NigroqueSimillima@reddit
Please stop repeating this, TCMA is only on RR engines, not the GENx that were installed on Air India
https://www.scribd.com/document/864763320/1-B787-Bulletins
Emotional_Two_8059@reddit
TCMA or similar logic is mandated by the FAA, it’s not something optional that RR baked in. Of course there might be different FADECs between RR and GE and potentially different microarchitecture/codebase. But the concept is the same
Independent-Mix-5796@reddit
“Only” is doing a lot of heavy lifting here.
David905@reddit
Exactly. If TCMA happened during a flight, then clearly it IS capable of triggering in a case other than on the ground.
Not only that, but the documentation I've read on it clearly states that it is intended to be functional during takeoff and landing. So why all the myths that 'it can only occur if both wheels are on the ground so cannot possibly be the case'.
Heiter-Sama@reddit
With how little velocity 171 had, the shutdown might still have started on the runway even
LantaExile@reddit
That seems unlikely watching the video. It climbs normally for about ten seconds before the power is cut.
gargeug@reddit
I have a theory that a congested AFDX network could cause the dropping of network packets or real-time requirements, and that is why early on researchers were not recommending it for use in life critical systems.
The biggest risk being the fiber optics. They can only mate like 200 times in their life, and foreign contaminant during unplugging can seriously degrade that fiber. Remember there was a video showing that plane's entertainment system going haywire. What if a tech went and unplugged and replugged in some of the fiber to fix it, but hosed some of the fibers. The network throughput could get pinched, even with routing redundancy because throughput is throughput. And those entertainment systems use the same fiber data switches as the flight control systems, a poor poor choice IMO.
Suppose the network was seriously degraded and at 100% utilization because of fiber loss, researchers show a 1.6% packet loss in that situation. If some of those losses were things like Wheels UP, or feedback from the thrust levers, the TCMA could get itself in a situation where it thought it was still on the ground, but the higher priority engine data was arriving on time and showing higher thrust than was commanded due to packet loss of WoW or lever. The controller could make the decision to kill the fuel to both engines because the wheels and thrust control are common inputs to control both engines.
Just a theory. But to me this whole thing, it if is a bug, sounds like a race condition which notoriously produce those super rare, unforeseen glitches like this could be. And it is hard because if you let the thrust keep going waiting on the other packets, you risk thrust runaway. So perhaps in that corner case they decided to protect the engine, not realizing this case could occur as a valid option to protect against.
DrSpaceman575@reddit
The TCMA has failed before on a 787 during landing. Wasn't a big story because no deaths but they were unable to restart the engines and had to be towed off the runway. So the idea of TCMA causing an unrecoverable dual engine shutdown on a 787 is not only possible but has happened previously.
For the #1 failure condition to be met I don't think the only possibility is FADEC error. There could be an inciting problem we don't know about that resulted in the throttles being pulled back or reverse thruster mistakenly being engaged. Could be entirely accidental even but timed unfortunately enough that it coincided with the plane believing it is on the ground.
Independent-Mix-5796@reddit
Landing isn’t the same as a takeoff, though. As far as I know, the JAL TCMA activation was caused by a too-fast full thrust reverser command, followed by a quick deactivation of reverse thrust. The FADECs interpreted this as an uncommanded high throttle command and thus shut down both engines.
For a similar scenario to have happened for AI171, the implication would be either 1) that the pilots, for whatever reason, were trying to reject takeoff — why else would they rapidly command reverse thrust or at least engine idle on takeoff? Or 2) that as you said (and as I was trying to convey with my initial comment) there are multiple other system failures that resulted in a fatal TCMA activation.
Lithorex@reddit
Given enough time, the likelhood of an event with a chance >0 occuring will converge on 1.
KingInTheFnord@reddit
But the time to reach any meaningful probability could be longer than the age of the universe.
Lithorex@reddit
While that is true, sometimes the dice just rolls for a disastrous outcome.
I wonder what peoplewould have argued to have happened in TAROM 371 if the internetnback then would have been around like it is now.
Admirable-Essay-6770@reddit
This, right here, is where one can spot the difference between a theoretician and an engineer.
Tiny-Plum2713@reddit
enough could be millions of years.
Lithorex@reddit
Could
Tiny-Plum2713@reddit
Yes. Which is why your statement is meaningless.
anon568946@reddit
That's right, never stop gambling
Emotional_Two_8059@reddit
What if TCMA activated just when the wheels were still touching, but engines took a second to roll back so the plane could still take off, just trading off speed for altitude, which is why it started descending right after? We’re now down to one fault needed (replicated in 2 FADECs)
Independent-Mix-5796@reddit
I came to the same guess myself, but I still can’t explain why then that both TCMAs would fail simultaneously.
Emotional_Two_8059@reddit
Because they both run the same code :) If it’s a bug in the code and the inputs/states are the same, it will manifest on both. That’s the problem with software…
A good example is the Generator Control Unit (GCU) bug that was discovered on the 787 previously. All 4 GCUs had an uptime counter, and assuming they power up at the same time, plus or minus some seconds, they would all go to fail-safe mode within seconds of eachother, after 248 days, where these uptime counters would overflow. So with just one small bug, you annihilate a 4-way power generation redundancy :/
Independent-Mix-5796@reddit
Ignoring the fact that not all software is built to the same standards (especially DAL-A software), just calling this “a bug” isn’t a satisfactory explanation. Is it an inherent design flaw in the way that the power threshold is calculated? Is there a simultaneous, identical, and perfect corruption of memory on both FADECs? Or was there a system failure of elsewhere on the plane that lead to a simultaneous state misinterpretation by the TCMAs? And if so, why wasn’t there sufficient warning of any erroneous conditions prior to V1?
Emotional_Two_8059@reddit
Man, tough to say if you’re not Boeing and have access to the code.
It might be that both engines for some reason went outside the performance envelope expected by the TCMA (there is some margin there, as there is some delay in the turbine response). What are the chances that we’ve only hit this edge case only once after 15 years of operation, and both engines had the same response?
I also have no idea if the TCMA has an upper limit on requested thrust where it engages (so it doesn’t engage on takeoff).
From what I understand, the engines just going to idle would not auto-deploy the RAT?! So just a few systems can completely kill the engines. TCMA being one of them.
There aren’t many other plausible scenarios… One that would also fit is if captain or FO just killed both engines and played along :/
Independent-Mix-5796@reddit
It’s likely not obvious even if you do have access to the code.
I think it’s a mistake to just look for plausible scenarios when this tragedy is implausible to begin with. TCMA sounds plausible but in my professional opinion I honestly don’t know if it is any more plausible than other possibilities.
turkishguy@reddit
The TCMA dialogue is likely being pushed because of the ANA 985 incident. AFAIK there are no public reports that specifically state why the engines shut off on that flight but it seems to be plausible that something related to the TCMA malfunctioned there and possibly here. It's also compounded by the fact that Boeing released bulletin shortly before that ANA incident.
You're right though - the TCMA is just a failsafe. Something else would've needed to fail for it to kick in. It's just a question of what that could possibly be.
gkfisher@reddit
OK, that’s really interesting so then…… What was it? Sabotage?
Rupperrt@reddit
was probably not TCMA then.
Accomplished_Mark343@reddit
Where are the engines? It should be relatively easy to look at the engine wreckage and see if they were turning/under power at impact. Seems like forward of the tail is just a black stain and completely obliterated but the engines I would think would be lying around the crash site.
Brief-Visit-8857@reddit
I think they were lodged inside one of the residential buildings. Not sure
Accomplished_Mark343@reddit
Yeah I think you are right. In one of the photos of the tail there is a building with round hole punched through it. Wonder if one in on there?
jofrevic@reddit
Can someone explain why this 787 seems to have 2 tails?
This one
https://www.columbian.com/news/2025/jun/18/air-india-faces-turbulence-as-plane-crash-prompts-deeper-checks-and-disruptions/
And this one
https://www.columbian.com/news/2025/jun/18/air-india-faces-turbulence-as-plane-crash-prompts-deeper-checks-and-disruptions/
jofrevic@reddit
Siorry second is
https://www.columbian.com/news/2025/jun/17/boeing-airliners-chief-stephanie-pope-headed-to-india-after-787-crash/
Brief-Visit-8857@reddit
They removed it with a crane. The second picture is after it was removed from the building it was lodged into.
jofrevic@reddit
Thanks, I think it is still in same place, the picture from above looks as if it is on the ground, but it is still on the building. Really confusing. See the answer above from a smarter or much better observer than me.
Beneficial_Long_6280@reddit
Because one is bottom view from ground and the other is top view.
jofrevic@reddit
Thanks, yes I see it! (My bad).
Tough-Candy-9455@reddit
I think you are talking about the horizontal stabilisers. They (and elevators, which are part of them) help stabilise and control the aircraft in the pitch axis, as in makes the plane climb or descend.
jofrevic@reddit
Yes, but they look double? Please se my reply to myself with second picture as I mistakenly posted same pic twice.
railker@reddit
Something to add I haven't seen noted yet:
The Boeing 787 comes with two engine options, GE and RR. There's been much discussion about the ANA 787 shutting down both engines after landing due to a fault in the TCMA system (Thrust Control Malfunction Accommodation).
ANA's 787s have RR engines. Air India has GEnx. The Transport Canada MMEL section for Engine Fuel and Control specifies (RR) beside the line for the TCMA system, and a Google Search struggles to bring up results with both of those things together.
Anyone able to correlate that the TCMA isn't even a system on 787s with the GEnx-1B?
Some1-Somewhere@reddit
It's been reported on PPRuNe that it become mandatory around 2005 ish, and everything from the GE90-115B onwards includes it, from any manufacturer.
Brief-Visit-8857@reddit
So not just the RR engines?
Some1-Somewhere@reddit
No, the person on PPRuNe was involved in the development for the GEnx-2B on the 747-8.
railker@reddit
Good catch, and thanks for all your inputs, you've been amazingly helpful with sharing knowledge for this entire speculative carnival. 😁
fugutoxin@reddit
More of a philosophical question here - I always had the impression that Boeing’s unofficial motto is that the pilot is the final authority in operating the aircraft (in contrast to Airbus and MCAS notwithstanding). But there is no manual control mode that a pilot can revert to if the FADEC fails, nor is there the option to shut it off. I understand the high-levels of redundancy built into the system, but the idea of a completely autonomous, self-monitoring, and self-operating system which a pilot can neither manually override nor turn off in a very rare scenario seems contrary to Boeing’s fundamental design philosophy.
railker@reddit
I do believe there's reversion even for that, above the start switches there's alternate EEC mode that can automatically engage or be engaged by the pilots. I understand it's a little like going into direct mode/law with your flight controls, it takes the restraints away and lets you have more direct control with the throttles.
fugutoxin@reddit
Thank you. I doubt that’s something taught in the simulator or even recommended as a last ditch effort when facing dual engine failure right at takeoff. But perhaps it should be. As a pilot, you should be the final arbiter of what the engines are doing. The pilot’s mayday message may be telling - “Thrust not achieved”. That sounds like a command that was given but not carried out by the aircraft.
ABoutDeSouffle@reddit
It seems like this was made up and the pilot only radioed mayday.
fugutoxin@reddit
Can you provide a verified source for that?
ABoutDeSouffle@reddit
No, neither can anyone claiming the “Thrust not achieved” part. It only can be verified after the official inquiry.
fugutoxin@reddit
But if you have no basis to say that this was made up, how can you make the claim you’re making?
ABoutDeSouffle@reddit
Across this tread and the ones before, quite a lot of people cite sources. They are not verified, but they state that nothing was added to the mayday call.
You did not give a source for your claim either.
fugutoxin@reddit
Wait, didn’t you say that the pilot only radioed the word “mayday”?
railker@reddit
Closest lead I've got is this tweet from one of the journalists that initially reported that. There is no official verified source of the thrust loss call, seems someone claimed it and that's obviously sensational so everyone ran with it. But we can still be proven incorrect yet.
fugutoxin@reddit
Ah, I see, thanks. So he may have said nothing, he may have said only mayday, or he may have said something more. It doesn’t look like Ahmedabad Airport is part of Live ATC so no chance a member of the public was listening at the time.
railker@reddit
Here's an image posted by Airways Magazine of a supposed initial statement from the DGCA, referencing there was a mayday call but no quotes. Last I checked, couldn't find an official copy, seems one of those statements that's kinda given out to media but not on a dedicated page on an official site we can point to. Which makes it hard to 100% verify.
Some1-Somewhere@reddit
It's in the manuals and is apparently not too uncommon a failure.
The EEC will drop itself into that mode if it deems necessary. Usually as a result of sensor or actuator failures.
It mostly just removes the engine protections against overboosting. It doesn't seem likely to be implicated here.
fugutoxin@reddit
It’s not uncommon for FADEC to drop into alternate EEC due to sensor or actuator failures? Do you know why that is (I’ve heard the 787 has a history of electrical problems)? Is this reversion anything akin to normal law versus alternate law in an Airbus?
Some1-Somewhere@reddit
Not uncommon as in can happen from time to time. Not a 787 issue.
Kinda sorta like alternate law but internal to the engines.
Note the same thing happens to engines on Airbus aircraft.
fugutoxin@reddit
Ok, gotcha. Just so I’m clear, there is no direct law reversion for any engine type on any Boeing, Airbus, Embraer, etc. aircraft?
Some1-Somewhere@reddit
It's not really the same thing. Normal/alternate/direct or similar is flight control computers.
If by direct law you mean throttle lever position equals fuel valve position, I don't think you've ever been able to do that on a commercial jet engine, even back to the 50s and hydromechanical controls. Engines are too unstable and the risk of over speed and catastrophic failure is too high.
RealPutin@reddit
1997 actually, but yes. HZ-AGM, Saudi Arabian Airlines.
The Uncontrollable High Thrust reg often has some approved minor deviations (787 and G650 both had some notes off the top of my head), but yeah, it's been a design requirement for a while and I know of it in RR, GE, and CFM engines in various sorts on both Boeing and Airbus frames
Brief-Visit-8857@reddit
Wow. That’s very interesting! Thank you
bicycles_sunset@reddit
Regarding the loud bang/noise supposedly reported by the survivor, are any of the items that cause automatic RAT deployment associated with a loud noise consistent with his report (including timing)?
theOJgotSqueezed@reddit
New here but just wanted to say this tragedy is truly awful. I’ve been thinking about this quite frequently. Almost 300 souls lost yet social media is filled to the brim with grifters exploiting this event like there’s no tomorrow.
From people making inappropriate comments about the deceased, to deceitful AI videos to farm engagement. The nonsense speculation from ‘experts’, when we really don’t know anything until the reports are out. It achieves us nothing.
I just can’t imagine what the passengers must’ve felt. May they rest in peace
SelfPsychological214@reddit
I honestly think it's racism. If it were 300 Americans who died instead there would be a completely different atmosphere. Just like when Boeing tried to blame foreign pilots for one of those 737 MAX crashes.
Difficult-Anybody405@reddit
Especially the children. The pain they must have felt. I hope it was a sudden death and they didn’t had to endure the burning. My heart aches for them 😔
DifferentManagement1@reddit
I’m glad the only place I read about this accident is here. This sub and this thread are fantastic - the subject is handled with intelligence and respectful curiosity
nguyenm@reddit
On Facebook in particular, there's been some fake news circulating about the existence of a preliminary report already by this date, as well as the probable cause being tied to the seat railing. As I mentioned, this is all untrue and is likely a product of an LLM given the syntax and use of emojis.
This hoax refers two completely made-up references: "Emergency AD 2025-16-51" and "Boeing Service Bulletin “787-25-123”.
External_Weird_8251@reddit
Ah LLMs...we need better AI literacy
turkishguy@reddit
Fake news didn't start with LLMs. People are just stupid.
kussian@reddit
Always has been
Sea-Us-RTO@reddit
yeah someone should make an AI for that
Existing-Help-3187@reddit
Its this one. Emojis and all in AAIB report lol.
AI 171. Posted as received. Still to be verified but it looks like a catastrophic electrical failure on rotation.
Flight: AI-171 | Aircraft: Boeing 787-8 | Date: June 25, 2025 | Route: Ahmedabad (VAAH) → London Heathrow (EGLL) Crash Site: ~1.2 km from VAAH Runway 23, post-V1 and rotation Fatalities: 247 (243 onboard + 4 ground) Survivors: 1 onboard survivors (alternate to original), 3 injured on ground
🛠️ AAIB Preliminary Report Highlights
Primary Cause – Electrical Power Transfer Interruption (PTI) During Rotation • During transition from ground to airborne electrical configuration, the aircraft experienced a cascading dual-engine FADEC (Full Authority Digital Engine Control) failure. • Root cause: Uncommanded bus transfer failure due to arcing in the main power relay box (PRB-A), traced to water ingress during pre-flight GPU disconnection in heavy rain. • This led to loss of electronic engine control at rotation, resulting in both GEnx engines rolling back to ground idle within 4–5 seconds.
Flight Data Record Timeline • +0:11 sec: Nose gear lifts off. • +0:13 sec: Sudden engine rollback begins. Thrust reduces from 92% N1 to <27% within 3 seconds. • +0:16 sec: Master caution + ENG FAIL L/R warnings. FO calls, “Both engines dropping!” • +0:20 sec: Autopilot and flight control reverts to Direct Mode. Pitch up attitude peaks at 18°. • +0:25 sec: Aircraft stalls at 186 ft AGL. • +0:30 sec: Full aerodynamic stall; nose drops rapidly. • +0:38 sec: Ground impact at 54° nose-down attitude, 174 knots.
Contributing Factors • Environmental Conditions: • Torrential rain during pushback. • Moisture intrusion into PRB-A connector (P/N: HLN8471) — a known corrosion-risk component. • Latent Maintenance Issue: • Power transfer relay unit showed signs of thermal damage in a previous MEL deferral 2 weeks prior. • No replacement had been conducted; aircraft was cleared under repetitive deferral. • Design Oversight: • Boeing 787 has no physical engine control backup (i.e., no direct mechanical linkage in FADEC loss scenario). • Loss of power supply to both EEC channels resulted in engine “freeze” at ground idle instead of flameout. • Flight Crew Response: • Attempted engine relight sequence not completed before stall onset. • Emergency power selector not activated — possibly due to confusion from multiple ECAM warnings. ✈️ Immediate Safety Actions • DGCA + EASA + FAA Emergency AD issued within 24 hours: • Mandatory PRB-A moisture integrity inspection on all Boeing 787 aircraft. • Temporary restriction on dispatch with MEL items related to power transfer systems. • Boeing: • Issued Service Bulletin SB-787-24-212 requiring replacement of PRB-A connectors with sealed versions. • Exploring addition of dual-path power redundancy for FADEC systems. Lessons Learned • Over-reliance on electrical power distribution architecture without layered redundancy. • Lack of crew procedural training for full engine rollback during takeoff in EEC dual failure scenarios. • Need for improved environmental sealing in GPU/electrical handover units in monsoon zones. Human Toll • The loss of 243 onboard lives, including 12 crew and 18 infants, deeply impacted the aviation community. • Final words captured on CVR: “We lost everything – no thrust!” • One family of five was killed on the ground in a hospital ambulance struck by debris. Timeline – What’s Next? • Aug 15, 2025: Release of FAA/Boeing electrical design audit report • Sept 5, 2025: ICAO session on electrical-critical phase-of-flight risk mitigation • Oct 2025: Mandated design retrofit across 787 fleet (rev. SB-787-24-219)
LoudestHoward@reddit
Official Report: 🛬🛫✈️💥
Existing-Help-3187@reddit
Lol
Not____007@reddit
Thanks man someone shared me a summary of this and it came from somewhat reliable sources so I thought maybe until I fact checked the heavy rain and then I was like doubtful. But at least with your message I can clarify its bs.
superdude311@reddit
“Autopilot reverts to direct mode” Lmao this is all such BS
carquestionno34565@reddit
It’s so stupid that your comment is downvoted to -15. Don’t people understand context?
Existing-Help-3187@reddit
Most probably the second line is throwing people off. They think its mine.
ArianasDonuts@reddit
Incorrect destinations, mentions heavy rain, and written 9 days into the future (June 25). Sounds legit.
ChrisV2P2@reddit
Just thought I'd mention here since this Captain Steeeve dude is now pushing the theory of vapor lock, here's a quote from the transcript of the video by the 787 mechanic that u/railker posted earlier:
The theory of vapor lock seems ridiculous on its face to me, the #1 risk time for vapor lock is on engine restart, but here we have the plane successfully completing a takeoff roll, during which time it cranks through something like 5,000 gallons of fuel without issue (which one would think would cool down the fuel lines, if anything), but then both engines simultaneously get catastrophic vapor lock immediately after takeoff even though they have separate fuel tanks and pumps. Not only is vapor lock on the 787 unknown, but it fits the facts very poorly.
Something that occurred to me from the video is, the mechanic mentions that one of the conditions the airplane looks for before retracting the gear is weight off wheels, which makes sense. From gear positioning it seems like gear-up was commanded, but subsequently failed. The obvious reason for this would be power loss, but maybe it's worth noting that the speculated TCMA activation and a gear retraction failure could have a common failure mode element of incorrect data about whether there is weight on the wheels. Probability is very low that I am onto anything here, but thought I'd mention it.
Blythyvxr@reddit
Vapour lock is what he’s pushing now? Fuck me the guy’s grabbing idea balls from the manatee tank.
st1r@reddit
IIRC he said the vapor lock theory was very unlikely but couldn’t be entirely ruled out yet (as of the time of recording) for XYZ reasons that he then went in depth about.
Lost-Inevitable42@reddit
I’m not sure any failure was simultaneous. Looking closely at the cctv vid, it looks like there may be a bit of unbalanced thrust. And I suspect that it gets mostly mitigated by the 787 auto controls.
Some1-Somewhere@reddit
Regardless of whether the crew or the aircraft handled the thrust asymmetry, you'd see a big rudder deflection. There isn't really one.
the4ner@reddit
Agree, especially at that relatively low speed you'd see some deflection
Brief-Visit-8857@reddit
I think it’s safe to say vapor lock can be comfortably ruled out. I don’t think it has ever happened to a modern commercial airliner. Now in regards to your theory, it’s very possible.
Proud_Engine_4116@reddit
Agreed. However I think that the real issue maybe that someone at Air India forgot to reboot the plane. The 51 days bug or the 248 day power cycle bug was ultimately responsible for this crash.
Air India has been struggling for a long time. They are trying to improve their operational efficiency and they have a terrible reputation for flight cancellation. It’s entirely possible that the 787s legendary temperament with respect to ground power quality, power on sequence etc leads to delays and they just leave the thing powered up.
Obviously I’m not trying to blame AI without evidence. Just pointing it out as a possibility.
pipic_picnip@reddit
Correlation does not imply causation.
Also you are missing an important consideration. Air India was privatised in 2022. So anything prior to 2022 while notable in and of itself, will no longer be relevant to compare in many cases such as cancellation rates. A state run airline has no incentive to provide excellence, they are simply providing an essential service required by state and it’s not like they can fail, even if state airlines are in loss they will keep getting funded from tax money as essential service.
The group that took over AI is a world known global conglomerate with a name for itself in multiple industries including a very trusted name in consumer cars and one of the most chosen heavy vehicles (trucks, trailers, buses) etc manufacturer. They have been making a lot of changes, but it’s not like you can just go and order 20 airbus from Amazon today and get a delivery tomorrow. Airline reforms take time, and not all of it is dependent on the company, there are numerous outside factors too.
I do not think with the information available so far anything definitively points to airline fault, so the odds of it happening are not any higher than any other probabilities.
Proud_Engine_4116@reddit
Respectfully I disagree with everything you have said. Those are Indian talking points designed to save face. And again, I’m not saying AI was responsible, but you cannot rule out that possibility.
As for your comment about ordering planes from Amazon, well, lol no way? You don’t say!
Thirdly: if you know India, you would realise how quickly this stuff becomes political. As someone from that country who had to leave because I was sick of the gross, wide spread ineptitude, hypocrisy, face saving etc, I’ll wait for the final report to come out.
Happy to make a bet that if AI is implicated, the Indians will arc up and start claiming racism, jealousy, “incorrect methodology” etc etc.
There have been a large number of close calls in Indian aviation and the DCGA is failing at its job to protect the flying public and those on the ground.
It’s so bad that you can’t even find their so called “offical press releases”.
Finally, I’d like to add that I’ve flown AI several times. I’ve even flown VT-ANB - and everything inside that plane was always broken.
pipic_picnip@reddit
But I didn’t rule out the possibility? I said nothing has surfaced that proves it to be more of a probability than any other causes.
It seems you just want to hear what you are intent on believing. So you do you. I am sure for every bad AI flight you have taken, there is a western counterpart who have similar criticism. Spirit airlines? The harbinger of losing luggage air canada? The infamous united airlines? So they should all be more prone to crash too because my personal experience dictates it be so. I am sorry you have bad memories of India but it’s not enough reason to add narrative to a nuanced situation.
I am not even Indian, I am Canadian and a frequent flyer so nightmare airlines is nothing new for me.
As for your bet, in these mega threads alone - there are experts who have cited that past crash reports from Indian authorities have been of satisfactory quality. Why would I believe one possibility over other with nothing to back it up except feels when precedence is pointing otherwise? Again I never denied it being a possibility, I just nothing surfaced so far that points to it being a higher probability.
Who cares if India’s feelings are hurt? I just want the truth so I know I won’t be on one of these fateful flights or at least calculate my risk before being on one. A complete anomaly of a crash is a danger to everyone. I wish I could just say “oh air India sucks let me just fly Dreamliner on other airways”. But I do not have that confidence and will not have that confidence until it is not completely ruled out the system was not at fault.
Proud_Engine_4116@reddit
Your points are valid as a Canadian who has probably never lived in India. I have a different perspective formed by living there and working closely with various different professionals.
However, we also know that there are many Indian accounts online and their only objective is to counter valid criticisms of India using gaslighting and various other techniques. So excuse me if I take what you say with a fistful of salt.
Just because it’s Tata Sons controlling AI (They created Air India to begin with before it was nationalised) does not mean they can wave a magic wand to make it go away.
There is also an issue with work culture in India which you have to live there to grasp. Once you do, you’ll realise how easy it is to falsify things, minimise harsh truths and distract from the crux as soon as possible.
And again, I’m not blaming anyone. I’m simply discussing possibilities and I’m more interested in the technical reasons for the crash. If it’s human error, then it’s human error. In that case I am more interested in how to prevent those kinds of errors in the future.
And while it’s true that we like to hear what we want to hear, I take care to reflect and retrospect. Honestly, it’s only Indians who can’t cope with facts and then attempt to gaslight everyone. By making points that skirt the periphery. Enough to register on radar but not enough to warrant action.
A history of flight cancellations is an Operational Red Flag with numerous people and well known social media personalities have called them out on.
A cursory search of decent newspapers in India about Air India is sufficient to prove my point.
Also, I don’t wish them any ill. I hope they can do better and become like they used to be, a very long time ago.
Emotional_Two_8059@reddit
248 day bug would kill all AC power until the RAT deployed, but it doesn’t explain the loss of power. The thrust lever resolvers are directly connected to the two FADECs, which have their own power generator attached to each engine shaft.
Brief-Visit-8857@reddit
Well, India’s DGCA ordered enhanced inspections of all 787s owned by Indian airlines… and found that they were all in compliance with standards. The aircraft involved in the accident was also compliant to standards before it crashed. Those standards would include the “generator bug”. I highly doubt it has anything to do with this. I regarded it as a possibility earlier on, but it won’t cause the engines to shut down, unless it affected the FADECs which I doubt.
Proud_Engine_4116@reddit
If all the generator control units shut down, and some variation of their internal CAN network being corrupted, it’s entirely possible the engine was starved for fuel. If they had altitude, they could have attempted a relight. I could be wrong, but the 787 attempts to auto-restart engines if there is a flame out.
As someone who works with cyber-physical systems, unclean power can cause some very unexpected failure modes.
Brief-Visit-8857@reddit
Let me counter your argument: In the 787, even if all generator control units shut down, the Engines’ FADEC still runs, powered by the PMA as long as the engine is still spinning. Fuel is handled by engine-driven mechanical fuel pumps and FADEC-regulated servo valves. Also it can run using gravity or suction feeds. So there’s no way a generator bug can cause fuel starvation or complete engine shutdown. Boeing’s critical systems are segregated by design, so it’s very hard for an internal CAN network to be corrupted. Everything is supposed to be redundant on the Dreamliner.
Proud_Engine_4116@reddit
I don’t think the gravity feed is sufficient for climb power. It needs the pumps. The pumps are electrically driven. I don’t think the FADEC is immune to corrupted sensor data. That’s the point I’m trying to make.
If it received false values - eg. It thinks it’s going too fast something, it could wind the engines back. Ultimately it comes down to the amount of time the pilots had to process the event and take accurate corrective actions.
Brief-Visit-8857@reddit
You make good points, but the 787’s FADECs don’t just shut engines down from one bad sensor, they cross-check data with other sensors and default to safe thrust levels, and not fuel cut off. If both engines quit, that’s beyond “corrupted data” it’s a deeper systems level failure. Simultaneous engine rollback or fuel cutoff from corrupted data would imply multiple, coordinated sensor failures plus multiple logic failures in both FADECs. That’s possible only in theory, but let’s be real. The 787 won’t let that happen. It’s an advanced modern airliner.
Proud_Engine_4116@reddit
With known software bugs that the FAA has identified as potentially catastrophic - The FAA has received a report indicating that the stale-data monitoring function of CCS may be lost when continuously powered on for 51 days. This could lead to undetected or unannunciated loss of CDN message age validation, combined with a CDN switch failure. The CDN handles all the flight-critical data (including airspeed, altitude, attitude, and engine operation), and several potentially catastrophic failure scenarios can result from this situation. Potential consequences include
Disclaimer: I haven’t read the full article yet. But I will later today. A Reverse Engineer’s Perspective on the Boeing 787 ‘51 days’ Airworthiness Directive
Brief-Visit-8857@reddit
So it won’t be an Air India problem ? It’ll be Boeing’s problem then
Proud_Engine_4116@reddit
I just wanted to add: thank you for not attacking me. I feel like I have to say it because I tried to have this conversation on the u/IndianAviation sub and a lot of the members there were very upset that I was trying to independently understand what may have happened.
Brief-Visit-8857@reddit
Yeah of course, it’s good to have civilized debates. In aviation we learn from each other :)
Proud_Engine_4116@reddit
100%. Thank you again.
Proud_Engine_4116@reddit
Correct. But maybe someone at AI forgot or neglected to power cycle it. Being a person of Indian origin, I can totally see that happening.
Brief-Visit-8857@reddit
Again, the DGCA inspected all the 787s after this crash, and they were all in compliance, including the accident aircraft. The aircraft was compliant with Boeing service bulletins (which is includes the 51 day generator thing you are talking about). So I definitely think this wasn’t the case.
Proud_Engine_4116@reddit
Maybe. I doubt anyone can say it was power cycled for sure, especially if the document was falsified after the fact. If you’ve spent any amount of time in India, you’d realise how easy it is.
It’s also easy to create back dated legal documents. Just go to any court, you’ll find all kinds of services available to those willing to pay.
I actually don’t put too much value in DCGA reports, nearly 50% of their essential posts are vacant and they have choked aviation and gate keep it preventing regular folks from perusing their aviation career dreams or just recreational flying.
I think a proper investigation with data from the flight recorders will be vital.
Brief-Visit-8857@reddit
I agree the culture might be a little concerning, but let’s make one thing clear. India has one of the strictest aviation laws in the world. And with this being a multinational investigation, I believe it’s in their best interest to be truthful. And I think they’ve done exactly that so far.
Proud_Engine_4116@reddit
So far. I hope they cooperate, but saving face is more important for them than the truth. You can see echos of that throughout Indian society.
It’s one of the major reasons that forced me to immigrate.
Brief-Visit-8857@reddit
Again, the DGCA inspected all the 787s after this crash, and they were all in compliance, including the accident aircraft. The aircraft was compliant with Boeing service bulletins (which includes the 51 day generator thing you are talking about). So I definitely think this wasn’t the case.
pipic_picnip@reddit
I think I am going to rule out his comments based on the sole fact that everything I have heard from actual experts about this Steve guy has been awful. I do not think he is a reliable source unless someone else who can approach things with integrity can corroborate his theories.
Insaneclown271@reddit
The only actual evidence we have at this stage is that the RAT was deployed, indicating a dual engine failure/stall. There was no power being generated by those engines. There is no jet noise in the videos. Only aerodynamic noise and that of the RAT.
PigglyWigglyDeluxe@reddit
RAT deployment isn’t officially confirmed and even if it was, there are multiple reasons why a RAT would be deployed.
https://youtu.be/Rjc5M6JyriY?si=OKC6n4KdLcf1gq7C
Insaneclown271@reddit
Anyone denying the rat was deployed now is demented. Both engines were failed. There is no jet noise in the videos.
PigglyWigglyDeluxe@reddit
No one is saying it didn’t happen. In the video these pilots simply said it isn’t confirmed (yet) and all they care about is cold hard verified confirmed facts. That is, if governing bodies say so in official reports, and not what people say in the comments.
Insaneclown271@reddit
I’m a 787 pilot. Both engines were failed or at or below idle thrust.
PigglyWigglyDeluxe@reddit
We don’t even have a preliminary report yet.
nautica5400@reddit
At this point we are really stuck at what came first, the chicken or the egg conundrum
Did the engines stall out mechanically to cause the loss of thrust and power OR was there a catastrophic bus short or electrical failure that began the sequence.
Both have valid theories. All of this aside from any potential external components that would have contributed to this.
Insaneclown271@reddit
There are a shit load of ones and zeros flying around in a 787. It’s the most electrically dependant transport jet operating right now. Data corruption could shut both engines down through the FADEC system.
Ricky_Ventura@reddit
Not realistically. You're talking 4 FADECs, 8 channels. The exact same thing would have to happen to all of them, or
KingInTheFnord@reddit
If both FADECs are running the exact same software, then it's certainly within the realm of possibility that a software bug that is based on a specific combination of inputs/variables could affect all FADECs simultaneously.
It's the same reason I'm wary of self-driving cars or electronic voting in elections. A software bug doesn't affect one, it can affect every car, or every polling station, simultaneously.
But I imagine this software is one of the most rigorously developed and tested pieces of tech in the world, so it still seems far fetched to me. But I guess the point is that a loss of thrust in both engines simultaneously is such an unlikely event that whatever the true cause is, it's going to sound far fetched.
Ok-Hotel-3316@reddit
Lmao... Ah, it definitely should be. Instead, boeing outsources tech to India for $8 an hour. Google about it with the max crashes
Funkytadualexhaust@reddit
Crud, i had assumed they would need dissimilar sw..
Aetane@reddit
Yep, this is such an unheard of occurrence - pretty much by definition, the cause must be incredibly unlikely
Some1-Somewhere@reddit
I thought two FADECs, four channels?
Emotional_Two_8059@reddit
I also thought the same. And we also know from the early 787 testing that bus switching could make both FADECs reboot :/ Not sure what that would mean for the engines though.
fysiX_cs@reddit
What I learned yesterday from a 787 pilot: even if the fadecs fail, they go into a failsafe, using last present parameters. So in other words, if you are at your calculated thrust setting for a take off, let's say 92% (just a random number), your engines will stay at that thrust setting, even if all fadecs fail.
CactusPete@reddit
Would it be more accurate to say that if the fadecs fail, they are supposed to go into a failsafe? If some sort of software/computer meltdown is possibly at issue, who knows how far it went. In other words, in that scenario, maybe the failsafes failed.
Could something physical - bird strike or battery fire for example - have taken out the fadecs? Naked speculation from an uninformed person.
fysiX_cs@reddit
Yeah I guess that could happen, but apparently it is very very rare. Now thinking this would happen on 2 engines simultaneously, near impossible. I think you'll win a lottery first. ;)
Sure FOD (foreign object damage) could take these out but not in a way that you wouldn't see it. As we all saw on the cctv video, we couldn't see anything.
The more you read from pilots and engineers, the more absurd this crash gets.
Mr_Tiggywinkle@reddit
Huh? What kind of data corruption would that be?
I don't see how data corruption could hit both independent FADECs simultaneously in a way that cuts them both down.
really_random_user@reddit
More electrically dependant than airbuses?
Insaneclown271@reddit
The 787 is far more.
superdude311@reddit
Well depends if you’re talking about front facing software (things like Normal Law control on airbus) vs backend software deep in the control systems of the aircraft. I would say the 787 has more of those backend systems electronic compared to most airbus aircraft (except for maybe the a350), but airbus definitely lends more control to the electrical systems
Insaneclown271@reddit
Not talking about the flight controls. The 787 uses electrical power for systems usually powered by bleed air.
superdude311@reddit
This is true. However, those systems that used to be powered by bleed air would’ve been electronic before, it’s just the source of power generation that changes. The 787 uses batteries where the bleed air system would’ve turned a generator.
hunglowcharlie@reddit
no
Super_Forever_5850@reddit
Is this because they are programmed to shut down both engines in such a scenario…Or are the engines dependent on constant FADEC input to keep running?
LantaExile@reddit
f you watch the takeoff video the plane climbs normally for about 10 seconds and then suddenly starts descending without any change of direction or rudder suggesting both engines went simultaneously which probably wouldn't be the case for mechanical stall out.
I'm guessing something like the ANA engine shutdown https://www.aerosociety.com/news/ana-787-engine-shutdown/
Chen932000@reddit
Electrics failure shouldn’t lead to loss of the engine. The engines electrically power themselves.
superdude311@reddit
Well they wouldn’t lose power but they’d lose the control inputs. The FADECs are supposed to rollback into last parameters if they experience a failure, but maybe something went wrong in that process
Heiter-Sama@reddit
Additional option would be sensor errors causing the TCMA to shut down both engines?
Lyuseefur@reddit
I’m curious - what data is still recorded to the EAFR when the RAT is deployed?
Legal_Literature1356@reddit
Yeah, in the 787, black boxes still record data even if both engine-driven generators fail, because it has a RAT that kicks in and provides backup power.
But that’s not the case with the 737. Since its control surfaces mostly use traditional cable and pulley systems and not fly by wire, it doesn’t have a RAT. So, if both engines fail, the black boxes stop recording on battery power, it only works when either APU is ON or GPU is connected or at least one of the engine driven generator is working.
That’s why we don’t have the final black box data from the Jiju Air crash both engines failed after a bird strike, and the recorders just cut off.
Lyuseefur@reddit
So the 787-8 would have full data logging from all sensors to the EAFR?
Legal_Literature1356@reddit
Yes
Lyuseefur@reddit
This will be really interesting then. Unlike the Jiju bird strike - fortunately we have the video showing this … this crash has limited video and what we do see leaves us with far more questions than answers.
The primary failure cause of Jiju is known because of the video. Without it, it is likely that we would still be wondering why the engines failed.
I remain puzzled as to how a pretty well designed plane - multiple redundant systems - can just crash one mile after takeoff with no apparent cause. Obviously it had fuel. Even if there was no power (how?!) there would be the gravity fed system.
GE, Boeing, NTSB, UK and India have their work cut out for them.
My cousin worked as one of the PM on this program. She is quite distraught because they worked very hard and took pride in making an extremely safe aircraft….
ignited-eyes@reddit
Sorry? What about the whistleblowers about this same plane? And the issues they flagged early on with one of them dying?
Lyuseefur@reddit
Just as in any company, there are good people and teams and there are bad ones.
I know, for a fact, that my cousin was one of the good ones.
ignited-eyes@reddit
Oh no I just meant the product/plane has its flaws as highlighted by the whistleblowers No shade on your cousin at all.
Legal_Literature1356@reddit
Airport CCTV is still a big puzzle for me. It literally looks like both engines just gave up together. No bird strike, no signs of compressor stall or surge. Even if it was fuel contamination, we would've seen at least some signs like compressor stall but here, it feels like both engines lost the thrust at the same time.
Even if one engine failed before the other, we should've seen some opposite rudder movement to encounter the force of the working engine and I think 787 does that automatically.
I hope we will find some answers soon in the form of a preliminary report. It should be out in 30 days.
wowo78@reddit
dual engine FADEC failure?
Blythyvxr@reddit
this is bullshit - it's a copy pasta that was doing the rounds a couple of days ago.
The crash happened a week ago. We still have no idea what happened - The investigating authority has not even confirmed that the engines lost thrust, despite this being the prevailing theory due to the RAT noise.
There is no way we will get any indication of root cause until the final report is issued, which is likely to take 1-2 years at a minimum.
The Alaskan door incident happened about 18 months ago, and we still don't have final report for that.
Chrisnewton1@reddit
I know there has been a lot of talk about grounding the 787'w over the threads, how likely is this now to happen?
I was thinking that its been a week since this tragic incident, and as time went by it seemed to me more and more unlikely that a grounding of the 787's would be unlikely as if they suspected anything by now then out of caution the 787's would be grounded.
However after now learning they have sent the black boxes to USA, it seems were now back to square one and no one knows what caused this and it again could lead to a grounding.
How likely is it that after over a decade of flying there has been a design flaw in the 787's that just hasnt surfaced until now?
Is it possible that if there is a grounding then it might noe affect all the fleet and maybe just some varients of the 787's?
Do you think its still unlikely a grounding will happen given that we know the RAT was deployed and its "looking" like a possible dual engine failure?
TOAO_Cyrus@reddit
This isn't a new type of aircraft or a recently manufactured one. It's not like the MAX which was brand new so any crashes would make you suspicious of all of them. Even if it's a defect it's the first time its been an issue in 15 years which makes it highly unlikely to start causing 787s to crash repeatedly all of a sudden. What you look for as recent software updates and maintenance procedures. I am sure software updates were immediately analyzed to look for any possible connection and AI at least is definitely reviewing their maintenance.
drtywater@reddit
If India is willing to send the black boxes to the USA it leads me to believe they don't think its a Boeing problem. If India thought there was a serious 787 defect they would send it to France or UK as those were GE engines.
Also nitpick if India does send it back the NTSB would make a statement saying they have gotten the boxes.
Brief-Visit-8857@reddit
I looked it up and they haven’t decided where to send the black boxes to yet. The report that it was being sent to the US was fake, according to Reuters.
Link: https://www.reuters.com/world/india/india-send-crashed-planes-black-box-us-local-newspaper-economic-times-reports-2025-06-19/
Brief-Visit-8857@reddit
Indonesia and Ethiopia would like to have a word with you
drtywater@reddit
In those cases I believe they sent the black boxes to France not the US.
Brief-Visit-8857@reddit
It depends on the availability and how fast they’ll get the data. The NTSB laboratory has the most availability. This is a time sensitive crash, you want the data extracted as quick as they can. Indian and British officials will be going with the black boxes so that they make sure the proper protocols are followed.
MortimerDongle@reddit
It would need to be something that has a decent chance of re-occurring, which seems unlikely given this is the first major crash of a popular aircraft that's been around for a little while.
787s are a big chunk of long haul flights so any grounding would be a very big deal economically.
Even if a flaw is found, an AD with no grounding is most likely
61746162626f7474@reddit
Grounding seems unlikely I think unless a second accident were to occur.
There are thousands of 787 out there with probably millions of cumulative takeoffs, and in 15 years the 787 has been flying we’ve just had the first hull loss. This suggests the odds this type of accident occurring are very small.
More likely I think is that a preliminary report will come quickly followed by airworthiness directives that will instruct airlines to upgrade some component or change procedures to eliminate the root cause of the accident.
787 flights make up about 30% of all long haul flights each day. Grounding the entire fleet would have enormous implications on global air travel and I’m sure it’s something airlines, Boeing, international governments and regulators would try to avoid at all costs.
Robo1p@reddit
The amount of people falling for the emoji-ridden "report" is just disappointing. This is AI being about as obvious as it can, not trying to imitate professional writing.
After-Pie5781@reddit
Not an expert here. But the engines obviously failed and the plane just dropped from the sky. The deployment of the RAT and the fact that the landing gear had started to retract would suggest catastrophic electrical failure.
777978Xops@reddit
We still don’t know for sure that they failed
After-Pie5781@reddit
I think it’s obvious from the video that the plane was hardly moving forward then just seemed to drop to the ground. If the engines were functioning it would have travelled much further than it did.
MortimerDongle@reddit
The engines were likely not producing thrust but I would guess the cause ends up being something that is technically not engine failure. Simultaneous dual engine failure without an obvious external cause just doesn't seem plausible
777978Xops@reddit
Oh they were certainly not powered. Whether they “failed” we actually do not definitively know that
After-Pie5781@reddit
There could have been a problem with fuel supply. I’m not sure if an electrical failure would cause the engines to stop working though.
Brief-Visit-8857@reddit
FADEC is fully electric on the 787, and it’s supposed to be very redundant. But if a catastrophic electrical failure occurs then it might technically shut down both the engines
After-Pie5781@reddit
I thought they could rely on electromagnetic dynamos in the event of an electrical failure. Seems silly not to have a separate back up system for something as key to flying as the engines.
Brief-Visit-8857@reddit
Nope, they don’t use dynamos. They rely on backup generators instead.
Baleful_Vulture@reddit
https://youtu.be/-MDjRMkc-cc?si=joeIKU5vSIhtVyN-&t=664
There is an alternator which can generate enough power for the FADEC/EEC and keep the engines running, so that the engines can keep running independently of the rest of the plane's electrical systems.
Brief-Visit-8857@reddit
Thanks for educating me. That makes this crash even more interesting
After-Pie5781@reddit
Yeah it’s bizarre how the plane just shut down and dropped out of the sky. It’s scary that this plane relies so heavily on a computerised electrical system. We all know how easily these things can fail or just start acting up without warning from basic home appliances. I dread to think how dangerous that is for an aircraft carrying hundreds of people. It seems like this is a very popular model for a lot of airlines. I don’t think that I’m going to be flying again until we can be 100% sure that it is safe.
Brief-Visit-8857@reddit
These aircraft have been flying for 14+ years, and this is the only fatal crash of the 787. I suspect that this might be a one off case of the software or electrical system failing in a way that has never seen before. Rest assured, I think we will find out some very interesting things from this crash. Perhaps a redesign too. We’ll see.
Emotional_Two_8059@reddit
FADECs are powered by their own alternators. The plane’s AC bus is only their backup power source
Emotional_Two_8059@reddit
This still doesn’t explain lack of thrust. Engines are controlled by independent FADECs that are inside each nacelle and have their own dedicated generator connected to the engine. AC bus is only their backup power source. And they can suction feed fuel even if all electric pumps fail.
Brief-Visit-8857@reddit
Yep, I agree with you on that. Just unfortunate timing, happened at a critical phase of flight.
allielhoop@reddit
Timing is interesting - so soon after takeoff.
Blythyvxr@reddit
Well fine is relative. BA038 had a hard landing at landing weight, gear struts punctured the wings.
It’s entirely theoretical, but say if the incident had happened at the Edward’s lake bed, it’d probably be OK, provided a good enough flare. Over open fields, maybe some concern, but a lot better than what happened.
FutureHoo@reddit
I feel like something would’ve been released by now if it was indeed fuel contamination. The overall radio silence - not even a leak - plus AI allegedly canceling 787 flights over the smallest issues leads me to speculate the cause of the crash is still due to an unknown failure
priyajeet@reddit
https://m.economictimes.com/industry/transportation/airlines-/-aviation/india-to-send-damaged-black-box-of-crashed-air-india-787-aircraft-to-us-for-data-recovery/amp_articleshow/121937414.cms suggests that black box being sent to the US due to lack of recovery tools available in India
777978Xops@reddit
Indian government turned and said this article is false and they’ve not made a decision
Brief-Visit-8857@reddit
That sucks. The last the time a black box that was sent from India (AIX 1344 crash in 2020) to the US took 10 days to decode and share the data with Indian authorities. But I suspect it will take longer this time because it’s a 787
Tasty-Explanation503@reddit
Scrutiny will of course be high, but all other aviation authorities should be watching US investigators with a microscope considering Boeings recent history.
Everything will be above board of course, but no risks should be taken in handing over the recorders.
Brief-Visit-8857@reddit
The UK is also involved in this. I don’t think they’ll cover anything up. The NTSB and the FAA actually exposed Boeing for their wrongdoing.
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RealPutin@reddit
I would be shocked to see fuel contamination cause a true simultaneous total failure. Usually you see asymmetric behaviors and slow reductions. And yes, they almost certainly tested the fuel that same day.
Phil-X-603@reddit
I think it might have been a one-off case where everything lined up perfectly (in a bad way), and somehow softlocked the 787's software.
Brief-Visit-8857@reddit
Yep, I think so too. Because Air India is canceling flights for the smallest of reasons, and the DGCA inspected most of the critical systems on the 787 after the crash. That to me tells me that they don’t really know what caused the crash, so they’re being extremely cautious.
m-in@reddit
The plane looked totally healthy all the way up to collision with ground structures. If this is not a software bug, it’ll be some crazy Swiss cheese hole alignment. If this is a software bug…
bobblebob100@reddit
I doubt a software bug could turn engines off. Especially when in the whole history of the Dreamliner this has never happened before like this
Unusual-Nature2824@reddit
The 787 had a known critical bug 10 years ago that required the aircraft to be shut down before 248 days. Integer overflow bug.
https://arstechnica.com/information-technology/2015/05/boeing-787-dreamliners-contain-a-potentially-catastrophic-software-bug/
kksweene@reddit
It happened once on landing to ANA while landing at Osaka in 2019. They had to tow the aircraft off the runway. Obivously different scenario landing vs taking off, but still there is a case of this happening
bobblebob100@reddit
Was the cause ever determined?
Heiter-Sama@reddit
Not sure why you got downvoted.
No it was not.
https://samchui.com/2019/01/19/ana-boeing-787-dual-engine-shutdown-upon-landing/
emhaith@reddit
Why did they do the high reverse thrust and shut down immediately? Was there any problems beforehand that led the pilots to do that?
BritniPepper@reddit
There doesn’t seem to be any indication of a physical problem. Birds, flaps, whatever. The gear begins to retract, the plane ceases to climb, the RAT deploys, the thing struggles to stay in the air over city buildings and stalls into them.
There has to be some non-physical cause. Software, a wiring problem, sensors, whatever.
This is way out of the ordinary so it’s pointless saying that this system or that should have worked. Obviously something failed dramatically.
I think that we're going to have to wait for the data recorders to be analysed. That’s hard evidence that all the armchair analysts - no matter how experienced or well-informed - don’t have.
Powerful-Ad2338@reddit
Engine Fuel Filter problem on AI135 (HKG -> DEL, return to HKG)
https://www.youtube.com/watch?v=wh_a0-gkgME
thefreeman06@reddit
The latest from a BBC report - "Air India says one engine on crashed plane was new"
Source - https://www.bbc.com/news/articles/clyl636ynzvo
RealPutin@reddit
The AI announcement referred to it as overhauled in March, fwiw
thepriceisright__@reddit
Does the 787 have any automated protection against shutting down the wrong engine in an engine failure scenario?
Hastily shutting down the good engine in a panic is unfortunately a recurring problem in both commercial and general aviation.
Tasty-Explanation503@reddit
Getting to the point here, unless there is some wild pilot error on takeoff, boeing may have a lot of explaining to do.
How serious could a fault in the flight management system be for the rest of the fleet?
it-is-just-a-game@reddit
Boeing doesn't make or sell engines.
IcY11@reddit
Since when does Boeing build engines?
thefreeman06@reddit
Still too many unknowns to point the finger at Boeing, best is to wait for confirmed details ... there will be an answer for this
Great_Cellist8125@reddit
I have a feeling the truth will never come out. This is probably either a sabotage by the ground crew or a major undiscovered flaw with the 787 that will be found after investigation. The black boxes have been sent to the US for data extraction as India found it challenging to do so due to extensive damage to the black boxes. Who do you think the US will protect if the blame falls on Boeing? Naturally, this is going to end up as a fabricated investigation and report that will make the pilots as the scapegoats.
Brief-Visit-8857@reddit
Like they covered up MCAS? lol. NTSB ain’t covering shit up. Their entire agency is run by people who want to make aviation safer. Good luck convincing them to cover for Boeing.
grumpyfan@reddit
Technically, Boeing covered it up and lied to the FAA about MCAS.
Brief-Visit-8857@reddit
Boeing did. Not the NTSB. They found out
IcY11@reddit
Stop with the conspiracy nonsense. If there is a flaw with the 787 they will have to fix the other planes and issue an AD. How will they cover that up?
priyajeet@reddit
I think you might be confusing NTSB with the FAA. Not that FAA will cover up, but mistakes were made per https://www.reuters.com/business/aerospace-defense/faa-was-too-hands-off-boeing-oversight-before-737-max-9-incident-2024-06-13/
KeepItPositiveBrah@reddit
NTSB is not covering shit up
MahanZar@reddit
yeah ofc, the corrupt reputation of the NTSB. such dumb unjustified conspiracy , don't talk if you don't know anything cause trust me, people can tell
Hexadecimal-16@reddit
VT-ANB was only 25 km away from 9M-MRD (MH17) when it crashed in July 2014.
spooky how the first fatal wide body plane to crash since MH17 tried to contact it.
FutureHoo@reddit
Pedantic but there have been a couple of fatal wide body crashes since
UPS 6 (747), prime air crash (767) come to mind. Not commercial though
sizziano@reddit
Commercial yes but not passenger.
Hexadecimal-16@reddit
yeah they weren’t passenger planes though
pepe_le_silvia@reddit
What about JAL 516?
Hexadecimal-16@reddit
not fatal
SA1996@reddit
Everyone is assuming it was a dual engine failure.
I still think the flaps theory is more likely.
I don't trust India's investigation, I am expecting a cover up to protect India's pilots.
Similar-Tangerine@reddit
Low IQ conspiratorial thinking
Radiant_Mongoose_635@reddit
India, UK, USA are doing the investigation
railker@reddit
If you mean the AAIB for the UK, that's also the abbreviation for India's investigation board/bureau.
Tough-Candy-9455@reddit
Representatives from UK's CAA were also at the crash site according to media reports. No idea what is the extent of their involvement in the investigation.
railker@reddit
Good call, hadn't seen their name come up before.
DrSpaceman575@reddit
No flaps wouldn't deploy the RAT. "Flaps theory" is pretty thoroughly debunked at this point.
AtomR@reddit
That literally has never happened. India isn't China.
fysiX_cs@reddit
Yeah sure. What if the cover up is a cover up?
JSC843@reddit
What if the cover up is a cover up for a cover up to cover up something that is covering up another thing that covers up a cover up from a cover up to cover up more cover ups that cover up cover ups for a cover up to cover up something that is covering up another thing that covers up a cover up from a cover up to cover up more cover ups that cover up cover ups for a cover up to cover up something that is covering up another thing that covers up a cover up from a cover up to cover up more cover ups that cover up cover ups for a cover up to cover up something that is covering up another thing that covers up a cover up from a cover up to cover up more cover ups that cover up cover ups for a cover up to cover up something that is covering up another thing that covers up a cover up from a cover up to cover up more cover ups that cover up cover ups for a cover up to cover up something that is covering up another thing that covers up a cover up from a cover up to cover up more cover ups that cover up cover ups
WAKE UP SHEEPLE
fysiX_cs@reddit
Sry I lost you at "a cover up". Do you mind explaining what you mean like if you'd have to explain it to a 5 year old?
JSC843@reddit
How should I know?!? THE COVER UP IS BEING COVERED UP
fysiX_cs@reddit
I guess it's best to end it and cover everything up.
Rupperrt@reddit
lol, that’s one armchair expertise if he ever seen one. I really hope it’s a bit and not serious.
To get a hint what went wrong, just check what all the remaining 787s of Air India have been checked for, giving a good indication that most likely lack of thrust was the issue here:
“One time check before departure of flight from India w.e.f 15.06.2025,(00:00)Hrs onwards. a) Inspection of Fuel Parameter Monitoring and associated system checks. b) Inspection of Cabin air compressor and associated systems. c) Electronic Engine Control- System Test. Engine Fuel Driven Actuator-Operational Test and oil system check. e) Serviceability check of Hydraulic system. f) Review of Take-off parameters.
Legal_Literature1356@reddit
Typical Captain Steeeve target audience.
Tough-Candy-9455@reddit
Uhh, NTSB is doing the investigation as well.
And you should read the reports of last two Air India crashes, both caused by pilot error. The investigation went hard on the pilots and training culture of Air India. In fact in the Kerala crash the AAIB specifically faulted the pilots for not using correct flap settings during the landing.
And there literally is wreckage picture with flaps extended so....
Automatic4k@reddit
The government said it would take a call on the location regarding the decoding of the black box of the doomed Air India plane in Ahmedabad after a thorough assessment from all angles by the AAIB.
https://www.indiatoday.in/india/story/air-india-plane-crash-black-box-ahmedabad-london-decoding-location-decision-soon-2743229-2025-06-19
k_dubious@reddit
I have a sinking feeling that this is going to turn into another massive scandal for Boeing. There just aren’t that many things that can cause a complete power loss within seconds, and all of the physical or mechanical explanations don’t seem to fit the facts here.
twisted_angular@reddit
May be related to poor maintenance too. These planes have been flying for more than 15 years.
twisted_angular@reddit
Not sure why downvoted, i am an Indian by the way so not being racist :). But reality is some Indian companies do cut corners. Whatever it is, i hope we get answers soon to make sure it doesn’t happen in future.
ignited-eyes@reddit
Appreciate your perspective but there is definitely a thing that's being racist against your own people.. I forget the term but just because you belong to a particular community doesn't excuse you from carrying biases against them. Specially, when it comes to being Indian or Pakistani for example there's a colonial hangover and an inferiority complex. It's in the little things like skin colour of appreciating your own stuff once it's adopted by the west like turmeric latte and what not and prior to that being not only oblivious but anti it. And the west ofc, approproating all of it without giving any credit to where it comes from etc etc.
Cgy_mama@reddit
I feel like at this point in time, virtually all companies are cutting corners.
kadala-putt@reddit
Air India in particular has been mismanaged by the government for decades. All of those videos you see online about dirty planes and broken seats/toilets/IFE are all a direct consequence of that IMO. It was making colossal losses at the time the government decided to (re-)privatize it. Because of the huge debt burden it had incurred over the years, the first two attempts at privatizing it failed, and it only succeeded in 2022 after the government decided to stick the tax payer with the lion's share of the debt, but the buyer still had to take on a substantial amount (about 3 billion USD or so). So I wouldn't be that surprised if it emerged that they were cutting corners under government ownership, and the new owners continued to do so, particularly since the airline is yet to make a profit.
Jockel1893@reddit
In such sensitive topics it might be better to think (check facts) and not feel it. Do you have any proofs of your statement other than feelings?
asukaj@reddit
So you dont think air india maintenance cut corners?
Jockel1893@reddit
It could be but I replied to the statement „all companies cut corners“ above.
Ok-Adhesiveness-4141@reddit
All Indian companies cut corners, as Indians we need to admit this.
Pretty sure Air-India's maintenance is below par.
theflawlessmech@reddit
Aircraft maintenance personnel are severely underpaid in India. I knew an unlicensed mechanic getting paid 15k inr (USD 180 per month) for working 10 hrs 6 days a week. Even though it's the ame who certifies the work (they aren't paid much better) the actual work is still carried out by the mechs.
ignited-eyes@reddit
11 years. This one.
stupidbitch69@reddit
The aircraft VT-ANB has only been flying for 13 years.
Lost-Inevitable42@reddit
The irony is that so many pilots/media speculators used the "flying for more than 15 years" as a reason why a malfunction was NOT likely.
Brief-Visit-8857@reddit
It’s gonna be a combination of everything, that’s for sure. Design flaw (possibly), bad maintenance practices that triggered the design flaw, something like that is what my money is on.
Aerztekammer@reddit
The 787 is an amazing plane. I from europe and an airbus all the way girl, but i really doubt that it's a design flaw. Poor maintenance seems more likely to me given how this airline operated. What really wonders me is how an airline that is fine to fly with seats without a working seat belt can be in star alliance.
Brief-Visit-8857@reddit
Tell that to certain European airlines that also have the same problem lol. You’re acting like European airlines never had a crash due to maintenance. And also even a maintenance fault shouldn’t cause a simultaneous dual engine failure in a modern airliner.
Aerztekammer@reddit
I pointed out i'm european to show that i'm not a boeing fangirl. 🤷♀️
Brief-Visit-8857@reddit
That’s like saying just because American Airlines’ IFEs aren’t working they should be banned from flying in Europe. Also American Airlines has also had a bunch of crashes due to maintenance lol. Double standards much?
Aerztekammer@reddit
bro you are imagining things i never said anything like that. I just said that i am not a boeing fangirl and i prefer airbus.
I just said that what we saw from air india by now, i wouldn't be surprised if they had poor maintenance. work on your reading comprehension before you get yourself so angry
Brief-Visit-8857@reddit
FYI, Boeing exactly hasn’t had a great track record
Aerztekammer@reddit
The boeing 787 is a save plane. Its been operating since 2009 and there was one crash.
Brief-Visit-8857@reddit
Are you forgetting about the issue with the batteries? Or how a lighting strike created micro holes in the 787?
Aerztekammer@reddit
By your definition, the whole world is unsafe. Every second outside can kill you.
Brief-Visit-8857@reddit
Now you know how ridiculous what you said sounds.
trenbollocks@reddit
Does being European preclude you from being racist, or at least prejudiced against non-Western airlines?
Aerztekammer@reddit
lol i don't have prejudice against non european airlines i prejudice against airlines that don't fix their seatbelts, don't care for their inflight standards like inflight entertainment and air condition. For example emirates, china airlines ect. are all competent airlines.
twisted_angular@reddit
I agree.
really_random_user@reddit
Seems kinda unlikely that it would lead to a total systems failure
Unless it's some sort of cascade fault
Brief-Visit-8857@reddit
Yeah, I agree. Brace for the downvotes
throwawayShrimp111@reddit
You complain constantly about people prematurely blaming the pilots, only to now try and pin the blame on Boeing lol.
Go use your telepathy or w/e to tell us what the real issue is.
Brief-Visit-8857@reddit
lol, imagine digging through my comment history just to undermine what I said 🤣 Get a life dude
Brief-Visit-8857@reddit
lol, imagine digging through my comment history just to undermine what I said 🤣 Get a life dude
777978Xops@reddit
After 4 million flights somebody would’ve died before this.
Everything where Boeing has been the root cause have been frames that are literally not even up to 2 years old. This frame is over a decade old, it has been though a lot with air India.
There are many places to stop before we get to the OEMs
And I think the OEM is one of the last stops.
RandomObserver13@reddit
While I disagree with the original comment, whoo boy are you wrong.
https://en.wikipedia.org/wiki/Boeing_737_rudder_issues
phluidity@reddit
Until we get the investigation reports, there is zero basis to make this statement. If it is a one in a thousand outcome of a situation that only happens one in every ten thousand flights, this may be the first time the holes have ever lined up.
Is it possible it is 100% a maintenance issue? Sure. Is it possible it is a design issue? Also sure. Is it possible it is a design issue that has been exacerbated by maintenance? Once again, sure.
777978Xops@reddit
There’s zero basis to make any statement…but here we are all making statements. Nobody has seen the report…
Get_Breakfast_Done@reddit
Are there software updates that have a lot fewer than four million cycles on them?
an_actual_lawyer@reddit
My leading theory, which is worth exactly 2 pennies, is that this system was overridden by maintenance personnel because they either couldn't figure out a problem with it or needed the plane available before the sensors/part(s) could be delivered.
dek00s@reddit
Hey, I had an idea that I haven’t heard discussed. Is it possible that a severe fuel contamination issue could cause loss of power to both engines? I doubt it would cause a full loss of power that quickly, but just an idea…
Ricky_Ventura@reddit
Maybe. This has happened twice semi-recently, both times when DEF was erroneously added to the Jet A. Both planes suffered double flameout, both landed safely after doing air starts.
You're right, it likelg wouldn't have happened that fast and it definitely wouldn't have affected this singular plane.
MamaessenKP@reddit
Maybe a dumb question, but when they build planes, do they take stuff like “Monday products” or bad production batches into account? Like, if they install two engines on a plane, are those engines from the same day, same factory, maybe even built by the same team—or do they mix things up on purpose? I’m just thinking of that thing you hear in PC hardware: if you buy two of the same hard drive from the same manufacturer on the same day, there’s a good chance they’ll fail around the same time.
Some1-Somewhere@reddit
Aircraft engines get swapped around between planes regularly; I think they said the right engine is brand new as of a couple of years ago. The same goes for many other parts. It's one of the earliest 787s; it's been through a lot of maintenance since initial construction.
turkishguy@reddit
The level of testing on every single component that goes into an aircraft engine is hard to fathom. There is no such thing as "bad product batches" - every component has stringent testing requirements it must pass before it eventually goes to assembly and then is tested again.
The GEnx engines are assembled in a single plant. Trying to produce them in multiple factories would be cost prohibitive. There are always different crews working and I can't answer the question on if Boeing takes into consideration the day of production.
railker@reddit
What you're saying does exist as a form of redundancy in some respects, but I haven't seen it in the form of segregating engines before. One of the aircraft in our hangar has 'sister' engines manufactured one after the other, but others have engines that are hundreds of units apart. Where you might see such redundancy is detailed in Wikipedia's article on FBW, which mentions a specific case example of the design of the Boeing 777's Primary Flight Computers, which each "housed three 32-bit microprocessors, including a Motorola 68040, an Intel 80486, and an AMD 29050, all programmed in Ada programming language."
Whether it's a new production aircraft or an engine change, you go park somewhere and perform "power assurance" runs, as the DGCA mandated all Air India 787s to do within 2 weeks. Modern aircraft do it all themselves, the older ones I work on you manually perform various tests at high power settings to ensure everything from oil temperature to the speed of the rotors and the temperature in the turbines is within specification, as well as performing all the related function checks of normal functions as well as redundancies, including turning off the EEC/ECU (or forcing it into alternate mode).
Can something still go sideways? Absolutely. But you aren't rolling an aircraft out to take passengers without having run that engine before and performed the prescribed tests to assure its performance.
matt3633_@reddit
Right engine had recently been replaced
priyajeet@reddit
Per this interview https://www.msn.com/en-in/money/topstories/air-india-chairman-n-chandrasekaran-offers-apology-says-jet-had-no-red-flags-new-engine-findings-due-in-30-days/ar-AA1GYiEZ
"But the fact that I know so far is this particular aircraft, this specific tail, AI-171 has a clean history. As for the engines, the right engine was a new engine put in March 2025. The left engine was last serviced in 2023 and due for its next maintenance check in December 2025. Both engine histories are clean"
Brief-Visit-8857@reddit
New engine? Maintenance mis-wiring something?
matt3633_@reddit
That's what I was trying to tell you the other day..
Brief-Visit-8857@reddit
Highly doubt it though… since only one engine was replaced. The other one should’ve worked fine still.
matt3633_@reddit
The FADECs receive data from shared systems, electrical miswiring could cause an issue that causes both FADECs to react simultaneously
Brief-Visit-8857@reddit
Actually, in the 787, each FADEC is electrically and logically independent. So even an mis-wiring shouldn’t cause simultaneous dual engine shutdown.
Emotional_Two_8059@reddit
Exactly
Brief-Visit-8857@reddit
It was fine for 3 whole months. I give this like a 20% chance of being the cause of the accident.
Snuhmeh@reddit
And the problem pops up months later and probably hundreds of hours of operation? On both engines? With no visible engine problems at all?
Brief-Visit-8857@reddit
I actually argue against this possibility in this thread here: https://www.reddit.com/r/aviation/s/l1Klk3VZgJ
Leather_Bat_6176@reddit
I’m flying a 787 Dreamliner from Sydney to Dallas next month and I am absolute terrified. Already such a nervous flyer and now I’m beside myself. I used to always love and feel so safe I this aircraft :(
IcePuzzleLocal5708@reddit
The most dangerous part of your flight is the drive to the airport, always.
Mission_Nin@reddit
I am also on a 787-9 this Sunday. Last year they rerouted this flight due to concerns about about Israel/Iran hostilities but now with definite hostilities taking place ... we are still going through the Middle East it seems.
I sympathise entirely with you. I will be literally counting down the minutes after take off until we get to level flight. And I will be checking the flight path...
Leather_Bat_6176@reddit
Where are you flying from/to?
CarbonKevinYWG@reddit
787 has be in service for 16 years and has flown over a billion passengers without incident.
This is the definition of an irrational fear.
Mission_Nin@reddit
I know it's irrational but that doesn't stop the fears...
Chen932000@reddit
This is still one of the safest airframes around.
pehpehsha2@reddit
Possibly a stupid question, currently my thinking would be some catastrophic electrical failure.
I see a lot of different components, electrical systems, data recorders etc have independent and redundant power supplies. I'm just wondering how that is done? Cause I imagine if you go follow the chain high enough to the power source if there was a massive failure it could take a whole lot of systems out?
There's so much inbuilt redundancy it's hard to imagine how both engines lost power so quickly into the flight
Some1-Somewhere@reddit
The 787 has four main generators (two on each engine) delivering AC power. There's also a pair of similar generators on the APU, but that wouldn't have been running.
Any one of those four/six should be enough to run most of the important loads like fuel boost pumps, instruments/radios, and some hydraulic pumps, but you likely need to shed cabin air compressors (pressurisation/aircon), in-flight entertainment, galleys, backup hydraulic pumps, and other non-critical loads.
Each engine has an accessory gearbox that mechanically powers:
Its two AC variable-frequency starter-generators, listed above
A mechanical hydraulic pump, supplying the left or right system (respective engine).
The centre hydraulic system only has hydraulic pumps, plus the RAT that only powers flight controls not the rest of the centre system (gear and flaps)
Any of the three hydraulic systems has enough flight controls for controlled flight.
A FADEC alternator, supplying the engine controller and actuators. If this fails, the backup supply for the engine controller is the main aircraft power.
A permanent magnet generator for the flight control computers (two on left engine, one on right). Backup if all these fail is again main aircraft power.
A high-pressure fuel pump for feeding fuel into the combustors, and for fuel-operated hydraulics in the engine. This can suck fuel out of the fuel tanks if necessary at lower altitudes in the event of boost pump failure.
In addition, you have:
A ram air turbine, delivering a small amount of electric and hydraulic power sufficient to run a limited selection of flight computers, radios, navigation gear etc.
A pair of aircraft batteries, capable of the same as the above but even more limited selection, plus starting the APU.
Cumulonimbus1991@reddit
There's so much redundancy in here, this has to be an incredible slim swiss-cheese linup to cause a crash such as this. Something no one would every think it could happen beforehand.
frumperino@reddit
I think nobody will ever look at planes as thoroughly engineered as these and find that not enough redundancy was designed into all the critical systems. The swiss cheese model veers into stratospheric levels of improbability for enough things to go wrong at once to kill both engines.
But as with MCAS an otherwise beautifully engineered plane can be compromised and all those carefully planned redundancies defeated when you trust faulty software to sit at the heart of the plane in some black box and let it have an extremely high level of authority that can silently and unexpectedly sabotage the whole system.
Which box hosts the TCMA system? What authority does it have? What safeguards prevent it from activating and shutting down the engines when the plane is in flight or during takeoff? How bulletproof is the logic that creates the "it is safe to shut down engines" state information? Can an upside down mounted gear position sensor defeat it?
Some1-Somewhere@reddit
TCMA is software running on the FADECs. Exact details on how it senses air/ground are not known but apparently on the 747-8, at least two different sensors of different types would have to agree it was still on ground.
NigroqueSimillima@reddit
AI-171’s GEnx engines aren’t subject to the bulletin that showed a TCMA dual cut.
Some1-Somewhere@reddit
Maybe not, but that just means that particular bug doesn't exist - it couldn't have been that exact bug anyway, because there's little reason to select reverse during takeoff.
TCMA is on them nonetheless.
fugutoxin@reddit
It sounds like the engines and the engine controls are well-insulated from any severe electrical failure that might occur in the aircraft. So even if electrical power to everything else was lost, the PF could still manually operate his PFCs and the engines?
Some1-Somewhere@reddit
Yes.
fugutoxin@reddit
I don’t believe a pilot can switch to manual control mode or switch off FADEC. It exists with multiple layers of redundancy. But the pilot is out of the loop when it comes to ultimate control over the engines.
Some1-Somewhere@reddit
'Manual' as in 'not via the flight control computers or autothrottle'; the FADEC directly reads the thrust lever angle and operates based on that. Think direct vs normal law for flight controls.
FADECs are indeed Full Authority.
fugutoxin@reddit
But you seem to be saying that FADEC will defer to the pilot’s throttle command even if it judges it to be a bad idea, yes? Is that in fact the case?
Some1-Somewhere@reddit
Deciding whether the pilot's request for thrust is a bad idea is a job for the flight control computers. If they're not running, the request for thrust goes straight to the FADEC and it does its best to meet that request.
TCMA is not about pilot error or overriding the pilots. It's for if the engine breaks in such a way that it can only deliver high thrust, but the pilots want idle (Uncommanded High Thrust/UHT). There are apparently a bunch of ways this can happen, but one option is a stuck-open fuel valve.
The FADEC then has a choice: keep the engine running (in a faulty, high-thrust way) and let the pilots shut it off if they want to, or shut the engine down completely.
TCMA says you keep the engine running if it's in the air, but shut it down on the ground.
railker@reddit
Haven't had the chance to watch it yet, but Stig Aviation is a line mechanic and works on the 787 and has just put out a video showing some of the technical side of the things we've been talking about over here.
Blythyvxr@reddit
There's a decent (understandable) undertone of anger/frustration in that video, particularly when discussing the flap retraction bullshit.
A lot of interesting information in that video on the systems.
DogsOutTheWindow@reddit
Awesome video!! Thanks for sharing with us man.
Brief-Visit-8857@reddit
Looks like the emergency power was operational before the crash. Looks very much like a dual engine failure.
Source: https://www.wsj.com/business/airlines/boeing-787s-emergency-power-system-likely-active-before-air-india-crash-148b7e02?mod=hp_lead_pos1
tranquility__base@reddit
railker@reddit
So a repeat of everything we already knew but worded slightly different to sound new. But honestly not a bad write-up considering the news usually bungles aviation topics.
Brief-Visit-8857@reddit
We didn’t technically have official confirmation, but now we know for certain the RAT and flaps were deployed
AtomR@reddit
How? Most aviation experts had already communicated it. What's the new source now?
Brief-Visit-8857@reddit
Sources from the actual investigation
railker@reddit
First two words from behind the paywall are "Investigators believe", they're about as sure as we already were within hours of the video coming out and unless they've already opened and fully read and analyzed the FDR data, are probably looking at the same stuff we are. I also see no mention of flaps anywhere in that paywall quote from tranquility__base.
I get being eager for information, we all are, but I see nothing certain or official or new in that article.
Brief-Visit-8857@reddit
Yeah, well this coming from the investigators instead of armchair experts is pretty telling to me. Because now we can solidly believe that they actually were out. They’re probably sifting through some of the data decoded from the FDR.
Spa_5_Fitness_Camp@reddit
We know neither of those things for certain.
sizziano@reddit
Ha Brickhouse, good dude. Still teaching at Riddle by the looks of it.
Snuhmeh@reddit
Engines don't spool down fast enough for all this to happen. Also, there wasn't any smoke coming from the engines and no noises of failure. I ran think the cause is going to surprise and disturb everyone.
Fragrant-Tomorrow757@reddit
Engine doesn't fail easily. Maybe their was an interruption/contamination of fuel
Snuhmeh@reddit
Or, unfortunately, someone pulls the fuel cutoffs
railker@reddit
That Horizon Embraer flight was a hair's breadth away from that happening last year. A wild fluke for sure, but proof that nothing is certain. We don't know what we don't know.
Brief-Visit-8857@reddit
Sabotage/pilot error has been ruled out already
allielhoop@reddit
Source?
Brief-Visit-8857@reddit
My bad, it’s still being considered.
Brief-Visit-8857@reddit
Right, so at this point it’s almost certain that it was a catastrophic electrical failure, or fuel contamination. But considering AI is canceling flights for the smallest of reasons and inspecting everything it sounds like they still aren’t sure what caused the engines to lose power.
F1010594@reddit
Still to be verified but it looks like a catastrophic electrical failure on rotation.
Flight: AI-171 | Aircraft: Boeing 787-8 | Date: June, 2025 | Route: Ahmedabad (VAAH) → London Heathrow (EGLL) Crash Site: ~1.2 km from VAAH Runway 23, post-V1 and rotation Fatalities: 247 (243 onboard + 4 ground) Survivors: 1 onboard survivors (alternate to original), 3 injured on ground
🛠️ AAIB Preliminary Report Highlights
Primary Cause – Electrical Power Transfer Interruption (PTI) During Rotation • During transition from ground to airborne electrical configuration, the aircraft experienced a cascading dual-engine FADEC (Full Authority Digital Engine Control) failure. • Root cause: Uncommanded bus transfer failure due to arcing in the main power relay box (PRB-A), traced to water ingress during pre-flight GPU disconnection in heavy rain. • This led to loss of electronic engine control at rotation, resulting in both GEnx engines rolling back to ground idle within 4–5 seconds.
Flight Data Record Timeline • +0:11 sec: Nose gear lifts off. • +0:13 sec: Sudden engine rollback begins. Thrust reduces from 92% N1 to <27% within 3 seconds. • +0:16 sec: Master caution + ENG FAIL L/R warnings. FO calls, “Both engines dropping!” • +0:20 sec: Autopilot and flight control reverts to Direct Mode. Pitch up attitude peaks at 18°. • +0:25 sec: Aircraft stalls at 186 ft AGL. • +0:30 sec: Full aerodynamic stall; nose drops rapidly. • +0:38 sec: Ground impact at 54° nose-down attitude, 174 knots.
Contributing Factors • Environmental Conditions: • Torrential rain during pushback. • Moisture intrusion into PRB-A connector (P/N: HLN8471) — a known corrosion-risk component. • Latent Maintenance Issue: • Power transfer relay unit showed signs of thermal damage in a previous MEL deferral 2 weeks prior. • No replacement had been conducted; aircraft was cleared under repetitive deferral. • Design Oversight: • Boeing 787 has no physical engine control backup (i.e., no direct mechanical linkage in FADEC loss scenario). • Loss of power supply to both EEC channels resulted in engine “freeze” at ground idle instead of flameout. • Flight Crew Response: • Attempted engine relight sequence not completed before stall onset. • Emergency power selector not activated — possibly due to confusion from multiple ECAM warnings. ✈️ Immediate Safety Actions • DGCA + EASA + FAA Emergency AD issued within 24 hours: • Mandatory PRB-A moisture integrity inspection on all Boeing 787 aircraft. • Temporary restriction on dispatch with MEL items related to power transfer systems. • Boeing: • Issued Service Bulletin SB-787-24-212 requiring replacement of PRB-A connectors with sealed versions. • Exploring addition of dual-path power redundancy for FADEC systems. Lessons Learned • Over-reliance on electrical power distribution architecture without layered redundancy. • Lack of crew procedural training for full engine rollback during takeoff in EEC dual failure scenarios. • Need for improved environmental sealing in GPU/electrical handover units in monsoon zones. Human Toll • The loss of 243 onboard lives, including 12 crew and 18 infants, deeply impacted the aviation community. • Final words captured on CVR: “We lost everything – no thrust!” • Aug 15, 2025: Release of FAA/Boeing electrical design audit report • Sept 5, 2025: ICAO session on electrical-critical phase-of-flight risk mitigation • Oct 2025: Mandated design retrofit across 787 fleet (rev. SB-787-24-219)
ECrispy@reddit
That guy Steve on YouTube is certainly milking this and making $$$. IMO he's the worst, using tragedy for his own gains.
He first blamed the pilots and put out video and sent on numerous shows and news media, acting like an expert, completely dismissing all other evidence and blaming the pilots.
He got backlash from informed people, in comments here and online, so he then makes another video 2 days later claiming 'new information about RAT' which is of course complete nonsense as people were posting about RAT from the beginning. Again, he gets to go on all the shows and get paid as an expert, not even apologizing.
NorthernEwan@reddit
He’s just posted a new video on some stupid baseless theories. Compressor stall, fuel contamination, and vapour lock…
No evidence of compressor stall whatsoever on any video. As for the other two, vapour lock or contamination in both engines at exactly the same time causing a simultaneous rollback? I don’t think so….
Stating the obvious, this is a system failure that affects both engines, and there are only a few things that may cause this including FADEC - which is plagued with issues.
Blythyvxr@reddit
3rd video… prick.
Comparing him and Blancolirio - Juan Browne does way more accident videos, near misses and covers a lot of GA - you can tell he does it because he cares about flight safety. Doesn’t get that many views, doesn’t sensationalise and uses his knowledge and experience to add information. He did jump to a conclusion on a recent video, but gave a retraction quickly, and with the same prominence as the video. (Although in that particular case he should have lawyered up imo)
Captain boy, with his epaulettes and his thumbnails, is clearly doing this for views and is being sensationalist. He’ll have another two videos out by this time next week. Tabloid YouTuber.
ECrispy@reddit
He's a scumbag it's pretty obvious now, I wish other experts called him out on his lies
LantaExile@reddit
Not sure how that's much different from your average news organisation coverage?
Legal_Literature1356@reddit
You probably haven’t seen that video where he shamelessly defends his stance, saying things like “some people will say wait for the preliminary report, others will say wait for the final report everyone has their own take.” So basically, he’s fine with blaming the pilots right away, but somehow has a problem with people asking to wait just a few more hours or days for facts to come out.
And it’s not just that he even went on multiple news channels as an expert pushing the same agenda that the pilots retracted the flaps instead of the landing gear.
Mentor Pilot did a live stream where he didn’t speculate on anything. Blancolirio waited at least 48 hours before making his video about explaining RAT.
And if you think Steve is the worst, just look at his followers and their comments. People are blindly supporting him and saying "Nothing wrong with the speculation Steve, even if it's pilots fault we need answers". Seriously? You don’t think the pilots families are also looking for answers and when their kids will go to school everyone will judging them like it was their fathers fault.
I’m not denying the possibility of pilot error. But is it really that hard to just wait 30 days for preliminary report?
You should watch his video where he went to clean his image.
https://youtu.be/2s4IqA3xR20
superhash@reddit
Oh I'm certain that he has bought clicks and views, none of that seems organic.
es-como-es@reddit
30 days? He couldn’t even be bothered to find the source video with the RAT sound before putting out his first “analysis” insinuating pilot error. Then shamelessly back peddled on the follow up video, claiming to have come across “new” evidence.
ECrispy@reddit
just saw that, disgusting and he's treated as some expert
Brief-Visit-8857@reddit
Oh god the comments are supporting him. Ugh people never learn
diego_reddit@reddit
He is laughing all the way to the bank
Brief-Visit-8857@reddit
That asshole made 150k plus off of those videos. Doesn’t he make enough money already?
Unlikely-Squirrel832@reddit
He's close to mandatory retirement age as an airline pilot I believe, becoming a full time youtuber probably means he'll make more money than from his retirement funds.
ECrispy@reddit
he titled his video 'what really happened' as well as if he has some secret knowledge. all the idiot media had him on and he's made hundreds of thousands more.
Not____007@reddit
Same plane taking off from Frankfurt https://youtu.be/hLnftY89ito?si=wfKjD7ZoP0a-Jlqa
Tough-Candy-9455@reddit
Yeah I was very much on the flap retracted/SpainAir like crash theory before I saw this video. Flaps 5 can very easily missed on the 787 in those blurry videos, its pretty inconspicuous.
onmyway4k@reddit
It was always very clearly visible that Flaps/Slats where out https://imgur.com/a/JzS3ro9
chillebekk@reddit
That could so easily have been a compression artefact. DCT-based compression is notorious for artefacts along edges (called "ringing") when they are pushed.
Not____007@reddit
Well some of us only got 787 rated this weekend lol
RealPutin@reddit
IIRC Flaps lever setting 1 is slats only, but I don't think there's any reason to believe the flaps weren't at least at 5 (which is required for takeoff)
Philownsyou@reddit
Not an aviation expert, but is the smoke coming from the turbines normal? You can pause at 1:33.
Not____007@reddit
I believe very normal https://www.instagram.com/reel/DK0-Xs5iCsE/?igsh=MTQwbjdiZGhzMjlnZw==
LiquicityMS@reddit
is it possible that toga could not be activated in 1st place? why no one is considering it? genuine questions
Tough-Candy-9455@reddit
Actually within the realm of possibility, there was an incident of a Jet2 plane where they missed to press TOGA after being work saturated on take off.
That being said I don't think so because:
FR24 gives speed of 170kt on take-off, which to my understanding is around the normal TO speed of a 787
It's a pretty easy fix. It's not like they hit an obstacle immediately near the runway (thinking of two previous Air India incidents, one the seat collapse and the other in the 90s at Aurangabad). It managed to get to like 600ft (video seems like a normal TO?) and lasted 30 seconds. They should've realised it and slammed the TOGA firewall.
Doesn't square with other evidence of ADS-B being lost and possible deployment of RAT
RealPutin@reddit
A - the plane took off
B - the pilots would likely not take off if TOGA couldn't be activated
Jaxxx187@reddit
He should be checked for super powers
WormTop@reddit
For a more sane perspective on this: let 242 people each roll 3 dice. On average, just one of the people will roll a triple 6.
Dependent_0NE_7146@reddit
How come we don't have streaming cam's directly in the cockpit? Or at least a video camera recording what goes on in the cockpit?
Brief-Visit-8857@reddit
Why would you need that if you have cockpit voice recorders?
trader45nj@reddit
Seeing physical actions would add information. Are both pilots in the cockpit, is one slumped over, is one attacking the other, etc.
Spare_Math3495@reddit
Pretty sure the black boxes recordings would make all of those clear without the video
Tiny-Plum2713@reddit
Statements like "anti ice was turned off either by one of the pilots or something else" are very common.
Spare_Math3495@reddit
Pretty sure the black boxes recordings would make all of those clear without the video
RandomObserver13@reddit
The NTSB has requested the FAA mandate them, but pilot unions and groups like ALPA have fought against them, mainly for concerns about privacy and misuse.
Dependent_0NE_7146@reddit
A compromise would be to only have them on during Take off and Landing, since a majority of issues usually happen during those two times
CoconutInteresting23@reddit
During "sterile cockpit" conditions okay, would be fine for me (pilot in training). But not when i want to talk to my workmate or cabin crew
RandomObserver13@reddit
There’s more money lobbying against them than for them. Until that changes, no cameras.
Envelope_Torture@reddit
Pilots unions everywhere fight very hard against video footage in cockpits.
kamikazechaser@reddit
From a tech perspective, there is no limitation. This is mostly to do with standardization, bureaucracy or both.
Aberracus@reddit
The survivor commented about an explosion 30 seconds into the flight , maybe one engine blew, and the pilots in panic turned it off but by mistake turned the working engine.
Snuhmeh@reddit
It was honestly probably the RAT deploying. He was sitting kind of near it and it pops out rather violently with a spring loading.
Tiny-Plum2713@reddit
Or it was the impact. Either way, eye witnesses are very unreliable. Especially those that have been involved in the accident.
nautica5400@reddit
I was curious about if the sound was a large electrical short or boom within or underneath the plane.
Not____007@reddit
most likely the rat door opening
SpeciesEL@reddit
The whole flight was only 30 something seconds...
Aberracus@reddit
His words
Tough-Candy-9455@reddit
I've worked in trauma casualty and you will be surprised to find how unreliable memory is. I've seen people say with 100% confidence stuff like "I was the car running over his left arm" with no evidence of any injury to the left arm.
With a shock and such an accelerated timeline I would not be giving that much weight to the minutiae of his testimony over physical evidence.
Aberracus@reddit
Sure, probably wasn’t 30 seconds at all, but an explosion is something
MyDespatcherDyKabel@reddit
I’ve heard many people say the nose could be the RAT deployment too.
Tough-Candy-9455@reddit
It can easily be the crash itself?
Tough-Candy-9455@reddit
You would see asymmetrical yaw at some point on the videos. There was none. Or any other indication of an explosion/bird strike to the engines.
maporita@reddit
This would have been evident in the video .. there would have been some asymmetry in the flight path. Instead we see a perfectly symmetrical aircraft take off and immediately lose thrust and crash.
s_p_s@reddit
https://www.instagram.com/reel/DK610Uly8jk/?igsh=OWhrN3M2c2RlczIx
Posting a video not seen anywhere yet. The video itself is not much, but it's the discussion that's interesting. At the very beginning and at the end, they are discussing that there was a bang/cackling sound after takeoff, then it crashed. Will do an accurate translation/transcript later
guessimnotanecegod1@reddit
There was another air india flight after the crash flying out from ahmedabad to london which got canceled due to technical issues. RIP.
Legal_Literature1356@reddit
According to an Air India spokesperson, the flight was cancelled due to aircraft unavailability. DGCA had ordered extended safety inspection checks for all 33 of Air India’s 787-8 and 787-9 aircraft, and most of them were grounded because of that. As a result, Air India is now facing a shortage of wide-body aircraft for many of its long-haul routes.
However, just a couple of hours ago, DGCA cleared 24 out of the 33 Boeing 787s after the inspections.
guessimnotanecegod1@reddit
It was an engine issue. Internal source.
pipic_picnip@reddit
So the source is “trust me bro”.
Away_Enthusiasm9113@reddit
6 Air India Dreamliner International Flights Cancelled Today
https://www.ndtv.com/india-news/delhi-paris-air-india-flight-cancelled-after-issue-found-during-pre-flight-checks-8690258
bobblebob100@reddit
This happens every single day. The media just want to create stories for clicks
Not____007@reddit
6 in one day from same airline?
bobblebob100@reddit
Yes. Not uncommon
https://uk.flightaware.com/live/cancelled/
Legal_Literature1356@reddit
According to an Air India spokesperson, the flight was cancelled due to aircraft unavailability. DGCA had ordered extended safety inspection checks for all 33 of Air India’s 787-8 and 787-9 aircraft, and most of them were grounded because of that. As a result, Air India is now facing a shortage of wide-body aircraft for many of its long-haul routes.
However, just a couple of hours ago, DGCA cleared 24 out of the 33 Boeing 787s after the inspections.
WispyPrincess@reddit
I read the flight which was supposed to be resumed for the route of the crash was also cancelled. Now it is AI159
Chen932000@reddit
TCMA is to cover a case where throttles are low and power is high. If TCMA believed the throttles were low (needed before it can trigger) it means the FADEC believed the throttles were low. If the FADEC believes the throttles are low though, that alone would have the FADEC cutting power. You dont need the rest of the TCMA logic to trigger at all for it to be a catastrophic situation.
fugutoxin@reddit
Thank you. I doubt that’s something taught in the simulator or even recommended as a last ditch effort when facing dual engine failure right at takeoff. But perhaps it should be. As a pilot, you should be the final arbiter of what the engines are doing. The pilot’s mayday message may be telling - “Thrust not achieved”. That sounds like a command that was given and not followed.
AeBlueSadi@reddit
I know it was very short flight but at any moment after the stall when the plane was coming down if the engines came back to full power was there any chance of lifting the plane or the crash was inevitable?
turkishguy@reddit
Someone in the first megathread did the math and said they would've needed full thrust within about 5 seconds of losing power.
Also worth noting that if this issue is at all related to the problems that caused the ANA 985 incident, that plane was never able to turn their engines back on.
Brief-Visit-8857@reddit
Probably not. They take a little bit to spool up. Maybe if they were a little higher
Alcyoneorion@reddit
Video of 787-8 having issues on takeoff retracting wheels https://m.youtube.com/watch?v=YYCq0UrinaM&pp=ygUiNzg3LTggbGFuZGluZyBnZWFyIGJlaW5nIHJldHJhY3RlZA%3D%3D
RealPutin@reddit
Not sure where you dug that up, but that's a -9 not an -8, and the gear doors automatically open after takeoff on the -9 and -10.
Alcyoneorion@reddit
The description states 787-8, however if you want to elaborate on the difference you are seeing that suggests it’s -9 that would be better than just “talking down” to someone for posting something they (I) think is relevant.
sizziano@reddit
Imagine doing even a modicum of research.
https://www.airfleets.net/ficheapp/plane-b787-38778.htm
Alcyoneorion@reddit
I could have also counted the windows but I’m not here to here to pretend I have some superior knowledge of 787s or planes just sharing a video I think is relevant
sizziano@reddit
It's not.
Alcyoneorion@reddit
It is
Temporary-Prior7451@reddit
One of those reports circulating:
Air India 171 Crash 🛠️ AAIB Preliminary Report Highlights
1. Primary Cause – Electrical Power Transfer Interruption (PTI) During Rotation • During transition from ground to airborne electrical configuration, the aircraft experienced a cascading dual-engine FADEC (Full Authority Digital Engine Control) failure. • Root cause: Uncommanded bus transfer failure due to arcing in the main power relay box (PRB-A), traced to water ingress during pre-flight GPU disconnection in heavy rain. • This led to loss of electronic engine control at rotation, resulting in both GEnx engines rolling back to ground idle within 4–5 seconds.
2. Flight Data Record Timeline • +0:11 sec: Nose gear lifts off. • +0:13 sec: Sudden engine rollback begins. Thrust reduces from 92% N1 to <27% within 3 seconds. • +0:16 sec: Master caution + ENG FAIL L/R warnings. FO calls, “Both engines dropping!” • +0:20 sec: Autopilot and flight control reverts to Direct Mode. Pitch up attitude peaks at 18°. • +0:25 sec: Aircraft stalls at 186 ft AGL. • +0:30 sec: Full aerodynamic stall; nose drops rapidly. • +0:38 sec: Ground impact at 54° nose-down attitude, 174 knots.
⸻
⚙️ Contributing Factors • Environmental Conditions: • Torrential rain during pushback. • Moisture intrusion into PRB-A connector (P/N: HLN8471) — a known corrosion-risk component. • Latent Maintenance Issue: • Power transfer relay unit showed signs of thermal damage in a previous MEL deferral 2 weeks prior. • No replacement had been conducted; aircraft was cleared under repetitive deferral. • Design Oversight: • Boeing 787 has no physical engine control backup (i.e., no direct mechanical linkage in FADEC loss scenario). • Loss of power supply to both EEC channels resulted in engine “freeze” at ground idle instead of flameout. • Flight Crew Response: • Attempted engine relight sequence not completed before stall onset. • Emergency power selector not activated — possibly due to confusion from multiple ECAM warnings.
⸻
✈️ Immediate Safety Actions • DGCA + EASA + FAA Emergency AD issued within 24 hours: • Mandatory PRB-A moisture integrity inspection on all Boeing 787 aircraft. • Temporary restriction on dispatch with MEL items related to power transfer systems. • Boeing: • Issued Service Bulletin SB-787-24-212 requiring replacement of PRB-A connectors with sealed versions. • Exploring addition of dual-path power redundancy for FADEC systems.
⸻
🧠 Lessons Learned • Over-reliance on electrical power distribution architecture without layered redundancy. • Lack of crew procedural training for full engine rollback during takeoff in EEC dual failure scenarios. • Need for improved environmental sealing in GPU/electrical handover units in monsoon zones.
⸻
📅 Timeline – What’s Next? • Aug 15, 2025: Release of FAA/Boeing electrical design audit report • Sept 5, 2025: ICAO session on electrical-critical phase-of-flight risk mitigation • Oct 2025: Mandated design retrofit across 787 fleet (rev. SB-787-24-219)
sizziano@reddit
Piss off with this AI shit that's already been debunked.
Temporary-Prior7451@reddit
Your tone and how you conveye your message says alot about you…
sizziano@reddit
That I don't tolerate misinformation? Yeah thanks.
Temporary-Prior7451@reddit
Yes, that was the message; it was clearly recieved… not responding to the tone and how you conveye it?
sizziano@reddit
This and other threads about this accident have been inundated by people spouting fake facts as if they're true or speculation as fact since day one. It's irresponsible behavior and frankly quite tiring. This specific AI "report" was already debunked yesterday rather quickly.
Temporary-Prior7451@reddit
Allright; i’ll go first about it;
my sincerest apologies for supplying you with said misinformation; honest mistake, which i now see is truly misinformation;
hey! you were right all along!
My question for you is;
Why are you being such a cunt about it, and how come i or anybody else here have to tolerate your tone?
Temporary-Prior7451@reddit
Fuck you, and fuck your tone….
RealPutin@reddit
What in the ChatGPT is this
Foreign_Towel60@reddit
I somehow saw something on YouTube with air Canada 143 , both engines failed for a completely different reason but pilots had time to make a landing and pulled of a miracle .. this was in 80s , whatever may be the reason for this if it’s indeed what looks like double engine failure , they simply had no time to recover . If it had happened bit upwards and rat would have been deployed as it’s been pointed out by several videos ,not sure if true . They would have tried to recover with time and height .. of course it’s speculation but possibility
RealPutin@reddit
Even the Gimli Glider had a decent gap between the first and the second engine failing. What's really odd here is the simultaneous dual failure - almost every time a fuel issue causes a dual failure, it's spaced apart by a minute or two
superdude311@reddit
This is true. However, those systems that used to be powered by bleed air would’ve been electronic before, it’s just the source of power generation that changes. The 787 uses batteries where the bleed air system would’ve turned a generator.
coolstorybro50@reddit
Pretty crazy that we’re going on a week after and we have NO information on wtf happened. Something stinks
Tough-Candy-9455@reddit
It's pretty standard for accidents where the cause is not obvious. For example the TWA 800 crash took like 4 years for a final report.
MyDespatcherDyKabel@reddit
Is it true that FAA & NTSB are jointly investigating the Air India crash? Or just the Indian authorities?
railker@reddit
The AAIB has launched a detailed investigation, and the U.S. National Transportation Safety Board (NTSB) is conducting a parallel probe under international protocols since the aircraft is American-made. Boeing and GE also both likely sending technical teams.
oatmeal-claypole@reddit
Surely there will be a preliminary report before then that offers some clues if not a definitive conclusion
Techhead7890@reddit
Flight Safety Detectives including former NTSB director Greg Feith put out an episode relating to the events so far. Particularly interesting was that he listed 10 different causes for a RAT to drop (around 25:00), particularly that the 787's hydraulic pumps are electrically operated; and that disruption of the crash site could hinder investigation and evidence. But they're still waiting for the black boxes to get hard info.
Not____007@reddit
For those that dont want to watch it : They basically go through and correct all the various theories going on around online. Ultimately they dont have any answers of what happened but are disappointed that the area was not cordoned off.
For those that do want to watch it : just skip the first 8 mins or so of them babbling about all the wild theorists online etc.
Thequiet01@reddit
Thanks for sharing this link.
DontLookUp21@reddit
Wait for the investigators to do their job.
https://www.instagram.com/p/DK0UH9hM_M7/?igsh=MzRlODBiNWFlZA==
torquesteer@reddit
I think you have a valid discussion point and the dismissive reply isn't going to help, so I will give a more valid 2-cent along with the lone upvote. The points are from Geoffrey Thomas so I won't try to pretend they're mine.
https://youtu.be/8Xi10A-HXv4?t=1012
a) It puts pressure on investigators to eventually release the absolute full truth under scrutiny.
b) We can leverage the robustness of the aviation community to raise (and maybe squash) theories very quickly because so many similar airplanes, procedures, and maintenance crews are still operating using methods and tools that need to adapt quickly to keep people safe.
c) Prevents hoaxes (such as the "official preliminary report" already mentioned in the comments here) from taking root.
So although so many theories are dispelled seem like people are doing fake investigations for fake internet points, there is a method in the madness in that plausible theories are discussed and possibly eliminated. We can use reddit's albeit flawed but still useful upvote/downvote system to bring forth facts.
I think the mods are doing a solid job in putting all these discussions in one place so that the subreddit doesn't become a cesspool for misinformation.
JustHarry49@reddit
Go away if you don’t want to be part of the discussion.
DontLookUp21@reddit
You mean fake investigators imagining stories without evidence for fake internet points?
laymyan@reddit
Brainstorming. You have no idea how enriching it is for the aviation community.
DontLookUp21@reddit
Really? All these fake narratives are enriching the community? Are you that delusional? lol
Chen932000@reddit
If the levers read idle and that idle was used as “good” wouldnt the engines also be using that idle as “good” and drive the power to idle regardless of TCMA? If the engines can detect the throttles being as idle is erroneous it will ignore them (maintaining power) but TCMA will also ignore them.
PrashanthDoshi@reddit
This is india you might have to wait 3 months even for report as per their civil aviation minister directed the investigation team to give full report within 3 months .
So I guess no preliminary report
Brief-Visit-8857@reddit
According to the ICAO standards, the preliminary report should be out within 30 days.
railker@reddit
And I'm sure the guidance isn't such that you need to have something substantial, you just need to issue a report within 30 days of what you know by that time.
The Preliminary Report for MH370 came out 30 days later and just said, 'This was the serial number of the aircraft, make of the engines, and how many people were on board. These are the ATC transmissions we have. Last communication and last radar ping times. SAR is ongoing. We don't know where it is.' [Heavily paraphrased].
Brief-Visit-8857@reddit
That’s an entire different case- they didn’t recover aircraft debris, the CVR or the FDR. That’s an unfair comparison
railker@reddit
And yet they still put out a preliminary report within the 30 days per ICAO Annex 13. It doesn't matter what you do or don't have, that's the due date to present what you DO have.
Tough-Candy-9455@reddit
The committee you are talking about has been primarily created to set SOPs for investigators/first responders in case of aviation accidents. It will be different from the standard investigation which is being conducted by AAIB (India) and NTSB (US), which usually releases preliminary report within a month and final report in 2-3 years.
BigHowski@reddit
Potentially dumb question here, but kind of related.
Why do big jets only have 2 black boxes? I'd have thought with the advances in tech they'd have a few of them in places likely to suffer less damages/heat etc. or likely to disconnect and been thrown clear in cases where a fire happens.
railker@reddit
Planes don't usually reverse into things, so the tail is typically a safe bet. And if they don't survive the insane G forces, pressures and temperatures they're rated for, you've got bigger problems. The ones from AF444 survived the crash and the living under 10,000'+ of the Atlantic ocean for two years before being recovered and read flawlessly. There's been VERY few accidents where recorders have been unreadable or unrecoverable.
Some1-Somewhere@reddit
In this case, the 787 has two EAFRs, each of which records both voice and data.
One is above the L1 door; the other in the tail.
Brief-Visit-8857@reddit
In the 787 it’s different. There’s 2 Black Boxes, both capture flight data and the cockpit voice. They’re placed in different area, one being the tail as it has the highest chance of survival according to statistics. In other airplanes, one black box captures the flight data and the other is the cockpit voice recorder. I suspect the main reason is money
bobblebob100@reddit
Sure i read you could do real time data monitoring that is sent back to head office too, but the cost wouldnt be worth 8t
DrSpaceman575@reddit
One part I’m still wondering is the claims of the landing gear being tilted due to a gear up command that did not complete.
If the gear had started to ascend and then the plane lost central hydraulic power due to damage to the electrically powered central hydraulic system it seems like that could explain the sequence of events we’ve seen.
If the gear were tilted for another reason then it wouldn’t mean much. I don’t think gear staying down means anything in this instance obviously the crew had bigger problems.
The only other remote possibility would be a sequence of commands from the cockpit that are so egregiously bad they would almost have to be malicious.
js5180@reddit
While I agree that the gear looks to be toes down, the landing gear doors haven’t opened yet, or at least not much, in the rooftop video. The CCTV video is less clear - it looks like they could be open.
Based on the 787 gear test video floating around, the toes-down tilt just about finishes before the doors open, so if we think the gear got stuck, the power loss had to be a second or two after the gear up command. Long enough to tilt the gear, but not even long enough to open the doors.
invertedspheres@reddit
There was some speculation on a pilot board about the possibility of the crew setting their initial altitude in the autopilot to 200 instead of say 2000 leading to a chain of events where the auto-thrust goes to idle and they fail to take manual control over the throttles. I've also seen comments saying that cycling the fuel selector knobs is a memory item for dual engine failure (which would kill their engines if they were functioning just throttled back). Reddit doesn't want to hear it, but chances are very high this was a case of human factors or pilot error.
Mcbobbings@reddit
How does that tie in with the RAT deployment?
DrSpaceman575@reddit
Technically it could be manually deployed. But again this buys into a theory with the crew hitting such an exactly wrong sequence of commands and failing to do such obvious fixes that's it's really inconceivable to me.
trader45nj@reddit
It seems inconceivable that in this scenario the pilots would not have manually moved the throttles forward in response to what was happening.
Ricky_Ventura@reddit
In response to the first or second scenario? The first scenario would automatically disengage auto throttles and they could climb out which is why they mention the pilots failing to notice.
In the second instance the issue is more that the fuel is interrupted than the throttles are back. Once you flameout there is no pulling the throttles up to regain thrust. You would need to air start and that's impossible APU off at 600 ft. The issue with this is the engine driven fuel pumps should have plenty of suction especially at takeoff power though that's also when demand is at peak.
trader45nj@reddit
In response to the scenario where the autopilot was set to just a few hundred feet or any scenario where an aircraft system moved the throttles to idle or low power and the crew didn't respond by moving the throttles forward to restore power. The engines going back to idle scenario is also pretty much ruled out by the RAT being deployed, on which there seems to be agreement that it was deployed.
Chen932000@reddit
The odds they would cycle the fuel selector before checking the throttles is what seems exceedingly unlikely.
AmbidextrousRex@reddit
Auto-thrust going to idle would not deploy the RAT though, right?
Heiter-Sama@reddit
The combination of auto-thrust idle with the engine powered would indeed satisfy once condition for the TCMA shutdown.
The other being weight on the landing gear.
Since the gear got stuck in the middle of the sequence, the combination with some sort of sensor error is one of the scenarios that leaves the least room for implausibility
Admiral_Cloudberg@reddit
Do you have a source for the dual engine failure memory items? Just curious
fabalaupland@reddit
What source or kind of damage to the hydraulic system could cause that, in your opinion?
DrSpaceman575@reddit
I think if the gear had started to retract then the only explanation that covers everything is a massive electrical fault that caused the central hydraulic pump, fuel pumps, and everything else to basically fry.
TigerIll6480@reddit
The engines have electronic controls, no mechanical throttle connections, correct? If they initiated the landing gear retraction and the hydraulic pump suffered a major short, could that potentially cause a cascade failure in the electrical system that would cut power to the FADECs? Especially if, as reported, this airframe may have displayed some electrical difficulties prior to this incident? I would assume that normally a circuit breaker would isolate something like that, but something seems to have gone catastrophically wrong right about then. A hydraulic pump failure and/or massive electrical short could account for the loud noise the survivor reported.
DrSpaceman575@reddit
I think physical damage to the wiring or electrical connections seems the most likely to me. Given how unique this problem is and how many safeguards there are against it so many systems would have to fail at once.
Some1-Somewhere@reddit
The FADECs have their own alternators powering them, mounted on the accessory gearbox and turned by the engine shaft.
The 787 is generally divided up into four electrical buses each with their own generator, plus the dedicated FADEC alternators and flight control permanent magnet generators.
theflawlessmech@reddit
I'm not sure how this works on the 787 but even with the loss of both fuel pumps, the spinning engine should turn the engine driven fuel pumps to provide fuel.
DrSpaceman575@reddit
That's what I'm still stuck on, even a failure of all onboard electronics wouldn't have just immediately cut the engines. I think something in the process told the engines to shut down or idle.
An electronic fault would cause the central hydraulics to fail, to my knowledge there's no clear evidence that the left and right hydraulic systems failed. But the gear not stowing points to electronic failure since that pump is powered electronically. Engines could still be at idle and not getting the right commands from the system.
Ricky_Ventura@reddit
It works like this on the 787. It's not considered reliable though as any significant momentary interruption will result in flameout.
Flameouts are usually pretty dramatic, though, as fuel is distributed and burned inconsistently into the combustor it often fills with fuel and as soon as the ratio of air to fuel is right the fuel ignites spectacularly. Surely something would have seen it.
Every solution has counters. Whatever did happen will be unlikely/unusual. Consequences of 13.5 years with no major losses.
Ricky_Ventura@reddit
This was also debunked. Both were from a different plane that was on the ground, APU off.
Bullfinch88@reddit
Layperson here, I've been following things relatively closely and have learned a lot from this sub over the last few days. Would anyone be able to direct me to a source with an annotated image or otherwise be able to demonstrate/explain the thinking behind the landing gear being partially retracted? Is this visible from the Aryan Asari video which captured the crash? Thanks
Vegetable_Tough4439@reddit
787 Gear Retraction Video
Check this video to see how the gear is tilted backward And only tilts forward once Gear up is selected
If you look at the original video taken from terrace The landing gear is tilted forward that hints at gear up was selected but somehow it stopped midway. You may look at 787 takeoff vids after this to get better clarity or checkout Swiss001 video
Bullfinch88@reddit
Thanks very much for this, that's extremely helpful. Am I focussing on the nose gear in the terrace video? I'll rewatch it a few times to see if I can recognise the tilt now that I have the 787 gear video for reference.
Brief-Visit-8857@reddit
I believe the gear also does that is hydraulics are lost. Correct me if I’m wrong
Vegetable_Tough4439@reddit
I have no idea about that Can anyone share some insights regarding gear tilting when hydraulics are lost.
Flimsy_Condition1461@reddit
I’ll preface this question by saying I don’t know anything about planes, but grew up around auto repair. A lot of theories circulating include fuel contamination. I was also wondering if issues with fuel injectors or fuel pumps are ever a possibility in commercial crashes?
Some1-Somewhere@reddit
They don't really have 'injectors'; turbine engines use a continual spray of fuel more akin to a garden hose: https://www.youtube.com/watch?v=oaiewQv5mn8
sizziano@reddit
That's a bit pedantic lol. These are basically injectors.
Some1-Somewhere@reddit
Combustion engine injectors like a mechanic would be familiar with have valves and often pumps integrated, because they need to dose fuel at the right time per stroke, every second stroke. Much more finicky and prone to blockage/contamination, I expect.
MidnightSurveillance@reddit
Without electrical power, the fuel pumps can stop working.
IllDot7787@reddit
I personally think this is the most possible theory.
TOAO_Cyrus@reddit
All pumps failing at once doesn't seem plausible. They are running off of multiple different AC buses from 6 different generators. To me the electrical issues seem like a symptom not a cause but who knows.
Chen932000@reddit
Even if all the airframe pumps did fail, at that altitude the engines would have no issue continuing to feed themselves fuel via their pumps.
Thequiet01@reddit
The engines should be able to suck fuel in without the pumps.
invertedspheres@reddit
IIRC, the 787's engines have their own independent fuel pumps that can supply them with enough fuel to sustain power, except at higher altitudes.
MidnightSurveillance@reddit
You may be right, I don’t know a whole lot about the systems on the 787.
invertedspheres@reddit
Almost everything critical is always designed to have redundancy in the event of an electrical failure. Even the FADEC's should have their own independent generators to power themselves as long as the engine is turning.
TigerIll6480@reddit
How do the FADECs react if there is a complete loss of inputs from the flight controls? Do they maintain thrust at the last recorded throttle position, return to idle, or shut down?
Some1-Somewhere@reddit
I have heard last commanded thrust for a certain time, then reduce to a mid-power 'cruise' thrust.
TigerIll6480@reddit
So even if a massive electrical failure shut down all of the cockpit controls, the engines should have continued running at takeoff thrust.
From everything I know about engines of any sort, even if the fuel was horribly contaminated, both engines shutting down simultaneously would be very unusual. One is almost always going to go out before the other, even if the sequence is quick, and there is no evidence of correction for a thrust imbalance.
What sort of insane combination of failures freezes the landing gear retraction at the very start of the cycle and shuts down both engines simultaneously in an aircraft with so many redundant systems?
MidnightSurveillance@reddit
Looking at a diagram for the 787 seems to be 2 independent AC buses a side and a central DC bus.
Some1-Somewhere@reddit
FADEC generators aren't shown on those diagrams as they're internal to the engines, and neither are the permanent magnet generators for the flight control computers. In both cases the backups if the dedicated generators fail is the general aircraft generators.
Some1-Somewhere@reddit
Basically all turbine engines have a mechanically driven high-pressure fuel pump on the accessory gearbox. The electric boost pumps prevent cavitation and air evaporating out of the fuel especially at high altitudes, but the engine will still operate.
Funkytadualexhaust@reddit
I doubt fuel contamination would occur exactly simultaneously with separate fuel tanks..
Flimsy_Condition1461@reddit
I’m not asking about fuel contamination, I’m asking about the fuel pump system failing.
bkirbs13@reddit
The fuel system is designed to supply fuel under gravity/suction in case of fuel pump failures.
KingInTheFnord@reddit
The question I guess is, if there was an arc fault that took out the pumps on sides causing a brief loss of fuel flow, can the engine-driven/suction fuel pumps have enough fuel flow for max thrust during take off and climb?
Do the engines lose thrust during this process? For how long? Is it possible that it’s something easy to recover from at altitude, but in this situation they simply didn’t have enough time/altitude?
Chen932000@reddit
At such low altitude there’s probably a whole lot of margin on the suction lift capability of their fuel control unit.
Some1-Somewhere@reddit
The electric pumps are only really boost pumps. They ensure positive feed pressure to prevent pump cavitation especially at high altitude, but they're not essential.
The main pumps are mechanically driven high-pressure fixed displacement gear pumps on the engine gearbox. Excess fuel is returned to the tanks after being used for oil/generator cooling.
TOAO_Cyrus@reddit
I've read that it's optimized for low altitude and high angles of attack.
theflawlessmech@reddit
The fuel filters have bypasses because the utmost importance is that fuel however contaminated gets to the engine. If all 6 tank pumps fail, then the engines have suction feed (although I'm not sure if they can provide enough pressure/flow for climb).
We will know once the investigation progresses and I'm sure it is going to be an interesting one.
roasty-one@reddit
Fuel filters don’t have bypasses. They are however, multiple pickups that mitigate the chance of debris blockage. Even if the filters were getting clogged you’re gonna get a low pressure warning from that pump. At which point the aircrew will just open the crossfeed.
theflawlessmech@reddit
Fuel filters definitely have bypass in the HMU as far as I am aware. I will have to check if it's the same on the Genx engines as well.
roasty-one@reddit
I think I misunderstood that you were talking about the engines. My apologies . My knowledge stops at the firewall shutoff valves. Other than knowing that the engine has a high pressure pump and filters and I don’t know how it all works. I was talking about the pumps in the wing tanks.
LouKrazy@reddit
https://en.m.wikipedia.org/wiki/British_Airways_Flight_38 for simultaneous and https://en.m.wikipedia.org/wiki/Cathay_Pacific_Flight_780 for more gradual
OrbitalPropulsion@reddit
I would not really call BAW38 a fuel contamination crash, it really was fuel starvation due to ice crystals restricting fuel flow. Which, due to the mechanics of it, was much more likely to be truly simultaneous than a typical fuel contamination incident. Though I'm not saying it's not possible, just not common, especially not in the specific way it happened in this flight and not in modern airliners.
really_random_user@reddit
Because there's 2 engines, fuel contamination would lead to staggered engine shutdown
Same for fuel exhaustion. The fact that they failed simultaneously is why it's confusing,
Heck for fuel contamination you'd see compressor stalls (fire spitting back) Same for bird or anything ingested in the engine. The fact that it just failed and went silet is what's confusing everyone
extratoastedcheezeit@reddit
It’s a non-zero chance, however it’s not a high probability as other flights, presumably fueled, did not have similar problems.
Brief-Visit-8857@reddit
Yep. The odds of only this flight being affected is crazy low.
throwaway-a0@reddit
Titan Airways A320 also, where maintenance error lead to fuel contamination.
railker@reddit
Low but never zero. Should be the motto of this investigation for the next couple weeks. 😁
What was that one flight took off from Malaysia or Thailand, encountered engine issues and had to land with one engine stuck at idle and another at well over half power because the fuel truck leaked some absorbent shit into the internals of the tank which clogged the aircraft's systems. Never heard of any other aircraft being affected in that case. Could just be a one-truck deal.
Elryc35@reddit
Cathay Pacific 780, from Indonesia.
Rupperrt@reddit
Has happened before
lizhien@reddit
Yes. Cue CX780.
Measure76@reddit
I don't really know this airport but it's similar in passenger count to Portland Oregon, where most of the traffic is smaller jets but they get a wide body in from London once a week.
I find it easy to believe that a certain type of contamination doesn't make it in to the smaller planes but then the big boy comes in and takes a much larger tug on the fuel straw and perhaps scrapes closer to the bottom of the barrel.
I'm not saying this is necessarily the case here, just pure speculation.
Flimsy_Condition1461@reddit
My question is not so much about contaminated fuel, but the possibility of the plane still having power but the actual fuel pump giving out?
extratoastedcheezeit@reddit
No, that’s not as likely since there are redundancies - pumps and gravity feeds.
DontLookUp21@reddit
Actually I heard it could've been a proton transmorgifier.
Respect those who.lost their lives. Wait for the investigation.
Flimsy_Condition1461@reddit
Obviously respect to the dead. But I think it’s fair to ask questions about how airplanes work.
Bramrod@reddit
Posted this in megathread 2 but still baffled. Has anyone seen any drone shots of the wreckage from above yet? I've only seen various angles from ground and building.. Hard to get an idea of how everything landed. Did the front of the fuselage end up at ground level even though the plane crashed into the 6th floor?
Comment from mt2: The thing I can't wrap my head around is this survivor. Sure he was in front of the wing / engines. But did the fuselage separate, his section was launched forward? Was he riding this thing till it stopped and jumped out? (sounds like the case) vs. catapulted out while it impacted. That explosion was so huge, I just can't imagine how he was so close and walked away. Baffling.. It would be interesting to see the crash site from above to get a better idea of where all the pieces landed..
railker@reddit
Considering the aftermath of the JAL A350 (also carbon fiber composite) that burned to the ground in 2024, just not sure there's much to see.
This post has the only image I've seen thus far.
Bramrod@reddit
So based on that pic, I can imagine how he ended up on the ground and could have had the buildings help shield fire from him. I made a real crude mockup that i imagine could show sequence of events.. imagining the fuselage probably hit the roof first and also the trailing edge of the building helping split the fuselage, separating it where it hit the ground and slid forward on the ground until it contacted the building or hit something to stop it..meanwhile this guy somehow overcame all the forces + heat and escaped. Wild.
Bramrod@reddit
Funny and just after I made that I found this diagram online.. I guess I wasn't too far off..
Silent-Treat-6512@reddit
How surprising is that during 911 the Boeing 757/767 were able to bring 2 twin towers down to rumbles even with near half the fuel tank, however a 787 with near full tank was not able to bring a 5 story building.. #insiderjob
texasradioandthebigb@reddit
Oh, shut the fuck up
pipic_picnip@reddit
Are we seeing the same photos? Your comment doesn’t make sense.
First of all it wasn’t the impact of the planes itself that brought down the twin towers. If you are bringing up 9/11, you would know the towers held up until the extremely high heat warped the structural integrity of certain parts of the tower and it collapsed on itself under the weight. Which is why 9/11 incident served as benchmark for ground breaking improvements in architecture because the twin tower design had serious flaws in it as no one had designed the towers keeping in mind multiple planes blasting into it. It was one of those “unheard of” situations like aliens attacking that you only rectify after it happens.
Secondly, look at the scale and distance travelled of this blast. The aircraft is on far left. But the blast has covered enough distance to impact 4 adjoining buildings that are not directly hit. We know for a fact that the resident building next to the mess was completely annihilated upon impact. Each building would absorb a lot of impact reducing the impact to the next building.
Lastly, Indian builds by default do not use a lot of wood in their foundational structures. They use concrete, cement, bricks with only minor finishing work like doors and window sills out of wood. Considering the kind of structure, this kind of damage is reasonable, because everything except the structure seems to have taken the brunt, and although concrete structures have a tendency to stand despite heavy impacts like this, it doesn’t necessarily mean they are fit for living or restoring anymore. Most likely they will demolish them and start over from scratch.
Thequiet01@reddit
Completely different building structure. Completely different stress profile on the building, too.
mjlky@reddit
gently planting a stick in the ground vs. shooting a rocket launcher at a wall
Tasty-Ingenuity-4662@reddit
Oh come on. During 9/11, the planes crashed INTO the buildings. Here the plane crashed on the ground in front of the buildings. Sure you can see a little bit of a difference here.
feignsc2@reddit
The 171 pilots weren't trying to crash into the buildings and the kinetic energy proportional to the square of the velocity.
Bramrod@reddit
There we go. Thanks for the aerial shot I hadn't seen something like this yet. Still baffling but interesting to see how everything landed.
PestyNomad@reddit
It crumpled in a way that spared him.
Rupperrt@reddit
Apparently one of the walls of the building they hit shielded him from the immediate fire blast before he could jump out through a broken door. And it’s been theorized that his seat, and not having seats right in front of him protected him from being squeezed during impact. Still an insane deceleration from 200km/h to zero and miraculous he didn’t lose conciseness.
Few-Media6255@reddit
The survivor said that, green and white lights came on. Is the colour of lights or them coming on in any way significant or give any specifics?
Brief-Visit-8857@reddit
Emergency lights in the 787 are green and white
Few-Media6255@reddit
Thank you, was checking this, if they come on automatically for a specific reason or if they can be turned on manually too
Brief-Visit-8857@reddit
They come on automatically if the airplane detects that electrical power is lost. I think they can be turned on manually too, but highly unlikely in this case. The pilots would be trying to fight the aircraft
Few-Media6255@reddit
Thank you
sizziano@reddit
It's speculated it was the emergency lighting.
Few-Media6255@reddit
Ok thank you
777978Xops@reddit
https://www.reuters.com/sustainability/boards-policy-regulation/india-regulator-asks-air-india-training-data-pilots-dispatcher-crashed-plane-2025-06-17/
Indian regulators have asked Air India to submit training data for both pilots and also information on the dispatcher of the aircraft before Monday.
sizziano@reddit
Fairly standard.
777978Xops@reddit
I know just sharing updates
sizziano@reddit
I'm just commenting.
RX142@reddit
Avherald reports:
RX142@reddit
The source of the comment could be this guy, who comes up when you search "former air india captain" commenting on this incident in the last day. Perhaps the full video from that news agency contains this captain's comments. In any case, him being trained by the late Captain would be quite a bias to take into account.
RX142@reddit
Does anyone else have a quote from this captain? I can't quite tell if "It is becoming gradually clear from the newly emerging evidence" onwards is avherald's opinion or that captain's opinion.
Vegetable_Tough4439@reddit
Aerial Image of Crash Site
If you look at extreme right of this image (zoom in) where ambulance and firetrucks are coming out on to the road That is the gate where the survivor walked out of and if you look in the viral video of him walking out he seems to be coming out from opposite direction of the buildings That means from right side of where two ambulance (looks like) are standing right at the gate.
This is what i could come up with what i have seen in video and from google maps The only reason i have written is it still baffles me that how he ended up there (being in left side of aircraft) and also came out from opposite direction of buildings
muhmeinchut69@reddit
Anyone have the original for this image : https://i.ibb.co/xKtj3mMQ/image.png
WispyPrincess@reddit
It was posted here today
https://www.reddit.com/r/aviation/s/LiFxwNnCgM
muhmeinchut69@reddit
Thanks, I missed that post.
Technical_Yak_4112@reddit
Hey everyone, I’ve always been an AIC enthusiast, I know some of the basics of the configuration and build of Aircrafts etc but I am no Pilot or Mechanic and have been following crashes since I’m like 6.
There have always through history been accidents that were unprecedented and issues were faced that had never been faced before. It seems it’s same case AI171.
With all the info we have on the crash and all the info available regarding the 787-8 manuals, what would be basic cause of the dual engine failure in terms of mechanics?
The outcome is too vast to be pinned down to one issue, but what do we think as a community could be something that we haven’t focused on enough
Ricky_Ventura@reddit
No one knows. The airframe flew globally for 15 years without a loss. What actually happened will be a freak combination of compounding accidents that has never occured and may well never again occur. Dual engine failure usually comes down to either fuel interrupt or compressor stall/interrupt and, well, there's plenty of issues with both to make either very unlikely.
stbtnjtonj@reddit
Did some digging after reading an excellent analysis in megathread 2, this article provides another explanation to various system connections and possible issues: TOGA, Autothrottle and FADEC Malfunctions in Boeing 787 Dreamliner During Takeoff and Climb: Causes, Risks, and Solutions https://www.linkedin.com/pulse/toga-autothrottle-fadec-malfunctions-boeing-787-dreamliner-during-ouxpf?utm_source=share&utm_medium=member_android&utm_campaign=share_via
True-Industry-4057@reddit
I read through this analysis and based on the phrasing and formatting I half suspect it to be AI generated slop.
Some1-Somewhere@reddit
Definitely AI generated; remarkably few falsehoods, still not actually that useful.
vintain@reddit
Probably belongs in LinkedInLunatics.
russbroom@reddit
I just stumbled upon this video on FB that I feel highlights the difficulty in conducting a thorough investigation of this particular tragedy.
MidnightSurveillance@reddit
First news article came out suggesting dual engine failure.
pipic_picnip@reddit
They haven’t said anything new in the article though beyond what everyone already knows. So they are pretty much spitballing ideas like the rest of us, only that being a media house they should be more careful to publish things with no basis.
MidnightSurveillance@reddit
Agree. And their only source was “the times”. But this is the first article I’ve seen that explicitly addresses engines. Most other ones are repeating capt. Steve’s horseshit.
Brief-Visit-8857@reddit
Yep, it definitely was a dual engine failure
Rupperrt@reddit
Most likely a dual loss of thrust yes. Which can be caused by an engine failure or by another failure in the fuel or engine monitoring software causing total or partial loss of thrust.
norman_9999@reddit
Still to be verified but it looks like a catastrophic electrical failure on rotation.
Flight: AI-171 | Aircraft: Boeing 787-8 | Date: June 25, 2025 | Route: Ahmedabad (VAAH) → London Heathrow (EGLL) Crash Site: ~1.2 km from VAAH Runway 23, post-V1 and rotation Fatalities: 247 (243 onboard + 4 ground) Survivors: 1 onboard survivors (alternate to original), 3 injured on ground
🛠️ AAIB Preliminary Report Highlights
Primary Cause – Electrical Power Transfer Interruption (PTI) During Rotation • During transition from ground to airborne electrical configuration, the aircraft experienced a cascading dual-engine FADEC (Full Authority Digital Engine Control) failure. • Root cause: Uncommanded bus transfer failure due to arcing in the main power relay box (PRB-A), traced to water ingress during pre-flight GPU disconnection in heavy rain. • This led to loss of electronic engine control at rotation, resulting in both GEnx engines rolling back to ground idle within 4–5 seconds.
Flight Data Record Timeline • +0:11 sec: Nose gear lifts off. • +0:13 sec: Sudden engine rollback begins. Thrust reduces from 92% N1 to <27% within 3 seconds. • +0:16 sec: Master caution + ENG FAIL L/R warnings. FO calls, “Both engines dropping!” • +0:20 sec: Autopilot and flight control reverts to Direct Mode. Pitch up attitude peaks at 18°. • +0:25 sec: Aircraft stalls at 186 ft AGL. • +0:30 sec: Full aerodynamic stall; nose drops rapidly. • +0:38 sec: Ground impact at 54° nose-down attitude, 174 knots.
Contributing Factors • Environmental Conditions: • Torrential rain during pushback. • Moisture intrusion into PRB-A connector (P/N: HLN8471) — a known corrosion-risk component. • Latent Maintenance Issue: • Power transfer relay unit showed signs of thermal damage in a previous MEL deferral 2 weeks prior. • No replacement had been conducted; aircraft was cleared under repetitive deferral. • Design Oversight: • Boeing 787 has no physical engine control backup (i.e., no direct mechanical linkage in FADEC loss scenario). • Loss of power supply to both EEC channels resulted in engine “freeze” at ground idle instead of flameout. • Flight Crew Response: • Attempted engine relight sequence not completed before stall onset. • Emergency power selector not activated — possibly due to confusion from multiple ECAM warnings. ✈️ Immediate Safety Actions • DGCA + EASA + FAA Emergency AD issued within 24 hours: • Mandatory PRB-A moisture integrity inspection on all Boeing 787 aircraft. • Temporary restriction on dispatch with MEL items related to power transfer systems. • Boeing: • Issued Service Bulletin SB-787-24-212 requiring replacement of PRB-A connectors with sealed versions. • Exploring addition of dual-path power redundancy for FADEC systems. Lessons Learned • Over-reliance on electrical power distribution architecture without layered redundancy. • Lack of crew procedural training for full engine rollback during takeoff in EEC dual failure scenarios. • Need for improved environmental sealing in GPU/electrical handover units in monsoon zones. Human Toll • The loss of 243 onboard lives, including 12 crew and 18 infants, deeply impacted the aviation community. • Final words captured on CVR: “We lost everything – no thrust!” • One family of five was killed on the ground in a hospital ambulance struck by debris. Timeline – What’s Next? • Aug 15, 2025: Release of FAA/Boeing electrical design audit report • Sept 5, 2025: ICAO session on electrical-critical phase-of-flight risk mitigation • Oct 2025: Mandated design retrofit across 787 fleet (rev. SB-787-24-219)
railker@reddit
Dated in the future and transcript from a CVR that was just recovered in the past two days. And ECAM is an Airbus system, Boeings have EICAS. And I doubt torrential rain was happening during pushback. Probably some AI output someone (not you! This has appeared before) is trying to pass off as legitimate.
PourLarryaCrown@reddit
Those wingtip vortices kicking dust a hundred feet in the air on rotation would seem to dispel any chance it was raining torrentially a few minutes before when they were pushing back.
Stealth022@reddit
This "report" has been confirmed to be false and entirely fabricated
norman_9999@reddit
Sorry. I didn't know. It came through a work relates source, so I had more faith in it than others. Ill remove it as I don't want to spread false information.
Stealth022@reddit
All good. When I first saw your comment, it looked legit until I dug deeper, haha
SubarcticFarmer@reddit
I was looking at that and trying to figure out where they actually could have even gotten some of that information this fast. I could see some of the items but it read more like a final report than an initial one.
RyboPops@reddit
wut
Mysterious-Sir-9795@reddit
FIRST!!!