What are some of the more unusual or unexpected aircraft “safety” features you know of?
Posted by sledge98@reddit | aviation | View on Reddit | 207 comments
sledge98@reddit (OP)
I’m an aviation/space content creator and was inspired by the post the other day about the 747 takeoff abort(https://old.reddit.com/r/aviation/comments/1k5y9f9/aftermath_of_747400_rto_19_apr_2025/)
I am looking for some other suggestions of weird or unique safety features of both airline and military aircraft that could be showcased in a future video.
Yesterday’s post was the first time I’ve heard of the fusible plugs that are used to safely deflate air craft tires. One other example that immediately came to my mind is that engines are designed to shear off when experiencing to forces that could damage the wing.
I appreciate any expertise or ideas you can provide and thank you for taking the time to read my post. - Sledge from https://www.youtube.com/@That-Happened
clear_prop@reddit
FAR 25.795(c) (1) Least risk bomb location. An airplane must be designed with a designated location where a bomb or other explosive device could be placed to best protect flight-critical structures and systems from damage in the case of detonation.
https://www.ecfr.gov/current/title-14/chapter-I/subchapter-C/part-25/subpart-D/subject-group-ECFR9bfdfe36b332e4a/section-25.795 https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_25_795-6.pdf
sledge98@reddit (OP)
Thank you! I havent seen this one before!
ColonelAverage@reddit
I'm a bit late to the party but my favorite tidbit is that there are ashtrays installed on every plane that carries more than 20 people.
They aren't there because smoking was legal, they are because PAX will smoke no matter what and they need somewhere to put their cigarette out. This is further unusual because the regulation itself offers redundancy: 25.853 (g) says "Regardless of whether smoking is allowed in any other part of the airplane, lavatories must have self-contained, removable ashtrays..." Whereas regulations by and large would not normally include that "regardless" part.
Folks smoking in the lavatory is such a fear that the redundancy goes even deeper. Smoking is illegal but they will remind you it's illegal every flight briefing. Even though they do that, there's an ashtray. Even though there's an ashtray, there is required to be a fire extinguisher in the lavatory waste bin. Even though there's that fire extinguisher, the waste bin must be able to contain a fire without the use of the fire extinguisher. Even though the bin must contain a fire, the structure the bin is in must also be able to withstand a fire in case someone forgets to replace the bin. Even with all this the lavatory smoke detector must trigger an alert on the flight deck. Even with all of this, at least one manufacturer requires the lavatory to be filled with paper towels, lit on fire, and contain that fire
Then we start to get to just general flam requirements vs just protecting against smoking, but everything on the plane is required to be demonstrated to pass specific flammability tests. When I worked in flam I burned hundreds of test articles to prove every color, thickness, combination, orientation, etc of material we installed was safe. When you board an airplane, your clothes are the most flammable thing you will see other than any paper products.
Far-Condition8586@reddit
Ditch the dumb Fortnite font click bait thumbnail for starters
sledge98@reddit (OP)
The purpose of thumbnails is to get you click. They're only "bait" if they don't deliver on the promise. So I'm not sure about the issue here.
Imgjim@reddit
Actually, I'm going to agree about ditching your thumbnails, but not for the same reason. I immediately thought the same thing about them "here we go, a video with a manic narrator, jump cuts, epileptic highlight animations, and poorly written jokes forcefully smashed into poorly researched content" but then I watched a few of your videos... They are very old school. Paced, informative, well edited, and... Watchable. So actually I would call those thumbnails click bait, as they don't represent your style at all... You're better than that. I would urge you to AB test a couple different styles of thumbnails on the same content, you may find you get more views and better engagement.
sledge98@reddit (OP)
I appreciate the feedback. Can you provide any examples of thumbnails from similar creators that don't give that vibe?
The issue with the "you're better than that" justification is that as a small channel you sometimes can't follow the thumbnail trends of successful channels. There are some large channels in my niche that i would dmsay have terrible Tobago thumbnails but it doesnt matter because they are already well known and people click for them. no matter what.
Whereas a good thumbnail design has to have minimal elements and be readable as a very small picture. My design goes with a solid background and a couple highlighted elements for that reason.
If i had think of someone 'similar' to my style i would perhaps note the "Found and Explained" channel or "Rex's Hanger."
I am open to suggestions and changing my methods. One recent change I've done is adding a small element of background than then fades into the blueprint. Is the change really a simple as a different font?
Imgjim@reddit
I like wendover's thumbnails, also found and explained is good stuff too. Yeah, why not just try a font change and see? If you have access to the thumbnail ab tool it's easy.
sledge98@reddit (OP)
TIL a font can be click bait. 😆
IoGibbyoI@reddit
Many, but not all, tail mounted aircraft engines have engine safety bolts that aren’t designed to hold the engine on, but to ensure the engine rolls away from the aircraft in the event of a separation. Falcon 2000s have this feature as well as some other Pratt equipped aircraft.
sledge98@reddit (OP)
Interesting, like it controls the direction they go after separation?
IoGibbyoI@reddit
It doesn’t control the direction. The bolt is in a position that if the engine comes off the mounts, the bolt acts as a pivot and breaks, forcing the engine to rolls away from the fuselage.
sledge98@reddit (OP)
Right, that's kind of what I was thinking. Thanks for explaining it to me.
Freddan_81@reddit
Shearing off in case of a gear up landing, not in mid flight.
dabarak@reddit
No, they're actually designed to shear off in flight, My understanding is that if an engine seized up and stops spinning, the high drag it would cause could result in hard-to-control yaw in the direction of the bad engine. In worse cases, I suppose the wing's strength could be compromised.
I don't know if this applies to engines on the fuselage.
sledge98@reddit (OP)
I was able to find this 727 that lost a fuselage mounted engine when it ingested frozen lavatory discharge. https://asn.flightsafety.org/wikibase/147064
mattblack77@reddit
Eg…..when the shit hits the fan?
sledge98@reddit (OP)
Lol
Mountain-Captain-396@reddit
They aren't designed to shear off on the ground or in flight specifically, they're simply designed to shear off if they are subject to enough force to damage the wing. The idea is that the engines will rip off before they are able to damage the wing substantially.
It's very rare for aerodynamic loads alone to actually shear the engines off. The only case of this happening that I remember off the top of my head is a Boeing 707 test flight where they lost control while doing a dutch roll demonstration.
A seized engine will cause extra drag leading to a yaw to one side, but it is well within the control limit of the rudder. That is why you have a Vmc speed (velocity minimum controllable) on a multi engine aircraft, which is the minimum speed needed to give you enough rudder authority to counter the yaw.
Hot_Net_4845@reddit
Here is a Mentor Pilot video regarding the 707, if anyone is interested
KaptainSet@reddit
Why downvote
TweakJK@reddit
Many passenger aircraft have a fire extinguisher in the lavatory trashcan. The end is covered in solder or wax, and melts when someone throws a lit cigarette in it, extinguishing the fire.
ColonelAverage@reddit
Yes! They are really neat too! They are about the size of a baseball and are one of the last exempted uses of the CFC Halon, which is a strong ozone depleting chemical. Halon puts out fires extremely well. Startlingly well, it's fun to watch it extinguish something. It's also able to be breathed in concentrations that are above the concentration required to put out a fire.
Btw, even though they have this fire extinguisher, the FAA still requires the waste compartment to be passively fire safe without the extinguisher (and with a couple minor fireproof features disabled). The tests I've seen only allowed basically the very top layer of trash to burn before being snuffed out. That test is also fun because part of the required trash mixture for the test includes cigarette boxes so when we would run a couple of those tests, we would submit an expense report for several cartons of cigarettes.
TweakJK@reddit
I want your job
AviationNerd_737@reddit
B737 Max 'self balancing' nature of the engine after severe imbalance-induced vibrations, which relies on a frangible part afaik. Controversial for its tendency to dump oil fumes down the bleed system.
IoGibbyoI@reddit
Can confirm I always smell oil on every engine start in a 737 Max.
approx_volume@reddit
That has nothing to do with the Load Reduction Device (LRD), which only “activates” with a very high energy load like a fan blade out. Any aircraft that relies on a bleed system from the engine to supply cabin air can ingest air with a slight petroleum smell.
IoGibbyoI@reddit
Oh I knew about the oil smell stuff. I’m always surprised how strong it can be on the newer airliners. I didn’t know about the Load Reduction Device.
747ER@reddit
Is this only on the -1B, not the -1A or -1C?
approx_volume@reddit
It’s on all LEAP engines, GE90-115B, and GEnx engines.
Kojetono@reddit
As far as I know all versions have it, just luck would have it that the only engines that experienced this issue were -1B.
AviationNerd_737@reddit
Don't quote me on this, but probably -1B.
Interesting observation and discussion this evoked, from my students... definitely shows how freakin' complex these systems are.
sledge98@reddit (OP)
Interesting stuff, I will look into this one more. Thank you!
Lava_Lamp_Shlong@reddit
Didn't expect to see a legend today, hi sledge how u doin
sledge98@reddit (OP)
I'm doing alright thanks!
Bon-Bon-Boo@reddit
Mentour Pilot on YT has good video about it. He’s trying to create an awareness about that dumb design.
TireShineWet@reddit
link for anyone wondering like I was: https://youtube.com/watch?v=swlVkYVSlIE
human_totem_pole@reddit
The very first versions of the 747 had a hatch in the cockpit ceiling with a Sextant so the flight crew could navigate using the stars if the aircraft navigation systems became degraded or failed.
The_Ashamed_Boys@reddit
It's a port that you slide the sextant into, open the valve then push it all the way into the slipstream.
I used to fly 747s (not the ones with sextant ports), and some of the older crew members told me about this flight engineer from when they flew the old 747s and his trick during flight was to launch marbles out the sextant port. Open it up and it sucks the marble up and launches it straight up. Pretty fun party trick as I assume it made a fun noise when the marble went out.
Well when these planes were undergoing heavy checks, they were noticing damage on the vertical stabilizer. So he had to stop since 500mph marbles to the vertical stab causes damage.
FreshSky17@reddit
I wonder how many random people were hit by marbles from the sky like what the fuck
Plotinus_Aureus@reddit
Most people would be shocked at the impact force that marble will make dropping from high altitude…you would not want that to hit anyone!
The_Ashamed_Boys@reddit
It's mostly oceanic flying so maybe fish ate some.
ProbablyBeOK@reddit
I knew guys on DC-8’s that did the same thing with a roll of toilet paper, stick a screw driver through the roll, open the port and let suck it out.
scotty813@reddit
As soon as I read launching marbles, I instantly thought, "Huh, I wonder how many hit the rear stabilizer and why didn't the captain stop it."
Professor_Airplane@reddit
The Air Force E-3 (AWACS) has a sextant port too. The flight crew would launch hard-boiled eggs from it. (Hard-boiled eggs were part of the standard AF crew meal packages.)
navair42@reddit
The P-3 had them too. My dad used to tell stories about betting his Navs beer if they could do a celestial fix within so many miles of their actual position. I also flew the P-3 25 years after he did but never got to see the sextant port used. I wish I had known about the boiled egg trick. We had the free fall chute to throw things out of when desired or needed.
Shankar_0@reddit
We had that in the E-3 (heavily modified 707) as well.
FYI, you can eject a shelled, hard-boiled egg right out of there with just the cabin differential.
Or, so the story goes...
Bosswashington@reddit
C-130s had this also. We use it to run prop balance wiring from the flight station to each engine, so we can close the doors during high power turns.
Draknurd@reddit
I heard this was used more as a way to smoke in the cockpit
loose_as_a_moose@reddit
Now we have to use the lav drain like Neanderthals.
retflyr98@reddit
C-141A (Starlifters) also had a sextant port. For a while, it was base policy, at McGuire AFB, NJ, to vacuum the flight deck, with the hose provided for each aircraft, during the final leg of operational missions. That procedure stopped when damage was also found on the vertical stabilizer from debris from the flight deck.
sledge98@reddit (OP)
Historical safety systems would be cool to include in my video. Thank you for this!
Worried_Place_917@reddit
Not aircraft structural, but I worked parts for a C-check line for Embraer, and a disposable BIC razor was on the MEL. Literally cannot fly without it.
Eventually did some asking and it's part of the med kit tied to the AED, so if you have to try and adhere electrode pads to a man with a hairy chest...
Vau8@reddit
I just learned at this very sub that the rims of the main landing gear of some airliners are fitted with fuses to let the air out of the tires so that they don't explode if they get too hot during emergency braking.
approx_volume@reddit
Yeah it is required as a part of compliance to 14 CFR 25.735, if the brake system is integrated into the wheel assembly, as outlined in the guidance in AC 25.735-1 (see subsection (g)).
datguyfrom321@reddit
Fighters have this too. We had a pilot reject takeoff after forgetting to close his weapon bays before starting his roll, rejected takeoff just below his rotate speed and when he stopped both main tires blew. Great times.
mk_dnk@reddit
A lot of smaller jets have this feature too. Use to fly a Honda Jet and had the fuse plugs blow after a high speed rejected takeoff. Word of advice, try to avoid setting the parking brake after a high speed RTO or your brake pads might fuse to the rotors. Ask me how I know lol.
gobirds1984@reddit
How did you like flying Honda's? I used to work on them and always heard about how underpowered the brakes were.
mk_dnk@reddit
The flying part was great! The ground stuff was another story. I flew all the models and they did a decent job rectifying issues with the E2’s. I use joke with newer Honda pilots that there are mins, personal mins, then Honda mins. Realistically though, as long as you respected the numbers, the plane would respect you. I worked for both of the two largest Honda operators before they both shut down and most of our pilots were very conservative with their calculations. I wouldn’t be surprised if you’ve worked on a plane I’ve flown.
gobirds1984@reddit
Hahaha I probably have. We had one Honda that sat in our hangar for over a year because during the 600hr, the company that flew that plane ended up closing.
Vau8@reddit
Well, that's an lasting insight.
Blindman081@reddit
Tires have thermal plugs. Has nothing to do with the rim.
Sparta954@reddit
The fusible plug is on the wheel/rim it is not on the tire of any aircraft I've ever worked on or seen
sledge98@reddit (OP)
Yes! That is exactly what inspired this post! Unfortunately my comment explaining my purpose of this discussion is downvoted at the bottom right now.
Vau8@reddit
Oh dear, sorry mate, I hadn't seen it down there ;) I guess people find your picture a bit too, well, sensational. It's quite a technical and sober bunch here, sometimes a bit punny and childish (what adult watches airplanes?), but sensationalism is frowned upon.
sledge98@reddit (OP)
Ah perhaps, I quickly made up that picture to be eye catching and sensational so that's on me hahaha
dos_torties@reddit
Nitrogen gas inerting in the fuel tanks to prevent gas fumes.
Also, I recently learned that the flap door on the lavatory garbage can is fireproof, in the event someone throws away a lit cigarette and it ignites. It’s got me curious about other small fireproofing designs around the aircraft, too!
approx_volume@reddit
Nitrogen gas inerting doesn’t prevent jet fuel vapor, but displaces oxygen so the total oxygen concentration is below the flammability limit for combustion to happen.
Jet-Coyote@reddit
The garbage can also has a small automatic halon bottle to extinguish the fire. It's indicated to the crew when the bottle is used so they know to shut the lavatory until the bottle is replaced or refilled.
rkba260@reddit
We don't have any indications of a lav fire suppression system deployment on the flight deck. Before every flight, the under sink bottle is checked, if it's been deployed it changes color.
loose_as_a_moose@reddit
Ships I worked on just had two rods with a low melt alloy plugging then. Had to check each flight the plugs were attached.
You’d probably notice the fact the lav waste compartment was suddenly charcoal coloured and smells like aromatic cancer - but sure. Check the fuse rods. Lmao.
MikeUp@reddit
Can't push back without a working ashtray in every lav for this reason.
sledge98@reddit (OP)
Is deployment automatic when fire is detected in the garbage?
rkba260@reddit
Yes. It's heat activated.
sledge98@reddit (OP)
Interesting. Thanks for the info.
MikeUp@reddit
Can't push back without a working ashtray in every lav for this reason.
GrafZeppelin127@reddit
After the TWA 800 disaster, one can certainly see the usefulness of nitrogen inerting systems—but perhaps lesser-known is that the Hindenburg nearly used a similar system with a helium gas sheath surrounding its hydrogen gas cells. The pure hydrogen, ensconced inside and lacking any oxygen, couldn’t burn or explode, and the hydrogen could then be safely used as fuel and antiballast as well without wasting any of the rare helium gas.
However, the Americans, who held a monopoly on helium at the time, prevented its sale to the Zeppelin Company on the basis that the Company’s leadership had experienced a hostile takeover by the Nazis following their President’s open criticism of Hitler. The concern was that the Hindenburg could have its helium siphoned off and used for military purposes, or the Hindenburg itself could be converted to military use, as had happened with civilian Zeppelins in World War One. During that conflict, not once was a Zeppelin successfully shot down by airplanes unless the planes managed to catch the hydrogen on fire, and machine guns proved utterly incapable of doing so until the invention of the incendiary bullet. Even bombing them repeatedly only worked once, after the sixth bomb in a row managed to start a fire that consumed the Zeppelin LZ-37 in early 1915, which would remain the first and only Zeppelin brought down by aircraft until the invention of the incendiary bullet in late 1916.
The Nazis almost certainly wouldn’t have used fireproofed Zeppelins in frontline military applications as the Imperial Germans had done early in World War I, as it became clear after the war that the Zeppelins were far more successful as antisubmarine scouts and ultra-long-distance cargo vessels, and cutting off their helium access when the war broke out would have very quickly rendered the question moot anyway.
Annual-Advisor-7916@reddit
Since you seem very knowledgeable about airships; what's your opinion on the flare-theory that is said to have caused the fire of the R101 when it crashed?
GrafZeppelin127@reddit
Honestly, that ship was such an engineering clusterfuck, such an absolute omni-shambles in both design and execution that trying to narrow down what exactly caused the fire is probably impossible. It could have been any number of things.
The calcium flares being water-activated and situated below the water ballast piping is just one potential culprit among many.
Darksirius@reddit
I was 14 when twa 800 happened. I still remember all the news footage.
GrafZeppelin127@reddit
It was, in its way, a far worse version of the Hindenburg disaster, since all 230 aboard perished versus only a third of the passengers and crew of the Hindenburg. Granted, TWA 800 is not quite so infamous, since it was not visually recorded, and the Hindenburg coming down in flames was the first and last accident with any passenger fatalities of the Zeppelin Airline, and the first major catastrophe ever caught on film.
To this day, both accidents have spawned a great number of baseless conspiracy theories, but more importantly they have both spawned a great deal of reform regarding the treatment of flammable substances on aircraft. Hydrogen lift gas was banned in many countries following the Hindenburg disaster, and commercial airliners in the wake of TWA 800 have introduced active and passive safety measures including nitrogen inerting to prevent their fuel tanks from exploding.
dos_torties@reddit
Well that’s a fun fact right there. Thanks!
Also, username checks out ✔️
WoundedAce@reddit
We still use nitro, it’s cool
nighthawke75@reddit
Carbon dioxide. Not nitrogen.
Kojetono@reddit
They use nitrogen, as it can be extracted from the air and doesn't need storage tanks on aircraft.
kilosoup@reddit
Unless you're Lockheed Martin. Even with the massive upgrades and overhauls in the 2010s, C-5s still carry 1500 pounds of liquid nitrogen on board for fuel tank inerting.
railker@reddit
You mean Nitrogen?
nighthawke75@reddit
US Navy used CO2 for ages as a blanketing system for their onboard fuel tanks.
This nitrogen extracting system is new to me. We could use that in fields to inject gaseous nitrogen into the soil.
GrafZeppelin127@reddit
No, plenty of aircraft do use nitrogen, I assure you.
spacegenius747@reddit
I think I remember a video about how the 737 max has a mode where the spoilers can act as ailerons in an emergency but I don’t really remember
Key_Research7096@reddit
A lot of planes have that, they're called roll spoilers
Disastrous_Drop_4537@reddit
On some planes that's all they've got. Beechjet and later b52s are two of the top of my head
Baruuk__Prime@reddit
737-800
Frangible Fitting.
This device is located immediately next to the Main Gear Wheel Wells on the aircraft. If a tire is ruptured and the gear is retracted, the shreds of the tire would destroy the Frangible Fitting and that would remove the hydraulic up-pressure on the gear, letting it come down again and light off a warning in the cockpit.
amcl1986@reddit
The door to the flight compartment is bulletproof, but the wall either side of it isn’t.
RobotGhostNemo@reddit
Some aircraft engine turbines are designed such that, if the turbine approaches dangerous speeds, the deformation of turbine rotor blades will cause it to hit the stator vanes and basically obliterate the turbine section, therefore preventing further acceleration of the spool.
nlhans@reddit
A350 has a safety feature in which the plane will automatically emergency descent when the cabin altitude gets above 14000ft. It does: https://www.faa.gov/sites/faa.gov/files/2022-11/FCOM_A350_Emer_Desc.pdf
So in short, if a pilot was still hand flying the plane at this point, its basically told to sod off lol. They also use it for "manual descents" because the AP mode is programmed so aggressively it will fly the planes all the way up to the barber poles and even a bit in the overspeed to minimize the descent time.
Imagine what kind of work has gone into this feature. You never would want to trigger this accidently. It would ruin an oceanic crossing if that happened with potential TCAS conflicts.
Tragically, accidents have occured because earlier planes didn't have the tech to do this. Example Helios Airways Flight 522, the pilots forgot to pressure the cabin after take off, checklists were missed, and the plane tragically crashed despite a cabin attendent reaching the cockpit trying to figure out what to do.
FarButterscotch4280@reddit
*emergency descent when*
That would be annoying if you were flying over the Himalayas, or Andes
AverseAphid@reddit
Which is why commercial aircraft never fly over the Himalayas and very rarely fly over the Andes. The emergency descent also only lowers to the MORA or <10,000 feet, whichever is lower.
Key_Research7096@reddit
I remember hearing something about if both windshield panels an A320 are blocked the pilots would fly with their head out the window
This_Elk_1460@reddit
I'm a big fan of the rat
PickleJuiceMartini@reddit
Ram Air Turbine
iboreddd@reddit
Some military jets have return-to-base trigger affiliated with the pilots health (pulse, heartbeat etc). If aircraft thinks pilot lost consciousness, it automatically create a waypoint to closest friendly airbase
quietflyr@reddit
Do you have a source for this?
iboreddd@reddit
I don't. I've worked on aircraft architecture
quietflyr@reddit
I ask because I've been working on military aircraft for 20 years, and very closely follow advanced technology integration as part of my job, and I've never heard of any production aircraft having any pilot monitoring whatsoever. No heart rate, no blood oxygen, no brain activity, etc. Pilots just don't wear sensors for that, and if they did, there are so many situations where erroneous data could be provided to the aircraft. It would just be wrought with problems, for a situation that virtually never occurs.
There is Auto-GCAS, which will recover an aircraft from a scenario where an unresponsive pilot would crash into the ground, but that's not based on the pilot's physiology, it's based on warning the pilot and automatically recovering if they don't try to recover on their own. And it definitely doesn't fly you anywhere, it just brings you back to level flight at a safe altitude.
iboreddd@reddit
It's a part of 5th gen (and supposedly 6th gen) aircraft feature. There's a dedicated subsystem which collects data from sensors (yes health sensors too), HMD and even HUD. Then fuse together and try to create meaningful data.
Regarding auto-landing, yes modern FCSs do have this functionality and they also get data of friendly or ally airbases from mission data per flight.
quietflyr@reddit
You know HUD and HMD are not sensors, right?
I never said auto land wasn't a feature that existed. Hell, Garmin offers it for light aircraft, and it has saved lives.
But I still fail to see the actual realistic business case for a system this complex, expensive, and prone to errors, which is only useful in extremely rare scenarios.
iboreddd@reddit
Yes but some of them have eye trackers.
What I saw was (cannot give details due to NDA) applicable only on operations when there are friendly airbases closer than xyz km. However, since data fusion itself is a new technological concept, it prone to errors as you said
2beatenup@reddit
And what’s the plan after that? Can it land automatically or do they send someone up there to help the pilot?
iboreddd@reddit
It lands automatically
loose_as_a_moose@reddit
On the 747 if you have smoke or fumes in the cabin the crew will descend below 10k ft, depressurise the cabin. The cabin crew will then open some of the cabin doors slightly to vent the cabin.
A colleague was explaining the procedure, so I don’t recall the exact doors or how many.
Mike__O@reddit
The coolest feature that I have ever seen that I'm not even sure was initially part of the design was on the 707, or if it was figured out later.
The 707 has inboard and outboard spoilers like most airplanes, BUT there's a big difference. You have switches on the overhead panel where you can shut off the spoilers in symmetrical pairs (i.e. shut off the inboards or shut off the outboards).
Due to the sweep of the wing and the position of the spoiler panels on the wing, the inboard spoilers are forward of the center of lift on the wing, and the outboard spoilers are aft. This can change the lift dynamics of the wing.
This becomes useful for a jammed stabilizer. You could shut off one set of spoilers and then use the speed brake handle to trim the airplane. For example, if you needed nose up trim, you would shut off the inboard spoilers and then raise the outboard spoilers via the speed brake handle. As the outboard spoilers came up, they would reduce lift on the part of the wing aft of the center of lift and therefore raise the nose. Same thing in reverse if you need nose down trim.
I've never seen it in other airplanes. Most newer airplanes don't have enough wing sweep to pull this off, and even older airplanes with a more swept wing like the MD11 don't have this feature due to how the speed brakes work on the MD11 (three position notches as opposed to infinite sweep like Boeing).
cx300@reddit
KC-135 Pilot here. We practice this in the sim yearly or so, it’s also labeled on our glare shield This plane was a precursor to the 707!
SukiDobe@reddit
Maybe thats what they’re always doing over KDSM lol
Mike__O@reddit
But NOT a proper 707! I think a lot of people don't realize just how different they are.
As far as the annual EP-- yup. Back when I was flying E-8s, the checkride EP was always going to be either jammed stab, 3 engine rudder boost out, or two engines inop on the same side.
cx300@reddit
With the R model engines it’s not as big an issue, we can fly on one engine up to about 200k gross weight Today’s checkrides usually consist of single outboard engine failure rudder power operative - it’s as easy as pulling the symmetric engine to idle and flying on the other two! Of course we still practice 2 engines failed one side, rudder power inoperative but only when there’s extra time in the sim
Mike__O@reddit
707 is a different animal, and the E-8 is a different animal from that. Even E-model tankers would almost certainly be easier to manage than an E-8 since you could dump down to a LOT lighter weight. BOW on a C-model E-8 was around 180k. Throw in crew and even an emergency-level amount of fuel and you're pushing 200-220k.
Those old JT3D engines allegedly made 18k each when they were new, but who knows how many horses left that barn in the 100k hours some of those clapped out old engines had. They all certainly spooled at different rates and it wasn't uncommon to see some pretty significant throttle spilts at cruise due to different engines producing different amounts of power at a given target thrust setting.
kevman_2008@reddit
The amount of throttle rigs I've done on JSTARS is crazy. Seemed like we had one every other week
Activision19@reddit
What is a throttle rig?
kevman_2008@reddit
Adjusting the throttle system so that the throttle levers and the engines accurately reflect each other.
The JSTARS were all cables and pushrods, so we would drop rig pins into tower control shafts then adjust the cables so the levers were all the way down .
Surprisingly easy, but our tech data mandated that all engine control rigs had to be done in a hanger, which was very limited
WestDuty9038@reddit
2 engine inop both side? Crikey. That must’ve been fun lmao
Mike__O@reddit
So long as you were light enough, it really wasn't much different than one engine inop on a twin. Same principles apply. If you were heavy (like the E-8 that ate geese on takeoff) two engines would just fly you to the scene of the crash, but if you were light the airplane could fly on two.
The big training element was the go-around. Those old JT3Ds took 8 seconds to spool from idle thrust to go-around power (per the manual). That meant when you had two engines inop you would push the throttles to go-around power, and keep the nose down to burn altitude to gain enough speed to start climbing.
WestDuty9038@reddit
Did you mean E-3? Also TIL, thanks for the info + makes sense
Mike__O@reddit
Yes, you caught me before I could hit the edit.
scotty813@reddit
I live in Tampa, and I gotta say, the CFM56 upgrades do make her sexy.
MortonRalph@reddit
They do. Former neighbor was a FO on one of the KC-135s at MacDill, and we were able to get a ride a few years back during a demo flight they did for some brass. My former office was in a 28 story building in downtown TPA that face MacDill, so all I had to do was turn my chair around and I could almost always get some good views of the field operations.
swirler@reddit
L-1011 has this too.
Cool-Acanthaceae8968@reddit
The L-1011 is the reason for this.
Delta 1080 had a stabilizer trim failure.. but because the overly-complex L-1011 had two individually controllable stabilizers.. they were able to nurse it home (a stabilizer failure is usually fatal).
It was after that they came up with the scheme to use spoillers for pitch control. NUKI. Nose Up, Kill Inboards. Your speed brake handle now functions as a yoke.
Iaqton@reddit
So you're saying, they did it all for the NUKI?
AviationNerd_737@reddit
Yes. Nice observation. To an extent, I believe you can do it on a '37 too.
May I ask how you know this?
Mike__O@reddit
Because I've got about 1800 hours in 707s (E-8s) and was an instructor on the airplane.
AviationNerd_737@reddit
Damn! Nice.
We see a lot of the 707 quirks/features on the '37 too. 1960s design after all :)
Traildetour@reddit
I wonder if that could have saved that Alaska flight that was stuck upside down and crashed in the ocean.
Mike__O@reddit
Not sure. My understanding that that the jack screw mechanism broke and the stab was free-floating. The procedure in the 707 was based on a failure of the jack screw in a way that you could no longer adjust the position of the stab, but it was still stuck wherever it was stuck. If the stab was free-floating I don't think the airplane would be controllable, even with the split spoiler trick.
beaded_lion59@reddit
FYI, the old MD-11 wing engines were designed to fail UPWARD and OVER the wing. JFC.
MrFickless@reddit
The 787 batteries are housed in giant metal boxes in case the lithium batteries catch fire or explode.
Kojetono@reddit
Similarly, the 787 APU has the compressor surrounded by a massive steel band that can keep it contained in case it shatters.
This was done because early examples could separate in a way that ejected a titanium disc from the engine. It could then cut everything it came across, potentially causing a lot of damage to control systems.
From what I heard this issue was fixed, but proving it is so expensive that paying Boeing 10k USD overweight fine per APU is the better option.
Internal_Button_4339@reddit
Compressor? Titanium disc?
You're aware the 787 APU is just a big lithium battery? No turbine engine.
Kojetono@reddit
Damn, I guess someone should tell Hamilton Sundstrand that they're in the lithium ion battery business now.
Internal_Button_4339@reddit
TIL they actually have a turbine, too.
flarne@reddit
What kind of cells do they use? I hope LTO?
Major-Ad148@reddit
Knowing Boeing, it’s probably lipo
VulgarButFluent@reddit
Not just a big metal box, which by the way is a BITCH to open and replace the battery, but it also has a pressure indicator to let you know it exploded just in case you missed the geyser of flame coming out the bottom via the Battery Exhaust ports that dump the gasses/fire of lithium ignition overboard.
Weet-Bix54@reddit
Wasn’t this changed after ANA had those fires when they started? Or was that one just really bad?
Gnochi@reddit
Those fires are why DO-311A was written, and the requirements of DO-311A were at the time lightest to meet by putting the battery in a thick metal box.
Frosty-Chard5251@reddit
The metal casings came after multiple batteries on 787s caught fire and they all were grounded and Boeing was forced to make changes to ensure safety.
TweakJK@reddit
When a Super Hornet enters uncontrollable flight, the pilot can flip a switch which changes the mode of the displays to show one thing, a giant freakin arrow that points in the direction they need to throw the stick to give them the best chance of recovering.
IoGibbyoI@reddit
I didn’t know this and it’s quite the unusual tidbit.
TweakJK@reddit
It also does a bunch more stuff.
2.8.2.6 Spin Recovery System. The spin recovery system, when engaged, puts the flight controls in a spin recovery mode (SRM). This mode, unlike CAS, gives the pilot full aileron, rudder and stabilator authority without any control surface interconnects and all rate and acceleration feedbacks are removed. The leading edge flaps are driven to 33° ±1° down and the trailing edge flaps are driven to 0° ±1°.
sledge98@reddit (OP)
That's a good one! Thank you!
Yorkshirerows@reddit
Some aircraft have a disorientation recovery button which puts the aircraft in a stable nose up attitude, seems like cheating compared to the 'giant freakin arrow' though
sintactacle@reddit
CTRL + F
Darko 0/0Wow, no Donnie Darko comments!
canuck2004@reddit
Structural dual load paths! I had no idea until I learned about them. I thought it was neat.
sledge98@reddit (OP)
I will have to Google this.
quietflyr@reddit
You'll get better results searching for fail-safe structural design philosophy. That's what it's actually called.
The idea is that failure of any one structural member shouldn't bring down the whole aircraft. This manifests in a bunch of different ways in the structure, such as rip-stop straps in the fuselage (where, if there's a crack in the fuselage skin, the straps are supposed to stop the crack from ripping into a much bigger fuselage hole. Or, on the old 707 horizontal stabilizer, it had three spar caps. If the top one failed, the load would redistribute to the middle spar cap and the stabilizer would still be able to carry load.
Now, it was eventually determined that this philosophy wasn't quite enough to prevent accidents, so they started with damage tolerance philosophy instead, which is quite different.
G8M8N8@reddit
Airliners dont want to spend time and money re-training pilots for new aircraft, so boeing has been continuously modifying ancient aircraft like the 737 with stranger results. The MAX brought a new engine, which was too big to fit under the wings, so the pushed it in front of the wings, which thew the whole weight distribution off. To stop the planes from falling out of the sky, they modified the flight computer to pitch up automatically in order to mediate the weight problem. They never informed pilots or operators of this design, leading to several planes crashing because the pilots were attempting to fight the computer for control of the elevators.
FarButterscotch4280@reddit
Well ! that was poorly written...
Continental-IO520@reddit
The 727 nose wheel brake is pretty cool. Highly unusual too.
GeologistPositive@reddit
Well some of them are designed so they don't fall off at all
m71nu@reddit
Being Dutch and having been blasted with all the news about El Al Flight 1862 I knew this. It also makes sense. You don't want an unbalanced engine to destruct the whole plane.
sledge98@reddit (OP)
Yea it's something that makes sense when you think about it but often at first people are surprised that an engine disconnecting is "working as intended".
LawManActual@reddit
That’s because most people are ignorant on the topic. They don’t have a reason to have thought about it, no experience in the area.
jas417@reddit
So true. I’m not a professional pilot here, I’m a few hours into an SPL and a big aviation nerd who plays too much flight sim and sponges up anything my friend who does fly 737s says.
All of the coverage on those recent aviation accidents(the big ones, and then the following ones that wouldn’t have hit the front page besides timing like the Caravan in Alaska) was so, so, so cringe…
I mean is there really not a journalist somewhere at CNN that also has a PPL or is at least a flight sim nerd that has half a clue what they’re talking about?
AdoringCHIN@reddit
The plane that went missing for over a day wouldn't have gotten attention? I feel like it probably would've.
jas417@reddit
A little I’m sure. Locally certainly. I don’t think I would’ve seen it as the headline on AP. Airliners are statistically the safest form of transportation, general aviation is closer to riding a motorcycle statistically. Now a lot of that is amateurs not doing preflights or rich guys who bought more than they could handle. Airliners, even the smaller ones like in the DC incident, really don’t go down often. Smaller but turbine powered and professionally flown planes like the that do go down, especially in those conditions. They don’t have the redundancy, second pilot and deuce capability even a CRJ would. A large chain of small mistakes or a few big ones have to happen for an airliner to go down. Caravans bush flying in a storm go down sometimes. It’s sad, and unfortunate but it happens.
Ok_Advisor_908@reddit
For sure, and I can't blame there intuition either. Generally there isn't a part in the world I'd ever assume is designed to detach from a machine.
LawManActual@reddit
That’s funny, I’ve an engineering degree and it’s not a foreign concept at all. They even have a name, sacrificial parts. Shear bolts are but one example of them.
I get it though. A lot of people are surprised that buildings, bridges, and other tall structures are designed to sway. It’s actually less stress on the bodies.
jas417@reddit
Haha sorry to recommend to you on a different one but yeah.
I’m an off roader, and I’ve learned the hard way, so I run weaker axle shafts than my diff gears and transfer case warrant. Why? They’re the fuse. I can bring spares, they cost 1-200 bucks, and I can replace them on the trail.
If I toast a diff or especially my transfer case I’m in big trouble if it happens in the wrong place, and it’s going to cost a lot of money when I get home. Same concept there but for safety, it’s a circuit breaker.
LawManActual@reddit
I’ve off roaded a bit, that’s a great example!
The “can change it on the trail” is the real key. Rather that break and spend an hour and be on the way than throw a rod, break engine case, have to be towed out from the trail by tow strap, then towed and hour home to then tow it to a dealer. (What a day!)
jas417@reddit
Ooooof… water or oil pan?
My buddies and I actually managed to McGuyver a smashed oil pan once and drive it out.. driver noticed and shut down as soon as the pressure light came on and did no lasting damage, of course we had to tow it a bit to a good spot which was now definitely our camp spot. Someone took the time to run out to a town and get some oil, and we actually patched it with a cut up PBR can and a whole lot of JB weld and it actually worked
LawManActual@reddit
That’s legit. Honestly a good day, and great story.
Mine was the side of the block, I still have a price of the block on a keychain. New truck too, under 6K miles. Good news is it was warrantied. The manufacturer even sent an engineer out to inspect it, glad I spent the time to thoroughly wash it before sending it to the dealer.
Got a new engine out of it though.
jas417@reddit
Hey at least it worked out. That must’ve been rough especially in a brand new truck you’re hoping but never positive they’ll warranty.
It really was, if you and your friends can think on your feet and come prepared you can really get yourselves out of some ridiculous situations, like when my truck slid halfway off a cliff when some rock gave and we got it back on and fixed the road with a high lift jack and shovels.
This friend was pretty new to this sort of thing, had an old AWD Astro van that was really mostly for mtn biking and skiing adventures, and we took an overlanding trip in eastern Oregon that was supposed to be very remote but pretty mild roads wise. We screwed up with one of the route choices and thought we’d ruined the hobby for her…. NOPE! She had so much fun and got so much satisfaction out of us all working as a team to fix her seriously damaged van that she went all the way down the rabbit hole and now drives a Wrangler Rubicon on 37s
elmwoodblues@reddit
Think of it like a fuse in your house or car, or the shear pin in your lawnmower or snow blower: a separation of a part (or circuit) to prevent further damage.
Ok_Advisor_908@reddit
Oh I'm well aware how it works, I just was meaning I don't blame those for not intuitively assuming it. Thanks for the info anyways, good analogy for anyone who doesn't :)
greyhoundbuddy@reddit
I did not know of this, and it does make sense reading these posts. But if I'm ever in a wing seat of an airliner in flight and see the engine drop off I will freak out.
LawManActual@reddit
That’s fair. It’s an abnormal event in abnormal events.
While I totally understand it, I still kind of chuckle when I see people freaking out over engine failure or compressor stalls. The aircraft can be on the runway when the engine fails, takeoff, climb, and return just fine. Of all the catastrophic failures, an engine failure is least concerning for me. Especially on the 320.
greyhoundbuddy@reddit
Well yes, unless that first engine failure is followed shortly thereafter by a second engine failure. Statistically highly unlikely I know, but then that first engine failure was also statistically highly unlikely. As a passenger I'd greatly prefer to have both engines working :-)
TheLorem_Wolf@reddit
Wait could you explain what you mean by this statement? Are you saying that the design of detaching the engine whilst it’s failing is a bad design or good design?
sledge98@reddit (OP)
I'm saying that a detaching engine will at first often seem a "bad design" to someone unfamiliar with aviation.
TheLorem_Wolf@reddit
Ahh okay i see what you meant haha! Sorry that statement confused me lol😂.
Albertoplays111@reddit
I’m sorry for this and i mean it. But can you use commas? It’s hard to read.
MerelyMortalModeling@reddit
I thought that crash was caused by the engine not cleaning separating like it was designed to do which caused catastrophic damage.
Frap_Gadz@reddit
Yes the engine detachment was triggered by fatigue in the fuse pins. The fatigue altered the way the engine came away under overload failure. The pylon design was found to be inadequate as were the inspections to ensure structural integrity.
60TP@reddit
The slander potential of this image is insane
sledge98@reddit (OP)
Explain?
Wit_and_Logic@reddit
Jettisoning an engine seems like less a save-the-people measure and more a make-it-someone-elses-problem measure.
MTLMECHIE@reddit
All new commercial airliners have ashtrays to put out small fires. I was in a CAE Airbus A350 simulator which them in the cockpit.
Random_Videos_YT@reddit
This looks like a mentour pilot/now thumbnail. Was it?
sledge98@reddit (OP)
No, i made this picture myself for this post.(cut and paste engine, add some flames)
Likely will be used as a concept for creating my thumbnail when i make this video.
mottledmirror@reddit
All critical engineering parts are designed to fail in a certain way.
Crumple zones on cars for example.
Horror_Place2697@reddit
This image makes me think
Imagine being in some sort of afterlive and getting asked "so, how did you die?"
"Well you see, a JET ENGINE FELL ON MY HEAD."
Which_Material_3100@reddit
The old “let it burn off the pylon” thing I heard during initial multi-engine jet training in the 1980s. This philosophy was part slowing us down during emergencies so we would not shut off the wrong engine. Or fly into a mountain on a complex engine our procedure after a V1 cut.
rkba260@reddit
I say this when it's my leg and I'm briefing engine out procedure, just to let the other guy/gal know it's a time threat and I'm going to be focused on flight path and accelerating, not any immediate action items.
Which_Material_3100@reddit
Perfect. “Wind the watch, smoke a Lucky..”
imaguitarhero24@reddit
People probably know about this one but airframe parachutes are still a pretty wild concept.
Even if you're familiar, Scott Manley did an excellent video recently on the subject, so this is a great time to share it.
sledge98@reddit (OP)
That's actually not a bad idea to include in my video.
KJ_is_a_doomer@reddit
ONA had JATO installed on some of their DC9s. Anecdotal sources maintained that it was either for increased performance or as an emergency thrust option to help the aircraft climb
Dirrey193@reddit
Iirc tires are filled with nitrogen to diminish fire chance in the landing gear and the fuel tanks are flexible, preventing air from coming into contact with the fuel as it is consumed
Appropriate-Gas-1014@reddit
Fuel bladders are flexible, but that's just so they can be installed and removed easier. The majority of large aircraft have rigid tanks, usually in the wings and center wing box.
Some aircraft do have a nitrogen generating system to create an inert atmosphere in the fuel tanks.
SubarcticFarmer@reddit
Nitrogen pressure doesn't vary as much by temperature as regular atmosphere and it doesn't have moisture. I've never heard anything about it being for landing gear fires. It's not like it is pure oxygen otherwise.
ValhallaAir@reddit
Holy shit it’s rocket sledge from rock league
sledge98@reddit (OP)
No, it's Sledge from "That Happened".
Shush ;)
Federal_Cobbler6647@reddit
Saab Draken had its airbrakes in fuselage, 2 upper surface, 2 lower. In case of primary flight control failure they could be activated to replace flight control surfaces and were automatically controlled trough stick.
Sacharon123@reddit
Look into the the direct lift control feature of the tristar and into the elevator jam assist feature of the 737 max. Its worth it. (if you want details, pm me, I should still have a hardback copy of the flgiht engineers manual somewhere).
sledge98@reddit (OP)
Appreciate it. I'll check this out and reach out if i have any questions.
Sacharon123@reddit
Just to make the connection, the elevator jam assist is the "safety" feature, but based on the DLC ;)