Just was on a flight that lost hydraulics before landing - how dangerous was that?
Posted by GetMammt@reddit | aviation | View on Reddit | 31 comments
Flew from BA to FFM Lufthansa and the pilot did an annoucement that there was a rare issue with rhe hydraulics and that they dont work, crew prepped us for the worst and fire fighters came but in the end all was fine.
Decent-Lecture2608@reddit
I am glad to hear that you are okay because hearing hydraulic issue mid flight would make everyone nervous. The fact they landed safely honestly shows the training and systems worked the way they’re supposed to. My friend who works in private aviation who uses jettly always says pilots are trained to stay calm specifically because passengers feels the crew’s energy,they are really professional.
flightwatcher45@reddit
Did the rat deploy? Unlike all hyd was lost but down to critical systems, not ideal but very doable.
Strenue@reddit
Part 25 reliability!
vfrflying@reddit
You didn’t happen to hit a light pole did you? Just kidding just kidding.
Strenue@reddit
And a tractor trailer.
helikiwi@reddit
Well, you've got to post about it. Can't be that bad.
BigJellyfish1906@reddit
In an airbus, it reverted to one of several backup systems, and you most likely landed with full hydraulic control. The captain only notified you because there were gonna be fire trucks on the runway, and you were probably gonna get towed back to the gate.
whatsitallabouteh@reddit
Not a major issue at all. A single hydraulic failure is not significant. Assuming it was the loss of the fluid (a pump failure would be dealt win by the PTU with zero operational effect). With even a green system failure, it’s not a major issue.
For landing gear extension, this would be done with the manual hand crank and I’ve actually had this occur a number of years ago. Depending on the MSN, a green system failure can result in a loss of nosewheel steering which can mean getting stuck on the runway (as it did on the old 321 I was flying).
Overall, a minor failure with minimal landing distance penalties.
ChazR@reddit
It's not ideal.
Modern aircraft have several independent hydraulic systems with a high degree of redundancy. The hydraulics are required for critical operations including flight controls - ailerons, elevators, speed brakes, and rudder operation. All of those are served by at least two fully independent hydraulic systems.
Hydraulics also operate the brakes on almost all (looking at you, 787) types.
Most probably a single hydraulic system failed, reducing the redundancy to an unacceptable level. If a second system had also failed it could have become somewhat sporty, but I'm not sure that's ever happened without actual enemy action.
They followed the procedure for a hydraulic failure, which is to get on the ground as fast as reasonably possible, and have emergency services standing by in case the brakes underperform.
It's a real emergency that needs to be handled properly, but the aircraft is designed to land safely with some degree of failure in any system.
Engineering will be working overtime.
Uniturner@reddit
Complete loss of hydraulics on all systems has occurred a few times. Most infamously in the Sioux City incident.
Every-Progress-1117@reddit
But in that particular incident, loss of hydraulics was due to a very exceptional event.
Loss of a single hydraulic system in a modern aircraft is a big concern, but systems are designed for redundancy and resilience. Lost off your tail engine to a catastrophic failure which then goes and severs hydraulic, fuel and control lines is quite a different scenario.
mattrussell2319@reddit
Right; the hydraulic lines of all three independent systems were routed through a single area and that’s what was hit by parts from the disintegrating engine. It sounds like designs have changed since then to include things like hydraulic fuse plugs to isolate affected part of the hydraulic systems
gromm93@reddit
The hydraulic fuse plugs didn't actually didn't happen until after the JAL 747 accident. The cause was an explosive decompression of the aft pressure bulkhead, which in turn destroyed the vertical stabiliser.
Again, basically the whole tail was destroyed, which took all the redundant hydraulics with it.
One of the ways I think they have better redundancy now, is to have different hydraulic systems for different control surfaces, and to have them physically separated enough so that damage in one area of the aircraft doesn't destroy all controlability of the aircraft.
BoringBob84@reddit
They have. 14 CFR 25.1309 says:
These regulations are difficult to meet and they require extensive analysis to demonstrate compliance. To prevent a single failure from taking out a system that is critical to flight, redundancy, independence, and physical separation are usually necessary. A modern aircraft with redundant hydraulic systems that were routed through the same rotor burst zone would be uncertifiable.
planescarsandtrucks@reddit
In addition to the single failure piece, 25.1309(b)(1)(i) is ver my important. The FAA defines extremely improbably as less than one in 1,000,000,000 flight hours (literally 1 in a Billion).
All failures must be assigned a probability based on testing, industry experience, or other approved data. Then all combinations of failures must be analyzed to determine if the combinations lead to a catastrophic condition, and if they do, then the probability of that combination must be less than the 1 in a Billion.
This takes hundreds or thousands of pages of analysis for every system on the aircraft to ensure that these combinations meet the regulation.
BoringBob84@reddit
I agree - Fault Tree Analysis per SAE ARP 4761.
Less stringent probabilities apply for hazards with less severe consequences and for light aircraft (14 CFR 23.1309) and rotorcraft (14 CFR 27.1309).
Uniturner@reddit
Sure, it was exceptional. JAL 123 is another example of an extraordinarily unusual scenario. It’s always the ‘different scenarios’ that get us though.
Ataneruo@reddit
Right, but the redundant systems reduce the number of exceptional scenarios that occur. No redundant hydraulic system will survive the in-flight breakup of an aircraft for instance, but a catastrophic failure of something that only affects one of the hydraulic systems is no longer an exceptional event if the redundant systems continue to work.
Senior-Cantaloupe-69@reddit
They’ve changed regulations over that. Aircraft certified since then have to make sure wiring and hydraulics are separated enough to prevent multi system failure. Coming from personal flight test avionics experience re-wiring the e-bay
surSEXECEN@reddit
That’s because an engine blew up and severed the triple-redundant hydraulic system. Infinitesimally unlikely to occur!
SlurmLoco@reddit
A DHL flight out of Baghdad during the Iraq war lost all hydraulics due to a surface to air missile strike. They were able to land using only differential engine thrust. No injuries and the plane was repaired and returned to service
highdiver_2000@reddit
oh wow.
https://en.wikipedia.org/wiki/2003_Baghdad_DHL_attempted_shootdown_incident
BoringBob84@reddit
This is why modern aircraft are required to have physical separation of critical systems (including hydraulics), so that no single failure or threat (e.g., rotor burst, tire blowout, bird strike, etc.) can take out redundant systems.
phil_ch@reddit
Just a relevant fun fact; The A220 also has fully electric brakes.
sir_thatguy@reddit
Assuming A320, if a pump had failed there’s a Power Transfer Unit that uses the good hydraulic system to power a hydraulic motor paired to a hydraulic pump in the bad system. (It’s the thing heard barking when shutting down at the gate.) This will provide some hydraulic power to the failed system.
If it’s a loss of fluid problem, then that circuit is just out of commission. But because of redundancy, most things will still be operational to some degree because of the other, independent, hydraulic system.
ForeverNo9437@reddit
Just adding more info, in somes cases the PTU (power transfer unit) must be turned off because it works too much (leak for example I think), which can make the PTU unusable.
MrFickless@reddit
Not really that dangerous, but increases the urgency to land. There are multiple, independent, hydraulic systems on every aircraft.
It's the equivalent of having a puncture on one of your front tires. You can keep going, but you'll probably want to find a mechanic to get that fixed before you lose the other and lose the ability to steer on the road.
airport-codes@reddit
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Difficult_Camel_1119@reddit
bad bot (or bad OP) FRA not FFM
Apprehensive_Cost937@reddit
Not an issue, as there are usually 2 or 3 hydraulic systems on board airliners, which provide redundancy.
If you lose one of them, your landing distance might increase slightly, or you might need to land at a higher speed (which is when we'd get the firefighters to inspect the brakes before taxi), or you perhaps can't turn the nosewheel anymore, and would need to get towed to the gate.
If you lose two systems, then it's a lot more serious, and you'd want to land pretty quickly, ideally on a nice long runway, and flight control systems might be degraded (but still safe), requiring us to establish in landing configuration much earlier than usual for example.
It goed without saying that pilots are trained for all of this, and we get regular simulator training and checks every 6 months, on top of all the other (theoretical) recurrent training, where we refresh knowledge about aircraft systems, abnormal procedures, human factors, etc.
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