737 Max

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Report details how Airbus pilots saved the day when all three flight computers failed on landing • The Register


(full report linked in article)


If I read it correctly, A330 touches down under pilot control with a little bit of rudder command. Switching from flight law to ground law caused all three flight computers to panic leaving the pilot to stamp on the brakes and hope.



Now I am sure reverse thrust failures are well trained in simulators but impressed that the pilot was cool headed enough to take in the inputs and react correctly in under 4 seconds. More proof I could never make it as a pilot.
 
#1,631
I look at that and wonder what the logic was that commanded the spoilers to retract once it was already in ground mode… sure, a cascading failure of the flight computers is a reasonable explanation, but I still don’t like it, as the runway landing distance numbers are predicated on them (the spoilers) deploying at touchdown to give maximum weight on wheels, and therefore max braking ability.

I.E., once on ground they shouldn’t have retracted.
 
#1,632
Report details how Airbus pilots saved the day when all three flight computers failed on landing • The Register
In this instance, the aircraft was shifting from flight to ground law as the pilot was applying the rudder (not particularly unusual, especially if there is crosswind on landing). Since the rudder deflects differently between ground and flight law a conflict occurred and the system was flagged as faulty. Then the same thing cascaded through the second and third FCPCs.
COM (Command) and MON (Monitor) is a standard protocol for Airbus Fly By Wire aircraft, with the monitor watchdog switching to another computer (command) in the event inputs diverge outside of acceptability. As our Airbus pilot put it: "Stick monkey (or autopilot) puts in command and clever Franco-German computer monitors input for correctness."
Click to expand...
😀

George
 
#1,633
6L6 said:
I look at that and wonder what the logic was that commanded the spoilers to retract once it was already in ground mode.
Click to expand...


I'm guessing they never FMEA'd this scenario so the rule that one computer needs to be running to keep the spoilers up over-rode. As anyone whose done even basic software or hardware systems analysis knows happy path is easy, unhappy path is often 90% of the work. And that's for non-life critical stuff.



Airbus are quoting 44m flight hours for the family with this being the only recorded incident so that should be at least 4 million landings if not double that so a rare edge case, albeit a very nasty one.



Does anyone know the approximate stats on pilot landings vs computer landings these days? When I fly I always try and work out whose touching down and generally fail except finnair in the winter when the ex military pilots seem to slam the plane into the snowy runway and one landing in (I think) Atlanta with an evil cross wind where the grin on the Captain's face gave it away 😀
 
#1,634
Depends on the runway too. Hyderabad runway is so long that one gentle reverse thrust is all that is needed, A320 uses only half the runway.
Sometimes the runway is short.
And sometimes they use reverse thrust to keep brakes cool, you can't take off with hot brakes, and the planes have to be turned around fast.


Some pilots go gently, and some slam the planes down...their training, and choice.
 
#1,635
Bill - Many, many less than you think, probably 1 out of 500 or fewer. Autoland is rare, expensive, and can’t be done at all airports.

As for rougher touchdowns/landings in inclement weather, that’s going to be close to 100% - you want to get the tires on the runway and through the water/slush/snow as best you can for maximum braking effectiveness. Crosswinds are another place where you might be correct in expecting a rough touchdown, particularly when they are strong.

Naresh - yes, reverse thrust can be used to shorten the landing distance, but you don’t get to plan on using it for runway distance requirements… (Because what if it doesn’t deploy properly, or asymmetrically, or if the reverses do deploy but the engines dont spool up… etc… , it’s not used in that calculation.). BUT, the advantages of spoilers (which are both aerodynamically draggy and, more importantly, make the wing produce essentially no lift, so all the weight of the aircraft is borne by the landing gear/wheels and therefore the brakes can be at maximum effectiveness) IS included in the landing distance calculations.

This is why it’s so bizarre that the aircraft, with the weight-on-wheels sensor showing it’s on the ground, stowed the spoilers.
 
#1,637
Here they were using reverse thrust to reduce brake use, 737-200.
Boeing withdrew the air frame warranty, saying the use was far beyond expected during design phase.
Airbus got the next order, one crashed because the wrong airport altitude was set.
After that, their performance has been good.
Anyway, not much to do with audio, bit a lot to do with the foibles that make us human.
 
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