Originally posted by Evan
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Look, they do hand-flown take-offs and landings day after day. They know, and have a practiced motor-skill, that pulling back on the stick makes the plane pitch up.
I can understand lack of training in what relates to not realizing about the UAS situation, or about not knowing the UAS procedure, or at being inefficient and imprecise while trying to hold a target attitude (lack of practice hand-flying at high altitude).
I CANNOT understand lack of training in what relates to make bold, sustained and frequent pull-up inputs that put a plane cruising in what they knew was already the limit of the envelope in a sustained violent climb that reached 12° nose-up and 7000 fpm climb, and keep it in that attitude for several seconds, and when the stall warning triggers (before an actual stall) they pull up hard actively stalling the plane, and kept pulling up with the stall warning shouting in clear English STALL STALL STAL uninterruptedly for 54 seconds.
Sorry, I will NEVER understand how lack of UAS training, high altitude upset recovery, and high altitude manual flight, relates to the above. The pilot inputs would have stalled a non-UAS, non-fly-by-wire DC-8 flying at low altitude, or a Cessna 152 for the matter.
I am NOT saying that the appropiate training would have not prevented the accident. On the contrary, it would have likely done that. Just that the lack of training ALONE doesn't explain the extreme, large, sustained, repeated, irrational inputs.
All of the above said, I do see how Airbus made things more complicated (and I know that, in many cases, a Boeing plane would have made no difference).
- The computer knew it had disconnected the AP and AT due to an unreliable airspeed, but didn't tell the pilots so.
- The flight directors might have presented confusing info, but apparently did not command the level of pull-up made by the pilots, just a slight climb. Since it is required that the pilots switch the FD off whenever the AP disengages for itself, the computer actively disengaging the AP could have killed the FD too.
- The sidestick lacks force feedback. In Boeing FBW planes the yoke has force feedback.
- The plane even in alternate law lacks longitudinal stability. In fact, even more in alternate law. In normal law at least the AoA protection acts like a longitudinal stability at high AoA. And in direct law at least the stick inputs are proportional to the elevator deflection, so the plane will have longitudinal speed and AoA stability. Boeing FBW planes have positive longitudinal speed and AoA stability in all flight control laws.
- There is a lack of throttle feedback too: the position of the throttles doesn't change when the thrust change in auto-thrust, and also when the autothrust self-disengages. The throttles were left at climb with the actual thrust being quite less than that.
- The sidesticks don't move together and the sidestick in use is hard to see for the pilot not-flying. Boeing planes have twin connected yokes that are big, bold, placed just in-front of the pilot and move together. it is likely that the non-flying pilot, and later the captain, didn't knew that the flying pilot was mostly pulling up until he said, 5 seconds before the crash "But I've been pulling up the whole time!" In a Boeing, it would be hard for the non-flying pilot to miss the yoke against his stomach.
- The stall warning, after sounding continuously for 54 seconds, started to behave stupidly. The captain must have noticed the high deck-angle as he "climbed" the aisle toward the cockpit, must have felt the stall buffet, and BEA said that he had to hear the stall warning just before entering the cockpit, time at which the stall warning stopped. The reason why it stopped is because at very slow speeds the AoA values are rendered invalid, and the reason for those very low speed readings was NOT the UAS (it had been already reverted by then), but that the very high AoA (of some 40°) left the pitot tubes severely misaligned with the air stream, rendering them ineffective. At one point the NFP took control and lowered the nose. By doing that he reduced the AoA, which diminished the large misalignment of the pitot tubes that started to show a faster airspeed, rendering the AoA values valid (and of course still too large) which triggered the stall warning. Then there were new pull-up inputs, the speed showed too low again, and the AoA became invalid again, and the stall warning stopped. So the illusion was that pushing down triggered the stall warning and pulling up stopped it. Let's be clear on this: This was AFTER some 40 seconds of irrational pulling up which ultimately triggered the stall warning to begin with, PLUS 54 seconds of continuous stall warning that were addressed with more pull-up inputs. I don't have any faith that, had the stall warning kept working properly, they would have solved the problem that they created and failed to solve for about one minute and a half. But at minimum it didn't help, especially not to the captain that got into the cockpit just as the stall warning stopped. Despite of that, the stall warning triggered (and stopped) dozens of times later during the fall. So the captain must have known that AoA was an issue, but perhaps the intermittent nature of the warning made him think that they were just at a marginal AoA case, which of course was inconsistent with the nose of the airplane pointing high up with the plane falling like a rock, which is like shouting DEEP STALL ASSHOLE!
So, while the pilot inputs would have stalled any plane at any altitude and any phase of flight, maybe, just maybe, this accident would not have happened in a Boeing because of the AoA stability, force feedback, and the NFP noting early in the sequence the stupid nose-up inputs.
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