American Airlines Flight 742 "flight control system" problems

[Ashling]

Confiture

With respect your reaction to the stick shaker/stallwarning/buffet, in this case, would be very different at 3000 from 150.

At 3000 you would apply the aircrafts stall recovery procedure. I believe Boeing state that you treat the approach to the stall as an actual stall so you smoothly apply nose down elevator (trimming if needed) to remove the warning. With no engines you'd need to keep the nose down longer and further to accelerate but you'd have enough room to put yourself in a much healthier situation. If your in an Airbus, as Sully was, its enough altitude to get out of Alpha Prot and improve your energy state significantly.

That is very different to just releasing the back pressure,

At 150 engines out your in huge trouble as you can't nose down so releasing the back pressure is about all you can do. I doubt it would be enough to remove the warning, or if it did the warning might soon return as the nose may still be high enough to keep your speed were it is or still decreasing just at a slower rate (remember you are @ Flap 15 so leading edges are fully deployed so lots of drag) so your alpha might not reduce enough to exit the warning which you might re-enter prior to your flare. You may also increase your rate of descent. Its also rather dependant on were you've trimmed to as well. If you've trimmed into your speed decrease releasing the back pressure will do little but if you've not trimmed you might find that your nose pitchs further forward than you intended which may be undesirable at 150' and of course cause you to pull straight back into the warning. Of course all this under huge pressure with no training in how to do it or in handling the aircraft, on a regular basis, in that regime. Good luck. I'll take the Bus for this one thankyou.

Its also important to appreciate that the aircraft has v little excess energy at F speed -19. A flare in that state is a very different thing to one at Vapp +5. In effect you are 24 kts slower than normal. This wouldn't be a flare in the normal sense or anywhere remotely close to it. It might reduce the rate of descent a touch but as you only have 3.5 degrees to play with (taking into account the error in AoA allowed for by the gap between max and stall)
the downside if you stuff it up and stall is catastrophic and you have absolutely no practise in doing this. If your rate of descent is survivable its not worth it.