Wie gehts studi...
I think I have not referred once to Boeing. I discuss THS and Autotrim because of its importance in this accident, whilst you seek to frame Bus as Victim of nasty Bus haters....
Autotrim is remarkable in 447 case for its anomalous behaviour in the tragic flight path that doomed this flight.
1. At 2:10:05, it was set to three degrees (-) NU. Throughout the climb and until STALL Warn 2, there it remained, until 2:10:48. You say, along with thermostat's elegant description of its function, that it seeks always to fair the elevators into its AoI, reducing stress on controls.
2. At 2:10:48, it started to move smoothly ( see graph IR #3), until it hit Maximum NU. IT REMAINED at MAX for the duration...
3. There has been a weak but continuous clamor that the THS' behaviour was due "insufficient deflection" by the pilot, and/or short duration of input via SS.
4. Which is it? Is it insufficient controls NU by the pilot? Or is it "Pilot pulls like madman" on SS, and the THS behaviour is unexplained?
5. Some explanations for this dormancy of the HS:
a. Overspeed protection, THS inhibited.
b. Load factor exceeded for Autotrim, (spike of +1.65G in climb)
c. Direct Law
d. A mystery, and none of my business....
Aufwiedersehn, Lyman
EDIT.... It is not incorrect to state that for purposes of discussion, one may say that there was no Autotrim whatsoever post autopilot loss, 2:10:05.
It was fixed for 43 seconds as this aircraft climbed to STALL....it then cycled smoothly to its functional limit, and remained there until impact, at 2:14:28.
I know you are a big fan of Autotrim, so....where was it?
I have belabored this anomalous failure as to the effect it must have had on the pilots. In phase 1, the CLIMB, the was no trimming. In PHASE 2, it was maxed full NU.
PF BONIN has to master the controls in two regimes, the climb, elevators only, and the fall, FULL NU THS plus elevators. In upset, and then LOC, he has TWO PITCH authorities to acclimate to.
No problem, any monkey can do that? Just as the a/c is about to Stall, the Slab
Actions to provide trim FULL NU. The a/c remains NU, dissipates some very valuable energy, and drops in free fall (still NU). You could do that in your dreams?
A casual observer could make the claim that the STALL was forestalled, then caused, by the THS.
Last edited by Lyman; 13th Aug 2012 at 14:57.