Hi Machinbird,
Originally Posted by Machinbird
Originally Posted by takata
Any pilot flying an aircraft with autotrim should know that his trim will follow his stick imputs, shouldn't he?
- Yes, assuming he knows he made the stick inputs.
- You seem to be assuming that the initial pitch up to FL375 was deliberate.
- They needed to know it was moving so that they could monitor it.
- Yes, I think that they didn't want all that nose up initially. Later, after the stall, who knows?
Well, I would say that what the PF really wanted during his initial imput is quite irrelevant concerning the "THS issue". You should read again the BEA note as you seem to be the one assuming that the THS was trimmed during the initial climb to FL375 (please, don't trust everything Bearfoil is posting!). You'll discover that everything started a while later: this THS was trimmed from 3NU to 13NU between
0210:51 and 0211:50, therefore, until this point, everything seems about right about its behavior:
"0210:51, the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs. [...] Around fifteen seconds later, [...] The PF continued to make nose-up inputs."
What would make you believe then that the PF maintained (at this stage) all those nose-up imputs without knowing it?
Originally Posted by Machinbird
Once in the stall, it was imperative that stall recognition occur, but it seems, it didn't. Without AOA indicatiors, without stall warning, without comprehending that the decreasing altitude was real, there was one final item that could have explained the situation and that was the THS trim position.
In fact, stall warnings seems to have sounded correctly at this point (see above) while the PF was trimming his THS near its max by applying sustained NU orders! Hence, this THS was fully trimmed during the stall sequence, not before it!
Without puting the sequence in the correct order, this will be fairly useless to discuss its usefulness as to alert you that you are going to stall, when you are fully stalled, but still trimming it the other way!
Beside, I also believe that there is a great deal of chance that the initial PF nose-up order, and following climb, was not voluntary but rather the result of an overcontrol of the roll tendency. Nonetheless, this is absolutely not the issue discussed about this THS setting. When THS goes there, it is quite hard to believe that the PF wanted something else than those sustained nose-up orders... Consequently, what more could he have learned from his THS setting that he already didn't knew while pulling up?
Your concern about it is only understandable with hindsight. Should they have tried to recover from a stall, at some point, this certainly would not help... but then, he put it here at the first place when it was certainly not the right thing to do at all...
My point stop here on this subject.