Clandestino,
I've read your recent posts with interest. I appreciate your sharing your experience and opinions.
Regarding the Stall, Stall Warning and THS, here are a number of clarifications:
As the operational recovery procedure from a Stall has been already revisited post AF 447 accident, there is a growing sentiment that it is time, for a closer look based on AF 447 data, and prior data as well, also to the automation being involved prior and during Stall, involving such elements as THS - the AF 447 case is bringing additional elements to those existing from previous incidents, documented by BEA reports.
BEA reports of incidents involving Airbus Stalls show that often the Stall Warning was active in parallel with the Autotrim moving the THS in max NU position, so the AF 447 case is not unique.
In some of the few Stalls that were followed by successful recovery, the BEA reports show that pilots struggled aggressively and valiantly with the combination Autotrimmed THS at max NU + Elevators max ND, which was a considerable obstacle to defeat.
On reflecting, it seems that in a Stall, a THS max NU, if anything, is only diminishing or delaying the effect of the Elevators ND, at a time, when the effectiveness of the Elevator ND is crucial and has stringent time constraints.
A successful Stall recovery involves a transition from Stall/NU, to ND with Elevators ND to regain speed, with loss of altitude, followed by Elevators NU, to level, and than regain altitude. It seems that in such conditions, having the THS stable in an Optimal Position from a Stall Recovery perspective - the Neutral position - which makes Elevator NU, or ND more deterministic, is a much better choice than having it move slowly from one position to another, under automation control, at times when the effects of Elevator ND, and/or NU have to be maximum and immediate, and are under very stringent time interval constraints.
It is more and more clear (to me) that the THS has a slow, longer time range stabilization function, which does not fit well with the short duration and requirements of quick transitions from NU/Stall, to ND and than NU during the Stall recovery, therefore, it is much better to have it neutral during these transitions.
Lastly, the suggestion that seems to have circulated during the past several pages regarding the THS at Stall is that it should be brought automatically to the Optimal Position for Stall recovery - Neutral Position - as opposed to being stopped in its current position, whatever that may be - which seems to be your understanding of the suggestion.
Originally Posted by
Clandestino
That question should be and will be forwarded to human factors experts.
If you'd like to suggest that stall warning should automatically stop the trim dead, it's a bad idea. If THS helped one get near or into the stall, last thing he needs is frozen trim - it must help one out of the edge of envelope too.