Ian_W
I think that this may miss the point.
If (as suggested earlier) the THS had remained at NEUTRAL rather than chasing the NU input during a stall, would the PF NU inputs have been enough with elevator alone to maintain nose up into a deep stall? Was it only the added authority of the THS that allowed the aircraft to be kept in the stall?
Perhaps with elevators alone and a THS neutral the aircraft would have dropped its nose, then (had PF kept NU) after getting flying speed its nose would come back up. Perhaps PF was expecting this nose drop 'nodding' behavior? Its what would happen in a lot of gliders and light aircraft and he was glider qualified. The lack of this nose drop possibly convinced PF that the aircraft could not be in a stall.
Was there any training or flight envelope information available to A330 crews that told of the possibility of deep stall? There seems to have been quite a lot on 'spurious' stall warnings.
So without any knowledge of deep stall, with THS having sufficient authority to hold the aircraft in a stable deep stall so no nodding ND, and previous information about spurious stall warnings: everything seems to be set up for a confused PF
Transcription de la conférence de presse du 29 juillet 2011
Some answers from Troadec (BEA director)
Question: there are a lot of airplanes which, when they stall, pitch nose-down including when they have stalled and their last command was to pitch up. This is apparently a phenomenon that many glider or flying school pilots are familiar with. Yet, here we can see that this phenomenon did not occur, that the airplane fell straight while remaining nose-up. Is this a stall mode that is normal or expected?
Jean-Paul Troadec: what was said, is that the airplane stalled from the pilot’s nose-up input. So, mostly the pilot’s inputs were to pitch nose-up, which maintained the stall.
Question: is the way the airplane stalled, that is to say straight while remaining nose-up and not nose-down, is it normal or typical or expected. Let’s say that a lot of airplanes pitch nose-down when they stall.
Jean-Paul Troadec: it’s a point where… Well, I cannot answer your question and say if it is normal or not. It is the situation of this airplane which is perfectly in accordance with the regulations and which was certified.