RetiredF4,
Thanks for your interesting
post, and for drawing my attention to the recent contributions of mm43, A337ab, and PJ2. Must admit that, since reading completely the deluge of about 50 pages of posts in the first four days – much of it rubbish – I've only been reading bits here and there until I happened to spot a significant typo in Smilin_Ed's pertinent post yesterday. (My own
response to the BEA Update on May27/2011z had provoked no PPRuNe feedback.)
You make a strong case for the possibility that the deep stall from about FL350 in the descent (AoA +40) might have been
sans-issue (even disregarding the height required for any recovery).
gums and others have talked about the pitching-moment problem on the previous thread, and I guess that's the essence of your proposal. Like a THS movement in the nose-down sense, down elevator would itself increase the already positive AoA of the THS, whose aerofoil was producing lift in the opposite direction to that for which it was designed. Can we assume that an increase in its AoA from +40 would decrease the vertical component of its lift? Probably.
On the other hand, at the FL380 apogee (pitch and wing-AoA +16), the THS AoA would have been "only" +3 (already producing lift in the wrong direction). At that stage, therefore, there was still a possibility of pitching the nose down with forward stick. My expectation that, with full forward stick, "the AoA would have started to reduce immediately" seems to be justified up to that point
– and perhaps a few seconds longer.
An irony of the BEA Update is the way they are confident enough to state AoA data for moments in time when the FBW system had
probably ruled the data invalid on the basis of (false) low-airspeed indications.
One possible explanation for the PF's apparent reluctance to try and pitch down before the deep stall is, as I suggested on May27, that his (unrecorded) ASI might have been over-reading. Later, about 20 seconds after passing the cruise altitude (FL350) in the descent, he said
"I don't have any more indications."
At that stage in the descent, with wing AoA not quoted, but probably over +40, the BEA reports that
"the PF made pitch-down inputs. In the following moments, the AoA decreased..." Was that merely coincidence?