Rudderrat & Retired F-4
From the BEA Note:
At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have
no valid indications".
At that moment, the thrust levers were in the IDLE detent and the
engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs. In
the following moments, the angle of attack decreased, the speeds became valid again and the
stall warning sounded again.
This tells me that the crew performed an "experiment" that indicates they could have reduced angle of attack using the elevators.
Even if there was a notch in the wing pitching moment, it is likely that this aircraft could have developed enough nose down momentum to proceed past the notch. Particularly if, as the aircraft began to pitch down, they then began to roll nose down trim in using the manual trim. In effect, as the aircraft began to pitch nose down, they began to match (approximately) the rotation rate of the aircraft nose down with the THS rotation. Success would have been signaled by getting light in their seats and return of rapidly accelerating airspeed at approximately 45 degrees nose down attitude.
If you will think back to Gum's Viper deep stall recovery, the recovery technique was to pitch the aircraft up and then develop sufficient pitch momentum nose down to pass through the sticking spot. In effect (with all that NU THS), AF447 was starting from the stick back position already and just needed to start the ball rolling forward.
I am wondering whether as the aircraft began to rotate nose down, the crew began to get light in the seat as the aircraft began to fall faster. That also could have been a discouraging factor to continued nose down input.
Of course in my F-4, best acceleration occurred at zero g, but the AF447 crew was undoubtedly not accustomed to the concept.