Lyman
Franzl:
Do you have advice on the abnormal responses (unusual) in this regard? It is why I brought up the possibility that PNF may have been referring to bug speeds lost? Eg. "we've lost the speeds"
No, i donīt. I couldnīt find any suitable explanation in the available documents. But but iīm interested as well, maybe somebody can explain?
Turbine D
Lots of talk about stalls:
The BEA analysis is quite spot on.
2.1.3.2 Exit from the flight envelope
The STALL 2 warning triggered at 2 h 10 min 51 but did not elicit any response from the crew. Even though the stall warning had been sounding for 9 seconds, the aeroplane climbed above the propulsion ceiling with the vertical speed still high, and with a flight path speed that was dropping as a result of this vertical speed. At this point, only descent of the aeroplane through a nose-down input on the sidestick would have made it possible to bring the aeroplane back within the flight envelope.
The rapid reduction in speed was accompanied by an increase in the angle of attack. The lift ceiling, at the Mach at which the aeroplane was flying at that time, was broken a few seconds after breaking through the propulsion ceiling. Due to its momentum, the aeroplane continued to climb: the aeroplanes kinetic energy was converted into potential energy until the point was reached when the aeroplane unavoidably started to descend. The PF was still applying nose-up inputs and the angle of attack continued to increase. Even with the engines at the TOGA thrust setting, the drag generated by this high angle of attack was so high as to prevent the aeroplane from accelerating.
Subsequently, the position of the sidestick, maintained in its nose-up or neutral position, continued to exacerbate the situation and made the recovery uncertain, even impossible.
The following part still gets my special attention (bolding by me)
2.1.3.5 End of the flight
At about 2 h 12, descending though FL 315, the aeroplanes angle of attack was established around an average value of about 40 degrees. Only an extremely purposeful crew with a good comprehension of the situation could have carried out a manoeuvre that would have made it possible to perhaps recover control of the aeroplane. In fact, the crew had almost completely lost control of the situation.
Up until the end of the flight, no valid angle of attack value was less than 35°.
For BEA the case was lost there not for this special AF447 crew, but for any average crew. And any average crew would not maintain full NU SS as the crew of AF447 did.
There is reason behind that statement, also it is not specified by BEA what this reason is. Reading through the posts of 9 threads shows, that most of the dedicated and expierienced posters (pilots, engineers...) have simple solutions for recovery, some reference their expierience in the sim as proof for simple managable recovery techniques, engineers come up with their math-model of flying.
Who are we going to trust on this matter, BEA or the other opinions?
Just for clarification, AF447 never should have encountered this situation firsthand, as correct recognition of the failures and the subsequent aplication of the procedures would have prevented the exit of the flightenvelope. Even in the first phase of the exit of the flight envelope recognition of the impending stall and the aplication of the correct procedure would have saved the day.
Why does BEA state, that after descending through FL 315
"Only an extremely purposeful crew with a good comprehension of the situation could have carried out a manoeuvre that would have made it possible to perhaps recover control of the aeroplane."