Originally Posted by gonebutnot forgotten #85
I find (1) unconvincing because it was one hell of an input, sufficient to cause a 7000 fpm climb and, apparently, two stall warnings, sounds sort of deliberate to me.
Was it 'one hell of an input'? 7000 fpm is achieved after 18 seconds of 0.2 g; 12 seconds of 0.3 g, or 9 seconds of 0.4 g.
the BEA has already told us that with no vaild M, the stall warning system uses a value near zero...)
BEA Interim Report #2:
In alternate or direct law, the angle-of-attack protections are no longer available but a stall warning is triggered when the greatest of the valid angle-of-attack values exceeds a certain threshold. In clean configuration, this threshold depends, in particular, on the Mach value in such a way that it decreases when the Mach increases. It is the highest of the valid Mach values that is used to determine the threshold. If none of the three Mach values is valid, a Mach value close to zero is used. For example, it is of the order of 10° at Mach 0.3 and of 4° at Mach 0.8.
This explanation is either in error, or we are misinterpreting it (The BEA Update adds a new meaning to 'invalid airspeed'). In the case of the UAS incident documented in the Air Caraibes Memo, stall warning occurred at 4.2 degrees, with ADR DISAGREE. In the case of AF447, the stall warning must have been at a similar value, because the low-speed value of 10 degrees is well beyond stall AoA.