Originally Posted by Mr Optimistic
What does 'twice in a row' mean - why not continuously ? Doesn't the warning continue until the a/c is unstalled
Stall warning means that the AoA has exceeded a threshold that is several degrees below the AoA at which the airplane stalls. Stall warning continues until the AoA is below that threshold value. IMHO 'twice in a row' means that AoA was just below that threshold, and small 'bumps in the road' caused brief exceedances.
Originally Posted by RetiredF4
2:10:05 - 2:10:20
(...) AOA being 4° at the beginning, raised quickly to above 10, triggering the stall warning (yes, i think that was a valid stall warning). (...)Only 15 sec passed, we are now at FL375 and Pitch is 10° AOA not known but somewhere around 10?
The AoA in level flight at FL350/M.81/275kCAS is 2.55 degrees. 4 degrees is the stall warning threshold at M.81 and would produce about 1.42 g normal acceleration. I don’t think “gee” exceeded approx. 1.4 because it then becomes rather difficult to match several constraints imposed by the FDR data released in the BEA Update. At 10 degrees AoA, M.81 the airplane would be fully stalled, but that didn’t occur here but much later. According to the BEA, “pitch attitude increased progressively beyond 10 degrees” between 2:10:05 and 2:10:50. Therefore I think that the ‘mean’ AoA got close to but did not exceed the S/W threshold at this stage, i.e. the triggering of S/W “twice in a row” was probably due to ‘light chop’ causing some AoA fluctuations between 2:10:15 and 2:10:25.