AF447

[Hyperveloce]

Hi there. Thank you D77, PJ2, all, for these reasonning.
-The Air Caraïbe report states that the stall warnings are triggered as soon as the AoA exceeds 4.2° (can't we find the tables for these AoA thresholds as a function of the aerodynamical configuration & the Mach ?), so indeed, a downdraft of ~10 kts would be sufficient to biase the AoA so as to induce a stall alarm ?
-In most of the known recent cases (about Pitot icing & corrupted airspeeds), stall warnings were sounded, in one occurence it was an overspeed warning. The freezing event durations seem to lie between 1mn and 4-5mn (3mn average).
-It appears that some pilots (were about to) react(ed) to the stall alarms
-The simulation trainings only implement true stall/overspeed alarms justified by conditions in most cases known and prepared beforehand.
-Facing a decision about a stall warning, wouldn't a pilot consider both the cost of disreguarding a justified stall warning and the cost of taking in account an undue stall warning ? (depends on where the PF thinks his plane is within the flight envelope)
-Which are the signals a pilot should consider to make his decision about stall warnings ? (ADR disagree context)
D77 suggests that the Air Caraïbe crew may have had a better, real time awareness of their airspeeds/thrust (A/THR manually OFF) than the AF 447 crew when they faced the stall warnings.
A cross-checking in the BUSS fashion (pich/altitude time evolution for a given pich,thrust)
A cross(checking in the OCTAVE fashion: airspeeds directly compared to GPS ground speed corrected by the OCTAVE
wind database (time required for that ? accuracy versus the aero margins ?)
.../...
on the contrary what would be the false friends to avoid when you have to decide about stall alarms ?
the speed trends if they are maintained/still displayed on the PFDs !
the part of the unreliable airspeeds procedure that tells to take stall alarms in account (and to disreguard the
ECAM warning "risks of undue stall warnings")
.../...
If it appears that the AF 447 may have lost control in high altitude cruise because it reacted badly to a stall alarm, it should be possible to assess the amount of time required to increase the airspeed from Mach 0.80 (~cruise speed) to Mach 0.85 (reaching MMO) then to Mach 90 (severe overspeed) under a few hypothesis ( thrust ; descent angle )
couples ?
Does anone understand why one of the planes which went through a Pitot freezing event (with the deluge of similar ECAM messages) found itself in TO/GA LK ? (the A/THR was manually disengaged before)
Jeff
PS) stall/ overspeed warnings are not transmitted by the ACARS