Originally Posted by GreatBear
By way of revisiting some of the discussion on the earlier thread, is it then possible that the aircraft was upset by really bad (severe turbulence being an inadequate description) up- down- shear forces at 02:10, stalled (easy in the coffin corner), and entered a developed and unrecoverable flat spin. In such a spin, would there not be greater than 30 kt disagreement between port and starbord pitots as the a/c rotated about its CG? Sufficient difference to trigger the PROBE-PITOT ACARS message?
GreatBear;
Pitots are relatively insensitive to variations in the local airflow angle. Significant differences due to angle of sideslip are likely to occur earlier in static pressure and AoA.
EDIT:: Re: "easy in the coffin corner": I've added a few datapoints to the
'coffin corner' graph posted earlier. According to information kindly provided by
PJ2, it takes about 4 minutes with T/L at IDLE to decelerate from M.8 to M.6, which is V_alphaMax (Vs1g). It seems that V_alphaMax at FL350 is defined by buffet onset, which probably implies that the airplane can decelerate even lower into increasingly severe buffet before it stalls.
EDIT2:: The graph showed the Mach corresponding to the stall warning AoA of 4.2 degrees at 1g. Since this is the SW threshold at M=.8, it is appropriate to show it as loadfactor at M.8. The graph has been changed accordingly.
regards,
HN39