Hi Neptunus Rex,
post #791
I'm sharing all your comments, only one tid bit should be added.
Originally Posted by Neptunus Rex
Most A330 flights take place in Normal Law, where α Floor will prevent the stall. α Floor is only available in Normal Law, and is triggered when full back stick causes the pitch angle to reach α Prot.
α Floor is only available in Normal Law, but it is inhibited above Mach 0.53. Below this speed, high AOA protection would reduce pitch while applying α Floor. It is obvious that high AOA protected mode is aimed at low altitude, high pitch and low speed situations which are, by very far, what is frequently needed.
At first sight, stalling at cruise level seems so unlikely, in protected mode or not, that most of the documentation/procedure is not even talking about the case.
At cruise, if one hear the stall warnings, this FCOM sentence
"release back pressure on the sidestick" is also inherently implying that the PF is pulling gee's during manoeuver, hence triggering SW, not that he is flying level at the onset for buffet.
If one look at the UAS/Turbulence penetration procedure tables, in clean configuration, safe pitch/thrust settings (=> Mach 0.80):
@ FL370, over 190 t:
- Pitch: 3°
- N1: 94.3%
Hence, at FL375, TOGA would not make that much difference as the aircraft would be very close to its maximum cielling anyway. Also, applying a 5° pitch "above FL100" is in reality aimed for above FL100 and below FL250. It is 3.5° from FL250 to FL370 (90% N1) and 3° above FL370. Also, those settings should be memory items for turbulence penetration speeds.
TOGA + pull up is the Windshear normal procedure. In no way it is related to STALL or UAS procedures at cruise altitude.
Also, while the situation was deteriorating seriously, from 0210:51, the aircraft took another 10 seconds to enter this full stall with all Alarms soundings. Even so, the PF still had its Flight Path Vector (FPV) working. In fact, it was flagged much later when alpha/speeds became again invalid when the stall was much more advanced.
This is another puzzling fact as the FPV (which seems to have been selected) would provide a visual increasing Alpha for the pilots. Moreover, during this early stall sequence, it is also probable that the Flight Directors came back on PFDs and that all speeds/baro altitude were valid and coherent again (but without any characteristic speeds -VLS, VSw, VMax- displayed).
Consequently, my opinion is that the PF should have distrusted all its instruments as everything seems to be working fine in the cockpit displays at this crucial point... but also, during the following 30-40 seconds, in addition to this Stall Alarm which never stopped its warnings.