Originally Posted by Hyperveloce
Ok, the gentle ND introduced by the low speed prot. can be overriden by the PF (and maybe the PF persistant NU inputs were to counteract the low speed prot. ND orders, but he did so much more than that).
See my post above. Low speed Stability, VSw, (and associated speed stall warnings) would only be available with two ADRs being declared valid, which might not have been possible before 0211:40+. Moreover, if it has been available before or after this point, it would have triggered "DIRECT LAW", whatever imputs made by the PF in order to counter those active ND protection imputs. Quite frankly, there is no trace of "Direct Law" and this never happened.
Originally Posted by Hyperveloce
But if we consider the past UAS incidents analyzed by the BEA, do we see a single occurrence of a low/high speed prot. activation when the ALT2 was triggered by a NAV disagreement ? In a few past cases, a descent (never more than 5000 ft) was decided when the stall warnings sounded but it was a PF action. Can we assume that these low and high prot. were not available in all these UAS incidents and in the AF 447 case ?
No (first question). Yes (second one). All events involved 2 or 3 ADRs faults, this ruling out "Low Speed Protection" (other have been transient, hence, the system would revert to NORMAL LAW and this protection doesn't apply). Moreover, not a single aircraft ever made a single excursion out of its flight envelope.