Good. This fleshes out those that know from those with no idea.
The aircraft was in normal pitch and roll laws (pg34).
In normal law, when approaching the stall correct function is for the auto trim to stop when Vls is reached such that the pilot has to continue to hold the stick back to induce the protections.
The flight check called for the crew to confirm autotrims stops at Vls (pg49)
Vls at 53.7T is 123kts.
The aircraft reached 123kts at 15.44.35. (pg34)
No alerts, no warnings, (pg37) no crew action (pg34)
Autotrim doesn't stop, but continues to trim back for a further 20sec.
Alpha floor as calculated by the FAC's does not activate at Vprot, possibly because it has calculated artificially low, incorrect data based on false AoA inputs.
Where else is this incorrect data reproduced? Through the DMC's as a PFD speed tape depiction of the critical speeds (hockey stick, tiger tail), which the pilots are referencing for their queues to base the test on. Maybe this explains why there’s no crew action?
The autotrim continues to trim back.
Finally, the ELACs (having failed to back up the Alpha floor based on…. you guessed it AoA inputs pg51) but now calculating Vs from the FMGC gross weight issue the STALL STALL warning. 15.45.05
The gear is down, so the roll and pitch default to Direct law, and as P2J rightly observes autotrim is then inhibited and the message “use manual pitch trim” appears on the PFD.
Yes, practiced in the simulator, but not coincidentally with a stall.
FAC1 / FAC2 deducing that the aircraft cannot stall in Normal law, send FAC1 fail FAC2 fail signals to the DMC’s. (Pg39)
When gear is retracted, pitch Alternate law is restored. (pg34).
If an aircraft is designed without control column feedback, with the only indication of impending stall artificially created and represented on the PFD, an aircraft hardly out of the factory but with 20years of service, then the calculation and depiction of that information needs to be infallable.
Can we point the finger at the pilots as the sole cause? Maybe! Do we lose the chance to isolate and identify an inherent systemic flaw. Yes