Quote from A33Zab (my emphasis):
"Besides this there are more updates since the event.
BUSS(before event) and further enhancement >Reversible BUSS.
Hybrid FPA.
Visible Red 'STALL STALL' warning on PFD."
The problem with a simple "STALL, STALL" warning on the PFD is that it is qualitative, but not quantitative. How is the pilot to decide what degree of pitch-down to apply?
In the past on swept-wing jets, we have been advised on the receipt of a stall warning to pitch down a relatively small amount AND apply TOGA thrust. While that technique has recently been rightly criticised (not least on this thread and its predecessors), it would probably suffice in most cases if the first activation of stall warning has happened immediately the stall AoA is exceeded - as would normally be the case on final approach. But in the event of UAS, the stall warning may not occur initially because of the consequent invalidation of AoA data. In that case the first stall warning activation may not take place until the a/c is already in a well-developed or even deep stall.
That is why I'm suggesting consideration be given to the provision of an AoA indicator that would appear on the PFD only in the unique situation of stall-warning activation. The degree of exceedance of stall AoA could be approximated in a clear graphic on the indicator, giving the pilot a good cue as to what kind of pitch-down may be required to start the recovery. I say "approximated" because some data needed to calculate the precise stall AoA may be unavailable or unreliable, but the stall warning system itself must be using a credible value.
After the initial pitch-down, a secondary stall could be more easily avoided in the subsequent pull-up if the AoA indicator remained displayed until the AoA (and perhaps pitch-attitude) returned to within normal ranges.
Yes, I realise this would increase the airlines' training costs...