Originally Posted by
CONF iture
The margin is already in alpha max and that is why alpha max has not been set to alpha stall and V alpha max is not Vs1g.
A very temporary excursion over alpha max is acceptable and is part of the protection mode. The system will not try to achieve anything more than alpha max but it will tolerate an overshoot if turbulence or sudden turn happen when already established at alpha max...
Honest conjecture - please don't be offended, but that's your interpretation and yours only.
You mention the Airbus demonstrator saying/showing "the airplane will rapidly reach alpha max", but I bet the demonstrator said nothing about it reaching a precise 17.5 degrees of AoA with the same urgency. The manuals, both FCOM and FCTM, seem to shy away from giving precise quantitative values for limit and rate when describing the procedure and functions, and this makes sense because there will be occasions where to do so would be inadvisable (e.g. adverse weather and/or a decelerating aircraft).
I mentioned this before, but I'll point out again that the difference between Bilbao (where phugoid damping was an issue) and Habsheim (where it most likely wasn't) was a gusting tailwind causing a sudden (approx. 10kt in under a second) drop in IAS in the former case.
The demonstration video by Capt. Corps would likely have been seen by Capt. Asseline, and in all probability he'd have sat in on a similar demonstration using the prototype (with the AoA gauge) - therefore he'd likely have been aware that immediate response to full back-stick in the landing configurations with protection active would have been in the 15-16 degree range.
The absolute Alpha Max value of 17.5 degrees was mentioned (albeit obliquely) in the BEA report to which both Asseline and his legal team would have had access prior to the court cases. Given the myriad ways in which they tried to draw attention to Airbus and possible technical issues, one would think that the apparent discrepancy between that absolute value and the AoA achieved would have made a cornerstone of their case, but it wasn't even touched upon. The only reasons I can think of that this would be the case are either that they missed it (IMO unlikely), or that they knew such behaviour was normal and therefore not a technical fault or design flaw.
[EDIT
Originally Posted by
roulishollandais
To avoid a new AF447 and his autotrim problems, inhibit Alpha-Floor, and modify alpha-max at or above Cz-max...
AF447 was in Alternate Law (2b) which does not have Alpha Floor (or for that matter any hard alpha protections) available. The autotrim behaviour was not a "problem" in the purely technical sense - it was simply trying to comply with the demands of the pilot.
Why not put these switches on the consoles again to give observability and controllability
to the "ordinary" pilots?
Because the automatic switching mechanism has been proven sufficient and safe during over 2 and a half decades of operation. Also, apropos of nothing, the B777's bypass mode exists as we know, but in the very few incidents where it might have been useful (I'm thinking in particular of MH124), none of the crews used it because they were too busy trying to control the aircraft.
PS. Gums is certainly not an ordinary pilot - I'd love to see him get a go in the A320 prototype one day to help him understand how it all fits together and why.
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