BOAC;
PJ - can you explain the logic of the angle of attack protection
Thank you for the question. I want to say something.
I am a mere bread-and-butter retired Airbus pilot who loves technical and human factors knowledge and who labours under a peculiar fascination concerning this aircraft which I flew and this design and its history. Years ago I heard
ET's presentation on "
Why We Designed Them the Way We Did" (and have the paper on same), and have alternately embraced and puzzled over the airplane since first flying the A320 in 1992 and the A330/A340 in 1999. I have been educated by those with far more experience than I on the Airbus and by some engineers who are possessed by an unusual patience and ability to explain things to a pilot.
Though I would like it to have been otherwise, I know nothing of aerodynamics or computer control systems. I know something about flying the Airbus and its "habits", and how to stay alive flying airplanes, a bit about flight safety and organizational factors in accidents and a bit more about flight data analysis.
The singular thing this thread has taught me is how little I really know, and what a pleasure it is to learn from others, a relationship which I hope is reciprocal. The older and greyer I get the more willing I am to let stuff lie in the weeds because this stuff always surfaces. I am less willing to "pronounce" on the why, the how and the what in sophisticated systems into which I have the merest cracks to peer through. On staying out of trouble in the Airbus, I think I can say something of value and have. But, despite the usual conspiratorial crack-pot views, for easily understood reasons I lean to trusting the BEA
on this one and am willing to wait to see what they have to say on various points so intelligently raised but frustratingly pondered here.
My views on the AoA item?...I think its "ordinary" vice "extraordinary". I would guess that in this AoA Protection Law we are simply looking at a response to the standard right-hand side of standard buffet curves, I can only posit that the airplane would pitch up "on the Alpha Prot AoA" in accordance with the design, perhaps with input from the High Speed Protection Law, who knows? We know from the AAIB report (if not from access to AMMs, AWMs & TSMs, etc), that when the Alpha Protection Law is invoked due to high Mach No., a pull on the stick would take the aircraft (in Normal Law) to Alpha-Max
and no further. The risk of an accelerated stall is assumed to be low to nil in Normal Law. We also know that the pilot can intervene fully, with a stick-forward (ND) response to essentially cancel the AoA Law once below the Alpha Protect Law triggering point. Rather than second-guessing the designers and the engineers on each point and at every turn, perhaps thinking about why the design is the way it is
in toto to see what problems are being solved? I think it is fair to say that some credit after all, must be given these people who, with the exception of one or two who have contributed to the thread, know far more about the design. Would we have the aircraft pitch down as per the low-speed Alpha response?...I don't think so. I think we have to think about it a bit, in the context of the Airbus design and not in the context of non-fbw designs and expectations.
To me, the AoA response makes complete sense as a pilot of the Airbus. What has not been either appreciated or grasped by many, is, from the beginning, this design has required a different way of thinking, a different approach to training, to flying, to anticipating behaviour and to interacting with the machine, and it absolutely requires a positive attitude and approach towards it. If one is forever either fearful or hostile or otherwise actively diffident towards the design and the airplane, like prejudice itself, no amount of discussion, facts, knowledge or perhaps even actual engagement and understanding, is going to change one's mind. And that too, is a human factor.