AAIB AIRPROX Report
HN39,
Re the AIRPROX report, I think some of us were not totally convinced by the AAIB's interpretation of the initial upset: their argument that turbulence caused a sudden increase in AoA sufficient to trigger phase-advanced Alpha-Prot.
We speculated that the pitch-up could have been due to overspeed protection. Then the AP tripped (for whatever reason). So the sequence would be roughly as follows:
(1) Overspeed protection causing pitch-up;
(2) AP disconnect (not sure why);
(3) lack of stick movement by PF allows a 1G trajectory, causing deceleration;
(4) Alpha-Prot is activated.
You remember my making reference to "phase-advance" in another context. We used to get phase-advanced stick-shake on the VC10 and BAC1-11. But I'm very surprised it could happen to the extent that the AAIB describes. (But I am. admittedly, often surprised!)
In haste,
Chris