Jet Jockey
The AOA Sensors were found to have frozen in place at a relatively flat angle. (due to the plane being washed with a pressure hose, allowing water to get into the workings of the AOA sensors which then froze at altitude)
The crew initiated a near stall moment as part of their flight tests to make sure the AP did it's flight envelope protection job.
Aircraft pitched up as it's supposed to, but due to the stuck AOA sensors, it thought it was still on the level and still slowing, so commanded the nose further up. By the time the crew realised something wrong, the AP had given up, given them control and threw up the "USE MAN TRIM" warning.
As I understand it, with the stabiliser in full nose up trim, and with the low airspeed, the elevators did not have enough authority in the time given to recover the plane before it stalled.
The investigation noted that the pilots were most likely relying on the plane fixing the situation. But when it called quits, it left them with a plane about to fall out of the sky.
Last edited by LiveryMan; 28th Jan 2015 at 14:18.