Capn Bloggs, re, "Having to fly an aeroplane differently because it's systems have had a dummy-spit is not training the way you fight. Throw in autotrim with backstick and you've set the crew up for a big fall. "
In the interests of accuracy in a serious discussion on automation which is being read by many, I beg your indulgence regarding the following:
The assumptions behind your statement are inaccurate and incorrect. As such the statement is misleading, particularly to those who are just trying to understand these issues, as they may have related to two known accidents.
It is unfair to the discussion to claim that the aircraft has to be flown "differently". It does not, and it is incorrect to claim this as fact, particularly if one has not trained on, checked-out on and flown the type.
To be clear, the aircraft requires no special handling in Alternate Law. It requires the same handling you'd give any other transport aircraft at high altitude, high Mach Number under the same circumstances.
To the contrary, there is nothing normal about pitching a transport aircraft up to 15° at FL350 and keeping it there. Every other transport aircraft would have behaved the same way, given the same treatment.
In the case brought up (AF447), the moment the airspeed information had been lost, the PF pulled the stick back and increased pitch, reducing energy & speed. The THS moves to neutralize elevator forces. In response to the up-elevator commands from the sidestick, the THS began to move only after sixty-seconds of nose-up input by which time the pitch had increased to 15°NU and the AoA to 12°. The stall warning was sounding continuously by this time with an 11,000fpm descent rate.
From that point, it took a further 45 seconds of consistent nose-up input to take the THS from normal cruise settings 2-3°NU to 13° NU by which time the aircraft had been fully stalled for two minutes and was passing FL290 in the descent.
For reasons we may never know and understand, the aircraft was severely mishandled, just as QZ8501 was.
When an ordinary line pilot enters test pilot territory there are quite possibly risks of a "big fall", but as with any other aircraft, not until. The aircraft itself performed as flown.
Last edited by FDMII; 1st Feb 2016 at 14:27.