Originally Posted by Denise Moore
Why the initial climb?
The answer can be speculated from the BEA report.
When AP disconnected the a/c was pointed down slightly (Pitch=0 deg) and it was descending. Also altimeter might have jumped down a few hundred feet because of impared pitots and air temperature sensors due to a possible ice build up from the strom they were in.
Pilots are trained to maintain altitude in cruise so he correctly pulls the stick back to keep at FL350. It appears he was in a down draft because it took a large stick deflection to maintain altitude for a few seconds. At high altitude and speed his strong stick input has dangerous effects and a stall warning is triggered. He then notices airspeed is broken. We can speculate that he was distracted, took his attention away from altitude and tried to process what was happening. More errors occur further distracting him. Finally the a/c has risen to FL375 before he figures out he has climbed, he had exited the downdraft and had held the nose up attitude.
Climbing the aircraft without adding power results in a drop in speed. Same as a pendulum swing up. Now a/c was in a dangerous high altitude and low speed condition with impared flight controls (ALT LAW).