The airplane’s angle of attack increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs. The vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left. The speed displayed on the left side increased sharply to 215 kt (Mach 0.68). The airplane was then at an altitude of about 37,500 ft and the recorded angle of attack was around 4 degrees.
From 2 h 10 min 50, the PNF tried several times to call the Captain back.
At 2 h 10 min 51 , the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of around 6 degrees at the triggering of the stall warning, continued to increase. The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight.
Gums: The initial 'zoom'climb' (for want of a better description), occurred
prior to significant THS movement, presumably as a result of normal crew input. Only after "the PF maintained nose-up inputs", following TO/GA selection did the THS move significantly away from what might be considered a normal attitude of 3 degrees.
I believe AoA protection is diminished as follows in ALT LAW:
AoA Protection: (a) alpha floor is lost. AOA is still monitored but warnings relate now to stall speed rather than AOA. Refer LOW SPEED STABILITY. If VS1G cannot be calculated due to loss of weight or slat/flap position information then there is no AOA protection at all.
My reading of the BEA note is that the THS did exactly what was commanded by the PF. The aircraft was already in trouble quite a while prior to the THS reaching 13 degrees.