Originally Posted by clandestino
Now, I would not expect 0.02 overmach in level flight to be dealt with by closing the TLs shut and keeping them there until high alpha protection kicks in and then watching and doing nothing for 17 seconds as aeroplane pitches up but that's just me.
The FDR data show that the airspeed did not change significantly in the 5 seconds between closure of the throttles and capture of alpha-prot. (To put this into perspective: the engines take more than 10 seconds to spool down to idle, the A/C then takes over 2 minutes to decelerate to V-alphaprot in level flight). From AAIB Bulletin No. 6/2001:
Five seconds after the autopilot disengaged, the thrust levers were closed and then the autothrust was disconnected, probably by the handling pilot in an effort to prevent another overspeed condition. Ten seconds after the autopilot disengaged, the corrected or phase-advanced angle of attack (a computed parameter which is not recorded but can be calculated by Airbus Industrie from the DFDR data) reached the ‘alpha prot’ value. This angle of attack excursion beyond alpha prot caused a change in the pitch flight control law from normal law (NZ law) to angle of attack protection law (AoA law).
(...)
Changes to the A340’s flightpath caused by the aircraft’s flight control system response to the overspeed warning and autopilot disconnect were negligible until AoA law was triggered. The fact that this law was not triggered until 10 seconds after the autopilot disconnected was a random event driven by the severity of the turbulence.
In the 17 seconds after capturing alpha_prot several attempts were made to reengage the autopilot, before moving the sidestick.
It would take a couple more seconds for it to activate nowadays in the same circumstances.
Are you sure of that?