Concour77,
Your posting:
If memory serves the attitude of the a/c just after the loss of Auto Pilot was 15 degrees right roll, minus two degrees ND. That is almost five degrees too low, and 15 degrees more than level wings. So it did not "start to roll" whilst the two pilots were "diagnosing" their situation?
From the Final Report:
The first disturbances in speeds 1 and 2 occurred at about 2 h 10 min 04, causing the autopilot to disconnect, which was signalled by a visual and an aural (cavalry charge) warning. The crew did not necessarily perceive these transient losses of speed information and the associated losses of altitude.
In addition, the crew’s mental resources were already taken up by turbulence avoidance maneuvers and the plan to climb during the minutes that preceded the autopilot disconnection.
When the autopilot disconnected, the roll angle increased in two seconds from 0 to +8.4 degrees without any inputs on the sidesticks. The PF was immediately absorbed by dealing with roll, whose oscillations can be explained by:
ˆ A large initial input on the sidestick under the effect of surprise;
ˆ The continuation of the oscillations, in the time it took to adapt his piloting at
high altitude, while subject to an unusual flight law in roll (direct law).
Following the autopilot disconnection, the PF very quickly applied nose-up sidestick inputs. The PF’s inputs may be classifed as abrupt and excessive. The excessive amplitude of these inputs made them unsuitable and incompatible with the recommended aeroplane handling practices for high altitude ight. This nose-up input may initially have been a response to the perception of the aeroplane’s movements (in particular the reduction in pitch angle of 2° associated with the variation in load factor) just before the AP disconnection in turbulence. This response may have been associated with a desire to regain cruise level: the PF may have detected on his PFD the loss of altitude of about 300 ft and loss of vertical speed of the order of 600 ft/min in descent. The excessive nature of the PF’s inputs can be explained by the startle effect and the emotional shock at the autopilot disconnection, amplified by the lack of practical training for crews in fight at high altitude, together with unusual fight control laws.
Although the PF’s initial excessive nose-up reaction may thus be fairly easily understood, the same is not true for the persistence of this input, which generated a significant vertical flight path deviation.
There remain a number of possible explanations:
ˆ The crew’s attention being focused on roll, speed or on the ECAM;
ˆ The initiation, more or less consciously due to the effects of surprise and stress,
of the action plan (climb) desired by the PF prior to the autopilot disconnection;
ˆ The attraction of “clear sky”, since the aeroplane was flying at the edge of the
cloud layer;
ˆ A saturation of the mental resources needed to make sense of the situation, to
the detriment of aeroplane handling;
ˆ The presence of turbulence that may have altered perception of aeroplane
movements in response to his inputs.
In answer to your final comment, the things they could have done, was to correct the roll, adjust the pitch angle and pause, doing basically nothing, until diagnosing the problem rather than reacting immediately to something not understood.