Originally Posted by
_Phoenix_
See Figure 26 of final report. In only 2 seconds, after AP disconnect, the roll angle passes from 0 to 8.4 while roll input remained neutral. Next 15 seconds, PF continuously corrected the right tendency of the aircraft, 4 times, 2 times at left limit stop.
Right, so let's look at that a bit more dispassionately.
AP disconnects at the red line, seemingly while damping a left bank, presumably from turbulence. At AP disconnect, for 0.2 seconds the pink "Roll Attitude" graph indicates a cessation of roll (stable at about 0.8 deg right), followed by a subsequent right roll, beginning at 02:10:06.4 over 0.8 seconds, peaking at 8.4deg right around 02:10:07.2. This seems consistent with a "bump" caused by turbulence - we don't know how the situation would have progressed, because it is countered with a left-bank control input.
The fact that the input graph is rendered at 180 degrees (i.e. opposite) to the attitude graph makes it a bit of a 'mare to read, but Bonin moves the stick to the half-left position to correct what is presumably a turbulence-induced roll. This seems to be an instance of overcontrolling, because the aircraft then rolls 6 degrees to the left.
The controls over the next 15 seconds or so look very much like a case of opposite PIO in roll until he begins to get a feel for what he's doing, and the roll oscillations begin to stabilise.
For this reason I'm not sold on the "incipient spiral" theory. Furthermore, Bonin's completely unnecessary pitch inputs begin simultaneously with the roll inputs at 02:10:07. No reasonable time is given to assessing what is actually happening in terms of the aircraft's status, and from that point on, every input he makes is reactionary.
Originally Posted by
infrequentflyer789
After decades of censure from some quarters over its implementation of hard-protections overriding the pilot
The hard protections don't "override" the pilot, they give the pilot what he or she is asking for up to the safe limit of the airframe, and will continually monitor the aircraft's status to comply with the commands given to the best of the aircraft's ability.