Originally Posted by
Hamburt Spinkleman
To dismiss it because it does not support a theory, seemingly based on numbers that have been pulled out of a hat at random, is foolish.
That's our Lyman! (ba-dum-tish!)
In all seriousness though, what Lyman is not taking into account is the time factor of the calcuations for those readings and traces. One of the things I noticed on my A320 sim trip was that when an altitude capture is selected, the V/S display on the FCU module will initially display a surprisingly high value before it settles - I believe this is because the value is computed in real time and relates to what the V/S *will be* if the current pitch and thrust commands are maintained - of course, when the autopilot stabilises pitch after the initial pitch-up or -down, this value becomes something more realistic.
My theory is that the values on the trace are also calculated in real-time and those large bumps just before disconnect are a result of what the V/S *will be* if the current trajectory is continued, the pitch is retained and/or corrections are not made. The autopilot was engaged long enough to ride out the bump but did not have enough time to return the pitch attitude to 4 degrees nose-up, eventually coming to rest around 1.5 degrees nose-up. The aircraft would have regained cruise level on it's own, but slightly more slowly. Everything that happens after then (including the elevator movements that command the zoom climb) are a result of the PF's overcontrol of the sidestick.
I suspect that what may have spooked the PF was not something he saw that we don't know about, but something we do know about - namely this "bump" just before disconnect, which briefly brought the pitch attitude below 0 degrees. The residual autopilot command was enough to bring the nose back above zero, but I think he mentally programmed himself to correct it manually and unfortunately overcooked it. From then on they were in the zoom climb and things quickly stopped making sense for him.
@hillberg - read the thread from the beginning, it's always going to divide people but it has already been covered to death here and elsewhere.