Originally Posted by
Lyman
From it, I conclude the zipper may have held his attention as to V/S and influenced his inputs, perhaps well into the "climb". My opinion only.
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I only suggest that that the "zipper" can't just be discarded as irrelevant.....
Had he not judged his V/S accurately, how was he to suss his actual ROA?
Having now spent time in an A320 simulator, I can tell you that in MANAGED mode, the corrections applied by the autopilot are displayed in that window. "-5000" appears, but only for a fraction of a second as the slight corrections are applied. I'd be very surprised if that interrupted his instrument scan (of which the FCU display should only be an occasional part) and led him to conclude they were descending for two main reasons.
1. They are a regular occurrence in MANAGED mode, and lots of corrections are expected in this scenario. He may have been relatively low-hours for an airline pilot, but this is one scenario where spending a lot of time with the automatics in would have led him to discount that as anything to worry about.
2. He did not start climbing until the automatics disengaged, at which point (as you'd expect), the "zipper" stops.