Reminds me of a scenario I saw in a 767 Sim a few years ago. A standard Go-Around from about 200ft AGL with autopilot engaged. Missed approach altitude was 3000ft. Everything appeared normal, we had altitude capture and the nose lowered as we approached 3000ft. BUT the nose kept dropping and dropping. At about 20 degrees nose down I disconnected the autopilot and manually flew a nose low upset recovery. It turns out the automatics had not captured 3000ft but a much lower altitude (we suspected about 1000ft). So the mechanics of what happen was as follows:
- After pressing the Go-Around switches the engines went to Go-Around thrust (normal).
- The Autopilot raises the nose to climb away (normal).
- The Autopilot trims the STAB nose down to counteract the large nose-up pitching moment due to Go-Around thrust (normal).
- The automatics captured ~1000ft instead of 3000ft (NOT normal).
- As we were climbing (or had climbed) through 1000ft, the autopilot commanded a nose down attitude to regain 1000ft.
- With the nose attitude decreasing and Go-Around thrust set, the speed started increasing rapidly.
- The autothrottle then set idle thrust in attempt to control the speed.
- Now here's the kicker: The autopilot had trimmed nose down to counteract Go-Around thrust. With the thrust rapidly reduced to idle, the now unbalanced pitching moments caused the pitch attitude to rapidly drop through 20 degrees nose down. The autopilot did not react quick enough to counteract the rapid nose down pitch change.
That might be a factor in this incident. Go-Around thrust activated. Nose down trim applied to counteract the nose-up pitching moment caused by Go-Around thrust. Nose lowered to regain the vertical path, but speed rapidly increases due Go-Around thrust. Thrust rapidly reduced to control speed. Pitching moments are now unbalanced and nose rapidly drops to a very nose low attitude. Startle effect and confusion overwhelms the crew.