Originally Posted by
Machinbird
We have seen three B737 fly into the ground/water at steep angles in recent years, and there appears to be a common thread.
- All were significantly out of trim nose down,
- All experienced zero g or negative g during the pitch over,
- All did not significantly reduce their angle of descent once they started down.
As pilots, we have to ask, how did this happen? How did these crews get themselves so badly out of trim and why couldn’t they at least try to pull out of their dives?
The answer is beginning to emerge that they could no longer control their aircraft in pitch! I suppose it is not surprising that an aircraft that is trimmed heavily nose down might be hard to keep in level flight, but there are several effects that do not appear to be widely understood that are making this situation much worse than it initially appears! My education began with a PM question to FCeng84 on control jam prevention measures implemented in the 737. FCeng84 has agreed to the sharing of his replies.; This is not his or my complete response, however. There is more detail available.
After some back and forth discussion: FCeng84 had the following observation:
Thank You Machinbird, very interesting analysis, you and FCeng84 have done an exceptional study.