Originally Posted by
DaveReidUK
I plotted a GE 3D trajectory when the data became available (similar to the one subsequently posted). I didn't post it because the data is sparse and it didn't strike me as particularly informative ...
When you did your 3D trajectory check, you did see a parallel movement from the last point before the upset until the first point with altitude loss that is in the order of 1600m. During these 15-20s the aircraft moved much more to the left (seen in the direction of
flight) than it lost altitude. The following points also show the same lateral displacement. It was not a position glitch.
Many other (except we two), only did look at the course that seem to not have changed and from this they probably did draw the not correct conclusion that the aircraft did continue straight ahead with a nose down input. Which it did not.
The lateral displacement to the left need a (steep) left bank to take place. This part you will not see on a 2D dive profile from the side.
The SJ182 accident have the same lateral displacement (also 1600m) but that ADS-B track do not have a gap of 15-20s during the turn so for SJ182 those points show the left roll leading to the inverted dive/barrel roll.
Without 3D, or at least looking at this with 2d from both the side and from above, you wint notice the lateral displacement to the left that tell us that a left roll had a dominant part of the upset.
MU5735
initiated the upset by a left roll with positive G, probably just what we would see if a pilot get disoriented and fly a about 1G seat of the pants pitch during the roll.
The dive following the lateral displacement is probably inverted initially and the about 1G barrel roll continue until the aircraft is almost right on the wings again.
Engine failure, Auto throttle failure or something that caused the initial part of the roll followed by spatial disorientation or a IRS failure maybe.