speeds and angles
I am sorry if this is redundant. I have been on and off here and have not had time to read every single message.
In an effort to investigate the difference between the data at point 6, 2:11:40 (35,000 ft, 10,000 fpm down, AoA > 40 and pitch angle 15) and impact, 2:14:28 (0 ft, 10,912 fpm down, groundspeed 107 kt, and pitch angle 16.2) I measured the ground distance along the flight path from point 6 to impact. (I did this on the assumption that the BEA graphics are computer-generated from GPS data and are therefore precise.) It is about 7.37 nm. The elapsed time is 2.8 minutes. The average rate of descent is 12,500 fpm and the average groundspeed is 158 kt. The average true airspeed is 201 knots, the average glide path angle is 38 degrees. Assuming that the pitch angle does not deviate much from 15-16 degrees, the average angle of attack is 53-54 degrees.
Since these numbers do not match those at either the starting point or the impact point, there must have been considerable variation in between, and in particular a higher rate of descent.
While I have argued (and written) against the "deep stall" theory, which unfortunately remained untested by the crew, I am having a hard time understanding how this airplane managed to maintain this high an angle of attack for this long a time without departing into a spin. Can anyone point me to wind tunnel or flight test work relevant to transport aircraft of this configuration at extreme angles of attack? The Langley stuff I've found is all about spinning. I'm going to telephone them tomorrow.