Originally Posted by Lonewolf_50
the absence of evidence is not evidence of absence.
There is evidence of turbulence - I think it caused the "stall warning twice in a row" shortly after 2:10:05. There is evidence of the absence of a strong, sustained updraft that "pushed" the airplane up to FL380 before 2:11:06 - see below.
Vertical air column velocity, were it encountered, would vary from about 2800 fpm to 6000 fpm based on the numbers you offer in your response to wally. That cannot account for the 7000 fpm climb by itself. It seems pretty obvious that the "big climb" was an energy tradeoff, if not in whole than at least to a substantial degree.
Precisely. A strong, sustained updraft would have been evident as an increase of the total energy of the airplane. On the contrary, there was a slight decay of total energy up to the point where the airplane stalled. Another poster on this thread has correctly explained that decay as the result of thrust reducing with altitude and increased drag due to manoeuvering airloads.
Assume for a moment that the plane encounters a 2800 fpm up draft as the pilot has begun to operate in alternate law. To get the 7000 fpm vertical rate, the pilot contributes about 4200 fpm to that via trading energy for altitude ...
Not so. The gain in altitude is entirely consistent with the loss in airspeed, except for the decay discussed above.
A gust load of that magnitude from outside would, I think, leave a trace in the g sensed by the flight control system.
Agreed, and on the AoA trace, and also small-scale turbulence would appear as "grass" on those traces, provided the sampling rate is high enough. These can be separated from changes due to control inputs by looking at the traces of elevator and THS position, and sidestick positions.
I also don't grasp how the flight control system filters such external loads in the various laws.
If you are referring to my reply to BOAC, I didn't say that the FCS filters loads. I was referring to signal conditioning that suppresses high-frequency content of, e.g., the AoA signal, before it is passed on to the consumers.