I know several have tried to make sense of the FR24 Speed and Altitude recording during the descent. However if you look carefully at the precceding information it is gives a better clue as to what has happened.
Before timestamp 7:39:28 both the altitude and speed were increasing, i.e both Kinetic and Potential Energy were increasing normally, as they passed 10,000ft.
After this the speed remains constant at 270 knots, maybe because of autopilot speed hold. During this period of constant speed the energy increased by 33ft/s x 100,000lbs auw. i.e = 3300,000 ft.lb/s , which divided by 550 give a horsepower equivalent to 6000 hp.
Then at 7:40:05 the climb stops and the airplane starts to descend, it looses any further energy input from the engines.
Then at 7:40:09 (4 seconds later.) the speed also starts to vary. The data beyond this point is meaningless as we don't know the pitch angle of the aircraft.
So it looks as if either one or more engines suffered a catastrophic failure, as the +ve energy input stops abruptly at that 7:40:05.
Last edited by phiggsbroadband; 10th Jan 2021 at 22:36.