Originally Posted by
exosphere
……. Entering such a dive would require a relatively quick pitch down which also means negative G’s, maybe exceeding final load factor.
Assuming the descent started at the time of the last cruise data point, a big assumption !
To lose 2,000 ft in 14 seconds is average about plus 0.3 g.
As long as the descent started at least 11 seconds of the first altitude readout of 27,025 ft then zero g would suffice.
Coincidently, if the descent was at an average of zero g for 11 seconds the rate of descent would be 21,737 ft/min at the next data point, 27,025 ft. using my simplified calcs. Assuming gravity, G = 10 m/s etc. So rough calcs.
The data point from FR24 gives a Rate of Descent at 21,696 ft/min.
So surprisingly similiar numbers. Maybe I made a mistake in my calcs.
But if correct, the aircraft didn’t need a high negative g bunt to achieve the initial descent, just a lack of lift.
All pretty horrible, but many scenarios achieve these numbers. 2 immediately spring to mind.
1: Wings level zero g profile.
2: a roll past or near 90 degrees.
1: The wings level zero g scenario seems highly unlikely, a jack fail or trim run away would in my guess be unlikely to achieve exactly zero g. I would assume some sort of dramatic manoeuvre but this is not an area where I have any expertise.
2: So very little lift component up. The problem with the roll case seems to be the lack of heading change.
The fidelity of the FR24 data may mask track changes. I note a 2 degree track change to the left passing 27,000 ft and 10 degrees left passing 25,000 ft. It’s back on track,( 100 degrees ) at 22,500 ft, but by 15,000 ft it’s now deviated to a track 40 degrees to the right.
A slow spiral ?
I can’t tell from the numbers. Maybe someone can.
equations used.
V^2 = U^2 + 1/2 a t ^2. V = velocity achieved, U initial velocity ( 0 in this case ) , a acceleration, t time
S = Ut + 1/2 a t ^ 2. S = distance