> The problem does not go away if the plane starts 3,200 feet lower than
> the CIA's 17,000 feet. It's still a lot of lightweight metal to get
> out of the sky in 29 seconds. You can just make it with a ballistic
> (no air resistance) fall, but it hits at 630 MPH. That's an awfully fast
> speed regime to be assuming no air resistance. If you can believe this
> then it's not that much harder to believe the 17,000 foot drop with an
> initial speed of 82 MPH and final impact at 700 MPH.
If you note that there was an explosion part way down for the rear section. This tells me that the plane exceeded its speed design specs for the wings and they tore off, igniting the fuel in the wing tanks...this would agree with a trajectory pushing 700 mph at terminus. I assume you are referring to the 82 mph initial speed as the stall speed of the 747. With its nose torn off, its stall speed should be a bit higher. Keep in mind that sea level speed of sound is 630 mph or so, as I recall... Given an initial forward velocity of the nose section of any where from 200-400+ knots, at least a portion of this should be translated by planing effects into downward velocity. A 29 second time to impact is completely reasonable for the nose section. I agree that it could be specious for the upwardly climbing rear section, depending on how long the engines continued to produce thrust...
A jet engine is self powered, self pumped. There should have been plenty of fuel in the lines between the emergency shutoff valve (if it activated), as well as in the sump well for the injection manifold, and those bad boys take at least 30 seconds to rev down. They could easily have kept producing thrust for at least 10-20 seconds after the time of the initial separation. If the initial explosion welded the wire harnesses (they travel right by the fuel tank), then the engines should have kept seeing a closed control circuit and kept running...Most of the power distribution and control equipment is in the area around the wing root, so the 747 could have kept running like a chicken with its head cut off, for at least a little bit.
This is the reason why ejection systems like the F-111 capsule have little guillotine solenoids to sever the controls harnesses, rather than explosive charges like the mechanicals have. They don't want any circuitry welding closed and presenting a normally closed circuit to the plane.