ORIGINAL: Pete737
ORIGINAL: David Searles
Spark's crash was insufficient airspeed, pure & simple. Tried to haul it off the ground before adequate airspeed had been obtained. Stall & crash.
The second flight appears as though the bug was tail heavy. Even after he got off the elevator, right after take off, the jet still wanted to climb. As such again he couldn't build sufficient airspeed, stall & crash.
Also it rarely makes sense to do first flights fully loaded with armament! Without all that extra drag, he might have been able to stabilize that jet, but with the bombs he didn't have enough thrust to continue to accelerate airspeed. Also it looks as though as the bug began to stall he pulled back on the stick to try to keep it flying.[:@] Should have done the exact opposite. Push the nose over and get the AOA down and give it time to build more airspeed.
David S
After the jet has entered this environment, How effective are the control surfaces?
When the wing stops creating enough lift to support the aircraft, the control surfaces essentially become useless for anything other than creating additional drag. The extreme pitch-up you sometimes see on bugs that are in the process of departing controlled flight is caused by the extreme drag created by the typical full up elevator input the pilot is inputting contrasting with the final vestiges of lift still being created by the LEX's. If allowed to stall or depart without that input, the bug will typically just drop straight ahead.
When the wing stops flying it will sometimes drop to the side of the wing with higher drag. When the pilot attempts to counteract this with opposite aileron input, since the wing is no longer creating adequate lift, the aileron input just adds increased drag and over she goes. I think their is a pretty good explanation of this, probably better than mine, given by the Test Pilot instructor on video three or four of the series on Test Pilots.
David S