Source = Northrop Flying Wings by Pape & Campbell. N9M #1 crashed during aft CG & control tests. Investigation concluded that there was a control reversal and the pilot was pinned into his seat by the control column. ( Low pressure pulling elevons up? ) #2 initial test flights showed severe reversal of elevator control forces at high lift coefficients. ( solved by designing a full power hydraulic control system ) MX-334 #1 hit propwash from tow plane after release, pitched up, stalled, flipped nose up, over onto back, went into spiral. Pilot was unable to reach the controls of the prone cockpit, so released the bottom escape hatch, ( now on top ) unstrapped, crawled out, and sat on wing for a moment before deciding he wasn't doing anything useful there, stepped off, and deployed chute, made good landing. ( can't blame CG for this one, sometimes prop wash /turbulance is just too much to overcome ) YB-49, stall testing, normal CG, flipped nose up over tumble, recovered @ 1000 ft. Pilot Cardenas said centrifugal force pulled arms up, but luckily the throttles were over head, and got one engine up to 100%, to recover. Must have been a wild ride. YB-49 #2 crashed, possibly from excess speed in dive after tumble/spin recovery. YB-49 stall testing with gear down to slow plane, stalled, snap rolled, recovered. I may be wrong about something here? I know that with hang gliders, and a variable CG, that holding near stall ( rear ) CG position can induce a tumble. Full speed ( fwd ) position invites over speed. And a high speed cruise position ( fwd of best L/D ) is best for turbulence. hmm.