This may or may not be relevant to this accident ...
Bill Thompson's book
Cessna - Wings for The World II has a detailed description of the crash of the prototype Cessna 340 on its maiden flight in 1970:
"The flight was uneventful with gear retraction, flap extension, general handling characteristics, and approach to stalls being investigated at 10,000 feet. Don decided to investigate the top speed and applied full power in level flight. The chase plane [the C-414 prototype] was about 50 feet below and 100 feet in trail when the elevator trim tab on the C-340 began to cycle about 10 cps and then jammed 30 degrees up-tab (nose down trim). Don immediately reduced power to idle. This caused the chase plane to overtake the C-340. The chase plane rolled right to clear the C-340 and immediately rolled back left to resume the chase. The C-340 had already pitched down 30 degrees and continued to pitch down in an outside loop until reaching the 120 degree point below the horizon. Several pieces of metal started to come off the aircraft and it then pitched back to about 70 degrees nose down and rolled over inverted and started into a flat spiral. The aircraft impacted the ground still inverted. [...] Later investigation confirmed that the bolt connecting the elevator trim tab rod and trim actuator had become disconnected during the flight. The trim-tab cycled a few times and then jammed up-tab. This created about 300 pounds of forward force on the control wheel which Don could not overpower."