What happened
Following an engine overhaul and an annual inspection performed by the owner/mechanic, a Cessna 172 departed on its first flight. During the final approach, as the pilot extended the flaps to the last notch, an audible "ping" was heard. Shortly after the pilot retarded the throttle, the aircraft's descent could not be arrested. The aircraft subsequently dove to the ground and experienced a nose-over.
The investigation
An FAA inspector examined the aircraft and found that the up elevator movement was intermittently restricted by a radio rack. While the radio rack was found to be tight in place with no evidence of shifting or looseness, the elevator's range of motion was significantly altered. Specifically, the up elevator movement was only half of the specified amount for the aircraft, while the down elevator movement was 150 percent of the specification.