What happened
During a high-speed test flight conducted outside of standard operating parameters, the aircraft experienced a period of elevator system oscillation. This vibration lasted for 17 seconds and was documented by the cockpit voice recorder at an average frequency of 28 Hz. During the final approach to runway 17, the crew observed the nose of the aircraft beginning to drop. Despite attempts to recover the pitch using engine power and horizontal stabilizer trim, the pilot could not maintain the necessary attitude. The aircraft subsequently landed short of the runway, making contact with a berm and an airport perimeter fence. At the time of the landing, surface winds were recorded at 23 knots from the south, with gusts reaching 32 knots.
Findings
Investigation into the mechanical failure revealed that the aft elevator sector clevis (p/n 2331510-32) suffered a fracture. This structural failure was attributed to reverse bending fatigue resulting from the intense vibrations experienced during the high-speed dive. This breakage led to a total loss of elevator control, which prevented the crew from effectively managing the aircraft's pitch during the approach phase.