What happened
During the final approach phase at Hilton Head Airport, the Mitsubishi aircraft experienced a sudden right-side roll and rapid descent. Eyewitnesses reported that the plane struck trees at an altitude of approximately 70 feet before hitting the ground. The impact triggered a post-crash fire, and the resulting debris field stretched roughly 3/4 of a mile along an 082-degree azimuth.
Findings
Investigation of the wreckage identified significant discrepancies in the configuration of the wing flaps. Measurements of the left wing flap actuator and jack nut indicated the left flap was extended to 40 degrees, while the right flap was positioned at approximately 20 degrees. The investigation determined that the right flap torque tube assembly, which connects the flap motor to the flap stop assembly, had become disconnected.
Specifically, the female coupler of the flap stop assembly contained a cotter pin that had failed to secure the male spline of the flap motor. This installation deviated from the standard procedures outlined in the manufacturer's maintenance manual and the requirements of Airworthiness Directive 88-23-01. Furthermore, the opposite side of the flap motor was found to be missing its cotter pin entirely.
Maintenance logs indicated that the aircraft had undergone an inspection related to Airworthiness Directive 88-23-01 on April 3, 2001, roughly 87 flight hours prior to the accident. This specific directive required the disassembly, inspection, and reassembly of the flap torque tube joints. While a phase 1 inspection was completed on July 9, 2001, and the aircraft was certified for service by an authorized technician, the improper installation of the cotter pin led to the mechanical failure.