What happened
On September 25, 2009, at 18:05, a Colomban MC 100 (registration F-WHRJ) was engaged in a test flight near Hudimesnil, France. The aircraft, an amateur-built design, had recently been completed by the pilot. The flight originated from Avranches aerodrome for the purpose of an endurance flight to obtain a restricted certificate of airworthiness.
After approximately two and a half hours of flight, radar data indicated that the aircraft, which had been stabilized at an altitude of roughly 3,000 feet, entered a steep descent. The aircraft subsequently struck the ground in a cornfield with a high pitch-down attitude. The accident resulted in one fatality and the destruction of the aircraft.
The investigation
The investigation focused on the elevator control linkage, which utilizes a linkage rod to connect the control stick side to the elevator side. Investigators discovered that the linkage rod and the elevator-side rod had become disconnected at the wreckage site.
Examination of the components revealed that the bolt intended to secure these two parts was missing from its housing at the time of impact. Furthermore, the end of the elevator-side rod showed minimal marking around the bore, suggesting that the bolt had been insufficiently tightened.
While the aircraft designer's plans specified that the nuts on the elevator control linkage bolts must be safety-wired (lock-wired), investigators found that several bolts had not been secured in this manner. Although the pilot was described as a meticulous builder, the investigation noted that while other amateur builders had assisted during various stages of construction, the pilot had not requested a final assembly inspection from an experienced third party prior to commencing flight operations.