What happened
On August 19, 2012, at approximately 18:35 local time, an Exel microlight motor glider, identified as 30-PO, was involved in a fatal accident near Aspres-sur-Buech, France. The pilot, who was also the owner of the aircraft, had departed from the Aspres-sur-Buech airfield at 14:00 for a local flight.
While flying over the ridges northwest of the airfield, witnesses observed a section of the wing detach from the aircraft. Following the structural failure, the aircraft entered a series of spins before stabilizing in a steep dive, ultimately crashing into a field. The accident resulted in the death of the pilot and the total destruction of the aircraft.
The investigation
The investigation focused on the structural integrity of the wing assembly, which consists of a fuselage and a wing made of two semi-wings connected to a spar (or wing key) via two pins. Investigators identified the failure point at the junction where the spar meets the right semi-wing, specifically around the connection pin hole. Examination of the fracture surfaces revealed characteristics of a sudden, brittle failure caused by structural overload, though no pre-existing structural anomalies were found.
Data retrieved from the aircraft's flight computer indicated that the pilot was actively controlling the aircraft until the moment of the breakup. Analysis of the 30 seconds preceding the failure showed that the aircraft was being flown at high speeds and high vertical rates. During the final 10 seconds before the structural failure, the estimated airspeed ranged between 188 km/h and 208 km/h, depending on wind calculations.
Findings
- The aircraft was operating at speeds significantly exceeding the manufacturer's maximum speed (VNE) of 180 km/h.
- The structural failure of the wing spar was caused by excessive aerodynamic loading during high-speed maneuvers.
- At the time of the failure, the spoilers (air brakes) were in the retracted position.
- The pilot had previously performed aerobatic maneuvers in the aircraft but had ceased doing so following manufacturer advice; however, the flight data confirmed the aircraft was subjected to high-speed descents and high vertical velocities immediately prior to the accident.