What happened
On May 14, 1999, a Mudry CAP 10B, registration F-GRIT, departed from Lognes-Emerainville for a local flight. After approximately twenty minutes of flight, the aircraft was observed by a ground witness near the village of Chevru. The witness reported hearing significant engine RPM fluctuations and loud, explosion-like noises, followed by the aircraft being enveloped in a white cloud of debris. The aircraft then entered a steep dive and struck the ground.
Investigators found a debris trail spanning approximately 400 meters. A significant portion of the right wing spar, including the landing gear attachment, was found 70 meters from the main wreckage, confirming a structural failure in flight. The impact resulted in one fatality and the total destruction of the aircraft.
The investigation
The investigation focused on the structural integrity of the wing and the flight conditions leading to the breakup. The aircraft, a wood and fabric construction, had been used extensively for aerobatic training. While the aircraft had undergone a 1,000-hour inspection, investigators discovered that a component used in the manufacturing of the lower spar flange did not meet required mechanical specifications.
Furthermore, the investigation examined the pilot's experience and the aircraft's recent operational history. The aircraft had frequently performed high-intensity maneuvers, including numerous take-offs and landings on paved runways, which may have contributed to fatigue. The investigation also reviewed the regulatory framework regarding aerobatic privileges for professional pilots.
Findings
- The primary cause of the accident was the execution of aerobatic maneuvers that resulted in a load factor of +6.6, exceeding the aircraft's certified limit.
- The structural failure was caused by the rupture of the right wing spar at the root.
- The use of a non-compliant wooden plank during the manufacturing of the spar flange may have weakened the structure.
- Repeated hard landings and high-intensity training cycles likely contributed to the fatigue or prior damage of the spar.
- The pilot lacked formal, structured aerobatic training, which contributed to the inability to maintain the aircraft within its structural load limits during maneuvers.