What happened
On June 5, 2014, an Avid Aircraft Inc ultralight, registration 73-JU, was performing a training flight at Albertville Aerodrome. After completing a circuit and a full landing on runway 23, the instructor and student prepared for a new takeoff. Immediately following takeoff, a witness observed the aircraft entering a right-hand turn at a low altitude. The aircraft subsequently struck the ground and caught fire, resulting in two fatalities (the instructor and the student) and the destruction of the aircraft.
The investigation
The investigation focused on the mechanical condition of the engine and the physical health of the crew. Examination of the Rotax 582 engine revealed that the bronze drive pinion of the air intake rotary valve had been destroyed due to wear. This failure caused the sudden engine shutdown. Investigators also found that the crankshaft runout exceeded manufacturer specifications, which likely accelerated the pinion's wear. Furthermore, the engine contained several non-standard parts, including incorrect connecting rods, piston bearings, and spark plugs. Maintenance of the aircraft was performed by the instructor and co-owners, but the maintenance manual could not be located, and no maintenance traceability was available.
Regarding the crew, post-mortem examinations of the instructor revealed coronary artery disease and the presence of certain medications, including an antidepressant and a beta-blocker. Biological analyses showed high levels of a cardiac marker, supporting the hypothesis of an acute coronary event during the flight. The student was a relatively inexperienced pilot with approximately 89 total flight hours.
Findings
- The primary cause of the accident was the physical incapacitation of the instructor, which prevented him from controlling the aircraft's trajectory following the engine failure. The stress of the sudden engine failure likely triggered the medical event.
- The engine failure itself was caused by the advanced wear of the bronze drive pinion, resulting from improper engine maintenance.
- The student's limited experience likely prevented him from managing the simultaneous occurrence of the mechanical failure and the instructor's incapacitation.
- The instructor's underlying medical condition and medication use were contributing factors that were not properly accounted for in his flying activities.