What happened
On August 5, 2001, at approximately 16:30, a microlight aircraft, identified as 37-NH, was performing a flight from the Saint-Benoît-sur-Loire microlight base toward Château-Thierry. During the takeoff roll, after the aircraft had traveled roughly thirty-five meters, it suddenly veered to the right. The pilot attempted to brake, but the aircraft entered a nose-over position and came to rest on its back.
The flight involved two occupants: the pilot and one passenger. The passenger sustained slight injuries, while the Aviasud Engineering Mistral sustained heavy damage.
The investigation
Investigators examined the wreckage of the Aviasud Engineering Mistral to determine the cause of the sudden deviation. The inspection focused on the nose gear assembly, specifically the connection between the gear leg and the front wheel support.
The examination revealed that the nose gear had fractured at the weld joining the gear leg to the wheel support. Analysis of the fracture surface showed that the weld was defective, with an imperfect weld covering more than one-quarter of the total welded surface. The fracture pattern was characteristic of a static failure, indicating the metal had reached its elastic limit under load.
Findings
- The primary cause of the accident was the failure of a mechanical component due to an imperfect weld present since the aircraft's construction.
- The fracture occurred laterally relative to the wheel alignment, suggesting the component failed under loads exceeding its design strength.
- While the exact source of the excessive force could not be definitively identified, photographic evidence from the takeoff roll showed the wheel had become misaligned. It is probable that a wheel orientation not parallel to the aircraft's path generated unusual lateral stresses that triggered the structural failure.