What happened
On October 16, 1999, at approximately 14:30, an Air Création Twin GTE 582 ultralight, identified as 25-LB, was involved in a fatal accident at AD Til Chatel. Following refueling, the aircraft was parked near the fuel pumps. The pilot started the engine and allowed it to idle while standing beside the aircraft. As the pilot attempted to board the aircraft from the right side, the engine RPM increased significantly.
Before the pilot could be properly seated or secured, the aircraft began to move. At the time of the movement, the pilot's seatbelt was unfastened, and the control bar remained secured to the front of the chassis by an elastic strap. The ultralight proceeded to take off under these unstable conditions, reaching an altitude of approximately 100 meters. The flight path became erratic, performing S-turns before entering a steep left-hand turn. The aircraft subsequently struck the ground in a nose-down attitude, approximately 300 meters from the departure site, resulting in the death of the pilot and the destruction of the aircraft.
The investigation
The investigation focused on the sequence of events leading to the unintended movement and takeoff. Investigators examined the aircraft's configuration and the pilot's actions during boarding. While the investigation could not confirm if the parking brake had been engaged, no wheel chocks were found near the aircraft's starting position.
Technical analysis of the aircraft's design revealed that when the control bar is attached to the front of the chassis, the resulting wing position is sufficient to induce a short takeoff and a climb once the engine reaches a higher power setting.