What happened
On May 29, 2005, at approximately 17:15, a Cosmos Bidulm ultralight, identified as 57-IQ, was undergoing engine start procedures at the Jouy-sous-les-Côtes airfield. The pilot, who was awaiting an instructor for a scheduled training flight, attempted to start the engine while parked on the apron.
Following five start attempts, the engine successfully ignited. However, as the pilot was in the process of sitting down, the engine RPM increased suddenly, causing the aircraft to move forward unexpectedly. The pilot attempted to grab the control bar but was unable to reach the master kill switch located under the seat. The aircraft began a right-hand turn at an altitude of roughly ten meters. An instructor flying nearby observed the aircraft performing a high-banked 360-degree circle at low altitude. The aircraft eventually came to rest approximately fifty meters from its original position, where the pilot was found with serious injuries caused by contact with the propeller.
The investigation
The investigation focused on the configuration of the aircraft and the pilot's pre-start actions. Investigators found that the power control lever, located on the left side of the seat, was set to full throttle. Notably, the starter lever, which is positioned similarly to the throttle, was set to the OFF position.
It was determined that the aircraft lacked an electric starter, requiring the pilot to manually pull a starting handle located above the seat back. The standard operating procedure required the seatbelts to be fastened and the control bar to be attached to the chassis compression bar. In this configuration, the wing was positioned in a high pitch-up attitude, which rendered the front wheel brake ineffective against a sudden surge to full power.
Findings
- The pilot failed to verify the position of the manual power control lever on the left side of the seat before attempting the engine start.
- Insufficient pre-start checks regarding the throttle position led to the unintended surge.
- The aircraft's configuration (wing pitch-up) prevented the front wheel brake from controlling the aircraft once the engine reached high RPM.
- The pilot was not wearing his seatbelt at the time of the accident, as the belts were found secured to the seats.