What happened
On 6 March 2024, a Robin DR400-160, registration F-GYAC, was prepared for a local flight at Nantes-Atlantique airport. After the pilot and a passenger boarded, the pilot attempted to start the engine. Following three unsuccessful attempts using the starter motor, the pilot moved the battery switch to the OFF position and turned the magneto selector key to what he believed was the OFF position, though the key remained in the ignition.
After engaging the parking brake, the pilot exited the aircraft to manually rotate the propeller. As the propeller passed the compression point, the engine unexpectedly ignited. The aircraft began moving forward across a grass strip toward a parked Airbus A320. The pilot, attempting to prevent a collision, climbed onto the left wing and eventually managed to partially enter the cockpit, using his hand to depress the rudder pedal to steer the aircraft away from the commercial airliner. He eventually regained full control and returned the aircraft to the flying club.
The investigation
The investigation examined the aircraft's electrical and mechanical state following the event. A maintenance check revealed that the battery voltage had dropped to approximately 8V following the repeated starting attempts. The investigation also reviewed the pilot's actions regarding the engine shutdown and the aircraft's configuration. It was determined that while the pilot believed the magnetos were grounded, the key had not been removed, and the throttle was not at idle, with the mixture set to full rich.
Findings
- The primary cause of the unexpected engine start was the failure to follow an appropriate checklist or shutdown procedure when exiting the aircraft.
- The pilot did not fully apply the parking brake before exiting.
- The magneto selector key was left in the ignition, and the engine was not properly secured (throttle not at idle, mixture not adjusted).
- Repeated attempts to start the engine had significantly depleted the battery voltage, making subsequent starts unreliable.