What happened
On 06 August 2021, a Waco YMF5, registration F-GYMF, was conducting a ferry flight from Dijon-Darois to Blois-Le Breuil. While cruising at approximately 1,000 feet over a forested area near Yvoy-le-Marron, the engine suddenly shut down without warning.
The pilot, attempting to manage the emergency, identified a clearing and turned the aircraft to reach it. During the descent, the pilot attempted several engine restart procedures from memory. While reviewing the emergency checklist, the pilot realized the fuel tank selection had not been verified. However, at an altitude of approximately 400 feet, the pilot determined there was insufficient time to continue restart attempts and focused on maintaining the best glide speed for a forced landing. The aircraft struck tree branches at the edge of the clearing before coming to a stop. The impact resulted in the pilot being severely injured and the aeroplane being destroyed.
The investigation
The investigation focused on the engine failure and the state of the fuel system. Investigators found that while the right-hand fuel valve was in the open position, the left-hand fuel valve was found in the closed position. The right-hand tank contained no fuel, whereas the left-hand tank was heavily damaged but had been the source of the fuel depletion issue.
It was established that during recent annual maintenance, technicians had closed the left-hand fuel valve to drain the right-hand tank. The investigation also noted that the aircraft was not equipped with a fixed emergency locator transmitter (ELT), and the pilot had not activated the transponder or contacted flight information services during the emergency.
Findings
- The engine shutdown was caused by fuel exhaustion in the right-hand tank while the left-hand tank remained full.
- The pilot's pre-flight checks focused on the right-hand fuel system due to recent maintenance, leading to an oversight of the left-hand valve position.
- A habit of performing checklists from memory rather than using the physical checklist reduced the pilot's vigilance regarding fuel selector positions.
- The decision to fly at a relatively low altitude over a heavily wooded area limited the options for a safe forced landing.