What happened
On May 2, 2023, a Bell 47G-2 helicopter, registration F-GANY, was performing agricultural spraying operations near Thouars-sur-Garonne. After completing an initial 15-minute flight rotation, the pilot landed to replenish fuel and whitening products. During this interval, a task specialist added approximately 20 liters of fuel to the tanks while the rotors were still turning.
Following the second takeoff, the aircraft flew for approximately 20 minutes. During the third rotation over a polytunnel, the engine suddenly shut down without warning. The pilot performed a forced landing in a nearby ploughed field. Due to the soft ground, the helicopter's skids sank into the soil, and the aircraft sustained damage during the landing process.
The investigation
The BEA investigation focused on the cause of the engine shutdown and the fuel levels on board. Investigators examined the aircraft's fuel system and performed a re-enactment of the refueling process. During the examination, investigators discovered a significant leak at the left-hand fuel tank bleed valve, even when the valve was in the closed position.
Technical analysis of the valves revealed that while the right-hand valve functioned correctly, the left-hand valve contained debris. When the valve was closed, these impurities prevented the piston from seating properly against the restrictor, allowing fuel to leak at a rate of between 1 and 2 liters per minute.