What happened
On Saturday, August 8, at approximately 19:00, a Weedhopper ultralight, identified as 74-GQ, was performing a local flight near Chambéry Aix-les-Bains. The aircraft had previously completed three short flights earlier that day. During the initial climb, at an altitude of approximately 20 meters above the ground, the engine suddenly stopped. In an attempt to maintain airspeed and execute an emergency landing, the pilot pushed the nose down; however, the aircraft struck the ground violently on its nose wheel.
The accident resulted in two serious injuries and the total destruction of the aircraft.
The investigation
The investigation focused on the sudden loss of engine power during the climb. Examination of the engine revealed no mechanical anomalies or malfunctions. However, a detailed inspection of the fuel system identified that the vent for the right fuel tank was obstructed because the vent screw had been tightened completely. This closed position caused a progressive vacuum to form within the right tank, which eventually interrupted the fuel supply to the engine. Although the pilot stated that the tank vents had been checked prior to the flight, the closed position of the vent screw led to the fuel starvation.
Findings
- The primary cause of the engine failure was fuel starvation caused by the obstruction of the right fuel tank vent.
- The vent screw was found in a fully closed position, creating a vacuum in the tank.
- No other mechanical issues were found within the engine assembly.