What happened
On May 22, 1999, a Socata TB 10, registration F-GCOF, was performing a cross-country flight when the engine began to sputter. The incident occurred at approximately 18:00 local time during the climb phase, at an altitude of roughly 1,900 feet. After noticing engine roughness, the pilot attempted to stabilize the engine by adjusting the throttle, but the power loss could not be corrected. Consequently, the pilot shut down the engine and performed an emergency landing in a field near Creux-de la Thine.
The investigation
The investigation focused on the fuel management and the state of the aircraft's fuel system following the landing. Upon inspection, the left fuel tank was found to be empty, while the right tank contained 60 liters of fuel. At the time of the incident, the fuel selector was set to the right tank. However, the fuel gauges were found to be malfunctioning; the left gauge indicated a half-full tank, while the right gauge indicated a full tank. These gauges were subsequently replaced.
Evidence showed that during the previous leg of the flight, from Lyon Bron to Saint-Rambert-d'Albon, the pilot had operated the aircraft using the left tank, which had initially shown a 3/4 level. Before the final departure from Saint-Rambert-d'Albon, the pilot switched the selector to the right tank. The investigation also noted that the pilot had failed to perform a visual fuel level check prior to the initial departure from Lyon Bron, as required by the flight manual.
Findings
- The primary cause of the engine failure was fuel exhaustion in the left tank.
- The pilot's pre-flight preparation was insufficient, specifically regarding the failure to visually verify fuel levels.
- Inappropriate fuel management contributed to the event, as the pilot continued operations without confirming the actual contents of the tanks.
- The aircraft's fuel gauges were defective, providing misleading information to the crew.