What happened
On May 28, 2006, a Robin DR 400-140 B, registration F-GLDK, was conducting a flight from La Mole to Moulins with a pilot and three passengers. During the cruise phase, the pilot noted that the fuel gauge indicated approximately 35 liters remaining. Approximately 15 nautical miles from Roanne, a red low-fuel warning light illuminated. Five minutes later, the engine began to sputter. The pilot activated the electric fuel pump and performed a forced landing in a field near Saint-Léger-sur-Roanne. During the landing roll, the aircraft struck a barbed-wire fence, resulting in damage to the propeller and wing.
The investigation
The investigation focused on the fuel depletion and the accuracy of the cockpit instrumentation. Upon inspection on the ground, the fuel tank was found to be empty. Investigators examined the fuel gauge and discovered that one of the two rheostat blades was bent, causing the gauge to provide erroneous readings. The investigation also determined that the low-fuel warning light only activated when only 5.8 liters of fuel remained in the tank.
Furthermore, the investigation reviewed the pilot's fuel planning. The pilot had calculated his fuel consumption based on a rate of 36 liters per hour, derived from a previous flight and adjusted for wind. However, this calculation was based on performance data for an aircraft equipped with a different propeller than the one installed on F-GLDK. Additionally, the aircraft's takeoff weight was near the maximum allowable limit, and the center of gravity was at the edge of the certified range.