What happened
On July 2, 2001, an ultralight aircraft, identified as 59-TL, departed from the Sauvian airfield to perform local circuits. Shortly after takeoff, while climbing to an altitude of approximately 400 feet, the Rotax 912 engine began to misfire. The pilot attempted to mitigate the issue by switching to the alternative fuel tank and testing the dual ignition circuits, but the engine failure persisted.
In response to the loss of power, the pilot executed an emergency landing in a nearby field. Prior to touchdown, the pilot shut off the electrical systems and the fuel supply. During the landing roll, the aircraft veered into a vineyard and performed a nose-over.
The investigation
The investigation focused on the engine's performance and the fuel quality. Upon inspection of the two carburetors, investigators discovered a white emulsion and traces of water within the float bowls. Subsequent draining of the fuel tanks revealed that approximately two liters of water were present in the tanks.
It was determined that the aircraft had been refueled using gasoline from a jerrycan. This fuel had been drained from the tanks of another aircraft undergoing repairs. Although the pilot had performed a fuel drain procedure on the aircraft's tanks and carburetors after refueling, the inspection had occurred too soon after the refueling process to allow any settled water to be detected.