What happened
On April 18, 2007, a Zenair STOL CH 701 ultralight, identified as 83-ACC, was conducting a local flight near Fayence, France. The pilot, who had recently acquired the aircraft, was performing circuit patterns to familiarize himself with the machine and to verify fuel consumption and gauge accuracy. During the pre-flight inspection, the pilot noted that the left tank was half full while the right tank was nearly empty, but determined the total fuel onboard was sufficient for the intended flight.
While performing the second circuit in a downwind pattern, the engine lost power. Unable to reach the runway at the Tourettes aerodrome, the pilot was forced to perform an emergency landing in a recently plowed field. The impact caused the nose gear to collapse, resulting in the aircraft flipping onto its back. The aircraft was heavily damaged, though no injuries were reported.
The investigation
Investigators examined the wreckage and the fuel system configuration. They confirmed that the left tank still contained fuel, while the right tank was empty. The fuel selector switch, located on the right side of the cockpit, was found in the LEFT position. The pilot stated he had not moved the selector since engine start.
Further inspection of the selector plate revealed that the letters "D" (for Droite/Right) and "G" (for Gauche/Left) had been hand-painted onto the plate following a modification. The letters were poorly positioned; specifically, the selector lever obscured these painted markings when a tank was selected, making it difficult to verify the active fuel source.