What happened
During flight operations, the aircraft's engine lost power, prompting the pilot to execute a forced landing in a nearby plowed field. The terrain was soft, which caused the aircraft to flip over upon impact. The pilot reported that the engine failure was due to fuel starvation. One fuel tank had run dry while the other remained full. Before takeoff, the pilot checked both sight gauges and noted they appeared identical. He stated that when a tank is either full or empty, the fuel level cannot be seen.
The investigation
The investigation focused on the cause of the engine power loss and the subsequent landing. The pilot's account indicated that he had visually inspected the fuel levels prior to departure. However, the design of the sight gauges made it impossible to distinguish between a full tank and an empty one based on visual inspection alone.
Findings
The primary factor in this accident was fuel starvation caused by one tank running dry while the other remained full. The pilot's pre-flight inspection failed to identify the actual fuel quantity because the sight gauges did not provide a clear indication when the tanks were either full or empty. This limitation led to an incorrect assessment of available fuel. The aircraft sustained significant damage due to the flipped over position after landing on soft terrain.
Safety message
Pilots should be aware that certain aircraft fuel sight gauges may not accurately indicate fuel levels when tanks are full or empty. Pre-flight checks must include methods other than visual inspection of these gauges to ensure accurate fuel quantity assessment.