Accident Overview
During an en route flight, a student pilot radioed that the engine was losing power. Another pilot who heard the transmission described the student pilot as sounding panic-stricken. The aircraft subsequently crashed into a small pond surrounded by an open field. Damage to the aircraft indicated it struck the pond in a steep nose-down attitude.
Investigation Findings
Examination of the aircraft did not reveal evidence of mechanical malfunction. Inspectors noted that the left wing surface behind the fuel tank filler neck showed the fuel cap was unfastened and lying on the wing during flight.
Fuel System Examination
A flight test was conducted in a similar aircraft with an unfastened left fuel cap. During that test, the cap moved aft and was held by its chain, and fuel siphoned from the left fuel tank. Fuel performance calculations indicated the aircraft would have used up to 13 gallons during the flight. The aircraft had a total fuel capacity of 30 gallons, with 15 gallons per tank.