What happened
The aircraft was landed wheels-up in an open, muddy field following an in-flight engine failure. According to the pilot's account, the sequence of events began just prior to turning onto the downwind leg of the traffic pattern. At that time, the pilot reduced power and extended the landing gear as part of the standard approach configuration.
Subsequently, the pilot increased the engine RPM and set the mixture control to full rich. Immediately after this adjustment, the engine quit completely. All attempts by the pilot to restart the engine were unsuccessful. With no power available, the pilot retracted the landing gear and proceeded to make a forced landing in the adjacent field.
The investigation
Following the accident, recovery operations were conducted at the site. Before the wings could be removed for transport, thirty-five gallons of fuel were drained from the aircraft's tanks. After the aircraft was recovered, further mechanical testing was performed to determine the cause of the failure. An external fuel tank was connected to the system, and a new propeller was installed.
Upon completion of these repairs, the engine was started and operated successfully. It ran at 1000-1200 RPM without difficulty, indicating that the mechanical components were functional after the incident. The Aviation Training Center director of maintenance reviewed the circumstances and determined that the cause of the engine failure was a fuel vapor lock.