Sequence of Events
The pilot reported that he was returning to the airport and had entered the base leg of the traffic pattern when a partial loss of engine power occurred. Upon activating the boost pump, engine power was restored for a short duration. However, the pilot was unable to maintain sufficient power for flight. An emergency landing was performed in an open field.
According to the pilot, after the initial power loss on base leg, he restarted the engine by using the fuel boost pump. Once the engine started, he turned the boost pump switch off, and the engine immediately lost power again. The pilot indicated that this start process was repeated several times with similar results each time.
Post-Crash Examination
A post-crash examination of the engine revealed no evidence of mechanical malfunction or failure.
Pilot Experience and Procedures
The pilot had 2.5 hours of flight time in this make and model of aircraft. The pilot's handbook (flight manual) states that the boost pump should be on for an air start and left on if the fuel pump is suspected of failure or loss of fuel pressure with the boost pump off. The pilot's actions of turning off the boost pump after each restart were contrary to the manual's guidance, but the investigation did not assign a cause for the power loss.