Incident Overview
During a flight at 11,000 feet, the pilot observed that the fuel flow gauge was fluctuating and the engine sounded abnormal. In response, he enriched the mixture slightly and activated the auxiliary fuel pump to the low boost setting. The fuel flow then stabilized. However, a short time later, the fuel flow gauge again showed fluctuations and the engine's sound indicated a problem. The pilot then switched the auxiliary fuel pump to the high boost position and leaned the mixture slightly. The engine subsequently operated normally, and he continued to the destination with the auxiliary pump remaining on high boost.
Loss of Power and Landing
On final approach to land, with the auxiliary pump still engaged, the engine lost power. Unable to clear obstructions, the pilot elected to land in a field short of the runway. During the rollout in tall grass, the aircraft struck a mound of dirt and nosed over.
Post-Incident Examination
No preimpact failure was found, and fuel remained in the tanks. The owner's manual for the aircraft notes that fuel vaporization can occur. It recommends that if fuel flow fluctuates above 1 gallon per hour, the auxiliary pump should be set to high and the mixture adjusted. Once fuel flow stabilizes for several minutes, the auxiliary pump may be turned off and the mixture reset.
Editor's Note
The incident highlights the importance of following manufacturer guidance for fuel system management, particularly in conditions conducive to vaporization.