What happened
Prior to departure from his home airport, the pilot replenished the main fuel tanks. The aircraft departed with both fuel selectors set to the "Main" position. After approximately two hours of flight, while descending from 6,000 feet to 4,000 feet, the engine experienced several minor power surges and hiccups before suffering a total loss of power.
The pilot established an appropriate glide speed and attempted a straight-in approach for runway 23 at the home airport. During the descent, the pilot performed emergency checklist procedures, which included verifying the electric fuel pump was active and cycling the fuel selectors through all available tanks. Despite these efforts, the engine could not be restarted. The aircraft continued its glide but impacted small trees approximately 2,500 to 3,000 feet before reaching the runway.
The investigation
An examination of the engine found no mechanical malfunctions that occurred prior to the impact. Fuel was present in all tanks and was found to be flowing from the selector valve through the fuel servo to the flow divider. Additionally, the electric fuel pump operated continuously when power was applied.
Investigators noted that the throttle idle adjustment bushing was missing from the engine; however, it could not be determined if this component separated during the flight or during the impact with the trees. A subsequent flow test of both the fuel servo and the flow divider showed no discrepancies capable of causing a complete loss of engine power.