Flight Details
The flight was intended to view a lake and its surroundings, located 10 miles from the departure airport. Approximately 30 minutes into the flight, the pilot experienced a loss of fuel pressure followed by rough engine operation. Believing the engine-driven fuel pump had failed, the pilot engaged the electric boost pump, which restored fuel pressure and normal engine operation. The pilot then decided to return to the airport for a precautionary landing.
Engine Power Loss
During the return, the fuel pressure gauge began to fluctuate, and the engine again ran rough before losing power entirely. The pilot attempted an in-flight engine restart using the emergency checklist but was unsuccessful. Subsequently, the airplane was ditched in the lake.
Post-Accident Inspection
No discrepancies were noted with the aircraft prior to the loss of power. Inspection of the fuel system revealed no foreign debris. A functional check of the electric boost pump showed no fuel flow output; during the test, the pump shorted out. Both the engine-driven fuel pump and the electric boost pump were removed for further examination.
Fuel Pump Testing
Two functional tests were conducted on the engine-driven fuel pump. The first test, performed in its as-received condition, found the adjusting nut loose and fuel flow consistently low, though some output was observed. After readjusting the nut to overhaul specifications, a second test showed fuel flow within normal limits.
Teardown of the electric boost pump revealed loose bearings that allowed the pump vanes to rub against the pump throat, reducing fuel flow through the system.