Accident Summary
During a local area maintenance test flight, the engine began misfiring shortly after takeoff. The pilot initiated a right turn to return to the airport but inadvertently stalled the airplane. The aircraft nosed down sharply and crashed.
Pilot and Flight Details
The pilot, who held both an airline transport pilot certificate and an airframe and powerplant mechanic certification, was performing a 100-hour inspection at the time of the accident. The fixed-base operator and the registered owner reported that the fuel nozzles had experienced recurring clogging issues.
Engine Examination
Examination of the engine fuel system revealed that the fuel inlet passage was clogged with an unidentified black, sponge-like material. This condition prevented fuel from reaching the fuel injector assembly, resulting in fuel starvation. Additionally, two of the fuel injector nozzle screens were completely obstructed, while the remaining screens were partially obstructed.
Further inspection of the engine disclosed extensive fretting on both crankcase halves and all cylinder bases. However, the examination did not reveal any abnormalities that would have prevented the engine from producing power.
Findings
The engine fuel system obstructions led to fuel starvation, causing the engine to misfire. The pilot's inadvertent stall during the return maneuver resulted in the loss of control and subsequent crash.