Incident Overview
The pilot of a single-engine airplane reported an engine problem or failure via radio and stated he was going down. Witnesses observed the airplane maneuvering at a low altitude with the propeller not turning. During a turn, the airplane's nose dropped, and it descended into the ground, impacting in a nose-down attitude.
Examination Findings
An examination of the accident site confirmed the nose-down impact attitude. The engine, a WSK 'PZL-Rzeszow' (PZL) Franklin 6A-350-C1R, was inspected. The engine-driven fuel pump had failed; the inlet and outlet valve stems were fractured due to fatigue.
Fuel Pump Details
According to a PZL representative, PZL did not know who manufactured the pump and did not know its characteristics. Further research revealed that the fuel pump was designed for use in a Chevrolet Corvair automobile. The pump manufacturer stated that the pump was intended strictly for automotive applications and not for aviation use. The pump was designed to operate at 5.4 to 6.9 pounds per square inch (psi) static pressure at the outlet when operated at 1,800 rpm. The PZL representative noted that the operating limits for fuel pressure in the 6A-350-C1R engine are 0.5 psi minimum to 8.5 psi maximum. The FAA issued Type Certification Data Sheet No. E9EA for the PZL Franklin 6A-350-C1R engine on December 8, 1994.