Accident Overview
The pilot experienced a loss of engine power and executed a forced landing in an open field. During the landing, the aircraft collided with two fences. An FAA inspector who responded to the site confirmed that fuel was present in the fuel tanks. A visual examination of the engine revealed no obvious mechanical failures.
Engine Examination
Investigators attempted to run the engine but found it would start and then immediately stop. The engine-driven fuel pump was removed for inspection. The mating splines in the drive shaft were observed to be severely worn.
Maintenance History
A review of the engine logbook indicated that a field-overhauled engine and an overhauled fuel pump had been installed approximately one year prior to the accident. An annual inspection was completed at the time of installation. The owner reported 149.38 hours of operation since that annual inspection. The fuel pump had been overhauled by an FAA-approved repair station.
Laboratory Findings
The fuel pump was sent to the Safety Board Materials Laboratory for further examination. A senior metallurgist noted wear and metal flow on the square key portion of the fuel pump shaft. There was no evidence of cracking or wear on the drive gear splined teeth. Manual rotation of the fuel pump achieved only intermittent engagement between the square key and the corresponding slot.
Hardness testing of the gear was conducted. The specification called for 50–52 HRC (Rockwell C-scale). Initial tests showed values below acceptable limits, prompting a Rockwell B-scale test, which yielded an average of 94.5 HRB. After removal of a cadmium coating, further HRC tests gave an average hardness of 40 HRC.
Regulatory Action
The FAA issued a suspected unapproved part notification (UPN No. 2004-00053) regarding the overhaul/repair procedure of the accident fuel pump. Teledyne Continental Motors subsequently released Service Instruction Letter SIL06-2, notifying owners and operators of the FAA's notification.