Accident Overview
The aircraft was discovered floating inverted approximately 1.5 miles from its departure point. The tailboom had separated, and evidence indicated that the main rotor blades had struck the tailboom. The windshield and chin bubble were broken out.
Mechanical Findings
Examination of the engine revealed that an oil pump gear tooth was adhering to the lower chip detector plug. The oil pump had three teeth missing from a gear. There was evidence of a smooth round object passing through the pump and jamming the gear teeth.
Bearing Failure
The ball separator cage for a bearing (MRC P/N 6859435-G) had broken apart, allowing balls to fall out. This caused the gear that drives the fuel control and oil pump to move sideways far enough to become uncoupled from its drive gear. Seven tangs on one-half of the ball separator cage had separated.
Unauthorized Part
The separated bearing was not an authorized type for use in this engine. The engine manufacturer had issued a commercial engine bulletin dated September 30, 1982, calling for all unauthorized bearings to be removed from spare stock and scrapped.