Mcdonnell Douglas Helicopter 600 N608BP accident near San Clemente, California

Probable cause

Failure of the engine’s number two bearing during cruise flight, which resulted in a loss of engine power.

NTSB analysis

During cruise flight the helicopter experienced a loss of engine power. The pilot performed an autorotation, maneuvering the helicopter to avoid obstacles. The helicopter sustained substantial damage after landing hard, semi-submerged in the surf zone of a beach. During the landing sequence, a main rotor blade made contact with the tail boom and the helicopter sustained crush damage to the lower fuselage. Post accident examination of the airframe did not reveal evidence of any failure or malfunction. Examination of the engine revealed a failure of the number two bearing, resulting in a subsequent failure of the engine’s gas generator and power turbine sections. Examination of the bearing revealed signatures consistent with the inner and outer bearing races experiencing misalignment. The misalignment resulted in the associated balls becoming mechanically locked against the ball cage, leading to raceway compromise, heat damage, and bearing failure. As a result of this accident, and other in-service wear issues related to the number two bearing, the engine manufacturer has embarked on a bearing redesign process for this engine series.

Text from the NTSB. Open the NTSB docket for WPR09GA119 for the full record.