Accident Overview
During cruise flight, ground witnesses observed a helicopter perform two violent roll maneuvers. The aircraft subsequently experienced an in-flight breakup, with wreckage scattered over an area of approximately 10 acres.
Investigation Findings
Examination of the wreckage revealed that the collective idler link and retaining pin assembly were missing. The lower attaching stud of the idler link showed evidence of failure: the stud was bent in the direction opposite to the direction of rotation, and sheared nut threads and cotter pin remains were found in the stud threads and cotter pin hole, respectively. The H-shaped idler lever, which connects the upper end of the idler link to the swashplate drive collar, was found attached to the collar and showed no evidence of distress. Investigators could not determine why the retaining pin connecting the collective idler link to the idler lever separated.
Conclusion
The reason for the separation of the retaining pin could not be determined.