Incident Overview
During a hover to pick up an external load, the pilot of a helicopter experienced a loss of rotor RPM. In response, the pilot executed a hovering autorotation. The aircraft subsequently impacted the ground, resulting in substantial damage.
Component Examination
Post-incident examination of the overrunning clutch assembly revealed a fatigue failure. Investigators found that when the clutch was last overhauled, the previous operating time was listed as unknown. Records indicate that the clutch was installed on the accident aircraft and operated for 175 hours beyond its mandatory replacement interval.
Mechanical Details
The overrunning clutch assembly is a critical component that allows the rotor to continue spinning if the engine fails or loses power. Fatigue failure of this assembly compromised its function, contributing to the loss of rotor RPM experienced by the pilot.
Maintenance Context
The fact that the clutch operated past its mandatory replacement time points to a maintenance discrepancy. Without a known previous operating time at overhaul, the component's lifecycle could not be accurately tracked, leading to extended service beyond safe limits.