Accident Overview
The aircraft impacted vertically in a heavily wooded swamp. Evidence indicated that the helicopter struck the ground with a high vertical rate of descent and low rotor RPM.
Investigation Findings
The investigation revealed that the belt drive clutch engagement cable had separated due to abrasion caused by internal contact between the cable and assembly components. The separation of the cable resulted in a disconnect between the engine and the transmission, leading to the loss of rotor drive.
Maintenance Records
A review of the aircraft maintenance records could not determine the exact total time on the cable. However, the records indicated that the cable had last been disassembled and inspected approximately 636.8 hours before the accident.
Service Information Notice
The manufacturer had issued a Service Information Notice on the cable assembly. The notice required an initial inspection within 50 hours and a recurring inspection every 400 hours thereafter, until the unit was replaced with an improved model. The aircraft maintenance records did not indicate compliance with the information notice; however, the operator stated that the inspections were being performed.