Incident Details
During an instructional flight, the helicopter's engine suddenly lost power while in initial climb. The certified flight instructor (CFI) took control of the helicopter and executed an autorotation, resulting in a hard touchdown in a gravel pit. After securing the helicopter, the CFI inspected the throttle linkage.
Inspection Findings
The CFI reported that something appeared disconnected behind the firewall. He noted that when rotating the throttle from full open to full close, the push/pull tube that connects to the carburetor did not move. A subsequent examination of the helicopter's throttle spring assembly was conducted.
Maintenance Error
Examination revealed that on a previous occasion, improper maintenance had been performed. The helicopter's maintenance records did not reflect any maintenance in this area. The inspection determined that the upper rod end bearing was disconnected from the lower portion of the rod because it had not been safety wired as required. This maintenance error resulted in a total loss of throttle control.