On September 25, 1992, a Hughes 269C (registration N9609F) operated by Helicopters, Inc. was involved in an aviation accident near East Bernstadt, KY. Investigators recorded the probable cause as: INADEQUATE MAINTENANCE INSPECTION INVOLVING FAILURE TO DETECT WEAR OF THE CLUTCH SPRING ASSEMBLY, RESULTING IN THE UNCOUPLING OF ENGINE POWER TO THE MAIN TRANSMISSION. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.
A helicopter on a low-altitude powerline patrol descended and collided with upsloping terrain. Investigation found a fractured clutch spring assembly with a separated retainer end and severe wear at the separation point.
Incident Overview
A helicopter conducting a low-altitude powerline patrol mission descended and subsequently collided with upsloping terrain. The event resulted in damage to the aircraft.
Investigation Findings
Post-accident examination revealed that the clutch spring assembly was fractured. The fracture involved the assembly retainer end, which had separated from the main assembly. The retainer wall exhibited severe wear at the location where the separation occurred.
Component Function
The clutch spring assembly is designed to engage the belt drive system. This system transmits engine power to the main transmission, enabling rotor operation.
Maintenance History
The helicopter had accumulated over 11,000 total flight hours prior to the incident. The most recent inspection of the clutch spring assembly took place approximately one month before the accident during a scheduled 100-hour inspection. A review of maintenance records indicated that the assembly had never been replaced previously.