What happened
The aircraft was engaged in a low-altitude powerline patrol when it descended and collided with upslope terrain.
The investigation
Investigators examined the aircraft's clutch spring assembly and discovered that the assembly retainer end had fractured and separated. The investigation found that the retainer wall was severely worn at the point where the separation occurred. This specific assembly is responsible for engaging the belt drive system, which transmits engine power to the main transmission.
The helicopter had accumulated more than 11,000 hours of total time. Maintenance records indicated that the assembly had been inspected approximately one month prior during a 100-hour inspection. Additionally, a review of the maintenance history showed that this assembly had no previous replacement recorded.