Incident Overview
While conducting a routine night patrol, a police helicopter experienced a mechanical failure when the large clevis pin in the clutch control spring assembly was lost. This caused the spring assembly to separate, disconnecting the powerplant from the rotor system. The pilot immediately initiated an autorotation to manage the descent.
Autorotation Attempt
During the autorotational descent, the terrain below consisted of a ravine with high trees. The pilot was unable to accurately judge the distance between the helicopter and the ground, preventing a successful autorotational landing. The aircraft subsequently came to rest in the ravine amid the trees.
Probable Cause
The probable cause of the incident was the loss of the large clevis pin in the clutch control spring assembly, which led to the disconnection of the powerplant from the rotor system.