Incident Overview
A Hughes 369D helicopter was returning to a load pickup point when the pilot sensed and heard a vibration that seemed to originate from the tail rotor area. In response, the pilot reduced power and initiated an autorotation.
Sequence of Events
During the autorotation, as the pilot increased power and collective to maneuver for the flare, two loud bangs were heard from the tail rotor area. Immediately thereafter, the airframe began an uncontrolled rotation. The pilot attempted to apply full up collective just before impact, but the helicopter struck the terrain with considerable force.
Aircraft Information
The helicopter involved was a Hughes 369D. No registration information was provided in the source.
Investigation
The investigation focused on the tail rotor area vibration and subsequent bangs. No probable cause was stated in the source.