Accident Summary
While being hovered at low altitude and slow speed around a water trough, the helicopter experienced a loss of directional control. The pilot initiated an autorotation to the ground. Upon touchdown, the right skid buckled and the tailrotor gearbox separated after striking an ant hill.
Initial Reports and Examination
The pilot originally reported that one of the tailrotor blades had separated, and the fracture surface appeared to indicate fatigue. However, a metallurgical examination of the failed components determined that all fractures were consistent with overload failure, not fatigue.
Environmental Factors
The reported wind conditions at the time would have been conducive to a loss of tailrotor effectiveness at lower airspeeds, which may have contributed to the loss of directional control during the hover.
Damage
Damage was limited to the right skid (buckled) and the tailrotor gearbox (separated). No other damage items were specified.