Accident Overview
A traffic watch helicopter, cruising northbound along an interstate at 450 feet above ground level and 85 knots airspeed, experienced a sudden grinding noise. The tail rotor subsequently separated from the aircraft. The helicopter initiated an uncommanded right turn, which was arrested after approximately one-quarter of a turn. The pilot attempted to autorotate into an open field east of the highway, but the aircraft struck a 25-foot tree at the field's edge and crashed.
Post-Accident Examination
Examination of the wreckage revealed that the tail rotor gear box housing, part number 369A5400-607, had failed. A portion of the housing, along with the driven gear, tail rotor blades, and related components, separated from the helicopter in flight. The missing parts sank in a lake about half a mile from the crash site and were not recovered. The remaining section of the gear box was examined by the NTSB laboratory, which determined that the failure was due to overload with no evidence of fatigue or corrosion.
Witness Observations
A witness reported seeing two objects fall from the helicopter. One object was white and resembled a bird, likely a seagull. The other object appeared to be a stick or a piece of wood resembling a 2x4.