Incident Overview
A helicopter experienced a loss of tail rotor authority while in cruise flight. The pilot initiated an autorotational landing procedure in response to the emergency. However, during the approach, the pilot lost all control of the aircraft, resulting in an accident.
Post-Accident Findings
An inspection of the tail rotor gearbox following the accident revealed a failure of the 90-degree gearbox. Examination of the helicopter's maintenance logbooks indicated that the gearbox had undergone an overhaul 195 flight hours prior to the accident. No other maintenance actions on the gearbox were noted in the logbooks. The helicopter had also received an inspection one month before the accident, and it had accumulated approximately 33 flight hours since that inspection.
Mechanical Background
The 90-degree gearbox is a critical component that transmits power from the engine to the tail rotor, enabling anti-torque control. A failure of this gearbox can result in a loss of tail rotor effectiveness, which is a serious flight control issue for helicopters.
Operational Context
The accident occurred during a routine cruise phase of flight. The pilot's decision to perform an autorotational landing was appropriate given the loss of tail rotor authority. However, as the approach progressed, the loss of control suggests that the failure may have progressed or that other factors affected handling.
No information was provided regarding the helicopter's type, registration, operator, location, date, time of day, weather conditions, or any involvement of air traffic control. Additionally, no details about occupants, injuries, or damage extent were included in the source.