Event Overview
A pilot conducted a maintenance test flight to verify control systems including collective pitch position, throttle positioning, and rpm correlation control. During entry into an autorotation, the helicopter's rotor rpm was lower than intended. The pilot applied collective pitch correction, which caused the correlator to over-respond, resulting in an rpm overspeed. The pilot then closed the throttle and increased collective, but the rpm subsequently decreased. The pilot was forced to complete the autorotation, landing on rough terrain.
Maneuver and Touchdown
To eliminate forward speed at touchdown and mitigate the risk of a rollover, the pilot anticipated a hard flare. Just before touchdown, the tail rotor struck the ground. The impact caused the tail rotor gearbox to separate from the tail boom. The helicopter then yawed approximately 150 degrees to the right. The pilot managed to level the helicopter, arrest the yaw, and land without further incident.
Aftermath
No injuries were reported. The helicopter sustained damage to the tail rotor and gearbox assembly. The event highlights the importance of precise rpm management during autorotative maneuvers.