Hard Landing During Autorotation Training Results in Tail Boom Damage

Incident Overview

During an instructional flight focused on autorotation training, the flight instructor reported that the helicopter was configured for a maximum glide. He set the rotor rpm between 93 and 94 percent. He applied aft cyclic to reduce the rate of descent and regain rotor rpm. The rate of descent did not decrease, prompting him to increase the throttle and level the helicopter as it neared the ground. The helicopter landed hard, bounced once, and came to rest. The tail boom sustained substantial damage.

Pilot's Operating Manual Caution

The helicopter's Pilot's Operating Manual includes a caution regarding autorotation below 500 feet above ground level. It advises increasing rotor rpm to a minimum of 97 percent under such conditions.

Post-Accident Observations

The flight instructor reported that there were no preimpact mechanical malfunctions or failures with the helicopter or engine that would have precluded normal operation.