The flight instructor reported that during the instructional flight, while conducting autorotation training in a maximum glide configuration, he set the rotor rpm between 93-94%. Aft cyclic was applied to slow down the rate of descent and to regain rpms. The rate of descent did not slow so the throttle was increased, and the helicopter was leveled as it approached the ground. The helicopter subsequently landed hard and bounced once before it came to rest. The tail boom was substantially damaged.

A caution in the helicopter's Pilot's Operating Manual states in part to "increase rotor RPM to 97% minimum when autorotating below 500 ft above ground level."

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