The flight instructor and student pilot performed a straight-in autorotation with a power recovery maneuver to simulate landing the helicopter with a complete power loss. As the instructor demonstrated the autorotation, during the glide, the instructor realized that he was going to overshoot the landing spot, and forced the helicopter out of trim, which enabled the helicopter to increase its decent rate. As the helicopter crossed 100 ft above ground level, the instructor trimmed the helicopter and noted that the helicopter’s airspeed and rotor RPMs were about 50 knots and 95%, respectively. The instructor initiated a flare and the helicopter started to sink. He then rolled the engine throttle UP and raised the collective, but the helicopter landed hard. Subsequently, the main rotor struck the tailboom, which sustained substantial damage. The flight instructor reported no mechanical failures or anomalies that would have precluded normal operation.