What happened
A certified flight instructor was performing a standard practice autorotation when the aircraft's airspeed dropped significantly. The pilot initially noted that the rotor was in the green, the airspeed was 55 KIAS, and the aircraft was in trim. However, at an altitude of approximately 50 to 100 feet AGL, just before the intended deceleration phase, the airspeed bled down to about 20 KIAS, accompanied by a high rate of descent.
The pilot attempted to execute a power recovery, but the aircraft continued its descent and struck the ground with significant force. During the impact, the tail rotor separated from the aircraft. The momentum caused the aircraft to bounce back into the air, after which it landed hard a second time and subsequently rolled over.