Background
A helicopter was being flown for the purpose of allowing the second pilot to acquire the minimum flight hours required to act as pilot-in-command. The owner of the helicopter and the second pilot were practicing autorotations from flight to a power recovery.
Accident Sequence
The owner stated that during the fourth autorotation, the second pilot allowed the rotor rpm to decay and then froze on the controls, preventing the owner from increasing the throttle. The owner was able to level the helicopter; however, it landed hard and the main rotor blades struck and severed the tail boom.
The second pilot reported that at the initiation of the maneuver, the owner rolled the throttle off, and the downwind glide was established. As the second pilot leveled the helicopter and pulled collective, he realized that the engine was not completely back on line. The owner subsequently took over the flight controls and flew the helicopter to the ground.
Pilot Reports
Both pilots reported the need for better verbal commands or stating intentions throughout the maneuver. They indicated that improved communication could have prevented the sequence of events.
Findings
Neither pilot reported a preimpact mechanical malfunction or failure with the helicopter that would have precluded normal operation. No external factors or system anomalies were identified as contributing to the event.