Incident Overview
A certified flight instructor and a student pilot were conducting training in a helicopter. The maneuver being practiced was a 180-degree autorotation with a power recovery to a hover.
Sequence of Events
During the flare, approximately 40 feet above the ground, the helicopter's sink rate increased dramatically. The flight instructor called for a go-around and took corrective action by increasing power, raising the collective, and pushing the cyclic forward. Despite these inputs, the helicopter continued to descend and contacted the runway in a level attitude.
Post-Contact Observations
After the helicopter came to a stop, a vibration was felt. The instructor confirmed that the main rotor blade had struck the tail boom during the event.
Mechanical Status
The instructor reported that there were no mechanical deficiencies with the helicopter prior to or during the flight.