Accident Overview
A pilot and a certified flight instructor were conducting annual refresher training in a helicopter. The accident occurred during a practice autorotation to runway 18. According to the pilot, the helicopter descended below a nearby tree line and "dropped vertically." The descent was so rapid that the pilot was unable to arrest the rate, resulting in a hard landing.
Wind Conditions
The pilot reported the wind at the time of the accident was from 230 degrees at 10 knots, with gusts reaching 19 knots. As the helicopter descended below treetop level, the pilot stated, "…we lost all lift and wind advantage…"
Damage
The hard landing caused a fractured tail boom.
Mechanical Status
The pilots reported no mechanical malfunctions or failures that would have precluded normal operation.
Pilot Reports
The pilot provided the account of the event, indicating that the helicopter's descent below the tree line led to a loss of lift and an inability to control the rate of descent.