Accident Description
During a local instructional flight, the helicopter impacted the ground at a high rate of descent. The wreckage and ground scars indicated a collision in a level upright attitude, with the helicopter subsequently rolling onto its right side.
Witness Observations
Several minutes before the accident, a witness on a farm approximately 3 miles from the accident site heard and observed the helicopter performing maneuvers consistent with multiple practice autorotations followed by power recoveries. The helicopter then departed in the direction of the airport. Witnesses near the accident site observed the helicopter in level controlled flight at about 500 feet above ground level, also flying toward the airport. They then saw the helicopter's nose drop, followed by a dive toward the ground, after which it disappeared behind a tree line. These witnesses reported hearing normal engine sounds during the event.
Wreckage Examination
Examination of the wreckage revealed that the main rotor blades had flexed downward and sliced into the tail boom. The blade and drive train evidence was consistent with a high rotational rate and a driven energy state, indicating engine rotation and power production at the time of impact.
Airframe and Engine Inspection
An inspection of the airframe and engine found no preimpact anomalies that would have precluded normal operation or functionality of the control system.