What happened
The flight was originally planned as a training exercise focused on demonstrating emergency procedures. During the sortie, the flight instructor conducted several traffic patterns and approaches to illustrate proper techniques.
During one specific maneuver, the instructor attempted to demonstrate an autorotation. In doing so, he allowed the rotor revolutions per minute (RPM) to deteriorate significantly. As a result of this loss of rotational energy, the helicopter lost lift and subsequently collided with the ground.
The investigation
Post-accident analysis relied heavily on the account provided by the flight instructor. No mechanical failures were cited as contributing factors. The investigation focused on the operational decisions made during the training exercise.