Accident Details
The accident occurred during a training flight practicing autorotations. The flight instructor and student were performing a series of autorotations before attempting a 180-degree autorotation. The student initiated a stabilized autorotation from the downwind leg of the traffic pattern. While turning, the student allowed the nose of the helicopter to drop, and the flight instructor instructed the student to correct the attitude by applying aft cyclic. The turn was completed at an altitude between 200 and 250 feet AGL and at a speed of 80 to 85 knots. The flight instructor believed the outcome of the maneuver was uncertain and therefore took control of the helicopter.
The flight instructor began a recovery by raising the nose and increasing throttle and collective to reduce the descent rate. According to the instructor, the rotor RPM decreased and the low rotor RPM horn activated at an altitude between 150 and 100 feet AGL. The helicopter subsequently landed hard and slid off the north side of a taxiway. The forward section of the left skid contacted soft dirt, causing the helicopter to turn left and nose over.
Investigation
A Federal Aviation Administration inspector examined the helicopter and found substantial damage, including the separation of the tail boom assembly, damage to the firewall, the left forward frame, and left skid support structure. The flight instructor reported no mechanical anomalies with the helicopter or its flight control systems.