What happened
During a training flight, a student pilot initiated a planned power-recovery 180-degree autorotation toward a plowed field. As the student attempted to recover using engine power approximately 20 to 50 feet above the ground, the flight instructor observed that the engine RPM needle was not increasing to match the rotor RPM.
The instructor attempted to apply maximum throttle, but found the throttle would not move. While the student pilot reported that the throttle was stuck, the instructor noted that the throttle appeared to be stuck because it was already in the fully open position. The engine was not running when the instructor took control of the aircraft.
During the maneuver, the helicopter contacted the ground and the right skid dug into the earth, causing the aircraft to roll over and come to rest on its right side. There were no injuries reported.
The investigation
Investigators examined the engine and the airframe following the accident. No mechanical anomalies were identified in either the engine or the airframe components.