Narrative
During a training flight, the aircraft crashed while attempting a practice autorotation after power was applied to effect a recovery. The certified flight instructor (CFI) observed that the student was going to overshoot the intended landing point and instructed the student to make a power recovery at 100 feet above ground level (AGL). As the power recovery was initiated, the aircraft shuddered and entered a high sink rate. By the time the CFI took control of the aircraft, the rotor rpm was below the proper range and decaying, while the engine rpm was near zero. The CFI reported that he then "bottomed" the collective and opened the throttle, but the engine did not respond to his inputs. Despite the CFI's efforts to regain control, the aircraft struck the ground in a tail-low attitude and yawed to the left. After sliding approximately 20 feet, the aircraft rolled over.
Post-Crash Examination
Following the accident, the Federal Aviation Administration (FAA) examined the engine. The engine started and ran normally, with proper magneto operation and a smooth idle at 1300 to 1350 rpm. When the engine was manually reduced to 500-600 rpm, the low side cushion returned the engine to normal idle upon throttle release. The inspection revealed no evidence of an engine malfunction.