What happened
During a training flight, a student pilot was conducting a practice auto rotation maneuver. As the aircraft approached the ground and the pilot initiated the landing flare, he applied engine power to transition out of the descent. The engine failed to respond to the throttle input, leaving the aircraft unable to arrest its sink rate with engine power.
Faced with this situation, the pilot executed a full auto rotation to maintain rotor RPM for a controlled touchdown. However, the timing of his collective pitch adjustment was delayed. He applied the collective too late in the flare sequence to cushion the landing effectively. Consequently, the helicopter impacted the ground with excessive vertical speed, causing one of the main rotor blades to strike and damage the tailboom structure.
The investigation
Following the incident, investigators examined the helicopter to determine if mechanical issues contributed to the event. A thorough inspection of the powerplant revealed no evidence of mechanical malfunction or failure. The engine and associated systems appeared to be functioning normally prior to the flare phase.