Primary finding
Probable cause
The helicopter flight instructor's delayed remedial action during an autorotation resulting in a loss of control and impact with terrain.
Investigator assessment
Analysis narrative
According to the flight instructor, while performing a simulated, right turn, 180 degree autorotation the helicopter impacted the ground and rolled over. The flight instructor stated that at 200 feet AGL, the low rotor RPM horn sounded, and he and the student pilot "attempted a recovery." The flight instructor reported that after hearing the low rotor RPM horn, but prior to impact, "a loud thumping noise could be heard and a violent shake in the cyclic could be felt." He stated that he chose to level the helicopter before it impacted the terrain and rolled. The helicopter sustained substantial damage to the main rotor system, fuselage and tail boom. The pilot reported that there were no mechanical failures or anomalies prior to flight that would have prevented normal operation.
Source record
Factual narrative
According to the flight instructor, while performing a simulated, right turn, 180 degree autorotation the helicopter impacted the ground and rolled over. The flight instructor stated that at 200 feet AGL, the low rotor RPM horn sounded, and he and the student pilot "attempted a recovery." The flight instructor reported that after hearing the low rotor RPM horn, but prior to impact, "a loud thumping noise could be heard and a violent shake in the cyclic could be felt." He stated that he chose to level the helicopter before it impacted the terrain and rolled. The helicopter sustained substantial damage to the main rotor system, fuselage and tail boom. The pilot reported that there were no mechanical failures or anomalies prior to flight that would have prevented normal operation.