NTSB Factual Report

On August 2, 2018, about 0930 mountain daylight time, a Bell 47G 3B helicopter, N347BH, experienced an engine power anomaly during attempted landing at Crazy Horse Heliport (0SD9), Custer, South Dakota. On approach, the pilot noticed the RPMs had dropped below normal operating range. The pilot increased throttle but was unable to recover RPMs within normal range and the helicopter descended toward the ground. The pilot executed a forced landing in a grassy area on the side of a highway. The helicopter rolled to the right after landing and sustained substantial damage to the main rotor. The commercial-rated pilot and one passenger were not injured. Another passenger received minor injuries. The airplane was registered to Dakota Rotors and operated by Black Hills Aerial Adventures under the provisions of Title 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed for the flight, and no flight plan was filed.