Accident Summary
On July 2, 2018, at approximately 1445 central daylight time, a Robinson Helicopter Company R-22 Beta II (registration N830J) sustained substantial damage during an accident near Georgetown, Texas. The flight instructor and the commercial pilot aboard were not injured. The helicopter was being operated under Title 14 Code of Federal Regulations Part 91 as an instructional flight.
Flight Details
The purpose of the local flight was to provide flight instructor training to the commercial pilot. According to the flight instructor, the helicopter had an adequate amount of fuel for the flight. The aircraft was equipped with a carburetor heat assist device, which correlates carburetor heat application with collective pitch changes to reduce pilot workload.
Accident Sequence
During the last traffic pattern iteration, while on the downwind leg at about 500 ft above ground level (agl) and 70 knots, the flight instructor reported hearing the low rotor revolutions per minute (rpm) horn activate. He took over the flight controls, immediately reduced the collective, and applied throttle. The low rotor rpm horn ceased and the light extinguished, with engine and rotor rpm at about 97%. As the instructor began the base leg turn, the low rotor rpm horn sounded again. Observing the tachometer, he noticed engine and rotor rpm were decaying. Assessing that the engine could not maintain safe rotor rpm, he entered an autorotation.
The instructor scanned the instruments and observed airspeed at about 55 knots. He reported hearing no noise from the engine and concluded it had ceased producing power. After entering the autorotation flare, he focused on maintaining rotor rpm and maneuvering to a landing area. At about 35 ft agl, he began the flare to reduce forward airspeed and rate of descent. The helicopter touched down in the yard of a private residence with slight forward airspeed; the skids struck a concrete driveway.
The impact caused the helicopter to pitch nose-low with the tail elevated, accompanied by a right yaw. Both tail rotor blades struck the ground and separated near mid-span. The tail boom and vertical stabilizer sustained substantial damage; the tail rotor stinger and skids received minor damage. After the helicopter came to rest, the engine was at idle, and the instructor performed an emergency shutdown. Both occupants exited without further incident.
Postaccident Findings
A postaccident examination of the airframe and engine revealed no preimpact mechanical malfunctions or failures that would have precluded normal operation. Maintenance records showed no uncorrected discrepancies. The operator reported that the pilot receiving instruction may have inadvertently gripped and reduced the throttle during the flight. This pilot had a history of being "heavy" or "rough" on flight controls, as observed during a postaccident flight. The temperature and dewpoint at the time were conducive to carburetor icing for glide and cruise power, as per FAA Special Airworthiness Information Bulletin CE-09-35.