What Happened
On 2 January 2022, a Robinson Helicopter Company R22 Beta II helicopter, registration ZK-HEQ, was used to transfer two passengers from Karamea to a remote landing spot in Kahurangi National Park for hunting. Shortly after dropping off the second passenger and beginning the return flight to Karamea, the pilot experienced a vibration and an associated noise. The pilot considered options and elected to continue the flight. During the landing sequence at Karamea, the helicopter broke up in the air and struck the ground. The helicopter was destroyed, and the pilot, the sole occupant, was seriously injured.
Why It Happened
The Transport Accident Investigation Commission (the Commission) determined that the helicopter very likely experienced a rotor overspeed, where the drivetrain exceeded the manufacturer's revolutions per minute speed limit. This rotor overspeed very likely caused the tail rotor drive shaft to deform. During landing, increased power and collective application likely caused the drive shaft to contact the tailcone's internal structure and tail rotor control tube, resulting in complete loss of drive and control to the tail rotor. The pilot then lost directional control of the helicopter. The Commission could not conclusively determine when the overspeed occurred, but evidence suggested it likely occurred during take-off on the return flight. The cause of the rotor overspeed was very likely the helicopter being flown inadvertently outside the Robinson R22 approved rotor speed limitations.
Factual Information
The pilot, aged 71, held a Commercial Pilot Licence (Helicopter) with about 8700 total flight hours and approximately 72 hours in the Robinson R22 in the preceding three months. The helicopter, serial number 4023, was constructed in 2006 and had a non-terminating certificate of airworthiness issued in 2008. It had been maintained per manufacturers' programmes, with a recent 50-hour inspection completed 26.4 flight hours before the accident. The engine had exceeded its time-between-overhaul limit by about 76 hours. The helicopter's weight and balance were within limits at the time of the accident. Fine weather conditions were reported.
Probable Cause
The rotor overspeed was very likely a result of the helicopter being flown inadvertently outside the Robinson R22 approved rotor speed limitations.