The aircraft had been engaged in mustering cattle in flat, open country. The pilot elected to land near a utility to obtain further instructions from stockmen in the vehicle. Approaching the vehicle, the aircraft suddenly commenced to vibrate severely and to lose height. The pilot was unable to avoid a collision with the utility, following which the aircraft struck the ground heavily and overturned. No fault was subsequently found with the helicopter which might have contributed to the development of the accident. The symptoms described by the pilot suggested that the vibration experienced was associated with a main rotor blade tracking problem. It was likely that while manoeuvring to reduce speed prior to landing, the aircraft was placed in a position where the lead and lag action of the rotor blades temporarily exceeded the capacity of the blade dampers. Because of the low height above the ground at which this occurred, there was insufficient time or height in which the pilot could effect recovery.
