Three helicopters were engaged in the mustering of cattle on the property. One became unserviceable during the afternoon but returned to the muster after rectification. By 1830 hours the herd of 4000 cattle were near the homestead and one of the pilots was instructed to return to the homestead and land. The other two helicopters continued the muster using the landing lights of the aircraft for lighting. Last light in the area was 1842 hours. At about 1910 hours the muster was nearing completion and the pilot of VH-HMX was instructed by the property overseer to move his aircraft away from the herd. Shortly afterwards the pilot of the other aircraft observed a fire, and upon investigation found the wreckage of VH-HMX. The aircraft had struck the ground in a steep nose down attitude while banked at about 90 degrees to the left. The pilot was neither approved nor qualified to conduct night mustering operations. An inspection of the wreckage found that the landing light had failed prior to impact, however, due to the damage to the helicopter no reason for the failure could be established. It is considered likely that while the helicopter was being turned away from the cattle, the landing light failed and with the the resulting loss of visual cues the pilot became disoriented and lost control of the aircraft.
