Flight and Incident Sequence
The aircraft had been conducting magnetometer survey flights from Tennant Creek Airport for several weeks. It departed at 06:30 local time and reached the survey area one hour later. At 07:50, the Doppler equipment became unserviceable. Shortly after, light rain was encountered, prompting the crew to abandon survey work and return to Tennant Creek. At 09:14, the crew radioed that they were in the circuit area. The reported wind was from 070° at 14 knots. This transmission was the last contact with the flight. One minute later, the twin-engine aircraft crashed in a prairie located 2 miles west of the runway 07 threshold.
Damage and Occupants
The aircraft was totally destroyed. All six people on board were killed, including an 11-year-old child.
Wreckage Examination
Examination of the wreckage revealed that one of the duplicated aileron control chains in the pilot's control column was broken near the control wheel sprocket. A link pin had failed and might have subsequently jammed the assembly as the control wheel was being rotated. Control could not be taken over by the copilot because there was no copilot on the flight. The right-hand cockpit seat and rudder pedals had been removed to allow a crew member access to the nose area for survey work.
Probable Cause
The cause of this accident was a loss of control of the aircraft, and although the evidence available does not permit the reason for the loss of control to be determined, the possibility cannot be eliminated that the pilot suffered an impairment of ability and, coincidentally, was deprived temporarily of aileron control.