What happened
A twin-engine aircraft was engaged in magnetometer survey operations out of an airport for several weeks prior to the accident. On the day of the event, the flight departed at 06:30 local time and arrived at the designated survey area approximately one hour later. During the mission, the Doppler equipment malfunctioned around 07:50, and the aircraft subsequently encountered light rain. Due to these issues, the crew decided to terminate the survey and return to Tennant Creek.
At 09:14, the crew communicated that they were positioned within the airport circuit area, noting wind conditions of 14 knots from 070°. This communication served as the final contact with the aircraft. Shortly thereafter, the plane crashed into a prairie located two miles west of the runway 07 threshold. The impact resulted in the total destruction of the aircraft and six fatalities, including an 11-year-old passenger.
Findings
Post-accident investigations of the wreckage revealed that one of the redundant aileron control chains, located near the control wheel sprocket in the pilot's column, had broken. Specifically, a link pin failed, which may have caused the assembly to jam while the control wheel was being turned. Because the right-hand cockpit seat and rudder pedals had been removed to allow a crew member access to the nose for survey equipment, there was no co-pilot present to take control of the aircraft.
While the investigation could not definitively establish the exact reason for the loss of control, it noted that a mechanical failure in the aileron control system occurred alongside the possibility that the pilot may have experienced a temporary impairment of ability.