Background
The pilot was serving as a relief pilot for the Eastern Goldfields Section of the Royal Flying Doctor Service, based in Kalgoorlie. On 30 April 1981, he was rostered as duty pilot from 1100 to 1700 hours. Shortly after 1100, the chief pilot advised him of a required flight to Jameson and return, with a refueling stop at Warburton en route. The pilot expressed concern about completing the flight in daylight, but after discussion with the chief pilot, it was concluded that the flight should return to Kalgoorlie about ten minutes before last light.
Flight
The aircraft departed Kalgoorlie at 1221 hours. The flight proceeded uneventfully, but delays en route and during refueling resulted in the aircraft not departing Jameson until 1609 hours. Based on flight plan time intervals, the expected arrival time at Kalgoorlie was 1844 hours, which was one hour after last light. The pilot did not hold the necessary qualification to operate a multi-engined aircraft at night, although he held a night rating for single-engined aircraft. He elected to proceed as planned and declared the last section of the flight a Mercy Flight.
Accident
At 1828 hours, when 55 km from Kalgoorlie, the pilot contacted the Kalgoorlie Flight Service Unit and received details of the weather, as recorded thirty minutes earlier. This information included an observation of lightning to the west-south-west and a line of thunderstorms from north-west to south of the aerodrome. At 1840 hours, when about 13 km from Kalgoorlie, he advised that he would use runway 28. No further communication was heard from the aircraft.
Witnesses at Boulder, 4 km east of Kalgoorlie, subsequently reported that a severe squall entered the area shortly before the aircraft was seen turning onto final approach for the runway. The strong wind had generated dust clouds, and the aircraft was seen to enter one of these while executing a number of sudden attitude changes. It then collided with a mineshaft headframe. The left wing was torn from the aircraft, which then crashed to the ground nearby. A passenger was seriously injured while four other occupants were killed.
Investigation Findings
Examination of the wreckage found no pre-existing defect or malfunction that could have contributed to the accident. The official finding stated that there is insufficient evidence to determine the cause of the accident, but it is evident that the aircraft encountered severe turbulence at low height during the approach for landing.