The pilot submitted a flight plan indicating a planned departure from Cobar at 1500 ESuT (1400 EST). A refuelling stop was to be conducted at Windorah. The planned arrival time at Osborne Mine was 1830 EST. Last light in the area was 1931.
The aircraft left Cobar at about 1455 EST. (The reason for the late departure was not established.) The planned flight time to Windorah was 2 hours 40 minutes. The aircraft was on the ground at Windorah for about 1 hour 30 minutes, apparently because the passengers walked to the township. Refuelling was completed at Windorah at about 1845. The planned flight time from Windorah to Osborne Mine was 1 hour 30 minutes. The pilot contacted the mine by radio and reported that he would be arriving at 2030. The runway lights were then activated by the mine staff.
A witness at the mine saw the aircraft, with navigation lights operating, fly overhead at an estimated height of 300 ft above ground level, considerably lower than the normal aircraft altitude. The aircraft was visible in the glow of the lights at the mine. A short time later, the witness was in a position to see the runway lights, and noted that the aircraft was to the north of the runway. He then lost sight of the aircraft as he drove the remaining distance to the strip. Later, he reported to the mine's communication centre that the aircraft had not landed. A formal search was commenced at 2100 when the pilot failed to cancel his search and rescue watch. A satellite which monitors transmissions from emergency locator beacons detected a beacon signal at 2132, when it passed over the accident area. The aircraft wreckage was subsequently located about 400 metres north of the airstrip.
Wreckage examination
Examination of the wreckage indicated that the aircraft struck the ground at a high rate of descent, and banked about 50 degrees right. Aircraft speed at impact was estimated at about 100 kts, and the engine was developing moderate power. No fault was found in any aircraft system which might have contributed to the accident. The impact was not survivable.
Pilot experience
The pilot was the holder of a private pilot's licence and a current medical certificate. He held a Night Visual Flight Rules rating and had accrued 30.4 hours of night flying experience. To act as pilot in command of an aircraft under these rules it was necessary for the pilot to satisfy a number of recent experience requirements. These included one hour flight time at night in the previous 12 months; one take-off and landing at night in the previous six months to fly without passengers; and three take-offs and three landings at night within the previous 90 days in order to carry passengers in the aircraft. According to the pilot's logbook he had not met any of these criteria. His most recent night flying had been conducted in late July 1997.
Flying conditions at Osborne
Some high cloud was present in the mine area. Visibility was good, but the night was dark with no moon and no visual horizon. The wind was blowing from the north-east at right angles to the runway and about 10 to 15 kts in strength.
A parking area and lit windsock were located on the southern side of the airstrip near its south eastern end. The runway lighting system contained a series of lights which pilots could use as a glide slope indicator when landing towards the south-east. Since the pilot had never previously landed at the airstrip during darkness it is not known whether he was aware of this feature.