The pilot, an enthusiastic light aircraft owner, had organised a week end "fly in" to his airstrip at Devon Downs, which was attended by light aircraft pilots and parachutists together with their families and friends. During the day a programme of general flying was carried out and late in the afternoon the pilot flew to nearby Scrubby Flat with the two passengers to pick up some sleeping bags. The passenger in the right hand front seat was also a qualified pilot but the right hand control column had been removed earlier in the day to permit parachute dropping and had not been replaced. The people assembled at the airstrip at Devon Downs first sighted the aircraft on its return as it climbed up from the nearby Murray River valley which, in this area, is bordered by 200 feet high cliffs. The aircraft then made a shallow descent and flew along the strip on a heading of about 250 degrees, at a very low height. At the western end of the strip the aircraft pulled up steeply to between 200 and 300 feet above the ground and began a "wingover" turn manoeuvre to the left. As the turn progressed to the point at which the wings were steeply banked and the fuselage approximately horizontal, the spectators saw the aircraft falter, then the nose dropped and the aircraft dived into the ground at a very steep angle. A fierce fire broke out immediately on impact and the aircraft was completely destroyed.

The aircraft departed from Port Pirie after refuelling in the course of a flight from Coober Pedy to Parafield. The pilot had not lodged a flight plan and there is no evidence that he consulted a weather forecast. The aircraft carried only VHF radio. Following advice from a friend of the pilot that the aircraft had not arrived at Parafield an air search was commenced and the wreckage of the aircraft was sighted late that afternoon at a position 3 miles west of the direct track Port Pirie - Dublin. The aircraft had struck the ground heading west and with the nose and right wing slightly down consistent with the aircraft having been under control. The engine was delivering substantial power at the time of impact. Weather over the route south of Port Pirie was influenced by a strong westerly wind and there were winds of up to 35 knots. The Hummock and Barunga Ranges had been enveloped in low cloud and drizzle throughout the morning and there are reports that the cloud cover extended to a considerable height in the area of the ranges and across the track which the aircraft might be expected to follow. A number of aircraft were seen and heard in the area during the period in which the accident occurred but it has not been possible to establish the precise flight path of this aircraft.

Following the commencement of aircraft vibration in flight at 4,000 feet, the pilot advised Alice Springs that he was returning and expected a normal approach and landing. He attempted to isolate the source of the vibration by checking the magnetoes and by applying carburettor heat, and then he proceeded to cut each engine in turn by moving the appropriate mixture control to the idle cut off position. After cutting the port engine the pilot trimmed out the rudder foot load, but did not increase power on the starboard engine. Some minutes later, realising that he had lost considerable height and was now down to some 500 feet above ground level, he attempted to restore power on the port engine and believes he reselected the mixture control to "rich". He then moved both throttle and pitch levers to climb power settings, but although the pilot still had considerable right rudder trim applied he felt no asymmetric foot load. The aircraft gained 100 feet and then flew level at 90 knots, with the vibration continuing. The pilot lowered the nose and as the aircraft began to lose height again he decided that he must land straight ahead. He transmitted a "Mayday" call and with the wheels and flaps retracted he landed amongst scattered, small trees, damaging the aircraft beyond economical repair. It is possible that the vibration was due to the turbulent airflow induced by the protruding section of the wing walkway. The extra drag arising from this source, however, would not have been sufficient to account for the loss of performance.

Approximately thirty minutes after departure a peculiar odour was noticed in the cabin which the pilot attributed to a boiling battery. He turned off the master switch and, since the odour then partially dissipated, continued the flight and advised that he would only use the aircraft's electrics to report at scheduled times. However, as the flight progressed, the fumes in the cabin became so obnoxious that a forced landing became imperative. The pilot advised his intentions and landed on a lone small claypan but over-ran into the surrounding uneven sand. During the landing the forward baggage compartment door flew open and portions of a burning foam plastic mattress fell out, igniting small spinifex bushes. After disembarkation, the fire, now obviously in the baggage compartment, was quickly extinguished and the spinifex fires were trampled out. The investigation established that a rolled foam mattress, which was the last item loaded at Birdsville, partially unravelled itself in flight and contacted the illuminated hot naked bulb in the baggage compartment light causing the foam to smoulder and emit acrid smoke and fumes which were carried back to the cabin. The composition of the foam was such that the smouldering would continue even when the heat source was removed but it is probable that the mattress did not burst into flames until the door flew open during the landing roll.

The aircraft was engaged on type endorsement training and the pilot in command was occupying the right hand seat. After climbing to 3, 000 feet in the Delissaville area, a series of simulated engine failures was carried out and on each occasion the undercarriage warning horn was silenced by opening the throttle of the inoperative engine. At the conclusion of these exercises the pilot under instruction was told to carry out an asymmetric landing and for this exercise the starboard throttle was set to the zero-thrust position which also silenced the warning horn. During the descent circuit, and approach to land, however, the warning horn sounded almost continuously due to the almost closed position of the port throttle. Reference was not made to the check list provided in the aircraft during these stages of the flight and, when the pilot under instruction did not lower the undercarriage, his omission was not detected by the instructor. The significance of the horn escaped both pilots probably due to the familiarity with its sound during the preceding exercises and the landing was completed with the wheels retracted.

The pilot had flown various Cessna types of aircraft but his experience on the Cessna 177 type was limited. The Cessna 177 differs from the other types which the pilot had flown in that it has a fuel shut-off selector located near the carburettor heat control. After taking off from an authorised landing area on the property of one of his passengers the pilot decided to land in another nearby field. At about 500 feet on final approach he selected what he thought was carburettor heat and shortly afterwards there was a complete loss of engine power. He then prepared to make a forced landing into a nearer field and during a subsequent cockpit check found that he had inadvertently operated the fuel shut-off instead of the carburettor heat. The fuel was selected on, the engine re-started and the pilot applied full power with the intention of abandoning the landing. The nose leg then struck and was damaged by a power wire of which the pilot was not aware. The aircraft was landed straight ahead and the nose leg collapsed when it contacted the ground.

Realising he was unlikely to become safely airborne over obstacles ahead, abandoned the take off and endeavoured to stop the aircraft, but he was unable to do so before it entered a swamp where the nose landing gear was torn off. The aircraft came to rest in swamp grass, substantially damaged.

As the aircraft neared the water it was levelled and full collective pitch was applied to cushion the touchdown. The aircraft struck the water at a forward speed estimated to be 20 knots, the nose pitched down into the 6 feet deep water and the aircraft overturned. After leaving the aircraft both pilots noticed that the wind was now easterly at about 5 knots.

The pilot submitted flight plan details to Moorabbin by telephone at approximately 1245 hours EST indicating that he intended to track direct to Mildura at an altitude below 5000 feet and that the estimated time for the flight was 104 minutes. At 1334 hours the pilot advised Melbourne Flight Service Unit by radio that he had departed from Lovely Banks at 1330 hours and estimated that he would be over Maryborough at 1400 hours. This communication was acknowledged and no further calls were received from the aircraft. Between 1345 hours and 1350 hours, the sound of an aircraft was heard in the Yendon area, some 15 miles south east of Ballarat. The engine noise, which was normal when first heard, rose to a high pitch and intensity and then ceased abruptly. The wreckage of the aircraft was found shortly afterwards at a position approximately 2 miles west of the direct track from Lovely Banks to Maryborough. Examination of the wreckage indicated that the aircraft had struck the ground at high speed in a steep nose down attitude. The aircraft disintegrated on impact and there was no fire. There is evidence from witnesses on the ground in the general vicinity of the accident site that the cloud base was low and there were showers in the area. Another pilot, on a flight from Melton, was approaching the Yendon area a few minutes before the time of the accident and was forced to turn back when he encountered increasing cloud and a lowering cloud base with considerable rain ahead.

Both aircraft converging on Moorabbin apt.BLM in blind spot below combing of RCN.Plt RCN didn't see BLM until too late to avoid collision. Wreckage of both aircraft fell into built up area, causing minor damage.