A group of pilots had arranged to conduct a fly-in at Clifton, Queensland. As part of their day's outing, they had also arranged for a visit to a collection of aircraft at Toowoomba. The accident pilot was to fly a single-seat RV-3 amateur-built aircraft on behalf of the aircraft owner. To re-familiarise himself with the aircraft, the pilot had conducted some local flying at Southport on the previous day.
Soon after the RV-3 became airborne during the departure from Southport for Toowoomba, the engine began to run roughly. The pilot landed the aircraft and operated the engine to clear what he suspected to be spark plug fouling. The subsequent take-off was apparently normal, and the aircraft arrived at Toowoomba without further incident.
Following the visit to the aircraft collection, the pilots prepared for departure to Clifton. The pilot of the RV-3 taxied to the threshold of runway 11 for departure. Witnesses reported that the take-off and initial climb were normal until the aircraft reached a height of about 200 ft, when the engine suddenly lost power.
The nose-attitude of the aircraft was observed to lower and the engine subsequently regained power. The aircraft then began a gentle climb and turned left. Witnesses reported that it appeared the pilot was attempting to manoeuvre the aircraft to land on the aerodrome. After the aircraft gained some altitude, the engine again lost power. The bank angle steepened and the nose-attitude lowered significantly. The aircraft's wings were then seen to level and the nose lifted to a near level attitude, however, the aircraft continued to descend at a high rate until impact on a playing field. The sides of the cockpit buckled outwards during the impact, allowing the fuselage behind the pilot to move forward, and the pilot's shoulder harness to slacken. He was no longer adequately restrained and received fatal injuries.
The pilot was correctly licensed and qualified to conduct the flight.
The aircraft was registered as Experimental, and was fitted with a fuselage fuel tank and a tank in each wing. The fuel selector valve was positioned to the right-wing tank and there were indications that both wing tanks had contained a significant quantity of fuel at impact.
Examination of the aircraft found that a fuel line connecting the fuel filter to the engine-driven pump had a loose connection at the filter. The carburettor float showed evidence that the carburettor fuel level had been low during aircraft operation. The condition of the spark plugs was consistent with operating in a lean mixture immediately prior to the engine stopping. No other defects considered likely to have contributed to the accident were found.
In addition to the engine-driven fuel pump, the aircraft was fitted with an electrically-powered auxiliary fuel pump. Both pumps were tested and found to operate normally. The loose fuel line connection could have allowed air to enter the carburettor. This may have been prevented had the electric pump been selected on, as it would have provided fuel pressure to the engine-driven pump. The investigation could not determine whether the electric fuel pump had been selected on for the take-off. The aircraft owner said that he had never used the electric pump for take-off.