The ATSB has found that the Bankstown midair collision accident was the result of a Piper Warrior passing through the extended centreline of runway 29 centre, to which the pilot had been cleared, and continuing on to the extended centreline of runway 29 left.
The Piper collided with a Socata Taralga, which had been cleared for its final approach to the left runway. The Piper became uncontrollable and crashed in an industrial area to the south-east of the airport. All four occupants were fatally injured. The Socata landed at Bankstown and its occupants were uninjured.
General Aviation Airport Procedures (GAAP) were in operation at the time of the accident. Under GAAP, pilots operating in visual meteorological conditions were responsible for aircraft separation when airborne in the circuit. Air traffic controllers were responsible for issuing sequencing instructions and providing traffic information to assist pilots to avoid other traffic. The pilot of the Piper was issued traffic information on the Socata and the pilots of the Socata reported that they saw the Piper.
A number of aircraft were conducting training circuits on runway 29 left (via left circuits) and other aircraft were arriving and departing Bankstown on runway 29 right (via right circuits). The pilot of the Piper had requested, and been issued with, a clearance to land on runway 29 centre from a right circuit and the pilots of the Socata had been issued with a clearance to conduct a touch and go landing on runway 29 left from a left circuit.
A significant proportion of GAAP operations at Bankstown involved contra-circuits onto runways 29 left and 29 centre, which were 107 m apart. Contra-circuit operations to runways less than 213 m apart were permitted, provided that the air traffic controllers provided traffic information to pilots about aircraft in the opposite circuit.
The investigation concluded that there were insufficient visual cues for a pilot in one circuit to reliably assess the collision potential of an aircraft in the opposing circuit, when both aircraft were conducting contra-circuits to parallel runways 107 m apart.
In December 2003, Airservices Australia, modified its procedures for Bankstown so that, where aircraft involved in contra-circuits are likely to be at base or final legs at approximately the same time, the use of the centre runway would be denied.
The ATSB has issued recommendations to Airservices Australia and CASA regarding the estimation of overall midair collision risk at major GA airports, and the provision of advisory material for pilots about collision risk management strategies.