Loss of separation involving a Boeing 747-338, VH-EBX and Airbus A320-211, VH-HYG, 74 km west of Adelaide VOR, South Australia, on 7 July 1995

VH-EBX was tracking eastbound on air route Y44, and VH-HYG was tracking westbound on air route Q34B, both aircraft were at FL 370. These air routes diverge from Adelaide towards the west.

At approximately 75 km west of Adelaide, when the two aircraft were within 22 km of each other, with a track angle difference of 20 degrees, which was increasing as they came closer, VH-EBX experienced a traffic alert and collision avoidance system (TCAS) traffic advisory (TA). This was followed 20 seconds later by a resolution advisory (RA).

The pilot of VH-EBX responded immediately to the RA, initiating a climb to FL 380 followed by a descent back to FL 370. Neither aircraft changed heading.

The aircraft passed with a separation of 8.5 km horizontal and 900 ft vertical.

The air traffic controller had been monitoring the situation for some time and was confident that the aircraft would pass with at least the minimum required horizontal separation standard of 9 km.

The recommended vertical deviation following an RA should be no more than 700 ft. The pilot of VH-EBX climbed the aircraft through 1,000 ft before returning to the assigned level.