Loss of separation involving an Aero Commander 690, VH-NYC and British Aerospace PLC BAe 146-300, VH-EWJ, 40 km east of Glen Innes, New South Wales, on 15 November 1993

On radar handoff from Sydney, both aircraft were at Flight Level (FL) 250 and on the Point Lookout-Casino track. The Brisbane Sector 2 controller indicated to Sydney that this arrangement was acceptable. The lead aircraft, VH-NYC had a groundspeed of 290 kt and VH-EWJ 440 kt. The controller was conscious of this and when he gave a 25 degree heading change right to VH-EWJ, he assessed that separation standards would not be infringed. However, it quickly became apparent that this would not be so.

VH-EWJ was then instructed to descend to FL 240. The minimum distance between the aircraft reduced to 3 NM. This occurred when there was 500 ft vertical separation between the aircraft. Workload on Sector 2 at the time was high with both northbound and southbound traffic. There were also some technical problems with the Sector 2 control console and periodic interruptions occurred as technicians rectified the faults. The controller had held a Sector 2 rating for 2 months, having previously been a controller in Darwin for some 18 years.

The factors considered relevant to the development of this occurrence are:

1. The controller was relatively inexperienced in the position.

2. The sector workload was high.

3. There were probable distractions caused by technicians adjusting the console.

4. The controller was late in vectoring the overtaking aircraft.