Loss of separation involving a Boeing 747-438, VH-OJD and Saab SF-340B, VH-OLN, 27 km south-west of Sydney, New South Wales, on 23 October 1995

VH-OJD was cleared to track inbound via the 229 VOR radial on descent to 6,000 ft. The Approach South radar control sector controller (APP S) was processing the aircraft for landing on runway 16R. Due to operational requirements, the APP S controller delayed turning the aircraft onto a right downwind for that runway.

VH-OLN had departed runway 16R, cleared initially to climb to 5,000 ft. The Departures South radar control sector controller (DEP S) cleared the aircraft for an early right turn and an unrestricted climb to its planned cruising level.

The APP S controller was about to instruct the crew of VH-OJD to turn onto right downwind for runway 16R when he recognised that VH-OLN was climbing through 5,000 ft. In an attempt to maintain lateral separation, he instructed the crew of VH-OJD to turn left immediately and advised them of the traffic ahead to their right. At this time, the crew of VH-OJD advised that they were complying with a TCAS Resolution Advisory and climbing to 7,000 ft.

Recorded radar information indicated that the aircraft had closed to approximately 2.1 NM, with 400 ft vertical separation when the minimum separation should have been 3 NM or 1,000 ft vertically. Each had penetrated their respective airspace boundary buffer.

The runway 16 airspace agreement has a narrow corridor in the APP S airspace to the west of the airport. This airspace design limits the flexibility available to APP S when vectoring aircraft to downwind for runway 16. The latitude that DEP S may apply when vectoring departing aircraft onto south-westerly headings, and providing climb, is also restricted.

Separation was not ensured before VH-OLN was cleared for an unrestricted climb. The situation was worsened by the high rate of climb achieved by VH-OLN.

Findings

1. The unrestricted climb instruction provided to VH-OLN by the DEP S controller was premature.
2. The vectoring of VH-OJD onto right downwind for runway 16R by the APP S controller was initiated late.
3. The airspace agreement boundary for runway 16 operations restricted flexibility in the processing of both arrival and departure aircraft.

Factors

1. The radar surveillance techniques used by both controllers were inadequate to prevent the loss of the prescribed separation standards.

Safety action

As a result of occurrence 9503423, the Bureau of Air Safety Investigation made interim recommendation IR950212. As the interim recommendation is also applicable to this investigation, it is reproduced below.

IR950212

The Bureau of Air Safety Investigation recommends that Airservices Australia amend the runway 16 airspace agreement boundaries to ensure that arriving and departing aircraft cannot be on, or near, reciprocal tracks. The amendment should address excursions into either buffer area.