Loss of separation assurance - Airbus A330-300, B-HLV and Boeing B737-800, VH-VUJ, 222 km north-west of Tennant Creek, Northern Territory, on 22 December 2009

On 22 December 2009, at 0253 Central Standard Time, an air traffic controller took action to resolve a loss of separation assurance that occurred on airway route J30, 222 km north-west of Tennant Creek, Northern Territory between an Airbus A330-300 (A330) aircraft, registered B-HLV, and a Boeing Co. B737-800 aircraft, registered VH-VUJ.

The aircraft were approaching each other at flight level 370 while tracking in opposite directions on the same airway route. The air traffic controller managing the airspace did not effectively control the resolution of the developing confliction.

The flight crews of both aircraft identified the traffic confliction and initiated avoidance action to maintain separation.

The investigation found that the controller did not implement a separation plan when the confliction was first identified and that action by the flight crew of the A330 prompted the controller to take action to re-establish separation assurance. In addition, a number of safety issues were identified, including that the controller had not received training in compromised separation recovery techniques and that there was no dedicated control room aisle supervisor during the then peak traffic period. Finally, ambiguity was identified between the Manual of Air Traffic Services (MATS) and the Aeronautical Information Publication (AIP) in relation to the assignment of non‑standard cruising levels and the definition of an 'operational requirement'.

In response to this occurrence, Airservices Australia (Airservices) conducted an internal investigation, which recommended a number of actions to address the safety factors and issues that were identified by the Airservices investigation. The Australian Transport Safety Bureau (ATSB) is satisfied that the action taken by Airservices to clarify the relevant content in the MATS and AIP, and recommended by the Airservices investigation will, when implemented, adequately address the safety issues identified in this ATSB safety investigation.