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On 8 January 2012, at about 2141 Eastern Daylight-saving time, a loss of separation assurance occurred between a Boeing Company B737-8FE, registered VH-VUJ (VUJ) and a Boeing Company B737-838, registered VH-VZS (VZS), near Tamworth Airport, New South Wales (NSW).
Both aircraft were conducting scheduled passenger services, under the instrument flight rules, with VUJ operating from Sydney, NSW to Brisbane, Queensland and VZS operating from Brisbane to Sydney. Due to weather diversions, the aircraft were operating on reciprocal tracks at the time of the occurrence.

The air traffic controller assigned VUJ climb to the same level maintained by VZS. On activation of the air traffic control system's Short Term Conflict Alert (STCA), when the aircraft were 17.5 NM (32.4 km) and 2,200 ft apart, the controller issued both flight crews instructions that ensured vertical separation was maintained in excess of the required standard and a breakdown of separation avoided.
The controller later reported feeling mentally fatigued following a shift with high complexity and workload. They had not identified the confliction before the STCA, but once aware, the controller's knowledge and application of effective compromised separation recovery techniques was integral in managing the situation.

Following the occurrence, Airservices Australia advised that compromised separation recovery refresher training would be provided to controllers again, in addition to sessions on separation assurance techniques, and that they were implementing a renovated Fatigue Risk Management System and a Normal Operations Safety Survey program.

This incident highlights the need for awareness of the effects of high workload and sustained task complexity on performance, the importance of regular breaks and implementation of strategies, such as the use of conforming levels, when able. In addition, the knowledge and application of effective compromised separation recovery techniques by air traffic controllers is integral in the management of compromised separation situations.

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