Final Report


What happened

On 24 April 2014, an Airbus A330 en route from Brisbane, Queensland to Singapore was maintaining 36,000 ft when the air traffic controller cleared an Airbus A320 on a reciprocal track en route from Darwin, Northern Territory (NT) to Brisbane, to climb through the A330's level. This resulted in a loss of separation assurance about 73 km east-south-east of Tindal, NT.

Recorded data from the two aircraft showed that the minimum vertical separation was 224 ft at 0249:04 Eastern Standard Time, when the two aircraft were 9.96 NM (18.45 km) apart horizontally. The minimum horizontal separation was 2.21 NM (4 km) at 0249:40, when the aircraft were 1,720 ft apart vertically. There was no loss of separation as the surveillance separation standard of 5 NM (9.26 km) was maintained when the 1,000 ft vertical separation standard did not exist. In addition, the vertical separation standard re-established before the surveillance separation standard was compromised.

What the ATSB found

The ATSB determined that the en route controller did not identify the potential confliction and assigned direct tracking and climb to the southbound A320 aircraft. The controller had occupied an active air traffic control position for a period of about 3 hours and 55 minutes during a night shift, without a formal rest break, and was likely experiencing the effects of fatigue at the time of the occurrence.

The ATSB identified safety issues relating to Airservices Australia’s utilisation of shift sharing practices for the Tops controllers resulting in them sustaining a higher workload over extended periods without a break, during a time of day known to reduce performance capability. The requirement for skills-based training for effective compromised separation recovery actions was also identified.

What's been done as a result

Airservices Australia has undertaken a number of safety actions relating to compromised separation recovery training. In addition, Airservices reported that they were reviewing the application of published fatigue risk management system guidelines for air traffic control staff undertaking night shift duties.

Safety message

This occurrence is a reminder of the potential for errors to occur when experienced personnel are working for extended periods during periods of circadian low without effective risk mitigators to manage fatigue induced error or consideration of traffic volume and complexity.

The occurrence


Safety analysis


Safety issues and actions

Sources and submissions