Controller fatigue contributed to a loss of separation assurance incident between a Singapore Airlines Airbus A330-300 and a Jetstar Airways A320 over Australia.
The event occurred in the early hours of the morning on 24 April 2014, while the SIA A330 (regietered 9V-STQ) operated the northbound Brisbane-Singapore route, and the Jetstar A320 (VH-VFH) operated the soutbound Darwin-Brisbane route, says the Australian Transport Safety Bureau.
The A330 was cruising at 36,000ft when an air traffic controller cleared the A320 on a reciprocal track, asking its crew to fly through the A330’s level.
As a result, at 02:49:04 the minimum vertical separation was just 224ft when the aircraft were 9.96nm (18.5km) apart horizontally. Thirty-six seconds later, at 02:49:40, the minimum horizontal separation was 2.21nm, and vertical separation was 1,720ft.
“There was no loss of separation as the surveillance separation standard of 5nm was maintained when the 1,000ft vertical separation standard did not exist,” says the ATSB. “In addition, the vertical separation standard re-established before the surveillance separation standard was compromised.”
Following an investigation, the ATSB discovered that the controller failed to identify the possible conflict for the southbound A320.
“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,” it says.
As a result of the incident, air traffic control provider Airservices Australia is reviewing its fatigue risk guidelines for controllers working the night shift.
“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,” says ATSB.