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What happened

On 8 November 2011, a loss of separation occurred between a Boeing Company 737-8FE, registered VH-VUV, and a Boeing Company 737-838, registered VH-VXM, near Ceduna, South Australia. The aircraft were conducting scheduled passenger flights and were under the air traffic control of Airservices Australia (Airservices). The aircraft were operating on converging tracks at 39,000 ft. The procedural longitudinal separation standard of 20 NM (37 km) was infringed. It is likely that there was between 6 NM (11.1 km) and 12 NM (22.2 km) longitudinal separation between the aircraft.

What the ATSB found

The ATSB found that the two controllers involved were experiencing a high workload due to a range of factors, including the number of tasks and their limited experience. Airservices’ processes for monitoring and managing controller workloads did not ensure that newly-endorsed controllers had sufficient skills and techniques to manage the high workload situations to which they were exposed. In addition, Airservices’s fatigue risk management system (FRMS) did not effectively manage the fatigue risk associated with allocating additional duty periods. The ATSB is also concerned that there had been increasing traffic levels and complexity in some sectors in recent years, combined with a decrease in the experience levels of controllers and without a concomitant increase in controller resources. In addition, although Airservices has been in the process of developing and trialling a flight plan conflict function for procedurally-controlled aircraft for several years, the fact that it is still not operational is a safety issue.

What's been done as a result

Airservices reported that the airspace sectors involved in the occurrence had been re-sectorised into three sectors in November 2012 to manage workload and that a working group had been established to determine a suitable workload model to monitor and forecast controller workload on a sector by sector basis. The first stage of a flight plan conflict function had also been deployed in Brisbane Upper Airspace, with further roll out planned in Melbourne Centre in 2014.
In addition, Airservices reported that an updated FRMS had been implemented in July 2012 and that it had addressed the systems limitations outlined in the report.

Safety message

High workload can have significant effects on a controller’s performance. It needs to be monitored and managed using a systemic approach, particularly for less experienced controllers but also those who have recently received a new endorsement. Other recent loss of separation occurrences involving high workloads and newly-endorsed controllers indicate that this problem is not restricted to the sectors involved in this occurrence. Ideally the best way of managing workload is to reduce the level of work demands and distractions. If the work demands cannot be reduced, then another option is to ensure the controllers have the experience, skills techniques and support to effectively manage their task demands.

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Safety issues

AO-2011-144-SI-01 - AO-2011-144-SI-02 - AO-2011-144-SI-03 -  

Controller workload monitoring and management

The air traffic controller provider’s processes for monitoring and managing controller workloads did not ensure that newly-endorsed controllers had sufficient skills and techniques to manage the high workload situations to which they were exposed.

Safety issue details
Issue number:AO-2011-144-SI-01
Who it affects:All relatively inexperienced controllers
Status:Adequately addressed


 

Allocation of additional duty periods

The air traffic services provider’s fatigue risk management system (FRMS) did not effectively manage the fatigue risk associated with allocating additional duty periods.

Safety issue details
Issue number:AO-2011-144-SI-02
Who it affects:All controllers
Status:Adequately addressed


 

Procedural air traffic control conflict detection system

Although the air traffic services provider has been working on the issue for several years, there was still no automated air traffic conflict detection system available for conflictions involving aircraft that were not subject to radar or ADS-B surveillance services.

Safety issue details
Issue number:AO-2011-144-SI-03
Who it affects:All en route flights under procedural control
Status:Adequately addressed

 
General details
Date: 08 November 2011 Investigation status: Completed 
 Investigation type: Occurrence Investigation 
Location   (show map):near Ceduna Airport Occurrence type:Loss of separation 
State: South Australia Occurrence class: Airspace 
Release date: 18 October 2013 Occurrence category: Serious Incident 
Report status: Final Highest injury level: None 
 
Aircraft 1 details
Aircraft manufacturer: The Boeing Company 
Aircraft model: 737 
Aircraft registration: VH-VUV 
Serial number: 37821 
Operator: Virgin Australia 
Type of operation: Air Transport High Capacity 
Damage to aircraft: Nil 
Departure point:Perth, WA
Destination:Brisbane, Qld
Aircraft 2 details
Aircraft manufacturer: The Boeing Company 
Aircraft model: 737 
Aircraft registration: VH-VXM 
Serial number: 33483 
Operator: Qantas 
Type of operation: Air Transport High Capacity 
Damage to aircraft: Nil 
Departure point:Port Hedland, WA
Destination:Melbourne, Vic.
 
 
 
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Last update 01 March 2016