A Brisbane Centre air traffic controller who was found asleep at their workstation towards the end of their shift had worked multiple consecutive night shifts resulting in sleep debt, an ATSB investigation report details.
The approach controller, who was managing the Cairns Terminal Control Unit (TCU) within Airservices Australia's Brisbane Air Traffic Services Centre ('Brisbane Centre') was found asleep at about 5:15 am on 9 December 2022. The oncoming approach controller found the night shift controller lying across 2 chairs with a blanket covering them.
Several factors contributed to the controller failing asleep, the investigation found.
"These included the time of day, the very low workload in their sector, a roster pattern with multiple consecutive night shifts, and the controller increasing their risk of falling asleep by lying across 2 chairs, not moving, and not undertaking activities to maintain mental alertness," ATSB Chief Commissioner Angus Mitchell said.
"The controller had also been working multiple night shifts with reduced extended rest periods, which likely reduced their ability to obtain restorative sleep."
When the controller was found asleep, there was no traffic in the Cairns TCU airspace, which was usual for that time of day, and there were no scheduled flights until after their shift.
However, had the controller been woken by a radio broadcast, they may have experienced 'sleep inertia', with the risk of delayed communications, or incorrect instructions/actions, and likely affecting their ability to manage any conflicts arising from traffic infringing their airspace without a clearance.
"There were no negative consequences from this occurrence, but it does highlight areas for improvement in work scheduling and fatigue risk management," Mr Mitchell said.
The investigation also identified issues relating to Airservices Australia's broader management of fatigue.
"An over-reliance on tactical changes to manage the roster at Airservices was likely due to an underlying lack of resources," Mr Mitchell explained.
"As a result, cumulative fatigue was not being effectively managed strategically, and an over-reliance on tactical principles did not identify or manage fatigue risks arising from the work schedule."
Following the incident, Airservices has increased its overall number of air traffic controllers, including in the North Queensland group.
The investigation also identified Airservices' fatigue assessment and control tool (FACT) had the means of identifying situational factors that influenced fatigue, but the tool's effectiveness was limited as supervisors were not identifying low workload as a fatigue hazard.
Airservices has subsequently developed additional guidance and training on the fatigue risk assessment process, including information on how low traffic situations should be treated as high risk.
Separately, the Civil Aviation Safety Authority has recently introduced changes to air traffic service fatigue risk management system requirements. Airservices is working with CASA to trial its existing system against the new requirements, and is using feedback to make improvements.
"Fatigue remains one of the most relevant ongoing concerns for safe transport, despite increased awareness across the transport sector," Mr Mitchell said.
"We urge transport operators to investigate fatigue events to identify and remedy deficiencies in work scheduling, fatigue risk management processes and risk controls."
