Section 21 (2) of the Transport Safety Investigation Act 2003 (TSI Act) empowers the Australian Transport Safety Bureau (ATSB) to discontinue an investigation into a transport safety matter at any time. Section 21 (3) of the TSI Act requires the ATSB to publish a statement setting out the reasons for discontinuing an investigation.
On 29 November 2012, the ATSB commenced an investigation into a loss of separation involving two Qantas Airways Airbus A330s, registered VH-EBM (flying as QFA485) and VH-QPC (flying as QFA762). The loss of separation took place approximately 148 km east of Narrogin, Western Australia, on 28 November 2012 with the aircraft on crossing tracks.
VH-EBM was inbound to Perth maintaining flight level (FL) 380[1] and VH-QPC was outbound from Perth on climb to FL 410. A short-term conflict alert was received by the controller as VH-QPC climbed through FL 370, approximately 15 NM (about 28 km) before the aircraft passed.
In response, the controller initiated compromised separation recovery actions. During this recovery action, separation between the two aircraft reduced to 2.84 NM (5.26 km) laterally and 900 ft vertically. There were no traffic collision avoidance system[2] alerts.
In reviewing the information gathered during its investigation, the ATSB determined that there were no associated safety issues or elements of the occurrence that have not already been covered in detail in other recent air traffic-related investigations (see AO-2011-090, AO-2012-012 and AR‑2012‑034).[3] The controller in question had completed compromised separation recovery training and had 8 months consolidation on this sector following their initial rating and en route endorsement. There were no identified training, rostering, fatigue or staffing issues and sector handover/takeover was not a factor. While the controller involved had been under moderate to high workload earlier in the shift, the workload was low at the time of the occurrence and there was no evidence that distraction was a factor.
The controller was responsible for two airspace sectors at the time of the occurrence. Airservices Australia has since undertaken significant work in re-structuring the sectors in the airspace over Western Australia. Although the ATSB determined that required voice coordination between sectors was not completed by the controller in this occurrence, this did not affect the controller’s awareness of the traffic as he was already interacting with the aircraft that were involved in the occurrence.
The ATSB did not find any organisational or systemic issues that contributed to the occurrence or that might adversely affect the future safety of aviation operations. On that basis, the ATSB has decided to discontinue its investigation.
[1] At altitudes above 10,000 ft in Australia, an aircraft’s height above mean sea level is referred to as a flight level (FL). FL 380 equates to 38,000 ft.
[2] Traffic collision avoidance system (TCAS) is an aircraft collision avoidance system. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder and gives warning of possible collision risks.
[3] All are available on the ATSB website at www.atsb.gov.au.