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Separation assurance of concurrent procedures
Date issue released
Issue number
AO-2019-041-SI-04
Issue Status
Closed – Adequately addressed
Transport Function
Airspace
Issue Owner
Airservices Australia
Mode of Transport
Aviation
Safety Issue Description

The Airservices Australia MARUB SIX standard instrument departure and the missed approach procedure for runway 34R directed aircraft onto outbound tracks that did not sufficiently assure separation between aircraft following the procedures concurrently.

Issue Status Justification

The safety action implemented by Airservices Australia is likely to address the safety issue, but the ATSB urges Airservices Australia to monitor the safety outcomes to optimise the procedure design in the long term.

Proactive action
Action number
AO-2019-041-PSA-01
Organisation
Airservices Australia
Action Status
Closed
Action description

In February 2020 Airservices advised that it would:

Conduct a risk assessment of MARUB SIX SID and missed approach operations on runway 34R at night to inform an options analysis to improve the effectiveness of system defences.

Subsequently, Airservices redesigned the missed approach for the Runway 34R instrument landing system (ILS) and ground-based augmentation system landing system (GLS) approaches, effective 2 December 2021.

Airservices reported:

The [runway 34R] missed approach now has a turn point that closely replicates where an aircraft on the MARUB SID [standard instrument departure] would commence turning. This provides an increased likelihood that distance will be maintained longitudinally between the aircraft. The MARUB SID has a tighter turning requirement ([minimum angle of bank] 25°) and steep climb gradient (4.8% to 1500ft, then 3.3%) which should prevent the missed approach aircraft from turning inside the departing aircraft. The MARUB SID turns to intercept the 075° track whilst the missed approach turns to a point and then tracking 060° which will permit divergence between the aircraft.
ATSB Response

The ATSB welcomes the safety action to reduce the likelihood of converging flight paths between aircraft flying these procedures concurrently, noting also that the later, and defined, missed approach turning point also should result in:

  • reduced flight crew workloads during the missed approach
  • more consistent missed approach flight paths
  • reduced controller workload to separate aircraft that are on similar flight paths from the end of the runway, with increased likelihood of track divergence.

The ATSB also notes the complexity of designing procedures to minimise conflict, especially in the case of a missed approach with other aircraft departing the same runway, as there are many factors that Airservices is required to take into account. The ATSB urges Airservices to apply its expertise and data to monitor the safety outcomes on an ongoing basis so that the lowest-risk designs can be identified and implemented in the long term.