British Airways B789 and Qantas A332 at Sydney on Sep 28th 2022, loss of separation during standard instrument departure
Last Update: March 3, 2023 / 09:13:39 GMT/Zulu time
A Qantas Airbus A330-200, registration VH-EBK performing flight QF-926 from Sydney,NS to Cairns,QL (Australia), was also climbing out of Sydney's runway 16R following the DEENA7 SID having departed about 3 minutes after the B789 and about 6.3nm behind the B789.
As the A332 was lighter the aircraft crossed DEENA already at 6000 feet at DEENA while the B789 was still climbing at DEENA and initiated their turn only later thus permitting the A332 to "catch up". A loss of separation occurred, the distance between the aircraft reduced to 600 feet vertical and 2.4nm horizontal, the controller intervened and instructed the A332 to maintain 9000 feet and the B789 to expedite climbing through 10,000 feet.
Australia's ATSB reported the DEENA 7 SID is being revised as the procedure can not ensure separation due to the criteria set for turning.
The ATSB released their final report concluding the probable cause of the incident were:
- When clearing two aircraft on the DEENA 7 standard instrument departure, the controller incorrectly assessed that they would have similar climb performance and became distracted and did not detect the relatively higher climb performance of the departing Airbus A330 aircraft. This resulted in the A330 turning inside the preceding Boeing 787 and a loss of separation standards with that aircraft.
- The DEENA 7 standard instrument departure has no designed positive separation assurance method, making it susceptible to loss of separation occurrences. (Safety issue)
The ATSB analysed:
During the departure of two heavy aircraft conducting the DEENA SEVEN standard instrument departure (SID), the controller assessed that the following Airbus A330 would have a similar climb performance to the leading Boeing 787, without considering that the A330 was conducting a domestic flight and would therefore have a significantly lower fuel load and better climb performance than the preceding heavily-loaded 787. The controller cleared both aircraft, in sequence, to climb to the same level. The controller then became distracted, planning the separation between 2 other aircraft and did not detect the variation in climb performance between the departing A330 and 787.
As the actual climb performance of the A330, on a domestic route, was greater than the climb performance of the 787 on an international route, the separation reduced. When the controller detected the closing aircraft, they instructed both flight crew to take action to increase the separation between their aircraft. During the occurrence, it is likely the controller did not receive a short-term conflict alert (STCA) warning however, they did suspect there had been loss of separation and did not provide a safety alert or advise that the instruction was an avoiding action.
The use of SIDs ‘enable the safe and efficient processing of instrument flight rules11 aircraft … from airports’ (Airservices Australia) and will ‘deconflict potentially conflicting traffic by the use of specific routings, levels, speed restrictions and check points’ (Skybrary). They are particularly useful in high traffic airspace such as departing Sydney Airport. However, according to Airservices Australia, SIDs do not provide longitudinal separation between aircraft which are following in trail with another aircraft, with controller action ensuring the maintenance of separation.
Despite this, the design of the DEENA SEVEN SID (and possibly others) did not provide a positive method of providing lateral separation assurance to departing aircraft with differing climb performance. As the aircraft had to satisfy 2 separate conditions prior to turning, there was no way of ensuring aircraft would turn at the same distance from the airport. As such, lateral separation could not be assured.
Airservices Australia advised that the DEENA SEVEN SID had been redesigned to remove the conditional requirements of the procedure. At the time of writing, the change had been approved and was planned to be released in the first implementation package for the Western Sydney International (Nancy-Bird Walton) Airport project. However, no timeframe for the release of the package was provided.
This article is published under license from Avherald.com. © of text by Avherald.com.
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