Loss of separation involving Airbus A330, VH-EBK and Boeing 787, G-ZBKF, near Sydney Airport, New South Wales, on 28 September 2022

Executive summary

What happened

On the afternoon of 28 September 2022, a Boeing Company 787-9 (787), registered G-ZBKF, was being operated by British Airways as flight number BA16, on an air transport flight from Sydney, New South Wales, to Singapore. At the same time, an Airbus A330-202 (A330), registered VH-EBK, was being operated by Qantas Airways as flight number QF926, on an air transport flight from Sydney to Cairns, Queensland.

At approximately 1508 local time, BA16 was cleared for take-off from runway 16R to conduct the DEENA SEVEN (DEENA 7) standard instrument departure (SID). Shortly after, QF926 was also cleared for take-off conducting the same SID. The Departure controller cleared both aircraft, in sequence, to climb to flight level 280 via the SID.

During the departure, the following aircraft climbed faster than the controller anticipated and turned towards the next waypoint inside the preceding aircraft, resulting in a loss of separation.

What the ATSB found

The ATSB found that the actual climb performance of the A330 was greater than the climb performance of the 787 which was not expected, or identified, by the controller due to their focus on other aircraft. This resulted in the A330, while complying with the SID, turning inside the leading 787, resulting in the loss of separation.

The ATSB also found that the design of the DEENA SEVEN SID did not provide a positive method of providing separation assurance to aircraft with different performance characteristics. 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. That is, separation could not be assured.

What has been done as a result

Airservices Australia advised that the DEENA SEVEN SID has been redesigned to remove the conditional requirements of the procedure. The change has been approved and planned to be released as part of the Western Sydney International (Nancy-Bird Walton) Airport project.  At the time of writing Airservices Australia was developing a timeline for the implementation of the redesigned SID. As such, the ATSB will continue to monitor the safety issue and provide website updates.

Safety message

Maintaining separation in high traffic terminal areas, such as Sydney, requires that both controllers and flight crews remain vigilant, maintain open communications, and use the available systems and tools to minimise the risk of errors. When sequencing departures, controllers should consider a number of factors, including how the flight duration (and the associated fuel load), will likely affect aircraft climb performance.

Standard instrument departures are designed to expedite the safe and efficient flow of air traffic operating from airports through the use of specific routings, levels, speed restrictions and waypoints. Where a SID, with limited designed separation assurance is used, it is important that air traffic controllers regularly monitor individual aircraft performance rather than rely on expected flight characteristics.

The occurrence

On the afternoon of 28 September 2022, a Boeing Company 787-9 (787), registered G-ZBKF, was being operated by British Airways as flight number BA16, on air transport flight from Sydney, New South Wales, to Singapore. At the same time, an Airbus A330-202 (A330), registered VH-EBK, was being operated by Qantas Airways as flight number QF926, on air transport flight from Sydney to Cairns, Queensland.

The Sydney Airport automatic terminal information service (ATIS)[1] indicated that parallel runways were in use, including simultaneous independent departures[2] from runways 16R and 16L.[3]

At approximately 1508 local time, BA16 was cleared for take-off from runway 16R by the Sydney tower controller. They were cleared to conduct a DEENA SEVEN (DEENA 7) standard instrument departure (SID)[4] (Figure 1) from runway 16R and to climb to 5,000 ft.

The DEENA 7 SID required an aircraft to turn right as soon as practicable after take-off, towards the DUNES waypoint[5] and then turn left to track 152° towards the DEENA waypoint. The aircraft was required to have passed DEENA and climbed above 6,000 ft prior to turning right towards the ANKUB waypoint. If the aircraft had not reached 6,000 ft at DEENA, there was a requirement to continue on a heading of 152° until passing an altitude of 6,000 ft, before turning towards ANKUB.

Passing 1,500 ft, the flight crew contacted the departure controller (Departures) and advised them that they were a heavy aircraft[6] on climb to 5,000 ft, departing via the DEENA 7 SID. Departures advised the flight crew the aircraft was identified on radar and instructed them to climb via the SID to flight level (FL) 280.[7]

Figure 1: DEENA SEVEN standard instrument departure (SID) from runway 16R

Source: Airservices Australia, annotated by ATSB

At approximately 1511, and with 6.3 NM spacing behind BA16, QF926 departed from runway 16R, also cleared on a DEENA 7 SID. During the initial climb, the flight crew contacted Departures advising that they were a heavy aircraft, passing 1,500 ft on climb to 5,000 ft, cleared on a DEENA 7 SID. Departures subsequently cleared them to climb to FL 280 via the SID.

BA16 climbed through 6,000 ft at around 25 km from Sydney Airport and initiated a turn to ANKUB in accordance with the SID. QF926 passed DEENA approximately coincident with climbing through 6,000 ft and initiated a turn to ANKUB at approximately 20 km from the airport, also in accordance with the SID (Figure 2).

Figure 2: Flight tracks of both aircraft during their departure from Sydney

Qantas Q926 is depicted in orange and BA16 is depicted in green.

Source: Google Earth with Flight Radar 24 tracks and annotated by ATSB

As QF926 was turning, the controller detected that the aircraft had climbed faster than they had anticipated and instructed QF926 to stop their climb at 9,000 ft, to which the flight crew advised they would do their best. The controller then instructed BA16 to expedite their climb through 10,000 ft.

The controller subsequently advised the flight crew of QF926 that there was a 787 above their aircraft, and they would step climb their aircraft underneath the 787. The Qantas flight crew advised they had sighted the higher aircraft.

There was a loss of separation standards (see the section titled Required separation) between the two aircraft with the minimum vertical separation reducing to 600 ft and lateral separation reducing to 2.4 NM.

The flight crew in BA16 later advised that they had received a traffic alert and collision avoidance system (TCAS)[8] traffic advisory[9] during the event and the first officer subsequently visually identified the A330. They also advised they were informed by air traffic control of the traffic, however this was not recorded on the departures frequency.   

Air traffic controller information

The controller had worked as a controller from 2008 and had moved to Sydney in 2015 where they had qualified in both the Sydney Approach Director and Departures positions. While they mainly worked in the Approach Director position, they were rostered in the Departures position regularly to remain current in that role.

They had conducted compromised separation training in their last departures refresher training session in June 2022.

The controller advised that they expected the A330 would have a comparative climb performance to the 787. Hence, they instructed them to follow the 787. Qantas typically utilised the A330 on international routes, however, more recently had been utilising the A330 on domestic routes, including Sydney to Cairns, with correspondingly lower fuel loads and higher climb performance.

The controller then proceeded to assess other traffic in the area. Specifically, they were assessing a track for an aircraft, on descent from FL 280 to Shellharbour to ensure separation between this aircraft and an Airbus A380, which was in the list to depart runway 16R. They were also assessing the departure tracks for other aircraft due to depart from runway 16L and coordinating a media helicopter, overflying the airspace at 500 ft, with the Bankstown Airport tower controller. The controller advised they considered their workload to be manageable at the time.

Air traffic control procedures

Departure procedures

At the time, auto-release departures were in progress at Sydney Airport. This procedure allowed the tower controller (Tower) to depart aircraft without prior coordination with the departures controller (Departures). Departures had a list of aircraft on their console which were due to depart. These aircraft were listed in order of departure from the runway they were using, but the Tower controller could depart the aircraft from either runway in the order which allowed best use of the runways.

Tower was required to ensure there was a minimum separation between the aircraft of 5 NM when aircraft were departing from runway 16R. When using the DEENA 7 SID, Tower cleared the aircraft to climb to 5,000 ft via the SID, this ensured that departing aircraft continued on a heading of 152° and would not initiate a turn unless they received a further clearance from Departures.

Required separation

The required separation standards at Sydney are specified in the manual of air traffic services (MATS). The manual specified that the separation standard in the Sydney terminal control unit (TCU) was 3 NM lateral or 1,000 ft vertical separation. However, the wake turbulence standards between 2 heavy aircraft, required a minimum of 4 NM separation where aircraft were departing using the same runway, which was the case for this departure.

The A330 departed with the required spacing behind the preceding B787.

Controller traffic alerts

The controller advised they did not receive a short-term conflict alert (STCA) on their console during the event. A replay of the recorded surveillance data indicated the STCA was displayed on a number of occasions. However, Airservices advised that the replay was not a reproduction of the controller’s screen at the time. The parameters for a STCA in the TCU environment are that within the following 60 seconds the aircraft will infringe 2.1 NM lateral separation and or 600 ft vertical separation. In this case, as the separation reduced to 600 ft and 2.4 NM in a turn, it is possible that due to the dynamics of the event, the STCA may not have shown on the controller’s console. However, the ATSB was unable to determine whether the controller received a STCA on their console.

Issuing safety alerts

According to MATS, where a controller becomes ‘aware that an aircraft is in a situation that places it is unsafe proximity to…other aircraft’, the controller should issue a ‘safety alert’. They should also use the term ‘avoiding action’ prior to instructions when in the controller’s judgement, the aircraft ‘is in a situation that places it at risk of a collision with another aircraft under surveillance’.

Weather

The weather at the airport during the occurrence was fine, with good visibility, scattered[10] cloud at 3,000 ft and a 15 kt easterly wind.

Replanning of Sydney Airspace

Airservices Australia advised that in response to the replanning of the airspace in the Sydney area due to the establishment of the Western Sydney International (Nancy-Bird Walton) Airport, which is due to open in 2026, the DEENA 7 SID has been redesigned.

Related occurrences

In the last 10 years, across Australia, there have been 8 occurrences of a loss of separation reported to the ATSB involving aircraft cleared on a SID where a following aircraft has climbed faster than the preceding aircraft.

Of these, 6 occurrences were at Sydney Airport and 5 of these involved the DEENA 7 SID. Of these, 1 occurred in 2012, 1 in 2019, 1 in 2020, and 2 in 2022.

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 rules[11] 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.

Findings

From the evidence available, the following findings are made with respect to the loss of separation involving Airbus A330, VH-EBK, and Boeing 787, G-ZBKF near Sydney Airport, New South Wales on 28 September 2022.

Contributing factors

• 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)

Safety issues and actions

DEENA 7 Standard instrument departure had no positive separation assurance method

Safety issue number: AO-2022-047-SI-01

Safety issue description: The DEENA 7 standard instrument departure has no designed positive separation method, making it susceptible to loss of separation occurrences.

Glossary