Aviation safety investigations & reports

Loss of separation involving Airbus A330, VH-EBJ, and Boeing 737, VH-VZO, near Sydney Airport, New South Wales, on 5 August 2019

Investigation number:
AO-2019-041
Status: Active
Investigation in progress

Preliminary report

Preliminary report 16 January 2020

Sequence of events

On the night of 5 August 2019, at 1831:45 Eastern Standard Time[1], an Airbus A330-300 (A330) aircraft, registered VH-EBJ and operated by Qantas Airways, was cleared by air traffic control (ATC) for take-off from runway 34 right (34R) at Sydney Airport, New South Wales. At that time, a Boeing 737-800 (737) aircraft, registered VH‑VZO and operated by Qantas Airways, was on final approach to the same runway.

A trainee controller was operating the Sydney aerodrome controller east (ADC-E) ATC position, under the supervision of an on-the-job training instructor (OJTI).

The ADC-E controller assessed that there would be insufficient runway spacing between the aircraft and instructed the 737 flight crew to ‘go around’. As the 737 flight crew conducted the missed approach, a loss of separation occurred between their aircraft and the departing A330. Flight data showed that separation between the aircraft reduced to about 0.43 NM laterally and about 500 ft vertically (Figure 1).

Figure 1: A330 and 737 flight paths and indication of the area of minimum separation

Figure 1: A330 and 737 flight paths and indication of the area of minimum separation

Source: Google earth overlaid with Qantas Airways flight data. Annotated by ATSB

The ADC-E controller reported that he had both aircraft in sight. In an attempt to increase separation between the two aircraft, he instructed the 737 flight crew to turn further right. The 737 was then at about 980 ft, which was below the minimum vectoring altitude (at night). As both aircraft converged, the A330 flight crew received a traffic advisory alert from their aircraft’s airborne collision avoidance system (ACAS). The A330 first officer, who was pilot flying,[2] then saw the 737 in close proximity and, in response, reduced the aircraft’s angle of bank to reduce the turn towards the 737. The captain of the A330 made a radio transmission to advise the ADC-E controller that it was ‘very close’. The controller then issued an instruction to the A330 flight crew to turn left.

The A330 climbed to 5,000 ft and continued to Melbourne without further incident. The 737 climbed to 3,000 ft and was issued radar vectors for a second approach to runway 34R. It landed without further incident a short time later.

Table 1 provides a more detailed summary of the sequence of events.

Table 1: Summary of key events

Time

Event

1831:04

The ADC-E instructed the A330 flight crew to line up runway 34R. The 737 was on final approach at about 2.8 NM.

1831:10

The ADC-E instructed the 737 flight crew to maintain minimum speed. The 737 flight crew responded that they were already at minimum speed.

1831:21

The ADC-E instructed the A330 to expedite lining up and to be ready for an immediate take-off. The ADC‑E was waiting for a turboprop aircraft, which had just landed on runway 34R, to taxi clear of the runway.

1831:45

Once the turboprop aircraft was clear of runway 34R, ADC-E cleared the A330 for immediate take-off.

1831:58

The ADC-E assessed that the runway separation standard would not be maintained at the time the 737 crossed the threshold of runway 34R. He instructed the 737 flight crew to go around. The A330 was still in its take-off roll and the 737 was at about 400 ft.

1832:30

The 737 was climbing through about 920 ft still on runway track (335°). The A330 was becoming airborne on runway track (335°).

1832:38

The ADC-E instructed the 737 flight crew to turn right onto heading 100°. Flight data showed the 737 flight crew commenced the right turn when passing about 1,300 ft AGL. At that time the aircraft was approximately 1,500 m north of the runway threshold. The A330 was in a climbing right turn tracking on the MARUB 6 standard instrument departure. The projected flight paths of the two aircraft were then converging.

1832:50

The A330 flight crew received an ACAS traffic advisory alert (‘TRAFFIC TRAFFIC’). The A330 first officer looked out the right cockpit window and sighted the 737 above in a climbing turn and in close proximity.

1833:03

The ADC-E instructed the 737 flight crew to turn further right onto heading 120°.

1833:09

The ADC-E instructed the 737 flight crew to climb to 3,000 ft.

1833:17

The A330 captain made a radio transmission saying ‘that was very close’.

1833:23

The ADC-E instructed the A330 to turn left heading 100°. Both aircraft were then on diverging flight paths.

 

Standard instrument departures and approaches

Standard instrument departures (SIDs) and instrument approaches are charted procedures that flight crews must follow when departing or landing at suitably-equipped aerodromes.

ATC had cleared the A330 flight crew to depart from runway 34R on the MARUB 6 SID (Figure 2). The design of that SID required flight crew to climb on the runway track (335°) to 500 ft and then turn right to intercept the 075° track to waypoint MARUB.

Figure 2: MARUB 6 standard instrument departure from runway 34R

Figure 2: MARUB 6 standard instrument departure from runway 34R. Source: Qantas Airways

Source: Qantas Airways

Prior to descent into Sydney, ATC had cleared the 737 flight crew to conduct a global navigation satellite system landing system (GLS) approach to runway 34R. In the event of a go-around, Airservices Aeronautical Information Publication Australia (AIP) 2.14.2 (Go Around and Missed Approach Procedure in VMC) stated that at Sydney visual go-arounds must be carried out in accordance with the GLS or instrument landing system (ILS) missed approach procedure for the runway the aircraft was using, or as directed by ATC.

When the ADC-E instructed the 737 flight crew to go around, the aircraft was descending through about 400 ft. The missed approach procedure for the GLS runway 34R required the flight crew to maintain the runway track (335°) until 600 ft and then turn right, track 070° and climb to 2,000 ft (Figure 3). Flight data showed the 737 flight crew commenced the right turn when climbing through about 1,300 ft AGL (above ground level). At that time the aircraft was approximately 1,500 m north of the runway threshold.

A missed approach procedure is designed for each instrument approach to provide aircraft with terrain and obstacle clearance during a go-around. A missed approach point (MAP) is a point where flight crew must initiate a missed approach if suitable visual references are not available to make a safe landing or the aeroplane is not in a position to make a safe landing.

For ILS and GLS approaches, the decision height (DA) in conjunction with the glide slope (G/S) is used to determine the MAP. The DA and MAP are annotated on the approach chart (Figure 3).

From the MAP, flight crews are required to navigate their aircraft in accordance with the applicable published missed approach procedure unless directed otherwise by ATC.

Figure 3: GLS approach runway 34R

Figure 3: GLS approach runway 34R. Source: Qantas Airways annotated by ATSB

Source: Qantas Airways annotated by ATSB

The MARUB 6 SID runway 34R and the missed approach flight path for the GLS approach runway 34R both required flight crew to make an early right turn and track to the east of Sydney Airport.

As in this occurrence, should an aircraft be departing on the MARUB 6 SID at the same time an aircraft conducts a go-around from runway 34R, both aircraft will track out to the east. There is potential that those flight paths will conflict and require intervention from ATC in order to ensure separation is maintained between the aircraft.

Aircraft flight management systems

Modern commercial aircraft are generally fitted with a flight management system (FMS) or similar system. A FMS uses a variety of sensors to determine the aircraft’s current position and then sends guidance commands to the aircraft control systems to navigate it along the flight path programmed by the flight crew.

An FMS has a worldwide navigation database that is coded with published instrument procedures including missed approach procedures. The navigation database allows an FMS to create a continuous display of navigational data to flight crew. Vertical navigation guidance can also be coded and displayed. Any discrepancies in a navigation database may lead to flight crew not following the correct flight path.

Air traffic control information

Separation standards refer to the minimum distance or time apart that aircraft operating in controlled airspace and at Class C[3] airports must be kept. These are outlined in the Manual of Standards for Air Traffic Services and air traffic controllers use them to safely manage air traffic.

Air traffic controllers must keep aircraft separated vertically or horizontally. When the separation between two or more aircraft is less than the standard, there is a loss of separation.

A surveillance separation standard is used when aircraft position information is derived from air traffic services’ surveillance systems (including radar). When aircraft are operating inside terminal area airspace, such as Sydney, controllers must maintain a minimum separation between aircraft of 3 NM laterally or 1,000 ft vertically. That standard of separation may be reduced by a tower controller when using visual observation.

A runway separation standard is applied for aircraft landing and taking off from the same runway. The standards required that an aircraft landing behind a departing aircraft cannot cross the runway threshold until the preceding aircraft is airborne and:

  • has either commenced a turn, or
  • is beyond the point on the runway at which a landing aircraft could be expected to complete its landing roll and there is sufficient distance to enable the landing aircraft to manoeuvre safely in the event of a missed approach.

In this case, the ADC-E ensured runway separation standard was not infringed by instructing the 737 flight crew to go-around.

Aerodrome controllers (ADCs) may reduce the radar separation minima in the vicinity of aerodromes when adequate separation can be provided using visual observation and each aircraft is continuously visible to the ADC. However, ADCs are not permitted to provide visual separation if the projected flight paths of the aircraft conflict.

In this case, the ADC-E and his supervising OJTI stated they had the two aircraft sighted and applied visual separation. At night or in instrument meterological conditons, ATC maintains responsibility for terrain clearance when an aircraft is being radar vectored. When the ADC-E issued a radar vector (at night) to the 737, the aircraft was still below the minimum vector altitude, therefore terrain separation was not maintained.

When a loss of separation occurs, compromised separation recovery procedures are required to be applied to reduce the risk of a collision. A controller is required to issue safety alerts to pilots of aircraft as a priority when a controller becomes aware that aircraft are considered to be in an unsafe proximity to each other. In this case, no safety alert was issued by either the ADC-E or OJTI as both controllers considered visual separation existed.

The ADC-E trainee was an experienced controller. He had previously worked as an ADC in another tower and had a surface movement controller rating at Sydney. At the time of the occurrence, he had neared the end of his training for the Sydney ADC-E position, with his performance check to obtain his rating scheduled for the next day. Both the ADC-E and OJTI had completed compromised separation recovery training.

Further investigation

The investigation is continuing and will include examination of:

  • design and risk assessment of MARUB standard instrument departures and missed approaches from runway 34 right
  • air traffic control procedures, controller training and controller actions
  • 737 and A330 operator’s procedures and flight crew actions
  • coding of flight management system navigation databases
  • further analysis of flight data recordings and ATC recordings.

 

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The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this preliminary report. As such, no analysis or findings are included in this update.

 

__________

  1. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.
  2. Pilot Flying (PF) and Pilot Monitoring (PM): procedurally assigned roles with specifically assigned duties at specific stages of a flight. The PF does most of the flying, except in defined circumstances; such as planning for descent, approach and landing. The PM carries out support duties and monitors the PF’s actions and the aircraft’s flight path.
  3. This is the controlled airspace surrounding major airports. Both instrument flight rules (IFR) and visual flight rules (VFR) flights are permitted and must communicate with air traffic control.

Initial summary

Initial summary: 9 August 2019

The ATSB is investigating a loss of separation involving an Airbus A330 (registered VH-EBJ) and a Boeing 737 (registered VH-VZO), near Sydney Airport, New South Wales, on 5 August 2019.

VH-EBJ was lined up ready for departure on runway 34R and VH-VZO was on final approach to runway 34R. After the previous landing aircraft had cleared the runway, the air traffic controller cleared VH-EBJ for immediate take-off. Shortly after, the flight crew of VH-VZO were issued a late instruction to go around as the runway separation standard could not be assured.

The controller instructed the flight crew of VH-VZO to turn on to an easterly heading and climb to provide separation with VH-EBJ as that aircraft became airborne. However, the turn instruction provided to the flight crew of VH-VZO conflicted with the departure track of VH-EBJ, which was on a standard instrument departure. 

The flight crew of VH-EBJ subsequently received a traffic collision avoidance system traffic alert.

The evidence collection phase of the investigation will include interviewing the air traffic controllers and flight crew, and reviewing recorded surveillance and flight data.

A final report will be released at the conclusion of the investigation. Should a critical safety issue be identified during the course of the investigation, the ATSB will immediately notify relevant parties so appropriate safety action can be taken.

General details
Date: 05 August 2019   Investigation status: Active  
Time: 1832 EST   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): near Sydney Airport   Investigation phase: Examination and analysis  
State: New South Wales   Occurrence type: Loss of separation  
Release date: 16 January 2020   Occurrence category: Serious Incident  
Report status: Preliminary   Highest injury level: None  
Anticipated completion: 1st Quarter 2021    

Aircraft 1 details

Aircraft 1 details
Aircraft manufacturer Airbus  
Aircraft model A330-202  
Aircraft registration VH-EBJ  
Serial number 0940  
Operator Qantas Airways  
Type of operation Air Transport High Capacity  
Sector Jet  
Damage to aircraft Nil  
Departure point Sydney, NSW  
Destination Melbourne, Victoria  

Aircraft 2 details

Aircraft 2 details
Aircraft manufacturer The Boeing Company  
Aircraft model 737-838  
Aircraft registration VH-VZO  
Serial number 34191  
Operator Qantas Airways  
Type of operation Air Transport High Capacity  
Sector Jet  
Damage to aircraft Nil  
Departure point Brisbane, Queensland  
Destination Sydney, NSW  
Last update 20 July 2020