VH-CZA, a Boeing 737, was inbound to Brisbane and was being sequenced to follow VH-EWM, a BAe 146, for a visual approach to runway 19 via left base. Both aircraft were under the control of the Brisbane Approach radar controller and were being processed via the Coolangatta One Standard Terminal Arrival (STAR). VH-TNU, a Dash 8, was behind CZA and was being processed via the Jacob's Well Four STAR.
The Brisbane Flow Controller had originally assigned TNU to land on runway 14. This required the controller to position the aircraft east of the Jacob's Well - Brisbane track, and for the crew to track direct to the Brisbane Control Tower before joining right base for runway 14. There were two light aircraft operating to the south and southeast of the aerodrome at 1,500 ft on traffic survey work. The controller assessed that these aircraft may have conflicted with TNU overflying the aerodrome for runway 14. As well, there was departing traffic that he considered might also have conflicted with TNU being processed for runway 14. As a result, the controller decided to process TNU for runway 19.
The controller vectored TNU north to a position approximately abeam and above CZA and informed the crew that they were following the traffic which was low and to their right. The crew of TNU advised that they were still in cloud. At this time, TNU was approaching 5,000 ft heading 360 degrees M and CZA was descending through 3,500 ft, heading 310 degrees M. The controller then asked the crew of CZA to fly a close left base, and advised that they were following a blue and white BAe 146 aircraft (EWM) which was over St Helena Island on left base for runway 19. A short time later, the crew of TNU reported visual. The controller acknowledged this transmission and then instructed EWM to contact the tower.
After making a number of transmissions to other traffic, the controller instructed TNU to turn left heading 310 and to descend to 2,500 ft. He asked the crew if they still had the B737 in sight, adding that it was in their 10 o'clock position at 3 NM. The controller instructed CZA to descend to 1,500 ft. The crew of CZA then reported visual and were cleared by the controller for a visual approach via a close left base. After CZA acknowledged this clearance, the crew of TNU reported that they had the traffic sighted. The controller responded that CZA was for a close left base and cleared TNU for a visual approach. He then instructed CZA to contact the tower and asked the crew of TNU to closely follow CZA. The controller then processed a departing aircraft and accepted the transfer of another inbound aircraft onto his frequency. A turn instruction he gave this aircraft was not initially understood and required two further transmissions for clarification. As this exchange concluded, the controller asked the crew of TNU to confirm that they still had visual contact with the B737. The crew responded that they believed that the B737 had landed. The controller immediately instructed TNU to turn right. He then confirmed with the tower controller that TNU was turning away from CZA. CZA subsequently landed normally on runway 19 and TNU was processed for landing on runway 14.
Recorded radar data indicated that the minimum separation between the aircraft was about 200 ft vertically, and 0.8 NM horizontally. This occurred as TNU was instructed by the approach controller to turn away from CZA. The required separation standard in the circumstances was 1,000 ft vertically or 3 NM horizontally. The data also showed that, at the time CZA was given as traffic to TNU, the groundspeed of CZA was 143 kts while that of TNU was 243 kts. When the crew of TNU reported sighting the traffic, the position of CZA relative to TNU was between 7 and 8 o'clock at about 3 NM rather than 10 o'clock as the controller had indicated a short time earlier. At this time, EWM was at about a 10 o'clock position relative to TNU but at a range of 7 NM.
A review of the automatic voice recording of communications between the approach controller, the aircraft, and other agencies confirmed that there was no request from the control tower for TNU to be processed for runway 14. It also confirmed that the crew of TNU was not given their number in the landing sequence.
Neither TNU, nor CZA, was fitted with a traffic collision avoidance system (TCAS).
The controller involved was highly experienced. He gained his initial ATC ratings in June 1980. He had been rated and endorsed to perform the radar approach controller duties since April 1990.
The incident occurred two hours after he had commenced duty on the Approach South position. The controller stated that he did not consider the traffic levels and/or workload to be unusually high at the time of the incident. He indicated that he changed the traffic sequence with respect to TNU to reduce his workload and improve traffic management for both himself and the tower.
Information from the crew of VH-TNU
The technical crew of TNU said that, in hindsight, they did not sight CZA at any stage during the sequence. Their report to the controller that they believed the aircraft had landed indicated that they had mis-identified EWM as CZA. The vectors they had been given placed the aircraft high and fast on the descent profile. This, coupled with the checklist actions and the request to sight the traffic, created a high cockpit workload situation. Neither pilot could recall being given their number in the landing sequence.
The cabin flight attendant on TNU became aware of CZA when she saw it through a passenger window as she completed the cabin pre-landing checks. She felt some concern regarding the proximity of the aircraft and considered entering the cockpit to confirm that the pilots knew of its presence. In the event, she decided to take no action, as she felt confident that they would have been aware of the situation.
Brisbane arrival procedures
The management of air traffic in the Brisbane Terminal Area (TMA) involved the formulation of a traffic management plan for arriving and departing aircraft. The Terminal Approach Coordinator (TAC) decided upon the plan after liaison with the Traffic Management Coordinator (TMC) in the control tower. Its purpose was to determine the most efficient use of available runways and types of approaches consistent with prevailing weather conditions and traffic density and patterns. Once the plan was agreed, the TAC directed the Flow Controller to sequence the arriving traffic in accordance with the traffic management plan. The task of the radar approach controller was to direct aircraft in accordance with the plan to ensure that aircraft arrived in sequence at appropriate intervals for efficient traffic flow.
In order to make the best use of the available runways and minimise delays, procedures had been developed to assist controllers with arriving aircraft required to overfly the aerodrome from the south for runway 14. These procedures were detailed in Northern District Local Instructions TMA 27, and were designed to assist in minimising workload on both the approach and control tower controllers by providing a standardised technique which allowed departing aircraft to depart and remain clear of the arriving overflying traffic. The instruction stated:
In the case of RWY 19/01 and an arrival from the east/southeast for landing RWY 14, the following shall apply. The arrival shall be positioned east of the JCW-BN VOR track, tracking direct to the CONTROL TOWER assigned A020 and for the ACFT to be on TWR frequency no later than 5NM with no restrictions.
These tracking requirements will ensure that a RWY 19 LAV SID can proceed unrestricted.
Sight and Follow procedures
At the time of the occurrence, visual separation standards were detailed in the Manual of Air Traffic Services (MATS) Chapter 4, Section 8. Air traffic controllers could use the visual separation standard to separate aircraft flying at or below FL125. However, if this standard was used an instruction to maintain visual separation with, or to follow other aircraft, should have been issued in accordance with requirements of MATS Chapter 6 Section 4. Chapter 8 of MATS, "Enroute/Approach Control", did not make reference to sight and follow procedures.
In the circumstances, the controller's decision to change the assigned runway for TNU was inappropriate and not in accordance with Local Instructions. It resulted in additional workload by way of the vectoring instructions, as well as the setting up of the sight and follow procedure, for TNU. There were other options for reducing workload such as vectoring the traffic survey aircraft away from the area. Ultimately, the decision set the scene for the conflict to develop.
The information the controller gave the crew of TNU concerning the aircraft they were to sight and follow was incomplete. Because the crew was not given its number in the approach sequence, there was no reason for other than one aircraft ahead to be sighted. Also, because of the speed differential between the two aircraft, the azimuth information provided by the controller rapidly became inaccurate. These oversights resulted in the misidentification by the crew of TNU of EWM as CZA.
The report by the crew that the traffic had been sighted, and the immediate acceptance by the controller of this information, was, in effect, one assumption reinforcing another. In other words, the crew said what the controller wanted to hear. This had two main effects. It:
- confirmed to the crew that they had correctly identified the traffic, effectively implying that there was no other potentially conflicting traffic, and
- it enabled the controller to divert his attention away from TNU and CZA to the control of other traffic.
Had either TNU or CZA been traffic alert and collision avoidance system equipped, it is likely that either or both crews would have become aware of the confliction before separation standards were infringed. It is also probable that the seriousness of the occurrence would have been less if the TNU cabin crewmember had reported her observation of CZA to the flight deck crew.
- The approach controller changed the approach sequence for TNU.
- The sight and follow instructions issued to TNU provided insufficient and inaccurate information.
- The crew of TNU misidentified EWM as CZA.
- Neither TNU nor CZA was equipped with TCAS.
Shortly after the incident, the operator of TNU published a memorandum to all company flight crew. It included a description of the event and the lessons to be drawn from it and was published in the March 1999 Issue of Asia Pacific Air Safety under the title "Follow your instincts".
As a result of its response to the occurrence, Airservices Australia held meetings at which the circumstances of the incident, with specific reference to the requirements of sight and follow procedures, were discussed amongst controllers. Additionally, Airservices examined the need for cross-referencing the sight and follow procedures in Chapter 6 Section 4 of MATS with Chapter 8 of MATS. Following this examination, sight and follow procedures were removed and visual separation procedures were revised through Amendment List 23 dated 3 December 1998 of MATS.
|Date:||03 August 1998||Investigation status:||Completed|
|Time:||0755 hours EST|
|Location:||13 km E Brisbane, Aero.|
|State:||Queensland||Occurrence type:||Loss of separation|
|Release date:||20 August 1999||Occurrence category:||Incident|
|Report status:||Final||Highest injury level:||None|
Aircraft 1 details
|Aircraft manufacturer||de Havilland Canada|
|Type of operation||Air Transport Low Capacity|
|Damage to aircraft||Nil|
|Departure point||Williamtown, NSW|
Aircraft 2 details
|Aircraft manufacturer||The Boeing Company|
|Type of operation||Air Transport High Capacity|
|Damage to aircraft||Nil|
|Departure point||Sydney, NSW|