de Havilland Canada DHC-8-102 , VH-TNU

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.

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.

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.

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

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.