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

Local Safety Action

The aircraft operator, in its monthly company newsletter, highlighted the need to be vigilant when using non-standard levels and direct tracking, stating that, "each deviation from these standards removes a level of protection. Another reminder to be vigilant particularly when accepting/requesting deviations from standard."

The controllers approved route and level changes that eliminated effective separation assurance strategies.

Separation assurance with the northbound Dash 8 was lost when the crew of the southbound Dash 8 was assigned a non-standard flight level. The conflict would have been avoided had a standard level been assigned.

The Australian Advanced Air Traffic System provided several conflict recognition tools for use by controllers although none were used on this occasion. Such use may have brought the conflict to the attention of the controller prior to activation of the STCA.

Specific reference to the non-standard level of the southbound Dash 8 in the handover/takeover may have assisted with conflict recognition in advance of the need for avoiding action.

The use of the direct track created an opposite direction conflict with aircraft on the Gladstone -MLY track and eliminated the safeguard provided by segregated routes. Despite that, the BUR controller was not required to coordinate the direct track prior to the northbound Dash 8 entering KPL/LMA airspace. The KPL/LMA controller may have recognised the conflict had coordination been provided on the northbound Dash 8 prior to transfer of control.

Effective scanning by the KPL/LMA controller following the handover/takeover may have enabled the controller to identify the confliction. Controllers need to use scanning techniques that allow them to continually assess the changing traffic pattern for actual and potential conflictions. The effectiveness of the KPL/LMA controller's scanning technique may have been affected by:

His unsuccessful attempt to relax during his short holiday,
The early start time of the shift given his preference to sleep until mid morning, and
The sequencing discussion and subsequent actions.

The controller's concentration levels may have also been low due to the relatively low traffic levels at the time of the occurrence.

A de Havilland Canada Dash 8-102 (northbound Dash 8) was en
route from Brisbane to Gladstone at flight level (FL) 140. A second
de Havilland Canada Dash 8-102 (southbound Dash 8) was tracking
from Gladstone to Brisbane via Maleny (MLY) also at FL140. Those
routes placed the aircraft on reciprocal tracks with approximately
1.25 NM lateral displacement. The Keppel (KPL) and Alma (LMA)
sectors were combined. The controller was responsible for the
airspace that extended from approximately 80 NM north of Brisbane
to approximately 70 NM north of Rockhampton and from the coast to
approximately 90 NM to the west. The KPL/LMA sector controller
received a Short Term Conflict Alert (STCA) between the aircraft
when they were approximately 10 NM apart. The STCA was a collision
avoidance tool in The Australian Advanced Air Traffic System
(TAAATS). The controller instructed the crews of both aircraft to
turn 90 degrees to the right and issued traffic information to the
crew of the northbound Dash 8 about the southbound Dash 8. The
aircraft passed 5.4 NM abeam each other. The radar separation
standard was 5 NM. Each crew had the other aircraft in sight. There
was no infringement of separation standards.

Traffic levels at the time of the occurrence were considered
low. There were two aircraft to the northwest of Brisbane that
required the attention of, and coordination between, the KPL/LMA
controller and the Burnett (BUR) controller.

The KPL/LMA controller had assigned the crew of the southbound
Dash 8 FL190. The crew subsequently requested and was assigned
FL150. Eight minutes later, the crew requested "amended
non-standard FL140". Use of the standard levels for the track flown
would normally provide a degree of separation assurance between
aircraft. A non-standard level was a level that was not in
accordance with the table of cruising levels detailed in the Manual
of Air Traffic Services. The controller approved the crew's request
for the level change. Shortly after, the southbound Dash 8 was
maintaining FL140. The controller then conducted a
handover/takeover and another controller assumed responsibility for
the sectors.

The crew of the southbound Dash 8 reported a layer of stratus at
FL150 extending from Gladstone almost to Brisbane. The crew
requested FL140 to remain beneath the cloud and avoid any
associated turbulence; although the crew did not provide a reason
to the controller at the time of the request. Flight level 130 was
available and was the standard level but was not requested because
the crew thought the base of controlled airspace was FL130 in that
area and was therefore outside controlled airspace. The base of
controlled airspace was FL125. Flight level 130 would have kept the
aircraft within controlled airspace and would have provided a
minimum of 500ft vertical separation with aircraft operating
outside controlled airspace.

The crew of the northbound Dash 8 had been cleared to FL180 on
departure from Brisbane. The crew reported on climb to FL180 and
requested amended FL140 from the BUR sector controller. That
controller re-cleared the crew of the northbound Dash 8 at FL140, a
standard level. The controller also re-cleared the crew direct to
Gladstone when the aircraft was clear of conflicting traffic in the
BUR sector. Local instructions enabled controllers to approve
direct tracking subject to a number of conditions. One of those
conditions stated that direct tracks were available on "northbound
tracks that are east of and will not cross a line MLY-RK
[Rockhampton]: landing within the lateral limits of Fraser
airspace". The track of the northbound Dash 8 met those
requirements.

The BUR sector controller then transferred control
responsibility of the northbound Dash 8 to the KPL/LMA controller.
A transfer of control responsibility, or hand off, was performed
when one controller highlighted the subject aircraft on another
controller's Air Situation Display (ASD). The symbol then changed
colour to indicate the intention to transfer control
responsibility. The symbol changed colour again when control
responsibility had been accepted. Crews were instructed to change
to the next control frequency following acceptance of the hand off.
Following the hand off, the northbound Dash 8 entered KPL/LMA
sector. Both the northbound Dash 8 and the southbound Dash 8 were
maintaining FL140. Neither the KPL/LMA nor the BUR controllers were
required to voice coordinate level changes or changes in tracking.
That information was entered into TAAATS by the responsible
controller and was updated automatically at all relevant
consoles.

The assignment of the non-standard level to the southbound Dash
8 was not considered significant by the first KPL/LMA controller
because the aircraft was within radar coverage. There was a general
awareness of standard levels among the KPL/LMA controllers
interviewed, but none considered the use of standard levels
essential for aircraft within radar coverage. The use of standard
levels often did not achieve separation assurance because much of
the sector's traffic climbed and descended into and out of coastal
ports and controllers had to monitor aircraft altitude or levels to
ensure vertical separation was maintained. The controller assigned
FL140 to the southbound Dash 8 as there were no conflictions at
that time and the use of a non-standard level was not uncommon.

The second controller believed he had missed the significance of
the non-standard level because he had not issued the level himself
and did not use any scanning techniques after the takeover that may
have highlighted the conflict. He advised that he would have
normally highlighted the label of an aircraft at a non-standard
level using the individual quick look (IQL) function available on
TAAATS. The IQL function was used to check hidden track label
details but also changed the colour of a label on an individual
console. The controller could not recall whether the first
controller had drawn his attention to the non-standard level during
the handover/takeover. The first controller did not believe he had
mentioned the non-standard level during the handover/takeover.

The use of direct tracking by the BUR controller meant that the
northbound Dash 8 would require either a different level or radar
vectoring to maintain separation with the southbound Dash 8. The
flight-planned route for northbound traffic provided a segregated
two-way route structure between southbound aircraft on the
Gladstone-Maleny track, and northbound traffic. However, the
segregated two-way route structure was not usually used because
direct tracking provided separation assurance between succeeding
northbound aircraft departing Brisbane and facilitated traffic
management along the coast.

The southbound Dash 8 had maintained FL140 for approximately
twelve minutes prior to the time the KPL/LMA controller received
the STCA. The crew of the northbound Dash 8 had reported
maintaining FL140 three minutes prior to the time the KPL/LMA
controller received the STCA.

The KPL/LMA controller reported that he had maintained radar
surveillance, had not been distracted and was aware of both
aircraft. The controller was fit for work and all equipment was
serviceable. The controller advised however, that he had taken his
family on a short trip to relax. He had returned two days before
the occurrence but had been unable to relax. He also stated that he
usually stayed up late at night and preferred to sleep until
mid-morning. The night before the occurrence the controller stayed
up until midnight but had awoken in sufficient time to commence
duty at 7:00am on the day of the occurrence. He also reported that
he had been discussing the inbound sequence with other controllers
immediately prior to the occurrence.