Boeing Co 737-377 , VH-CZO

As a result of this occurrence, the Bureau of Air Safety Investigation is currently investigating two safety deficiencies. The first relates to the inappropriate use of MATS 6-2-3 paragraph 32 by aerodrome controllers. The second relates to the non-application of MATS 6-3-1 paragraph 2 by controllers employed in the Brisbane aerodrome control tower.

Any safety output issued as a result of these analyses will be published in the Bureau's Quarterly Safety Deficiency Report.

The controller did not withhold the take-off clearance for CZO when there was no reasonable assurance that separation would exist between the aircraft when CZO commenced the take-off roll.
The lack of visibility of the A4S taxiway at night from the control tower required that aerodrome controllers instruct pilots to confirm when clear of the runway.

The difficulty in accurately locating aircraft on the high speed
taxiway A4S at night from the control tower is evidenced by the
controller twice assuming that OGG had departed the runway and
entered the taxiway. The awareness among local controllers of this
difficulty should have encouraged the use of procedures to ensure
the maintenance of required standards. However, the controller only
recognised that his visual assessment was incorrect when advised by
the crew of OGG. It is likely that the controller subsequently
assessed that as CZO had not lined up, it was not necessary to
cancel the clearance, but the two aircraft should simply be
monitored.

The procedures relating to take-off clearances permitted a
degree of discretion by the controller. However, that discretion
was conditional upon a valid determination of collision risk and
the maintenance of separation standards. Consequently, MATS 6-2-3
paragraph 32 was not appropriate to the issuing of the take-off
clearance, as the controller had not positively identified the
relative positions of the aircraft.

The aerodrome controller cleared VH-CZO for a night-time takeoff
from the Brisbane runway 01, believing that VH-OGG, after landing,
had vacated the runway onto the high-speed taxiway A4S. At the
time, CZO was at the A7 holding point. The crew of OGG alerted the
controller (and the crew of CZO) that they were on the active
runway. Shortly after, the controller asked the crew to confirm
that they were on taxiway A4S and was advised that they were not.
Aware that CZO had not lined up on the runway, the controller did
not cancel the take-off clearance, but monitored the situation
until OGG vacated the runway at taxiway A4.

The high-speed taxiway A4S was 1,900 m from the runway 01
threshold, and taxiway A4 was 2,310 m from the 01 threshold.
Taxiway A4 required that the crew turn the aircraft through 90
degrees to exit the runway.

Taxiway A4S was equipped with uni-directional centreline
lighting, which was not visible from the control tower. This made
it difficult in conditions of reduced visibility for controllers to
determine that an aircraft had vacated the runway and was on the
high-speed taxiway. However, in visual meteorological conditions at
night, it was not normal practice for controllers to ask crews to
report when their aircraft was clear of the runway.

The Manual of Air Traffic Services (MATS) 6-3-1 paragraph 2
stated:

"When take-off or landing separation is based on the
position of the preceding landing or taxiing aircraft and visual
determination, particularly at night or in reduced visibility, is
limited by poor azimuth resolution or other factors, the pilot of
that aircraft shall be instructed to report when the aircraft has:

crossed and is clear of a runway intersection; or

stopped short of a runway strip; or

vacated the runway."

The MATS 6-2-3, paragraph 31 stated:

"Before clearing an aircraft for take-off, and
immediately before take-off is commenced, the tower controller
shall make a visual check from the control tower to determine as
far as practicable, that the take-off path is not obstructed. If
the take-off path is obstructed, take-off clearance shall be
withheld or cancelled as appropriate, until the obstruction no
longer exists."

The prescribed separation standard was detailed in MATS 6-3-4
paragraph 24. The standard required that a departing aircraft shall
not be permitted to commence take-off until the landing aircraft
has vacated and is taxiing away from the runway.

The controller cleared CZO for takeoff using the provisions of
MATS 6-2-3 paragraph 32. This paragraph stated:

"Take-off clearance need not be withheld until
prescribed separation exists if, in the opinion of the controller,
no collision risk exists and there is reasonable assurance that
separation will exist when the aircraft commences take-off
roll."