After landing on runway 27 at Melbourne during land and hold
short operations, VH-CZH, a Boeing 737, vacated the runway via the
parallel taxiway Echo which crossed runway 34 at a distance of
2,333 m from the threshold. The surface movement controller
instructed the crew to hold short of runway 34 because VH-OGK, a
Boeing 767, was landing.
VH-EAL, a Boeing 767, was taxiing for a runway 34 intersection
departure at taxiway Juliet, 773 m from the runway 34 threshold.
The co-pilot was the flying pilot. OGK had just landed on runway 34
and was vacating at the high-speed taxiway Foxtrot, 1,588 m from
the runway 34 threshold. The aerodrome controller instructed the
crew of EAL to line up and wait.
EAL's crew had noted VH-NKN, a Beech 1900, on final approach for
runway 27. When OGK was clear of runway 34, the aerodrome
controller cleared EAL for an immediate take-off. NKN was on a
practice instrument landing system approach to runway 27 and was
approximately at the outer marker. The aerodrome controller
requested the crew of NKN to reduce to minimum approach speed.
The pilot in command of CZH reported that he saw OGK vacate
runway 34 at taxiway Foxtrot and then received a clearance to cross
runway 34. As CZH began to cross the runway, the crew observed EAL
lining up with its landing lights on. At about one-half to
two-thirds of the way across runway 34, the co-pilot of CZH
commented to the pilot in command that it looked like EAL had
started to roll for take-off. The pilot in command confirmed this
and both pilots monitored EAL's progress. The forward section of
CZH was well clear of the runway but the rear section was believed
to be obstructing the runway when the crew noticed that EAL's
take-off had been rejected. Both pilots observed the spoilers of
the B767 extend.
At the time EAL was cleared for immediate take-off, its crew was
not aware that CZH was crossing 34 at taxiway Echo. As they started
to roll, the pilot in command saw that CZH had crossed about
two-thirds of the width of the runway and estimated it would be
well clear and so continued with the take-off. When the aircraft
was at about 90 kts, the pilot-in-command heard the instruction
"stop immediately" transmitted twice, took control from the
co-pilot, applied reverse thrust and slowed the aircraft before
exiting runway 34 at taxiway Foxtrot.
The controllers
The aerodrome controller was undergoing re-familiarisation
training under the supervision of a rated training officer. Both
controllers had extensive aerodrome control experience. The surface
movement controller had worked at Melbourne tower since April 1998
and was a rated surface movement controller. He was not trained in
aerodrome control at Melbourne.
The traffic management plan and outcome
The aerodrome controller had planned for CZH to cross runway 34
after OGK had turned to exit runway 34 via taxiway Foxtrot. A
conditional clearance was issued to the surface movement controller
to this effect. The conditional clearance was "after Qantas 33 has
vacated the runway, cross runway 34", which was acknowledged by the
surface movement controller. The training officer said that he was
not aware of the interchange. The aerodrome controller's plan,
which was endorsed by the training officer was to hold EAL in the
lined-up position on runway 34 while CZH crossed the runway and
while NKN landed on runway 27.
Although the training officer had endorsed the plan, the speed
of NKN on final for runway 27 was erratic and as a result, his
mental model changed. He perceived that there was an opportunity
for EAL to take off before NKN landed. The training officer
considered that the new plan was desirable because another aircraft
was on long final for runway 34 and there was a possibility that it
would have to go-around behind, or over EAL. The training officer
reported that he did not think that the aerodrome controller had
noticed the performance of NKN on final, which meant that the
opportunity for it to land and the plan to work was
diminishing.
The training officer conveyed the new plan to the aerodrome
controller, who then cleared EAL for an immediate take-off. The
aerodrome controller scanned the runway and noticed CZH crossing at
taxiway Echo. The training officer reported that he was not aware
that CZH had been cleared to cross runway 34 until after the
take-off clearance was issued to the crew of EAL. The controllers
both reported that they did not immediately cancel the take-off
clearance issued to EAL because they assessed that CZH would be
clear of the runway before EAL commenced the take-off roll. The
rationale for this decision was based on their interpretation of
Chapter 6 of the Manual of Air Traffic Services.
The aerodrome controller monitored the position of NKN, which
was "getting close". He did not feel comfortable with the
developing situation and instructed EAL to cancel departure. This
transmission was made 21 seconds after clearing EAL to take-off.
EAL started to roll and the aerodrome controller transmitted "EAL,
stop immediately". When EAL continued to accelerate, the aerodrome
controller transmitted again "EAL, stop immediately, stop
immediately." The crew acknowledged this transmission, applied
reverse thrust and slowed before exiting the runway at taxiway
Foxtrot. The controllers both reported that the motivator for the
cancellation of the take-off clearance was the potential for EAL to
conflict with NKN on final to runway 27, rather than the potential
for EAL to conflict with CZH, which was crossing on runway 34.
ATS procedures
The Manual of Air Traffic Services includes instructions for the
control of departing and arriving aircraft within the traffic
circuit and on the movement area of an aerodrome. Chapters 6 and 12
were relevant to this occurrence scenario.
