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.