Aviation safety investigations & reports

Boeing Co 767-238, VH-EAL

Investigation number:
199803972
Status: Completed
Investigation completed

Summary

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.

Analysis

The investigation revealed that the local practice for issuing a conditional clearance for a taxiing aircraft to cross an active runway might have been deficient. When a taxiing aircraft needed to cross an active runway, coordination was required between the surface movement controller and the aerodrome controller. If traffic conditions permitted, it may have been possible to issue the taxiing aircraft with an immediate clearance to cross the active runway. However, at other times, a taxiing aircraft may have been issued with a conditional clearance, authorising it, for example to cross the active runway after a landing aircraft had vacated the runway.

When a conditional crossing clearance had been issued, the continued safe operation of the system was dependent on both the surface movement controller and the aerodrome controller remembering that this traffic coordination had been arranged and was still pending. Interviews with controllers and observation of current work practices indicated that the coordination between the surface movement controller and the aerodrome controller for conditional clearances was verbal only. Neither controller used any form of memory aid to record the fact that a conditional clearance had been issued and was still pending. In this occurrence, this led the aerodrome controller, at a time of high workload and possible stress, to forget that a conditional crossing clearance was pending.

In addition, the training officer was not aware that a clearance had been coordinated between the surface movement controller and the aerodrome controller. Because the system did not provide any physical record that a conditional clearance was pending, there was no cue to alert the training officer to the fact that this was the case.

The use of memory markers recording actions by annotation or other means, assists controllers in remembering vital operational information in two ways. Firstly, the associated actions that the controller carries out in setting the memory marker assist in the consolidation of a strong memory trace. Secondly, the marker can be checked at any time by the controllers if they are uncertain of the current status of the item or condition that it refers to.

Significant Factors

  1. A conditional clearance authorising the surface movement controller to clear CZH to cross runway 34 was issued to the surface movement controller by the aerodrome controller.
  2. The aerodrome controller's training officer was not aware that a conditional clearance was active when he instructed the aerodrome controller to clear EAL for take off.
  3. There was no tactile memory marker alerting the controllers that an aircraft had been cleared to cross an active runway.
  4. The aerodrome controller did not scan runway 34 before issuing the take-off clearance.
  5. Neither the aerodrome controller nor the training officer cancelled EAL's take-off clearance when they became aware that CZH was crossing runway 34.

Safety Action

As a result of this and other occurrences, the Bureau of Air Safety Investigation is investigating two perceived safety deficiencies. The first relates to the use of conditional clearances for runway entry and runway crossings by vehicles and aircraft, and the procedures used by air traffic controllers to alert themselves that vehicles and aircraft are on an active runway. The second relates to the inappropriate use of paragraph 29 of the Manual of Air Traffic Services 6-2-3 by aerodrome controllers.

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

General details
Date: 23 September 1998   Investigation status: Completed  
Time: 0822 hours EST    
Location   (show map): Melbourne, Aero.    
State: Victoria   Occurrence type: Separation issue  
Release date: 10 December 1999   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft 1 details

Aircraft 1 details
Aircraft manufacturer The Boeing Company  
Aircraft model 767  
Aircraft registration VH-EAL  
Serial number 23306  
Type of operation Air Transport High Capacity  
Damage to aircraft Nil  
Departure point Melbourne, VIC  
Destination Sydney, NSW  

Aircraft 2 details

Aircraft 2 details
Aircraft manufacturer Beech Aircraft Corp  
Aircraft model 1900  
Aircraft registration VH-NKN  
Type of operation Air Transport Low Capacity  
Damage to aircraft Nil  
Departure point Williamtown, NSW  
Departure time 0615 hours EST  
Destination Melbourne, VIC  

Aircraft 3 details

Aircraft 3 details
Aircraft manufacturer The Boeing Company  
Aircraft model 737  
Aircraft registration VH-CZH  
Serial number 23660  
Type of operation Air Transport High Capacity  
Damage to aircraft Nil  
Departure point Adelaide, SA  
Destination Melbourne, VIC  
Last update 13 May 2014