Loss of separation

1. The attention of the pilot under training was partially diverted from safely taxiing the aircraft due to his pre-occupation with a previous event.
2. The training captain did not provide a timely warning to the pilot under training that he had passed the correct taxiway and was approaching an active runway.

The task of taxiing the aircraft after landing was not particularly demanding. The night was fine and clear, there were no works in progress, and both pilots of the Metro were familiar with the airport layout. However, it was apparent that the attention of the pilot under training was partially diverted from taxiing the aircraft by his pre-occupation with how he had performed during the practice ILS approach. The result was that he then mistakenly believed the aircraft was still approaching the entry to taxiway Bravo, when in fact the aircraft had passed that point and was approaching runway 34L.

The training captain noticed that the aircraft had passed the entry to taxiway Bravo, and was about to query the pilot under training when he noticed the other aircraft landing on runway 34L. In hindsight, he should have alerted the pilot under training when it became apparent that the aircraft was not beginning to turn into taxiway Bravo.

Although it was reasonable to have expected the crew of the Metro to enter taxiway Bravo after correctly reading back their taxi clearance, the vigilance and prompt action of the tower controllers acted as a final safety defence to stop the aircraft from entering the runway.

1. The considerable number of changes and staff issues within the Ocean sectors in the period prior to the occurrence.
2. The lack of a procedure to assist rated controllers to develop an inter-group training program.
3. The inadequate preparation of the group leader for on-the-job training.
4. The lack of a training pre-brief by the group leader and the sector controller.
5. The approval of the use of non-standard level by the B767.
6. The inability of the group leader to maintain an appreciation of the traffic disposition.
7. The lack of controller pilot datalink training aids and the inadequate installation of the facility at the console.
8. The distraction and subsequent failure of the sector controller to regularly scan the flight progress strips.

Organisational aspects

The group leader had a number of projects and staff issues that had to be addressed and that were constraining his ability to effectively manage the Ocean sectors. Taken individually these issues were probably not significant, but collectively they established the environment in which the Group was required to operate. The en-route manager and the group leader developed a plan to overcome these issues and in the long term develop staff in the Ocean sectors. Part of this plan was for the group leader to train for and obtain Ocean sector endorsements.

Training plan

The group leader developed a revised training plan that was constrained by staff commitments and scheduled ab initio training. However, he was not aware of the differences in the operation of sector 8 in comparison to other procedural sectors. Had he undertaken the classroom or simulator training prior to on the job training, he probably would have had an understanding of the unique aspects and a better overall understanding of the operation of the sector.

The group leader and the nominated supervising controller had only spent a short time together but the latter was aware of the training aspects that had been covered up to the morning of the occurrence. Because of this aspect he probably had a better appreciation than the sector controller did of the group leader's ability. Consequently, he would have been in a better position to recognise that the trainee was not maintaining the traffic situation. He might have been able to assume control of the position at a sufficiently early stage to recognise the conflict.

The current training guide and workbook were based on training ab initio controllers. There was no procedure to assist controllers from another group to modify the training to suit their specific requirements. There would appear to be scope for development of a process for peer review of revised training programs that would ensure that essential training aspects are included in a program.

Supervising controller

The sector controller that offered to supervise the group leader was unaware of the trainee's level of sector knowledge. They did not pre-brief and consequently they probably both had different expectations as to the level of participation of the other in the operation of the sector. This aspect in conjunction with his operation of the controller pilot datalink probably caused the sector controller to be distracted to the extent that he was unable to maintain an adequate scan of the flight progress strips.

Flight progress board management

The approval for the B767 to operate at a non-standard level for the track flown cancelled the defence normally provided to the air traffic system by the use of standard levels.

Controller pilot datalink facilities

The lack of a controller pilot datalink training guide or training aid provides an opportunity for controllers to become distracted to the detriment of the management of aircraft separation. Controllers should be able to develop their controller pilot datalink system skills remote from the operating position.

Operating position

The positioning of the controller pilot datalink and the sector 8 operating console restrict the ability of controllers to maintain an effective scan of the flight progress strip board. Controllers are required to divert their gaze and attention from the board to operate the controller pilot datalink keyboard. Modification of the console layout to enable more ready access to the controller pilot datalink or alternatively, provision of a controller to operate the controller pilot datalink during busy traffic periods would alleviate the problem.

1. Appropriate separation assurance techniques were not implemented by either controller.
2. Coordination between controllers was ineffective.

The investigation revealed that each controller had different expectations of the intentions of the other. The DN controller had expected the AN controller's Metro would continue on its current track, and that the two aircraft tracks would cross. Conversely, the AN controller expected to keep his aircraft inside the track of the departing B737. Neither the coordination nor communication between controllers was effective. The unexpected turn onto downwind by the Metro, towards the B737, reduced the distance available for the B737 to climb safely above the Metro. The DN controller attempted to stop the B737 at 6,000 ft, but that instruction, combined with the rate of climb of the aircraft, was unable to prevent a breakdown of the vertical separation standard.

The instructions passed to the pilot of the B747 may have been unnecessarily complex, given that the pilot was from a non-English speaking background. The controller's transmission was not as definitive as it could have been and included extraneous, non-standard phraseology.

The response from the crew may have indicated to the controller that his transmission was not understood, in that the word "into" indicated a possible turn to intercept the localiser. In addition, the controller did not query the unintelligible transmission.

Air Traffic Control services

Sector 3 was responsible for the provision of air traffic control in that part of the Bangkok FIR to the south of Bangkok, and for associated portions of the Phnom Penh and Ho Chi Minh FIR'S. The Sector 3 console had three positions: a radar control position with a radar display located on the left, a procedural control position in the centre, and a radar assistant position on the right. The radar controller was responsible for separating all aircraft in the sector. This included aircraft outside radar coverage. The Sector 3 procedural controller was responsible for issuing clearances using procedural control, and assisting the radar controller with flight progress strip (FPS) marking and coordination. The procedural controller was required to notify the radar controller of any changes that would affect procedural separation.

The radar controller was the only position with facilities to transmit and receive on the control frequency of 135.5 MHz. The procedural controller could monitor the frequency, but required the radar controller to transmit control instructions to aircraft operating under procedural control.

The console had been originally designed for operations utilising a flight data processor for aircraft flight information, without the need for flight progress strips. As a result, the radar operator and assistant radar positions were not fitted with flight progress strip bays. The flight data processor had subsequently proved to be less effective than planned and the sector had reverted to using flight progress strips. This required the radar and the radar assistant consoles to be fitted with temporary strip holders.

A high level of interaction and cooperation was required between the radar and procedural controllers to effectively manage the sector's airspace. The flight progress strips for each aircraft were required to be retained in the procedural display until the crew reported at the next position. This was to enable controllers to observe that an aircraft was in transit between the previous and next positions. However, due to limited space to display the strips, the Sector controllers had developed a habit of removing flight progress strips at the earliest opportunity to make space for new strips.

The strip for QFI6, annotated for the portion of the route from ALGOR to KABAS, did not include an estimate for KATKI. There were two strips for KAL362: one annotated for the portion of the route before KANTO, and one for KANTO to SINMA. The KANTO strip for KAL362 was located in the same bay as the KABAS strip for QF16. The radar controller removed the KAL362 KANTO strip from the bay after the crew reported at that position, prior to the SINMA position.

When the crew of KAL362 requested climb from FL270 to FL290, the radar controller scanned the flight progress strips at the procedural position. There was a SINMA strip for KAL362, but no other strip to indicate a possible conflict. SINMA was located east of the route of QF16. The procedural controller was carrying out coordination duties at the time, and did not hear the climb request. The radar controller then issued a clearance for the crew of KAL362 to climb to FL290, without consulting with the procedural controller.

Crew awareness

The crew of QFI6 were using the same control frequency as KAL362 when the crew of that aircraft reported at KANTO, and were subsequently approved to climb to FL290. There were reports of radio interference on that frequency, including reports of interference from aircraft operating at lower levels. The crew of QF16 did not recall hearing the crew of KAL362 request climb to FL290, nor the amended clearance and readback.

1. The design of the Sector 3 console did not allow for all relevant flight progress strips to be displayed.
2. The radar controller removed the KANTO flight progress strip after the KAL362 crew reported at that position.
3. The procedural controller did not hear the request for climb to FL290 by the crew of KAL362.
4. There was no requirement for the display of KATKI on flight progress strips for all aircraft using the intersecting routes.
5. The radar controller did not consult with the procedural controller prior to instructing the crew of KAL362 to climb to FL290.
6. The radar controller did not ensure that vertical separation was maintained between KAL362 and QF16 while the aircraft were in an area of conflict
7. The crew of QF16 did not hear the request and subsequent approval for KAL362 to climb to FL290.

The procedural controller was responsible for issuing clearances to aircraft under procedural control, as was the case in this event. The role of the radar controller was to pass on the clearance to the aircraft. By not consulting with the procedural controller, the radar controller bypassed the established system of control, leading to a breakdown in safety.

The configuration of the Sector 3 console provided insufficient space to adequately display all relevant flight progress strips. As a result, controllers had developed the habit of removing strips at the earliest opportunity, thereby creating the potential for vital information to be missed.

The KANTO flight progress strip for KAL362 should have been retained on the procedural board until the crew reported at SINMA, the next position. The removal of the KANTO strip by the radar controller removed the only reminder available to all controllers that the intended tracks of KAL362 and QFI6 would cross.

Inclusion of the KATKI position on all flight progress strips for aircraft using the intersecting routes would have enabled controllers to more readily assess separation requirements in the procedural airspace. If the strips had required the KATKI position it is probable that the details for QFI6 and KAL362 would have been displayed under the same designator on the board, allowing controllers to recognise the potential conflict.

The inability to monitor the control frequency while conducting coordination reduced the likelihood of the procedural controller maintaining a complete appreciation of the disposition of traffic.

The reason why the crew of QFI6 did not hear the transmissions regarding KAL362 climbing to the same level, while operating on the same frequency within direct line of sight, could not be determined.

QFI6, a Boeing 747, had departed Bangkok for Melbourne and was tracking southbound on airway G463 at flight level (FL) 290. The aircraft was in contact with Bangkok Area Control Centre (BKK ACC) Sector 3 on 135.5 MHz. Sector 3 was a combined radar and procedural control sector. At 0212:54 QF16 reported passing ALGOR at FL290, estimating KABAS, the flight information region (FIR) boundary, at 0221. Just prior to reaching KABAS, the aircraft would pass the intersection of G463 and B219 at KATKI. These positions were all located beyond radar coverage, over international waters, within the procedural control portion of BKK ACC Sector 3 airspace.

A Korean registered Boeing 747, KAL362, had departed Kuala Lumpur for Seoul, tracking via B219 at FL270. Approaching KANTO, located to the west of KATKI, the aircraft was transferred to the BKK ACC. The crew of KAL362 contacted Bangkok Sector 3 on 135.5 MHz and reported passing KANTO at FL270, estimating KATKI at 0219, and requesting climb to FL290. The next reporting position was SINMA, to the east of KATKI. At 0217:20 Bangkok Sector 3 cleared KAL362 to climb to FL290. KAL362 reported leaving FL270 for FL290. At 0220:21 the pilot in command of QF16 advised the Sector 3 controller of having received a traffic alert and collision avoidance system (TCAS) traffic advisory (TA), and that the aircraft had been climbed to FL300 to avoid a collision with KAL362, but was now descending to FL290.

The crew of QF16 had received a TCAS TA, followed by a resolution advisory (RA) commanding a climb to avoid climbing traffic some 800 ft below. Each crew sighted the other aircraft. The KAL362 crew also received a TCAS TA, followed by a TCAS RA commanding a descent. The crew of KAL362 did not report a traffic confliction.

An investigation carried out by Aeronautical Radio of Thailand Ltd, the Thai air traffic control organisation, indicated that KAL362 was incorrectly given a clearance to climb to FL290 by the Bangkok Sector 3 controller, and that the crews of both QF16 and KAL362 were acting in accordance with the clearances issued to them. The minimum required distance between the aircraft was 1,000 ft vertical separation, or a lateral separation of not less than 15 minutes between their estimated times of arrival at KATKI, the intersection of their intended flight routes.

In accordance with ICAO Aircraft Accident and Incident Investigation Annex 13, paragraph 5.3, the circumstances of this occurrence provide for the State of Registry to institute and conduct any necessary investigation. After consultation with the Korean authorities it was agreed that BASI would take responsibility for the ongoing investigation.

Radar

The Adelaide radar did not provide reliable coverage on air route T134. It normally gave coverage for aircraft over Portland and for a few miles east of SUBUM, but only provided intermittent coverage for the remainder of the route segment.

Radio

As air route T134 was predominantly outside VHF coverage, the route was designated for HF operation. The air traffic service unit responsible for HF communication was Perth International Flight Service. This limitation resulted in a delay in passing information between the controller and the crew of the B737 because the flight service officer was the intermediary for all radio transmissions.

Flight planning

The company flight plan for the A320 included a manoeuvring time of 10 minutes at the departure aerodrome. This time was estimated by the flight planner, using a computerised flight planning system, as that required for manoeuvring prior to setting course after the aircraft had become airborne. However, the flight plan indicated the time as an elapsed time from airborne to abeam/overhead Melbourne airport. The air traffic control strip printing system did not provide for a specific manoeuvring segment. Consequently, it added the 10-minute manoeuvring time to the 12-minute flight-planned time to the first enroute navigation aid.

Having added this 10-minute interval to the departure time, all the flight progress strips for the A320 therefore indicated position estimates which were approximately 10 minutes later than the corresponding flight-planned estimates.

The manoeuvring time was introduced by the company to allow for the time between becoming airborne and setting course, which varied depending on considerations such as runway direction, standard departure instructions and wind velocity. The flight crew had the same initial flight-plan information as air traffic control. However, the crew updated their plan to reflect the actual time at which the aircraft set course.

The B737 was operated by a different company and the flight plan did not include provision for a manoeuvring time. The flight progress strip estimates were therefore within the normal tolerance of plus or minus 2 minutes.

Pilot reporting

While under radar observation, pilots were not required to report their position as the controller could see that the aircraft was at the reporting point. If there was a difference between the estimated and actual times of arrival, then it was noticed by both parties and independently corrected. Under these conditions separation standards relied on radar.

When under procedural control, separation standards were based on estimated times of arrival at the reporting points and pilots were required to advise air traffic control of any variation of more than 2 minutes. Separation standards were devised to allow for these variations. Controllers crosschecked known times, as reported by pilots, with the flight plan time intervals to provide a check on the estimated time of arrival for the next position. If this crosscheck was within 2 minutes of the pilots estimate, no further action was required.

1. The flight plan for the A320 contained a manoeuvring time for the aircraft prior to setting course.
2. The air traffic control strip printing system was unable to allow for a discrete manoeuvring time in the strip preparation.
3. The Melbourne Sector 4 controller did not conduct a crosscheck calculation on the flight progress strip notation for the A320's estimated time of arrival at SUBUM.
4. The Adelaide Sector 4 and Melbourne Sector 1 controllers did not initiate any check action for the observed significant difference in the time interval for the A320 between Portland and SUBUM.
5. Air traffic control procedures were such that there was no assurrance that the flight crew's estimated times were the same as those being used by ATC to provide procedural separation.

Flight planning

The air traffic control strip printing system's interpretations of the A320's flight plan led to a latent error in the flight progress strips for the A320 that was not present in the B737 strips. The system defence to negate this error was removed when the Melbourne Sector 4 controller did not update the flight progress strip estimated time for the SUBUM position.

Air traffic control procedures

Once the Melbourne Sector 4 controller had read the flight plan estimated time for the A320 at SUBUM, the coordination procedures were such that this incorrect estimate was passed to Adelaide Sector 4 and then from Adelaide Sector 4 to Melbourne Sector 1 without further check. Consequently, when coordination was required to allow the climb of the B737, the two controllers concerned had incorrect information. They did not question the information because it had been based on a radar observation.

Air traffic controllers

Although the flight progress strips showed that a longitudinal separation standard existed, the Melbourne Sector 4 controller did not review the situation before transferring the aircraft to Perth International HF. However, a scan of the strips should have revealed the error because the flight-planned time for the route segment was 45 minutes which, when added to the known time over Portland, would have given an estimate for SUBUM of 1447 rather than 1500.

The decision by the oncoming Adelaide Sector 4 controller to check his longer-range radar display, detected the actual position of the A320 on air route T134 and enabled him to implement remedial action.

Pilot reporting

The aircraft passed over the last radar-observed position and the crews would have made estimates for SUBUM, but were not required to report those estimates to air traffic control. The controller also made estimates for SUBUM and based a procedural separation standard on those estimates. He had no need to check those estimates with the pilots or any other controller. Consequently, when the error was made, there was no crosscheck with which to provide a safety net.

Both flight crews were operating within 2 minutes of their corrected estimates, based on their actual times at Portland, and therefore were not required to report any minor changes.

Consequently, the crews and the controllers were working a procedural standard from two different time bases, neither of which had been crosschecked with the other. In a procedural environment, pilots and controllers must have a single datum on which to base their reporting and separation.

The Boeing 737 (B737) had departed Sydney for Perth and the crew was maintaining the aircraft at flight level (FL) 280. The planned route was to track overhead Portland, Vic., then via air route T134 across the Great Australian Bight. The reporting point SUBUM was located on air route T134, approximately 220 NM south-south-west of Adelaide.

As the aircraft proceeded towards Portland, it was being radar monitored by the Melbourne Sector 4 air traffic controller. Flight crews were not required to report their positions while under radar observation. Accordingly, the time at which the aircraft was overhead Portland was recorded on the air traffic control flight progress strip by the sector controller, who then calculated an estimated time of passing SUBUM. This estimate was based on the flight-planned time interval from Portland to SUBUM and the actual time at which the controller saw the aircraft pass over Portland. The report was then coordinated to Adelaide Sector 4, which had jurisdiction for the route segment to SUBUM.

The Airbus A320 (A320) departed Melbourne for Perth and was tracking to intercept air route T134 via Portland. The crew was maintaining the aircraft at FL310.

The flight progress strips displayed information obtained from the respective company flight plans and showed that the B737 was estimating Portland at 1355 EST and SUBUM at 1444. They also showed that the A320 was estimating Portland at 1415 and SUBUM at 1500.

The Melbourne Sector 4 controller observed the B737 pass Portland at 1357 and, based on that observation, estimated that the aircraft would be approximately on time at SUBUM and elected not to change the estimated time of 1444. The position report was coordinated with Adelaide Sector 4. Air traffic control procedures allowed for a difference of up to 2 minutes between pilot and controller estimates without requiring a cross-check.

A short time later, the Melbourne Sector 4 controller assessed that the A320 passed over Portland at 1402 (13 minutes ahead of the estimate) but due to other duties, did not immediately notate the flight progress strip or coordinate this position with Adelaide Control.

At 1404, the Melbourne controller realised that he had not informed the Adelaide controller of the A320's Portland position report and commenced the coordination process. He reported the time at Portland as 1402 and the level as FL310. At this moment he realised that he had not made a calculation for the SUBUM estimate and used the estimated time of arrival as written on the flight progress strip as his revised estimate. This action resulted in his flight progress strip indicating that the A320 was going to be "on time" at SUBUM despite being 13 minutes early at Portland.

Communications for both aircraft crews were then transferred to Perth Flight Service on high frequency (HF) radio.

The Adelaide Sector 4 controller accepted the coordination from Melbourne Sector 4 on face value because the Melbourne controller was required to check the accuracy of data he was coordinating. The Adelaide Sector 4 controller checked his flight progress strips and noticed that the A320 was early at Portland but estimated to be "on time" at SUBUM. He considered that this discrepancy was probably due to a flight planning error that had been corrected by the Melbourne controller. His decision was influenced by the fact that both aircraft were estimated to be "on time" at SUBUM. He also considered that as they were vertically separated any error in the estimated times would not be significant, and chose not to pursue the matter any further.

The Adelaide Sector 4 controller then coordinated the Portland position details, including the estimated times of arrival at SUBUM, with Melbourne Sector 1, the control position for air route T134 from SUBUM. As a consequence, Melbourne Sector 1 had flight progress strips that indicated both aircraft being "on time" at SUBUM.

At 1444, the Perth Flight Service officer contacted Melbourne Sector 1 with the position report at SUBUM from the crew of the B737. This report included a request for a climb to FL310. As such a climb would negate vertical separation, the controller was required to establish a 10-minute longitudinal separation standard in order to approve the request. As the flight progress strips indicated estimates for SUBUM at 1444 and 1500, this standard appeared to have been achieved. However, because the B737 had only just entered his area of responsibility, he was required to check with the previous sector (Adelaide Sector 4) before authorising such a change. There had been a change of personnel at Adelaide Sector 4 and, as the oncoming controller also had the same time indications as the Melbourne controller, he agreed to the change and the crew of the B737 was instructed to climb to FL310.

After approving the climb, the Adelaide controller decided to check his radar display on the maximum range and saw that the A320 was only 30 seconds east of SUBUM. He immediately contacted the Melbourne Sector 1 controller to inform him of the confliction.

The Melbourne Sector 1 controller contacted Perth Flight Service and issued an instruction for the crew of the B737 to descend to FL290. Because of the amount of coordination required, it took almost 3 minutes to translate the Adelaide controller's observation into an acknowledged instruction for the B737 to descend. As the B737 had reached FL300 before the crew received the instruction to descend, and as the vertical separation standard was 2,000 ft, an infringement of the separation standards had occurred.