At 0627 EST, a Boeing 737 (B737) departed Melbourne for Perth. Melbourne Sector Inner West advised Melbourne centre of the departure. An airways data systems operator (ADSO) received this information and notified Adelaide centre of the departure by intercom. He then activated the flight strips for Melbourne Sector 1 and delivered these strips to this sector. A hard copy departure message should also have been sent via the Aeronautical Fixed Telecommunications Network (AFTN) to all units affected by the flight, but this task was not completed. As a result, Perth Air Traffic Control did not receive any notification that the aircraft had departed.
For much of its flight to Perth, the B737 was on route L513 and was under the control of Melbourne Sector 1, a procedural control sector. This sector was combined with Sector 5 until approximately 0850 when it was decided to split the two sectors. The departing controller proceeded to hand over control of Sector 1 to the oncoming controller, but kept control of Sector 5.
At 0853 EST, during the Sector 1 handover/takeover, the crew of the B737 reported having passed TAPAX (a position reporting point 523 NM east of Perth) at 0852. They also reported that they were maintaining FL350, and estimating TAMOD (a position reporting point 153 NM east of Perth) at 0951. The departing controller took the position report and appropriately marked the flight strips. The report was required to be passed to the Perth Outer controller, as the sector boundary was 10 NM east of TAMOD. This coordination task was not done.
The departing Sector 1 controller later reported that he did not perform the coordination task as he assumed that the oncoming controller would do it. He also reported that he did not specifically point out the need for the oncoming controller to perform this task, but assumed that she had heard the position report and understood that it needed to be done. The oncoming controller later reported that she could not remember hearing the position report. Neither controller could recall whether the relevant flight strip had been cocked on the flight progress board to indicate that there was an outstanding task to be performed.
The oncoming controller took control of Sector 1 at 0856. Soon after taking over, Perth control contacted her to advise that an eastbound Airbus 320 (A320), VH-HYJ, was about to transfer to her frequency and that the crew would soon contact her. This crew contacted her at 0857. At 0858, immediately after taking this crew's report, the controller contacted the westbound B737's crew and advised them to contact Perth at TAMOD. This frequency-transfer task was normally performed when the aircraft was 5 minutes from TAMOD, or 0946 in this case. Shortly after performing this task, the controller removed the B737's flight strips from the flight progress board. This action was normal practice for filing the flight strips after an aircraft had left the Sector 1 area of responsibility.
At 0929 EST, another eastbound A320, VH-HYR, departed from Perth for Melbourne. The aircraft was planned on route L513 until TAMOD, before turning onto the one-way route Y53. The estimate for TAMOD was 0953. The Perth controller informed Sector 1 of the departure. He advised that the aircraft had planned FL370 but that he recommended restricting the aircraft to non-standard FL350 due to a westbound A320, VH-HYA, at non-standard FL370 and estimating TAMOD at 1006. The Sector 1 controller agreed with this restriction.
Although having the air traffic under his jurisdiction procedurally separated, the Perth Outer controller checked the radar at 0941 and observed a return approximately 220 NM east of Perth (67 NM east of TAMOD). As the displayed information was based on extreme range returns, it was considered unreliable. However, it indicated a westbound jet aircraft at FL350. The controller checked his coordinated and pending traffic, but was unable to identify the aircraft.
At 0943, Perth Outer contacted Melbourne Sector 1 to report the return and ask whether she knew its identity. The Sector 1 controller was not aware of any aircraft in that area other than HYA, the westbound A320 that was 15 minutes behind the position of the unknown aircraft. Perth suggested restricting HYR to FL330 until the problem could be rectified. Another Perth controller advised HYR's crew of the problem. At 0946, Perth Outer directed the crew to divert to the left of track, as the observed radar return's altitude was still unverified.
With the assistance of other controllers, the Sector 1 controller retrieved the used flight strips and identified the return as the B737. The relevant information was reported to Perth Outer at 0947. The aircraft was then transferred to the Perth controller.
As the A320 had been restricted to FL330 and diverted left of track, there was no breakdown in separation. The two aircraft passed each other at 0950:01. HYR passed TAMOD at 0949, and the B737 reached TAMOD at 0951. Analysis of the radar tape indicated that HYR would have reached FL350 between 0949:20 and 0950:20. The B737 was fitted with a Traffic Alert and Collision Avoidance System.
Departure Message Processing
After receiving the B737's departure notification from Melbourne Sector Inner West, the ADSO annotated the callsign, departure point, destination and departure time on an aircraft movement advice form before advising Adelaide of the departure. However, this information was not entered in the appropriate boxes on the form and the SSR code was not entered. In addition, various unnecessary items were written on the form, including the numbers of four AFTN messages that had been sent around the time that the B737's departure was being processed.
The ADSO who took the departure notification was a trainee. He was required to be directly supervised during his task performance, but this supervision was not present at the time the departure was being processed. It was later reported that workload was high at the time of the departure, and that the trainee and the supervising ADSO were both performing departure processing tasks.
Prior to the incident, the tasks required to process a departure were specified in written procedures, but they were not all specified in the same procedural documentation. The order in which the tasks should be performed was not specified in any procedural documentation.
Sector 1 Handover/Takeover
Sector 5 was in the process of being transferred from the Bight Group, which also had Sectors 1 and 4, to the Desert Group. A console for Sector 5 had been set up in the Desert Group's area, and the controllers in that group were currently being trained in Sector 5 operations. Until the transfer was completed, Sector 5 could also be operated from Sector 1's console.
Immediately after the oncoming controller took over Sector 1, the departing controller took the flight strips for Sector 5 and arranged them on the relevant flight progress board in the Desert Group. He then proceeded to conduct a training session on Sector 5 for another controller.
It is desirable for a controller to perform all outstanding tasks prior to handing over to another controller, but this is not always practical. In this case, several tasks had to be conducted during the handover/takeover and the workload level was significant. Both the departing and the oncoming controller reported that the handover of Sector 1 appeared to be well conducted. Prior to the incident, there was no written procedure that detailed all of the required tasks to be performed during a handover/takeover.
Sector Boundary
The boundary between Melbourne Sector 1 and Perth Outer was approximately 10 NM east of the reporting point TAMOD (163 NM east of Perth). The range of the relevant radar was typically 220 NM to the east of Perth between FL330 and FL370. The Perth controller was therefore able to see to approximately 50 or 60 NM east of TAMOD at high flight levels. The air route structure had been redesigned with the intention of the Perth radar being used to its full potential, but the sector boundary had not been changed.
Personnel Information
The oncoming Sector 1 controller commenced duty at 0700 on the morning of the incident. She finished duty on her previous shift at 2030 the previous night. As she lived 90 minutes from her place of work, she had only slept 5 hours during the night before the incident. Due to other factors, she had slept even less during the previous night.
In addition to not passing coordination on the B737, the oncoming controller made three minor errors during the period after she took over Sector 1 until the Perth Outer controller detected the incident. These errors were an attempt to call HYA on the wrong frequency, and two occasions of contacting the wrong Adelaide controller (as she forgot that the relevant Adelaide sectors were combined). There were no other problems noted with any aspect of her performance or behaviour during this period.
Neither of the Sector 1 controllers had received any training in the use of teamwork or team resource management skills.