The Brisbane Ocean sector controller saw on radar an unidentified aircraft climbing through flight level (FL)180. The controller issued traffic information to the crew of a Dash 8 operating an instrument flight rules (IFR) flight from Lord Howe Island to Sydney at FL200. The crew of the Dash 8 sighted the unidentified aircraft at an approximate distance of 5 NM and 1,500 ft below them. The two aircraft passed with 3 NM lateral separation at the same level. The unidentified aircraft was subsequently identified as an Astra conducting an IFR calibration flight. It appeared that the crew of the Astra had not complied with Aeronautical Information Publication (AIP) procedures for changing levels in non-controlled airspace. These procedures require pilots of IFR category aircraft operating in non-controlled airspace to notify the relevant air traffic agencies of any changes in altitude/level. Investigation of the occurrence revealed that the Astra crew were not notified of a change in airspace management for their area of operations.
The Astra crew was conducting a calibration of a new radar that had been installed at Williamtown aerodrome. This required the aircraft to track outbound from Williamtown at 1,500 ft, in a direction clear of local operating areas and air routes, until radar coverage was lost and then return on the reciprocal track while climbing. Once the next altitude or level was reached the crew would immediately turn the aircraft to track outbound again. The manoeuvre was to be repeated at 10,000 ft, FL200, FL300 and FL400 and would conclude with the aircraft completing the task at approximately 220 NM from Williamtown.
The Astra crew had prepared and dispatched written briefs on the task to Williamtown and Brisbane Air Traffic Control (ATC) agencies. However, the calibration task schedule was amended and subsequently conducted 24 hours earlier than originally notified. The brief depicted the calibration flight as being a series of steps with an increase in altitude/level as the distance from Williamtown increased but did not depict that the aircraft would fly the reciprocal track at any stage. After the Astra had departed Williamtown to commence the calibration, the Williamtown approach coordinator briefed the Brisbane Flight Service International officer on the task, based on the briefing and other details as subsequently advised by the crew.
The general practice of the Astra crew was to conduct personal briefings with the responsible air traffic control staff on the day of a calibration task and this was their intention on the day of the occurrence. However, when the Astra arrived at Williamtown, the senior air traffic control officer who had planned to attend the briefing was not available. Consequently, the crew only briefed a technical ground party.
The Astra crew was issued a clearance by Williamtown Air Traffic Control to track via the 100 tactical air navigation aid radial on climb to FL210. On this track the Astra would transit Williamtown restricted area R577 which was promulgated as continuously active, 24 hours a day. The intended track of the Astra entered and exited R577 respectively at 25 NM and 130 NM east of Williamtown. The vertical limits for the area are from sea level to FL600. When not required for military operations a notice to airman (NOTAM) deactivating R577 for specific periods was normally issued by Williamtown Air Traffic Control. A deactivation NOTAM was not issued for the period of the calibration flight.
As an aid to airspace management, Brisbane and Williamtown Air Traffic Control agencies had agreed to automatically release portions of R577 and other restricted areas to Brisbane when the restricted areas were active. This agreement was published in the Northern New South Wales Manual of Air Traffic Services Supplement (MATS SUPP) which in turn was part of both Williamtown and Brisbane operating procedures. The agreement effectively transferred airspace management responsibility for the south-east portion of R577, known as the Jordy Release, from Williamtown Air Traffic Control to Brisbane Centre. The planned track of the Dash 8 passed through the Jordy Release.
The lateral and vertical limits for Australian airspace were published in the Airservices Australia Designated Airspace Handbook (DAH) and depicted on AIP charts. The DAH, charts or a NOTAM can be used for flight crew pre-flight briefing. None of the documents included the MATS SUPP provisions.
A letter of agreement between Brisbane Ocean sector, Brisbane Flight Service International and Sydney Flight Service 4 detailed the airspace management responsibilities for the Jordy Release when transferred to Brisbane Centre. The division of responsibilities was:
- Ocean sector
That portion of the release above FL200 between 90 NM and 150 NM from Sydney and above FL245 outside of 150 NM Sydney, - Flight Service International
That portion of the release at FL200 and below that level outside of 90 NM from Sydney, and - Sydney Flight Service 4
That portion of the release below the control area steps inside 90 NM from Sydney.
The Ocean sector controller was required to separate IFR aircraft as if they were in controlled airspace. The officers of both flight service units were required to issue traffic information to pilots of IFR category flights, just as they would have for pilots of IFR flights in non-controlled airspace, in accordance with the Manual of Air Traffic Services (MATS) criteria. Part of the MATS criteria required traffic information to be issued when aircraft were climbing or descending through the level of another aircraft when these aircraft were within 15 NM or 10 minutes longitudinally or laterally. Ocean sector uses radar and procedural control methods to separate aircraft. Radar coverage extends to beyond the eastern limit of R577. Neither of the flight service units had access to radar services.
Because of the flexible airspace management arrangements for the Jordy Release, flight service international officers usually pre-empted requests for confirmation of the availability of planned routes for aircraft inbound to Sydney. Normal practice was to advise crews as early as possible when the area was active with military operations to enable them to commence tracking via alternative routes. The crew of the Dash 8 was not advised that their planned route was unavailable. The crew was subsequently advised to contact the Ocean controller at 140 NM from Sydney for a clearance.
The Astra crew reported that due to R577 being active, they believed that, their flight would be managed by Williamtown air traffic control. The Williamtown coordinator advised flight service international that the crew had been cleared to FL210 but that initially they would maintain 1,500 ft. The coordinator subsequently advised flight service international that the Astra had climbed to 10,000 ft. The Astra crew was instructed that they were leaving the Williamtown restricted area and to transfer to flight service international on high frequency (HF) radio. This was required as they were operating in that portion of R577 being managed by flight service international.
After several attempts, the Astra crew contacted flight service international on HF radio and was advised of another HF frequency to use if they were having communication difficulties. There was no further contact with the crew on HF radio. The flight service international officer attempted unsuccessfully to contact the crew. The problems with the HF radio communication were believed to be the result of propagation difficulties. Once it was apparent to the crew that HF communication was not viable they tried to establish communications with Brisbane Centre via VHF. The crew reported after the occurrence that because they were unable to advise any air traffic service agency of the next climb, from 10,000 ft to FL200, they broadcasted their intention on the VHF emergency frequency, 121.5 MHz. The investigation could not establish whether other crews heard the transmission.
The crew contacted the Nambucca Sector Controller and reported that their position was 120 NM east of Williamtown on the 100 radial and that the aircraft had left 10,000 ft on climb to FL200. The Nambucca controller confirmed that the Astra was tracking west and that at 110 NM from Williamtown the crew would commence a turn to track outbound. The Nambucca controller contacted the Ocean controller to report the Astra's position. At approximately the same time the Ocean controller was issuing a clearance to the crew of EA261 and shortly after noticed an unidentified aircraft approaching the Dash 8. The Nambucca controller issued traffic information to the crew of the Astra, who arrested the climb of their aircraft and then descended to FL185.
The Astra crew did not select the radio failure code of the aircraft's secondary surveillance radar transponder. The investigation did not establish why the crew did not change the transponder code.