Aviation safety investigations & reports

de Havilland Canada DHC-8-201 , VH-TQG, 185 km E Williamtown, (NDB) NSW, 15 November 1999

Investigation number:
Status: Completed
Investigation completed


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 the 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.


The briefing planned between the Astra crew and Williamtown Air Traffic Control staff did not occur and as a result, the air traffic control staff were not fully conversant with the Astra crew's intentions. Also, the Astra crew were unaware of the unique delineation in airspace management responsibilities for the area where they intended to operate. These aspects made it difficult for the crew to adequately prepare for contingencies and for air traffic controllers to understand the complex nature of the calibration task.

The Astra crew complied with the clearance issued by Williamtown Air Traffic Control. However, the clearance was issued without air traffic control being fully conversant with the flight profile. The misunderstanding was compounded by the Astra crew believing that their flight would be managed by Williamtown Air Traffic Control. If the crew had been aware of the ramifications of the Jordy Release, it was likely that they would have appreciated that the initial stages of the flight would pass back and forth between R577 and non-controlled airspace. Had they been aware of this fact and that consequently, they were responsible for their own traffic avoidance, the Astra crew may have ensured that air traffic services were advised of the intention to change level well in advance of commencing the climb to FL200. If the crew had been able notify flight service international of their intention to climb from 10,000 ft to FL200 it was probable that they would have been issued with traffic information on the Dash 8 and the conflict may not have occurred.

The operation of the Astra's transponder on the assigned code assisted in the resolution of the situation. An alternative for the crew was to select the transponder to the radio failure code of 7600, which was part of the aviation safety net. Given the complex nature of the task and the communication difficulties being experienced by them at the time, this action may have provided a more timely alert to air traffic agencies. Had air traffic agencies been alerted by the change in code to 7600, it is likely that air traffic control or flight service international officers would have either provided traffic information or initiated action to separate other aircraft in the vicinity of the Astra.

Significant Factors

  1. The flight crew and air traffic control staff did not brief effectively before the calibration flight.
  2. The Astra crew was unaware that Brisbane Centre was responsible for management of a portion of R577.
  3. The Astra crew was unable to maintain continuous two-way communications with flight service international.
  4. The provision of radar coverage and use of secondary surveillance radar transponders in oceanic airspace assisted in the resolution of the conflict.

Safety Action

Local safety action

The operator of the Astra has confirmed that flight crew/air traffic control briefings will be conducted before all future calibration flights.

Australian Transport Safety Bureau safety action

As a result of the investigation the Australian Transport Safety Bureau issued the following recommendation:

The Australian Transport Safety Bureau recommends that the Australian Defence Force review airspace activation and clearance issue procedures to ensure that flight crews understand and/or are notified of any changes in prohibited/restricted/danger airspace management responsibility.

General details
Date: 15 November 1999   Investigation status: Completed  
Time: 0410 hours UTC    
Location   (show map): 185 km E Williamtown, (NDB)    
State: New South Wales   Occurrence type: Separation issue  
Release date: 11 August 2000   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft 1 details

Aircraft 1 details
Aircraft manufacturer de Havilland Canada  
Aircraft model DHC-8  
Aircraft registration VH-TQG  
Serial number 430  
Type of operation Air Transport Low Capacity  
Damage to aircraft Nil  
Departure point Lord Howe Island  
Destination Sydney, NSW  

Aircraft 2 details

Aircraft 2 details
Aircraft manufacturer Israel Aircraft Industries Ltd  
Aircraft model 1125  
Aircraft registration VH-FIS  
Serial number 045  
Type of operation Aerial Work  
Damage to aircraft Nil  
Departure point Williamtown, NSW  
Departure time 1130 hours UTC  
Destination Williamtown, NSW  
Last update 13 May 2014