A Cessna 340 (C340) was maintaining 8,000 ft while tracking direct to Williamtown from a position bearing 020 degrees at 25 NM. A Royal Australian Air Force Macchi was conducting a Tacan approach and intended to perform a missed approach procedure before climbing to 10,000 ft to continue the training sortie. The sector controller had issued the approach controller with a restriction for the Macchi to maintain 7,000 ft on departure to ensure separation with the C340. The approach controller was a trainee being supervised by a rated officer.
While the Macchi was on final approach to runway 30, a further restriction of 2,000 ft was placed on the departure due to other conflicting aircraft. The crew of the Macchi contacted the approach controller on departure and advised that they were maintaining 2,000 ft. The controller took appropriate action to resolve the confliction and then cleared the crew of the Macchi to climb to their planned level of 10,000 ft. The controller had omitted to issue the 7,000 ft restriction even though it was still a requirement to ensure separation with inbound aircraft.
As the Macchi climbed through 8,000 ft, while approximately 6 NM south of Williamtown, it passed within 1 NM of the C340. There was an infringement of separation standards.
The investigation by the Directorate of Flying Safety - Australian Defence Force revealed that the Australian Defence Air Traffic System (ADATS) was being trialled at the time but that the older surveillance radar (SURAD) equipment was actually in use by the approach controller. The SURAD did not have identification labels or height information (facilities that were available on more modern equipment) and that limitation increased the workload on the controller. Additionally, the SURAD was unreliable in its ability to provide constant, accurate position information within 10 NM of Williamtown. The controllers were aware of those restrictions as they were documented in aeronautical publications.
The military sector controller was using the Interim Radar Display System (IRDS). Although that system had labels and a Mode "C" height reading capability, the Macchi was not equipped with a Mode "C" capability. Consequently, the sector controller did not have a radar indication of the height of the Macchi.
The airspace was divided vertically between approach/departures and sector control with ground level to 5,000ft being owned by approach/departures, and sector control the airspace above. The coordination had been adequate but flight progress strip management made the task of remembering an additional restriction more complicated. Consequently, the trainee approach controller forgot to issue the 7,000ft requirement to the crew of the Macchi. The rated officer did not pick up the error until the Macchi was actually passing the level of the C340. The training officer said that he looked at the radar and the strips but was feeling tired and may have missed the information.
The management of the flight progress strip, which was very crowded and difficult to read, was different from that used in other Australian locations. Local procedures were being taught where level restrictions were placed in box 11, whereas in all other air traffic control units the box for such notation was box 4, as specified in the Manual of Air Traffic Services (MATS). That local procedure had been in use at Williamtown for some time, but the investigation was unable to find any documentation specifying such action. In addition, the strip had been divided into four quarters to cater for four separate approaches that the crew of the Macchi had intended to carry out. That action made the writing very small and difficult to read. The alternate method was to use separate flight progress strips for each approach, resulting in more writing space being available for instructions and, therefore, allowing for larger print.
Local safety action
As a result of the investigation the RAAF have made the following changes:
- Local Instructions have been amended to introduce a "cap" system of hand-off between approach and sector control. Approach maintains 5,000ft and sector assign descent to 6,000ft, therefore providing separation assurance between the airspace volumes.
- The procedure for notating flight strips has been amended to be in accordance with Manual of Air Traffic Services.
- The practice of using a single flight progress strip for multiple approaches was ceased.
In addition the following points are noted:
- The ADATS has been commissioned at Williamtown.
- The possible affect of fatigue on controllers has been referred for further investigation.
|Date:||29 June 2000||Investigation status:||Completed|
|Time:||0940 hours EST|
|Location:||9 km S Williamtown, Aero.|
|State:||New South Wales||Occurrence type:||Loss of separation|
|Release date:||14 December 2001||Occurrence class:||Airspace|
|Report status:||Final||Occurrence category:||Incident|
|Highest injury level:||None|
Aircraft 1 details
|Aircraft manufacturer||Cessna Aircraft Company|
|Type of operation||Flying Training|
|Damage to aircraft||Nil|
|Departure point||Bankstown, NSW|
Aircraft 2 details
|Aircraft manufacturer||Aeronautica Macchi S.p.A|
|Damage to aircraft||Nil|
|Departure point||Williamtown, NSW|