The Australian Transport Safety Bureau did not conduct an investigation into this occurrence. The report produced below is derived from an investigation report produced by the Department of Defence-Royal Australian Air Force (RAAF)1 which was the administering authority for the Darwin Control Zone.
Reported information
On 21 July 2004, at 0955 central standard time, a Cessna Aircraft Company 206 (C206) departed Darwin for Croker Island, NT. The aircraft was being operated under the visual flight rules (VFR). Another aircraft, a Cessna Aircraft Company 210 (C210) departed Darwin at 0956 for Snake Bay, NT, and was also being operated under the VFR. A third aircraft, a Cessna Aircraft Company 404 (C404) departed Darwin at 0958 for Croker Island. That aircraft was being operated under the instrument flight rules (IFR). All three aircraft were instructed by the aerodrome controller (ADC) to fly a heading of 060 degrees after take off.
The RAAF investigation report found that the pilot of the C404 had been instructed to sight and maintain visual separation with the C210. However, the C404 also caught up with and eventually overtook, the C206. Neither the pilot of the C206 nor the pilot of the C404 received traffic information on the other aircraft, and neither pilot was assigned the responsibility for separation with the other aircraft. According to the RAAF investigation report, the C404 passed within 0.2 NM of the C206 while both aircraft were at the same altitude. There was an infringement of separation standards.
The Manual of Air Traffic Services (MATS) section 4.5.1.4 authorised the assignment of responsibility for separation to the pilot of one aircraft if that pilot reported 'sighting the other aircraft and is instructed to maintain visual separation with, or to follow that aircraft'. The MATS Section 4.5.1.2 also stated that, when applying visual separation, 'controllers shall consider aircraft performance characteristics, particularly in relation to faster following aircraft'.
Darwin was operating on auto-release procedures at the time of the occurrence. The MATS Part 10, section 1 defined auto release as a procedure whereby the ADC must ensure that the spacing between successive departing aircraft is sufficient to enable the Departures controller to establish and maintain the required separation minima. In this occurrence, the responsibility for establishing and maintaining the required separation minima between the C210 and the C404 had been assigned to the pilot of the C404. The ADC did not ensure that the departures controller could establish and maintain separation between the C206 and the C404, and the responsibility for establishing and maintaining separation had not been assigned to either pilot.
1 For further information on the RAAF report contact The Directorate of Flying Safety - Australian Defence Force (FS5), Campbell Park Offices, Canberra ACT 2600.