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The Australian Transport Safety Bureau did not conduct an on scene investigation of this occurrence. The information presented below was obtained from information supplied to the Bureau.

On 6 October 2004, at 1301 central standard time, a Lockheed Georgia Company C-130H (C130) operated by the Royal Australian Air Force (RAAF) departed Darwin Airport for Edinburgh, tracking via air route A461. The pilot of the C130 was cleared to climb to flight level (FL) 250. Eleven minutes after the C130 departed, a Boeing Company 737-838 (737), registered VH-VXM, departed Darwin Airport for Adelaide, also tracking via A461.

The sector controller located in the Brisbane Centre recognised that the faster following 737 could potentially conflict with the C130 during its climb and contacted RAAF Darwin Approach. The controllers agreed that the Darwin approach controller would establish a method to resolve the conflict and accept responsibility for separation. The Darwin controller issued a requirement to the crew of the 737 to reach FL260 by 90 DME (a measure in nautical miles after application of navigation aid and other tolerances using Distance Measuring Equipment) from Darwin. This requirement did not provide separation assurance with the C130. This error was not detected by either controller.

At 1319, a radar handoff of the 737 was completed between the two controllers and the climb requirement was reiterated to the crew of the 737 by the Darwin approach controller. At 1321, when the crew of the 737 made their initial call on the sector controller's frequency, that controller realised that there was a problem with the separation method being applied. At that time, the 737 was passing FL212 and the C130 was passing FL220, and the distance between the two aircraft was reducing. The controller immediately instructed the 737 crew to climb to FL370 and to expedite their climb through FL230. At 1322, the radar system's short term conflict alert activated. The C130 crew was instructed to descend their aircraft to FL220. The distance between the aircraft reduced to 3.9 NM, which was less than the required 5 NM radar separation standard, before the 1,000 ft vertical separation standard was re-established. There was an infringement of separation standards.

The RAAF and Airservices Australia investigated the occurrence. Those investigations found that:

  • the Darwin approach controller did not apply an appropriate requirement to the crew of the 737 to ensure separation was maintained
  • the sector controller's monitoring of the situation was inadequate.
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