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On 2 June 2014, at about 1200 Central Standard Time (CST), the approach controller at Darwin Airport, Northern Territory was processing the arrival of a Qantas Boeing 737 aircraft, registered VH-XZA (XZA), and an Airnorth Fairchild SA227, registered VH-ANW (ANW). When about 34 NM south-east of Darwin on a standard arrival route, XZA was cleared by the approach controller to descend to 3,000 ft for an approach to runway 11.

About 3 minutes later, when about 34 NM SE of Darwin, ANW was cleared by the approach controller to descend to 3,000 ft. This resulted in a loss of separation assurance as both aircraft were at a similar distance, tracking for runway 11, assigned the same altitude, with no assurance that vertical or radar separation would be maintained.

The approach controller then handed over to another approach controller, explained that both aircraft were on descent to 3,000 ft, and advised the incoming controller to monitor the situation.

When ANW was about 19 NM from the airfield, the controller instructed the pilot to turn left onto a heading of 360° and about 20 seconds later advised the pilot of ANW that relevant traffic was a Qantas 737, about 6 NM ahead, and to report sighting that aircraft.

The controller then received a ‘predicted conflict alert’ (PCA) on their situation data display. The pilot of ANW then reported having the 737 in sight and the controller instructed the pilot of ANW to follow the 737 and cleared ANW for a visual approach to runway 11.

When the PCA sounded, about 1,300 ft of vertical separation and 4.5 NM laterally existed between the two aircraft. As the radar separation standard of 3 NM laterally and 1,000 ft vertically applied at the time, a loss of separation between the aircraft did not occur.

This incident highlights the importance of having tactical separation assurance in place at all times.


Aviation Short Investigations Bulletin - Issue 34

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[ Download PDF: 331KB]
General details
Date: 02 June 2014 Investigation status: Completed 
Time: 1138 CST  
Location   (show map):near Darwin Airport Investigation type: Occurrence Investigation 
State: Northern Territory Occurrence type: Loss of separation assurance 
Release date: 03 September 2014 Occurrence class: Airspace 
Report status: Final Occurrence category: Incident 
 Highest injury level: None 
Aircraft 1 details
Aircraft manufacturer: Fairchild Industries Inc 
Aircraft model: SA227-DC 
Aircraft registration: VH-ANW 
Serial number: DC-873B 
Operator: Capiteq 
Type of operation: Air Transport Low Capacity 
Sector: Turboprop 
Damage to aircraft: Nil 
Destination:Darwin, NT
Aircraft 2 details
Aircraft manufacturer: The Boeing Company 
Aircraft model: 737-838 
Aircraft registration: VH-XZA 
Serial number: 39367 
Operator: Qantas 
Type of operation: Air Transport High Capacity 
Sector: Jet 
Damage to aircraft: Nil 
Departure point:Melbourne, Vic.
Destination:Darwin, NT
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Last update 25 February 2015