Aviation safety investigations & reports

Loss of separation assurance involving a Boeing 737, VH-XZA and a Fairchild SA227, VH-ANW, near Darwin Airport, NT on 2 June 2014

Investigation number:
Status: Completed
Investigation completed


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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

Download Final Report
[Download  PDF: 331KB]
Alternate: [Download  DOCX: 325KB]
General details
Date: 02 June 2014   Investigation status: Completed  
Time: 1138 CST   Investigation level: Short - click for an explanation of investigation levels  
Location   (show map): near Darwin Airport    
State: Northern Territory   Occurrence type: Loss of separation assurance  
Release date: 03 September 2014   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft 1 details

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 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  
Last update 14 November 2018