Aviation safety investigations & reports

Breakdown of separation between a foreign military Boeing 737 and a Cessna 206, VH-RAP, Darwin Airport, Northern Territory on 12 March 2014

Investigation number:
Status: Completed
Investigation completed


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On 12 March 2014, at about 1211 Central Standard Time, the crew of a United States military Boeing 737 aircraft, call sign ‘Convoy 7186’, requested a clearance from the air traffic control (ATC) planner at Darwin Airport, Northern Territory, for a flight to Kadena Air Base, Japan via the ‘A461’ air route.

The planner cleared Convoy 7186 to track to the destination via the ‘OCTOB’ waypoint at 5,000 ft above mean sea level (AMSL) and for an ‘OCTOB TWO’ standard instrument departure (SID).

At about 1245, the tower controller cleared the pilot of a Cessna 206 aircraft, registered VH-RAP (RAP), for take-off from runway 29 at Darwin, then to turn right onto a heading of 320° and climb to 3,000 ft AMSL.

The crew of Convoy 7186 then contacted the tower approaching the holding point for runway 29 and requested an ‘IFR release’. The tower controller asked the crew to repeat the call. The crew stated that they wanted to verify they were ‘direct OCTOB on the go, up to 5,000’. The tower controller replied ‘Affirm’.

At about 1248, the approach controller identified RAP and requested the pilot to maintain 2,000 ft to guarantee separation assurance with the following aircraft. Shortly after, the crew of Convoy 7186 contacted the approach controller and advised they were passing 2,000 ft on climb to 5,000 ft and tracking direct to OCTOB.

The approach controller immediately issued a safety alert and advised the crew that there was a VFR aircraft at 2,000 ft about 1 NM ahead and that Convoy 7186 was cleared on an OCTOB TWO departure. The crew replied, ‘Negative, it’s direct to OCTOB on the go’ and advised that they had the VFR aircraft in sight.

This incident highlights the importance of using standard phraseology in all radio communications.


Aviation Short Investigations Bulletin - Issue 32

Download Final Report
[Download  PDF: 290KB]
Alternate: [Download  DOCX: 385KB]
General details
Date: 12 March 2014   Investigation status: Completed  
Time: 1250 CST   Investigation level: Short - click for an explanation of investigation levels  
Location   (show map): Darwin Airport    
State: Northern Territory   Occurrence type: Loss of separation  
Release date: 14 July 2014   Occurrence category: Serious Incident  
Report status: Final   Highest injury level: None  

Aircraft 1 details

Aircraft 1 details
Aircraft manufacturer The Boeing Company  
Aircraft model 737  
Type of operation Military  
Sector Jet  
Damage to aircraft Nil  
Departure point Darwin, NT  

Aircraft 2 details

Aircraft 2 details
Aircraft manufacturer Cessna Aircraft Company  
Aircraft model 206  
Aircraft registration VH-RAP  
Serial number U20602989  
Type of operation Charter  
Sector Piston  
Damage to aircraft Nil  
Departure point Darwin, NT  
Last update 14 November 2018