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Early in the afternoon on 4 June 2015, a Pacific Aerospace CT/4B, registered VH‑YCU (YCU), was tracking towards Quirindi from the north, at 4,500 ft. At the same time, a Diamond DA 40, registered VH‑UNV (UNV), was also tracking towards Quirindi. UNV was approaching Quirindi from the north‑east, and was also at 4,500 ft. Both aircraft were operating under the visual flight rules, and the weather conditions were fine and clear.

The crew of YCU broadcast their position and intentions on the Quirindi Common Traffic Advisory Frequency (CTAF), but the crew of UNV were not monitoring that frequency. Both crews were monitoring the area frequency, but there was no requirement for either of them to broadcast on that frequency. As such, neither crew was aware of the other aircraft as they approached Quirindi.

Just north of Quirindi, the traffic collision avoidance device fitted to YCU alerted the crew to an aircraft in their vicinity. The crew of YCU then sighted UNV, slightly ahead and to their left, at the same altitude. The crew assessed that the two aircraft were on a slightly converging flight path. Although there was no immediate risk if a collision, the crew of YCU made a heading adjustment through about 20 degrees to the right to ensure that the flight path of the two aircraft would diverge.

The requirement to monitor a CTAF is subject to a level of interpretation, particularly with respect to the altitude above an airfield at which the requirement applies. Nonetheless, pilots are encouraged to ‘err on the side of caution’ when considering when to make broadcasts and whether specific frequencies should be monitored, particularly noting the fundamental importance of communication in the effective application of the principles of see-and-avoid. Insufficient communication between pilots operating in the same area is the most common cause of safety incidents near non-controlled aerodromes.


Aviation Short Investigations Bulletin Issue 44

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General details
Date: 04 June 2015 Investigation status: Completed 
Time: 1420 EST  
Location   (show map):Quirindi Airport Investigation type: Occurrence Investigation 
State: New South Wales Occurrence type: Separation issue 
Release date: 04 November 2015 Occurrence class: Operational 
Report status: Final Occurrence category: Incident 
 Highest injury level: None 
Aircraft 1 details
Aircraft manufacturer: Pacific Aerospace Corporation 
Aircraft model: CT/4B 
Aircraft registration: VH-YCU 
Serial number: 079 
Type of operation: Flying Training 
Sector: Piston 
Damage to aircraft: Nil 
Departure point:Tamworth, NSW
Destination:Tamworth, NSW
Aircraft 2 details
Aircraft manufacturer: Diamond Aircraft Industries 
Aircraft model: DA 40 
Aircraft registration: VH-UNV 
Serial number: 40.1077 
Type of operation: Flying Training 
Sector: Piston 
Damage to aircraft: Nil 
Departure point:Bankstown, NSW
Destination:Bankstown, NSW
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Last update 17 October 2017