Final Report


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

Read report