On 4 June 2010, at about 1345 Eastern Standard Time, a Diamond Aircraft Industries DA40-D (DA40), registered VH-YHM, was travelling in a westerly direction towards Esk, Queensland (Qld), maintaining 2,500 ft. When passing Dayboro, Qld, the DA40 came into close proximity with a Cessna Aircraft Company 172R (C172), registered VH-RQZ, which was descending through 2,500 ft, heading to the south.
The lateral separation between the aircraft was estimated at 10 m, with the DA40 in front of, and slightly below the C172. While the pilots of both aircraft had sighted each other, there was insufficient time to respond and take any action.
The pilots both reported maintaining a visual lookout, but having been temporarily distracted just prior to the incident.
Flights conducted outside controlled airspace (Class G) are not provided with a traffic separation service from air traffic control (ATC). Consequently, maintaining separation is the pilot's responsibility. It is crucial that pilots employ a number of defences to ensure that separation between aircraft is suitably achieved. Applying unalerted and alerted see-and-avoid principles by maintaining a vigilant lookout, and providing and interpreting radio communications will assist in enhancing situational awareness.