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At about 1142 Eastern Standard Time on 26 September 2011, two Beech A36 (Bonanza) aircraft, registered VH-IOL (IOL) and VH-YEN (YEN), operating under the Visual Flight Rules in G airspace, came into close proximity near Ravensworth, New South Wales, at 2,700 ft above mean sea level. The pilot of IOL was successfully alerted by Brisbane air traffic service (ATS), in time to see the other aircraft and initiate an avoidance manoeuvre. The pilot of YEN had not been monitoring that radio frequency and never saw the other aircraft. IOL was equipped with a portable collision avoidance system but the pilot had switched it off because of ground-based machinery interference.

The chance of a successful avoidance manoeuvre was increased because one of the pilots had been successfully alerted by ATS. The alert occurred because both aircraft had transponders active on Mode C, enabling ATS to be aware of the proximity between the two aircraft.

The incident highlights the safety benefits for pilots to maintain an active listening watch on the appropriate radio frequency. Traffic information from any source can direct the attention of pilots to help them 'see-and-avoid' other aircraft in the vicinity.

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