ANSP info/procedural error involving a Piper PA-24-250, VH-PJM and Piper PA-31-350, VH-XMM, Tottenham, New South Wales, on 3 September 1996

The pilot of VH-PJM was enroute Forbes to Brewarrina at 6,000 ft initially estimating Nyngan at 0941 EST but later revised the estimate to 0931. The pilot of VH-XMM was enroute Walgett to Hamilton at 6,000 ft initially estimating Tottenham at 0910 but revised the estimate twice, the last being 0921. Based on the original flight plan/ flight progress strip estimates for both aircraft, the time of passing in the Tottenham area would have been 0905 with PJM approximately 45 NM south-south-east of XMM.

The pilots revised their estimates enroute because XMM encountered a headwind component whereas PJM encountered a tailwind component. However, by the time the Flight Service operator had passed traffic information to both pilots, both aircraft had passed within 5 NM of each other at 6,000 ft.

The Flight Service operator advised that at the time of the breakdown in separation his traffic workload was fairly high. He failed to realise that the revised estimates placed both aircraft in the Tottenham area at approximately the same time.