Separation issue involving a Beech Aircraft Corp 200, VH-SKN and Beech Aircraft Corp C90, VH-FDM, 96km NW Boulia, (ALA), QLD on 15 August 1997

The pilot of VH-SKN reported that, while cruising FL170 some 52NM from Boulia, a VFR aircraft (VH-FDM) reported 49NM from Boulia, on the same track, leaving FL175 on descent. SKN had been advised of several IFR aircraft by Flight Service, but had not received any broadcasts from VFR traffic until the descent call from FDM. The pilot of SKN considered that the three mile separation which existed between his aircraft and FDM compromised safety. FDM departed Mt Isa 5-10 minutes before SKN and thus should have been aware that SKN was tracking for Boulia. Both aircraft were King-Air variants, but had a significant performance margin over FDM and it was this which contributed to SKN catching up to FDM during the flight.