The pilot was conducting the final stage of a night freight flight from Melbourne to Hobart and return. Because of traffic in the Melbourne/Essendon area, the aircraft was radar vectored to the south of Essendon. In the vicinity of the Westgate Bridge the pilot was instructed to carry out two orbits, in order to facilitate his approach to Melbourne. These orbits were conducted with the aircraft in cloud. The pilot was then instructed to take up a north-westerly heading, and to descend to 2000 feet (above mean sea level). On gaining visual contact with the ground, the pilot saw an aerodrome ahead, which he assumed was Melbourne. The aircraft was too high for a direct approach to this aerodrome, and the pilot requested approval to carry out a further orbit. The aircraft was advised to take up a westerly heading, and the pilot was instructed to call the Melbourne Tower controller. The Tower controller at Essendon was aware that the aircraft was enroute to Melbourne. After he observed the aircraft passing abeam Essendon, he cleared a waiting aircraft to take-off into the south. Shortly afterwards, he saw the first aircraft commence a descending turn to the left and track towards Essendon. The controller alerted the Melbourne Tower controller to the situation, and instructed the aircraft which had just become airborne to turn to the left. The pilot of this aircraft saw the approaching aircraft, and adjusted his flight path accordingly. The two aircraft passed with about 200 feet of vertical separation, and were some 200 metres apart horizontally. Melbourne Tower advised the inbound pilot he was tracking for the wrong aerodrome, and instructed him to carry out a go around. At this time the pilot realised his error, and the remainder of the flight was uneventful. It was determined that the pilot had become disorientated as he gained visual contact with the ground. When he sighted an aerodrome, he had a fixation that it was Melbourne, and he had disregarded visual and aural cues that he was proceeding to the wrong aerodrome. He was not familiar with the area, and it is highly likely that he was suffering the effects of fatigue.
