VH-OZV departed Moorabbin from runway 35L and after making a left turn, commenced tracking in a southerly direction on climb to 9,000 ft. Three miles south of Moorabbin the pilot called RAS, but the aircraft was not identified because its transponder was not being interrogated. The RAS controller passed traffic information to the pilot of OZV on an aircraft two miles at 12 o'clock, also with no transponder return. The pilot of OZV sighted the other aircraft in his 11 o'clock position, 100 to 200 ft higher. He took evasive action, in the form of a left turn, to avoid a collision.
The conflicting aircraft was later identified as VH-PWQ, whose transponder suddenly started operating after traffic information was passed to OZV. The pilot of PWQ said that he flies from Berwick to Ballarat, as he was on this occasion, once a week, and transits via the coast south of Moorabbin at 2500 ft. He listens out on RAS and the appropriate Moorabbin tower frequency for traffic. However, he did not make a broadcast of his position, altitude and intentions on the Moorabbin tower frequency, as is required by AIP OPS 42.2.1. He heard OZV departing Moorabbin but never saw it, even when they passed in close proximity.
