The aircraft was carrying out calibrations of the RAAF Richmond Tacan transmitter and was planned to track out from Richmond on the 143 degree radial for 25 nm, track north-east to intercept the 108 degree radial at a point 25 nm from Richmond then to track inbound to Richmond on the 108 degree radial, flying all legs at 2 000 feet. Toward the end of the outbound leg, the pilot called Sydney Flight Service for clearance to enter the Sydney Control Zone. Before clearance was available, the aircraft penetrated Sydney controlled airspace over Bankstown Aerodrome, causing a breakdown of separation with another aircraft departing Bankstown on a Standard Instrument Departure. The pilot was instructed to call Bankstown Tower, which, after confirming the aircraft's altitude as 2 000 feet, instructed the aircraft to hold over Bankstown until onward clearance was available. The pilot was unaware that the lower limit of the Sydney Control Area was 1 500 feet over Bankstown Aerodrome, believing that the lower limit was 2 000 feet (as it is to the west of Bankstown), and that the aircraft was outside controlled airspace. This incident was not the subject of an on-scene investigation.