Latest version of CAR 166, Rules of the Air,
g).before landing, descend in a straight line starting at least 500
metres from the threshold of the landing runway and at a distance
common to the ordinary course of navigation for the aircraft type;
I havent owned CAR's or CAO's in a loooooong time mate, All this stuff is available, including AIP's, for free, from CASA website and Airservices Australia website.