CASA has given no clear direction on their interpretation of "in the circuit".
However the important part of the CASA directive to ASA is 7(b):
"No ATC may
assume control responsibility for more than 6 aeroplanes......" My italics/underline.
Once you have cleared an aircraft into the CTR/circuit you have effectively "assumed control responsibility", regardless of whether the aircraft is in the "circuit" yet or not, and until that aircraft is on the ground or has left the CTR.
Also you have to allow for the potential go around, so effectively you have to wait for a landing aircraft to have definitely landed or a departing to be established outside the CTR before clearing another aircraft in or out if you have already "capped out".
Thankfully we have TSAD ( a feed off the Sydney Radar ) otherwise we'd have to get aircraft to report established outside the CTR too....and hence more frequency congestion.
And to clarify the matter of who is responsible for these Notams I can definitely assure you it is not us Tower Guys but probably some boffin
in CASA H.O. Canberra who wouldn't know GAAP from a Skim Cappucino.
You will be happy to note though that at about 12.09pm today the "2 minute warning" Notam was cancelled.
Of course that doesn't preclude CASA coming up with yet another even more cunning plan.
IMHO I think you will find that most GAAP controllers would much rather have it back the way it was. It certainly is very frustrating from a professional aspect to be limited by this arbitrary, one-hat-fits-all directive and not be able to provide the level of service that you are capable of delivering. "One hand tied behind your back" does not even begin to cover it.
The management of the "Cap" has become a distracting safety/workload issue i.e. monitoring, counting, manipulating displays etc that takes attention away from the real job of looking out the window and providing a control service. In the context of the YSBK GAAP Tower environment, counting to six is not as simple a task as it may seem on paper!
Unfortunately ATC are as much passengers on this as you pilots, and we too are learning as we go. We are trying our best to work within the limitations imposed and try to accommodate all requests but inevitably there will be times where pilots may incur a significant delay for their operations or they may not be available.
Hopefully this has been a little informative for you all, however these are just my personal opinion and do not necessarily reflect those of my colleagues or employer.(Ask 3 controllers the same question and you'll get 6 opinions! My disclaimer!
)