Once more into the fray !!
Four Seven Eleven, you state:
"I am at a loss as to what economic or other benefit will be achieved by exposing a B747 on descent into Sydney, or a B717 climbing out of Hobart, to the possibility of unknown, non-communication traffic, where a full separation service currently exists."
Economic benefit? Perhaps it's saving VFR aircraft from flying large extra distances over tiger country when denied a clearance into non-radar terminal Class C.
Let's look at an example. A VFR aircraft is tracking at 8,500' overhead Launceston, Hobart to Port Davy in south-west Tasmania, where it requires a clearance into the Hobart Class C procedural airspace. What does the controller do when there is already an RPT jet descending into Hobart from the north? As the separation standard is, I believe, something like 10 minutes or 30 miles ( plus a bit for Mum and the kids) for a Baron doing 180 knots, the VFR aircraft cannot normally be given a radial or a DME distance or a geographical fix to track by, surely the standard thing would be for the air traffic controller to tell the VFR aircraft - perhaps a commercial charter operator to "remain OCTA". That, is indeed, what normally happens, large extra distances are flown, while totally extraordinary separation standards from the 1940s are kept.
I haven’t checked the schedules for the Apple Ilse for a while, but I recall that tower hours did not always cover RPT movements, and the RPT operators were more than somewhat disinclined to pay to have the tower hours extended, when commercial demand changed the airline schedules. So much for the Class C or whatever protection as an article of faith.
I've seen it happen at Wagga before the tower was removed and currently at Tamworth, ie VFR aircraft are told to remain OCTA and fly very substantial extra distances because Class C terminal airspace is actually designed for a radar environment. It happens to me continually at Coffs Harbour, if there is an RPT movement, the alternative, really long delays or an invitation to disappear off towards the high ground. I am still conservative enough that I carefully consider where I fly single engine. The probability of an engine failure is several orders of magnitude more likely than an “in air encounter”.
Former CEO of Air Services, Bill Pollard, after a third glass of red, often warmed to a favorite subject, why on earth we wanted to have all the inflexibility of trying to use a “radar” class of airspace, C, without radar, particularly with the miniscule local traffic levels.
It is the miniscule traffic level that is the reason why there are not totally unacceptable commercial delays.
So there you have it, the reason it works at all is the same reason it’s not needed, there’s sod all traffic (by real world standards) in this (and most other Australian) airspace.
Straight out of the ACT Textbook, "Alice in Wonderland".
Tootle pip !!