I think we are a bit off the Class E track but you are now talking about a favourite subject of mine, and they are all inter-related!
The whole argument about when a Tower should be "required" is to my mind, far too prescriptive and bureaucratic. It also, I believe, leads to active neglect of air traffic hotspots caused by the mix of traffic as aerodromes develop their operations.
The requirements for a CASA review of whether a Tower is required can be found in the Australian Airspace Policy Statement (currently 25 Sep 2018). For Class D airspace with an ATC service, which implies, but does not state, a Control Tower, the threshold criteria are:
- Total Annual Aircraft Movements 80,000
- Total Passenger Transport Movements 15, 000
- Total Annual Public Transport Passengers 350,000
Hence none of the so-called Metro D airports should have Towers, and indeed paragraph 21 states that CASA should consider downgrading them. Of course, we know that would never happen because of the political fallout if there was a subsequent accident, but what about the aerodromes that have traffic mix issues but never seem to get recommended for an upgrade?
To my mind, in a free market economy, aerodrome operators should be the ones deciding whether they would like a Control Tower, not a Federal Authority. I believe that the airspace surrounding an aerodrome should be considered an asset available to the aerodrome in order to pursue plans for development. Ballina has been mentioned above, and it is a great example, but there are others I have read about where the aerodrome has attracted international pilot training, and those basic-english students are now interacting with Dash 8 or F70/100 RPT movements. Another example is Wellcamp, 10NM west of TWB in Queensland. The owners are very entrepreneurial and have built a magnificent multi-purpose airport. They have attracted a Qantas pilot training school and have RPT operations plus weekly Cathay Pacific and Singapore Airlines freight flights. The aerodrome airspace is constrained on three sides by military R Areas (IMO unnecessary - don't get me started!) which funnel GA aircraft over Wellcamp. Should this complexity have some ATC oversight, of course, but it does not meet the MInister's threshold requirements. I believe the aerodrome owners should be able to establish their own control tower, if necessary, initially in Class G airspace, and then request Class D from CASA when real statistics and collision risks have been locally assessed. Is this possible in Australia, yes, but only with the permission of Airservices (CASR Part 172), that is another Federal Bureaucracy! I am told that Airservices has no intention of building any more control towers. It wishes to be seen to be on the cutting edge of ATC technology by introducing Remote or Digital Aerodrome Services. Good luck with that if my NBN service is anything to go by!
It is perplexing to me that the Government, CASA, and Airservices seem to be very happy to rely on a USAF satellite system for sole-source IFR navigation, to contemplate a private US company, Aireon, providing ADS-B surveillance of Australia under contract, but not let Australian aerodrome operators run a simple Control Tower!