Originally Posted by
CaptainMidnight
Those worried about 500FT vertical separation, have a look at ERSA for Sydney's chopper and Victor One VFR routes.
500 ft on Victor 1? The charts seem to show traffic into Sydney crossing Victor 1 at 1600', so about 1100' clearance - double what the Melbourne coastal route will have.
Victor 1 is 5 miles from and 500' above the threshold. The Melbourne coastal route is 10 miles from and 1700' above the threshold - and traffic may be (will be?) below the glide slope at that distance by design.
Information on wake turbulence says it descends to somewhere between 500 and 900 feet below the flight path. 1000 feet is considered adequate vertical separation. 500 feet is not.
Looking at the numbers, I would guess Victor 1 was designed so the Sydney approach was at least 1000' above the base of CTA. In Melbourne, the consultation material explicitly said 500 feet was all that was required - but that was based on the minimum in the regulations to protect aircraft in CTA, not safety. Melbourne will be like Victor 1 - if you busted airspace by 500 feet on Victor 1.
You have convinced me that the approaches via BOLTY/OBGAL are not the issue, it is only the one through ESLOK that crosses the route.
You know what they say about seeking forgiveness and asking permission... I have the feeling that they wanted 1000 or 1500 feet CTA base for the GLS approach, but knew that if they asked permission they would meet a lot of opposition. On the other hand, once the GLS approach is published, they can implement a restricted area on short notice or change the airspace steps much more easily for "safety reasons" (GA aircraft not perfectly holding altitude and causing TCAS RAs, people flying in the wrong direction/wrong altitude in proximity to the approach etc.). Then it is GA's fault because they can't follow the published procedures, and you can't shut down a Melbourne airport approach for GA's convenience.
Time will tell if I'm right or wrong. If GA are still transiting OCTA at 2000 a few years from now, I was wrong. If the CTA LL is dropped further to accommodate the approach, my prediction was correct.
(I actually support the GLS approach into Melbourne. If that is the safest and most efficient approach, and it requires that airspace then obviously Melbourne airport traffic should have priority. However, if they take that airspace away, Airservices should make it much easier to transit in CTA i.e. make clearances available through CTA for the majority of the traffic that currently uses the route. That would be a safer option overall, but I believe that Airservices do not want to process GA traffic through CTA.)