J_A_K and GB, you're welcome.
J_A_K, The wait does seem excessive, but when we try to reduce it things can go pear-shaped pretty quickly and we (the royal "we") end up in a recovery situation - I've seen it happen.
If we try to play unders and overs by holding the departure down, then obviously the departure's climb is inhibited which then restricts when and where it can turn and track over built-up areas because of noise abatement minimum altitude requirements. It also may run out of controlled airspace, which is a no-no for us. If you let the departure climb then you have to push the arrival down to slip under him, usually well below profile height miles away from the airport, over water.
It's extremely poor technique to have piston lighties miles out over water at low level, so within the procedures we're given we minimise that as much as we can. A Sy-Cootamundra flight is not an over-water flight - you wouldn't be carrying life jackets, would you?
Depending on aircraft types, wake turbulence separation can be a factor - the margin by which we aim to make them miss has to be bigger - 2 minutes at 240kt is 8 miles, nearly 3 times the normal radar standard, and that has to be fed into the equation.
In the traffic situation you described the mix of types is significant just for the timing. A PA31 or C310 departing with a BA146 coming down the coast, the cut-off would be on or north of the 07 extended centreline, so you're looking at about 30 track miles for the 146 at least, about 8 minutes.
A Westwind departing with a 146 or something slower coming down the coast, you could play it tighter - WWs go like $%^& off a shiny shovel and will quickly be out of conflict.
Now there's an interesting aircraft! I've seen one of them on a 12 mile base leg at 400kt GS.
'course, if there's a few arrivals in succession there's not much we can do, except maybe try to bunch the arrivals up and get them on the ground as quickly as possible to give the departures a run.
No-one likes the curfew procedures. The inefficiency you speak of (long delays on the ground) is an issue for all of us, except, apparently, for the pollies and noise lobby. They don't care.
I've heard a suggestion that the curfew hours be divided into arrival blocks and departure blocks which would be published and you time your operation to suit - I guess that's one way of managing the situation but I don't know how well it would work. I can see problems with it.
There are safety issues in the present set-up as well, regardless of how the delays are managed - human factors for us as ATCs and, for aircraft, low level over water a long way from land.
What we would like to see is 16L for departures, with a turn out through Botany Bay heads, and 34L arrivals. We already have procedures and standards to allow simultaneous arrivals and departures in that configuration. However, the environmentalists at this stage say no. They see it as the industry applying the thin edge of the wedge and they won't give ground. They have a huge mistrust of all of us in the industry and seem to forget that their own legislation won't allow the wedge to be driven and the situation to get out of hand - all the "noisy" aircraft are defined and on a legislated movement quota.
There are no votes in it, so it's difficult to get a good hearing in the corridors where it matters.
AA
Last edited by Ausatco; 15th Sep 2003 at 15:28.