David Luff writes: > With regard to ATC, there's at least one other person working on it > besides myself, but AFAIK no-one is attempting to model centre > control - I might have the terminology wrong there but I'm > referring to control of the airways away from airfield > tower/approach/departure control.
Here's how things work in Canada... Control zones are quite small -- usually about a 5-7 nm radius around an airport up to 3000 ft AGL and are class C if there's a tower with radar or class E if there's not. A terminal area (I think the Americans still call it a TRACON) usually has around a 25 nm radius up to, say, 10,000 ft (I don't have the charts with me to check) with increasingly high floors as it moves out, sort-of like an upside-down wedding cake. Terminal areas are most often class D, so everyone (VFR and IFR) still has to get ATC clearances but ATC does not provide positive separation for VFR. Outside of control zones and terminal areas at the lower altitudes we have class E airspace along the airways and terminal area extensions (major approach paths into the terminal areas) and mostly class G elsewhere; I understand that there's little class G in the U.S. In class E, IFR traffic has to be talking to ATC (usually the centre controller), but VFR traffic acts mostly as if it's in class G, except for increased visual minima. VFR traffic can request flight following outside of a terminal area, in which case it talks to centre just like IFR traffic but simply informs center of what it is going to do instead of requesting a clearance (even centre gets confused -- when I inform them that I'm going to climb or descend during VFR flight following, I still sometimes get back "<new altitude> approved"). In reality, things are even more complicated; for example, Ottawa terminal has taken over en-route most of the way to Toronto, so almost 100nm out of the Ottawa terminal area I'm still talking to Ottawa terminal for flight following instead of Toronto Centre. Ottawa terminal airspace sort-of collides with Montreal terminal airspace, and there's a pie-shaped chunk carved out of Ottawa terminal airspace up to 4000 ft in the northwest to provide an uncontrolled practice area. There are often also low-altitude corridors to allow planes to fly in and out of satellite airports without having to enter the class C or D airspace of the terminal area or control zone. The charts (U.S. sectional or Canadian VNC) are fascinating reading once you start to get the hang of them. > Additionally, if you're into graphs, movement, shortest paths > and all that, which is classical sort of AI stuff really, then there's > plenty of that to be sorted to get ground control working robustly. I'm > plugging away at some textbooks now, but there's lots of work in that > that could be spread about. If you read the online aviation discussion forums in the U.S., you'll get the impression that ATC has little to do with shortest paths, either in the air or on the ground. My experience up here has been different, but I don't know how much of that has to do with real differences and how much is cultural (parts of the U.S. have a long-standing cultural paranoia about authority, while we still happily put ER II's face on our money up here). All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
