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« on: February 09, 2011, 08:35:12 PM »
Good lord we're over-thinking this.
If center needs 10-in-trail, same route, that departure restriction is put back down all the way to the tower, period. It would be an incredible and completely unnecessary amount of work for a departure or center to vector a long-string of aircraft to get from 5 to 10 in trail when tower could have provided the initial separation right at departure time. Delays on the ground are MUCH easier on the system as a whole, and 10 miles does not a significant delay make.
Tower can and does use radar to determine in-trail spacing. No need to think so much in terms of time, particularly on the network here.
No need to make a primary Class B or C tower call for release except in extraordinary circumstances (particularly extraordinary for VATSIM).
If it's a solid line of planes going to the same place (as it often is on VATSIM for fly-ins), ensure tower has the appropriate departure restrictions, and they can watch the radar... when one guy is 7-8 miles in the direction of the restriction, launch the next guy, runway barely matters, unless it's an opposite direction runway, then launch em a mile or two earlier. By the time the 2nd gets airborne, the first one is already at about the 10 miles. If tower launches one a little too tight, then he/she should wait a little longer on the next one to give departure a ~20 mile gap to stick the middle guy in.
Always better to have a little more than a little less when it comes to in-trail spacing. Of course, not excessively more.
Speed restrictions SUCK on VATSIM for the simple fact that every other plane has different winds aloft (oh how I wish there was a way to make it truly uniform for all connected). In all though, not terribly dis-similar to real life. Building in-trail from a fan of aircraft, wind is pushing from different directions relative to the ultimate direction of travel. Adjust mach numbers based on ground speed. .01 mach ~= 6 knots. Set an anchor point and use the mileage count. When everyone has the same ground speed when going direct the point for in-trail, relative distance doesn't change. In the end though, basic rule is vectors to get space, speed to keep it. If wind is bad, try to vector everyone to approximately the same line to minimize impact of relative wind.
Some closing points.
I would personally look in to getting rid of that static 10 NM restriction... if planes are separated, they're separated. If the next controller needs in-trail for whatever reason, then coordinate as appropriate. Otherwise, it's kind of a waste of airspace, and for day-to-day operations, well... I won't go further in to it here.
Real life controllers may never deal with 20 departures from one airport going the same exact route to the same destination, but there are plenty of examples of aircraft exiting the TRACON on the same route to the center. The solution usually starts with GROUND control in most cases, and planes are taxied to the runway in a sequence that precludes two successive departures going to the same fix. Knowing VATSIM isn't like this though for typical events... best to just advise the pilots to expect a short delay waiting on/holding short of the departure runway for in-trail spacing.
Nice videos, and they get the point across... but for others, remember to think that departure may not have the luxury of cranking around quite so much or climbing above 100 to get the lead guy up to speed as fast when arrival traffic is heavy. Denver's got clean, clean airspace... most other places don't have it quite so nice.
~Nate
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