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I contribute to an open-source ATC sim, and I'm looking to advance one of our current features. I know this is widely variable, but is there a typical example, either in distance from the airport, or altitude, that I can use to approximate when a pilot would switch to departure?

If you can give me an example of both so I can say "when N123AB climbs through altitude x OR is y miles from the airfield N123AB will contact departure". This would provide some more variation since we have a LOT of different aircraft types in the sim and they've all got different performance. Rates of climb and speeds would have a big impact here. This will be better than saying "after x amount of time N123AB contacts departure". Thanks for your help!

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  • $\begingroup$ There is no typical altitude or distance. There are too many variables. $\endgroup$ Jun 9 at 21:06
  • $\begingroup$ Generally a little bit before you exit class D airspace. $\endgroup$ Jun 10 at 1:27
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    $\begingroup$ What is the open-source ATC sim please? Sounds interesting. $\endgroup$
    – Caltor
    Jun 10 at 9:08
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There is no standardized altitude rule for switching frequencies. This is done at the request of your current controller. If the airport is uncontrolled but you need to switch to a nearby ATC frequency for departure through controlled airspace you do so when you feel you are ready and/or when the local charts state you should do so because of airspace restrictions or other rules.

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  • $\begingroup$ Indeed, if you're flying a small plane, you may never get to the altitude at which that commercial jet switches frequencies. It's really up to the controller, and seems to have more to do with being clear of the airspace departing traffic would use. E.g. in a small plane I might make a turn at about 1000 ft AGL, then be told to switch to departure, while that 737 following me departs straight out until reaching 10K ft or so, and doesn't switch to departure until later. $\endgroup$
    – jamesqf
    Jun 10 at 4:11
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It will be different at every airport and even at different times for the same airport, but if you’re looking for a simple rule to keep things reasonably realistic, I’d go with 1000-1500ft AGL; that’s seems to be when I usually hear it.

If you want to make it annoyingly realistic, I’d say about 20-30 seconds at current climb rate before hitting the initial altitude in the clearance. I pretty consistently check in with Departure and get my next climb just as I’m leveling off.

Note that in some countries, your clearance will tell you to switch on your own when passing some altitude (MSL) rather than being told to by tower, and that’s typically 1000-1500ft AGL as well.

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  • $\begingroup$ At least in central Europe, TWR at bigger airports will typically tell you "when airborne contact Departure" as a part of the takeoff clearance, which means you are supposed to do it as soon as practical (steady climb, gear up, …). TWR doesn't expect to talk to you again (unless your takeoff goes wrong). $\endgroup$
    – TooTea
    Jun 10 at 10:48
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There are two basic scenarios: On some instrument departure routes /SIDs, it is required to stay with the airfield tower controller until after passing a pre-defined fix or until being handed over. When that is not defined, one usually switches over a soon as stabilised in climb with a clean airplane and on track (aviate, navigate, communicate). Usually about 1000-2000 ft AGL. It also does not make sense to switch very early in flight, as sometimes the area controllers do not have radio reception / radar contact with the plane as it is still too close to the ground.

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