by Eric Stearns
Controlled airports generally follow the same procedures for arriving and departing traffic. It's important to know who to contact for what, and what to expect when you do talk to them. The procedures can vary slight depending on whether you are an IFR or VFR flight; those differences will be covered as needed.
Hierarchy of controllers
In the RW, the hierarchy of controllers is very clear. As a compromise to the relatively low traffic volume and small number of controllers, VATSIM controllers often work positions they would not in the RW. For example, MSP_CTR will work MSP_TWR if the position is not manned by another controller.
When departing an airport and deciding who to contact look for controllers in the following order:
1.DEL (clearance delivery)
TWR controllers will almost always only work one airport (one exception is BAY_TWR in Oakland Center; BAY_TWR works SFO, OAK, and SJC_TWRs). So a departure from KTEB (Teterboro, New Jersey) would not talk to EWR_TWR (Newark Tower), even though the airports are only about 5 miles apart.
If the TWR position is not manned, it might be served by the APP controller above. If you're departing a busy airport like EGLL, it's a safe bet that EGLL_APP will work EGLL_TWR if it's not manned.
There are trickier parts of APP controllers though. It's becoming more common for there to be consolidated approach controls, which cover large areas, in the RW. Examples are SFO_APP and LAX_APP. SFO_APP, when he/she is the only controller online, controls the airspace from MRY all the way up north of SMF. So SMF or MRY departures should contact SFO_APP for departure (if SMF or MRY_APP are not open). LAX_APP controls the airspace from the Mexican border up to about 20 miles north of BUR. If you're in doubt, consult that ARTCCs website or ask the controller in question if he/she is working your departure airport.
If there are no APP controllers online in your area, the next step up is the CTR controller. CTR boundaries are available on servinfo and from numerous other sources.
CTR and APP controllers won't always work every tower within their airspace. If he/she is not working a particular tower, the controller will advise you of that. In that case, the airport will be treated as an uncontrolled airport. IFR departures from uncontrolled airports are addressed in other lessons.
Clearance Delivery (CD)
This controller will use a VATSIM position ID format of XXX_DEL; for example, YYZ_DEL would be the clearance delivery controller at Toronto (An "S" in the middle [YYZ_S_DEL] would indicate a student; "M" or "I" would indicate mentor or instructor).
CD controllers generally do not control any physical space on an airport; they're sole purpose is to issue clearances to IFR aircraft. In the real world, CD controllers will issue VFR clearances (if required) as well; this isn't always true on VATSIM, but a VFR aircraft should start by calling CD. All IFR flights departing an airport with a CD controller should contact that controller first. He/she will issue the IFR clearance and may have additional instructions.
Ground controllers use the VATSIM position format of XXX_GND.
Ground controllers are responsible for most taxiways and at busier airports they also sequence departures for maximum efficiency. There are some exceptions to this; the TWR controller will sometimes control taxiways where it is advantageous for him/her to do so. For example, the taxiways between closely spaced parallel runways are generally controlled by tower controllers (e.g. 27L/R at ATL, 28L/R at SFO, 30L/R at STL, etc). For this reason, after landing always wait to contact ground control until you are instructed to do so by the tower controller. If it seems that he has forgotten you, feel free to query the tower controller as to whether or not he wants you to contact ground.
If there is no DEL controller online, the GND controller will provide DEL services.
Tower controllers use the VATSIM position format of XXX_TWR.
Generally, tower controllers are responsible for separation of aircraft on runways and also airspace in the vicinity of an airport. A typical tower might control the airspace within a 5 nautical mile radius up to an altitude of 3000' above the ground. These numbers vary greatly by region and even between towers in a certain region. If you're inbound to an airport with a tower and talking to an APP or CTR controller, that controller will instruct you to contact the tower at the appropriate time. After landing, remain on the tower frequency until instructed to contact the ground controller.
On departure, switch from ground to tower when you're approaching the runway end. Some ground controllers might instruct you to switch to tower at an appropriate time. During a busy event, you might be instructed to "monitor tower"; in that case the tower controller is aware of your sequence and will call you...there's no need to report that you're on the frequency.