Hi All,
Im new to VATSIM and wanted a clarification on Top Down ATC. I understand it in concept, but my question is on frequency selection.
By way of example, lets say I spawn on the ground at Hanscom Airfield, Mass USA (KBED). A TERM ctrlr is online at KBOS and KBED is under their airspace.
I would understand that I use the call “Hanscom GND or CLC DLV” on initial contact, and actually talk to the KBOS Terminal controller, but is that terminal controller monitoring the frequencies underneath him, in this case 121.7 for Hanscom Ground? By the observation that I did the other night it appears that “all” comms with this controller is done on the KBOS frequency. Is this correct? If so, understandable for staffing limitations in the simulated world, but also breaks the illusion somewhat to a small degree.
I suppose a good comprimise might be to use comm 2 for VATSIM transmissions, but for training purposes switch “legitimate” published frequencies in Comm 1 and just pretend thats the active frequency.
Hi Adrian, and welcome to VATSIM.
Of course, we have to bend reality a bit to accommodate the hobby environment, where everyone is a volunteer, participating as they have time and interest.
In our top-down environment, you would call the controller that is “above” the real-world (RW) position you would normally contact.
In your example, you mentioned “Terminal”. Though I know what that means from a US FAA ATC perspective, in our environment we typically would refer to “Center” or “Approach” or “Departure”.
So… in the case if you at KBED, if BOS_APP (or A90_APP) were online, you’d call them (normally 133.00) and would refer to them as Boston Approach. If Boston Approach (or A90) were not online, but Boston Center was (normally 134.70), you’d call them, and call them Boston Center.
No, the higher level ATC is typically not monitoring or using frequencies subordinate to their position. In your example, if only one Boston Center sector were online, that would mean that they would have to monitor at least 244 frequencies. Not something we want to spend the bandwidth dollars on, nor would there be tangible benefit for the network. And it would probably kill the controllers 
In our environment, with top-down service, we would NOT do as you suggested; we would simply call an online controller, with their correct callsign, and allow them to simulate all control positions (workload permitting) at and under their purview.
It’s not perfect, but it works for our community.
I hope this helps, and again, welcome!
Thanks Don, thats great thank you for taking the time with a great and thorough response. It all seems reasonable, Im enthusiastic to get involved in such a fascinating environment.
As a follow up, Im reading im the VATSIM documents to treat unconttolled airspace as UNICOM standardized to 122.8. Does that mean in a situation like this that I would broadcast intentions on 122.8 while 2200’AGL and below? Probably not best practice in this case but Im uncertain.
Im guessing another tactic is to be upfont with intentions. Having the airport diagram up in front of me, and knowing the most sensible ground taxi routing to the into-wind rwy, my initial call could be, “BOS DEP, is on the GA ramp in Hascom, request taxi C, E, for VFR departure RWY 29”. To which Id expect the reply to be, “Roger <c/s>, taxi as requested contact me when ready for departure”
This essentially brings me to my last thought, which is, what happens when a controller has too much on his plate? How is this handled?
Thanks again.
Hey Adrian, so I’m an S3 controller in Australia so I have a bit of an insight into this albeit not as much as more experienced controllers.
You’d only use UNICOM if you were actually in uncontrolled airspace.If a controller is providing full top down then they count as the controller at all levels. From clearance to taxi to takeoff.
And generally speaking you wouldn’t need to supply a taxi route to them even if operating top down. Especially if we’re talking about a terminal controller. One thing I do always add when I’m talking to a controller who is handling multiple airports is where I am, always on the first contact at least. So. “Boston Departure, Qantas 412 on the ground Hanscom requesting IFR clearance to Sydney”. Of course if you’re VFR there will be differences obviously but still. Just treat it like there’s a delivery, ground and tower controller.
As for the final part of your question a lot of the top down stuff is covered as traffic permits. I can’t speak for the Boston ARTCC’s operations policy but referring to ours in VATPAC we have a few lines about that.
If Tower for the primary aerodrome under a terminal control area is unavailable, the controller of the Approach position shall assume responsibility of all of the aerodrome control functions at that aerodrome, provided traffic load permits.
The four words are the important part here. The same thing is there for the en-route top-down coverage. Our primary responsibility is our own position. Ideally, you’ll run everything but just say I’m handling Sydney Approach and traffic is getting crazy without anyone beneath me I may have to withdraw top-down coverage to make sure I can provide a decent service to the people I’m handling in the air. It might not be a full withdrawal but it might just be ground movement. I can still give clearance and then tell them to contact me at the holding point.