I’ve just uploaded some new videos to the official X-Plane YouTube video channel. These videos are screencast tutorials for airport authors to help them understand the ATC Airport Flow feature in X-Plane v10.

ATC Airport Flows are essentially a set of rules that control how the runways are used for airport operations. An airport like Chicago’s O’Hare (KORD) for example has 7 runways (14 different takeoff/landing directions)! ATC does not simply put aircraft wherever they feel like in the moment or there’d be a massive aluminum traffic jam. They have a set of rules that control which runway(s) are in active and inactive at any given time. These rules are typically based on two main criteria: weather conditions and time of day.

In the real world, at major airports, traffic studies are done to decide which runway combinations are most efficient for traffic flow, safety and workload and those combinations of runways become active when the conditions are just right.

Once the controller deems certain runways active/inactive for the current conditions, there are yet more rules to determine which types of aircraft use each of those runways. For example, if a small Pilatus is flying into KORD, I strongly doubt they’re going to block up their major runways for arrivals for a small single engine turbo prop. They’re likely to put him on a smaller accessory runway. Also consider some airports which only use certain runways for arrivals while other runways are only used for departures. This is often done for noise abatement or obstacle avoidance. These types of rules can be included in the ATC Airport Flow.

Our goal was to give authors enough granularity to closely mimic the way real airports are run so that when X-Plane’s ATC is in action, it’s towers can make similar decisions to the real controllers.

Part 1 of 4

Part 2 of 4

Part 3 of 4

Part 4 of 4

About Chris Serio

Chris is an electrical engineer and commercial pilot who got roped into software development by Ben because misery loves company.

28 comments on “Screencast: Creating ATC Airport Flows in WorldEditor v1.2

  1. Very usefull information! I correct some flows that I have tried, but one doubt, the actual version of X-plane considers the type of plane??, cause I´m trying here do the lighter planes take-off on a shorter runway, but all, independently of type, take-off on the same runway.

    1. Not sure if it will help but remember the logic is ‘or’ meaning that if any condition is true the flow is applied.

    2. Hi,

      I’ve seen the same sort of issue. Regardless of the type of traffic I set (props), the airport I’ve designed is populated with turbojets and other heavy metals. I wonder if I skipped some needed step. Would it be worth opening a bug in the tracker?

      1. Flows do not determine which type of AI aircraft appear at the airports, they determine which types of traffic are PREFERRED on which runways.

        1. The airport that I´m working have 2 runways, I had made the shorter to the lighter planes (props, helicopters, turbo-prop) and the other only for heavy-jets and jets. But all planes take-off on the longest runway. This distinction by plane type is already working or maybe a bug or an error in my scenery?

          1. It’s working on the sim side. It’s likely you have a bug. Check your flow conditions and be sure your conditions are correct. I’ll turn on better sim debugging in a future version so authors can know what “flow” the sim has chosen as the active one.

  2. Very interesting and useful. I’ve just created my flows and atc routes from your previous screencasts for my fictional airport that will soon be ready. I have yet to test this in X-Plane.

  3. Great tutorial, thanks.
    Is it right that there is no way to “close” an airport for certain types of aircraft or certain conditions via ATC flows? XP will always auto-generate a flow for every aircraft and every wind condition if custom flows fail?
    Wouldn’t ATC flows be a good tool to have specific (e.g. plausible and realistic) traffic for airports and weather condition?


    1. You’re correct, flows do not have the power to “close” an airport. X-Plane currently has no notion of what it means for an airport to be closed nor would the ATC or AI aircraft know what to do in such a case.

    1. I’m ashamed to admit that flows were ready to go in 10.00…and they’ve been running at KSEA since then as well. It’s just taken me this long to have the time to make a screencast to talk about them…and they required WED 1.2 to create them which took a little while to go beta as well. 🙁

  4. From a ATCS point-of-view, everybody gets assigned the “primary” departure runway. I’ll see an SR-22 in the que behind a B777-200. Pilot’s of smaller aircraft will request a different runway, if avaliable, to avoid being delayed.

    Usually, if multiple departure runways are in use, departures will be segregated to provide the most expeditious departure flow towards the direction of the destination airport. This is to avoid departures crossing over each other.

  5. Nice tutorial, but I have some problems.
    At LZIB are 2 crossing runways 13/31 and 04/22.
    Departure runways are 04, 13 and 31.
    Arrival runways are only 22 and 31.
    For example:
    When there is a wind-rule for the rwy 13, AI departs from rwy 13, but AI doesn’t arrive to rwy 22, still arrives to rwy 13 only.
    How can I restrict arrivals on runways 13 and 04 ?
    Simply, I can’t make multi-runways flow 🙁
    Where I do mistake ?

    P.S. Sorry for my bad english.

    1. Hi Peter, I can’t debug your flow in this forum. Double check everything carefully, make sure the weather/time are set the way they are supposed to be in the sim, make sure there are no AI planes at the time so ATC can change flows immediately (usually takes a full minute) and then retest. If you think you really found a bug, please file a bug report and include your apt.dat.

  6. Chris,
    I think I’ve spotted a minor flaw in the 3rd of 4 films, and I’m only raising this so I can confirm whether I’ve understood or not. Also, it is late here and I’m tired … so if I’ve misunderstood please forgive me.
    In the example there is a “North IFR flow” created, which according to the objectives does not have a time rule. But in the example a Wind Rule was added.
    Does this not mean there is a missing “catch-all” flow for southerly winds in IFR conditions? And to fix this, would we just remove that wind-rule?

    While I’m here, I would also like to know where one might find what the actual rules are for a given airport. I’ve used airport charts to create the taxi-networks (based on your previous series of tutorials), but is there a similar reference for these Flows? Or do we use “common sense” (which may be difficult for people like me with no real world aviation background)?.

    1. Hmm I think you’re correct. I got caught up with the fact that the runways were “north” runways and instinctively added the north wind rule. With that rule removed, it should behave as expected.

      As far as where to find the actual rules, many people have scrounged up that kind of data by visiting towers, talking with controllers, observing traffic over time, listening to the ATIS over time etc. There are a lot of VATSIM groups that have gathered this data already. When I used to do ATC at Boston on VATSIM, we had a table that was the inspiration for this feature.

      1. You can browse the websites of most vARTCC’s on VATSIM and pick up a copy of their SOPs. Most (at least those in the US) have already explored the avenues Chris mentioned above and model their flows to match real life.

        Chris, any insight behind the design decision to use maximum wind speed as opposed to a minimum or range? Most documents I’ve seen concerning airport flow design use minimums (eg, >15) to decide flow.

        1. Flows should be thought of by preference according to airport efficiency. Controllers want the most efficient flow to be first in line to be selected and only if those conditions aren’t met does the next flow get considered. When there are clear skies and calm winds, ATC can choose their most efficient flow. When the visibility comes DOWN, or the ceiling comes DOWN or the wind speed goes UP, the next flow in order may need to be considered. It’s for these reasons we chose the types of comparisons that we did.

  7. To all the developers in the U.S. you can go to //www.fly.faa.gov/ois. Then select East or West Directory. Then select the underlying ARTCC and you will find the major airports listed. Under each airport you will find all the possible runway (arrival & departure) configurations from VMC (VFR) to LOW IMC (Hard IFR). O’hare (KORD) is listed under West Directory / ZAU / ORD, and there you will find 15 different configurations. Yes, they really have 15 possible ways to land and depart.

  8. Hi Ben, I was wondering whether in a future update of WED, you could incorporate the “slop” thing from the ATC taxi lines into the actual taxi lines. This would make it much easier to create the taxi lines. Just a suggestion, thanks!

    1. Oh you mean the way that the tool creates single-point links when lines are _near_ each other? Please file a bug in the _scenery tools_ bug base of type feature request, project WED!

      1. Ok, will do thanks! Sorry, I didn’t know that was classified as a bug…

  9. Hi Ben,
    creating flows for smaller airports (e.g.EDAZ) need rules for gliders and grassrunways. Pariculary if they are parallel to concrete or asphalt runways. I tried to to leave all Traffic types unselected but this XP did not accept.

    What I have to do ?

    1. Hmm on one hand, I could consider other aircraft types such as gliders, but on the other hand, flow rules are created out of necessity at BIG airports that need to remain efficient considering the large volume of traffic they have to deal with. Right now I think i’m of the opinion that smaller airports don’t need and should not have flow rules.

  10. In the interest of allowing the new Flow rules to be generated and easily used with them, I would like to suggest that you consider making all of the weather settings generate a METAR for the particular Weather setting being used. Currently, it would seem that the system is built to use the easily accessed METAR data real time from the internet. This is fine but it means that one always has to operate in real actual time. Most people do not fly in real time during simulation. However the METAR data from internet sources is real time. It would probably be OK to just overlay the selected sim flight time with current METAR data… and perhaps this is the plan… which would give a semblance of the real data.
    But beyond that, in the other modes of simulation weather, I believe that METAR data should be generated consistent with the other manually or automatically selected weather modes provided with XP and that that METAR data should be displayed and available for inspection in the weather pannels — and then used as appropriate to then trigger the operation of the Airport Flow mechanism of ATC.
    This would enable a means to check out any and all of the flows using the manual weather option to build a METAR input which would drive the ATC Flow.

    1. I’m not 100% sure i know what you’re asking but there is NO requirement that people use live METARS for flows to be in effect. Any sim weather is used to activate flows. I call them “METARS” in my video out of habit, not requirement.

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