Realistic AI aircraft traffic at airports requires specifying multiple parameters in the WED scenery file.

The minimum requirements for successful AI traffic operation at an airport are:

  1. The airport is of type “airport”, i.e. not a “seaport” or “heliport.”
  2. The “Has ATC” property is checked in the metadata.
  3. Have at least one ATC frequency of type “Tower” defined.
    • Note this refers to the “Type” property, not the name given to the frequency entry, which has no relevance for AI operation.
  4. At least one (very preferably multiple) ramp starts of sufficient size is specified:
    • The size of the largest ramp start (of any type) must be larger or equal to the actual AI aircraft attempting to spawn/land.
    • X-Plane will not check if that ramp start is actually vacant or the right type – it rather gives ATC authority to make “emergency” decisions like parking a 747 on a Size A “Props” “Misc” ramp start, if none of the size F starts at that airport are available for some reason.
    • See the “Guide to Ramp Starts” for details on ramp start fields.
  5. At least one paved runway (surface = “Asphalt” or “Concrete” only) of sufficient width and length is active.
    • Active means either:
      • there is valid flow specification that meets the current weather condition and it includes a “Runway use” rule for that runway
      • or no flows are specified. In this case, X-plane will auto-generate suitable flows that activate all runways under any weather condition.
    • Sufficient width & length depends on the AI aircraft category as in the table below:

Aircraft category

Min. Rwy Width

Min. Rwy Length

Heavy

125 feet

10,000 feet

Fighters

125 feet

7,500 feet

Jets

100 feet

7,500 feet

Turboprops

75 feet

2,500 feet

Props

50 feet

2,500 feet

Anything else

25 feet

1,000 feet

These are all conditions to make AI spawn or attempt to land at the airport.

It also implies the actual ramp start types and ATC taxi network details do not prevent AI operation, but only help to make it look more “plausible” once AI are present at the airport. A working ATC Taxi network, either auto-generated by X-plane or specified in the scenery is required to have those AI successfully leave the runway and taxi to/from the ramp starts.

Troubleshooting Tips

To debug problems with AI operations it is recommended to start with hiding all user specified flows and ATC taxi networks in the WED scenery pack. X-Plane will then auto-generate these items, which will result in functional flows & networks, although they will also appear less polished.

By default, the X-Plane log.txt also includes information about AI spawning, flow selection and AI Taxi instructions. The art control atc/debug/log_spawn=1 prints log info on AI aircraft arrival & departure logic. Use the developer console to see this in-sim or view it in the log.txt

3 comments on “Guidelines for AI aircraft airport use

  1. Support Grass runways!

    Is the decision to need paved runways a technical limitation (eg AI really behaves badly on grass – big fix required) or more of a sweeping generalisation from back-in-the-day when X-Planes airports were ‘plausible’ rather than the curated beauties they are today?

    1. It’s due to a limit in the sophistication with which ATC analyzes the airport layout. Chris started digging into the ATC code again recently, and this is one I’ve had on my radar to re-evaluate at some point.

      At a minimum, I expect we will be able to allow airports with grass runways that are longer than the longest pavement if the flows are built by hand – basically if the author tells us things are okay then they’re okay. If the airport layout is autogen, that’s a lot harder, as grass tends to just be a big blobby area.

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