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How to make a flatten using ADE?

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I have scenery for Astana airport (UACC). The AFCAD needs some work and it needs a flatten (parts of the main apron has default textures bleeding through the scenery). I am working on the parking and adding the missing taxiways, but I do not know how to make a flatten file. Can someone explain to me how to make a flatten file using ADE?


If anyone is interested the scenery can be found at and the file name is The description says the scenery is a alpha-beta version, but the scenery is decent.

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I use FlattEx by Mario Corallo, which also does excludes, over areas much larger than airport boundaries if needed.

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Or FSTflatten. It allows to flatten areas almost "surgically" with "multigons", not just rectangles as FlattEx does.

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Making flattens in ADE is simple. The instructions are much more complicated than the actual work:


As Hannah Glasse might have said, first open your airport. You'll need to be running ADE version 1.65 or thereabouts: I don't think earlier versions would do flattens for FS9.


Next, find out what elevation it's been given by the creator:


Click on the File dropdown menu




Click on 'Airport Properties'




The airport elevation is shown in the Properties window as 1165 feet


I suppose you want to flatten the terrain just a little bit higher so that the scenery sits on top of the airport file (AFD) stuff. I'm not sure that it will work. It may be better to give the AFD  a new elevation. Give the flatten a go and we'll carry on from what you find.


I suggest that six inches is probably as high as you'll want to go. The problem is that AI will still roll along at the airport elevation rather than sitting on top of the scenery so too much extra elevation will leave their wheels buried.


Half a foot then...


Here is a button called 'Add Polygon'




Click on it.


Then single left-click each corner in the flatten you want to create.


Here's one that's half done.




The polygon doesn't have to be a rectangle. It doesn't have to be any particular size either but it's always best to slew around in FS9 and follow the general topography of the local area - you don't want to put a load of bizarre cliffs in place. Don't cut across or surround any water either. Water has it's own elevation and won't comply with your flatten; you'll end up with sink-holes or levees.


Double-click your final corner. ADE will complete the polygon for you and open a simple dialogue box in which you can specify the flatten's elevation. The default is the Airport Properties elevation. Make the terrain six inches higher:




... and there's the flatten.




I suppose you know how to compile the modified airport. but before you do, I suggest clearing up the errors in the original. There are a lot of orphan parking spots. AI won't use them, or will just sit on them and occasionally vanish, so you might want to connect them to the rest of the taxiways before compiling.


Use the Fault Finder in the Tools dropdown menu.




It's also worth saving the airport. If you exit without saving as an ADE project you won't be able to edit the flatten later (like when you find it doesn't fit).




Now compile




Now you can exit. You'll have three new files now, named something like: UACC.ad4, UACC.bgl and UACC_TER.bgl. The ad4 is the project, the plain bgl is the afd and the TER.bgl is the flatten. I suppose the best place for the flatten is in a layer below (bigger number) than the airport's  scenery layer.


Let us know how you get on.

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What interested me in all of this was HOW default textures are bleeding through? Default FS9 airports are all built on one elevation, they do not have hills in them. A new version of an airport for FS9 is also on one level, and over-rides the default version even if the elevation is the same; it is EXPECTED that the new airport will have the same elevation. So presumably the new part that is suffering from bleed-through is outside the perimeter of the default airport flatten? And it is terrain textures that are showing, not the default airport textures? But still, there should be no need to set the new airport flattened area at a level 6 inches above the default, the new will surely over-ride the old?

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Dave Morgan, that you for the detailed explanation. I made the flatten and it came out good.

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