• Which the release of FS2020 we see an explosition of activity on the forun and of course we are very happy to see this. But having all questions about FS2020 in one forum becomes a bit messy. So therefore we would like to ask you all to use the following guidelines when posting your questions:

    • Tag FS2020 specific questions with the MSFS2020 tag.
    • Questions about making 3D assets can be posted in the 3D asset design forum. Either post them in the subforum of the modelling tool you use or in the general forum if they are general.
    • Questions about aircraft design can be posted in the Aircraft design forum
    • Questions about airport design can be posted in the FS2020 airport design forum. Once airport development tools have been updated for FS2020 you can post tool speciifc questions in the subforums of those tools as well of course.
    • Questions about terrain design can be posted in the FS2020 terrain design forum.
    • Questions about SimConnect can be posted in the SimConnect forum.

    Any other question that is not specific to an aspect of development or tool can be posted in the General chat forum.

    By following these guidelines we make sure that the forums remain easy to read for everybody and also that the right people can find your post to answer it.

P3D v4 Altitude / crash issue for island

I made an island with SBuilderX. On that island I have an airport made with ADE. Visually everything looks ok.

I can start at the airport (OWL1) and change between slew and flight mode without issue when sitting on the runway.

But as soon as I slew away from the runway/taxiway and go back to flight mode, the aircraft either sinks and crashes (with crash detection on) or takes off (with crash detection off).

Obviously the ground is not hardened where it is supposed to be. But I cannot find what error I made. I attach the source and compiled files. In the meantime while trying to find the reason for this I have reduced the island and airport altitude to sea level.

Any help is very much appreciated!


  • OWL-Island.zip
    175.7 KB · Views: 30
Hi Martin,

I think you need to create a hole in your water poly to allow the landclass to show.
I did that, George. And I think it is looking through as you would expect it. But the ground is not hard.


And yes I know the shape of the island looks like a roadkill - it is not final :)
IIRC you have to make a raster landclass over the island (because there probably isn't any there if it's water by default in the sim).

Last edited:
This is the instructions I have followed. I just re-did everything, but with the same results:

This is easy, I did about 25 islands yesterday evening
I do it this way:

1. draw a generous hydro polygon, make it transparent
2. draw a plain polygon of the outlines of the island, leave it opaque.
3. draw a simple exlude hydro polygon around it, adjust the transparency so you see
your island again. Stay inside the hydro poly from step 1 with it.
4. mark the opaque plain island ploygon (the whole thing, not a vertex!) with "set as
hole" and (in polygon drawing mode!!!) and assign it to the hydro poly in step 1. Be
sure to get the right one in a complex setup. Now, if you work with satellite-
backgrounds, you should see the background from the sat-image through the "hole".
Then you did it right. In FSX you will see whatever landclass is defined for that patch
of land showing through the hole. Remember, there is always land under the water
polys. Of course you also can set another landclass poly with the exact circumference
of the hole on the island, or rework the landclass underneath with the LC-tool, etc

1. clear, I think I cannot do anything wrong here
2. also clear, made it very simple this time
3. also clear: outside island, inside first poly
4. if I do someting wrong, then here. I draw a rectangle around the island shape so that it is completely marked. Then I rightclick it and select "set as hole". I switch over to the polygon drawing mode and select the first created water poly.

Everything looks okay, but I am still falling through when slewing off the runway. In my initial trials (see above and attachment) I have added varions polygons around the airport: flatten, airport background, landclass, but none prevented the issue.

So where do I do things wrong? I feel stupid as hell.....
Drop this into your scenery folder and you'll see that you can now land on your island.


  • LC_4912.bgl
    458 bytes · Views: 26
Yes, that works fine. But, you should remove the duplicates from the original cvx file.
Last edited:
Indeed - and many thanks!! Can you please tell me how you created this file? Is this something I missed in Sbuilder? Or something completely different?