Sometimes it is necessary to change the altitude of an airport.  It could be that you have installed a custom mesh and the airport is no longer flat to the ground.   This is not as simple as changing the altitude of the airport in the properties dialog.  ADE does not allow this to be changed since it has no useful effect on its own.  While in most cases FS honors the last file loaded in the case of airport properties it honors the first.  So if we want FS to accept our altitude change then we have to create a special Bgl file that loads before the stock airport.  Generally we put these in World Scenery since we know that will load before any stock airport files.

Load the airport that you want to revise the altitude for.  This is KHUT

The stock altitude for this airport is a little over 470m.  We are going to change this to 450m.

It is not enough to change the reference altitude of the airport.  There are a number of other parts of the airport that have an altitude that could be set differently than the airport reference altitude.  Generally we don't want this.  Below are two examples - Runways and Starts.  Both are currently at the airport reference altitude.  If we changed the airport reference altitude but not the runways and starts then, in the case of this tutorial, the airport would end up at 450m while the runways and starts would be 20m higher.  Other elements like aprons and taxiways have no altitude property and automatically stick with the airport reference altitude.

This is a simple dialog that just has one thing to change - the altitude.

1. Here we just change the value to 450m
2. To proceed  click the Change button.  If you change your mind now use Cancel to get back to the airport display.

If the airport is not stock - that is an airport created by the user that has an Ident not in the stock list - then ADE now offers the option of creating a stub.  By default this is turned off since it is not required.  However for some advanced users who may have several Bgl files related to their airport then having a Bgl file that they know will load before anything else may be of benefit.

This notice will appear when you select the Change Button.  It is warning you that the change will not affect background polys or  terrain flattens.  These can be complex and in some cases involve slopes.  We feel that you will know what and why the background polys and flattens are set the way they are and it is too risky to let ADE decide to change them.

If you want to complete altitude change then click OK.  If you are not sure or want to check any terrain elements first then click Cancel.

We will now check the altitude properties for the airport, the runway and the start.  This confirms that ADE has now changed everything that needs changing (other than terrain elements as mentioned above)

ADE changes the description in the Title bar when an airport has a revised altitude.  This is a reminder that this airport will not be set at the stock airport in sim.

To get FS to recognize and act on the revised altitude you need to compile the airport.  In addition to the standard Bgl file(s) created for the airport a special one will be created and placed in the World Scenery Folder.  This is sometimes call a 'stub' or 'pre-load' Bgl file.

1. Open the ..\Scenery\World\Scenery folder
2. The pre-load Bgl file is present and has _ALT in the name to indicate that this is changing the altitude of KHUT.

That completes the task of changing the altitude for this airport and concludes the tutorial