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Revision as of 13:28, 6 April 2016 by Rominet (talk | contribs) (Use “navdata cache” instead of “NavDB cache” for consistency (“Navdata cache” being the canonical name of the corresponding page on the wiki))
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Screen shot showing typical structure $FG_HOME

$FG_HOME is an environment variable indicating the main location where user-specific FlightGear data is stored (not application data). $FG_HOME is a notable place were FlightGear data is written to, contrary to $FG_ROOT, which is generally read-only.

$FG_HOME is normally used to refer to the operating system specific location for some settings/folders. Its default value is determined by the fgfs binary during startup and is a directory that varies with the operating system supported by FG (Windows, OS X and Linux). It is highly recommended to rely on the default value (i.e., not setting $FG_HOME yourself in any way), unless you Really Know What You Are Doing™.

Note  The /sim/fg-home property should be considered read-only, for similar reasons why $FG_HOME shouldn't be explicitly set by users.
Note  FlightGear reads the Fgfsrc config file from $FG_HOME if it exists (fgfsrc without any leading dot), in addition to .fgfsrc from $HOME (with a leading dot in this case).


In $FG_HOME is information stored between sessions. That information is for example configuration/preferences, properties marked with the user-archive attribute and aircraft-specific settings (using the data helper class in aircraft.nas). $FG_HOME is also the location for the SQLite-based navdata cache.

Common paths

You can determine the location of your $FG_HOME by using the property browser and checking the value of /sim/fg-home, but the usual paths are shown below.

You can also use the Nasal Console to print out $FG_HOME:

var path = getprop("/sim/fg-home");
print("Your $FG_HOME is at: ", path);

The /sim/ property subtree is also the place where you can find other folders, such as fg-root, fg-scenery and the current working directory (fg-current).



Mac OS X

~/Library/Application Support/FlightGear (to learn more about viewing hidden folders, see [1])

As all future FlightGear versions will take their preferences from here, it is a good idea to have their access available easily.

Desktop/Finder/Go/Go to Folder is where you need to start.

When given the option, input: ~/Library/Application Support/FlightGear

It is probably a good idea to have ~/Library/Application Support/FlightGear saved on a Stickies note just in case you forget it.

If you want/need to refer to any of these files frequently, you could make an alias of a file, or the whole folder, and place it somewhere easier to access. TerraSync data is stored in $FG_HOME/TerraSync in the default configuration, see TerraSync for details.


FlightGear 3.0 and later


%HOME% is usually C:\Users\User name

Before FlightGear 3.0


%APPDATA% is another environment variable that depends on your Windows version. On XP and older, it can be found under C:\Documents and Settings\User name\Application Data. On Vista and later it can be found under C:\Users\User name\AppData\Roaming. The folder is hidden by default. See these instructions to show the folder.

Use in troubleshooting

As one user once said, "When in doubt delete $FG_HOME". Many problems, including corrupted databases, broken TerraSync and many others can be fixed by deleting fgfs_0.txt, fgfs.txt, terrasync_cache, and the navdata cache.

When you encounter problems, try deleting the files, but always keep the fgfs.log and fgfs_0.log log files to help in troubleshooting.

Related content

Wiki articles