Learn how to update FlightGear navigation data, choose the right AIRAC package, rebuild the nav cache, and fix stale navaids or FMS data.
To install or update navigation data in FlightGear, use a data set explicitly packaged for your FlightGear version, close the simulator, back up the existing data, install the files in the package’s specified user or simulator data folder, then restart FlightGear and let it rebuild its navigation cache.
Choose the right FlightGear navigation data update
The correct method depends on whether you need refreshed stock data, a specific AIRAC cycle, or data for one aircraft’s flight management system.
| Requirement | Best method | Main limitation |
|---|---|---|
| Refresh FlightGear’s supplied database | Update FlightGear through its normal installer or package manager | The bundled data may not represent the latest AIRAC cycle |
| Match current charts, routes or online operations | Install an authorised AIRAC package explicitly labelled for FlightGear | The package must support your FlightGear release and required data types |
| Update only an aircraft’s CDU or FMS | Use the aircraft-specific target supplied with the data package | Updating FlightGear’s central database may not affect that aircraft |
Do not substitute an X-Plane or other simulator package merely because it contains similarly named .dat files. FlightGear’s parser, directory structure and supported record formats matter. If no FlightGear-compatible build is offered, do not attempt to convert it by renaming files.
How do I install the new nav data?
A safe installation preserves the old database, keeps every file from one cycle together and uses the active FlightGear data directories rather than a guessed installation path.
- Close FlightGear completely. Shut down both the simulator and launcher so the navigation cache and source files are not in use.
- Identify FG_HOME and FG_ROOT.
FG_HOMEcontains your user settings and cache;FG_ROOTcontains the simulator’s core data. Typical FG_HOME locations include%APPDATA%\flightgear.orgon Windows,~/Library/Application Support/FlightGearon macOS and~/.fgfson Linux. Sandboxed packages can use a different location, so confirm the active path in FlightGear’s launcher or start-up log. Our explanation of FlightGear’s data folders and missing-file errors can help if several installations are present. - Back up the existing data. Copy any existing user
NavDatadirectory and any stock files you intend to replace. Do not back up only one file from a matched cycle. - Follow the package’s FlightGear layout. A package built as a per-user override will commonly place its contents in
FG_HOME/NavData. A package intended to replace bundled data may targetFG_ROOT/Navaidsand, when airport data is supplied,FG_ROOT/Airports. Preserve the supplied folder hierarchy and avoid creating an accidentalNavData/NavDatanesting. - Keep the data set together. Navigation packages can contain navaids, fixes, airways, airports and procedures. Files may have names such as
nav.dat,fix.dat,awy.dator compressed equivalents, but names and coverage vary. Do not combine files from different AIRAC cycles or change their compression. - Restart and allow the cache to rebuild. FlightGear compiles its source data into a navigation cache. The first start after an update can take longer than usual; interrupting it may leave an incomplete cache.
- Verify the result. Search for a changed waypoint, navaid or airport in the map or route manager. Our guide to checking airports and navaids on FlightGear’s map explains the relevant map tools.
If the update’s instructions specify a different destination, follow those instructions rather than forcing the package into the folders above. Installers that offer a dedicated FlightGear profile should be allowed to create the expected directory structure.
What should I do if FlightGear still shows old data?
Old waypoints usually mean FlightGear loaded another installation, retained its compiled cache or found an older user override first.
| Symptom | Likely cause | Fix |
|---|---|---|
| The map is unchanged | Wrong FG_HOME or FG_ROOT, or the cache was not rebuilt | Check the start-up log for the paths actually loaded, then use the launcher’s navigation-cache rebuild control if your version provides one |
| Cache generation reports parsing errors | Unsupported file format, damaged archive or mixed cycles | Restore the backup and reinstall one complete FlightGear-compatible package |
| Navaids disappear after the update | The user override is incomplete or incorrectly nested | Remove the new override, confirm that stock data returns, then correct the package layout |
| The map updates but the aircraft CDU does not | The aircraft uses its own FMS database | Install the aircraft-specific data target or consult its included documentation |
| The update disappears after upgrading FlightGear | Files were written directly into FG_ROOT and replaced by the installer | Use a supported per-user NavData package where available |
If automatic cache detection fails, close FlightGear and remove only the generated navigation-cache file identified in the start-up log, then launch again. Do not delete the source .dat files or the entire FG_HOME folder; that folder also contains controls and preferences.
Does installing FlightGear scenery update navigation data?
Scenery and navigation data are separate, so installing terrain or buildings does not normally update navaids, fixes, airways or an AIRAC cycle.
Airport layouts can involve both airport database information and visual scenery, which is why a new runway may appear in the route manager but not look correct outside the cockpit. Use the separate FlightGear scenery installation instructions when the missing item is terrain, objects or visual airport content rather than navigation records.
Why does an aircraft’s FMS still show the old AIRAC cycle?
Some advanced FlightGear aircraft use a private navigation database instead of, or alongside, FlightGear’s central cache.
Check the aircraft’s documentation and the data package’s supported targets. A central update may refresh the map, route manager and standard GPS while leaving that aircraft’s CDU untouched. Procedure coverage also varies: a package containing navaids, fixes and airways does not necessarily include SIDs, STARs and approaches.
How can I confirm which AIRAC cycle is installed?
The most reliable cycle identifier is the one supplied in the package manifest, installer or FlightGear start-up log.
Confirm that the log shows the intended NavData path and no parsing errors, then check several records known to have changed in that cycle. Testing only one established VOR proves that the database loaded, but not that every component belongs to the same cycle.