Install or update FlightGear navigation data safely: find FG_HOME/NavData, handle CIFP and AIRAC files, rebuild the cache and fix stale data.
To install or update navigation data in FlightGear, download a package explicitly compatible with FlightGear, close the simulator, back up the existing NavData folder, copy the package into the active FG_HOME/NavData location exactly as supplied, then restart FlightGear, rebuild its navigation cache if required, and verify a changed waypoint or procedure.
This FlightGear navdata update procedure changes the simulator’s navigation database. It does not update a saved flight, built-in tutorial flight, aircraft, charts or visual scenery.
Choose the right FlightGear navigation data update
The correct update depends on whether you need refreshed stock data, a particular AIRAC cycle or data used privately by one aircraft’s FMS.
| What you need | Use this method | Watch for |
|---|---|---|
| Refreshed data supplied with FlightGear | Update FlightGear through its normal installer or package manager | The bundled database may not match the AIRAC cycle used by your charts or online group |
| A specific AIRAC cycle | Install a complete, licensed navdata package whose supported targets explicitly include FlightGear | Navaids, fixes, airways and procedures must belong to the same cycle |
| New SIDs, STARs and approaches | Use a FlightGear package that includes compatible CIFP procedure data | An en-route package does not necessarily contain procedures |
| An updated aircraft CDU or FMS | Use the aircraft-specific target described by that aircraft or data package | Updating FlightGear’s central database may not update a private FMS database |
AIRAC means Aeronautical Information Regulation and Control. Its cycle identifier tells you when the data became effective; it does not guarantee that every package contains airport layouts, instrument procedures or worldwide coverage.
File ở đâu? Where are FlightGear navdata files stored?
For a manual per-user update, FlightGear navigation files normally belong in FG_HOME/NavData, not beside the simulator executable.
| Location | Purpose | Should you modify it? |
|---|---|---|
FG_HOME/NavData | Per-user navigation-data overrides | Yes, when the package specifies a FlightGear user installation |
FG_ROOT/Navaids | Navigation data bundled with FlightGear | Only when the package explicitly instructs you to replace stock files |
FG_ROOT/Airports | Bundled airport and runway information | Do not alter it for an ordinary navdata update |
| Aircraft-specific data folder | A private FMS or CDU database | Only according to that aircraft’s documentation |
Common FG_HOME defaults are %APPDATA%\flightgear.org on Windows, ~/Library/Application Support/FlightGear on macOS and ~/.fgfs on Linux. Sandboxed packages, portable installations and customised launch options can place it elsewhere.
Confirm the active FG_HOME and FG_ROOT in FlightGear’s start-up log rather than trusting a folder left by an older installation. Our breakdown of FG_HOME, FG_ROOT and missing-data errors explains how to identify the files FlightGear actually loaded.
Folder names are case-sensitive on some systems. A mistake we see constantly is an extra level such as FG_HOME/NavData/NavData, which leaves the files invisible to FlightGear.
FlightGear navdata update tutorial: the safe method
A clean installation keeps the complete cycle together and makes it easy to restore the previous database if parsing or procedure loading fails.
- Inspect the package before changing anything. Confirm that FlightGear is listed as a supported target and check the package’s cycle, coverage and installation notes. Packages commonly contain files such as
earth_nav.dat,earth_fix.dat,earth_awy.dat,cycle_info.txtand aCIFPfolder, but names differ between formats and releases. - Close FlightGear and its launcher. The source files and generated navigation cache should not be in use while they are replaced.
- Find the active FG_HOME. Use the path reported by the start-up log. This prevents an update being copied into an abandoned profile belonging to another FlightGear installation.
- Back up the old database. Rename or copy the existing
NavDatafolder as a complete unit. If an authorised installer manages the update itself, let it perform its own backup and clean-up. - Extract the new package with its hierarchy intact. If the archive contains a top-level
NavDatafolder, place that folder inFG_HOME. If it contains the navdata files directly, createFG_HOME/NavDataand place them there. KeepCIFPas a subfolder when supplied, and do not rename or decompress individual files unless the instructions require it. - Install one complete cycle. Do not combine a new airway file with old fixes or retain procedure files from a previous cycle. Starting with an empty new
NavDatafolder avoids stale CIFP records surviving an overlay installation. - Leave FG_ROOT alone unless instructed otherwise. A stock-replacement package may target
FG_ROOT/Navaidsor another bundled-data folder, but those files can be overwritten by a later simulator upgrade. Back up every file named by the package before replacing it. - Restart and let the navigation cache rebuild. FlightGear normally detects changed source data, and the first start can take longer while it compiles the database. If it does not rebuild, use the navigation-cache rebuild facility exposed by your FlightGear build.
- Verify more than one data type. Check a changed fix or navaid in the map or route manager, then test an airway or procedure if the package claims to include them. An established VOR appearing normally proves very little about whether the new cycle loaded.
If you are updating the whole simulator to obtain newer bundled data, follow our safe FlightGear upgrade and FG_ROOT checklist so an old data directory is not paired with a new executable.
What is CIFP, and where does it go?
CIFP means Coded Instrument Flight Procedures; it supplies machine-readable SIDs, STARs and approaches rather than the complete navigation database.
When a FlightGear package includes a CIFP directory, preserve it inside the package’s NavData structure. Do not move its airport files beside earth_nav.dat, and do not combine them with en-route files from another AIRAC cycle.
A raw CIFP distribution is not automatically a ready-to-install FlightGear update. It may have limited geographic coverage or require supporting fixes, navaids, runway records and a compatible parser. If CIFP is absent, updated navaids and airways can work while the FMS continues to show old or missing departures, arrivals and approaches.
Procedure loading can also fail when a procedure refers to a runway designation that does not match FlightGear’s airport database. That is different from a missing navaid and cannot always be fixed by rebuilding the cache.
What if it’s not labelled for FlightGear?
If a package is not documented as compatible with FlightGear, do not install it by trial and error.
FlightGear can read navigation records derived from formats also used by other simulators, but matching file names do not prove compatibility. Record versions, folder layout, compression and CIFP handling can differ. Renaming an unrelated package’s files does not convert them.
Use another simulator’s target only when the package documentation explicitly states that the exact format is accepted by your FlightGear build. If it does not, retain the bundled database or update FlightGear through its supported installation method.
What should I do if FlightGear still shows old navdata?
Stale data usually means FlightGear loaded a different profile, retained its generated cache or found an incomplete user override.
| Symptom | Likely cause | Fix |
|---|---|---|
| The map still shows the old fix or navaid | Wrong FG_HOME, nested folders or an unchanged cache | Check the loaded paths in the start-up log, correct the folder structure and rebuild the navigation cache |
| Navaids disappear after installation | Incomplete package, unsupported format or mixed cycles | Remove the new override, restore the complete backup and reinstall one compatible data set |
| The log reports parsing errors | Damaged extraction, wrong record format or altered compression | Discard the extracted copy and install a fresh, unchanged FlightGear package |
| The map updates but the aircraft CDU does not | The aircraft uses a private FMS database | Install its supported aircraft-specific target rather than repeating the central update |
| Fixes and airways update but procedures do not | Missing, stale or incompatible CIFP data | Install the matching procedure component and remove CIFP files left from older cycles |
| The update vanishes after a FlightGear upgrade | Files were written into FG_ROOT and replaced | Use a supported FG_HOME/NavData installation when the package offers one |
If automatic cache detection fails, close FlightGear and remove only the generated navigation-cache file identified by your build or its log, then restart. Do not delete the source .dat files or the whole FG_HOME directory; that directory also contains preferences, controls and other user data.
How do I roll back a failed update?
Close FlightGear, remove or rename the new NavData folder, restore the complete backup and rebuild the navigation cache.
Confirm that stock or previous-cycle data returns before trying another package. This separates a bad data set from an unrelated aircraft, scenery or simulator problem.
How can I confirm which AIRAC cycle is installed?
The most reliable cycle identifier is the package manifest or its supplied cycle_info.txt file, not the archive’s download or modification date.
Check the start-up log to confirm that FlightGear loaded the intended NavData path without parser errors. Then inspect several records known to have changed in that cycle: one fix or navaid, an airway segment and, where included, a SID, STAR or approach.
Our guide to using FlightGear’s map to inspect airports and navaids covers the quickest central-database check. If the map is correct but the cockpit unit is not, use the steps for checking waypoint and route data in FlightGear’s GPS before assuming the update failed.
Does a navdata update change scenery or tutorial flights?
No. Navigation data, visual scenery and FlightGear tutorial flights are separate types of content.
A navdata package can update navaids, fixes, airways and supported procedures without changing the visible airport. Airport and runway records may also be supplied separately from terrain, buildings and objects, so a new runway can appear in route planning while the scenery still shows the older layout.
Saved routes and tutorial scripts are not rewritten by a navdata update. They may behave differently if a referenced waypoint was renamed, moved or removed, but the original flight or tutorial file remains unchanged.