Edit aircraft weight and balance in FS2004 safely via Fuel and Payload or aircraft.cfg, with correct units, CG checks and common fixes.
In FS2004 (FS9), use Aircraft > Fuel and Payload to change loading for the current flight. To alter permanent empty weight, centre of gravity or payload stations, back up the aircraft's aircraft.cfg, edit its [WEIGHT_AND_BALANCE] section, save it as plain text, then reload the aircraft and verify the limits.
How do I change weight and balance for one flight?
The Fuel and Payload dialog is the safest choice when you only want to load passengers, baggage, cargo or fuel for a particular flight.
- Load the aircraft and place it on the ground.
- Open the menu bar with the Alt key if it is hidden, then select Aircraft > Fuel and Payload.
- Adjust the payload stations rather than changing the aircraft's empty weight. The available station names come from its configuration file.
- Set the fuel quantity separately. Fuel has its own weight and tank position, so it also moves the centre of gravity.
- Check gross weight and CG before accepting the changes. If the CG is outside its permitted range, redistribute the load instead of merely reducing the total weight.
Changes made through this dialog affect the loaded flight; they do not rewrite aircraft.cfg. Some complex add-ons use a custom loading gauge which may override the standard FS2004 dialog.
How do I make permanent weight and balance changes?
Permanent defaults are stored in the aircraft's aircraft.cfg, normally inside its folder under the FS2004 Aircraft directory. All repaints represented by [fltsim.x] entries in that file normally share the same weight and balance data.
- Identify the active aircraft folder. Similar add-ons sometimes have several folders or separate passenger and cargo variants.
- Back up
aircraft.cfg. Keep an untouched copy outside the aircraft folder or give it a recognisable backup extension. - Open the file in a plain-text editor. Find the
[WEIGHT_AND_BALANCE]section. - Edit only documented values. FS2004 configuration weights are in pounds and position coordinates are in feet, regardless of regional display settings.
- Preserve the syntax. Use decimal points, retain the section heading and make sure numbered payload stations remain valid.
- Save it as plain text. Confirm that Windows has not renamed it
aircraft.cfg.txt. If FS2004 is installed in a protected system folder, administrator permission may be required. - Reload the aircraft. Select a different aircraft and then select the edited one again; restart FS2004 if it continues to use cached data.
Which aircraft.cfg entries control weight and balance?
| Entry | What it controls | Main caution |
|---|---|---|
max_gross_weight | Maximum permitted total aircraft weight in pounds | Raising it does not create extra lift, thrust or structural capability. |
empty_weight | Configured empty aircraft weight in pounds | Check whether the developer already included crew or operating equipment. |
reference_datum_position | Location of the datum used for CG and loading coordinates | Changing the datum without recalculating every associated position invalidates the arms. |
empty_weight_CG_position | Empty-aircraft CG coordinates relative to the datum | These are distances in feet, not a percentage of mean aerodynamic chord. |
max_number_of_stations | Number of payload stations available to FS2004 | It must cover the numbered station_load.n entries. |
station_load.n | Default station weight, position and usually its label | Do not move a station merely to force the CG into range unless its physical location is wrong. |
A station entry follows the general format station_load.0 = weight, longitudinal, lateral, vertical, label. In the normal FS aircraft coordinate convention, positive longitudinal values are forward, positive lateral values are to the right and positive vertical values are upward. Existing add-on documentation should take precedence if it defines a different reference method.
Files may also contain empty_weight_pitch_MOI, empty_weight_roll_MOI and related values. These describe rotational inertia, not ordinary payload placement, and should not be altered just to correct a loading warning.
How do I choose the correct CG and station values?
Use the aircraft's operating handbook, type data or the add-on developer's documentation, then convert every position to the datum used by that particular model. A distance measured from the nose cannot be entered directly if the configured datum is elsewhere.
The basic longitudinal calculation is CG arm = sum of (weight × arm) ÷ total weight. Empty weight, every payload station and fuel must be included. Our explanation of calculating aircraft moments and CG covers the underlying method without tying it to one simulator.
If the source gives CG as a percentage of mean aerodynamic chord, you need the position of the leading edge of that chord and its length relative to the FS2004 datum. Do not enter the percentage directly into empty_weight_CG_position, which expects feet.
Passenger and cargo versions may legitimately require different empty weights, stations and CG positions. A useful real-world FS2004 example is the Boeing 727 package containing separate passenger and freighter weight configurations; inspect such files as examples rather than copying their figures into another aircraft.
Where is fuel weight and position configured?
Fuel quantities and tank positions belong in the [fuel] section, not in [WEIGHT_AND_BALANCE]. Change the fuel percentage through the simulator for normal flight planning; edit tank capacities or coordinates only when correcting inaccurate aircraft data.
A tank farther ahead or behind the CG can shift balance substantially as fuel is used. The practical effects are explained in our guide to fuel load, burn and centre-of-gravity movement.
Why are my FS2004 weight and balance changes not working?
- The values revert: you edited a duplicate or inactive aircraft folder, changed only the in-simulator loading, or an add-on loading gauge restored its own defaults.
- Payload stations are missing: check
max_number_of_stations, station numbering and the syntax of everystation_load.nline. - The CG moves in the wrong direction: the longitudinal sign or datum has been misunderstood. Compare the pilot, baggage and fuel positions already present in the file.
- The aircraft is much too heavy: kilograms may have been entered where FS2004 expects pounds, or crew weight may exist in both
empty_weightand a payload station. - FS2004 rejects or omits the aircraft: restore the backup and check for a damaged section heading, missing value, invalid character or incorrectly saved filename.
- The loading warning remains after raising maximum gross weight: total weight may now be under the edited limit while the CG is still outside its envelope. Gross weight and balance are separate checks.
After editing, test an empty configuration, a typical operating load and the heaviest authorised load. Verify the displayed total weight and CG each time, then check that take-off trim, rotation and pitch response remain credible. If the only goal is carrying more payload, changing a limit in aircraft.cfg is not a substitute for accurate performance data.