How do I change FSX aircraft performance or cruise speed?

To increase an aircraft’s speed in Microsoft Flight Simulator X (FSX) or FSX: Steam Edition, back up its folder, then tune engine thrust or power and drag in aircraft.cfg in small steps. Changing cruise_speed alone only changes a reference value; actual speed depends on the flight model, weight, altitude, weather and power settings.

How do I increase aircraft speed in Flight Simulator X?

FSX has no global setting that makes every aircraft fly faster; each aircraft has its own flight model in aircraft.cfg and an associated .air file. Do not edit the separate fsx.cfg graphics and simulator-settings file for this purpose.

Choose the first adjustment according to the part of the performance envelope that is wrong:

Start with a small test adjustment. For example, thrust_scalar=1.02 requests a two per cent scalar increase, while parasite_drag_scalar=0.98 applies a two per cent reduction to that drag multiplier. Neither guarantees a two per cent speed change because thrust required rises rapidly with speed.

Do not use cruise_lift_scalar merely to chase a cruise figure. It changes lift and trim relationships and can disturb stall, approach and landing behaviour.

Do you mean aircraft speed or the FSX simulation rate?

Aircraft performance and time acceleration are different controls. If you want the whole simulation to run faster, the default FSX keyboard commands use R followed by + or - to change the simulation rate; check your control assignments if those keys have been remapped.

Editing aircraft.cfg does not change the simulation rate. High rates can also upset autopilots, traffic and complex add-on systems, so return to normal time before critical phases of flight.

Why doesn’t changing cruise_speed make the aircraft faster?

cruise_speed is a reference value, not an instruction telling FSX how much thrust to produce or drag to remove. It may be read by planning or aircraft-information functions, but physical speed still settles where available thrust equals aerodynamic drag.

The related max_indicated_speed and max_mach entries describe operating limits used by FSX or the aircraft’s instruments. Raising them does not improve acceleration or maximum level speed; it merely changes the declared limit and may conceal an unrealistic flight model.

Weight, centre of gravity, altitude, air temperature, mixture, propeller setting, engine condition and aircraft configuration all affect the result. Published cruise performance also assumes a particular power setting. Comparing a handbook’s 75 per cent-power cruise figure with an unrestricted full-throttle test is not a valid calibration.

Is TAS a folder in FSX?

There is no standard “TAS folder” in FSX. TAS means true airspeed, normally expressed as KTAS, while the panel commonly shows indicated airspeed in KIAS.

At altitude, KTAS is normally higher than KIAS for the same flight condition. Groundspeed is different again because it includes wind. When tuning an aircraft, compare KTAS with a published KTAS target at the same altitude, weight and power setting; never tune the flight model from groundspeed.

Where is aircraft.cfg in my FSX?

The active configuration file is normally inside the aircraft’s folder under <FSX>\SimObjects\Airplanes, but the FSX installation root differs between boxed installations, Steam Edition and custom library locations. Our guide covers the correct aircraft.cfg locations, backups and Windows permission fixes.

Folder names are not always the same as the name shown in Aircraft Selection. Downloaded aircraft can also exist in more than one installation, so confirm that you are editing the copy loaded by the simulator.

How do I identify my own aircraft (“ini punya saya”)?

Ini punya saya is Indonesian for “this is mine”. In an FSX context, the simulator does not mark an aircraft folder as yours; identify the selected model using its ui_manufacturer=, ui_type= and ui_variation= fields.

The sim= line in that livery’s [fltsim.x] block names the active AIR file without its .air extension. Our explanation of how liveries, [fltsim.x] entries and the sim= mapping work helps distinguish appearance records from the files that control performance.

FSX tutorial: how to edit aircraft.cfg safely

The safest method is to establish a repeatable baseline, change one valid parameter and then repeat exactly the same test.

1. Find the active aircraft folder. Match the selected manufacturer, type and variation to its [fltsim.x] entry. Check the associated sim= line rather than assuming the first AIR file in the folder is active.
2. Back up the complete folder. At minimum, preserve untouched copies of aircraft.cfg and every referenced .air file. Most performance sections apply to every livery using that model.
3. Record a baseline. Use the same fuel, payload, centre of gravity, altitude, temperature, weather, power setting and aircraft configuration. Let speed and engine indications stabilise before recording KIAS, KTAS, climb rate, fuel flow and relevant engine output.
4. Change one value. Scalar values commonly use 1.0 as their neutral setting. Begin with an adjustment of roughly two to five per cent and use a full stop as the decimal separator.
5. Save it as plain text. Retain the exact filename aircraft.cfg. A word processor or an editor that silently creates aircraft.cfg.txt will leave FSX reading the original configuration.
6. Reload the aircraft. Reselect it after saving. Close and restart FSX if the result remains unchanged, especially with a complex add-on.
7. Retest more than cruise. Check take-off distance, acceleration, climb at several altitudes, cruise, descent, glide, approach, stall behaviour, fuel flow and range. Restore the backup if the change fixes one number but damages the wider envelope.

“Those options aren’t there in my FSX” — what should I do?

Aircraft power and drag scalars are not exposed in the normal FSX settings menus; they are text entries within each aircraft’s configuration. If an expected entry is missing from aircraft.cfg, first confirm the engine type and active aircraft copy.

• Wrong engine section: piston, turboprop and jet models use different sections. A jet’s thrust_scalar does not belong in a piston-engine section.
• Omitted neutral scalar: a conventional model may omit a scalar and rely on its default behaviour. Add only a documented FSX entry, place it under the exact applicable section and avoid duplicate keys.
• AIR-file-controlled data: many detailed engine and aerodynamic curves are stored in the binary .air file rather than exposed in aircraft.cfg.
• Custom add-on logic: complex aircraft may calculate thrust, engine limits or drag through XML gauges, compiled modules or external systems. Standard scalars can have limited effects or break the add-on’s internal logic.
• Wrong installation copy: boxed FSX, Steam Edition and additional aircraft libraries can contain similarly named folders.

Can I change the code?

You can change supported values in aircraft.cfg, but it is configuration data rather than executable source code. Use a plain-text editor, retain the original section names and syntax, and keep a restorable backup.

An AIR file is binary and must not be edited in a text editor. It requires a compatible flight-dynamics editor and a clear understanding of the record or curve being changed. Renaming the extension does not convert it to text.

XML gauges may be readable, but compiled modules are not safely editable this way. If custom systems control performance, use documented configuration options where available and respect the add-on’s licence and support conditions. An add-on update, repair operation or Steam file verification can overwrite modified files.

Why is my FSX performance edit not working?

Most failed edits result from FSX reading a different file, Windows preventing the replacement or the aircraft not being reloaded.

• The edited file is not active: check the selected livery’s sim= mapping and look for duplicate aircraft folders.
• Windows blocked the save: protected installation folders may deny changes. Edit a copy in a writable location, then copy it back with the required permission.
• The extension changed: enable file-extension visibility and remove any unintended .txt suffix.
• The setting is duplicated: search the complete file for another copy of the same key or section before adding a new one.
• FSX still has the old model loaded: reselect the aircraft or restart the simulator.
• The comparison is inconsistent: a different payload, altitude, temperature, mixture or propeller setting can mask a small flight-model change.
• Custom systems override it: restore the backup rather than applying increasingly large scalars to fight an add-on’s own engine or flight-model code.

How do I know the new cruise performance is realistic?

A credible adjustment should match several published performance points without creating implausible behaviour elsewhere. We recommend matching engine output and climb first, then cruise drag, fuel consumption and low-speed handling.

Use the same airspeed type and test conditions as the source data. For a piston aircraft, set the specified manifold pressure, RPM and mixture; for a turbine aircraft, match the stated altitude, weight and engine rating. Allow the aircraft to stabilise before recording speed.

Choose a configuration scalar when the error is broadly consistent across the envelope. If the correction is needed only near one altitude, Mach number or power setting, restore the broad scalar and correct the relevant AIR-file curve instead. That avoids fixing one cruise point at the expense of climb, approach, range or engine realism.