Learn what the Prepar3D flight model controls, which aircraft.cfg and .air values to edit, how to test changes and why some add-ons ignore them.
Prepar3D’s flight model is the aircraft-specific aerodynamic, mass, control and propulsion data interpreted by the simulator’s flight-dynamics engine. You adjust it mainly in the aircraft’s aircraft.cfg and associated .air file; control sensitivity changes input response, not the underlying aerodynamics. Back up both files before editing.
How does the Prepar3D flight model work?
Prepar3D calculates forces and moments from the aircraft’s configuration, aerodynamic tables, loading, control positions, propulsion and atmospheric conditions. The simulator supplies the flight-dynamics engine, while each aircraft supplies the data that makes a glider, airliner or fighter behave differently. Our explanation of how a flight-dynamics engine turns aircraft data into motion covers that distinction in more detail.
The visible 3D model does not automatically determine lift, drag or stability. In a [fltsim.x] entry, model= selects the visual-model folder, while sim= identifies the associated .air file. Editing the visual mesh alone will not change the flight characteristics.
Prepar3D also does not use the MSFS 2020/2024 flight_model.cfg format. Values copied from that file will not create a Prepar3D flight model.
Do realism and sensitivity settings change the flight model?
Realism options and controller settings can change how the aircraft feels, but they do not rewrite its aerodynamic data. If only the yoke, joystick, pedals or throttle feel too abrupt, start with our Prepar3D sensitivity and null-zone setup before modifying the aircraft.
Which files control a Prepar3D aircraft?
The main files are aircraft.cfg and the binary .air file inside the active aircraft package. Traditional installations commonly place aircraft below SimObjects\Airplanes, but add-on packages can reside elsewhere and be registered through an add-on.xml file. Our guide to locating and installing Prepar3D aircraft packages explains the usual layouts.
| Problem to correct | Where to look | What it controls |
|---|---|---|
| Incorrect weight or centre of gravity | [WEIGHT_AND_BALANCE] in aircraft.cfg | Empty weight, maximum weight, datum, CG and moments of inertia |
| Generally weak or excessive controls | [flight_tuning] | Broad effectiveness and stability scalars |
| Wrong geometry | [airplane_geometry] | Wing and tail dimensions, incidence and related geometry |
| Incorrect lift, drag, stall or pitching behaviour | The .air file | Aerodynamic coefficients and curves across angle of attack, speed and other conditions |
| Incorrect engine or propeller performance | Engine and propeller sections, plus applicable .air data | Power, thrust, fuel flow and propeller behaviour |
| Ground handling or gear position | [contact_points] | Wheel locations, suspension and ground contact rather than airborne aerodynamics |
The [flight_tuning] section is useful for restrained, broad corrections. Entries such as elevator_effectiveness, pitch_stability, parasite_drag_scalar and induced_drag_scalar modify underlying behaviour; they are not substitutes for accurate geometry and aerodynamic tables.
How do you adjust the Prepar3D flight model safely?
- Back up the complete aircraft package. Preserve the original
aircraft.cfgand.airfile together. An installer or content update may restore them later, so keep your working copy separately. - Confirm which package Prepar3D is loading. Check the aircraft’s active path and the
sim=entry. Duplicate installations are common, particularly when an add-on package exists alongside an older copy underSimObjects. - Identify the type of flight model. Default and conventional aircraft normally use the stock configuration and AIR data. Some advanced add-ons calculate part of their aerodynamics or engine behaviour in a gauge or external module; their manuals or supplied configuration tools should take precedence.
- Create a repeatable baseline. Use fixed weather, a known fuel load, a recorded CG and the same aircraft configuration. Measure the original stall, climb, cruise, trim and glide behaviour before changing anything.
- Correct physical data first. Enter verified weight, CG, geometry and engine values using the units required by the Prepar3D SDK documentation for your installed version. Do not falsify wing area or aircraft mass merely to force one performance figure to match.
- Choose the narrowest effective adjustment. Use small
[flight_tuning]changes for broad control or stability corrections. Edit the.airtables when a problem occurs only within part of the envelope, such as lift near the stall or drag at high Mach. The downloadable practical FSX/P3D-era flight-dynamics tutorial provides useful background, although the SDK documentation matching your Prepar3D version remains the authority for supported records and units. - Change one variable and reload the aircraft. Use a full aircraft reload or restart Prepar3D so the files are read again. Retest the same points before making another adjustment.
aircraft.cfg is plain text, but an .air file is binary and needs a compatible AIR-file editor. Use decimal points rather than locale-specific decimal commas, preserve section and key syntax, and never assume that two similarly named parameters use the same units.
Why do flight-model edits sometimes have no effect?
Edits usually appear ineffective because Prepar3D is reading another file, the aircraft uses custom flight dynamics, or the simulator has not reloaded the package.
- Wrong aircraft copy: an
add-on.xmlpackage may override the copy edited underSimObjects. - Wrong file reference: changing
model=affects the visual model; inspectsim=for the active AIR-file name. - External calculations: a custom module may override stock engine, control or aerodynamic values.
- No reload: changing a file while the aircraft remains active may leave the previous data in memory.
- Invalid syntax or units: malformed lines can be ignored or prevent the aircraft from loading correctly.
- Installer restoration: repairing or updating an add-on can replace modified files with the supplied originals.
How can you tell whether the adjusted model is accurate?
A credible adjustment must match more than one headline figure. Compare against a reliable aircraft handbook at the specified weight, CG, configuration, altitude and atmospheric conditions.
- Check stall speed in each documented flap and gear configuration.
- Compare climb rate at the stated power setting, speed, weight and altitude.
- Match cruise using the correct speed type—IAS, CAS, TAS or Mach—and the documented power setting.
- Test trim, static stability and control authority without relying on the autopilot.
- Verify glide or descent performance, take-off behaviour and landing configuration.
- Repeat tests near the edges of the operating envelope; a scalar that fixes cruise may damage the stall or high-speed response.
The best Prepar3D flight-model adjustment is therefore the smallest change that corrects a measured error without creating another one elsewhere in the envelope.