Flight Simulator X (FSX) remains one of the most enduring platforms for desktop flight simulation, beloved by virtual pilots for its depth and extensibility. At the heart of this extensibility lies the humble aircraft configuration file, or .cfg file. These text-based files act as the DNA of each aircraft, dictating everything from flight dynamics and visual appearance to system behavior and sound output. Whether you are an experienced add-on developer or a simmer looking to fine-tune your favorite aircraft, understanding the structure and parameters of these files is essential for achieving optimal performance and realism.

In this comprehensive guide, we will break down the anatomy of FSX aircraft configuration files, explore the key sections that control performance, and provide actionable tweaks to enhance your flying experience. By the end, you will be equipped to edit these files with confidence, unlocking the full potential of your virtual hangar.

What Are FSX Aircraft Configuration Files?

Aircraft configuration files are plain-text files that store parameterized data for every flyable and AI aircraft in FSX. They are typically named aircraft.cfg and reside inside the aircraft’s main folder within the SimObjects\Airplanes directory of your FSX installation. In addition to aircraft.cfg, you may encounter model.cfg, panel.cfg, and sound.cfg files that handle specific sub‑systems, but the primary file controlling flight behavior and overall setup remains aircraft.cfg.

Every section of the file is enclosed in square brackets (e.g., [General]) and contains key-value pairs that define parameters. The file is parsed by the FSX simulation engine at aircraft load time, so even small changes can have dramatic effects on how the aircraft behaves. This makes it a powerful tool for customization, but also a source of frustration if edits are made carelessly.

Where to Find Configuration Files

The default location for FSX aircraft is:

  • %ProgramFiles(x86)%\Microsoft Games\Microsoft Flight Simulator X\SimObjects\Airplanes

Each subfolder inside Airplanes corresponds to an aircraft. Within that folder, look for aircraft.cfg. For add-on aircraft, the folder may be in a different location if installed via a third-party manager. Always note the exact path before editing.

Backup Before You Edit

Before making any changes, create a backup of the original aircraft.cfg file. This simple precaution allows you to revert to the stock configuration if a tweak breaks the aircraft’s behavior. Additionally, use a proper text editor like Notepad++ or Visual Studio Code; avoid using Word or other rich-text formats that may insert hidden characters.

Key Sections of the Configuration File

The aircraft.cfg file is divided into multiple sections, each governing a different aspect of the aircraft. We will examine the most important ones for performance and realism.

[General]

This section contains metadata about the aircraft: title, manufacturer, model, description, and simulation version. While it does not directly affect flight dynamics, it is critical for the aircraft to appear correctly in the menu and for proper identification by the simulator.

  • title – Must be unique across all installed aircraft.
  • sim – Points to the simulator version (usually "Flight Simulator X").
  • panel and sound – Refer to the panel and sound configuration files.
  • visual_damage – Enables or disables visual damage effects.

If you are modifying an aircraft for better performance, ensuring the sim and panel entries are correctly linked is a prerequisite.

[Contact Points]

The [Contact Points] section defines the landing gear geometry and properties. Each contact point is a line of numbers specifying the location, compression, damping, and friction of the gear. Properly set contact points ensure stable ground handling, realistic gear compression, and prevent the aircraft from bouncing or sinking into the runway.

  • Point.0 – Usually the nose gear.
  • Point.1 and Point.2 – Main landing gear.
  • Point.3 – Tail gear (if applicable).

For performance, adjusting the static compression and damping values can reduce excessive bouncing on landing and improve takeoff rotation feel. A common tweak is to increase the compression value for the main gear by 10–20% to simulate heavier aircraft.

[Flight Dynamics]

This is the heart of the simulation: it controls how the aircraft responds to aerodynamic forces, control inputs, and environmental conditions. The section includes parameters for lift, drag, inertia, and control surface effectiveness. Key entries:

  • empty_weight and max_gross_weight – Baseline weight.
  • reference_wing_area – Wing area in square feet.
  • reference_wing_span – Wing span.
  • reference_wing_chord – Mean aerodynamic chord.
  • lift_coefficient and drag_coefficient – Directly affect climb and speed.
  • pitch_stability and roll_stability – Control how the aircraft returns to level flight.

To improve performance (e.g., increase climb rate or top speed), you can carefully adjust lift and drag coefficients. However, be cautious: small changes can lead to unrealistic behavior. Many simmers prefer to increase engine power via the [Engine] section rather than alter aerodynamic coefficients, as the latter can break the flight model.

[Systems]

The [Systems] section manages fuel, electrical, hydraulic, and pneumatic systems. For realism, you can enable system failures or fine-tune fuel consumption rates. The key sub‑sections include [Fuel], [Electrical], and [Hydraulic]. Each has its own set of parameters.

  • Fuel capacity – Adjust to match real-world values.
  • Fuel flow – Controls consumption per hour.
  • Battery capacity and alternator amperage – Affect electrical system reliability.

Editing these values can improve performance by making fuel usage more efficient, but for pure flying performance, focus on the [Flight Dynamics] and [Engine] sections.

[Engine]

Often considered part of the [Flight Dynamics] section in older aircraft, modern FSX add-ons place engine parameters in a dedicated [Engine] section. Here you can set maximum power, thrust, and fuel efficiency. Key parameters:

  • max_rpm – Maximum engine revolutions per minute.
  • fuel_flow_max – Maximum fuel consumption.
  • thrust_scalar – A multiplier for engine thrust. Increasing this by a small amount (e.g., 1.05) gives a noticeable performance boost without ruining the flight model.
  • engine_type – Piston, turboprop, jet, etc.

Adjusting thrust_scalar is one of the safest ways to improve climb and cruise speed. Start with a 5% increase and test before scaling further.

[Propeller] (for prop aircraft)

If you fly a propeller-driven plane, this section controls blade pitch, efficiency, and drag. The propeller_efficiency parameter can be increased to improve fuel economy and speed at altitude. Similarly, adjusting the fixed_pitch or variable_pitch settings can change how the engine responds during takeoff and climb.

[Weight and Balance]

This section defines the center of gravity (CG) limits and empty CG position. A well-calibrated CG improves stability. For better handling, you can move the CG slightly forward (increase stability) or aft (increase maneuverability). The CG is expressed as a percentage of mean aerodynamic chord (%MAC). Typical values range from 20% to 35%. A forward CG (lower %) makes the aircraft more stable but reduces elevator authority.

[Models]

The [Models] section links the external visual model (3D mesh) and interior cockpit. It does not affect flight performance but is essential for visual consistency. If you install (or remove) an add-on model, ensure the [Models] entries point to the correct .mdl files. Corrupted model references can cause the aircraft to fail to load.

Step-by-Step Performance Tweaks

Now that we have covered the major sections, let us explore concrete edits that can enhance performance while maintaining realism.

1. Increase Engine Thrust (Safely)

Open the [Engine] section and locate thrust_scalar. If it does not exist, add it:

thrust_scalar = 1.05

Raising this value by 5–10% will increase engine power. Test the aircraft in a variety of conditions (takeoff, climb, cruise). Avoid exceeding 1.15 unless you are comfortable with an unrealistic power increase.

2. Improve Climb Rate

In [Flight Dynamics], adjust lift_coefficient or induced_drag_coefficient. A more reliable method is to increase max_rpm or fuel_flow_max in the [Engine] section. Alternatively, reduce drag by lowering drag_coefficient slightly (e.g., from 0.035 to 0.033). Remember to note the original value.

3. Reduce Bouncing on Landing

In [Contact Points], locate the lines for Main Gear (typically Point.1 and Point.2). The third and fourth numbers represent compression and damping. Increase the compression value by 0.05–0.10 and the damping by a similar amount. For example, change:

Point.1 = 1, 25.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0

to something like:

Point.1 = 1, 25.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.03

(The exact position of parameters varies; consult the SDK documentation for your specific aircraft.)

4. Adjust Fuel Efficiency

In the [Fuel] subsection (often inside [Systems]), modify fuel_flow_gain or fuel_consumption_scalar. Lower values mean less fuel burn, extending range. Be careful not to set values below 0.7, or the aircraft may appear to have unrealistic endurance. A realistic range is 0.85–1.00.

5. Fine-Tune the Autopilot

Some aircraft.cfg files include an [Autopilot] section. Parameters like max_bank, max_pitch, and turn_rate affect how the autopilot handles the aircraft. Increasing the bank limit from 25 to 30 degrees can make enroute turns smoother. Additionally, adjust default_pitch_mode to a constant speed or vertical speed based on your flying style.

Common Pitfalls and How to Avoid Them

  • Over-editing – Making too many changes at once can make it impossible to diagnose problems. Change one parameter at a time and test.
  • Mismatched values – For instance, increasing engine power without adjusting fuel flow can lead to unrealistic fuel consumption or overheating (if the aircraft uses a temperature model).
  • Incorrect syntax – A missing comma, extra space, or wrong line order can cause the aircraft not to load. Always validate your edits against a known working file.
  • Forgetting to save – Ensure the file is saved as plain text with the .cfg extension. Some text editors may add a hidden .txt extension if you are not careful.

Resources for Further Learning

To deepen your understanding of FSX configuration files, consult these authoritative sources:

Conclusion

FSX aircraft configuration files are the gateway to a truly personalized simulation experience. By understanding the roles of each section—from the fundamental [General] to the performance-critical [Flight Dynamics] and [Engine]—you can make informed adjustments that improve stability, climb rate, fuel efficiency, and overall handling. The key is to approach edits methodically: back up your files, change one parameter at a time, and test thoroughly before making further modifications.

Whether you are aiming for a more realistic flight model or simply want to squeeze a bit more speed out of your favorite aircraft, the power is literally in your hands—or rather, in a text file. Take the time to explore, experiment, and learn from the vast community resources available. With careful tweaks, you can transform even the default FSX aircraft into finely tuned machines that perform exactly as you wish.

Happy flying—and may your edits always keep you in the air!