How do I set up FSUIPC4 for FSX controls and add-ons?

For FSX and FSX: Steam Edition, install FSUIPC4—not FSUIPC6 or FSUIPC7—into the simulator’s Modules folder, approve both trust prompts, then open Add-ons > FSUIPC after loading a flight. Unregistered FSUIPC4 normally satisfies add-ons needing its data interface; assigning and calibrating controls requires registered functionality.

Which FSUIPC version works with FSX and FSX: Steam Edition?

FSX and FSX: Steam Edition require FSUIPC4, the 32-bit module made for FSX.

A higher FSUIPC number is not a universal upgrade: each branch targets a different simulator architecture. If documentation says “FSUPIC”, that is almost always a misspelling of FSUIPC; for FSX, the module file should be FSUIPC4.dll.

Is FSUIPC4 for FSX free, or do I need a registered licence (Kaufversion)?

FSUIPC4 can normally be installed without user registration when an add-on only needs its IPC data interface.

The German term Kaufversion simply means the purchased or registered functionality; it is not a different DLL. A licence for another major FSUIPC version should not be assumed to unlock FSUIPC4, and existing registration details must be entered exactly as issued.

The free download is the FSUIPC module, not a copy of FSX. Use our FSX-compatible FSUIPC package and select the FSUIPC4 material. We do not recommend obtaining FSX or an old FSUIPC archive from the Internet Archive: FSX itself is commercial software, while archived module packages may be obsolete, modified or missing their documentation.

How do I install FSUIPC4 and confirm that FSX loaded it?

Install FSUIPC4 with FSX closed and point the installer at the exact folder containing the fsx.exe you use.

1. Extract the package first. Do not run the installer from inside the compressed archive. If Windows blocks it from changing a protected FSX folder, rerun the verified installer with administrator privileges.
2. Back up an existing configuration. Copy Modules\FSUIPC4.ini and any existing licence file before updating. The INI contains assignments, calibration and profile settings.
3. Check the detected simulator path. With boxed FSX and Steam Edition installed together, confirm that the destination is the correct installation. The finished module belongs in that installation’s Modules folder, not in SimObjects, the Scenery Library or an aircraft folder.
4. Register or skip registration. Enter valid FSUIPC4 details if you have them. Otherwise leave registration blank; compatible add-ons can still use the unregistered IPC interface.
5. Approve both FSX prompts. Start FSX and allow the module and its publisher when asked. Rejecting either trust prompt can prevent FSUIPC4 from loading.
6. Load a flight and check the menu. Press Alt if the menu bar is hidden, then look for Add-ons > FSUIPC. It may not be visible while FSX is still at its opening screens.
7. Close FSX normally once. This lets FSUIPC create or update FSUIPC4.ini and its runtime log in the Modules folder.

Our complete FSUIPC4 installation checks for FSX cover installer detection, trust entries and module-loading errors in more detail.

Do not copy an entire DLL.xml file from boxed FSX to Steam Edition. Their application-data folders can differ, especially when both editions are installed, and replacing the file can disable every other DLL-based add-on listed in it.

How do I assign FSX controls through FSUIPC4?

Registered FSUIPC4 can manage axes, buttons and aircraft-specific profiles, but each physical input should have only one owner.

1. Test the hardware in Windows. Make sure every axis reaches its full range without erratic movement. FSUIPC calibration cannot repair a device that Windows reads incorrectly.
2. Remove duplicate FSX assignments. Delete each FSX binding that FSUIPC will handle. If all joystick inputs will be assigned through FSUIPC, disabling FSX controller processing is a clean alternative.
3. Detect one axis at a time. Open Add-ons > FSUIPC, select the axis-assignment page and move only the intended lever or control. Use Rescan if the wrong axis remains selected.
4. Choose one routing method. Use Send direct to FSUIPC Calibration for conventional flight controls, or Send to FS as normal axis when an aircraft’s documentation requires a native FSX axis event. Never send the same lever by both routes.
5. Calibrate after assigning. Set the minimum and maximum just inside the stable physical limits. Add a small centre or idle zone only where the control needs one.
6. Assign buttons and switches. A momentary button usually needs a press action. A maintained two-position switch may need one action when pressed and another when released.
7. Create aircraft profiles where necessary. Use separate profiles for aircraft needing different throttle, propeller, mixture or custom-event arrangements. Include related liveries in the intended profile so changing repaint does not appear to erase the controls.

For the complete workflow, including duplicate-input prevention and profile setup, use our detailed FSUIPC axis and button procedure. The worked TOGA button example shows how the same method applies to a specific aircraft command.

Direct to FSUIPC calibration or send to FS as a normal axis

Use direct calibration for conventional controls unless the aircraft developer explicitly requires a native FSX event or a proprietary control utility.

For an axis routed through FSX, start with full FSX sensitivity and a minimal null zone unless the aircraft instructions say otherwise. Direct FSUIPC axes bypass those FSX sensitivity settings.

Calibration details that prevent common control problems

Calibrate only after removing duplicate assignments and confirming that the hardware produces stable values.

• Throttles: assign a combined throttle for one physical lever or per-engine axes for separate levers. Create a reverse zone only if the hardware has a repeatable detent.
• Rudder: set a narrow centre region to stop minor sensor noise moving the virtual pedals.
• Toe brakes: confirm that fully released pedals produce no braking. If the response is backwards, reverse the axis in calibration instead of creating a second assignment.
• Response slopes and filtering: apply these after the endpoints and centre are correct. They will not cure duplicate bindings or a failing potentiometer.

Connecting add-ons through FSUIPC4

Most local add-ons that list FSUIPC as a communications requirement need no FSUIPC control assignments and no registered user licence.

Start FSX, load a flight and then launch or activate the add-on according to its instructions. If it reports “waiting for simulator”, first confirm that Add-ons > FSUIPC exists; without that menu, the module itself has not loaded.

• Complex aircraft: an aircraft may require standard FSX events, custom controls or its own configuration tool even though it also communicates through FSUIPC.
• Networked clients: software running on another computer is a WideFS case. Installing or registering FSUIPC4 alone does not create the network connection.
• Old or incompatible add-ons: FSUIPC cannot convert an aircraft, gauge or utility made for a different simulator into an FSX-compatible product.

Troubleshooting FSUIPC4 in FSX

Start by separating a module-loading failure from a control-assignment problem: if the FSUIPC menu is absent, changing axes or reinstalling joystick drivers will not help.

If a trust prompt was rejected, back up fsx.cfg, remove only the line referring to FSUIPC4.dll from its trusted-software section, then restart FSX and approve the new prompts. Do not delete unrelated trusted entries.

When the log points to DLL.xml, back it up and repair only the FSUIPC entry. Replacing the complete file can remove other module declarations. If security software quarantined the DLL, restore it only after verifying the package, then exclude the specific file or module folder rather than reducing protection globally.

For a clean configuration test, close FSX, back up and rename Modules\FSUIPC4.ini, then start FSX again. FSUIPC will create a fresh INI without the old assignments, calibration or profiles. Keep the original file and any separate licence file until the replacement configuration is proven.