What you're changing and why it matters

The ACT (Air Cycle Thermal) tanks on a Fenix A321 are part of the air conditioning and pressurization system. Changing the number of tanks — typically from two to three or vice versa — alters how the aircraft manages cabin temperature and humidity during flight. This is a structural and systems modification that requires changes to the aircraft configuration file, not a straightforward panel adjustment.

Most pilots make this change to match their preferred realism level or to test how different tank configurations affect system performance in the simulator. The modification is done through the aircraft's configuration settings, which control how many tanks the systems logic recognizes and displays on your overhead panel.

Key Takeaways

  • ACT tank count is controlled in the aircraft configuration file, not through in-sim menus or panel switches.
  • The Fenix A321 typically ships with a default configuration that you modify by editing text-based configuration files in your community folder.
  • After changing the configuration, you must restart the simulator completely for the change to take effect.
  • Backup your original configuration file before making changes, so you can revert if something goes wrong.

Locating the configuration file

The Fenix A321 configuration files are stored in your Microsoft Flight Simulator community folder. On Windows, this is typically located at C:\Users\[YourUsername]\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalState\packages\community. On Mac systems, the path varies depending on your installation method.

Inside the community folder, find the Fenix A321 aircraft folder. It is usually named something like fenix-a321 or a321-fenix. Open that folder and look for a file named aircraft.cfg or a similar configuration file. This is the file you will edit to change the ACT tank count.

If you cannot find the community folder, open Flight Simulator, go to Options, then General, and look for the Community Folder path listed there. You can click the folder icon to open it directly.

Editing the configuration file

Open the aircraft configuration file with a plain text editor such as Notepad (Windows) or TextEdit (Mac). Do not use Word or another word processor, as these add formatting that will break the file. Search for the line that contains act_tanks or num_act_tanks or similar wording related to ACT tank count.

The line will look something like act_tanks = 2 or num_act_tanks = 2. Change the number to your desired value. Most Fenix A321 configurations support either 2 or 3 tanks. Set it to whichever you prefer, then save the file. Make sure you save it as a plain text file with no added formatting.

If you cannot find an ACT tank line in the file, the configuration may not expose this setting, or it may be named differently. Check the Fenix documentation or community forums for the exact parameter name used in your version of the aircraft.

Restarting the simulator and verifying the change

Close Microsoft Flight Simulator completely if it is running. Do not just close the current flight — exit the entire process. Then reopen Flight Simulator and load the Fenix A321. The overhead panel should now show the number of ACT tanks you specified in the configuration file.

Check the air conditioning panel to confirm the tanks are displayed and functional. If the change did not take effect, verify that you saved the configuration file correctly and that you closed and reopened the simulator. Configuration changes do not explore while the simulator is running.

Reverting to the original configuration

If the change causes problems or you want to return to the default tank count, you have two options. The simplest is to delete the modified configuration file from your community folder. Flight Simulator will then use the default configuration that came with the aircraft. Alternatively, if you made a backup of the original file before editing, you can restore that backup.

To create a backup before making changes, right-click the aircraft.cfg file, select Copy, then right-click in the same folder and select Paste. Rename the copied file to something like aircraft.cfg.backup. If you need to revert, straightforward delete the modified file and rename the backup back to aircraft.cfg.

Troubleshooting common issues

If the simulator crashes after your change, the most likely cause is a syntax error in the configuration file. Open the file again and check that the line you edited follows the same format as other lines in the file — usually parameter = value with no extra spaces or characters. Save it again and restart the simulator.

If the ACT tanks still show the old count after restarting, you may have edited the wrong file or the file did not save properly. Verify that you are editing the configuration file in the community folder, not a default file elsewhere. Also check that your text editor did not add a file extension like .txt to the filename when you saved it.

If the overhead panel shows the new tank count but the systems do not behave as expected, the issue may be with how the aircraft logic handles that specific tank configuration. Consult the Fenix documentation or community support channels for known limitations or required additional changes.

Frequently Asked Questions

Will changing the ACT tank count affect my saved flights?

Saved flights may not load correctly if you change the tank count after saving them. If you want to keep a saved flight with the original configuration, either revert the tank count before loading it or start a new flight after making the change.

Can I have different tank counts for different aircraft liveries?

Not easily. The configuration file controls the aircraft model itself, not individual liveries. If you want different tank counts, you would need separate aircraft folders or a more complex setup. Most users stick with one tank configuration for the entire aircraft.

What is the difference between 2 and 3 ACT tanks in terms of performance?

In the Fenix A321, the tank count affects how the air conditioning system distributes cooling load and how it responds to cabin temperature changes. Three tanks provide more granular control and slightly faster response times, while two tanks simplify the system. The difference is most noticeable during high-altitude flight or in hot climates.

Do I need to reinstall the Fenix A321 if I mess up the configuration file?

No. You can straightforward restore your backup or delete the modified file and let the simulator use its default version. Reinstalling the aircraft should be your last resort if the default configuration is also corrupted.