Precision Flight Serial CAT I and Microsoft Flight Simulator 9 (2004) - Manual (Page 13)

Set Up Guide for Serial CAT1 and FS2004 Page 13
C3. Rudder Calibration
10. Make sure that your rudder trim is centered.
11. Now click on Select button under the Rudder Axis. This should say Set Automatic now.
12. Push your left pedals all the way to the Left and hold it. Click on the Set left most limit.
13. Push your right pedals all the way to the Right and hold it. Click on the Set right most limit.
D. Enable and calibrate trim
NOTE:
Before enabling the Aileron or Rudder trim, you will need to make sure that your trim is a
separate channel.
14. Go to the Trims & Steering tab.
15. Enable the Rudder Trim and turn it left to right and see if the indicator is responding.
If your rudder trim is not responding: