Well the probelm is that XWA thinks the thrid Axis on your stick are rudder pedals. Which they are not. GO to the Option screen by hitting Escape. ANd select "Game Controlers" there should be a thing to select Rudders on/off make sure it is off.
It is kinda hard to get used to, so practice a lot with it, and you can be among the best XWA pilots out there