My plane is pulling away

[NedLynch]

What Snapper said.

In addition check in the settings/axes if your joystick inputs stay neutral when you don't touch the stick. There you can also adjust deadzones and how the movement of the stick is being translated into movements of the control surfaces in flight, i.e. 1:1, more agressive, less aggressive, play around with those settings and see what you like best.