 On most propeller powered aircraft, the rotation of the propeller(s) induces a counteracting roll movement due to Newton's third law of motion, in that every action has an equal and opposite reaction.To relieve the pilot of having to provide continuous pressure on the stick in one direction (which causes fatigue) trim tabs are provided to adjust or "trim out" the pressure needed against any unwanted movement.The tab itself is deflected in relation to the aileron, causing the aileron to move in the opposite direction.