On that radio, select 'plane' or 'airplane' mode! It does no mixing according to the manual, page 6. http://www.hobbyking.com/hobbyking/store/uploads/137920662X387078X43.pdf
You can see on page 5 (labeled 4) in the manual above that 1-4 are Aileron (roll), Elevator (pitch), Throttle & Rudder...