Originally Posted by
unmanned_droid
What your nephew is doing is a banked turn with an extreme angle of bank (certainly compared to a lot of GA). It is usually not a balanced turn as GA teaches it, and it is necessary to pull positive G (considerable amounts) in order to maintain height as well as change heading.
Maybe not a balanced turn as taught for GA in the sense that rudder is generally not consciously applied by the pilot, but in all of the FJ types I've flown it would be expected that the ball stayed roughly in the middle under the action of stability augmentation systems (yaw dampers and the like) so the practical outcome was a balanced turn. I never flew the Jag, but understood that it was particularly prone to departure from controlled flight under pitch-yaw coupling...