Final answer:
The axis of a turn and bank indicator is vertical and perpendicular to the lateral aircraft axis, important for understanding the lift forces during a banked turn.
Step-by-step explanation:
A turn and bank indicator axis is vertical and is perpendicular to the lateral aircraft axis. When an airplane is in a banked turn, the lift force generated by the air on the wing is divided into two components. One component acts vertically to balance the weight of the airplane, while the other acts horizontally to provide the centripetal force necessary for the turn. The angle of bank, which indicates how much the aircraft is tilted from its original level position, affects the magnitude of these lift components. Mastery of the relationship between banking angle and the corresponding changes in lift force components is critical for pilot training and safe aircraft operation.