Angle of incidence is the acute angle formed between which two elements?

• A. The wing tip and fuselage centerline.
• B. The chord line of the airfoil and the aft fuselage surface.
• C. The chord line of the airfoil and the longitudinal axis of the aircraft.
• D. The wing root and the tailplane.

Answer: (C)

The angle of incidence is the fixed angle between the wing’s chord line and the aircraft’s longitudinal axis. The chord line runs from the wing’s leading edge to its trailing edge, while the longitudinal axis is the nose-to-tail line along the aircraft’s center. This mounting angle is set during design and remains essentially constant in flight, establishing the baseline orientation so that, in the aircraft’s normal cruising attitude, the wing presents the appropriate angle of attack for lift. It’s not about the wing tip relative to the fuselage centerline, nor about the chord line relative to the aft fuselage surface, nor about the wing root to the tailplane. The angle of attack, which is different, is the angle between the chord line and the oncoming air, and it can change with pitch and flight conditions.