The angle of attack is defined as the angle between the wing chord line and the relative wind.

• A. Between the wing leading edge and the relative wind
• B. Between the wing trailing edge and the relative wind
• C. Between the fuselage and the relative wind
• D. Between the wing chord line and the relative wind

Answer: (D)

Angle of attack is the angle between the wing's chord line and the relative wind. The chord line runs from the wing’s leading edge to its trailing edge, and the relative wind is the airflow direction relative to the wing (the air approaching the wing as the airplane moves through it). This specific geometric relationship—between the chord line and the oncoming air—determines how the air is deflected over the wing and, in turn, how much lift is produced. It’s not measured from the leading edge or from the fuselage, and the trailing edge isn’t the reference line either. In flight, increasing the angle of attack generally increases lift up to a critical point, beyond which flow separation causes a stall.