Define angle of attack.

Define angle of attack.

• A. The angle between the wing's chord line and the relative wind
• B. The angle between the wing's leading edge and the horizon
• C. The angle between wingtip and fuselage
• D. The angle between the relative wind and the tailplane

Answer: (A)

Angle of attack is the angle between the wing’s chord line and the relative wind. The chord line is an imaginary line from the wing’s leading edge to its trailing edge, and the relative wind is the airflow that encounters the wing, coming from the direction opposite the aircraft’s motion. This angle is what mostly determines lift: as it increases, lift rises up to a point, then flow separation causes a stall. The other ways of measuring an angle—such as between the leading edge and the horizon (which describes pitch attitude with respect to the ground), between wingtip and fuselage, or between the relative wind and the tailplane—do not define how the wing meets the oncoming air.

Angle of attack is the angle between the wing’s chord line and the relative wind. The chord line is an imaginary line from the wing’s leading edge to its trailing edge, and the relative wind is the airflow that encounters the wing, coming from the direction opposite the aircraft’s motion. This angle is what mostly determines lift: as it increases, lift rises up to a point, then flow separation causes a stall. The other ways of measuring an angle—such as between the leading edge and the horizon (which describes pitch attitude with respect to the ground), between wingtip and fuselage, or between the relative wind and the tailplane—do not define how the wing meets the oncoming air.