Chord line in an airfoil is defined as which line?

• A. An imaginary straight line drawn through an airfoil from the leading edge to the trailing edge.
• B. A line from root to tip.
• C. A line along the wing's chord at mid-span.
• D. A line from nose to tail.

Answer: (A)

The chord line is the straight line drawn from the airfoil’s leading edge to its trailing edge. It defines the chord direction and length and serves as the reference for measuring the angle of attack, which is the angle between this line and the relative wind. The camber line, by contrast, is the curved line halfway between the upper and lower surfaces, used to describe the airfoil’s camber, not the chord direction. The other descriptions refer to spanwise or longitudinal axes, not the airfoil’s cross-sectional reference line.