What is meant by the mean aerodynamic chord (MAC)?

• A. The rate of climb of the aircraft.
• B. The chord length at the root of the wing.
• C. The chord of an imaginary airfoil that has the same aerodynamic characteristics of an actual airfoil.
• D. The maximum aerodynamic efficiency.

Answer: (C)

Mean aerodynamic chord is the chord length of a hypothetical airfoil that would produce the same lift distribution as the actual wing at a given condition. In other words, it’s the representative chord that accounts for how the wing’s taper and planform cause lift to vary along the span, effectively averaging the wing’s geometry into a single, meaningful length. This MAC is used to locate the aerodynamic center and to position the aircraft’s center of gravity relative to the wing.

It’s not the rate of climb, not the root chord, and not the maximum aerodynamic efficiency (which relates to the lift-to-drag ratio, not a single chord length).