Chord (aeronautics)

In aeronautics, the chord is an imaginary straight line segment joining the leading edge and trailing edge of an aerofoil cross section parallel to the direction of the airflow.

[2] For a turbine aerofoil, the chord may be defined by the line between points where the front and rear of a 2-dimensional blade section would touch a flat surface when laid convex-side up.

[3] The wing, horizontal stabilizer, vertical stabilizer and propeller/rotor blades of an aircraft are all based on aerofoil sections, and the term chord or chord length is also used to describe their width.

The chord of a wing, stabilizer and propeller is determined by measuring the distance between leading and trailing edges in the direction of the airflow.

The term chord is also applied to the width of wing flaps, ailerons and rudder on an aircraft.

To provide a characteristic figure that can be compared among various wing shapes, the mean aerodynamic chord (abbreviated MAC) is used, although it is complex to calculate.

The pressure distribution over the entire wing can be reduced to a single lift force on and a moment around the aerodynamic center of the MAC.

Note that the figure to the right implies that the MAC occurs at a point where leading or trailing edge sweep changes.