Chord (aeronautics)

In aeronautics, the chord of an airfoil is the straight line connecting the leading edge and trailing edge. The chord length, or simply chord, is the length of this line, measured from the leading edge to the trailing edge.

The chord is a fundamental reference dimension for an airfoil. It is used in calculations related to the airfoil's lift, drag, and moment coefficients. It is also used in determining the airfoil's aspect ratio (the ratio of wingspan to chord).

The chord can vary along the span of a wing. In such cases, the term root chord refers to the chord at the wing root (where the wing joins the fuselage), and the tip chord refers to the chord at the wingtip. The average chord is the average of all chords along the span. A wing with a constant chord is said to have a constant chord or rectangular planform. A wing whose chord varies along the span is said to have a tapered planform.

The chord line is also used as a reference for defining the angle of attack, which is the angle between the chord line and the oncoming airflow.