In this week’s installment, I thought that I would discuss airfoils in more detail. All airplanes have wings, and all wings are shaped according to airfoils. Therefore, understanding airfoils is central in aircraft design.
Airfoils can be obtained by taking cross-sections of a wing that are parallel to the fuselage. Therefore, they can provide much information about how air flows over top and underneath a wing. Since wings generate lift by deflecting air downwards, airfoils are also central in understanding how much lift a plane generates.
During the 1920s, the National Advisory Committee for Aeronautics (NACA) developed a system of naming conventions for airfoils. One of the most prominent collections of airfoils in this categorization system is the NACA “4-series,” which distinguishes airfoils based on chord, camber, position of maximum camber, and thickness. The distance of a straight path from the leading leading edge of an airfoil to the trailing edge is denoted by the term “chord.” In calculations, aerospace engineers frequently adjust other measurements to be expressed as a percentage of the chord. Meanwhile, the camber line is an “average” curve that engineers draw through an airfoil from the leading edge to the trailing edge that corresponds to the airfoil’s curviness. The maximum distance (expressed as a percentage of chord) between the camber line and the chord line is denoted by the term “camber.” Therefore, camber captures how bendy an airfoil is. The position of maximum camber is the distance (expressed as a percentage of chord) from the leading edge to the point at which the camber line is farthest above the chord line. Finally, the term “thickness” refers to the maximum thickness of an airfoil, again expressed as a percentage of the chord.
With this NACA naming system in place, engineers can choose a particular chord that a wing should have, and then depending on the specifics of the plane’s mission, determine exactly what airfoil to base the rest of the wing off of. As we will discover in future posts, different airfoils can produce different amounts of lift and drag in differing scenarios.