Wing loading is an aerodynamic variable applied to aircraft that is a product of the loaded weight of the plane divided by its wing area. The wing loading characteristics of any aircraft are design features which dictate overall performance in several areas including lift capabilities, landing and take-off speeds, and maneuverability. Generally in slower commercial designs, the larger the aircraft's wings are in relation to its weight, the better it will perform overall. In high speed designs however, the opposite is true, with smaller wings and higher wing loadings giving superior performance. Some flexibility is necessary in high speed designs, however, because they also operate at lower speeds and necessitate multipurpose wing designs such as variable sweep and blended fuselage types.
One of the most critical areas of aerodynamic design is the wing loading factor of any given aircraft. This variable is the corner stone on which the character of each aircraft design is founded. Wing loading is a function of loaded weight and total wing area and is expressed in pounds per square foot (lbs/ft2) or kilograms per square meter (kg/m2). To calculate wing loading figures, the all-up loaded weight of the aircraft is divided by the total area of its wings. The larger the wings in relation to the overall weight of the aircraft, the lower its wing loading factor and vice versa.
This relationship has a fundamental effect on how aircraft engineers achieve their design requirements. For instance, aircraft with low wing loading values, i.e., those with large wing surfaces in relation to their maximum weight, feature better performance at lower speeds. They generally have higher lift capability with lower takeoff and landing speeds and better performance during climb and cruise phases of flight. They are also more maneuverable throughout their speed range, particularly at the lower speeds. High speed aircraft such as fighters will, however, generally have smaller wing profiles and larger wing loading figures giving them better performance at high speeds.
High speed fighter aircraft also have to take off and land and are often called on to perform at lower speeds where stability and maneuverability are critical. This wide range of wing load requirements have led to several lateral developments in fighter design which included the F-16 and MiG 29 blended fuselage/wing configurations and the variable sweep wings on the F-14. This allows for lower wing loading values with its related improvement in low speed performance while maintaining the small wing profile necessary for supersonic flight. The use of leading and trailing edge devices such as slats and Fowler flaps also allow the overall wing area and profile to be adjusted to lend stability and performance during low speed phases of flight. This is an essential wing design feature on aircraft with wide operational speed envelopes such as large commercial jets.