Wing loading
In aerodynamics, wing loading is the loaded mass of the aircraft divided by the area of the wing. An aircraft with a low wing loading has a larger wing area relative to its mass (i.e. a glider), as compared to an aircraft with a high wing loading (i.e. fighter jet, or modern airliner).
The faster an aircraft flies, the more lift is produced by each unit of wing area, so a smaller wing can carry the same weight in level flight, therefore increasing the wing loading. This increased wing load also increases takeoff and landing distances and speeds. A high wing loading also decreases maneuverability. The same constraints apply to winged biological organisms.
The table, which shows wing loadings, is intended to give an idea of the range of wing loadings used by aircraft. Maximum weights have been used. There will be variations amongst variants of any particular type. The dates are approximate, indicating period of introduction.
The upper critical limit for bird flight is about 25 kg/m2 (5.1 lb/sq ft). An analysis of bird flight which looked at 138 species ranging in mass from 10 g to 10 kg, from small passerines to swans and cranes found wing loadings from about 1 to 20 kg/m2. The wing loadings of some of the lightest aircraft fall comfortably within this range. One typical hang glider (see table) has a maximum wing loading of 6.3 kg/m2, and an ultralight rigid glider 8.3 kg/m2.
Wing loading is a useful measure of the general maneuvering performance of an aircraft. Wings generate lift owing to the motion of air over the wing surface. Larger wings move more air, so an aircraft with a large wing area relative to its mass (i.e., low wing loading) will have more lift available at any given speed. Therefore, an aircraft with lower wing loading will be able to take off and land at a lower speed (or be able to take off with a greater load). It will also be able to turn at a higher speed.
Quantitatively, the lift force L on a wing of area A, traveling at speed v is given by
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