Wing-loading

In aerodynamics, wing loading is the total mass of an aircraft divided by the area of its wing. The stalling speed of an aircraft in straight, level flight is partly determined by its wing loading. An aircraft with a low wing loading has a larger wing area relative to its mass, as compared to an aircraft with a high wing loading.

The faster an aircraft flies, the more lift can be produced by each unit of wing area, so a smaller wing can carry the same mass in level flight. Consequently, faster aircraft generally have higher wing loadings than slower aircraft. This increased wing loading also increases takeoff and landing distances. A higher wing loading also decreases maneuverability. The same constraints apply to winged biological organisms.

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

${\displaystyle \textstyle {\frac {L}{A}}={\tfrac {1}{2}}v^{2}\rho C_{L}}$,

where ρ is the density of air and C_L is the lift coefficient. The latter is a dimensionless number of order unity which depends on the wing cross-sectional profile and the angle of attack. At take-off or in steady flight, neither climbing nor diving, the lift force and the weight are equal. With L/A = Mg/A =W_Sg, where M is the aircraft mass, W_S = M/A the wing loading (in mass/area units, i.e. lb/ft² or kg/m², not force/area) and g the acceleration due to gravity, that equation gives the speed v through

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