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A fixed-wing aircraft may have more than one wing plane, stacked one above another: Biplane: two wing planes of similar size, stacked one above the other. The biplane is inherently lighter and stronger than a monoplane and was the most common configuration until the 1930s. The very first Wright Flyer I was a biplane.
The blue and light green shapes are roughly equal in area. The Whitcomb area rule, named after NACA engineer Richard Whitcomb and also called the transonic area rule, is a design procedure used to reduce an aircraft's drag at transonic speeds which occur between about Mach 0.75 and 1.2.
For example, the NACA 712A315 has the area of minimum pressure 10% of the chord back on the upper surface and 20% of the chord back on the lower surface, uses the standard "A" profile, has a lift coefficient of 0.3, and has a maximum thickness of 15% of the chord.
To generate enough lift at a given wingspan, the aircraft designer must increase wing area by lengthening the chord, thus lowering the aspect ratio. This limits the Airbus A380 to 80m wide with an aspect ratio of 7.8, while the Boeing 787 or Airbus A350 have an aspect ratio of 9.5, influencing flight economy.
Aircraft use the wing area (or rotor-blade area) as the reference area, which makes for an easy comparison to lift. Airships and bodies of revolution use the volumetric coefficient of drag, in which the reference area is the square of the cube root of the airship's volume. Sometimes different reference areas are given for the same object in ...
The pressure surface (a.k.a. lower surface) has a comparatively higher static pressure than the suction surface. The pressure gradient between these two surfaces contributes to the lift force generated for a given airfoil. The geometry of the airfoil is described with a variety of terms :
Supercritical airfoils feature four main benefits: they have a higher drag-divergence Mach number, [21] they develop shock waves farther aft than traditional airfoils, [22] they greatly reduce shock-induced boundary layer separation, and their geometry allows more efficient wing design (e.g., a thicker wing and/or reduced wing sweep, each of which may allow a lighter wing).
The ratio of the length (or span) of a rectangular-planform wing to its chord is known as the aspect ratio, an important indicator of the lift-induced drag the wing will create. [7] (For wings with planforms that are not rectangular, the aspect ratio is calculated as the square of the span divided by the wing planform area.)