= Aircraft wing
An \b[aircraft wing] is an aerodynamic lifting structure of an <aircraft>. Its three-dimensional shape combines <airfoil> sections with a spanwise arrangement described by the <wing planform>. The <airfoil> specifies a local profile; the <wing planform> specifies the shape seen from above. <Wingspan>, <wing area>, <wing taper ratio> and <wing sweep> describe different aspects of that geometry.<Wing Geometry by NASA Glenn Research Center>[Top View and Airfoil Geometry: span, planform and sectional shape]{ref}
The surrounding <fluid flow> exerts <pressure> and <viscous stress> on the wing's surface. Integrating these surface forces gives a resultant whose component perpendicular to the incoming flow is <lift> and whose parallel component is <drag>. A useful whole-wing relation is
$$
L=\frac12\rho V^2 S C_L,
$$
where $\rho$ is air <density>, $V$ is flight speed relative to the air, $S$ is <wing area> and $C_L$ is <lift coefficient>. The <lift coefficient> packages the effects of shape and operating conditions, including <angle of attack>; it is not determined by <wing area> alone.
For a stipulated example, $\rho=1.2\,\mathrm{kg/m^3}$, $V=30\,\mathrm{m/s}$, $S=10\,\mathrm{m^2}$ and $C_L=0.8$ give <dynamic pressure> $540\,\mathrm{Pa}$ and <lift> $4320\,\mathrm{N}$. Halving the speed at unchanged <lift coefficient> reduces <lift> to one quarter. Maintaining the original <lift> would require $C_L=3.2$, which the actual wing might be unable to achieve before <aerodynamic stall>.
A <wind tunnel> makes the shape–force connection measurable: hold a model at controlled <angle of attack>, measure its <lift> and <drag> with a balance, and vary the model or flow conditions. Such measurements distinguish a geometrical description from an aerodynamic prediction. Two wings with equal <wingspan> and <wing area> can still have different <lift coefficients>, <drag> and stall behavior.
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