Editing Wing (section)

===Cross-sectional shape===
Wings with an asymmetrical cross-section are the norm in [[subsonic flight]]. Wings with a symmetrical cross-section can also generate lift by using a positive [[angle of attack]] to deflect air downward. Symmetrical airfoils have higher [[Stall (flight)|stalling]] speeds than [[Camber (aerodynamics)|cambered airfoils]] of the same wing area<ref>E. V. Laitone, Wind tunnel tests of wings at Reynolds numbers below 70 000, ''Experiments in Fluids'' '''23''', ''405'' (1997). {{doi|10.1007/s003480050128}}</ref> but are used in [[aerobatic]] aircraft as they provide the same flight characteristics whether the aircraft is upright or inverted.<ref>The Design Of The Aeroplane,Darrol Stinton,{{ISBN|0 632 01877 1}},p.586</ref> Another example comes from sailboats, where the sail is a thin sheet.<ref name=Babinsky>"...consider a sail that is nothing but a vertical wing (generating side-force to propel a yacht). ...it is obvious that the distance between the stagnation point and the trailing edge is more or less the same on both sides. This becomes exactly true in the absence of a mast—and clearly the presence of the mast is of no consequence in the generation of lift. ''Thus, the generation of lift does not require different distances around the upper and lower surfaces.''" Holger Babinsky ''How do Wings Work?'' Physics Education November 2003, [http://iopscience.iop.org/0031-9120/38/6/001/pdf/pe3_6_001.pdf PDF]</ref>

For flight speeds near the speed of sound ([[transonic flight]]), specific asymmetrical airfoil sections are used to minimize the very pronounced increase in drag associated with airflow near the speed of sound.<ref>John D. Anderson, Jr. ''Introduction to Flight'' 4th ed page 271.</ref> These airfoils, called [[supercritical airfoil]]s, are flat on top and curved on the bottom.<ref>'Supercritical wings have a flat-on-top "upside down" look.' NASA Dryden Flight Research Center http://www.nasa.gov/centers/dryden/about/Organizations/Technology/Facts/TF-2004-13-DFRC.html</ref>