Editing Delta wing (section)

====Low-speed flight and vortex lift====
Like any wing, at low speeds a delta wing requires a high [[angle of attack]] to maintain lift. At a sufficiently high angle the wing exhibits [[flow separation]], together with an associated high drag.<ref name=":0">{{Cite book|title=High Angle of Attack Aerodynamics: Subsonic, Transonic, and Supersonic Flows|url=https://archive.org/details/highangleattacka00romj|url-access=limited|last=Rom|first=Josef|date=1992|publisher=Springer New York|isbn=9781461228240|location=New York, NY|pages=[https://archive.org/details/highangleattacka00romj/page/n24 15]–23|oclc=853258697}}</ref>

Ordinarily, this flow separation leads to a loss of lift known as the [[Stall (fluid dynamics)|stall]]. However, for a sharply-swept delta wing, as air spills up round the leading edge it flows inwards to generate a characteristic [[vortex]] pattern over the upper surface. The lower extremity of this vortex remains attached to the surface and also accelerates the airflow, maintaining lift. For intermediate sweep angles, a retractable "moustache" or fixed [[leading-edge root extension]] (LERX) may be added to encourage and stabilise vortex formation. The ogee or "wineglass" double-curve, seen for example on [[Concorde]], incorporates this forward extension into the profile of the wing.

In this condition, the centre of lift approximates to the centre of the area covered by the vortex.