The aerodynamics of jet flaps

Abstract

With jet-flap wings a considerable proportion of the jet efflux leaves the wing trailing edge as a plane jet sheet inclined to the relative mainstream. The lift generated is several times the corresponding vertical component of the jet momentum, while the sectional thrust lies between the corresponding horizontal component and full jet momentum. After introducing briefly the origin and primary concepts of jet flaps, this paper discusses progress towards the clarification and formulation of jet-flap aerodynamics, mainly by an examination and analysis of recent Royal Aircraft Establishment and National Physical Laboratory research work. The aspects considered comprise lift, pitching moment and downwash, sideslip derivatives, and the effects of ground proximity. Some associated implications with regard to jet-flap aircraft performance, stability and control are also mentioned.