The effect of deflecting flaps on strike/fighter aircraft wing design

Abstract

The designer of a strike/fighter wing must bear in mind the many manoeuvres which the aircraft must perform. It is not sufficient to consider a single altitude cruise design point. Instead one must aim for:(a) An economic altitude cruise, i.e. a moderately high Mach number and lift coefficient without drag rise.(b) A sea level dash capability, i.e. a high subsonic Mach number and a low lift coefficient without drag rise.(c) Good manoeuvrability at intermediate and high subsonic Mach numbers, requiring high maximum usable lift coefficients.(d) Good field performance with very high lift coefficients in both take-off and landing configurations.(e) Some supersonic capability.Such a wide range of performance inevitably leads to some incompatability in the design. The high speed requirements are necessarily in conflict with those at low speed and similarly there is an inconsistency between the needs for altitude cruise and sea level dash. Reference 1 develops a design procedure based on fixed geometry sections, which attempts to satisfy all the design requirements in a reasonable manner. This paper is restricted to consideration of a method in which flap deflections may be incorporated into the design conditions so that the general performance can be improved without seriously degrading any of the individual requirements.