An experimental investigation has been carried out to compare the effects of sweep direction upon the aerodynamic characteristics of three wing planforms. The wings have biconvex aerofoil sections which allow them to be tested in both the forward-swept and backward-swept configurations without changing the section profile. Measurements of lift, drag and pitching moment have been made for angles of incidence in the range —5° to +50° at a mean chord Reynolds number of approximately 1·5 × 105 and a Mach number of 0·1. To complement the force and moment data a comprehensive series of oil-flow visualisations are also presented. In addition the aerodynamic characteristics of simple strakes (wing root fillets) have been studied for both the swept-forward and swept-back configurations.

The unsteady planar flow of inviscid compressible fluid past an oscillating aerofoil is considered. Many recent computational studies have experienced difficulties in obtaining accurate, or any, results at medium or higher frequencies of oscillation. This may well be due to the emergence of multi-scaling and multi-regions according to the present analytical study which concentrates on the large frequency properties of the linearised flowfield. Multi-scaled dependence in the solution is found to occur in both the streamwise and transverse directions. Comparisons are made with computational results.

A similitude has been obtained for delta wings with attached leading edge shock at large incidence in hypersonic flow. A strip theory in which flow at a spanwise location is two-dimensional has been developed. This combines with the similitude to lead to a piston theory which gives closed form solutions for unsteady derivatives in pitch and roll. The derivatives in pitch are independent of and the roll damping derivative varies linearly with the aspect ratio. Substantially the same results as the theory of Liu and Hui are obtained with remarkable computational ease.

Wing tip sails are small lifting surfaces fitted to the wings in such a way that they use the local air flows about the wing tips, induced by the generation of lift on the wing, to produce a thrust. They act in a manner similar to that of the sail of a yacht when it is sailing close to the wind, hence their name.

Previous work, described in references 1, 2 and 3, has investigated the effects of adding sails to existing wings, extending their span and wetted area. It has long been realised that the correct use of sails is to replace part of the outer wing area with them, in other words to include them in the initial design of the wing. This note describes wind tunnel tests on a simple untapered, unswept wing to examine the benefits from such a design approach and subsequent flight tests on a Cessna Centurion to confirm them.