Measurements of wing buffeting, using root strain gauges, were made in the Nasa Langley 0-3 m cryogenic windtunnel to refine techniques which will be used in larger cryogenic facilities such as the United States National Transonic Facility (NTF) and the European Transonic Windtunnel (ETW). The questions addressed included the relative importance variations in frequency parameter and Reynolds number, the choice of model material (considering both stiffness and damping) and the effects of static aeroelastic distortion.

The main series of tests was made on three half models of slender 65° delta wings with a sharp leading edge. The three delta wings had the same planform but widely differing bending stiffnesses and frequencies (obtained by varying both the material and the thickness of the wings). It was known that the steady flow on this configuration would be insensitive to variations in Reynolds number. On this wing at vortex breakdown the spectrum of the unsteady excitation is unusual, having a sharp peak at particular frequency parameter.

Additional tests were made on one unswept half-wing of aspect ratio 1·5 with an NPL 9510 aerofoil section, known to be sensitive to variations in Reynolds number at transonic speeds. The test Mach numbers were M = 0·21 and 0·35 for the delta wings and to M = 0·30 for the unswept wing. On this wing the unsteady excitation spectrum is fairly flat (as on most wings). Hence correct representation of the frequency parameter is not particularly important.

An analysis technique capable of simulating the effect of engine failure during takeoff from offshore platforms is presented. Use is made of inverse simulation whereby the control actions required for a subject helicopter to follow a particular trajectory can be established. A mathematical representation of the towering takeoff procedure, and details of the modified inverse simulation technique needed to cope with the modelling of an engine failure are described. Detailed piloting accounts of the strategy used to fly the towering takeoff (with and without engine failures) are also given and are used to give qualitative validation of the analytical approach. Simulation results for a single engine failure of a transport helicopter during critical phases of a towering takeoff are presented. Finally, some directions for future work and potential applications of the technique are discussed.

The influence of isolated spherical roughness elements upon the transition of a three-dimensional boundary layer on a swept flat plate is discussed in this paper. Perturbations induced by the roughness are found to be more effective on the start of transition rather than the crossflow of the laminar undisturbed boundary layer at the roughness location.

This paper describes an investigation of the aerodynamic characteristics of collectively variable incidence wing tips at low speeds. Theoretical considerations supported by experimental measurements suggest that the use of articulated tips which can be rotated to a high incidence for low speed flight will decrease sensitivity to gusts. Furthermore, windtunnel measurements demonstrate that the use of very high tip incidences can produce an increment in maximum overall lift coefficient for some wing configurations. Another feature investigated is the possibility of utilising the lift increment for the purposes of direct lift control. The use of a radio controlled model to test the practical viability of the concept is described.