Tonight we commemorate the achievements of Juan de la Cierva, the great pioneer of rotary aviation. His development of the autogyro stimulated the development of the early rotor theories and paved the way for the modern helicopter. In turning the autogyro into a practical aircraft, Cierva proved to be an innovator prepared to take an unconventional approach. He was at the same time pragmatic in that he really wanted to build a helicopter but realised that the required technology was not yet mature, and settled on the autogyro as representing what was an achievable concept. His concept was thus unconventional, dramatic and achievable — an admirable combination. However, in his first attempts to fly an autogyro he rapidly came up against the problem that faces all rotory wing designers — which is that the advancing blade has a much greater lifting potential than the retreating blade, due to the difference in dynamic head. This led him to introduce the flapping hinge that allowed the rotor to achieve roll balance as well as providing the backward tilt of the rotor that is necessary for autorotation. Having made this step forward, he realised that the introduction of blade camber would allow the retreating blade to achieve higher angles of incidence before stalling, but in so doing he built in a potentially dangerous control characteristic.

A computational analysis is performed of self-sustained oscillatory flow over a cavity driven by a shear layer at Mach 1·5. The unsteady flow is studied through solutions of the Reynolds-averaged Navier-Stokes equations with turbulence modelled by a two-equation k-ω model. The trailing edge (face) of a baseline rectangular cavity is modified using wedge and ramp shapes to investigate means for the suppression and attenuation of the self-sustained oscillation. Through modification of the shear layer impingement, both wedge and ramp are effective in reducing the level of oscillation. The time-averaged pressure (form) drag coefficient of the cavity is also reduced significantly. The main cause of the drag reduction is the elimination or reduction of the high pressure area near the downstream corner of the cavity due to the presence of a vortex. Two types of unsteady flow exist when a curved ramp is employed: ‘regular’ and ‘random’. The use of a h= 0·6D ramp generates a random type pressure fluctuation with lower rms pressure compared with the h= 0·2D and 0·4D ramps.

The paper examines the influence on optimal structural designs of changing the design criteria and concepts for an unmanned air-vehicle wing, for both single and twin-spar rib configurations. The results indicate that the influence of such factors as panel buckling, aeroelastic efficiency, the number of design variables and the number of ribs can be significant. It is also shown that the best design is given by the twin-spar layout.

The established control anticipation parameter longitudinal handling qualities criterion is based on the assumption that the short term dynamic response of the aeroplane is classical, or second-order-like. Modern fly-by-wire aircraft often have longitudinal short term dynamics which are not second-order-like and to which it is difficult to apply the criterion. This paper presents a proposed generic control anticipation parameter which is a modified version of the control anticipation parameter and which may be applicable to both unaugmented and augmented aircraft of all types. The appropriateness of the modified criterion was illustrated by designing a number of command and stability augmentation control laws, constrained to meet the criterion, for application to a medium weight fly-by-wire civil transport aircraft. The handling characteristics conferred by the control laws were assessed in a series of flight simulator trials, the results of which are briefly presented.

Effective operation of a large-scale supersonic intermittent blow-down windtunnel system requires suitable control of the air control valve to establish the desired pressure profile in the settling chamber and generate a corresponding supersonic air flow. In this paper, we establish a lumped parameter nonlinear time-varying mathematical model for blowdown-type windtunnels, based on the thermal-fluid mechanical balance principle. We apply the LQG/LTR procedure to achieve a robust controller design that diminishes the effects of unavoidable uncertainties and time-varying characteristics and obtains the desired experimental environment in the system. Simulation results show that this LQG/LTR based controller, with a carefully selected loop shape combining both anti-integrator windup and the time-delay compensation schemes, achieves satisfactory control performance for the entire windtunnel testing procedure.

The vorticity production by a single vortex generator jet in a turbulent boundary layer at high speed and zero pressure gradient was studied by analysing surface-flow patterns. The investigation involved a range of jet mass flow rates and skew angles while the freestream Mach number and jet pitch angle were held constant. A qualitative analysis of the skin friction patterns demonstrated the effective role of the skew angle as a bifurcation parameter. The vortex production is classified into three main regimes as the skew angle increases from zero (fully downstream) to 180° (fully upstream). Better understanding of the physical mechanism behind the transition from the first regime to the second is crucial in the design of the airjet vortex generator.