A theoretical solution is given for the overall buckling and wrinkling of sandwich circular rings when subjected to a uniform radial pressure loading. The core is in the form of a honeycomb material, and the faces can be made from laminated fibre reinforced plastics, which exhibit coupling between bending and stretching. The elasticity equations for both the orthotropic core and faces are satisfied, and it is found that the problem is governed by four simultaneous differential equations for the displacements of the faces. A solution is obtained by assuming simple sine and cosine functions for these displacements. Minimum critical pressures are found numerically and results are given which show the dependence on face thickness, core thickness and mean radius. A procedure is suggested for finding approximate solutions for sandwich rings subjected to more general loading conditions.

The objective of the present paper is to examine how the mathematical modelling of the overall aircraft system, in order to calculate its flight dynamics, has had to change to meet the requirements set by the type of problem posed. Some of these requirements reflect an increasing complexity in the aerodynamic design of the aeroplane. Others, a desire to improve the accuracy of the solutions to new and sometimes old problems.

In addition the basic difficulties raised by the fact that, strictly speaking, the aerodynamic forces and moments depend on the past as well as the present history of the motion.

A comparison is made of the aerodynamic formulations constructed from the character of the dynamics with those deduced, on the basis of a number of assumptions, from an analysis, which starts by considering the true nature of the aerodynamic forces and moments. In mathematical terms this is expressed by describing them as functionals of all the state variables.

Classic theory of helicopter ground resonance studies the phenomenon on a planar model obtained by reducing the dynamic parameters of the full helicopter into the plane of rotation. In this paper the phenomenon is studied on a spatial helicopter model of six degrees of body freedom. It is found that in general there exist six regions of instability, whereas the planar theory of Coleman determines only one region. The theoretical results obtained here are verified by experiments conducted on a dynamic model of helicopter. In addition, this paper reviews all the existing analyses which have studied the problem.

The ‘inverse method’ proposed in 1936 by Duncan, Collar and Lyon for the calculation of flutter boundaries is re-stated in a form suited to modern methods of dynamical and numerical analysis and programmed for use on a home computer. The method is extended to provide information on sub- and supercritical eigenvalues. For a microcomputer with 32K RAM, flutter problems of orders up to 35 may be accurately solved.

A simplified kinetic theory of turbulence originally proposed by P. M. Chung has been modified and applied to the problem of non-uniform grid turbulence with no velocity gradients. Preliminary comparison to the experimental results of Gilbert shows good qualitative agreement. The theory contends that shear stresses induced by local drift velocities maintain the anisotropic nature of the turbulent profiles. Both theory and experiment indicate that the integral length scale is comparatively uniform across the flow.

The flow before and after the partial impingement of a jet on a half plane has been studied. From the extensive mean velocity and turbulence intensity measurements the three basic flow regimes of the main jet flow, the flow over the flat plate and the redirected flow on the flat plate surface have been isolated. The inherited characteristics and axisymmetry of the upstream jet flow and their extent downstream of the flat plate, have also been established. The effect of the leading edge on the flow over the flat plate and the effect of friction on the surface on the redirected flow have also been studied.

In this presentation I will review the advances in manufacturing technology applied to the manufacture of large civil aero engines, but first I think we ought to look back and put these advances into some sort of historical perspective.

Traditionally the level of automation in civil aero engine manufacture has been relatively low. However, the level of technology in the component and that applied to the individual manufacturing operations has been very high.

Automation, from the start of the Industrial Revolution has been directed to the mass production of high volumes of relatively simple stable design components using conventional materials and production processes.

Ghosh's large-deflection hypersonic similitude and piston theory for plane flows have been extended to axisymmetric flows: a new piston motion in conico-annular space as an extension to Sedov's axisymmetric piston has been proposed and a set of ordinary differential equation for 1-D unsteady motion obtained. Wedge and cone flow solutions are obtained without the constant-density assumption of the earlier theory; the pressure ratio is expressed as a closed form function of the similarity parameter whereas the previous constant density theory gave an iterative procedure. The present theory unifies small disturbance theory and constant density theory.

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.

In 1945, the world's first turboprop-powered aircraft took off. It was a converted Gloster Meteor fighter aircraft, powered by two turbopropeller derivative engines based upon the Derwent 2 jet engine (Figs. 1 and 2).

By 1953 the world's first turbopropeller-powered airliner entered service. It was the Vickers Viscount powered by four Rolls-Royce Dart engines (Figs. 3 and 4).

To date, 7125 Darts have been sold and by the end of 1982 they had accumulated more than 100 million hours in service. The case for the turboprop as a powerplant for the commuter aircraft continues as strong as ever it was, but the Dart must be replaced by a low cost more fuel-efficient engine. Rolls-Royce plans for this are outlined.

With the present emphasis on fuel efficiency, a case is emerging for a 90-100-seat twin turboprop-powered super commuter — a market which Rolls-Royce intends to enter. Current estimates for a service date for such an aircraft place it in the region of 1992 to 1995.

Boundary layer equations are derived for viscous high-Reynolds number flow along streamwise concave corners using a simple non-orthogonal Cartesian co-ordinate system. The equations are solved numerically for corner angles of 30°, 60°, 90°, 120° and 150°, with emphasis given to the cross-flow velocity and streamwise vorticity fields. The results are discussed in the context of the inherent instability of this boundary layer at high Reynolds numbers.

The interaction of an incident oblique shock wave with the turbulent boundary layer with suction is investigated. Wall streamline and schlieren photograph visualisations as well as the pressure measurements on the wall are made. Boundary layer surveys with pressure probes and hot-wire probes are also done. The suction downstream of the interaction almost nullifies the shock reflection while the higher suction up and downstream of the interaction results in a reflection similar to that in inviscid flow.

This short note is intended as a measure of thanks to Alec Young for his encouragement and supervision of the author's PhD studies.

International air transport is a vital industry, integral to world trade, commerce and tourism. This industry has contributed substantially not only to worldwide economic growth, but also to political and sociological progress. However, in recent years the industry has fallen into chaos, to the point that many airlines find themselves either subject to unstable situations, or threatened by bankruptcies, or, in the case of state-owned airlines, in need of financial support from their governments. Competitive behaviour sometimes occurs on an under-the-table basis, interline co-operation has been deteriorating, and a clear international policy whose guidelines are accepted by everyone in the industry is absent. If the international airline industry is to continue to play a vital and dynamic role in contributing to the progress and prosperity of so many nations, then it is essential to adopt and implement policies aimed at eliminating the chaos in the industry, facilitating its healthy growth and stability, and developing international collaboration for the common good.

The flow from a high aspect ratio rectangular nozzle has been studied, so as to provide data to aid prediction of the effectiveness of this type of jet flow for acoustic shielding. Flow parameters investigated in both stationary and parallel, coflowing, airstreams, include axial centre-line velocity decay, jet width growth and velocity profile similarity. The existence of significant velocity peaks towards the edge of the jet in the plane of the major axis was observed, together with an unexpected interaction on this jet flow by an adjacent circular and subsonic jet.

Vorticity panel methods are applied to solve the interacting flow between an outer stream and a two-dimensional jet exhausting into that stream; both are assumed to be at low speed. The cases include a jet emerging from a thick afterbody and an inclined jet. The work is intended as a prelude to obtaining initial values for calculating the mixing of a jet with an outer stream.

We consider the effects of atmospheric disturbances, such as wind, shears, turbulence and wakes, on the aerodynamics of aircraft, in order (§1) to quantify the phenomena in question, and provide a basis for future application to problems of performance and stability. The present method of description of the effects of non-uniformity and unsteadiness of the incident flow on aircraft aerodynamics, is presented in some detail for a head- or tailwind sheared vertically (§2), and its extension to all three components of velocity and six shear derivatives is outlined (§11). The starting point (§3) is the relative life change due to a uniform or sheared wind; in the latter case we introduce (§6) a dimensionless shear number S, which plays with regard to vorticity, a role similar (§6) to the Mach and Reynolds numbers respectively in connection with compressibility and viscosity. The aerodynamics of a body or aerofoil in an incident stream containing vorticity, is specified (§7) by a shear coefficient Cs, playing a role similar to the lift, drag and moment coefficients for aerodynamic forces and torques. The present theory is consistent with the formulas of theoretical aerodynamics, the results of wind tunnel tests and observation of atmospheric disturbances involving shear flows. The use of the concepts of shear number S and shear coefficient Cs allows the calculation (§10) of the uniform wind equivalent to a given shear, ie, the wind velocity which would cause the same lift change as the shear. This equivalent wind may be useful in the calculation of the aerodynamic effects of sheared flows, eg, forebody vortices on a wing, wing in a propeller slipstream, tailplane in a wing’s wake, an aircraft landing, behind another, or flight through storms or microbursts.

Time-dependent aerodynamics is primarily concerned with the pressure distributions developed by moving control surfaces, such as the oscillation of a trailing-edge flap, the rapid extension of a spoiler, or the pitching of a canard.

Some recent experiments in time-dependent aerodynamics are reviewed. These include wind tunnel dynamic interference and its attenuation, the aerodynamics of an oscillating trailing-edge flap, the reduction of response to turbulence by active control, the aerodynamic characteristics of rapidly moving spoilers, and the time-dependent aerodynamic characteristics of supercritical wings.

The paper concludes with a discussion of aeroelastic problems at subsonic and transonic speeds and with some buffeting measurements in a cryogenic wind tunnel.

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.

Experimental results obtained in jets from notched nozzles in a co-flowing free stream are presented. It is confirmed that even at low jet speeds the notches produce trailing vortices and it is found that the effect on the free stream on the vortices is surprisingly small.

A powerful mechanism for the generation of secondary flow, which does not rely on viscous or turbulent stress, is lateral skewing of a shear layer such as that encountered by the body boundary layer in a wing/body junction. For a given entry shear, the characteristics of the secondary flow (a horse-shoe vortex) will depend on the wing nose shape. The effects of three wing nose shapes on the size, position and strength of the horse-shoe vortex have been studied in low-speed flow. As expected, the vortex size and strength increased with nose bluntness; quantitative data describing this effect are presented in this paper. The results include contours of streamwise velocity and secondary velocity plots from which vorticity contours and a non-dimensional circulation were derived. The results should be of use in wing design where this secondary flow needs to be controlled.