Recent interest has been shown in stability problems in which the parameters in the relevant characteristic equations are not constant. For instance, the coefficients in the characteristic equation for the stability of flutter of an aeroplane's wings are functions of the speed of the aircraft. When the aircraft is accelerating or decelerating it is therefore necessary to consider whether the resulting variation of the coefficients is sufficiently rapid to invalidate a calculation of stability which is based on the assumption that the coefficients are constant. Similar stability problems arise in connection with guided missiles.

The concept of small stage efficiency is introduced when studying one-dimensional gas flow in nozzles in order to permit a closer approximation of real flow conditions than is possible from an isentropic analysis. It is more or less conventional to assume the flow conditions are adiabatic whenever the small stage efficiency is used. That is to say, small stage efficiency is generally considered in relation to flows contained within adiabatic boundaries, in which case it becomes a measure of the heat generated by internal frictional effects alone.

Numerical results are presented for two-dimensional vortex-aerofoil interaction using a grid-free discrete vortex method. The effects of the passing vortex on the surface pressure distribution and hence the aerodynamic force and moment of the aerofoil are examined in detail for a variety of interaction geometries. For some head-on interaction cases, vortex-induced local flow separation is also predicted on the aft part of the aerofoil surfaces. Extensive comparisons are made with other numerical results and the results from the Glasgow University BVI wind-tunnel test, which show good agreement.

The paper concerns a phenomenon which occurs in rows of closely spaced blades, as in an axial flow compressor, when the flow around the blades approaches the stalling condition. Patches of stalled flow can propagate along the blade row, thus causing cyclic variations in the lift on individual blades. Under certain conditions this cyclic loading can lead to large blade stresses, and ultimately to blade failure.

In some recent tests we have successfully used the smoke from smouldering paper to indicate the flow of air in the vortices above slender wings at speeds in the region of 200 f.p.s. Smokes of this kind are particularly suitable for the production of the large volume flows required because in certain conditions they do not lose density by condensation in long supply tubes.

I Consider it a great honour to be invited to deliver the First Lanchester Memorial Lecture, which, according to the instruction received from the Secretary of the Royal Aeronautical Society, should deal with Lanchester's personality and achievements. It is also a great pleasure for me to recall my personal contacts with this great man. On the other hand, I am not quite sure whether the decision of the Council, choosing me as the first Lanchester Lecturer, was really a wise one, since I am not in the best position to present a full biographical sketch of Lanchester. Somebody more familiar with Lanchester's automobile work, as, for example, Sir Harry Ricardo, would be more able to present a full picture of Lanchester's achievements. I must, therefore, restrict myself essentially to the treatment of Lanchester's contributions to the sciences of Aerodynamics, Flight Mechanics and Operational Analysis.

Kinetic heating, which is associated with supersonic flight, is probably the greatest challenge which has confronted the structural engineer, since the design and analysis of affected structures requires a radical extension of current practice. For example, the laws of heat transfer and the effects of high temperature on structural materials become important factors in structural analysis. To obtain a clear appreciation of the situation it is therefore necessary for the designers of the structure to become familiar with these factors, together with certain aspects of boundary layer theory.

During the past decade, the theory of optimal control associated with linear multivariable systems having state and output equations of the respective forms

and

has been applied extensively to the design of controllers for a variety of aerospace systems. Such applications of this theory have been mainly concerned with the design of controllers that generate optimal control vectors, ẑ, which minimise performance indices of the form.

where Q and R are positive-definite matrices.

A study of the process of mixing and wake development has varied applications in wide ranging fields like jet ejectors, wake signatures, base pressure control, combustors, flow over cut-outs, jet noise and jet interactions. In real flows the wake is usually divided into two zones namely, the near field and the far field. The near field is usually controlled by initial conditions which involve two back-to-back boundary layers separating from the trailing edge of a solid surface. In the far field the flow becomes fully developed and assumes self similarity. The properties of fully developed far field have been well established but little is known about the near field. This paper describes the application of an integral analysis to study the effects of initial conditions like velocity ratio, initial boundary layer thickness, compressibility and temperature ratio on the development of near field of the turbulent mixing layer between two compressible, non-isoenergetic streams at constant pressure. Results include velocity and temperature profiles and the location of jet boundary line in the mixing layer. These results show the gradual approach of the mixing layer to self-preservation.

The paper outlines the existing procedures employed in the field of defence procurement and mentions some new ones which may be used in the near future. It will serve as a reminder of the way in which major aircraft and weapon and equipment projects are conducted and will lay the foundations for what is hoped will be a fruitful discussion.

As this is a wide subject area with many specialised fields, a broad review from a systems viewpoint would appear to serve the purposes of this Symposium best. Also, such a review may help to show that the importance of range instrumentation in upper atmosphere research is rather more fundamental and widespread than generally appreciated.

With all transport vehicles a light structure weight is of prime importance. Light weight vehicles require less power to accelerate, less braking to stop, less power to climb hills. The power /weight ratio broadly determines the ability of a vehicle to get out of difficulties, avoid collision and, generally speaking, settles the vehicle's performance characteristics.

This is particularly true of the aeroplane where, with a third dimension of travel, the effect of gravity is present to a degree unknown to sea or land travel, even in mountainous countries.

Weight saving thus becomes of paramount importance in aircraft design and leads inevitably to the conclusion that nothing should be carried in the aeroplane to fulfil a service which can be satisfactorily and safely performed on the ground.

A further result, and one that most concerns us here, arises from this weight factor. In many trades a great deal of the technical execution of the work in detail is carried out in accordance with the superintendent's or foreman's knowledge and craftsmanship, and whether there is a little more—or less— material used is a matter for commercial considerations of cost, rather than one of necessity to save weight in order to fulfil performance.

The Sixth Louis Bleriot Lecture was given in London by General Guy du Merle on 19th March 1953 at the Institution of Mechanical Engineers, Storey's Gate, S.W.I. Mr. G. H. Dowty, F.R.Ae.S., President of the Society, presided and welcomed particularly M. Jules Jarry, President of the Association Francaise des Ingenieurs et Techniciens de l'Aeronautique, and members of A.F.I.T.A., who had come over from France for the occasion.

Introducing the Lecturer, the President outlined his career. After leaving school General du Merle went into the corps of aeronautical engineers, which was then of civil status but had since been militarised. He spent two years at the Ecole Nationale Supérieure de l'Aéronautique, graduating in 1932, and obtained his certificate as a pilot of military aircraft including seaplanes. For the next two years he served as an engineer pilot at the Centre d'Essais en Vol (Flight Testing Centre) testing prototype aeroplanes at Villacoublay, during which time he flew both French and foreign aircraft. He next became Engineer at the Technical Department of Aeronautics at the Air Ministry and then Director of the Department. While a professor at the Ecole Nationale Supérieure de I'Aéronautique he had published a book on the construction of aeroplanes, a copy of which was in the Library of the Society. Upon being attached to civil aviation at the Ministry of Public Works and Transport, he founded and directed for two years the National School of Civil Aviation at Orly. General du Merle was then appointed Director of Navigation and Air Transport at the same Ministry, and represented France at a number of international meetings on Civil Aviation. Appointed Ingénieur Général de l'Air, he had regained for a short time his original Ministry, which he now represented on the Interim Committee of E.D.C. He had been on missions to England a number of times since the end of the war, and in 1947 had flown several British aeroplanes, including the Sea Fury, the Meteor and the Vampire. He was a Fellow of the Royal Aeronautical Society, and was also an Officer of the Legion d'Honneur and held the Medaille de l'Aéronautique. General du Merle was at present Commandant des Ecoles et Stages at the Ministere des Travaux Publics et des Transports (Officer in charge of Schools and Courses).

Measurements have been made of laminar and transitional heat transfer rate distribution on a 15° semi-vertex angle, spherically blunted, cone at Mach numbers 8·6, 10·6 and 13·0. The laminar results are compared with theoretical predictions and good agreement is obtained with a modified form of the analysis due to Lees. Using a development of the correlation of pressure distributions previously obtained by the author, a new correlation of experimental and theoretical heat transfer results is suggested. The effect of nose bluntness on boundary layer transition has been observed both from flow visualisation and heat transfer results. It is suggested that the main factor causing nose bluntness to influence transition is the adverse pressure gradient which is induced.

The aim of this article is to describe a method of power utilisation in a man-powered oscillating wing machine and to suggest features of design, which it is hoped might be of practical value to the many man-powered flight enthusiasts wishing to engage in what might, perhaps, become a relatively cheap and exhilarating sport.

With considerable expenditure of time and resources, successful attempts at man-powered flight have been made in the not so distant past. These exercises, at or near the limits of man's physical endurance, have been rewarded with flights lasting but a short while. And it is believed that any improvement of results in the near future can be only marginal.