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).

The problem of symmetrically loaded circular plates of constant thickness is covered adequately in several of the standard textbooks on the strength of materials. Formulae are derived enabling the deflections and stresses to be readily calculated in any portion of the plate. The problem is complicated by the introduction of a variable thickness and by a variation of material properties due to a temperature gradient down the radius of the plate; conditions such as are encountered in gas turbine wheels, bearing support diaphragms and flexible disc couplings. Methods exist whereby the plate can be solved if the thickness is a simple function of the plate radius, but in practice this is not always so, the profile often being complicated by flanges and spigots.

In recent years, aerodynamics and thermodynamics have found common ground in the specialised field of gas dynamics. Developments in this subject have led to a much more complete and widespread knowledge of subsonic, sonic and supersonic flow of gases in the conventional type of convergent-divergent nozzle. When the back pressure is raised above the value against which the nozzle is designed to discharge, oblique and then normal shock waves are set up in the divergent cone at a position along the nozzle axis determined by the magnitude of that back pressure. The gas which has crossed the shock wave is subjected to a process of subsonic compression.

In this paper a theoretical investigation is made of the changes in pressure, temperature, density and Mach number which occur across a normal shock wave, when the position of the wave varies along the nozzle axis. The investigation illustrates the effect of change of medium, for which the relevant property is the ratio of specific heats. This ratio for certain polyatomic gases may approach unity (e.g. for Dichlorodifluoromethane CCl2F2, in gaseous form, γ=1·06), and for the inert monatomic gases γ= 1·667. The analysis is made non-dimensional by expressing such quantities as gas pressure, temperature, and density at any given position along the nozzle axis relative to the values of the particular parameter at entry to the convergent section.

In Mr. J. M. Stephenson's Technical Note, “ The Elimination of Wall Effects in Axial-Flow Compressor Stages,” in the April 1953 issue of the Journal, the author suggests that the blade rows of an axial flow compressor are so closely spaced as to ensure that the axial velocity profile is unchanged across the rows. Whether this statement is correct or not such an assumption regarding the axial velocity profile is a basic design condition and when made it will not leave any flexibility in the choice of the function f(r).

The following problem constitutes a minor delay in ultimate production, yet considerable time and effort and manpower are duplicated at present in finding a practical solution to what is really a repetition of Drawing Office calculations.

The problem is that drawings calling up various machined fittings often lack any reference to “practical” measurements by which the operator, the toolmaker and the Inspection Department may ”set-out ” and check the work concerned.

This note suggests a method, suitable for stressing purposes, of obtaining a fuselage air-load distribution, for a swept-back wing aircraft. The method is basically that given in Ref. 1. Mach number effect on the aerodynamic centre position is discussed and an approximate method of allowing for this is suggested. A numerical example is given.