This Paper was originally written at the request of L'Association Francaise des Ingenieurs et Techniciens de L'Aeronautique (AFITA) and was presented at a meeting in Paris on 30th April, 1946. The Service Technique of the French Air Force were also interested.

The Paper reproduced here represents the entire lecture, except for those parts which were concerned purely with the French picture.

The heading of this lecture is the “Development of Air Transport During the War” but because time is limited I have had to exclude any mention of the ferry organisation which was responsible for the delivery by air of many thousands of aircraft. The work has however been, described in “The Atlantic Bridge.” The period with which I propose to deal is the 21 months ending in September, 1946. In this short period, in response to the demands of war, the Transport services of the Royal Air Force flew rather more passenger miles than did British Civil Aviation in the preceding 21 years up to the same date, and carried in addition great quantities of freight and military stores. This volume of transport flying, packed into a few short months, gave rise to many problems but also afforded unique opportunities for testing out new ideas and new equipment. My purpose tonight is to give a brief account of what was accomplished, and against this background to examine some of the lessons which were learned and the ideas for the future to which they gave rise.

A few of the outstanding problems connected with the design of tailless aircraft are discussed. The paper does not set out to be in any way a comprehensive dissertation of the whole field of tailless design, as it was considered that it would be more useful to concentrate on some of the recent problems which are exercising the minds of designers at the present moment.

Since the problems discussed are those which are currently causing some degree of speculation, it follows that in the majority of cases only possible means of solution may be suggested and only tentative conclusions drawn.

A meeting of the Royal Aeronautical Society was held at the Institution of Civil Engineers, Great George Street, Westminster, on 11th December 1946, at which a paper, “ Lofting and Template Reproduction,” by Mr. S. P. Woodley, was read by Mr. L. G. Burnard. In the Chair, Sir John Buchanan, F.R.Ae.S.

In 3.2.1 it was indicated that ξi, ηi may be found from the appropriate co-factors of the secular equation and appear directly as functions of the geometric and elastic properties of the root cross-section. The method will be applied in 5.6.2 for the four-boom tube, in 5.7.3 for the n-boom tube, and in 5.8 for the trapezoidal tube with direct stress carrying top and bottom panels. This procedure is advantageous when it is desired to study the effect on ξ, η of varying particular parameters of the cross-section.

However, when in any case the h-functions have to be obtained, it is often more expedient to determine ξ, η by one of the following procedures.

In his article “The Expanding Domain of Aeroelasticity,” Professor Collar explains how, in the course of a few years, the subject of aeroelasticity has grown from a mere collection of problems of common interest to the aerodynamicist and the structural specialist to become a main branch of aeronautical engineering. Aeronautical engineers owe Professor Collar a debt of gratitude for defining in the clearest terms what aeroelasticity purports to be, and for removing the vagueness and uncertainty which so often permeates any new branch of science or engineering, especially when it is derived from long–established subjects, as aeroelasticity is from aerodynamics and theory of structures.

As is to be expected from one so distinguished in the aeroelastic field, Professor Collar writes especially from the standpoint of the aeroelastic specialist. Engineers with a different background, while accepting the broad principles which Professor Collar lays down, may see their applications and development in a different light.

A consideration of the factors suggesting that new types of flying instruments are becoming necessary.

To safeguard the aircraft and crew against the danger of excessive speed and normal acceleration loads, until recently it was considered sufficient to provide for the pilot an airspeed indicator and to fix in the aircraft a plate giving the maximum safe speeds permitted for diving, without and with external stores, flaps and undercarriage down and so on. In the case of Service aircraft these limitations are usually published in Pilot's Notes for the type. Based on design data these speeds are those at which, allowing suitable factors of safety, the stresses in the appropriate parts of the aircraft's structure are calculated to reach the maximum safe limits.

This paper is a study of the questions: (1) Are the simplified equations and design procedure in Limit Design that have been developed for application to structural steel construction, applicable without modification to light metal structures? (2) How do the properties of these metals which are different from those of steel affect the application of the theory? Do they offer any advantages? Any disadvantages? (3) What changes in traditional design procedure are warranted? What changes are imperative?

No claim is made to a complete solution of the design problem, since each particular structure involves a thousand and one details. Only the broad fundamental philosophy is discussed here. The discussion and conclusions are supplemented with a report of a number of experiments on a few extrusions of some of the more important alloys of magnesium and of aluminium.

In this paper an explanation is furnished as to why linear simultaneous equations arising in structural problems are, in certain circumstances, sensitive or “ill-conditioned,” and an indication is given concerning the physical significance of this sensitivity. Means are also discussed whereby difficulties of this kind may be overcome.

This paper was requested to deal with (1) the future relations between designers and production; (2) the special problems to be faced by the production people and the assistance to be expected from the designers; and (3) how such design problems as pressurisation, silencing and the fitment of turbine engines were being tackled.

These terms of reference are very broad and probably can only be touched upon in a general way. I, personally, have been engaged entirely on the design side for the past thirty years and therefore it might have been more fitting if a member of the production organisation had been asked to give this paper.

The part played by major structural strength tests in aeroplane design is well known. Without such tests the standard of safety for aircraft would soon decline and excess weight, as an insurance against structural failure, would become a general rule. Considerable time and effort are expended therefore in the early stages of each new design of aeroplane to check by actual test whether its strength meets requirements. It is clearly reasonable to devote some little further time and effort to the study of methods and technique for strength testing in general.

The title “Operational Flying” gives considerable latitude, although a title such as “Naval Air Operations” would be more descriptive. I propose to spend rather less than half my time talking about operations with which I was personally connected. One reason for this is that my experience of firstline flying did not extend beyond the end of 1941 and therefore can hardly be considered to be of topical interest.

After that I will say something on the subject of Naval air operations as a whole. I will also touch on such points as ship-based flying from the pilot's point of view; the way in which the carrier is fitted in as part of the fleet; the relative merits of ship– and shore-based aircraft in different circumstances; the so–called vulnerability of the carrier; and finally, a brief outline of the current types of aircraft in service and. of the capacity of a typical carrier from which they would operate.

During the past few years a new series of low drag aerofoils has been developed which represents a radical departure from earlier practice. The changes envisaged are much greater than those which accompanied the general change-over from the biplane to the monoplane, and give rise to many problems whose solution requires considerable theoretical and experimental work. An important feature of the new sections is the precision in design and manufacture which is essential for their success. This has given renewed interest to the investigation of many of the detailed problems of air flow and calls for parallel improvements in manufacturing technique so as to achieve the high standard of surface finish required.

The purpose of this paper is to give a brief account of the theoretical basis of the design and application of the modified profiles as aircraft wing sections. It deals with the design of aerofoils for the subsonic range only, or, to be more precise, for flight at speeds below the critical Mach Number at which shock waves are first formed. The critical value usually lies in the range 0.6 to 0.8, depending on the wing shape and incidence, as will be described in more detail later.

Some aspects of the determination of the strength of materials formed the subject of two meetings held jointly with the British Rheologists’ Club (President, Prof. E. N. da C. Andrade) and the Royal Aircraft Establishment in the Assembly Hall, Farnborough, on the 16th June, 1945, and with the Royal Aeronautical Society in the library at 4, Hamilton Place, on the 19th February, 1946, under the chairmanship of Sir Ben Lockspeiser.

At the Farnborough meeting three papers were read, namely, “The investigation of failures in wood by microscopical examination” by M. C. Pryor and A. Rayne; “The effect of duration of loading on the strength of brittle materials” by C. Gurney; and “Application of statistical methods to mechanical test results” by B. Chalmers and E. R. W. Jones. At the London meeting Prof. N. F. Mott of Bristol University spoke on the “Griffith theory of cracks in solids and recent developments of this theory, with application to brittle fracture in glass and in metals.”

The scope of this paper is necessarily restricted. A large aeroplane, within the new definition, has not yet flown in this country. This event, however, is not very far off and the preparatory work that makes it possible has brought to light many novel problems. In some cases these could be predicted with normal anticipation, whereas others have only emerged as analysis progressed. These latter are frequently good examples of the dangers of too facile extrapolation.

Some of the reasons for having large aeroplanes are examined and subsequently, the chief technical problems arising are described. These descriptions avoid mathematics, as in many cases this approach is extremely long and involved and merits individual publication.