More than sixty years ago Theodore von Kármán showed in a paper entitled Über die Turbulenzreibung verschiedener Flüssigkeiten (On turbulent friction of various fluids) how the pressure drop of various fluid flows through pipes could be correlated in a single curve. The correlation parameter he used is now known as Reynolds number. It had been named after Osborne Reynolds only three years earlier in 1908 by A. Sommerfeld, shordy after he had left Aachen, in a note at the Internationaler Mathematiker Kongress in Rome. Sommerfeld had recognised the importance of Reynolds' similarity law and was deeply persuaded by his experimental and theoretical work.

It is not only a great honour but also a great pleasure to have been asked to deliver this Sixty-Third Wright Brothers Lecture to the Royal Aeronautical Society. My own associations with the Society and its members have almost always been highly edifying, stimulating and productive in both the personal and professional spheres. I believe that the relationships between our two nations which I have had the opportunity to observe from the government, industrial and scientific standpoints have greatly enhanced the qualities of our institutions and the extent of our progress in aeronautics as in many other areas. We have often been competitive, sometimes fiercely so, but almost never in a destructive way. I still remember from my youth the vicarious thrills of the editorial battles of the 1930s between The Aeroplane and Aero Digest over the merits of British and American air transports and the genuine delight I experienced when I actually met C. G. Grey, Editor of The Aeroplane in that era, at a Society garden party years later. The challenge of worthy adversaries, the hard but fair rules of engagement, and the sportsman’s appreciation of the game well played, in victory or defeat, are as potent sources for excellence in science, technology, business and the professions as they are in contests of skill and daring.

The discussion generated by the Roskill Commission and by airport planning inquiries in different parts of the United Kingdom has increasingly emphasised that airports are merely a sub-system within a larger system. They cannot be planned and developed except with reference to the other elements that make up that system. There are essentially four critical elements:

1. (i) The passengers or goods requiring transport by air.

2. (ii) The physical, social and economic environment around the airport.

3. (iii) The airport itself.

4. (iv) The aircraft and the airlines which operate them.

The total system is concerned with enabling passengers and freight to travel by air in order to reach a different environment.

This paper attempts a view of the development of civil aviation in a rather broad and fundamental way, deliberately avoiding any detailed discussion of the many technical aspects of this large and complex industry.

Anyone who is associated in any way with the design and production of aircraft and with the administration and operation of airlines and airports will be only too well aware of the immensity of the technological and organisational effort involved. And looking back over the past 50 years, the development of civil aviation into a major world industry can be viewed, rightly, as a major technological achievement. However, any technological development and the successful evolution of any transport system or industry must be initiated and sustained by some form of social demand. Frequently the demand is difficult or impossible to identify, indeed the idea of a demand may be less useful than the idea of a welcoming response to supply: technical advance frequentiy seems to generate a new market rather than to satisfy an existing one. Nevertheless aviation has during its development passed through a number of phases and been subject to shifts of objective, sometimes gradual, sometimes very rapid, reflecting changes in the response of individuals, companies, nations, and now perhaps even of the world community at large. These changes in demand may be expressed as changes in priorities and we have tried, in Fig. 1, to give some indication of how the balance of demand appears to have shifted as aviation (in this case, both civil and military aviation) jhas progressed from its early status as a sporting pastime to its present position as a world-wide transport system.

This paper describes the design and development of the HS. 748 short/medium range turboprop aircraft. At the RAeS Convention on “Economical Factors in Aviation” held on the 13th/14th May 1970, Mr. Knight of BAC stated, when analysing post-war British civil aircraft projects, that “there are really only three types that can be called true commercial aircraft successes. They are the Vickers Viscount, the HS.748 and the BAC One-Eleven”. This paper discusses the philosophy behind the original design of the aircraft, its development to date, its in-service history and also gives examples of the many different projects based on the HS.748 which have been and which are still being considered. The aircraft is described as the HS.748 throughout this lecture as this is its current designation. It should not be forgotten, however, that this aircraft was designed and flown as the Avro 748 for at least three years.

In its initial version, the L-1011 TriStar (the Dash One) is designed for short/medium-haul routes—typically carrying 250/270 mixed-class passengers distances of from 300 to more than 3000 nm. A general arrangement is shown in Fig. 1. As indicated in Fig. 2, the L-1011-1 payload/range curve is placed between those of the DC-8-61 and the Boeing 747. It should be noted that both these aircraft are designed for long ranges and are suited only for operation from major airports. On the other hand, the TriStar has airport performance, in terms of field length, comparable to that of the much smaller short-range types, typified by the Boeing 727. This, in broad terms, illustrates the primary design objective of the Dash One. The dashed line on Fig. 2 shows the payload/range curve of the L-1011-2 which will, of course, have an airport performance at the heavier gross weights more in keeping with long-haul requirements.

The Remotely Piloted Vehicle, or RPV, is here as a viable element in the arsenal of aerospace power. The astute student of air power, the United States Air Force planner, and we in the research and development community are well aware of the current and potential applications of the RPV in fulfilling aerospace missions.

The general subject of this session is the effect of shortages of raw materials on the development of aircraft. It is most important at the outset to distinguish between two related but essentially different situations.

• (a) A genuine shortage in which the material in question just cannot be obtained in anything approaching adequate quantities.

• (b) A situation in which, for some reason or other (possibly associated with some moderate limitation in supply), the price of the material increases rapidly.

In either case there is a pressure to reduce the amount of the material that is used, but in the first case one must do so almost regardless of cost or operational effects, while in the second case purely economic and competitive considerations apply. This is most clearly illustrated in the case of fuel—I shall show later in this paper that we could hope to achieve very large savings in fuel usage— perhaps as high as 40%—in a new generation of aircraft, but some of this saving can only come at the cost of reduced speed, reduced operational flexibility or increased complexity. The major decision that must be made is how far along this line should we go—nevertheless, if we are to have the freedom to make that decision we must continue to pursue with all energy the R & D necessary to achieve the maximum improvements.

The designer of a strike/fighter wing must bear in mind the many manoeuvres which the aircraft must perform. It is not sufficient to consider a single altitude cruise design point. Instead one must aim for:

(a) An economic altitude cruise, i.e. a moderately high Mach number and lift coefficient without drag rise.

(b) A sea level dash capability, i.e. a high subsonic Mach number and a low lift coefficient without drag rise.

(c) Good manoeuvrability at intermediate and high subsonic Mach numbers, requiring high maximum usable lift coefficients.

(d) Good field performance with very high lift coefficients in both take-off and landing configurations.

(e) Some supersonic capability.

Such a wide range of performance inevitably leads to some incompatability in the design. The high speed requirements are necessarily in conflict with those at low speed and similarly there is an inconsistency between the needs for altitude cruise and sea level dash. Reference 1 develops a design procedure based on fixed geometry sections, which attempts to satisfy all the design requirements in a reasonable manner. This paper is restricted to consideration of a method in which flap deflections may be incorporated into the design conditions so that the general performance can be improved without seriously degrading any of the individual requirements.

In 1972 civil sales formed some 30% of the US aerospace industry. Although in 1973 there was a swing back to defence products, civil sales retain an important position. Not surprisingly, aerospace industries without sizeable civil projects on hand, such as Britain's and Canada's, are looking with concern at their future prospects.

Such increasing dependence brings its own problems, for civil sales have been characterised by large fluctuations in the past. Predictions have often been wrong and costly, yet accuracy is a prerequisite of the industry's steady development. The heavy research and development and expenditure involved in a major civil programme necessitates a forecasting horizon of up to a decade.

Today we speak of the quality of life and the need to improve the quality of the environment. The removal of all kinds of pollution from our environment is a laudable aim and for some types of pollution positive action and an awareness of the problem can make improvements with a minimum of cost. However, in the case of most forms of pollution, and this includes noise, improvement in the quality of the environment can only proceed at a price. Thus there is considerable need for phased reductions in pollution and future planning with imposed realistic targets is paramount. In this region of social planning the problem of cost benefit analysis cannot always be applied and pressures are exerted to directing funds for economic gains and combating other pressures in national and international life in directions which lead away from pollution control. Nevertheless improvements to the environment dependent on the supply of finance can only be achieved, all other things being equal, when the economic state of a country is stable and attention of governments is directed with a willingness to achieve what at first sight is a downright impossibility.

Despite it being 19 years since Major Halford died, his influence is still felt at Rolls-Royce Small Engine Division, (formerly the de Havilland Engine Co Ltd) which indicates the stature of the man. One way that his influence is felt is that we still have some 3000 Gipsy engines in service. Considering that the first were delivered in 1926 and production stopped in 1964, he certainly had hit upon a good formula. As Mr. Perkins said at the last Halford Lecture, Halford was really as keen on doing the biggest engine in the world as on the smallest, so we cannot claim to be following a trail blazed in that direction. He was, however, very keen on the demonstration method of launching engines, and was good at getting something together very quickly to prove if he was on the right track and to “cut the cackle”.