It has almost become a tradition in recent years to begin a paper on boundary layer by paying a tribute to the great Prandtl and his famous paper in which he introduced the conception of boundary layer into Fluid Dynamics.

The year 1954 is, however, not only memorable to mark the passing of fifty years since Prandtl's classical demonstration of the effect of boundary layer suction on the flow pattern around a cylinder; it is also memorable because in 1954 most convincing demonstrations of practical applications of boundary layer control for aircraft have taken place. I am referring, in particular, to the demonstrations with the Attinello flap in the United States which mark the introduction of one form of boundary layer control as an engineering and practical reality.

I wish first to express my deep appreciation for having been invited by the Council of the Royal Aeronautical Society to present a lecture on aeronautical research in Sweden. As the subject is a very broad one, it was necessary for me to consider rather thoroughly what would be expected from this paper and thus, which limitations in its scope should preferably be made.

Before the 1939-45 War it was possible to design new, successful aeroplanes mainly on the basis of experience from previous types in combination with generally available design information, such as aerofoil data. The success was, in fact, often more dependent on the skill of the designer than on the amount of research and detailed aerodynamic and structural testing done. After the advent of jet propulsion and transonic and supersonic speeds this situation changed radically. Nowadays a substantial amount of basic and applied research, as well as scientifically performed development work, is a necessity for any country, regardless of size, attempting to produce its own designs of efficient and safe aircraft.

Reginald J. Mitchell of Supermarines—a North Staffordshireman, like myself, and, in the words of Joe Smith, “ a practical engineer possessed of an abundance of plain, straightforward common sense; a man of drive and genius”—will go down to history as among the most inspired of those who had the good fortune to live and work in Aviation's pioneering days. During the short span of his active designing and engineering life—for the 16 years between 1920 and 1936—he produced 24 different aircraft types, so brilliantly and affectionately discussed by the great Joe Smith in his foundation Mitchell Memorial Lecture in January 1954. Mitchell's aircraft included, in the civil transport field, the “ Sea Eagle ” of 1923, which opened air services to the Channel Islands, the unique “Air Yacht” of 1929 and the very advanced 75,000 lb., 174 ft. span, six-engined, 40-passenger commercial flying boat of 1930 (Fig. 1), the contract for which was unfortunately cancelled as an economy measure in January 1932 after work was well advanced.

The structural problems introduced by the kinetic heating of high speed aircraft require a radical extension of what has hitherto been regarded as the normal domain of structural theory. Aerodynamics, for example, cannot be regarded as a self-contained subject which merely provides basic data for the structural worker. Certain aspects of aerodynamic theory, particularly the mode of heat generation, have to be considered simultaneously with the structural problem. Thermodynamics and metallurgy are still more closely integrated with structural theory. The laws of heat transfer, and the variation of material properties with temperature, are both essential factors in the structural analysis.

The successful development of the gas turbine for aircraft propulsion stimulated much thought, some serious and a great deal speculative, on the possibilities of even more advanced forms of propulsion. The ramjet and the rocket immediately sprang to mind. The former was a natural development of the turbo–jet. It could extend the useful field of the turbo–jet but the bounds of that extension could be clearly seen. On the other hand, the rocket was not restricted by the same fundamental limitations and its eventual, although still somewhat remote, exploitation in wider spheres could be prophesied with some confidence. Before the 1939—45 War, the stage of development of the rocket motor was comparable with that of the internal combustion engine a century ago. Pioneers like Tsiolkovski in Russia, Esnault–Pelterie in France, Oberth in Austria and Goddard in America had laid down the basic theory and made some small scale experiments in support, but the first major practical steps came from the Germans during the war.

Before the 1939-45 War, the stage of development of the rocket motor was comparable with that of the internal combustion engine a century ago. Pioneers like Tsiolkovski in Russia, Esnault-Pelterie in France, Oberth in Austria and Goddard in America had laid down the basic theory and made some small scale experiments in support, but the first major practical steps came from the Germans during the war.

Flight before the Wright brothers demonstrated their powered man–carrying flying machine was based on the philosophy of vehicles with high inherent stability combined with pilots whose only duty was to steer. This combination resulted in low controllability and poor manoeuvrability, with a strong response to the disturbances of rough air. The Wright brothers broke with the high–inherent–stability concept and combined inherently unstable aircraft with three–axis control operation by human pilots to achieve stable flight systems with good controllability and good manoeuvrability. This change from inherently stable to inherently unstable aircraft was the basic contribution made by the Wright brothers to start the age of flight.

In this paper, a picture of the state of flight control before the Wright brothers is built up from references to the literature. A similar picture is drawn for flight control developments after the Wright brothers, and the effect of their efforts on the progress of events is discussed. Plots with time as the independent variable and non–dimensional ordinates are used to illustrate the overall pattern of past developments in flight control and to indicate the course of future progress.

The problems which occur in defining the thrust of a jet engine and the internal drag of a ducted body are considered, and formal definitions and names are given for the concepts considered to be of importance.

My pleasure in accepting your invitation to lecture, which I treat as a great honour, has been somewhat overshadowed by doubt that I shall do justice to the occasion. This is but the second lecture to commemorate Captain Frank Barnwell. I am fully alive to the fact that the members of this Branch of the Society, many of whom were Captain Barnwell's personal friends, are very desirous of establishing, in these early lectures, a standard which is a worthy memorial.

Captain Barnwell was one of a small number—I suppose they can be counted on the fingers of two hands —who, by their courage and ability, made the barely flyable contraptions of 50 years ago into the aeroplanes we know today. The changes in aeronautical engineering have been so great that it is not easy to realise in 1955 the problems Barnwell and his colleagues faced in 1905, the year of the first Barnwell designs.

The True Balance of a man's worth cannot be struck by a knowledge, however full, of only one of his activities.

I do not propose to confine myself to Cayley's aeronautical activities in this paper, for that would be to do much less than justice to a man whose interests, when known and understood, can only add to the stature of a great Yorkshireman and a great Englishman, one, to quote William Cobbett, “of the resident native gentry, attached to the soil, known to every farmer and labourer from their childhood, frequently mixing with them in those pursuits where all artificial distinctions are lost, practising hospitality without ceremony, from habit and not on calculation.”

Sir Walter Raleigh, in his introduction to the History of the War in the Air (1914-1918), referred to Cayley as one who “amused his leisure with science.” Raleigh was not aware and, indeed, very few who know something of Cayley's aeronautical work are aware, of how active was the interest Cayley took in scientific and engineering matters during his long life. I hope in this paper to add something to Cayley's stature, great as it is, in this respect.

The main task of the aircraft accessory designer is to provide fully developed and type-tested equipment to meet the needs of the Aircraft Industry at the time when a new aircraft is at a stage in construction where accessories are to be fitted.

But he must do more than this, particularly with equipment for multi-engined aircraft. He must endeavour to set up and test a complete aircraft ancillary power system. This is particularly important for the electrical system, where two or more generators have to operate in parallel, successfully sharing the load on the system and providing over-voltage and other protection in such a manner that failure of the complete system does not result from failure of one engine, generator or its attendant equipment.

The whole process of designing an aero engine, from the original concept to the production of the first of the type, called a prototype, normally takes about two years.

The prototype design may originate from proposals put forward by the engine maker from specifications for military aircraft engines, issued in the United Kingdom by the Ministry of Supply, or from the Aircraft Industry.

It is not usual for engines to be designed specifically for civil aviation requirements. More often they are adaptations of military engines de-rated to increase their reliability, and to extend the overhaul period. With the growth of civil transport and the development of guided missiles, it is possible that this state of affairs may be reversed and engines for civil aircraft may become more important than those for Service use. At the present time, it is difficult to foresee a potential civil or private aircraft engine market that would justify the cost of designing and developing a small jet engine on that score alone.

The purpose of this paper is to attempt a broad review of some of the factors that influence the economic development of a country and to illustrate in general terms the importance and the application of airborne survey techniques, as a means of collecting the information on which any sound development must be based.

The industrial and agricultural revolution that is now taking place on a world-wide scale demands a completely new approach to the problem of economic development. When economic development was slow and confined to small areas it was sufficient perhaps to base that development on limited information. Today, however, the pace is quickening every year, but the speed with which we are obtaining the information, on which such development must be based, is lagging behind.

Why is the present position different from any other epoch in world history? The main cause is the industrial revolution, which has produced rapid means of communication, by air and by radio. The Twentieth Century now lives literally as neighbour to the Stone Age.

As technical progress has improved the airborne performance of aircraft, so the difficulties associated with their take-off and landing have increased.

The grass airfields which were still commonplace at the end of the Second World War have now developed into complex arrangements of concrete runways of up to three kilometres (two miles) long, taxiways, dispersal areas, and so on. The main disadvantages of these large airfields, both for military and for civil aviation, soon become obvious: —

1. (i) The enormous expenditure in either case; for military aviation this expenditure has to be approved, but it is at the expense of the production of actual aircraft—like Ugolin who ate his children so that they would not be fatherless;

   for civil aviation, the high cost of airfield construction has hampered the development of aviation in the remote areas where it would be of particular use in raising the standard of living.

2. (ii) The lack of flexibility of air forces operating from fixed bases, thus reducing their efficiency.

3. (iii) The increase in vulnerability as destructive weapons become more highly perfected.