It is a signal honour to be invited to give this particular lecture; for me personally, it is especially significant, since for a brief period, 12 months in 1937/38, I held at A&AEE, then based at Martlesham Heath, the equivalent of the post originally held by Tizard in 1916/17, when A&AEE was first formed. At an earlier period, 1926/29, I had been on the staff of A&AEE as a Technical Officer, one of the most enjoyable and fruitful periods of my career. Hence it gives me special pleasure to be here this evening, and a great sense of fulfilment.

Sir Henry Tizard was not only a great man, a great man of science, an inspired leader; he was also a great patriot. He spent himself in the service of the country he loved. His anxiety, always, was to see this country forge ahead, to realise her leadership in research and so stride ahead in industry.

The history of the seaplane is almost as old as flying itself, dating back to man-carrying Box Kites only two years after the Wright brothers memorable flight at Kittyhawk.

The First World War greatly increased the pace of development, which continued to its peak just before the Second World War, when the flying boat became a mainspring in the opening of routes to the Empire. During the Second World War seaplanes played a major part in the Allied war“* effort but decline was already evident, and increased during the early post-war years.

The relative numbers of landplanes and seaplanes used by one principal carrier are shown on Fig. 1, which indicates the rise and fall of the popularity of the seaplane passenger aircraft relative to other aircraft. This paper attempts to analyse the seaplane's virtues and drawbacks, reviews its past and attempts to anticipate its future. The problems and characteristics of the seaplane base are also examined together with some past solutions.

For aviation to become commercially usable and reliable, in addition to the development of aerodynamics, of reliable structures and reliable engines, there had to be the development of instruments, communications, and navigational aids. Suppose, for example, that today one could not fly through cloud, or at night, then nothing remotely resembling a regular service would be possible. Flying would still be a sport.

To illustrate what I mean I shall quote the example of another innovation with quite different properties in this respect. The first railway was immediately commercial and usable without any aids. It can be seen at once that the train running along rails is constrained compared with aircraft. It is obvious that the navigation problem here is very simple, and that there is not really a problem of control or stability—the first railway trains did not even have brakes. The mechanical skill of operating and maintaining the new device had to be learned; but very little else.

The general adoption of the International System of Units (SI) in engineering as well as in science makes this the time to relinquish the slug, an engineering unit of mass. Seldom has a convenient unit proved so contentious. This note sets out salient points in the controversy, and indicates basic issues which could scarcely have been appreciated universally at the time.

In essence the slug is the unit of mass that goes with the pound force or the pound weight, just as the poundal is the force unit that goes with the pound-mass. There has, however, been a great deal of argument as to whether it is a true derived unit or simply a fundamental unit in disguise, and about how to realise it in practice: in particular, if unit force is defined or established by reference to the gravitational force on the pound-mass, there arises immediately the question of the appropriate value to use for g, i.e. should it toe the local value, the value at a specified place, or some other agreed standard acceleration?

The first research carried out in France relating to air cushions was effected in 1957 by the Bertin Company. The phenomenon was first observed during thrust measurements on inward directed annular jet silencers (Fig. 1), in which the effects of air inlets were being studied. Thrust was measured by the weighing of a plate located in front of the nozzle; when the secondary air inlets were closed, the scheme was in fact the one of the peripheral jet air cushion and the thrust read on the dynamometer was found to be much greater than the theoretical jet thrust (Fig. 2).

It should be noted that this work was an extension of research carried out by SNECMA concerning striction, that is to say the control of the exit area of the engine nozzle by means of an inward directed peripheral fluid curtain the purpose of which was to increase the pressure inside the exhaust pipe which is the characteristic of annular jet air cushions (Fig. 3).

Classical gas dynamics is by definition the dynamics of gases that are in local thermodynamic equilibrium everywhere in the flow field so that their thermodynamic behaviour is completely specified by two independent variables of state, for example by pressure p and density p. The fundamental assumption of local thermodynamic equilibrium is not valid in many flow situations of practical importance, and this fact has given rise to a revision and generalisation of classical gas dynamics. This generalisation is usually called “relaxation gas dynamics”. Ten years ago J. Ackeret mentioned this subject briefly at the end of the Daniel and Florence Guggenheim Memorial Lecture on The Role of Entropy in the Aerospace Sciences. He gave that lecture at the 2nd International Congress of the Aeronautical Sciences in Zürich (12th September 1960) and he said on that occcasion: “Non-equilibrium states are of growing importance, for strictly speaking, exact (thermodynamic) equilibrium occurs only relatively seldom in gas dynamics. However, a rational theory of nonequilibrium states must necessarily be extremely complicated….

One of the best known results in finite wing theory, which is quoted in aerodynamic text books, states that the distance between two rolled up vortices behind a wing with an elliptic spanwise load distribution is sπ/2, where s is the wing semi-span. Within the framework of linear wing theory this result is correct. But it is of interest to enquire how this result is affected when the standard linear model becomes less valid, for example, at higher wing lift coefficients.

In this note, it is assumed that a continuous trailing vortex sheet rolls up into two discrete vortices. These two discrete vortices are assumed to have cores of finite radius; inside the cores the flow is taken to be solid body rotation, while the flow outside the cores is the standard irrotational vortex field. It is assumed that this rolling up process takes place far downstream of the finite wing which generates the trailing vorticity.

The elementary beam theory for shell structures yields the exact solution for normal and shear stress, if the three following conditions are fulfilled:

• (a) the shell must be prismatic;

• (b) the cross section must not deform in its plane;

• (c) the centres of rotation of the different cross sections must form an axis of rotation parallel to the longitudinal axis of the beam.

A Fast and efficient method has been developed to obtain the equilibrium composition of a flame at a given temperature, pressure and mixture strength. The Newton-Raphson iteration technique enables one to solve a set of simultaneous non-linear equations and in the present problem these are the equations relating the equilibrium partial pressures and equilibrium constants for the particular reaction and the conservation of atomic species in reactants and products. A trial solution is used to check the energy balance for the flame at the assumed temperature. The temperature is then suitably altered and the whole procedure is repeated till a reasonable agreement is obtained.

A “light wire” is one for which the integrated wire weight and tangential fluid friction forces are much smaller than the weight of the load which it supports, so that only the aerodynamic force acting normal to the wire need be considered. The equations for this simplified model were first formulated by Glauert, and have been further studied by Bryant et al and Neumark, among others. Ref. 4 contains a comprehensive list of references.

In this note Glauert's equations are used to obtain numerical results for the wire shape, a wire shape integral which is of interest for trailing wire antennas, and the steady state aerodynamic forces which act upon the aircraft. Computer solutions taking cable weight into account have indicated that the results for a weightless cable are realistic for many cases.

In an investigation, on the characteristics of the wake from slender cone-cylinders at large angles of attack, the strength and position of the vortices in the wake were determined for a large range of flow conditions. Two types of experiments were conducted, namely schlieren studies and wake traverses.

Schlieren photographs (such as Fig. 1) clearly reveal straight parallel vortex lines in the wake for subcritical values of the cross-flow Reynolds number component and for cross-flow components of the free stream Mach number up to at least 1·4. In ref. 1 numerous such schlieren photographs were analysed using the impulse flow analogy (refs. 2 and 3 for example). According to the analogy the progressive development of the wake along the body when viewed in cross-flow planes is similar to the growth with time of the flow behind a two-dimensional cylinder started impulsively from rest with the same cross-flow conditions.

During the past decade we have seen many notable achievements in aviation by Russian scientists, engineers and technicians. The first man in space, the first supersonic air liner, and the rapid growth of Aeroflot are but three of their more prominent successes.

In a rather less spectacular manner, the Russians have developed a very powerful helicopter industry and it is probably correct to say that no other country in the world has utilised the helicopter so extensively on such a wide variety of uses as have the Russians.

In this lecture, I will endeavour to briefly trace out the historical development of the helicopter in Russia and to review some of the current types in service.