By way of introduction to my paper and to place its subject matter in perspective, I would like to refer to a paper by A. Silverleaf, Deputy Director of NPL, Teddington, entitled A Review of Hovercraft Research in Britain (published in the JOURNAL, pp. 1019–1028, December 1968). Mr. Silverleaf presented a comprehensive review of research programmes at national establishments, in industry, and at universities. Although he did not specifically mention the College of Aeronautics by name, Mr. Silverleaf briefly commented on the research programme into external aerodynamics that is being conducted at the College.

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).

This paper is intended to provide a summary of the present role of the flight recorder in relation to the investigation of aircraft accidents and to refer briefly to its future role in this field, together with its potential for flight safety monitoring.

The paper deals principally with the philosophy of data recording for these purposes and with the general needs of the associated data recording, recovery and analysis systems. It also describes the predominant problems encountered up to the present time in the use of such systems for accident investigation purposes in the United Kingdom. The technical problems relating to system design, information recovery and analysis are, however, of a specialised nature and can only be referred to in brief terms within the scope of this paper.

An historical survey gives an opportunity to reflect on a few selected episodes which seem to have had a significant influence on shaping later events. I need not remind you that reflections on aircraft mostly having two-dimensional curvature with surface finish falling short of mirror standards, and not only is the image probably distorted but also the perspective depends very much on where the observer stands. Moreover, also, quite important objects can be thrown right out of vision.

The calculation of the response of an aircraft to atmospheric gust has two main purposes. These are, first, to make possible an assessment of the peculiarities of the response of a particular aircraft (e.g. the length of the discrete gust which produces maximum load), and secondly, to provide an estimate of the gust loads which the aircraft must be designed to withstand, in both the static and fatigue senses. (In this paper, however, the fatigue aspects are not considered.)

In ref. 1, an extension of the Kantorovich variational method of minimising a functional is discussed. The extension is based on an iterative technique wherein functions derived from the solution of sets of simultaneous ordinary differential equations are used again in cyclic order to obtain an improved solution. It is conjectured that if the iterative procedure is continued indefinitely, the functional will be close to its correct value, and so also will the associated function. The method given in ref. 1 is a generalisation of the iterative technique for minimising a double integral given by the writer in ref. 4, although in this work the iterations are carried out in the first approximation of the Kantorovich method and convergence is obtained in the usual manner of Kantorovich. Like ref. 4, ref. 1 uses the classical torsion problem of a rectangular bar as an illustrative example. Each shows that accurate Prst approximation solutions can be obtained and ref. 1 goes on to show that, for this particular problem, the derived functions are unique and are not dependent on the initial choice for part of the function.

Of the two main finite element approaches, the displacement method has progressed more rapidly than the force method in the area of element representation. Many authors have contributed to the displacement method with both static and dynamic stiffness matrices for beam elements, plane stress elements and plate bending elements. The plane stress and bending elements being rectangular, triangular or quadrilateral in form. A dynamic stiffness matrix consists of a static stiffness matrix and a mass matrix. In the force method, .static flexibility matrices have been developed for beam elements and plane stress elements. However, static flexibility matrices for plate bending elements have only recently been published (Kaufman and Hall, Morley, Robinson, Przemieniecki). For the past few years, the author has been investigating the rank force method for structural vibration analysis. In ref. 6 a dynamic flexibility matrix is presented for a beam element. This matrix consists of a static flexibility matrix and an inverse mass matrix. Ref. 5 contains the derivation of a dynamic flexibility matrix for a rectangular plate element in bending, twisting and shear. The author, in collaboration with Petyt, demonstrated how a dynamic stiffness and flexibility matrix can be extended to include material damping.

This brief survey endeavours to highlight the major points of the Edwards Report to provide background for the more detailed contributions and discussions to follow. It is perhaps worth repeating the terms of reference of the Committee:

“To enquire into the economic and financial situation and prospects of the British civil air transport industry and into the methods of regulating competition and of licensing currently employed; and to propose with due attention to other forms of transport in this country, what changes may be desirable to enable the industry to make its full contribution to the development of the economy and to the service and safety of the travelling public.“

I am delighted as a test pilot, to have been asked to talk to the Test Pilots’ Group on the subject of light aviation. Originally I was asked to talk about the design of homebuilt aircraft; but, since, leaving the Service and joining the Air Registration Board, to look after all aeroplanes weighing less than 6000 lb, it seems appropriate to take a look at a wider field at this time, without focusing on any specific class of light aircraft.

In the fourteenth Henson and Stringfellow lecture delivered to the Society earlier this year, Speechley compared the development of the helicopter with that of conventional fixed-wing aircraft. He pointed out that some ten years elapsed between Kittyhawk and the mass production of military aircraft which occurred during the First World War, and that there were a further two decades before the commercial breakthrough of the DC2/3 aircraft. Initial helicopter progress followed a similar pattern but the commercial breakthrough is still awaited more than twenty years after the beginning of large-scale military procurement.

The modern aero engine is one of the most sophisticated machines currently produced by man. Its design, manufacture and repair necessitate the use of the latest knowledge and techniques, and development in one form or another continues throughout its service life.

Despite this high technical content, the fundamental requirement of the industry is to run on a sound economic basis. Often, however, this objective is lost in the equally demanding requirements of flight safety, or meeting over optimistic dates and of keeping up with competition in a multiplicity of other ways.

Much has been written about the initial development of engines up to type approval. This paper proposes to go beyond that and to describe some of the problems which arise during manufacture and operation, to emphasise the frustration and fury of an operator who has to unload 100 passengers and find them hotel accommodation—at his expense—in some outlandish part of the world because of a leaking oil pipe, and to highlight the need for repair techniques which are economical and simple.

The side force produced by gas injection through a single port into the supersonic regime of a rocket nozzle is composed of the natural reaction of the fluid leaving the port and the force due to pressure fields set up within the nozzle by the interaction of the secondary and primary flows. The obstruction presented to the main flow by the entering secondary fluid produces a shock system originating from the vicinity of the injection port. The pitch and yaw of a rocket can be controlled by simultaneous secondary gas injection from two ports mutually at right angles. With two ports operating, the respective shock wave systems produced can interact and hence cause an alteration of the side forces which would be produced if the ports were operating independently.

The equations governing the flow in a boundary layer are a simplified form of the full Navier-Stokes equations; the simplification being based on the argument that within the boundary layer the velocity gradients normal to the solid surface are much larger than those parallel to the surface so long as the boundary-layer thickness is much smaller than (a) a representative streamwise length of the surface and (b) the principal radii of curvature of the surface.

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….

The fundamental mechanics of the helicopter involving a number of rotating components make the machine subject to vibration. The prime source of excitation is the main rotor and at the design stage of a new helicopter detailed consideration should be given to the level of forcing produced at the hub. Up to the present time, designers using sophisticated mathematical models have not been completely successful in predicting, for a complicated airframe, the vibratory response to this forcing.

The Edwards Report is the first comprehensive survey of British Civil Aviation for over thirty years, and it recognises this fact by supplying detailed examination of many aspects of the industry. In this review of the report selection will be made of what appears to be the salient policies of the report and around which the other recommendations follow.

Central to the report's recommendations is the view that controlled oligopoly, in which fares are fixed by a Licensing Authority, will lead to the provision of a more desirable air service than either monopoly operation of “uncontrolled” competition in which freedom of entry and fare fixing is allowed so long as basic safety requirements are satisfied.

A procedure has been developed by Moon for the determination of the total solar irradiance within the earth's atmosphere. The present note illustrates how transmission factors derived by Moon for the constituents of the atmosphere can be used with recent curves of spectral irradiance outside the earth's atmosphere to determine the solar heating at a point on or above the earth's surface at any given time. Special consideration is given to the variation in atmospheric water vapour content with altitude, season, and position on the globe since this is a parameter of some importance. The method described forms the basis of Engineering Sciences Data Item 69015.

As a necessary first step towards the large displacement analysis of the cooling tower structure by the finite element method, an account of the small displacement theory of the SABA family of elements has been given in the first part of the paper. It may be worth repeating the basic considerations which influenced the philosophy in the design of the element: for an economical large displacement analysis to be successful it is essential that the structure should be represented by as few displacement parameters as possible, consistent with an accurate description of the structural behaviour. The SABA element is an axi-symmetrical thin shell element which describes the displacement variation in the circumferential direction by a Fourier series, each term of which is associated with a polynomial for interpolation in the meridional direction. By the devise of interpolating the meridional geometry in the same way, no strain is induced in a rigid-body movement, thus achieving true equilibrium and avoiding serious error in a large displacement calculation. Results of the small displacement analysis by this element for various examples given in Part I agreed accurately with existing solutions by other methods.