It is a great honour to be asked to give the Barnwell Memorial Lecture. It is now nearly 29 years since Barnwell was killed test flying at the age of 57 an aeroplane which he designed and built himself. He was a man of many parts and a man for all seasons. It is a measure of the passing years that now there is a Barnwell Memorial Lecturer who did not enter aviation until three years after Barnwell's death and has never participated in the design of any aircraft. Yet Barnwell's ideas and actions have indirectly, anonymously and through others, had important effects on the life and work of myself and thousands of people like me. I did my operational flying in the last World War on Beaufighters, and in more recent years have been concerned with Britannias, both aircraft designed and built in Bristol by members of Barnwell's old team. It is curious to note that exactly 50 years ago Barnwell was sitting on a committee of the Royal Aeronautical Society charged with considering the future of the Society. We are still at it. At a meeting of the Future Activities Committee the other week, I wondered what Barnwell would have thought of the discussion and recalled Isaac Newton's remark that if we now see a little further it is by standing on the shoulders of giants.

The problem of a static two-dimensional hovercraft over a solid surface has been studied by many authors and the solutions show reasonable agreement with experiment; the main source of error appears to be the neglect of viscous effects in the simple theories. It was recently pointed out by Hogben that no comparable simple inviscid solution exists for hovercraft over water. The main difficulty with the over-water solution is that there is no obvious reason why water should not occupy part of the cushion and some extra condition would be needed to determine this depth of water h2.

In recent years, manufacturers of centrifugal blowers for ventilation systems have abandoned the traditional arrangement of radial vanes shown in Fig. 1(a) for the “backward-aerofoil” arrangement shown in Fig. 1(b), which is the same as a conventional centrifugal water pump. Unlike the older type, the aerofoil-type blower does not depend on “centrifugal force” to produce a pressure rise despite the misleading accounts given in some hydraulics textbooks (the circumferential component of the air velocity is zero at entry and small at exit) although it does depend on the increase in blade peripheral velocity from the entry to the exit (which explains the curious blade arrangement).

In recent years there has been considerable interest in the possibility of providing high speed aircraft with the capability of vertical or short take-off and landing (V/STOL). One method for achieving V/STOL is to use lifting engines or fans, the aerodynamic interference effects of which are not yet fully understood. Experimental work on this problem has been done by Jordinson, Otis, Vogler and research workers at the British Aircraft Cor-poration, but no satisfactory theoretical analysis is known. The object of this paper is to put forward a semi-empirical method for predicting the aerodynamic interference of an exhausting jet on a uniform mainstream flow past a wing.

In May 1966 under threat of USA withdrawal from the 1929 Warsaw Convention, over 30 of the world's leading international airlines agreed to increase the limit of their passenger legal liability from US $8300 (Warsaw) or US $16 600 (Hague) to US $75 000 (inclusive of legal costs) or $58 000 (plus costs) for passengers travelling to, from or via the USA. Today the number of participating airlines is over 90 and there are individual variations, eg (i) BEA has extended the new limits to all its Warsaw or Hague passengers; (ii) Lufthansa and other airlines have adopted the equivalent of a $58 000 limit for domestic passengers within Germany.

In the United Kingdom (including associated overseas territories) on 1st June 1967 the Hague Protocol came into force for the first time and the limit of liability for non-Convention (ie mainly domestic) carriage was raised to the equivalent of approximately £21 000 ($58 000).

The end of the first year of the new limits and the beginning of the new UK limits were marked by the Air Law Group of the Royal Aeronautical Society by an international discussion held at the Society on 1st June 1967. The Chair was taken by Sir William Hildred, CB, OBE, MA, and the principal speakers were: Dr. B. Cheng, University College, London; L. S. Kreindler, Trial Lawyer, New York; A. Goodfellow, Solicitor, London; and M. J. Lester, Secretary and Solicitor, BEA.

The aims of the Discussion were to:–(a) Review the present position nationally and internationally; (b) Discuss possible future developments from the viewpoint both of airlines and their passengers.

The stability of a compressed plate is examined, using the energy method, with transverse deflections defined by a function giving the exact shape, but never specified. By this means it is possible to make observations about the form of the plate buckling coefficient. This form is examined tor two cases of loading, and it is demonstrated that a close approximation to the complete curve linking the buckling coefficient with plate aspect ratio can be deduced. The method is applicable to single plates or thin walled members consisting of an assembly of plates, and enables families of curves connecting buckling coefficients with aspect ratios to be summarised in a single relationship.

The solution of a problem in plane elasticity can be associated with a minimum energy principle, involving the minimisation of a double integral subject to certain boundary conditions. In 1933, Kantorovich proposed a method which reduced this problem to that of finding the minimum of a single integral. He chose part of the solution a priori (in accordance with the character of the problem) which left only one undetermined function in one of the variables. This unknown function could then be found through the solution to an ordinary differential equation. He then constructed a second approximation by introducing two unknown functions which led to the solution of two simultaneous differential equations. Again the accuracy of the solution was dependent on the initial choice for part of the function; so also was the rate of convergence.

It has recently been suggested that the tracked hovercraft is a suitable means of high speed transportation. On some routes it may be necessary for the vehicle to pass through tunnels. The purpose of the present note is to determine the effects of steady tunnel operation, and in particular to find if the “piston effect” is likely to adversely affect the performance of the air cushion.

During the past two years, there has been a sharp acceleration to the interest which industry has displayed in the subject of management education. This can be attributed to these factors: —

• (a) A more widespread realisation of the gap developing between the UK and a number of foreign economies, as manifested by diverging rates of the major economic indicators.

• (b) The attainment of top-management responsibilities by a younger generation of managers, many of whom had been given some earlier training and who were more conscious of its value than the incumbents of the job from earlier generations.

• (c) The publication of the Franks, Robbins and (in the aerospace industry) the Plowden reports.

• (d) The impact of the Industrial Training Boards making it manifest, in terms of serious levies, that training was an economic necessity and therefore must be investigated thoroughly.

Notwithstanding the widespread awakening of interest, it is very belated and sets numerous problems. The problems are in two areas—scale and quality.

The Centennial Year is over, and the activities of the Society are now projecting towards the second century of its existence. A number of new Committees have been formed, notably the Activities Committee and the Management Studies Group Steering Committee, and it is possible that during the on-coming year one or more additions to the number of Groups will be made.

Hugh Gordon-Burge has stated with clarity and force two of the salient problems in air safety work—that of obtaining information on accidents and incidents and that of disseminating the useful results after investigation and analysis.

He has also asked a number of pertinent questions to which I will try to provide some answers. As a basis for further discussion I also offer some tentative solutions to certain of the problems he has identified.

The views expressed are entirely personal.

An investigation has been made into the stability of compressor blade flutter in separating flow in the presence of external perturbations. The fluttering blade is an example of a hysteretic system governed by a non-linear difference-differential equation for which an analytical approach is not possible and for which the authors originally proposed this new treatment. For design purposes a digital computer has been used to produce stability diagrams under specified conditions including blade torsion. The solution for the response is also available if required. The method involves forming the non-linear feedback analogue to the blade system and which has behaviour governed by the same equation as that studied. The stability is then studied on a digital computer in the presence of small external perturbations by means of a dual input describing function applied to the analogous feedback system with consideration given to the aerodynamic phase lag involved and initially small blade torsional motion.

Axi-symmetric buckling of a circular plate having different material properties in the radial and circumferential directions was analysed in ref. 1. A plate with constant thickness and subjected to a uniform edge compression was considered. The plate edge was assumed clamped or simply-supported. The analysis of ref. 1 is extended to include plates with thickness variation in the radial direction.

A simple expression is obtained for the lift induced upon a wing by the pressure field of the fin mounted upon the wing in supersonic flow. This expression holds for all fins with sharp edges provided that the wing trailing edge is normal to the free stream and that the Mach lines from the apex of the fin do not intersect the wing leading edge. If the fin has a blunt trailing edge the further restriction that the wing trailing edge is upstream of that of the fin is also required.

Results for the induced lift and pitching moment are presented for a delta fin with variations in size and position of the fin relative to the wing trailing edge.

The rapid growth of interest in fluid logic and control elements has refocused attention on the reattachment of two-dimensional jets to plane surfaces. Of particular interest is the size of the low-pressure bubble enclosed between the jet and the adjacent inclined plane, and the effect on this of fluid velocity and compressibility. Several full studies have been made of such flows, notably by Bourque and Newman, Sawyer and Olson, and the basic characteristics have been well established. Agreement has been reached that bubble length is independent of jet Reynolds number (above 104), but doubts remain as to the best method of measuring the bubble length and also as to the effect of compressibility on this measurement. In order to clear up some of these points for an investigation of compressible flow through control valves, some experimental tests have been carried out on the reattachment of air jets to a plane.

A family of alternative expressions is presented suitable for the representation of the lateral deflection of rectangular plate elements in bending. Such expressions are extensions of a simple polynomial representation assumed in earlier work. The new expressions are such that not all displacement continuity conditions are met completely but, nonetheless, a criterion ensuring convergence of numerical results to true stiffness levels is satisfied. Deflection and natural frequency estimates based on one expression of the proposed family demonstrate rapid convergence and high numerical accuracy.

During 1961 preliminary consideration was given by the Weapons Research Establishment to the possibility of measuring the structure of the upper atmosphere by pressure probes on sounding rockets. A similar technique had been used with success in the USA. It was proposed that velocity be measured and that an incidence meter be used to measure pitot and static pressures, from which atmospheric pressure and density could be calculated. There was available at the time comprehensive calibration information on hemispherical-headed incidence meters at Mach numbers below 3. Since the sounding rocket would be flying within the Mach number range 3 to 6 there was a need to extend the existing calibrations to higher Mach numbers. At first it seemed that the results of Baer would do this, but a closer examination showed that his results did not agree with the incidence meter calibrations.

This paper describes a preliminary investigation of the torsional stress concentration factors for circular shafts containing grooves determined using an analogue computer. The range covered by this analysis is for grooves which increase in depth from a minimum of 0·05 of the diameter of the shaft, with radii which vary from 0·5 to 0·05 of the diameter at the minimum section. Results are presented in the form of a data sheet, and a comparison is made with the approximate expression of Neuber. An investigation is also made of the modifications to the stress concentration factor if the flank is not perpendicular to the centre-line of the shaft.