To anyone who knew Barnwell, however little, it is a great honour and pleasure to be invited to give this lecture as a tribute to his memory. I was too young and too remote to have known him well, but he was the first leading aeroplane designer that I ever met. Some older members of our Society will recall the aeroplane known as the Bristol Bagshot; and a few will remember that in its early flights it was found to suffer from an unexpected, and at that time new, form of control trouble. This occurred shortly after I had started work in the old Airworthiness Department at Farnborough, and the investigation of this new trouble, later to become known as “ Reversal of Aileron Control,” was put upon the new recruit. As a result I came to know Russell, as lively a young man at Bristol then as now, and was taken by him to see Barnwell. I was struck then, as afterwards, that here was a designer of insight and great kindliness who had learnt to combine engineering with the humanities to an unusual degree; and, as I realised afterwards, he had also learnt how to encourage and get the best out of the young men around him. And so I, like so many others, came to admire him.

It is necessary to start this paper with a disclaimer. Neither the author nor his firm have been concerned with the development of Drone aircraft for more than a few years. Others in the field have more, certainly longer, experience; the choice of the present author is probably because he has been associated with the development of the most ambitious target aircraft so far produced in Britain—the Canberra Mk. 10.

The early history of work on automatic flight was discussed by Dr. G. W. H. Gardner in the 46th Wilbur Wright Memorial Lecture*. Credit is due to the Royal Aircraft Establishment for the development of more modern Drones and associated equipment, and indeed, of the whole control system which is now used for Aberporth and in Australia. Much credit is also due to the Australian authorities for the working up of the target service which they now provide at Woomera and for the development of the Jindivik target. The Fairey Aviation Company Ltd. and Flight Refuelling Ltd. have respectively been concerned with the droning of the Fairey Firefly and the Gloster Meteor aircraft which are also used as targets for British missiles.

Navigation used to be solely concerned with the safest and most expedient means of directing an aircraft to its objective—either the destination airport or a military target. Nowadays, especially in civil aviation but increasingly in military transport operations, the need to comply with air traffic control (A.T.C.) procedures is tending to dominate both the technique of navigation and the kind of navigation aids used.

In recent years great stress has been placed on the problem of air traffic control and now, with the imminent arrival of jet air liners in large numbers, the consternation is even greater. Reactions to the problem vary, so that on the one hand there are the down-to-earth realists who see no immediate prospects of any revolutionary improvement in A.T.C. methods; on the other hand there are the optimists who already speak of the present A.T.C. system as though it is a thing of the past and talk of the “ new “ system which will replace it when the jets arrive. Despite the most extensive studies of the problem, such as that recently undertaken by the Curtis Presidential Committee in the United States, no entirely satisfactory description of the “ new “ system of A.T.C. has materialised. Meanwhile the penalities of restriction and delay of jet aircraft by air traffic control need no emphasis, but to give one example, the Comet I, when operated by B.O.A.C., regularly arrived at London Airport with at least two hours fuel as diversion and traffic reserve. The weight of this fuel was of a similar order to the total payload of the aeroplane, so it will be realised that economic operation of jet aircraft can stand or fall on this single issue of air traffic control.

An investigation into the turbulent flow characteristics in a smooth-walled annulus has been continued. Velocity and its correlation has already been dealt with in the author's note in the November 1958 JOURNAL (p. 830). In the work presented here, the eddy diffusivity in gas flow is discussed, its distribution predicted, and experimental results for the eddy difiusivity of heat in an insulated annulus with a heated inner wall are included in support.

The distributions of velocity, shear, temperature and heat flux for an annular flow with heat transfer at the inner boundary are shown diagrammatically in Fig. 1. The features of the turbulent velocity profile and methods of correlating velocity distribution are outlined in Ref. 1. The shearing stress T is given by the equation

The number of available exact solutions to the St. Venant flexure problem is limited, but there are some simple solutions which appear to have been overlooked. The sections covered are a wedge, a double wedge, a biconvex section, and an aerofoil-type section. All the solutions given are restricted to certain values of Poisson's ratio, depending on the section.

The components of shear stress parallel and perpendicular to the direction of loading are given by:

The first of these conferences was held in 1953, the second in 1954 and the third in November 1958 at Milwaukee. This third conference was sponsored by the Agricultural Research Service of the United States Department of Agriculture and, to promote worthwhile discussions, attendance was by invitation only.

Twenty papers were presented on four main themes, economics, progress as regards agricultural applications, progress as regards forest applications and, finally, a review of present and proposed research.