The 902nd Lecture to be given before the Society, which was also the 15th Main Lecture at a Branch of the Society and the First Barnwell Memorial Lecture, was held under the auspices of the Bristol Branch on 4th March 1954. The Lecture was delivered by Major G. P. Bulman, C.B.E., B.Sc, F.R.Ae.S., Director of Construction and Research Facilities, Ministry of Supply and a Past President of the Society.

Dr. A. E. Russell, F.R.Ae.S., President of the Bristol Branch, opened the meeting and then invited Sir William Farren, C.B., M.B.E., M.A., F.R.S., M.I.Mech.E., F.R.Ae.S., President of the Society, to preside.

For US in the early evening of life, who have witnessed the development of aviation since the Wright brothers flew in 1903, for us, it is hard—and a little sad—to realise that some of our great pioneers are already becoming almost mythical characters. They were our personal friends with whom we worked most happily; yet, to the young men of today, who are now carrying, or are about to don, high responsibilities in the aeronautical world, they are indeed just names. And so it is fitting that the Royal Aeronautical Society should have inaugurated these Memorial Lectures, of which this is the third. I am deeply sensible of the honour and responsibility which have fallen to me by the choice of the Bristol Branch to pay this first tribute to Captain Barnwell. May I say at once how indebted I am for so much of the detail of this appreciation to Mr. C. W. Tinson, who served with Barnwell for most of his career at Bristol; to Mr. C. H. Barnes, who has written the history of the Bristol Aeroplane Co.; and several other “ old hands.” It is significant that in all my conversations with them, they referred always with obvious affection and deep respect to “the old man.”

A simple cumulative fatigue damage law is used to estimate the endurance of a number of typical structural components when subjected to the alternating wing loads encountered by an aircraft in flight. A method is developed to study the fatigue damage in terms of infinitesimally small intervals of alternating load and the corresponding fatigue strength. Recent gust data are used in conjunction with the complete fatigue strength diagrams of 13 simple components. The fatigue damage is studied for the ranges of altitude (i) up to 12,000 ft., and (ii) above 30,000 ft. In each case it is found that the damage rate curve, which gives the intensity of fatigue damage at any gust velocity, takes a characteristic form, with a well-defined range of gust velocities giving the greatest fatigue damage. This leads to a simplification of the whole problem, and it is found, finally, that the life of the structure is governed—in so far as the cumulative law is correct—almost entirely by that gust velocity, which, when applied alone to the structure, gives an endurance of about two million cycles. The results of the survey are compared with the design criteria suggested by Walker and the lives estimated by Williams.

The 899th Lecture to be given before the Royal Aeronautical Society was held on 11th February 1954 at the Institution of Mechanical Engineers, Storey's Gate, London, S.W.I. Mr. G. R. Edwards, C.B.E., F.R.Ae.S., Vice-President of the Society, presided. Introducing the Lecturer, Dr. D. Williams, M.I.Mech.E., F.R.Ae.S., Mr. Edwards said that Dr. Williams was really too well known to need any introduction; his activities had been devoted in recent years to structural problems as applied to aeroplanes. Without reciting his attainments in detail, the job he had tackled in recent years at the Royal Aircraft Establishment and about which he had written papers, covered such subjects as vibration, wing flutter, sandwich construction, the effect of blast on aeroplanes, energy theorems, fatigue, dynamic loading by gusts and landing impacts, water-borne runways and nose-wheel shimmy, a variety of subjects one or all of which had caused most of them a great deal of anguish at one time or another.

Stability criteria for systems governed by linear differential equations with constant coefficients are discussed in a general way. Detailed treatment of the sextic equation includes a simple and expeditious scheme for computing the test functions.

Glass Cloth/Polyester resin laminates similar to those described by Irving and Saunders (Journal, February 1954) have been used at the University Engineering Laboratory, Cambridge, in the manufacture of blades for an axial flow compressor. In the first experiments, an existing aluminium stator blade was used as a pattern, and a mould was made by pouring molten type metal round this pattern, held in a steel sided moulding box.

An Experimental study of fluid flow past a symmetrical aerofoil with a rear suction slot and a retractable flap was described by D. M. Heughan in the October 1953 JOURNAL. The present note describes the electric tank method for studying the same problem. The experimental apparatus is shown in Fig. 1. A and B are electric poles along two of the edges of the tank which is filled with water. The poles A and B together with the central pole P are connected to an electric supply via a resistance R in such a way that the potential of P is intermediate between that of A and B. The aerofoil F is represented by a wooden block coated with paraffin wax and the pole P is located in such a way as to represent the sink in the suction slot. A voltmeter V records the potential at a point in the tank.

An outline is given of a combined photoelastic and fatigue programme of work on single-pin double-strap joints; the stress concentration factors obtained from photoelastic tests are to be correlated with the results from a parallel series of metal fatiguetests on geometrically similar specimens. The form and dimensions for a photoelastic specimen suitable for this work are given. Further results will be published as the work proceeds. This Note outlines a programme of work recently initiated by the Royal Aeronautical Society, and now being done under Ministry of Supply contract, in connection with the fatigue strength of bolted joints.

In My Note on “Stress Analysis of Circular Frames ” I was unable, due to lack of space, to discuss more thoroughly the reasons why the name of W. Ritz is omitted with reference to his method. The reader, interested in that subject, can find all the details in my recently published discussion and paper.