The 1,157th lecture to be given before the Society, “Supersonic Aircraft—Promise and Problems” by M. B. Morgan, Esq., C.B., M.A., F.R.Ae.S., Scientific Adviser to the Air Ministry, was given on 17th March 1960, at the Institution of Mechanical Engineers. Mr. Peter G. Masefield, M.A., F.R.Ae.S., Hon.F.l.A.S., M.Inst.T., President of the Society, presided. Opening the meeting Mr. Masefield said he thought this would be one of the most interesting and stimulating lectures of the session. The subject of the supersonic aeroplane had been freely discussed in the United States and probably in Russia also. In this country they had been more reticent so he hoped they would have a really good discussion after this lecture. One significant point was that people no longer wondered whether a supersonic transport could, or should, be built but only whether it should cruise at a Mach number of 2 and be made in light alloy, or whether it should be around Mach 3 and be made of steel or more exotic materials. That sooner or later—and many believed sooner—transports would fly at supersonic speeds at 70,000 ft. was taken for granted.

Mr. Morgan was well known to them all. Born in Wales, he was educated at Rutlish, Merton and St. Catharine's College, Cambridge, where he took the Mechanical Sciences Tripos and won the John Bernard Seely Prize in Aeronautics in 1934. In fact, he and Mr. Morgan used to enjoy the Cam together and Mr. Morgan looked little different today than he had in those days. Mr. Morgan was apprenticed to Mather and Piatt Ltd. and also spent a short time at Vickers, Weybridge before joining the R.A.E., Farnborough in 1935. Since then he had specialised in aerodynamics, flight research and development, stability and control and, he had taken his Pilot's Licence in 1944. He was Head of the Aero Flight Section of the R.A.E. from 1946-1948, Head of the Guided Weapons Department from 1948-1953 and Deputy Director of the Establishment from 1954 until 1959. He had then been appointed to his present position of Scientific Adviser to the Air Ministry and had also been Chairman of what had come to be known as “STAC”–Supersonic Transport Aircraft Committee. He felt that they could have no better person than Mr. Morgan to talk on the Supersonic Transport.

It is singularly appropriate that Mr. Walter Tye should be in the Chair today, not only by reason of his membership of the Air Registration Board, that Cerberus which watches so efficiently over so many aspects of safety in the air, but also for a more personal reason. He recently received the “ Aviation Week “ Award for distinguished service in achieving safer utilisation of aircraft, and I should like to take this semi-public opportunity of adding my congratulations to the many which he has received.

In many of the offices of my airline one finds displayed a small plaque. On it appears, among other words, the legend “Safety is no Accident.” Although I am no great believer in the power of an oft-repeated formula to achieve miracles, I do believe that these words hold within them much of my flight safety philosophy.

Before examining the Airline Pilot's views on Flight Safety, a brief look at this Airline Pilot will be taken to get a rough idea of the viewpoint from which he speaks.

The Chairman, in his opening remarks, referred to pioneering. In the early days of aviation the pilot was a pioneer, and as such he had to take risks. At the present time, and in some parts of the world many years ago, the pioneering adventure of flying has grown up into a serious transport industry, and the airline pilot has grown up with it. Today, the airline pilot is an executive of that transport industry; a highly skilled employee or a highly specialised manager depending on the way you look at him.

When I was asked to take part in this Symposium it was suggested to me that I should talk about the Accident Investigator's view on Flight Safety. Now I do not suppose that the accident investigator's view is very different from the view of anyone else working in the safety field. The whole object of flight safety is to prevent accidents and the whole object of the accident investigator is to ascertain the causes of accidents so that remedial measures may be taken.

Flight Safety is a subject which ranges outside the control of the Aircraft Constructor and so it has been interesting to learn the other points of view from the other papers. While it should be the natural aim to see that the aircraft matches the highest standard of safety, the constructor's control over this in the hands of the operator is limited.

The Matrix Force Method is frequently used in the stress analysis of complicated aircraft structures. It assumes as unknown quantities, or redundancies, groups of internal loads, and yields stresses and displacements in terms of a set of unit loads. Lately, this method has been extended to include effects of uneven temperature distribution. With large structures, the method is most effective with high speed digital techniques which allow considerable computational detail to be stored in the computer memory. Theoretically, the method is based on the Castigliano theorem of least work, equivalent formulations being possible. Hence the method is applicable to elastic problems of the first order only, i.e. strains infinitesimal, structural distortions not affecting equilibrium conditions markedly.

There have been numerous attempts to predict the stand—off distance of bow shock waves, ranging from the exact solutions of the inviscid flow equations by Mangier (1959) and Van Dyke (1959) to the semi—empirical treatment of Moeckel (1949) and Love (1957). Sinnott (1959) has recently proposed a single formula Δ/R=K cot θm where K is a numerical constant given as 0·77 for axisymmetric bodies and the symbols are defined in Fig. 1.

In many cases of the flow through porous screens, one may consider it to be made up of a number of jets passing through the openings of the screen. These jets are separated by a series of wakes behind the solid parts of the screen. The majority of investigations on the flow through such screens have been concerned with the measurement of pressure drop and its variation with different flow conditions; it has been assumed that the pressure is discontinuous at the screen itself and that the pressure drop coefficient Δp/½ρυ2 provides sufficient information, where Δp is the pressure drop across the screen, ρ the density of the fluid, and υ the velocity of approach to the screen.

In ref. 1 an extensive review was made of the panel flutter problem and analyses dealing with flutter of cylindrical shells of finite length were discussed in considerable detail. It was stated that one of the central points of controversy is in the choice of the appropriately simplified governing equations for the thin–walled elastic shell. Related to this is the choice of flutter mode and the question as to how the critical flutter speed depends upon the number of circumferential and axial waves in that mode.

Stepanov and Strack and Holt found that the critical Mach number decreases with increasing number of circumferential waves, and Fung has concluded that the axially symmetric mode is of the greatest interest.

The purpose of this note is to present a relatively simple analysis in which only axi–symmetric deformations of the shell are considered. The shell is assumed to be unreinforced longitudinally.