The noise radiated from the intakes of turbojet engines during landing is already causing a serious nuisance. This paper, which is largely based on the deliberations of an ad hoc working panel of academic experts formed by Rolls-Royce in 1961, describes the characteristics of the noise and discusses possible mechanisms of generation. The noise appears to be dipole in origin, and to come mainly from the first two compressor stages. It consists of a few discrete tone components, generated mainly by the interactions which occur when one row of aerofoils passes through the wakes of a preceding row; and broad band noise resulting from the turbulence in the wakes and the inherent instability of the boundary layer on the aerofoils.

Some discrete tones may be eliminated over part of the running range by suitable choice of blade numbers and disposition. The broad band noise is unlikely to be reduced without major design modifications involving either a reduction of the air speed relative to the front stage blades, or removal of the boundary layer at their trailing edges.

The lecture discusses the extent to which the problems met in the fuel systems of subsonic aircraft are aggravated by flight at supersonic speeds and mentions some new problems of considerable severity. These arise from the relatively large fuel quantity required, its high rate of consumption and its heating by kinetic effects or by its use as a heat sink for the aircraft systems. The paper includes a discussion on fuel management and gauging and of the means used to transfer fuel to the engines—showing the relative merits of some of the available pumping techniques. A few comments only are made on the engine control system.

The problem of thermal degradation of the fuel in the tanks and in components leading to the engine is discussed, with particular attention being paid to the difficulty of establishing a valid test method for differing aircraft configurations.

Spontaneous ignition of flammable mixtures in contact with heated surfaces is a hazard that is likely to arise in a particularly acute form at a Mach number of about 3. The progress of research into this phenomenon is briefly outlined, and some of the measures which may be adopted to ensure safety are indicated. Associated with this is the necessity to develop instruments to detect hazardous conditions in various parts of an aircraft, on which some recommendations are made.

Because two world wars have exerted such a profound influence on military aviation I have chosen to treat the subject under the following headings:

• The Beginning

• The First World War.

• The Inter-War Years.

• The Second World War.

• From 1945 to the present.

• The Future.

Under each heading I will endeavour to outline the developments and changes in technology and rôle which have taken place, and to indicate the effects these were to have upon each succeeding period.

Blue Streak is to be the first stage booster of a three stage satellite and space probe launcher being developed in Europe. The main contractor for the Blue Streak rocket vehicle is Hawker Siddeley Dynamics Ltd. with the propulsion system the responsibility of Rolls-Royce Ltd. The work reported in this paper was carried out under Ministry of Aviation contract and forms part of the United Kingdom participation in the initial programme of the European Launcher Development Organisation (E.L.D.O.).

The static or “tethered” firing of liquid-propelled rocket vehicles is an essential process in the establishment of operational reliability before attempting launchings.

The world of hearing is made up of two types of sound— on the one hand, that which provides communication, be it in the form of speech, music or the noise of a car or dog; on the other hand, a noise which interferes with that message, or a sound consisting of an unwanted message, intruding upon a person's thought processes or sleep. It is always difficult to separate these two functions, since one man's noise is another man's message, and this is particularly so for quiet noises heard at night or occurring sharply to frighten and alarm. It is for this reason that the law regarding noise has been less specific than in other fields and it is for this reason that seldom have any clearly defined limits been specified.

This brief paper attempts to outline the present methods for the legal control of aircraft noise and, by emphasising potential weaknesses, draws attention to possible improvements for the future. The views expressed are personal opinions only and must not be interpreted as the views of Insurers generally or the British Aviation Insurance Co. Ltd., in particular.

Professor Richards has clearly described the technical problems involved in the control of aircraft noise. In its essentials, any system of legal control must involve the evolution and enforcement of standards in the design and operation of aircraft, airports and aircraft-affected communities.

Static probes, although widely used in supersonic tunnels and in flight, have not formed the basis for many reports on their design and behaviour at high Mach number.

It is known, however, that the flow over the nose of the probe causes pressure variations such that it is some distance along the probe before the static pressure is equal to free stream static pressure. The NPL, in a series of tests at M = 1.6 showed that the pressure measured at a point situated less than 10 calibres (probe diameters) downstream of the beginning of the parallel portion of the probe was dependent on the shape of the nose.

Interest in sail design has recently stimulated some work, using thin aerofoil theory, to obtain the velocity distribution on simple polynomial mean lines. In particular in reference 1, a solution has been obtained for a cubic mean line. There is an omission in equation (3) of this reference where an x should appear in the numerator outside the curly bracket. (The equation is subsequently used in its correct form).

In the present note a general solution is obtained for polynomial mean lines. It is demonstrated by applying the result to Boyd's equation (3).

I am grateful to Mr. Llewelyn for pointing out the slip in equation (3) of reference 1.

In considering a particular case of the polynomial camber line I did have to evaluate a number of integrals of the kind but the process is not as laborious as perhaps Mr. Llewelyn implies for there is a simple recurrence relation between integrals of this kind.

An analytical method is presented for the design of two-dimensional contractions. In this method, the complex potential of the flow of an infinite row of equally spaced line sources normal to a uniform stream is obtained. By adjusting the strength of the sources, the streamlines of the main stream are used as boundaries of two-dimensional contractions of various contraction ratios. It is found that, in all cases, there is a region in the main stream between two neighbouring sources in which the speed of flow increases monotonically along streamlines. Contractions formed by any of the streamlines in this region would therefore have favourable pressure distribution along their boundaries except for very small adverse pressure gradient at the inlet and outlet which are due to the introduction of parallel sections.

In the December issue of the Journal some measure of agreement appears to have been reached between Bragg and Smith and the present writer, at least for the second example. The difference of opinion in the first example centres on whether a propelling nozzle with a thrust efficiency exceeding unity necessarily implies perpetual motion. The argument that it does may be put as follows.

In a recent paper the suggestion is made that “it would be sensible when discussing the flow to use a Mach number based on the actual propagation velocity in the given circumstances.”

This directs attention to the deeper question of whether or not a Mach number however defined is a rational parameter in terms of which to express effects of flow.

In certain cases the quantity γp/ρ occurs quite naturally, regardless of any physical interpretation that can be given to it.