The present time, when the prospect of high speed flight often seems to recede, not to approach, may well be a good occasion to review the ram-jet, an engine whose main use is at high flight speed. We owe the succinct name “ ram-jet” to the Americans and the original idea to the French. But despite the admirable efforts abroad this paper is most concerned with British ideas, especially and naturally with those conceived and prosecuted at the National Gas Turbine Establishment. At the outset it is appropriate to acknowledge all the separate personal contributions to the subject of this paper and the assistance of my colleagues in preparing some of the information presented.

Thermal effects in aircraft may arise from kinetic heating, engine installations and auxiliary systems. The first source is potentially of greater importance, although problems in connection with the second source can be severe, especially with vertical take-off aircraft of the “flying bedstead” type. The difficulty encountered in a formal analysis of heat conduction problems when practical boundary conditions are to be satisfied frequently suggests a finite difference approach. This may take the form of direct numerical integration or the use of digital or analogue computers or network analysers in which electrical circuits are arranged to be analogous to the thermal system. Several examples illustrating the use of these finite difference methods are instanced, such as the growth of temperature in a thick plate, the transient distribution of temperature in a rib carrying a hot duct; the chordwise distribution of temperature and transient loss in torsional stiffness in a thin wing due to kinetic heating, and the distribution of temperature and spanwise thermal stress due to kinetic heating in a bay of an integrally stiffened panel. The importance of experimental methods is emphasised and a brief description and illustration of a model fuel tank for simulated kinetic heating tests is given. An urgent plea is made for correlated data on thermal contact resistance of typical aircraft joints, some examples of which are also illustrated. Data is given on some physical and mechanical properties of materials likely to be used for airframes where thermal effects are expected. These include thermal expansion, conductivity, diffusivity, creep, fatigue, specific strength and stiffness, and a parameter called here the “Thermal Stress Efficiency.”

In considering this subject we should first briefly examine how guided missiles came on to the scene. Manned flight in heavier-than-air vehicles is some 50 years old and, once the early scepticism of sopie critics had been overcome, very large and highly successful efforts were made to use flying machines of this kind for direct military purposes. The scope of these efforts and the measure of success that attended them are well known and have been the subject of many of the papers and much of the discussion which the Royal Aeronautical Society has enjoyed in the past 50 years or so of its 90 years of active life. It is indeed significant that the two World Wars of the past 40 years have, by reason of the extra effort they focused on military aviation, been the cause of most of the advances in aviation and thus brought about commercially and economically successful civil aviation as we have it today.

Ten years ago take-off speeds rarely exceeded 130 m.p.h. and the maximum inflation pressure used in aircraft tyres was about 120 lb./in2. Today tyres have to cater for speeds up to 230 m.p.h. and pressures of 350 lb./in.2. The increased requirements have produced serious problems of heat generation within the tread and carcass of tyres, which, if not solved, result in disintegration. Fig. 1 shows the effect of speed on tyre temperature and also, the effect of lightening the tyre construction.

Beyond the speed range shown, the temperature rises rapidly and tyre failures would occur. To meet these conditions, improved materials with lower hysteresis losses, and capable of operating at higher temperatures, have been produced. Control can also be obtained by modifying casing cord angles, reducing casing and tread thicknesses and so on.

Lagrange's Interpolation formula can be used to obtain an approximate polynomial representation of a curve (derived empirically, or known otherwise) as well as to interpolate between isolated values of a function. In obtaining such an approximating polynomial, standardisation of the values of the independent variable has the advantage that many relevant quantities can be calculated and tabulated (or plotted, or both) in advance.

A New type of auxiliary equation is given for calculating the development of the form-parameter H in turbulent boundary layers with adverse pressure gradients. The chief advantage of this new method lies in the rapidity and ease of calculation which has been achieved, without apparent sacrifice of accuracy.

Whereas the growth of momentum thickness in the turbulent boundary layer can now be rapidly calculated by methods involving only simple quadrature, the prediction of the form parameter development remains a laborious task, while the results obtained do not always appear to justify the complexity of the calculations.

The Function of the air intake of a gas turbine engine is to deliver whatever air mass flow is required, with the best recovery of ram stagnation pressure, over the desired range of flight speeds and altitudes.

Although it is generally shown in other forms, the performance of an air intake for supersonic flight can be represented on charts very similar to those of a rotating compressor. In Fig. 1 the ratio between ambient (static) pressure and stagnation pressure at the diffuser of a typical intake is shown as a function of corrected inlet and outlet air mass flow (which are themselves functions of the local flow Mach numbers), for a series of flight Mach numbers.

It has been suggested to the Divisions of the Society overseas and to the Singapore Branch that, instead of publishing their Annual Reports, it would be of more general interest to publish, two or three times a year, news of their activities and of aeronautical developments in their areas. This month we publish reports from the New Zealand and Southern Africa Divisions and hope that we shall have news soon from the Australian Division and the Singapore Branch.—Ed.