Several years ago it became apparent that there was a need for some means of reversing the thrust of jet engines on landing—the equivalent of reversing pitch propellers on piston and turbo-prop engines.

Many different designs were investigated on the drawing-board, with experimental backing in some cases, and when the best configurations had crystallised detail work started on a reverser for the Avon engine. While this was being developed a second design, identical in its main principle but different in many small ways, was prepared for the Conway engine.

Recent developments in the control systems of aeroplanes have been such as to underline the need for new terms, and the need to remove any ambiguity relating to terms already in existence. The question has also been raised by the British Standards Institute in relation to the revision of the Glossary of Aeronautical Terms. The present paper examines the problem in the light of possible future developments, lists proposed terms with their definitions, and gives an outline of the underlying arguments. It is written in the spirit that in the field of systems of units, notation, and nomenclature “survival of the fittest” will always apply. The details of the nomenclature are not considered all-important, but we have tried to select the right concepts, to classify sensibly, and to produce accurate and general definitions. We expect many useful and amusing comments on nomenclature, but the other aspects are the fundamental ones, and we hope there will be some constructive criticism.

A centrifugal compressor rotor is quite robust, but the blading of an axial compressor looks horrifyingly fragile and very susceptible to damage by objects sucked into the engine. The introduction of axial compressor engines into airline service brings this again to the attention of designers and service engineers. The object of this paper is to outline the problem, and to describe one experimental approach to assessing the relative merits of different blade materials from the damage point of view.

Air dissolves in aircraft fuels to an extent directly proportional to the ambient pressure, so that when fuel which has been stored at sea-level atmospheric pressure is taken up to a high altitude, there is a tendency for air to come out of solution. In certain circumstances, which are later described in detail, air bubbles can be liberated very violently from fuels in aircraft tanks at high altitude and a thick foam can form on the surface for a short time.

The production of fuel foams by degassing has posed a certain problem; foams, being intimate mixtures of air and fuel, may well be inflammable; furthermore, the rising of air bubbles through fuel can result in the accumulation of electrical charge in the foam giving rise to the possibility of a source of ignition.

Summary: Modern radar techniques have found wide application in the fields of aeronautics and guided missiles and to make full use of these techniques the designer of modern aircraft and missile systems requires a knowledge of the basic radar principles. This paper is an introduction to these principles. Four main functions of radar are discussed, namely the detection of objects in the beam, measurement of range, information on direction, and the use of the doppler principle to measure velocity and to distinguish moving objects. The discussion is confined to primary or self-contained radars although the principles are applicable to navigation aids such as Gee and Loran. The paper concludes with a brief description of the radome problem.

Data were obtained of the pressure loss characteristics of metal strip matrices constructed by winding together alternate layers of crimped and plain metal strip. The hydraulic diameters of the passages so formed were in the range 0.023 in. to 0.060 in. with passage lengths from 1 in. to 6 in. and metal thickness from 0.002 in. to 0.006 in.

The units were mounted in a 6 in. diameter duct in which air velocities of up to 200 ft./sec. were obtained. The range of passage Reynolds number was from 300 to 6,000. The majority of the experimental results were for atmospheric pressure, but some tests were carried out at sub-atmospheric pressures to test a correlation equation derived from analysis of the results.

The calculation of damping from the results of resonance and free oscillation experiments has hitherto been based on elementary theory in which the springs or other elastic supports are represented by lumped stiffness parameters. This “ light spring theory” is generalised here to include the elastic stiffness terms in distributed parameter form; i.e. the mass of the springs or other supports is taken account of by including wave equations for the propagation of stress waves in the springs and so on. A record of the free motion of a model in a wind tunnel, shown in Fig. 1., indicates the inertial effects of the spring supports. To minimise this “surging” of the supports one may design them to have high natural frequencies compared with the system frequencies. However, this gives no indication of the error entailed in using light spring theory, nor does it cover experiments which must be performed at high frequencies.