bluuebunny/crossref_metadata_2025 huggingface dataset:
The Relationship Between Fatigue and Stress Concentration
Authors: Heywood R.B.
Published: November 2014

It is well known that notches have a deleterious influence on the fatigue strength of parts. A constant, the sensitivity index, is commonly used to relate the fatigue stress concentration factor to the elastic stress concentration factor. The author outlines a simpler hypothesis, which he claims to be a more reliable guide to fatigue behaviour in notches. Briefly it assumes that the elastic stress concentration factor gives the reduction in the fatigue strength due to the notch, but because of the local nature of the stress concentration, the endurance limit is increased according to a simple law. This increase in the fatigue strength depends on the smallness of the notch.
Adiabatic Flow in Pipes
Authors: Lukasiewicz J.
Published: November 2014

When the flow in long pipes is considered, the frictional losses occurring before the pipe entry can usually be neglected. If thus an isentropic flow up to the pipe entry were assumed, the Grashof and Zeuner equation (A. 12) could be represented in the ψ—p plane of the dimensionless de Saint Venant and Wantzel equation (A.23). Using the dimensionless equations of Appendix II, the above plane is developed to cover adiabatic flows in general.
A Note on Axial Flow Fans for Aircraft Ventilation
Authors: Williams J.A.C.
Published: November 2014

AXIAL flow fans were originally developed from aircraft airscrews and therefore can be claimed as children of aeronautical science. Their use has been confined in aeronautics to wind tunnels and radial engine cooling until the advent of ‘pressurized’ cabins. In this case ventilation requirements have caused an axial flow fan to be used. These fans have been gradually developed in the ventilation industry and they are replacing centrifugal fans where these would have been used previously. Price and noise level have not been in the axial flow fans' favour in this fight but they have advantages of higher efficiency, ease of installation and non‐overloading power characteristic. Latest developments in aerodynamic design and production technique suggest that the disadvantages are being overcome. This note is intended to furnish a general introduction to the design features of axial flow fans for aircraft ventilation.
Book Reviews
Authors: Duncan W.J.
Published: November 2014

Although this volume has only just come to hand it bears the date 1938 and it is, therefore, not surprising that most of the contents are considerably out of date. The book, which is written in French, begins by giving a general description of the wind tunnel at the Ecole Polytechnique at Bucarest. The general layout of the wind tunnel is very similar to that of the compressed air tunnel at the N.P.L. but the tunnel works with air at normal atmospheric pressure and the main structure is built of wood. The exterior casing of the tunnel is in effect an independent building exposed to the weather and takes the form of a horizontal octagonal prism with truncated pyramidal ends. The working section is 1·5 metres in diameter and a driving motor of 40 kw. gives a top speed of 46 metres per second or very roughly 150 ft. per second. Results of tests on a considerable variety of Joukowski aerofoils carried out at a Reynolds number of a little below half‐a‐million are given in the report. On account of this low Reynolds number and of the fact that the sections are not of types now used in practice, the data will be of little interest to the aircraft industry. One minor point of terminology which appears to be worthy of comment is that profit a didre means a profile having a finite trailing edge angle, the idea being that there is a dihedral angle between the tangent planes at the trailing edge.
An Electrical Study of Boundary Lubrication
Authors: Brix V.H.
Published: November 2014

IN a previous article discussing ‘Boundary Lubrication’ we described this type of lubrication as of the greatest significance because it is the most frequently encountered condition in everyday machinery. The fact that ordinary bearings, bushes, and indeed reciprocating parts and gear teeth, depend so much on the materials of which they are composed can be taken as evidence that ‘Boundary Lubrication’ plays a predominant part in the functioning of these components.
A Survey of Plastic Materials for Students
Authors: Fitzgerald‐Lee G.
Published: November 2014

IN 1865, Alexander Parkes, of Birmingham, found that the potential explosive nitrocellulose could be plasticized by being mixed with camphor and alcohol, and thus was discovered the ‘celluloid’ named, after its originator, ‘Parkesite’, the forefrunner of ‘Xylonite’. This discovery was the beginning of the plastics industry which has, in only eighty years or so, grown to be one of the major industries; so much so, in fact, that the Twentieth Century has been referred to, by some enthusiasts, as the ‘Plastics Age’.
Spring Tabs
Authors: Baker F.B.
Published: November 2014

The first step in calculating stick force is to modify the wind tunnel hinge moment curves. This is done by obtaining a curve for b1 at various incidences, and then altering the measured hinge moments in accordance with the formula in para. 15. Numerical examples of this process are given in Tables 1, 2, 3, and the new hinge moment curves plotted in figs. 25, 26, 27.
The Design of Oscillating Cantilevers
Authors: Turner B.T.
Published: November 2014

THE advent of practical working centrimetric radar brought many mechanical and structural problems. One of these was the design of oscillating cantilevers to carry light dipole aerials.
Some Bomber Range Considerations
Authors: Jones J.
Published: November 2014

THE range of an aircraft is given by Breguet as
Numerical‐Graphical Method of Stressing Hollow Girders
Authors: Lockwood Taylor J.
Published: November 2014

THE simplified method of stressing which follows is an extension of one first developed as a means of attacking the shear‐lag prob‐lem for a ship‐beam (Trans. N.E. Coast Inst, of Engrs., 1924–5). It is now extended to cover also axial stresses due to torsion and departure from the Batho torsion shear, a related subject. Shear‐lag and diffusion are closely connected and a theory which covers one should have at any rate a general application to the other; it is not, how‐ever, claimed for the present method that it is very suitable for use where the rates of diffusion are locally high, and its applicability to diffusion problems in general is a matter of judgment.This of course applies also to any corresponding method. The method is considered first for a girder of uniform transverse dimensions (no taper of depth or width) but with variation in scantlings along its length. Later the first‐order effect of tapered dimensions is considered. There may be longitudinal stiffeners at any point in the section, e.g. spar booms or stringers. The transverse sections of the girder are assumed to retain their dimensions with absolute rigidity.
The Library Shelf
Authors: D.M.C.
Published: November 2014

Within the last two decades great progress has been made in the field of hydrodynamics, both in the theoretical sense as well as the practical. This has been particularly noticeable in the rapid advances made, in aircraft and propeller design, which owes most to the successful application of aerodynamical theory. Not so noticeable, and certainly less obvious, are the results obtained by the application of fluid mechanics in other branches of engineering, as for example, in the design of turbo‐machinery such as turbines, pumps, compressors and that pump‐cum‐turbine arrangement known as the torque converter and the so‐called fluid flywheel. In these latter classes of machinery the more modern theories do not attempt to throw down or displace the older laws, by whose means many successful designs have been accomplished, but on the other hand are direct developments thereof as a result of more intensive study. The most important development of recent years, due to the greater knowledge of fluid mechanics, is adequately illustrated by the amazing progress made in the design and performance of axial compressors. Some thirty years ago, a similar but less spectacular application of fluid mechanics was devised in the form of the Michel or Kingsbury thrust bearing.
Thermodynamic Properties of Combustion Gases
Authors: Kestin J.
Published: November 2014

THE calculation of gas turbine efficiencies on the basis of the real properties of the working medium is a laborious process. Such a calculation involves the determination of the composition of the combustion gases for a series of air/fuel ratios, and the evaluation of a number of thermodynamic properties at various temperatures and pressures, such as the enthalpy (total heat), entropy, specific heats, etc. These properties are calculated from the tabulated properties for the component gases with the aid of the rules for mixtures.
The Stresses in Closed Cylindrical Vessels
Authors: Conway H.D.
Published: November 2014

IN a previous paper (AIRCRAFT ENGINEERING, Vol. XIX, February 1947, pp. 52–4) expressions were derived for the maximum bending moment and shearing force in vessels closed at one end and subjected internally to (a) gas pressure, (b) hydrostatic pressure. The method of solution has been extended in this paper to include the cases of cylindrical vessels, closed at both ends by flat plates or hemispherical shells and subjected to gas pressure.
The Elementary Theory of Stressed Skin Construction
Authors: Hemp W.S.
Published: November 2014

THE types of problems treated in the Theory of Structures can be conveniently classified under three headings:
The Design of Redundant Structures for Minimum Weight
Authors: Parkes E.W.
Published: November 2014

THE procedure usually adopted for the design of a redundant structure is to assume some initial distribution of material and then to stress this by strain energy methods. From the knowledge of the load distribution thus acquired a second structure is designed and stressed and the process is repeated, if necessary, until a reasonably uniform stress is obtained.
‘Redux’ Bonding a French Fighter Aircraft
Authors: Moss C.J.
Published: November 2014

IN a recent issue of AIRCRAFT ENGINEERING Mr R. H. T. Harper, of Messrs de Havilland Aircraft Co. Ltd., gave an account of the design considerations which led his company into using composite wood and metal spars for the ‘Hornet’ single‐seater fighter. Such a method of construction was made possible by the development of the ‘Redux’ process for bonding metal to wood by Messrs Aero Research Limited, Duxford, and it was the first of a number of advanced designs made possible by this new process. They have already been described at some length in a number of articles in the technical press (see Bibliography), and it is only necessary to state here that when using the ‘Redux’ process for bonding metal to wood the strength of the bond is always greater than that of the wood itself even at 100 deg. C., and that the process can equally well be applied to the gluing of metals to metals (e.g. see the description of the use of ‘Redux’ on the de Havilland ‘Dove‘ given in The Aeroplane, September 20, 1946).
The Economic Value of Increase of Modulus of Elasticity in Aluminium Alloys
Authors: Cox H.L. , Windle Mrs M.J.
Published: November 2014

IN the present note a comparison is made between normal aluminium alloys and alloys with increased values of the modulus of elasticity for covering the upper surfaces of wings of moderately thick sections, particularly of the smooth wing type. This comparison is intended to form the basis for the design of test panels for experimental verification of the theoretical conclusions.
Longitudinal Stability, Speed and Height
Authors: Neumark S.
Published: November 2014

IN high‐speed level flight in the compressibility region an entirely new factor makes its appearance, viz: small variations of atmospheric density and speed of sound with height. This factor affects dynamic stability due to continuous changes of height during longitudinal disturbances; there is no effect in lateral disturbances. The affects are very small in low‐speed flight but they increase steadily with Mach number. The short‐period oscillations are not affected but the corrections to phugoid motion become appreciable in high subcritical flight, larger in supercritical (transonic) range, and very important in supersonic flight. The effects of compressibility are of paramount significance but they should be considered in conjunction with varying height effects. Another result of the investigation is the appearance of a new mode of disturbance, due to the stability quartic being converted into a quintic. The fifth (real) root is often small, it may vary in sign according to aerodynamic properties of the aircraft and characteristics of the power unit. The new mode is a subsidence or a divergence, and it determines height stability or instability, hence it may show to what extent an aircraft is able to keep constant altitude over long stretches of time.
Present‐Day Stalling Risks with Civil Aircraft
Authors: Clark K.W.
Published: November 2014

SO much of the aircraft designer's attention has lately been diverted toward major developments such as supersonics, that there is some possibility of old‐established hazards like inadvertent stalls being forgotten. The only difference in these nowadays is that stalling speeds are generally higher and aircraft can strike the ground harder. There is perhaps therefore good reason for considering stalling hazards once again. In doing so, my remarks are confined to civil aircraft, partly because the safety of Service aircraft must often give way to their operational needs and partly because their accident statistics are not readily available for discussion.
Variation in Strength of Nominally Identical Tail Planes
Authors: Raithby K.D.
Published: November 2014

IN the strength testing of major components of aircraft structures, considerations of time and expense do not usually permit the use of more than one specimen of any component. However, it has long been realized that, if a number of nominally identical specimens of any given component were tested, there would be some variation in failing load and probably in mode of failure, and that this variation would depend on the type of construction.
Laterally Loaded Non‐Uniform Struts
Authors: Gittleman W.
Published: November 2014

THE bending moments in a strut with lateral loading can usually be found graphically by means of the Polar (Howard) Diagram, but with a strut of non‐uniform section and a complex load system it is difficult to obtain an accurate solution without drawing to an inconveniently large scale. The tabular method described here is applicable to struts of varying section with any load system and involves only arithmetical calculation. The strut is divided into a convenient number of ‘simple’ segments, i.e. segments of uniform section with no point loads applied within the length of each segment, and successive applications are made of relations between the bending moment and slope at either end of the segments. Two trial solutions are necessary, from which the required solution is readily obtained.
The Length of Aerofoil Curved Surfaces
Authors: Falkner V.M.
Published: November 2014

IN applied aeronautics it is frequently necessary to calculate the distance along the curved surface of an aerofoil, not only for constructional purposes, but also in order to deal with some of the problems in applied aerodynamics which play an essential part in modern design. Aerofoil sections are usually defined by rectangular co‐ordinates, the offset distance Y from the chord line being given against values of X, the distance along the chord from the leading edge. It is usual for X and Y to be expressed non‐dimensionally in terms of the chord as the unit.
The Warping of Thin Shells
Authors: Morse William
Published: November 2014

IT is well known that cross‐sections of a thin‐walled shell, unconstrained at the ends, do not necessarily remain plane under the action of an applied torque, but may undergo axial displacement or warp, as it is called.
An Experimental Single‐stage Air‐cooled Turbine
Authors: Reeman J. , Buswell R.W.A.
Published: November 2014

To facilitate future development of the cooled gas‐turbine, more test information is needed on the effectiveness of cooling in an actual turbine operating at high gas‐temperatures. Part I of this paper deals with some design aspects of a single‐stage experimental turbine built to enable an experimental investigation to be carried out on the air cooling of nozzles and blades. The turbine, built for operation at high gas‐temperatures, was fitted with internally air‐cooled blades having a large number of small cooling passages running the whole length of the blades. A description is given of the pressed powder technique used to introduce the small passages in blocks of heat‐resisting material from which the blades could be machined. Mention is made of some of the difficulties encountered in this method of manufacture and also of the need for careful consideration of suitable methods of disposal of the cooling air when internally cooled nozzles and blades of this form are used.
British Progress in Propulsion Since the War
Authors: Baxter A.D.
Published: November 2014

IT is well known that war gives a great impetus to development in many fields, not least of which is that of aircraft propulsion. Such was the case in World War II, when great strides were made, but it is interesting to note that the pace has hardly slackened in the years following its conclusion. This is perhaps because of the ‘cold’ war which took its place, or perhaps because the introduction of jet propulsion has stimulated thought and action in realms beyond the dreams of the piston engine era. Whatever the cause, the results are apparent and this is a suitable moment to look back and measure the progress of the past seven or eight years.
An Experimental Single‐stage Air‐cooled Turbine
Authors: Ainley D.G.
Published: November 2014

A comprehensive series of tests have been made on an experimental single‐stage turbine to determine the cooling characteristics and the overall stage performance of a set of air‐cooled turbine blades. These blades, which arc described fully in Part I of this paper had, internally, a multiplicity of passages of small diameter along which cool air was passed through the whole length of the blade. Analysis of the test data indicated that, when a quantity of cooling air amounting to 2 per cent, by weight, of the total gas‐flow through the turbine is fed to the row of rotor blades, an increase in gas temperature of about 270 dcg. C. (518 deg. F.) should be permissible above the maximum allowable value for a row of uncoolcd blades made from the same material. The degree of cooling achieved throughout each blade was far from uniform and large thermal stresses must result. It appears, however, that the consequences of this are not highly detrimental to the performance of the present type of blading, it being demonstrated that the main effect of the induced thermal stress isapparently to transfer the major tensile stresses to the cooler (and hence stronger) regions of the blade. The results obtained from the present investigations do not represent a limit to the potentialities of internal air‐cooling, but form merely a first exploratory step. At the same time the practical feasibility of air cooling is made apparent, and advances up to the present arc undoubtedly encouraging.
Supersonic Ram‐jet Performance
Authors: Lukasiewicz J.
Published: November 2014

Ideal and practical performance of ram‐jet units in steady flight in the stratosphere at Mach numbers from 1·5 to 4 is examined. The effects of combustion, temperature, altitude, intake and exhaust nozzle design are considered.
Rocket Exploration of the Upper Atmosphere
Authors: Burgess Eric
Published: November 2014

UNDER the auspices of the Gassiot Com‐mittee of the Royal Society a conference on rocket exploration of the upper atmosphere was held at Queen's College, Oxford, on August 24, 25 and 26. The majority of the papers pre‐sented were concerned with the instrumentations and techniques for physical measurements con‐cerning the atmosphere, but in addition there were some papers which outlined the develop‐ment of the high altitude sounding rocket, first using modified V‐2 rockets and then new vehicles constructed specifically for high altitude research.
Torsion of a Multi‐webbed Rectangular Tube
Authors: Wittrick W.H.
Published: November 2014

A PREVIOUS paper by Mansfield considered the problem of the torsion of a doubly symmetrical rectangular box containing a large number of equidistant identical webs. Mansfield overcame the practical difficulty involved in solving the large number of simultaneous equations by an ingenious approximate method consisting of the replacement of the webs by an equivalent continuous medium. This device resulted in the derivation of a simple differential equation instead of the system of simultaneous equations.
A Survey of Experiments on Jet Noise
Authors: Powell Alan
Published: November 2014

The bulk of jet engine noise developed at high powers arises from the turbulent mixing of the jet efflux in the surrounding air, as judged from model experiments, and has a continuous spectrum with a single flat maximum. The high frequency sound arises from fairly close to the orifice, and reaches its maximum intensity at fairly large acute angles to the jet direction. Lower frequency noise arises from lower down stream and its maxima make smaller acute angles with the jet axis. The possible origins are briefly discussed in view of Lighthill's theory and refraction effects. The most intensesound has a wave‐length of the order of three or four exit diameters, and originates between five and ten diameters from the orifice. A semi‐empirical rule of noise energy depending on the jet velocity to the eighth power and the jet diameter squared gives a rough estimate of the noise level for both cold and heated jets. Further noise from heated or supersonic jets may occur through eddies travelling at supersonic speed and so producing small Shockwaves. Model experiments have shown that interaction between shock‐wave configurations in choked jets and passing eddy trains generates sound and this initiates further eddies at the orifice. The directional properties of this sound are quite distinctive, the maximum being in the upstream direction. Methods of reducing jet noise are briefly discussed.
The Library Shelf
Authors: A.D.B.  , E.H.B.  , C.F.B.  , V.D.N.
Published: November 2014

This is another of the growing series of text‐books on gas turbines. The earliest of these were based mainly upon information and experience gained from the rapid development of aircraft turbines, but the application of this power plant to land and marine requirements has also gone on apace since the end of the war, and more and more mechanical engineers outside the specialized aeronautical field are seeking information. For these latter, the present book should be most valuable.
The Library Shelf
Authors: W.A.M.
Published: November 2014

This unusual book gives a combined account of three different branches of dynamics, dealing with particles, fluids and solid bodies. The preface explains the history of the course at the Massachusetts Institute of Technology on which the book is based. When instruction in aeronautical engineering was started at M.I.T., some forty years ago, the branch of the subject that was most fully developed from a rational viewpoint was the theory of dynamic stability. The students, with only an elementary training in mathematics and mechanics, found this theory of stability too difficult to grasp, and a course was therefore started to bridge the gap between the mathematics and mechanics that the students already knew and the complex problems of aircraft stability.
The Fifteenth S.B.A.C. Display
Authors: Noton B.R.
Published: November 2014

EACH September the eyes of the aeronautical World turn towards the S.B.A.C. Air Display and Exhibition with interest unequalled by any other event. It is fitting that the Display is now held each year at the airfield of the Royal Aircraft Establishment, one of the world's most prominent aeronautical research centres. This interest becomes increasingly keen too, as the preview day comes closer, because new prototypes of unorthodox designs often appear a short time before the Show to illustrate the results of years of careful planning, development and research of the particular company. These designs often mould the path of progress for smaller countries without the economic resources to forge the way ahead alone. Most British citizens are very proud of their country's place in aviation today, both in the military and civil fields. This is understood by most foreigners because it is clear that Britain has won a place in aeronautical development second to none.
Wings Under Repeated Thermal Stress
Authors: Parkes E.W.
Published: November 2014

When an aircraft changes its speed or altitude, large thermal strains may be set up in the wing structure; sometimes these are of sufficient magnitude for the accompanying stresses to exceed the clastic limit of the material. During its life the aircraft may suffer a large number of cycles of thermal stress. Under repeated thermal loading it is found that four types of stress‐strain system may be set up: permanent elasticity and shakedown to an clastic state, which are safe, and alternate plasticity and incremental collapse, which are dangerous. The present paper investigates these stress‐strain systems and determines the conditions for their occurrence.
A Swept Cantilever Box Beam with Two Spars and Skew Ribs
Authors: Noton B.R.
Published: November 2014

A two‐spar cantilever box beam with forty‐five degrees sweep and oblique ribs placed parallel to the root clamping section was the subject of a series of static tests. Stress and strain distributions were determined, primarily in a region distant from the root and tip disturbances, to permit a stringent comparison with three well‐known swept wing theories and the simple theory of bending. Torsional and flexural stiffnesses were also measured and compared with these theories. The sequence of calculation for each method is presented and it is found that two of the theories provide accurate predictions of the stresses, strains and stiffnesses. The influence of rivet slip and rivet flexibility on the stiffnesses of the box is mentioned. As a secondary aim of the investigation, the distribution of normal and shear strain has been measured in the cover skin and spar webs at the root connexion. The design of swept box examined has been the subject of research in a number of establishments and a review of this other work is included.
A Swept Cantilever Box Beam with Two Spars and Skew Ribs
Authors: Noton B.R.
Published: November 2014

The notation and equation numbers in the text are those of Hemp's report.
Stress Analysis of Triangular Cantilever Plates
Authors: Mansfield E.H. , Kleeman P.W.
Published: November 2014

The stress distribution in triangular cantilever plates under a uniform normal load and under a tip load is investigated theoretically. Numerical solutions are presented for plates with angles of sweep from 0 deg. to 60 deg. and with tip angles of 30 deg., 45 deg., 60 deg., 75 deg. and 90 deg.
Statical Indeterminacy of a Structure
Authors: de C. Henderson J.C. , Bickley W.G.
Published: November 2014

A SKELETAL structure is defined as one which can be ideally represented by linear (one‐dimensional) members appropriately connected at point nodes. The members are not necessarily straight or in one plane. The term structure will be used to denote a skeletal structure.
Progress in Research on High Speed Flow
Authors: Holt Maurice
Published: November 2014

PARALLEL with the quest for higher speeds in aircraft of the traditional type, there has been a remarkable advance in rocket and missile design in recent years. The German legacy of the V2 gave both East and West a long start in this development, and full advantage of this has been taken in the period of intensive research of the past ten years. Lately the possibility of space travel has made a very profound appeal to people in all spheres and this has caused the pace of research in this field to be stepped up.
Struts of Minimum Weight
Authors: Ayers K.B.
Published: November 2014

IT is intended to show in this article the magnitude of the weight saving which can be achieved on simple struts. It is necessary for any comparison to derive the weight and shape of the solid or hollow strut theoretically most efficient. This can be done most conveniently using the Calculus of Variations and it will be assumed in all cases that the strut is of such a length that bending stresses predominate at the instant of failure and that the ends of the strut are rotationally free.
Panels under Thermal Stress
Authors: Parkes E.W.
Published: November 2014

This paper discusses the problem of a panel attached along two of its edges to heavy members which respond only slowly to external temperature change and thereby prevent its free (hernial expansion, and along the other two edges, parallel to the direction of loading, to light members which permit free expansion. It is shown that the load‐bearing capacity of such a panel is generally small, if buckling is to be avoided, but that much greater loads can be carried in the post‐buckling condition, provided that a small degree of rippling can be tolerated. The paper includes a number of numerical examples, in one of which the concept of a load‐temperature envelope is introduced.
Flight Loads During Combat Training
Authors: Baum Queenie
Published: November 2014

In view of the comparative lack of information available on the magnitude of loads occurring on aircraft used for combat training, V‐g recorders were fitted to several Mustang aircraft of the Royal Australian Air Force in Victoria. The recording period covered 102·5 flying hours, consisting of aerobatics and general flying, dive bombing, rocket launching, etc. The unfactored design flight envelope was not exceeded during this period, the highest load factor of n=7·3 occurring during general flying (duty unspecified) while the highest speed was 422 m.p.h. I.A.S. which was well below the maximum permissible. Consistently high loads were produced during dive bombing—the mean highest load per slide being n=5·36, while 5g was frequently exceeded, sometimes many times on a slide. Rocket launching is a similar manoeuvre although the loads were somewhat less severe. Some air to air gunnery was also practised, and the loads were the least severe during this manoeuvre.
Turbine Disks for Jet Propulsion Units
Authors: Johnson A.E.
Published: November 2014

In the first two parts of this paper attention has been directed to determination of the stresses in a disk as dependent upon elastic and plastic strain, including creep effects which may occur at the rim region. The problem has so far, however, been treated without complication introduced by the blade fastenings and therefore, in effect, the disk has been investigated as far as the base of the blade grooves or slots. It has, however, been realized that the projections forming blade root fastenings present their own problems, differing from those of the disk, and these problems have been left to be dealt with in this third portion of the paper. Nevertheless, in Parts I and II the fact that the root fastenings applied an interrupted radial loading at the outside, and not a perfectly distributed load as assumed in the analysis, was not overlooked.
The Possible Use of Semiconductor Devices in Aircraft
Authors: Brown D.C.
Published: November 2014

SINCE the early years of the last decade a great deal of research has been done on the properties of the new class of materials called semiconductors because their electrical properties lie between those of conductors and insulators. Some of the results of these researches are described in this article, in particular those which are of interest to aircraft engineers. A simple explanation of the mechanism of these devices is given and some emphasis is laid on work done by staff and students of the Department of Aircraft Electrical Engineering at The College of Aeronautics.
Helicopter Rotor Blade Flapping and Bending
Authors: Jones J.P.
Published: November 2014

THE problem of calculating the motion of a helicopter blade presents many difficulties. Probably the most serious is the lack of knowledge of the aerodynamic forces acting on a blade, but a second major difficulty arises when the equations of motion have to be solved. The first and second harmonics may be readily obtained, but the higher harmonics can only be calculated at the expense of considerable effort. This is especially true if the effects of elasticity and varying tip‐speed ratio are taken into account.
The Detection of Fatigue Cracks in Specimens under Dynamic Loading
Authors: Linge J.R.
Published: November 2014

THE application of cemented wires to determine the location of initial failure in static tests on large specimens has been investigated, among others, by R. W. Powell in 1946.
The Library Shelf
Authors: A.D.Y.
Published: November 2014

Transonic flow has been defined as flow in which regions of subsonic and supersonic flow occur each of significant extent, so that across the common boundaries of these regions fluid particles are accelerated or decelerated through the speed of sound. By the term ‘significant’ is here implied significant for the particular problem or flow characteristic under consideration. Hence for problems in which viscous effects are of major interest the flow past a body at any main stream supersonic speed is strictly speaking transonic in so far as a region of subsonic flow must exist in the bounday layer adjacent to the surface. The book under review is confined, however, to the theory of transonic flow of an inviscid fluid, and the main application of this theory is to problems that arise in considering the flow past wings and bodies at main stream Mach numbers in the range from about 0.8 to 1.2.
The Contra‐Flow Gas‐to‐Gas Heat Exchanger
Authors: Turton J.S.
Published: November 2014

THE heat transfer from a fluid to a solid surface may be expressed by the non‐dimensional heat transfer coefficient or Stanton number:
The Support of an Aircraft for Ground Resonance Tests
Authors: Molyneux W.G.
Published: November 2014

The current trend in ground resonance testing is aimed at providing aircraft modes of vibration appropriate to the free‐free condition. To achieve this objective the rigid body frequencies of the aircraft on its supports must be low by comparison with the frequency of any mode of distortion. A minimum frequency ratio of 1:3 is specified. The various types of support in current use are considered in relation to the minimum frequency they are likely to provide. It appears that none are capable of frequencies lower than about 0·5 cycles/sec. For the forthcoming generation of large thin‐wing aircraft with fundamental frequencies below 1 cycle/sec. some further development in methods of support seems necessary. A non‐linear spring system appears to hold great promise in this respect, and one such system is described capable of frequencies less than 0·25 cycles/sec. for a limited range of movement.
The Library Shelf
Authors: J.K.  , C.R.D.  , M.C.W.  , M.A.P.
Published: November 2014

For one man adequately to cover the whole practical and theoretical field of rocket propulsion is well‐nigh impossible: in view of this, the present work has been compiled from the work of four authors, three of whom are Belgian and one (Barrère) French. The whole, which originated in a series of lectures organized by M. Jaumotte, forms a fairly comprehensive survey of the field. Indeed, by its inclusion of three chapters on external ballistics it goes outside the limits of rocket propulsion as normally understood.
The Case for Pneumatics An Examination of the Possibilities of High and Low Pressure Systems
Authors: Wotton J.
Published: November 2014

THE outstanding difference in using a gas as compared with a liquid as a means of transmitting power is the high degree of compressibility which can be achieved in the one and its virtual absence in the other. As might be expected there are instances in both cases where the peculiar characteristic is of value and others in which it is a drawback. In some cases a soft damping action is required for which compressed air provides a suitable medium, while in others a high degree of damping at a controlled rate can best be performed by the use of hydraulic fluid. In applications where complete irreversibility is required by means of the locking of the medium in some restricted space air is virtually useless and in such cases recourse has to be made to some form of damping, either hydraulic or mechanical, which generally adds considerably to the complexity when compared with a straight hydraulic system. Also, in systems which call for small dead beat movements the consumption of compressed air is often unacceptable. On the other hand the medium itself does not constitute a fire risk, is readily replaced in flight in the case of small leakages and is responsible for quite a small expenditure in terms of engine power.
A Proof by Induction of the Henderson‐Bickley Ring Formula
Authors: Booth L.G.
Published: November 2014

HENDERSON and Bickley showed in AIRCRAFT ENGINEERING for December 19551 that the degree of statical indeterminacy of a skeletal structure may be determined from the ring number of the structure.
Complex Stress Creep Relaxation of Metallic Alloys at Elevated Temperatures
Authors: Johnson A.E. , Henderson J. , Mathur V.D.
Published: November 2014

As stated in general terms in a previous paragraph, in the ease of this material the following complex stress relaxation tests were made: two pure torsion tests from initial stresses of 4 tons/sq. in. and 3 tons/sq. in.; two tests having a stress ratio T/S=0·4 and having initial stress values of T=1·6, S=4 and T=1·2, S=3 tons/sq. in. in the two cases; two tests having a stress ratio T/S=0·8 and having initial stress values T=3·2, S=4 and T=2·62, S=3·28 tons/sq. in. respectively; and finally one test having a stress ratio T/S=1·5 and having an initial stress value T=4·5 and S=3 tons/sq. in. (i.e. a total of seven tests).
An Approximation to the Influence Function for Plate‐like Wings
Authors: Milne R.D.
Published: November 2014

A general solution for the small deflexions of thin plates of slowly varying thickness under lateral loading in the form of an influence function is briefly presented. It is known that the influence function may be represented as an infinite series in terms of the eigenfunctions and eigenvalues associated with a homogeneous form of the plate differential equation. It is suggested that the series may give an acceptable approximation to the influence function when summed over a small number of terms when also the eigenfunctions and eigenvalues involved are deduced by an approximate procedure of the Rayleigh‐Ritz type. In order to test this assertion a numerical example is given for a uniform canti‐lever plate and the results are compared with experiment and with similar results deduced by an alternative theoretical procedure. Thus the calculation of a sufficient number of approximate normal vibration modes and frequencies for the plate as normally required for aeroelastic investigations may in this way be made to serve as the basis for a complete analysis of the plate. A simple approximate allowance for shear deflexion of the plate is presented and illustrated.
Structural Design in British Aviation
Authors: Walker P.B.
Published: November 2014

IN the year 1945 aircraft structural design had reached an advanced stage in this country, as judged by all previous standards. The needs of war and the vast expenditure on aircraft design and manufacture had unquestionably forced the pace of progress. On the other hand, war‐time conditions must inevitably have tended to produce an unbalanced growth. Expenditure of money and effort was accompanied by a no less drastic expenditure of technical capital, and really long‐term thinking was unavoidably put aside.
The Library Shelf
Authors: R.D.M.
Published: November 2014

Within the compass of three hundred and seventy pages Dr Pai sets down an account of the theory of compressible flow which is surprisingly comprehensive. Such compactness has its accompanying drawbacks. The style is not always easy to read and smacks of the reference work in many places. The reason is often merely outlined, sometimes too scantily, but mostly with enough depth to enable the reader to grasp the theme of the argument. A bibliography at the end of each chapter is fully sufficient to develop the subject for the interested student. Neither the application of the theory nor its real relation to physical events is given serious consideration but the theoretical limits demarcating approximate methods of solution are carefully set out and analysed. In short the book deals with the theory of compressible flow in a brisk and authoritative manner and Dr Pai clearly derives pleasure from the aesthetic value of the theory for its own sake.
The Effect of a Damping Compound on Jet‐Efflux Excited Vibrations
Authors: Mead D.J.
Published: November 2014

The theory is presented of the increase in damping that can be obtained when a damping compound is added to a simple structure vibrating in a bending mode. Consideration has been given to the use of ‘Aquaplas’ damping compound on a vibrating stringer‐skin combination, and it has been shown that the maximum damping ratio is obtained when the material is applied to the stringer flange over the centre 40 per cent of the pin‐ended length of the beam. A preliminary experimental investigation is described, in which damping measurements were made on a simple structural specimen treated with Aquaplas. A new method was used successfully to determine the damping ratio of a heavily damped system. The damping properties of Aquaplas were evaluated, and some of the theoretical conclusions were verified. Some of the results obtained indicate that a more accurate mathematical representation must be sought for the visco‐elastic behaviour of Aquaplas than is provided by the ‘complex stiffness’ method.
The Estimation of Tail Loading Due to Elevator‐Induced Pitching Manoeuvres
Authors: Richards P.F.
Published: November 2014

This Part presents Appendices I and II which deal, respectively, with the theoretical analysis of the checked manoeuvre and a new simplified method of determining flight loads to cover all pitching manoeuvres, in a form suitable for amendment of civil airworthiness regulations. The latter method also considers additional design cases, including the loading conditions arising from the malfunctioning of an anto‐pilot in pitch: a specimen calculation is also given.
Sandwich Construction
Authors: Heath W.G.
Published: November 2014

An extensive bibliography exists on sandwich construction; it is felt, however, that few of the available papers are readily adaptable for use in aircraft design offices. This paper, whilst based on an existing theory, extends it to include panels with faces of unequal thicknesses and aeolotropic cores such as honeycomb. The various modes of failure are described, and comparisons are drawn between the equilibrium equations and those derived in the theory of solid plates. A very simple equation for the overall instability of a sandwich panel is obtained, based on the concept of ‘width reduction factors’ which make allowance for core flexibility and unequal face thicknesses. Methods are described for presenting these reduction factors' and other important parameters in the form of data sheets, of which examples are given. The panels which are discussed are assumed to be flat, and compressed by a load uniformly distributed across their ends. The edges, which are simply‐supported, are taken to be long in relation to the panel width.
The Avoidance of Ground Resonance
Authors: Price H.L.
Published: November 2014

(i) The Position of the Vertical Asymptotes Vertical asymptotes of the (X, y) curve are given by those values of X which make y infinite. Taking the curve in the form given by Eq. (10), viz.:
Photoelastic Measurement of Surface Strain
Authors: Linge J.R.
Published: November 2014

The technique described in this paper consists of the examination of surface strains in a metal component with optically sensitive material bonded to the component and the analysis of the photoelastic pattern produced under load by means of polarized light reflected from the surface of the metal. The original investigations cover in considerable detail the development of the technique and the results obtained, using the photoelastic materials Catalin 800, C.R.39, and the Marco Resin, S.B.26C, and S.B.28C, in conjunction with light alloy, magnesium and mild steel. The fundamental problem of producing good adhesion between the photoelastic material and the metal surface coupled with satisfactory light reflexion from the latter comprised the major part of the initial investigations. Results of the measurement of both elastic and plastic stress concentrations at holes in plates subjected to uniform tension are presented, together with a qualitative analysis of the effect on stress distribution of the variation of the pin to hole clearance in lugs. Owing to the fairly extensive nature of the original investigations it has only been possible to outline the more salient features of the work undertaken. The term ‘Metaplastic’ is suggested to describe concisely the use of compound specimens for the photoelastic applications considered.
Approximate Formulae for Flutter Prediction
Authors: Molyneux W.G.
Published: November 2014

On the basis of certain simplifying assumptions a general equation can be developed that provides an estimate of the flutter speed of a binary system. The equation includes aerodynamic stiffness derivatives, and in the absence of reliable derivatives for oscillatory motion it is suggested that derivatives derived from steady flow measurements can be used. The equation is applied to derive specific formulae for main surface flexure‐torsion flutter. The effects of compressibility on the derivatives for this particular case is deduced, and the derivatives are then used to estimate certain general effects of compressibility on flutter. It appears that many of the generally accepted features of flutter in the transonic region can be established by this approach, but the application of the formula is limited by the lack of reliable data for aerodynamic stiffness derivatives. A concentrated effort to establish these derivative values is likely to be more rewarding in the long run than flutter tests on innumerable models to establish overall flutter trends of limited application.
Design Problems of Ballistic Missile Tank Structures
Authors: Houghton D.S. , Johns D.J.
Published: November 2014

The in‐flight design problems of ballistic missile fuel tank structures are examined and simplified analyses are presented.
Flow Numbers and Their Summation
Authors: Woods W.A.
Published: November 2014

In this article the concept of a component flow number is developed and for a particular example good agreement is shown with an empirical expression. An expression is derived for the flow number of two components in series—this is confirmed by experimental evidence. A rapid computational method for a combined flow number is given and also a single change in a flow path and parallel flow paths are discussed. Conclusions are drawn concerning the dependence of flow number on the physical variables for single and multi‐component flow systems.
Recent British technical progress in aeronautics part One—Structural Design
Authors: Newell A.F.
Published: November 2014

AT a time when the glamour of space travel is capturing the imagination of the aeronautical world it seems somewhat mundane to be asked to report on the progress of the past years‘ achievements. The first reaction is to question if there has been any progress, or is this just ’another' year.