A method is described for determining the inlet and exhaust valve area requirements of a two-stroke cycle engine. It is shown that the valve timings are interdependent and that the final choice is a compromise with a number of other factors.

The Cantilever-Type mechanism often used in large missile erectors is subjected to heavy stresses when raising a missile from the horizontal to the vertical position for launching. In the event it becomes necessary to return the missile to the horizontal position, severe stresses in the erector, and possibly the missile itself may be developed if the lowering mechanism causes the erector to stop suddenly just before it reaches the horizontal position. This note presents a simple matric formulation of the problem which enables one who has access to an electronic digital computer to compute maximum deflections and load factors that occur as a result of a sudden stop.

The evaporation rate of a liquid spray in a turbulent gas stream is of interest in connection with direct contact heat transfer and combustion equipment. Any fundamental approach to this problem has usually dealt with single drops evaporating in an “infinite” atmosphere. The evaporation of sprays from actual atomisers is obviously a more complicated process and few attempts have been made to find in how far single drop data may be applied, or to measure the evaporation from a whole spray.

The main difficulties lie in devising a satisfactory method of measuring the evaporation rate. Selden and Spencer, injected the liquid into a bomb filled with hot gas under pressure and measured the decrease in pressure with time on a special indicator.

The calculator is a device in slide rule form for assisting in the design and stressing of flat rectangular panels in shear.

In the Incomplete Tension Field theory, the ratio q/qb becomes an important factor, where

q applied shear stress (lb./in.2)

qb shear stress at which panel first buckles (lb./in.2).

This ratio is normally evaluated by use of the formula

qb = KE(t/b)2

where E Young's modulus (lb./in.2)

t thickness of panel (in.)

a length of longer side of panel (in.)

b length of shorter side of panel (in.)

and K depends on the value of b/a and the edge conditions, and is normally obtained from R.Ae.S. Data Sheet 02.03.01.

This method becomes laborious when dealing with large numbers of panels.

By the use of the Calculator, q/qb may be found quickly, with no unnecessary paper work.

The buckling of skewed plates with clamped edges and under externally applied shear, and skewed plates with simply-supported edges but with both externally applied axial and shear loading have been considered previously. It is the purpose of the present note to consider the buckling of simply-supported rhombic plates under externally applied shear as shown in Fig. 1.

While the use of blade lacing wires or shrouding is not altogether common in gas turbine practice, occasions may arise when their use is desirable, and the purpose of this note is t o present a method whereby the vibrational characteristics of a number of blades wired together may be conveniently found.

The free and forced vibrations of a multi-rotor system where one section of the shaft has a nonlinear elastic characteristic are considered in this paper. For any frequency of steady vibration the system is reduced to an equivalent rotor at either end of the nonlinear section. The vibrations at all points are assumed to be one-term approximate solutions and the amplitudes of steady forced vibration are determined by a method outlined by the author in an earlier paper.

Ram-jets in Great Britain have, until now, been associated with Guided Missiles and, for this reason, tight security regulations have been in force. In fact, it is only recently that it has been possible to talk about ram-jets at all. Even now, quite a number of features in these engines are classified and, for this reason, some portions of this paper may appear perhaps a little thin and inconclusive, but I have done my best to discuss the subject as fully as possible.

It is now generally known that the work of the Bristol Company has led to the adoption of the Thor ram-jet engine for production by the Ministry of Supply but security restrictions remain and in this lecture I have drawn upon general experience and thoughts in this field and avoided giving information directly related to a particular engine. In these circumstances, of course, the choice of any operating condition for the purpose of giving form to the lecture has had to be a purely arbitrary one.

The dimensionless thrust generated by supersonic flow through a convergent-divergent nozzle is given by Ref. 1,

1

which takes its optimum value, bmax when pe = pa.

For ideal one-dimensional flow, the relationship between Ae and pe is given by

2

and the optimum dimensionless thrust by

3

Where4

From equations (2) and (3), the constant D in equation (1) can be evaluated and thence the thrust of an ideal nozzle at any pressure ratio provided that no separation occurs.

Equations (2) and (3) are tedious to evaluate and it is not easy to estimate the effect of changes in γ.

Reports of noise effects on the rear fuselage structure of large British aircraft indicated that one might expect noise damage in this region on the Vickers Supermarine Type 544 aircraft. It will be seen from Fig. 1 that the jet efflux from each engine passes close to the fuselage side and under the tailplane. The fuselage structure proper is, however, protected from the heat and noise effects at the jet efflux by a fairing which is insulated at all attachments. This fairing, by virtue of its shape, is called the “ pen nib. ”

Tables of the characteristic functions of certain types of uniform beams were published by Young and Felgar in 1949. The functions concerned represent (to suitable scales) the principal modes of free flexural vibration, although their uses are far more extensive than is implied by this. Some of the uses to which they can be put are mentioned in Ref. 1 and others are discussed by Felgarand Bishop;they cover both statical and dynamical problems and relate to beams, plates and shells and include problems of elastic instability. In fact these functions can be used in series representations in the same way as circular functions are used in Fourier series.

One of the main uses to which these characteristic functions may be put does not appear to have been described in print, although the relevant formulae are quoted in Ref. 2. The functions can be used in vibration analysis to shorten calculations, sometimes leading to very considerable savings of labour.

An estimate is made of the “ground” interference effect of the deck of an aircraft carrier. It is shown that in the extreme case of wing span equal to deck width the induced upwash is of the order of 20 per cent less than the usual ground interference value. Thus the landing characteristics of an aircraft should not be markedly affected.

It seems that there should be a difference between landing an aircraft on a stationary aircraft carrier and on the ground, due to modification of the ground-interference effect by the finite width of the carrier deck, particularly if for some reason large aircraft are to be used. In this note an estimate is made of the magnitude of this effect.

In the early stages of preliminary design, it is essential to have a method for the comparison of aircraft on an operating cost basis. The standard S.B.A.C. method is too lengthy and, in any case, demands a greater amount of data than is usually available in the early design stages.

The formula presented in this note is an extension to the ones presented by the author in the January 1955 and November 1956 Journals and is more accurate in that it provides for variation in aircraft first cost, type of power plant, speed and range.

It is submitted that the formula gives a reasonable first estimate, suitable for early design comparisons, and that the few parameters required are normally available at the earliest stage of the design.

There are two types of shock loading to which aircraft components are subjected, namely: medium shock loads which can heavily damage equipment; and shocks of high impact, such as those imposed during crash landing, causing the equipment to be torn loose from its mounting, with danger of injury or even death to aircraft personnel.

An impact shock machine has been installed recently in a laboratory for studying this important problem. The machine is capable of providing calibrated shock tests up to a maximum peak acceleration of llg, and of simulating the shock loads normally experienced under everyday operating conditions. Apparatus being tested is mounted on a frame bolted rigidly to the table of the impact testing machine, which has been designed to take specimens up to a maximum weight of 400 lb., with maximum overall dimension equivalent to a cube of 30 inches side. A specimen under test is dropped from a maximum height of 5 ft., falling freely.