There is a peculiar magic in these lines of Sidney Godolphin, penned 300 years ago. I can think of no better introduction to a paper on aeronautical research and design.

Flying is rather a remarkable business, about which we are inclined to get a little blasé nowadays. Few things can tax the engineers' skill more than the design of a modern high performance aeroplane. In its way it represents supremacy in engineering achievement. Let us not take all this too much for granted; and let us remember those gifted designers—no longer with us— who laid the foundations of the art. Among these, the name of Roy Chadwick stands high.

All of us who are intimately connected with aviation appreciate that the introduction of a new era of air transportation—the jet age—will not be accomplished without a tremendous effort in almost every field of the Industry.

There are current problems for which solutions are available but not implemented, current problems requiring new solutions, and new problems associated with the unique characteristics of the jet aeroplane.

This paper is concerned with a method of improving the utilisation of metal cutting machine tools and thus deals with that part of production covered by machining. It is particularly applicable to the Aircraft Industry, where the production of military aeroplanes must be as rapid as possible and the costs of civil aircraft in a competitive market must be kept to the minimum. As it is designed to be used in conjunction with small quantity manufacture it can be of great assistance in development work.

The limitation to the rate at which machining of any part can take place is generally dictated by the rate at which information can be transferred to a machine tool and converted into appropriate slide movements. In large scale manufacture where batch sizes are high, this transfer of information is normally effected by elaborate pre-set tooling arrangements and the cost and time required to prepare this information is acceptable only as the cost per part becomes very small.

A new concept is put forward which should help materially in the design of engine test cells and ground mufflers. It is suggested that a relatively small spreader can be added behind a jet nozzle which changes, the shape of the jet from circular to a long annular slot. The frequency rise which may be obtained in this way is used to reduce low frequency noise, possibly at the expense of more easily attenuated high frequency noise. As a modest example, tests are described on one particular version which gives an attenuation in the most important low frequency range of nearly 20 decibels. It is shown that the back pressure on the engine is negligible even with a cooling flow equal to the engine mass flow. Other applications are discussed and tested, while suggestions for full scale installations are made.

It is well known that when a plane air jet of high velocity blows over a convex surface, such as the upper surface of a lowered trailing edge flap, it flows along the surface, remaining attached for a considerable length; in the case of the flap, it adheres right to the trailing edge. This effect, usually described as the Coanda effect, has been utilised in the attempts to increase lift at constant incidence by “flap-blowing” in which the high velocity air jet is ejected either through slots in the flap shroud, or tangentially out of the flap surface.

The low velocity air stream approaching the flap over the wing upper surface, which in the absence of “blowing” would tend to separate at the flap shroud, is entrained by the high velocity jet, and the incipient flow separation over the flap thereby suppressed. The energy contained in the “blowing” jet can, in addition, also produce “supercirculation.“

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.