A method is described by which blades of aerofoil section can be manufactured on a laboratory scale. Emphasis has been placed upon cheapness, rapid production, and the ability to obtain an accurate representation of the blade profile for a large aspect ratio of 3·5. In addition, for a series of experiments with a cascade in water, the blades were to be made from a material which did not require the use of a protective paint on the surfaces. To satisfy the above requirements a casting process was adopted, and the blades were made from a plastic resin material. Although the discussion presented is confined to the production of blades, the method can easily be extended to the manufacture of impeller hubs, fairings, nozzles, and so on.

Wind tunnel measurements of the auto-rotation characteristics of Lanchester’s “aerial tourbillion” are presented in the form of tip speed plotted against wind speed. Three configurations were tested, a 10.94 inch diameter model with and without a cowling, and a 7.50 inch diameter model without a cowling. All showed a minimum wind speed for auto-rotation, dependent on friction at the shaft. At each wind speed above this value, there were two equilibrium rotational speeds, an unstable one, giving the required initial rpm for auto-rotation, and a higher stable one, the auto-rotation speed, which with increasing wind speed rapidly approached proportionality to the wind speed.

Fairly good agreement with an approximate blade element theory was demonstrated, the best agreement being obtained with the measurements on the model with cowling.

The solution of a set of m ordinary linear differential equations of the nth order having variable coefficients can be provided by the use of a set of m2 indicial admittances and the solution is derived from that given by the use of impulsive admittances. The indicial admittances are easily derived from the impulsive admittances and vice versa.

An “indicial admittance” is a function representing the response of a system to an applied “input” in the form of a “unit step function” and the concept is due to Heaviside. When the indicial admittance is known, the response to an input which varies with time in an arbitrary manner can easily be found. Similarly, the response can easily be found when the “impulsive admittance” is known, where this is the response to a unit instantaneous impulsive input.

The safety of civil aircraft is regulated through a process of airworthiness certification and the application of operational regulations. The main elements of airworthiness are:

• (i) certification of the design,

• (ii) compliance with airworthiness requirements,

• (iii) maintenance and reaction to service problems -continued airworthiness.

The airworthiness requirements are developed through a process of discussion and consultation with all interested parties. Whilst the result is largely a consensus view, the ultimate authority rests with the airworthiness authority. In recent years there have been increased efforts to reduce national differences with the aim of producing a single international code. At present there are two, with European and US international pressures tending to work against ‘improving’ requirements unless there is a clearly recognised need.

Airworthiness cannot be achieved by regulation. Regulation can establish a framework within which all who are concerned with the design, construction and operation of aircraft can work, and can set boundaries of responsible behaviour. Within that framework airworthiness can only be achieved by the actions of constructors, operators and authorities, and it is the management of those actions which is the subject of today’s discussions.

In a search for a rational basis for a transport-economical comparison of jet and airscrew propulsion of aircraft, a method has been developed which is generally applicable for evaluating any kind of propulsion of aircraft, as well as the efficiency of any principle or type of aeroplane design. The method is based on the assumption that the ratio between the useful load and the gross weight (or empty weight)—when related to the speed —is representative for the overall efficiency of the aircraft, including the power plant, from a transport point of view. General equations have been deduced for this useful load ratio as functions of, in addition to the speed and altitude, all major design parameters, as wing loading, power loading (or thrust loading for jet aeroplanes), specific engine weight, specific fuel consumption, parasite drag coefficient, effective aspect ratio, and two structural weight coefficients. This has been possible by the deduction of a formula for the gross weight, which appears to be usable even for general analysis of other aircraft performances, whenever the useful load has to be considered.

The method presented has been applied in this paper particularly for a comparison between jet-propelled aeroplanes and piston engine-airscrew aeroplanes. This has revealed that pure jet propulsion seems to be superior to the conventional system at speeds as low as 200 to 300 m.p.h., depending upon the duration in hours of flight and the detailed assumptions made.

Lack of accurate data for the gas turbineairscrew combination has prevented the writer from making a closer investigation of this system, but a preliminary study of the same kind seems to indicate that the turbineairscrew aeroplane—although for most purposes definitely superior to the piston engine aeroplane—is inferior to the pure jet aeroplane for durations up to about two hours of flight. If, however, all the mechanical complications involved in retaining the airscrew are taken into consideration, it appears doubtful whether the turbine-airscrew system will be any more than an intermediate step in aeronautical development. At the best, it might remain only for extremely long ranges, or transport of cargo at comparatively low speeds.

The conclusions drawn are based on the present stage of development of jet engines, but naturally it will take at least some three to six years before the jet aeroplanes contemplated are built and put into service.

Box beams, built up essentially with flanges and webs are widely used in aircraft construction and much has been written about their calculation. But often assumptions are implicitly made without reason. The first aim of this paper is to point out which assumptions must be chosen and why, and to show what results may be expected from them. The calculations are then developed in the. cases of the quadrangular box beam and the wing with three spars (redundancy of the first degree).

I want this evening to present some reasons for believing- that we can build successful aeroplanes of enormous size, and, what is more important, that they will not be merely monuments to a desire for the gigantic.

In the past, bold computers have defined upper limits to the size of aeroplanes. Their prophecies have varied, and most of them have been belied by practical achievement. Their arguments were usually based on what has been called the “ Cube Law ” or the “ Square-Cube Rule.” This rule, though it has apparently proved misleading, is indeed correct when properly applied, and it forms a convenient point from which to begin an enquiry into the feasibility of the giant aeroplane.

Before we begin, let me say that this paper is not a catalogue of engines, their bores and strokes, their output and weight. These aspects have been well covered before and are well recorded.

However, engines will figure prominently because that was the business of de Havilland Engines and our fortunes or misfortunes followed their pattern. However, instead of rigorously following the historic trail I prefer to pick out some of the landmarks and to outline some of the problems we met on the way. There may be a few anecdotes and something about the people who took part.

To begin at the beginning, we must start with Geoffrey de Havilland, who wanted to fly.

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.

A design procedure has been developed to generate aerofoil shapes for prescribed pressure distributions in an incompressible viscous attached flow. It is based on the method of singularities, originally proposed by Chen and later modified by Kennedy and Marsden, for inviscid flows. The classical approach of adding the displacement thickness of the boundary layer and wake to the aerofoil contour is used to account for viscous effects. Several numerical examples are worked out and are compared with the inviscid flow results. Significant changes in aerofoil contours due to viscous effects are observed and these are discussed.

An aspect of structural design which is becoming increasingly more important is the behaviour of a structure when it is subjected to random pressure loading. Random pressure fields can be encountered in several different ways, two of the principal sources of such fields being the noise emitted by a jet, and the fluctuating pressures in a turbulent boundary layer. Many jet-propelled aircraft have suffered secondary structure fatigue failures in those parts of their structures near to the jet stream, and it is not unlikely that certain failures of panelling in engine intakes have arisen because of vibrations set up by the turbulent pressure fluctuations in the boundary layers at the walls.

Before making an appreciation of present knowledge about a single metal, it is not inappropriate to say something of all metals, for the ever-increasing tempo of material civilisation has largely depended on man's increasing knowledge of these constituents of his World. His first discovery in this field was copper. To it and to its alloys he gave an exclusive allegiance for some 100 generations, then about 3,000 years ago iron became, and still continues to be, the predominant metal of his needs.

In the eighteenth century, when alchemy finally gave way to the logic of scientific thought, the metals employed by man for purposes other than currency and decoration were practically confined to iron, copper, tin, zinc, mercury and lead. Today, when over seventy metallic elements are known, only a small number of these are used by the engineer.