This paper is concerned with the rolling resistance, or drag, of an unpowered pneumatic-tyred wheel rolling at high velocities in soft soil. Its application is to undercarriage design for aircraft intended to operate from unsurfaced airfields, and to the inverse problem of predicting the performance of existing aircraft in such conditions.

A practical application of two-dimensional subsonic bluff body flow research can be seen in the design, construction and positioning of tall slender buildings. Similarly, from a three-dimensional viewpoint, drag reduction and vortex control is an important factor in the latest road vehicle designs. From just these two examples it can be seen that the problem of flow about a bluff body is one of major practical importance, while at the same time being of great theoretical interest. However, despite many years of extensive testing, there has been little progress made on the theoretical investigation of turbulent base flows since the foundations laid down by Kirchhoff and von Karman. The non-steady processes in the wake, in particular the complex dynamics of vortex formation, have proved to be problems of formidable size.

There are two main reasons for the modern resurgence of interest in airships. The first is that it can have a greater endurance than any other flight vehicle. This makes it particularly suitable for such offshore tapestry duties as fishery patrol and oilfield surveillance. The second is that it does not require power to sustain lift. It can thus transport a given load with a low expenditure of fuel which is continually rising in price.

With the achievement of a man powered flight across the English Channel by Bryan Allen flying the ‘Gossamer Albatross’ aircraft in 1979, attention is now centred on new performance objectives for man powered aircraft.

In the long term it is widely recognised that man powered flight must develop as a sport and this requires an improvement in the design and construction of the necessary aircraft. It is anticipated that this trend will be stimulated in the short term by speed competitions which will encourage the design and construction of compact man powered aircraft.

With such compact machines the prospect of sporting flights for duration no longer relies on the reduction of the pilot's continuous power input, but on the utilisation of help from the atmosphere, in particular, by using dynamic soaring techniques.

In the places in the UK where these things are discussed, there is a reconsideration of the pros and cons of the two axes systems commonly used for aircraft dynamic calculations.

The first of these is a system fixed in the body and moving therefore with it: this system is referred to as ‘body axes’ and is used by the ‘stability and control’ specialists for assessing rigid aircraft behaviour.

The second is a fixed inertial frame fixed in the earth and is used by the flutter specialists for assessing a variety of behaviours of the flexible aircraft. It is the purpose of this paper to point out the very simple correspondence between these two systems in the case of small perturbations from an equilibrium position of the rigid aircraft flying straight and level. The first section presents unpublished work from the Vickers Aircraft Company’s files done in 1952 which is confined to the symmetric motion at constant speed (i.e. with the phugoid suppressed).

Wind energy has long been recognised as a potentially abundant source of clean and renewable mechanical and electrical power. History records that wind energy has been harnessed by man since about the year 2000 BC when windmills were used for energy production in Babylon and China. An ancient Persian vertical-axis windmill of about 7th century vintage is shown in Fig. 1. Windmills appeared in Europe in the 12th century and flourished until the 19th century as one of the few forms of rotary mechanical power. The Dutch windmill achieved lasting fame as the subject of paintings and etchings by the Dutch Masters including Rembrandt and van Ruisdael. Rembrandt's etching ‘The Windmill’ shows the fine detail of a 17th century windmill in Amsterdam.

The final versions of Dutch and English windmills were relatively sophisticated machines, well suited to the tasks of grinding grain and other materials, pumping water and sawing wood. Steam power came to displace wind power in the 18th century, and windmill numbers diminished rapidly during the late 19th and early 20th centuries. Nevertheless, working examples of traditional windmills can still be seen in Holland, England and on the Greek islands.

In the design of contraction cones for wind tunnels little account appears to have been taken of the influence of compressibility on the performance; the rules of thumb resulting from experience in low-speed wind tunnels are applied regardless of the speed range being considered. This is not surprising in view of the lack of understanding of the complex processes in the development of the stream turbulence through a contraction cone. In addition to the dominant process of the distortion of the vortex lines, the flow is influenced by decay, by the interchange of energy between components both because of the tendency to isotropy and because of the curvature of the flow, and by the apparent turbulence created by turbulent wall boundary layers. Eventually methods of turbulence modelling should be able to calculate the flow but meanwhile it is worth examining the predictions of rapid distortion theory.

A stiffened panel, designed so that failure in compression will occur afterinitial buckling, suffers a loss of axial stiffness due mainly to buckling of the skin between stringers and a consequent loss of flexural rigidity of the panel as a whole. The stringers will then carry an increasing proportion of the total compressive load, provided that the stringers themselves are of sufficient buckling resistance. Failure — due either to flexural buckling of the complete panel or to some other mode of stringer failure — can occur at a load substantially in excess of skin buckling. Behaviour of this kind is commonly found in very light structures for which it may be desirable to concentrate the load carrying capacity in certain discrete members, with a minimum gauge skin in between. However, a post-buckled design may also be preferred in rather more heavily loaded structures, in an attempt to reduce the loss of efficiency in a practical design when some restriction on, say, minimum stringer pitch is imposed. The purpose of the present series of tests is to investigate the post-buckled efficiency of a particular family of Z-section stringer-skin panels, of a design representative of current practice, with a stringer pitch chosen to be close to one-third of the effective panel length.

The basic information required by the pilot of any airborne machine is the same, regardless of the type of machine and the method it uses to counteract gravitational force. This information falls into two categories: firstly there is the information the pilot needs to ensure the safety of the machine (and of his own neck) when leaving the earth's surface, operating in the alien environment above it, and returning to the surface in an orderly fashion; secondly there is the information the pilot needs in order to turn flying into a useful activity, by being able to navigate safely and economically between defined geographical points.

Into the first category falls all the information relating to the functioning of the machine, to its attitude and motion relative to the earth, and to its speed through the air.

In this paper, the author seeks to present in easy-to-understand diagrams the effect of external loads on the pretensioned bolt in a bolted joint. In most cases, bolted joints are tightened up with little thought for the size of the external loads that may later be imposed upon them. Since external loads always change the preload in the bolt, it is important to know by how much the bolt load changes. Too much preload leaves too little margin for the external or working load; too little preload and the cyclic stresses cause the bolt to fatigue, assuming the bolted joint is subjected to frequent working loads. No two bolts are alike, even under the most rigorous quality control production methods, but with more sophisticated nut and bolt tightening equipment coming on to the market, better results can be achieved. The use of these diagrams will help engineers and designers understand what is happening in the bolted joint.

The College of Aeronautics has a considerable interest in composite materials, and in their application in particular to aerospace vehicles, over a number of years, and during this time we have conducted several research programmes on these types of materials.

During recent years, an area of research which has attracted our interest is in the application of composite materials to light aircraft, forming part of a more general study of light aircraft which has resulted in our constructing and testing aircraft in this category on two occasions in recent years.

Some of the work on these programmes has been conducted by students at Cranfield studying for higher degrees, and I acknowledge my indebtedness to them for some of the results presented in this paper.

I find that there are three clearly defined themes appropriate to this occasion, so rather than pick just one I decided, at the risk of being rather superficial, to attempt to cover them in one lecture.

Obviously I must start with a short historical review of Warton Division from 1945 to the present date. During which time a major part was played by Sir Frederick Page in the development of the Division. This period starts when he was the technical guiding light of the newly formed English Electric team, through the vital middle period when he was managing the steadily growing complex now called Warton Division to more recent times when he still acted as a sure guiding light despite his much wider responsibilities.

The advent of the commercial jet air liner, two decades ago, and growing public awareness of the noise of aircraft operations, led to the adoption by airlines of two distinct take-off departure procedures. A Standard Procedure for aircraft departures is usually recommended by the aircraft manufacturer, such that the air liner is operated in a safe and expeditious manner. A Noise Abatement Procedure was devised to reduce the noise impact of airline operations in the airport community environs. Generally, noise abatement procedures were thought to increase pilot work load and, therefore, reduce margins of safety, and increase fuel consumption.

In the 1960s, when most of the air liners were powered by low by-pass ratio engines, the noise abatement procedure included a so called cut-back. This procedure included throttling back from take-off thrust (TOT) to less than climb thrust shortly after take-off (during cut-back) to benefit those communities living close to the airport. Subsequently climb thrust (MCLT) would be applied.

The problem of finding the temperature and velocity distribution inside the boundary layer of a compressible flow over a flat plate is a well-known problem which has been discussed by many distinguished investigators in the past five decades.

Excellent reviews of the work done on this classical hydrodynamic problem are available, for example, in the monographs of Schlichting, Loitsyanskii and Stewartson.

It has long been accepted within the aircraft industry and others, that the number of man-hours needed to produce successive units or batches of units decreases. This effect is called ‘learning’; and a plot of the man-hours required per unit set against the production number is called a ‘learning curve’. Similarly a plot of unit cost (at constant economic conditions) against production number is also called a learning curve, since cost is related to the number of man-hours required.

When the production costs of future aircraft are estimated, learning has to be simulated. This is generally done using curves chosen from a standard family of ‘learning curves’ generated by a simple parametric equation; a curve is chosen on the basis that it is the best-fit by the standard equation to the out-turn data from previous similar projects.