The ability of the helicopter to hover and therefore to take-off and land in confined areas has proven to be of significant value in an increasing range of applications. Rotorcraft have now established a significant role for specialist aeronautical applications both in the civil and military field.

Figure 1(a) shows a graph of the increase of helicopter usage in the civil market. To the traditional roles of point to point transport and special purpose public service operations has been added a massive increase in energy related use, particularly for off-shore oil exploration. Present fleet growth rate in the civil area is about 15% p.a. There is no sign that this demand will abate. There has also been a substantial increase in helicopter use on military operations, as illustrated in Fig. 1(b). Helicopters now account for between 40–50% of all service aircraft (excluding training and liaison) in both the United States and Britain. The flexibility offered by the helicopter has been critical in its tactical value for land operations. The ability of the helicopter to operate from small ships at sea in all weathers, and at night, has provided it with a unique role in naval applications. In Britain over 80% of naval aircraft are now helicopters.

Before 1800 Dr. Johnson observed that ‘the age is running mad with innovation’ and ‘every Master Manufacturer hath a new Invention of his own and is daily improving on those of others’. By the middle of the 19th century this first industrial revolution had made Britain the world leader in the application of steam power, in railways and in the output of coal, iron, steel, cotton cloth, and other manufactured goods. Yet by 1886 the Commission of Enquiry into the Economic Depression stated ‘We are no longer alone. More active rivals with better equipment are springing up and leaving us behind’. Between the turn of the century and the First World War, some of those rivals—in particular the USA and Germany—had eliminated our earlier lead and had gone ahead in key industrial sectors.

The overall objective of design against fatigue is to achieve adequate safety and reliability for minimum structural weight and, having this end in view, the fatigue performance of an aircraft structure is a major consideration in the design, testing and operation of an aircraft. This has not always been the case, indeed until the early 1950s the design of aircraft structures was based almost entirely on strength considerations with little regard to fatigue. However, in the decade following the Second World War a series of accidents both in the military and civil field, culminating in the Comet disasters, focused attention on the need to consider the problem of fatigue in design and provided the climate of opinion to support requirements for much more extensive and expensive full scale fatigue testing than had been contemplated hitherto. Since that time, advances in safety and reliability have been achieved in the face of customer requirements for major increases in overall fatigue life and for higher standards of day-to-day reliability of the structure. For example, in the military field a required fatigue life exceeding 6000 hours would not be exceptional now for a combat aircraft (Fig. 1) as compared with a life in service of about 1500 hours for such an aircraft in the years immediately following the Second World War. On the civil side, whereas lives of about 20 000 hours would have been considered adequate in the early 1950s, operators now require lives in excess of 60 000 hours. The European Airbus shown in Fig. 2 typifies such aircraft currently in service. Both military and civil aircraft are now expected to be in service for 20 or more years.

Although 2000 AD is but 20 years away, even so this is a long period in terms of the rate of recent technological development. My remarks about the possible future state of this subject must therefore be somewhat speculative. The projections will be based, however, on research carried out over the past 10 years, and I hope this will provide an element of usefulness.

I shall refer to both agricultural and forestry crops. Our most extensive agricultural experience has been with cotton and its pests in the Sudan, particularly the cotton bollworm moth; and with cereals in the UK, particularly cereal aphids. Our forestry experience has been with softwoods and the spruce budworm moth in eastern Canada, and with lodge-pole pine forests and the pine beauty moth in Scotland. In terms of techniques our experience has ranged over ground-based and airborne radars, a full range of ground and airborne meteorological instrumentation, the study of insect flight behaviour by sensitive infra-red opto-electronic devices, the turbulent dispersal of spray droplets and their deposition on foliage and insects, the study and quantification of insect population dynamics, and the use of many biological techniques, including suction traps and light traps.

The purpose of this paper is to give a fairly detailed description of where carbon fibre composites are most likely to be used in the structures of future military aircraft together with an indication of the structural configurations.

I feel very privileged to be asked to give the 26th R. J. Mitchell Memorial Lecture in honour of a great man whose work and designs inspired many of us in our youth. My lecture tonight covers a period of time similar to that which elapsed between R. J. Mitchell’s death and the first Memorial Lecture by Joe Smith in 1954. In this period, which covered the Second World War and the immediate post-war era, the activities of the British industry were manifest with a proliferation of designs and immense technological and radical advances such as the introduction of the jet engine, the swept wing, early supersonic flight, etc.

It was a period when the evolution of new designs—while led by men of inspiration, vision, genius and persistency like Mitchell—became more and more the work of teams ever increasing in number.

Although normal flapped and /or slatted wings may be considered as having a variation of camber because of the deflection of such devices, a variable camber airfoil is considered here as a mechanical unit employing flexible leading and/or trailing edges, thus eliminating surface discontinuities, but otherwise operated in the same manner as the more conventional devices they replace and is simply illustrated in Fig. 1 (i.e. flaps and ailerons on the trailing edge and slats or droop on the leading edge). The use of varicam trailing edge systems for lateral control implies that such systems should preferably be capable of both up and down (i.e. differential) movements.

It is traditional in looking to the future to analyse past experience. In this paper the processes of development of 25 UK combat (or fighter-bomber) types covering a period of 45 years have been analysed and compared with available data on 20 US types.

In this analysis:

1. (i) Date of the project has been taken as date of Instruction to Proceed rather than the more usual first flight or entry into service dates, as it is felt that this more accurately represents technological projections involved.

2. (ii) Of necessity aircraft empty weight has been used as a basic parameter. While AMPR weight is more conventional in modern estimating, it is impossible to obtain such data for older types, but in a broad review such as this empty weight would seem to be an acceptable parameter.

3. (iii) Costs have been corrected to 1978 monetary values using curves deduced from cost of living and aerospace product data for both UK and USA.

My department's involvement in flight simulation started in the early 1960s under Professor Stephens. At that time, and even more so subsequently, what I think is an unusually high proportion of our staff had previous experience either as pilots, or in flight testing. Since 1965 we have operated our own light aircraft, primarily for flight test work at undergraduate level. In addition our links with the University Air Squadron are strong and the number of our students who are members is also exceptional. Every project described here, apart from one, was done by a pilot, or ex-pilot.

Our first project, for a PhD, was somewhat exploratory in nature, consisting as it did of three largely unrelated investigations. The first of these, suggested by two accidents involving aircraft on ground controlled approaches (GCA), was tackled using a fixed-base simulator consisting of a spring-loaded pitch control and throttle, and the usual flight instruments, all under a hood. I should explain that the GCA, particularly favoured by the military as an approach technique, consists of precision ground radar giving information of azimuth and elevation relative to the desired line of approach, to a ground controller. The ground controller then passes instructions to the pilot such as: ‘You are 30 ft below the glidepath. Adjust your rate of descent and turn left three degrees.’

There are many examples in his two Alice books where Lewis Carroll, perhaps unwittingly, provides analogies with the world of reality. The lines quoted above are often used to portray the rapidly changing scenario in which we struggle to maintain the status quo of our social and political lives. The same is true in the world of structures: the scenario continually shifts as we discover new hazards which threaten our products. Aircraft speeds have increased, operators have demanded longer service lives, new materials have been introduced with their own susceptibilities, and so we must develop more comprehensive design requirements and better design techniques to ensure that each new aircraft maintains the existing standards of airworthiness—or at least the standards we imagine to exist.

By inviting me to give the 25th Henson and Stringfellow Memorial Lecture the Committee of the Yeovil Branch and the Lectures Committee of the Main Society have done me an honour which I deeply appreciate and I hope that what I have to say may be sufficiently novel and interesting to do justice to this important occasion.

My subject is the story of the mild obsession which first aroused my interest in rotating wings and which has guided my steps at critical times over the past 50 years— a benign obsession in that for most of that time there was nothing that could be done about it so that it has not hampered the engineering work needed to implement the policies of my various employers. It was a matter of great good fortune for me that at just the right time some of the concepts underlying this lecture had hardened sufficiently for Westland to agree to my concentrating on this study during the last few years of my career.

High authority automatic flight control systems are now in wide use in both transport and combat aircraft. These have required the development of failure survival system architectures, and techniques in safety assessment to ensure that the risk of fatal accidents attributable to the automatic control aspect is acceptably remote.

Most of the current systems are analogue in nature, and employ sufficient redundancy to survive at least one failure during operation. Future systems will employ quadruplex or triplex-monitored architectures, capable of surviving at least two failures, and will be mainly digital in concept. The design and safety assessment techniques developed for analogue systems have been adequate for current systems, but the new digital technology and more extensive use of systems in safety critical applications will demand further development of the various aspects involved.

A major contribution to the design and safety assessment of safety critical systems was made during the past two decades in the programmes for the development of automatic landing for civil aircraft, culminating in the system in the Anglo-French Concorde.

Twenty years ago, the electronic valve gave way to the transistor; now the transistor as a discrete component has been replaced by the integrated circuit, and micro-processors are emerging as cheap, reliable and basic elements of electronic architecture.

Each step has yielded a major reduction in the size of equipment needed to achieve a particular function or to improve performance—but in spite of miniaturisation, an increasing volume of avionics has been incorporated into succeeding generations of aircraft as requirements for greater precision and safety have arisen.

Application has already provided striking improvements in the quality and ease of communication and navigation, which in turn have brought about the demise of the dedicated radio operator and navigator. The trend will continue with more automation of flight control and system management, leading to two-crew operation of most short and medium range aircraft—providing, of course, that the cost of ownership of additional equipment is less than the costs of the displaced crew member, and that flight safety standards continue to improve.

Criteria for the design of helicopter rotor blades has been long established but the introduction of composite materials opens up new means of achieving these.

As an introduction to the subject I would like to look briefly at the design considerations under the headings:

1. 1. Aerodynamics

2. 2. Dynamics

3. 3. Strength

The emergence of active control technology (ACT) as a design feature of future combat aircraft raises three fundamental requirements (a) the identification of those areas where active control is likely to make for more efficient designs (b) the development of a capability to produce system hardware and software satisfying the stringent integrity requirements which the envisaged ACT applications demand, and (c) the development of a capability to implement successfully the ACT benefits, emerging from (a), by means of appropriate control laws.

This paper is concerned primarily with Item (c). Subjects considered include the design of control laws for fast target acquisition and precise tracking, the design of ride-smoothing systems, control laws for manoeuvre limiting at high angles of attack, and flying qualities problems associated with aerodynamically-unstable air-craft.

The design of control laws takes place through a series of steps including initial computer-aided studies followed by ground-based simulation with the pilbt-in-the-loop and ultimate validation (probably with re-tuning of control-loop parameters) through flight test.

Control of agricultural pests and diseases has been attempted for well over one thousand years, but it is only during the present century that the means have been available to combat the problems on a large scale by the use of pesticides. The contribution which pesticides have made to the reduction of crop losses is enormous. However, the fact that significant losses of production still occur shows that they are not a complete or simple answer to the problems.

When used in the broadest sense the term ‘pest' applies to a wide range of plant and animal organisms which adversely affect the crops grown by man. Attention here will be restricted to invertebrate pests and crop diseases.

Many aircraft in service today have already achieved lives considerably greater than those originally anticipated by their designers. One thinks of aircraft like the Douglas DC-3, still going strong in many parts of the world after 40 years. Even aircraft like the Vickers Viscount, the world’s first successful turbo-prop air liner, are much ‘longer in the tooth’ than one might at first think; the oldest airframe still in regular service left its makers 27 years ago. Geriatric is the word which has been coined to describe such aircraft and, based on its dictionary definition of ‘care of the old’, the description is probably apt. However, this term is often wrongly thought of as synonymous with senile which, from its dictionary definition of ‘feebleness of old age’, is most inappropriate to such aircraft. It is interesting to examine first the longevity of current aircraft, secondly the application of the science of geriatrics to them and finally the means by which the expectation of life of new types of aircraft may be increased.

The question posed by the symposium title is one of concern to many psychologists, especially those with interests in the study of high levels of human skill. The area of flight simulation does however present a number of challenges in terms of research questions, which are at present only partially answered.

There are at least three areas of simulator use where psychologists have interests and have a part to play:

• Man-machine system development

• Research simulators

• Training simulators.

In the early 1970s considerable attention was being given to the possibilities of short-haul aircraft aimed at operating into or near city centres. There was a belief that suitable airfield sites could be found if field lengths no greater than about 2000 ft-3000 ft were required into which the aircraft could operate quietly with steep climb out and approach.

In 1781-84 Carl Friedrich Meerwein (1737-1810), a South German builder and architect to his namesake, Karl Friedrich, Prince of Baden, worked on ideas for a practical ornithopter. Living in comparative obscurity in Emmendingen, a small town near Freiburg, he began in August 1781 by building a simple pair of ellipsoidal wings. He might have taken the matter no further had his interest not been caught by reports of Pierre Blanchard's abortive flying attempts in Paris, published in a Basel journal in July 1782. During the next two years, when everyone in Europe was talking about the French balloonists, Meerwein decided to set out his ideas for a heavier-than-air machine. Published in Basel in the summer of 1784, his book was widely read. A modified French version was published in the same year and reissued in 1785, and in 1812 a Portuguese translation appeared.