The possibilities for technical progress in every aspect of aviation during the first half of this century have indeed appeared as a limitless horizon. Increasingly since that period, as we have moved outward toward the technical horizons, the course has become rougher, and we find ourselves in the foothills with a high and formidable range of mountains looming into view before us.

These figurative mountains are representative of the increasing interface deterrent which we are encountering at the edge of the aviation systems’ advancing fronts. These deterrents include socio-environmental and political impacts, economic factors, and the need, in many cases, for redirection and/or equivalent progress in non-aviation technical systems which interface with aviation development. Specific areas are increasing costs for R & D, increased fuel costs, environmental effects of new aircraft and air transport ground systems, changing requirements and demands of the public, increasing liability exposure, increasing regulatory constraints and conflicts, etc.

Aircraft lift and drag characteristics can be measured in flight by subtracting the components of engine net thrust along and perpendicular to airspeed from the corresponding components of the total aerodynamic force R.

In steady straight flight the flight path angle can easily be measured and consequently the components of R when aircraft weight is known. Measurements in steady-straight conditions, however, are time consuming and furthermore the resulting accuracies are limited due to unavoidable deviations from the nominal straight flight condition.

‘Testing distribution equipment’ is a simple enough tide, deceptively so, and the superficial simplicity of our subject has in my view been misleading and somewhat detrimental to agricultural aviation development. With this remark made, I will now try to justify it and explain why I think that testing is in fact reasonably complex, even though, because the physical mechanisms are usually straightforward, the subject appears to be more simple than it really is.

Firstly, I would like to take a moment to consider the meaning of the two words ‘distribution’ and ‘testing’.

It is to me a signal honour to be invited to give the 33rd British Commonwealth Lecture of this august Society on the subject of the Commonwealth Advisory Aeronautical Research Council. It has fallen to my lot to serve this Commonwealth body from its inception until my retirement a few days ago and, although during most of this period my work for the CAARC has represented only a part of my professional duties, it is a part which has lain very close to my heart.

An abundance of cheap energy has been essential for the growth of civilisation during this century, and, like so many of our resources, has been taken for granted— almost for too long. The title is derived from American folklore and is self-evident. ‘Without energy, can’t travel’ is also obvious; perhaps for today’s lecture a more appropriate slogan could be ‘have alternative energy sources, continue to travel’.

This paper has been written at rather short notice, which has prevented me from going into statistics and detailed figures, as I would have wished. It is therefore given fairly broad brush treatment and concentrates mainly on the larger types of crop-spraying aircraft in the category of around 6/7000 lb all up weight. This is where the engine situation is most critical and the need for a satisfactory powerplant which the operator can afford is most needed.

My only claim to be able to offer ideas or suggestions and perhaps some prognostications for the future is by associating with a number of Ag operators over the last four years, mainly in the States and particularly at the last four National Agricultural Aircraft Conventions in Florida and at Las Vegas; I have therefore no intention of being pontifical. Another reason for caution is because most of my past experience with engine installations has been with sophisticated aircraft, such as jet fighters, where I have had the good fortune to be supported by a team of technical experts and colleagues.

Shorts’ experience in the world of so-called small airliners began with the design, development and manufacture of Sky van (Fig. 1), a 12 500 lb STOL transport aimed particularly at the expanding market provided by the developing nations. To date some 120 have been sold. The disposition of these aircraft around the world is shown at Fig. 2. Two competitive aircraft of roughly the same size and developed at the same time are the Canadian de Havilland Twin Otter and the American Beech 99, the former having captured by far the largest slice of the market.

With this background the Company has naturally retained a keen interest in the business prospects afforded by the third level airline market. Indeed, the prospect of maximising the non-recurring investment already made in Skyvan provided a spur both to continued project design and to market studies in that segment of the airline industry bounded by the Islander at one end and the DC-3 at the other—say 10 to 30 seats capacity.

One of my responsibilities is the day-to-day supervision of the various pilot examiner authorisations issued by CAA. These authorisations permit the holder to carry out various tests pursuant to Sch. 9 of the ANO. (For the benefit of those who think that Sch. 9 has something to do with income tax let me hasten to add that Sch. 9 lays down the requirements for licence certificates of test—aircraft type tests and instrument rating renewals.)

As you are aware ever increasing numbers of those Sch. 9 tests are conducted on simulators, or more correctly—simulators approved for that purpose. This creates two areas of input from CAA—approval of the device and authorisation of the examiner. The former is normally approved annually and the latter every three years.

Modern technology places great demands on structural material performance. Until the 1950s, structures were invariably designed according to safe-life principles, for which a crack-free service life was required and assumed. However, the tendency to much longer utilisation of aircraft, and latterly the introduction of high strength materials, have focused attention on damage tolerant design in which allowance must be made for possible cracking and its certain detection before catastrophic failure. Especially for high strength materials is this change in philosophy necessary, because the improved static strengths (and hence potentially increased structural efficiency) rarely result in comparable improvements in fatigue properties, and are usually accompanied by a decline in fracture toughness and in greater susceptibility to environment-induced cracking.

This Second European Pioneers Day Lecture has two main themes: to pay tribute to the memory of Professor Dietrich Küchemann and second, to comment on how computers and wind tunnels should be used to assist aircraft design. These are not separate themes; as I will show, they are closely interrelated. You may be surprised that I feel that a lecture on the second theme is needed. However, in the past ten years, there has been a dramatic advance in theoretical methods on aerodynamics and in particular, for transonic flow calculations. This has created new opportunities but if we are not alert, there are also dangers in the new situation. My aim in this lecture is to draw attention to the opportunities and the dangers. I want to express my belief that computers will never completely replace the wind tunnel; we must learn to use them in partnership; only in this way can we hope to compensate for the limitations of any theory or the deficiencies of any experiment and finally, we must never forget that both are only tools; they are not a substitute for the human brain. Ideas, concepts, inventive genius, intuition, experience, the ability to interpret and draw logical conclusions will always be needed: in short, without scientists such as Professor Küchemann, the computers and the wind tunnels will be of little value.

Most civil and military aircraft developed over the past 10 to 15 years have relied upon increasingly complex avionic systems. Some units in this category have been developed to improve the presentation of information to the crew or to decrease their workloads; others have come to play a vital role in automatic flight control (such as fly-by-wire), so that it may not be possible to fly the aircraft without them (and indeed, in the case of ccv the aircraft may even be unstable without them); others again have been developed to give the crew better communication with each other and the outside world, and more detailed information from the radar system and its display. Figure 1 lists a breakdown of systems in a typical modern military aircraft in each of these categories: information and display, control, communications and radar.

Section 8(2)(h) of the Civil Aviation Act 1949 gives power to make provision in the Air Navigation Order ‘generally for securing the safety, efficiency and regularity of air navigation and the safety of aircraft and of persons or property carried therein’. When it was decided to institute a Mandatory Occurrence Reporting system, there was therefore no problem about including a requirement for reporting in the Air Navigation Order, since the whole purpose of the system is to secure the safety of air navigation.

Provision for Mandatory Occurrence Reporting was first made in the summer of 1974 by the Air Navigation (Amendment) Order 1974 which added to the Order a new article, Article 80(A), which specified classes of persons required to report to the Civil Aviation Authority ‘any reportable occurrence … which is of such a description as may be prescribed’. ‘Prescribed’ in the Air Navigation Order means prescribed in regulations (in this context the Air Navigation (General) Regulations) and Article 80(A) did not in fact bite until regulations had been made.

Many factors influence the choice of the electrical power generation system and the design of the associated busbar distribution network in an aircraft. Beyond the usual factors of safety, initial cost, weight, maintenance cost and the actual rating, the characteristics of the electrical power demanded by the utilisation system, and in particular the avionics equipment, are becoming a factor of increasing importance. The influence of such systems will, of course, vary with the aircraft size, its role, and its overall complexity. Perhaps it is as well also, to point out that the purpose of any system is to enable the aircraft to fulfil its role in the most cost effective manner. This may be a novel approach to the systems engineer whose enthusiasm leads him to believe that the aircraft's sole purpose is to carry around his pet system.

Ever since I first began to study Aeronautics I have been annoyed by the vast gap which has existed between the power actually expended on mechanical flight and the power ultimately necessary for flight in a correctly shaped aeroplane. Every year, during my summer holiday, this annoyance is aggravated by contemplating the effortless flight of the sea birds and the correlated phenomenon of the beauty and grace of their forms.

During the incredibly brief period of the last 20 years, a revolution has taken place in air transportation. The magnitude and rapidity of change, and its worldwide impact, are probably unprecedented in history. The earth has shrunk so that no two points are much more than a day apart. World travel has become commonplace, bringing with it sociological changes of immense potential magnitude.

Today we are standing on the threshold of an era of even greater growth in our industry and its contribution to the world.

It is the purpose of this discussion to review progress and promise in the total air transportation system from the standpoint of passengers and freight, geography, technology, economics, regulation, airlines, and manufacturers. I would like to do this in three parts: (i) progress, (ii) uncertainties, and (iii) promise.

As the eighth decade of heavier-than-air flight comes to a close, it has become increasingly evident that the nature of progress in civil aviation is undergoing a significant change. The transition from an explosive growth to what has been referred to as maturity has been both swift and unexpected, and coincidentally enhanced by factors external to aeronautics. While the anticipation of timing of such a change usually calls for a predictive ability which borders on clairvoyance, the inevitabilty of occurrence of transition in the development of any technology should be clearly recognised. It should be thus neither surprising that the forecasts of the 1960s have badly missed the mark, nor that the period of transition has set in.

As civil aviation moves into a new phase of development, it is of interest to evaluate the status it has attained globally as a mature industry and service, and to consider the factors which could significantly influence its future. We shall preface the global assessment with a brief review of the major causes of spectacular growth of aviation since 1945—an exercise necessary to appreciate the basis of maturity and the constraints now evident.

The present energy situation has caused engineers to look more closely at methods of energy recovery which have previously received only limited attention due to the availability of cheap and plentiful fossil fuels. One of these methods is the use of an airscrew, or windmill, to convert wind energy into mechanical energy. There are a number of disadvantages in the utilisation of wind energy: the power available is relatively low for the size of plant involved and the supply is intermittent, but on the other hand the energy is free and available in most areas.

The economic feasibility of using windmills on a scale large enough to supply the national grid system is debatable, but there is certainly a demand for small units suitable for the individual domestic consumer.

When we talk of a flight simulator, we naturally contemplate something which is artificial, something which is inferior to the real thing—a substitute for the real aeroplane. There is a danger, therefore, that we might also think of the flight simulator instructor in the same terms —that he is someone who is inferior to the real thing, the flight instructor. Nothing could be farther from the truth.

The flight simulator instructor needs to be a flight instructor who is additionally qualified to instruct on the simulator. He is therefore someone who is superior to just a flight instructor.

Over the 40-year evolution of the helicopter, man's understanding of vibration control techniques has greatly increased. However, with the performance of helicopters also increasing, the extent of their vibration problems has not diminished. Crew vibration therefore remains a significant factor in the design of all current helicopters. With more complex and critical demands being placed on aircrews it becomes more important that vibration should not impair their performance. Thus, as man's greater understanding of vibration control techniques provides the ability to constrain the vibration the definition of appropriate vibration limits becomes both more necessary and more useful.