The rate of progress in most technical fields, and propulsion is no exception, has increased so rapidly during the past 50 years that it is becoming difficult to predict the trend of development for more than a few years ahead. On the other hand, there are fundamental limits to progress in certain directions and it is within these limits that this paper is written. One must, of course, devote some thought to the validity of the limit. Not so long ago it was thought that the speed of sound would be a limiting speed for aircraft, for instance. One cannot go far wrong with the basic laws of physics and the intention, at least, of this paper is not to transgress such laws.

The safety target for the Supersonic Transport has been set by the governments sponsoring the project. This is to achieve a safety level at least as good as that of subsonic aircraft at the same time. An analysis of present accident trends is used to give more precision to this statement. If the present rate of improvement in safety continues, the accident rate in the early 1970's can be expected to be some 20% to 25% below today's figures and the target for the SST must be for an improvement of at least 30%. To achieve improvements of this order in a safety record which is already good requires considerable effort by all concerned and necessitates a more scientific approach to safety requirements, especially airworthiness requirements. Some examples of the way this is being done in the United Kingdom and f ranee are given.

In considering the spectrum of possibilities which advances in electronics offers during the next fifty years it is worth a short backward glance over an equal time span.

In 1918 the use of electronics was almost entirely devoted to developments in the radio frequency field, principally those of communication and sound amplification. Wireless telegraphy under pressure from naval and merchant marine requirements had reached the stage where it formed a dependable means of communication, albeit with the need for specialised human skills, for the world's modern shipping.

There had been a limited amount of aeronautical radio development during the war, to reduce the size and weight of wireless telegraphy and the later radio telephony transmitters; much of the later stages of this work was carried out at Biggin Hill. However, these developments had scarcely any influence upon either the design and construction of aircraft or perhaps more important only a small influence on their operation. It was to be sometime before the exploitation of the radio frequency spectrum on the ground and in the air contributed to increase greatly the operational capability of the aeroplane during the 1930's.

It is a great privilege for me to give the Eighth Cierva Memorial Lecture and to pay tribute and honour to Juan de la Cierva who, more than any other inventor, was responsible for bringing into reality the principle of rotating wing flight. Cierva was an inventor of indefatigable industry, patience and genius. His faith in the Autogiro and the future of the rotating wing aircraft will be remembered for ever.

The invention by Cierva of the articulated rotor with flapping and drag hinges to relieve bending stresses at the blade root, and in the chord-wise plane, provided the solution to true helicopter flight which become a reality in 1936.

Aviation has become a great international utility, and as the scale of investment has grown innovation is increasingly dominated by economic considerations. The time needed to bring research, development and design to fruition is lengthening and economic and technical trends must be appraised tor many years ahead. Of the various parameters defining aircraft design and performance, speed is the most fundamental. The speeds of both military and civil aircraft have been doubling every decade for over 50 years; but the factors which contributed to this exponential growth have changed and a new basis for prediction must be established.

Above high subsonic speed transport efficiency remains sensibly constant although with pronounced optima around Mach 0.8 and Mach 3. In future, aircraft will tend to fall into distinguishable speed regimes; but application will be determined by their economic productivity rather than by small differences in transport efficiency. Subsonic aircraft will remain the mainstay of civil and military aviation for many years, with supersonic aircraft meeting a growing civil demand on the longer international routes and military requirements tor fighters, bombers and reconnaissance aircraft. In neither field is there any imminent demand for hypersonic aircraft.

But if the quest for higher speed is no longer the dominant incentive in aeronautics, there are new in:tiatives at the low speed end of the flight envelope, and continued improvements are foreseeable in the efficiency of propulsion, structure, and avionics. If these opportunities are seized there is a challenging and rewarding future for European aviation.

From April to September of this year there will be numerous celebrations in honour of the Royal Air Force's 50th Anniversary, and it is highly appropriate that during this period the full plans for the Royal Air Force Museum are to be made public. The Museum is to be a new national institution maintained by the Treasury but built out of the sum obtained from a public appeal which is now in full operation.

A question constantly asked of all connected with this project is “who first thought of the idea?” The present writer has been told by at least a dozen men, all of them honest of eye and sincere of voice, that they and they alone were the only true begetter of the scheme, and it is a fact that every Station Commander who caused one or two aircraft to be preserved past the day of their official demise can feel that he and his men played some part in the slow development that has culminated in the present large-scale project.

The paper considers the possibilities of a single type of VTOL vehicle—the compound rotorcraft—in the context of 1968 technology. Past and current compound programmes are reviewed in establishing technical status and include the XV-1, Fairey Rotodyne, Kamov KA-22, US Army Aviation Material Laboratories experimental compounds and the AH-56A (AAFSS).

Qualitative characteristics of compound rotorcraft such as airframe vibration, gust response, landing and take-off characteristics, and safety are discussed and compared with both fixed- and pure rotary-wing aircraft.

Characteristics such as cruise speed, vehicle lift/drag ratio, empty weight fraction, and maintenance are examined quantitatively for a 30-passenger compound rotorcraft, and appropriate limitations of these characteristics are discussed. Sensitivity of direct operating costs to changes in these characteristics is considered.

The compound method of VTOL flight appears to offer great promise in both military and commercial fields, particularly as it can be applied to the inter-urban mass transport problem and to Army logistics and ground attack functions.

The interest in Canada in the design and manufacture of utility aircraft with a short take-off and landing (STOL) performance may be traced back to the difficulties of surface transport in the early development of the country and the widespread use of bush aircraft.

The leading characteristics of the STOL aircraft are examined with particular reference to design features essential to a short take-off and landing. The choice of powerplants and lifting systems is discussed with emphasis on the requirements for powered lift in the larger sizes of aircraft. The augmentor-wing is described as an example of an integrated propulsion lifting system with promise of a high performance.

The phases of the take-off, transition, climb and landing manoeuvre are reviewed to illustrate the relative importance of various parameters in design and operation. The importance is stressed of good stability characteristics and effective controls for manoeuvring in a confined air space and a consistent landing performance.

The requirements of a para-military mobile force tor a rapid response, deployment overseas and transportation in an area are examined. Some estimates are given of the probability of finding suitable airstrips in a particular region and the cost of constructing new airfields in a dynamic situation. The operating environment in potentially troubled areas of the world is examined briefly to provide guidance in design. The costs of a military supply system are discussed using various modes of transport which include trucks, helicopters, STOL and conventional transport aircraft with results which suggest that the system employing STOL aircraft in the tactical theatre has advantages in cost and effectiveness.

Attention is drawn to the growing requirement for shorthaul, commuter and air taxi aircraft with STOL characteristics. Reference is made to the increases in air travel and the widespread use of large transport aircraft which have encouraged the movement of airports from urban centres at a time when city growth and congestion render surface transport increasingly difficult. The relative costs of commercial systems using the helicopter and STOL aircraft are examined. It is shown that the cost of STOL ports is not an excessive portion of total system costs when all factors are taken into account. Some forecasts are made as to future development trends in transport systems using STOL aircraft.

Before I begin to generalise about the RAF, let me make a generalisation about mankind and us islanders. All men are escapists by nature. What distinguishes islanders from all other men is that they are the progeny of active escapism. In the legends of antiquity these “Islands of the West” in which we live were the “Isles of the Blest”. Remote continentals longed to escape hither. That is something we tend to forget—not without reason nowadays!—although the process still goes on, in darker colours now. Aviation has become the most general and the most active form of escapism. It is essentially transcendental !

Propulsion systems selected for commercial transports must provide efficient and reliable performance over a broad range of conditions. These aeroplanes are used over both short and long route segments, on non-standard days, and at a range of altitudes to meet air-line schedule requirements.

This paper covers some of the design parameters that were considered in the integration of the induction system, secondary air system, jet nozzle and the basic turbojet gas generator for the SST. During recent years some of the most important gains in propulsion efficiency have resulted from the development of inlets, engines and exhaust nozzles which are matched over a broad range of operating conditions. An efficient propulsion system for a supersonic transport depends upon very close matching of these components. This, of course, requires a better understanding of the capabilities and limitations of each of these major components. For the supersonic transport, 50% or more of the gross weight will be comprised of propulsion system and fuel and less than 10% will be payload.

I think that by now ELDO is sufficiently well known that I can assume its purpose and aims need no long explanation. I would prefer to give first a summary of its present situation, its achievements and the experience which has been gained; and at the end I shall give an indication of ELDO studies aimed at future activities.

Orbital manoeuvres by means of impulsive thrusts, such as those available with chemical rockets, are well known, but a different treatment is needed for the small, continuous thrusts that are typical of electrical propulsion systems. It is shown that with the aid of these small forces it is possible to change independently all the orbital elements of a spacecraft, and thus to proceed slowly from a given orbit to any other. For each manoeuvre there exists an equivalent velocity which depends only on the initial and final orbital states, and which can be related directly to the spacecraft propulsion parameters.

For any form of propulsion where the propellent acquires some or all of its energy from a separate energy source, as in electrical propulsion, it is found that optimum time-varying relations exist between the flow of mass and of energy, which may also be expressed in terms of the exhaust velocity and the thrust. In particular, the optimum exhaust velocity is shown to be an increasing function of time, related to the way in which the energy is released.

The practical realisation of electrical propulsion depends on the development of efficient propulsion units and of lightweight power supplies; these and other spacecraft components are discussed, and a number of examples of orbital manoeuvres are given, including close-Earth, far-Earth and lunar orbits. The paper concludes with a discussion of these orbital transfers in relation to their possible uses, including communication satellites and a test of relativity theory

The thunderstorm was a hazard which had still not been investigated at the end of the war, a hazard that had caused many serious aircraft accidents. No longer could the old admonition to stay out of thunderstorms be strictly followed by commercial or military pilots, whose flights could not be restricted to fair weather so as to avoid the severe turbulence occurring inside most thunderstorms.

This led to the ‘Thunderstorm Project’ in the USA in 1946-47 in Florida and Ohio'. Since the hazardous features of a thunderstorm are associated with individual cells, it is important for an understanding of the storm as it affects flight operations, to be aware of the nature of these features and their variation with stages of cell development.

Among the most interesting aircraft development programmes currently in progress is the Flight Test Programme of the F-111, an aeroplane that is being built for both the USAF (the F-111 A) and the US Navy (F-111B). Although the operational envelope of this aeroplane is only a modest step forward into new regions of flight, the dictates of its multi-mission role over the largest Mach-altitude envelope ever achieved by a tactical aeroplane is a significant advancement in the “state of the art”.

To accomplish these mission objectives, which include short take-off and landing distances, sustained supersonic operation at low altitudes, and a Mach 2.5 capability at high altitudes, the F-111 is configured and equipped with a number of unique design features and advanced systems. This discussion is intended to present a brief description of the more interesting features and a progress summary of the F-111 flight test programme.

In late September 1967, Her Majesty Queen Elizabeth II of Great Britain launched a new Cunard ocean liner in Scotland with the phrase, “Every great enterprise has an element of risk and uncertainty about it and I am sure no one can predict the future of our venture.” The launching of any new aircraft carries a similar connotation. For the jumbo jet as for the ocean liner, the risks should be recognised and, therefore, minimised because both the building of the ocean liner and the jumbo jet are extensions of a known art, not an introduction to unknown ventures such as may be true of the SST.

Size is relative. In its day, the DC-3 was called the “giant” air liner. If one compares the 21 passenger DC-3 with the 250 passenger DC-8, a twelve-fold increase, one can say that we are already in the jumbo jet age. The transition has been gradual through the Stratoliners, the DC-4, the DC-6, the Constellation, DC-7, Britannias, Vanguards, Caravels, Convairs, 707’s, and others. The results have been dramatic. (Fig. 1.)

The first part of this paper, published in the May JOURNAL, discussed in general terms certain topics relevant to business objectives and industry orientation and dealt in some detail with definition of company objectives and strategic plans. The successful completion of this first phase is dependent on close co-operation between Government and Industry for both civil and military projects.

This part of the paper deals with the procedures for implementing the strategic plan (management control) and the application and control at operational levels (operational control). The phase of implementation is one where considerable scope exists for ensuring future effectiveness through sound direction in that the plan becomes a firm commitment at this stage.

The paper concludes with a brief summary and a list of recommendations for future activities within the Management Studies Group of the Society aimed at definition of a basis for application of the disciplines described in the paper.

Structural testing has always been an art as well as a science but never more so than at present. Even though knowledge in relation to design and stressing has increased, testing is still a vital feature. This increase in knowledge has been accompanied by more complex problems particularly in relation to the need for environmental testing with the advent of supersonic and hypersonic aircraft, VTOL aircraft, rockets, guided missiles and space vehicles.