Although The Aeronautical Journal goes back a long way its main purpose is to look forward by publishing the latest research, design and development ideas for a knowledgeable and critical audience. Launched in January 1897, well before the Wright brothers’ record-making flight, the Journal has now reached Volume 107, number 1072. In this special issue to celebrate the 100th anniversary of the Wright brothers’ extraordinary achievement, it was decided to ask an international group of experts to look ahead to the next 100 years (or at least as far as they thought they could see). Hence in November 2001 the then RAeS President, Professor Ian Poll, wrote to a number of eminent people in the world of aerospace, inviting them to contribute. The response was enthusiastic and the fruits of their labours are on the following pages.

In the coming century, the impact of air travel on the environment will become an increasingly powerful influence on aircraft design. Unless the impact per passenger kilometre can be reduced substantially relative to today’s levels, environmental factors will increasingly limit the expansion of air travel and the social benefit that it brings. This essay considers the three main impacts, noise, air pollution around airports and influence on climate change. Of the three, impact on climate change is taken to have the greatest long-term importance and is discussed at the greatest length. It is argued that, of the three main contributors to climate change from aircraft – CO2 emissions, NOX emissions and the creation of persistent contrails – it is the last two which are the most promising targets. Ways of reducing the impacts of these two are discussed and it is noted that, in each case, the best environmental result is likely to entail some increase in CO2 emissions. It follows that regulatory or economic measures to reduce impact on climate should be framed so as to do just that. Measures framed purely in terms of CO2 emissions are likely to be counter-productive. Nevertheless, the design of aircraft to reduce fuel burn and hence CO2 emission remains a key long-term objective; the essay considers the potential offered by new technology and new design concepts in this arena.

The ongoing revolutions in information, biological, energetics and nano technologies are changing the nature and equipment of warfare. This is particularly true in military aeronautics. In the nearer term aircraft are becoming increasingly ‘uninhabited’ (UCAVs, UAVs etc.) enabled by the IT revolution, with multitudinous accompanying benefits in terms of affordability, survivability, redefinition of ‘risk’ and lethality. THE issue for such aircraft is enhanced persistence and increased range within the context of the overall system metrics. In the longer term the increasingly capable worldwide ‘sensor web’ will place at risk all air vehicles, in or out of theatre and whether or not they are ‘stealthy’. This, combined with advanced conventional weapons, high energy density material powered EMP (electro-magnetic-pulse) weapons and affordable swarms of ‘brilliant’ munitions will probably require yet another re-definition of military aeronautics, perhaps as survivable (hardened) hypersonic, global range, boost-glide devices.

One hundred and two years ago, after the Wright brothers had just attempted another unsuccessful flight, they predicted that it would be another 50 years before manned flight was achieved. Only two years later and 100 years ago this year, Orville Wright achieved the first powered flight at Kitty Hawk in North Carolina, illustrating just how difficult it is to predict the future and at the same time launching the pioneering age of aviation.

We discuss the status, trends and long-term ambitions of Computational Fluid Dynamics (CFD) when applied away from the design point or concept, and therefore in the historically weak areas of CFD. This includes both undesirable flight conditions, such as stall, and undesirable products of the flow, such as noise. All pose the great challenge of turbulence, and accuracy is as dependent on the ideas behind the turbulence treatment as it is on computing power. A measured shift from Reynolds-averaged representations to large-eddy simulations will take place. Empiricism, both turbulence and engineering related, will recede only step by step over many years. Yet, CFD will make full use of every increase in computer power of this century. Increasingly, CFD will compete with flight tests, not just with wind tunnels, and will be validated by flight tests. Integration with other disciplines will allow us to predict crucial phenomena such as flutter, sonic fatigue, and pilot-induced oscillations. A gap will remain at any time between the phenomena amenable to a ‘grand challenge’ calculation and those amenable to a fully CFD-based design process, because certification involves thousands of conditions. The highest demand currently is in community and cabin noise for which industrial-accuracy methods are non-existent. On the other hand, gratifying progress has occurred in the area of stall and spin.

The prediction of the future is always a relatively uncertain process. The only certain fact is that the prediction is unlikely to be wholly accurate. Even the prediction of trends following examination of past performance will be uncertain regarding the future rate of advance and may be entirely upset by new discoveries and their application. This is as true for examining the future of airframe materials as it is for prediction of economic growth, which itself significantly affects the development of materials technology in the aircraft industry. However, 100 years of powered manned flight does give a solid database from which to begin. In that period airframes have moved from wood, wire and canvas, through to riveted and stressed skin metal structures to adhesively bonded polymer composites. In each case the use of new materials is associated with a change in fabrication methods and it may be confidently anticipated that this will remain true in the future. This fact accounts for a justified conservatism in embracing new materials, not simply because of the need to develop experience and confidence in them, but also because of the costs associated with new constructional methods entailed in their application. It also, in part, accounts for the generally slower pace of application of new materials relative to what is initially predicted: the other powerful brake being the state of the economy and the market for new aircraft at any particular time. The early prediction of the demise of aluminium and its replacement by polymer composites made in the 1980s being a case in point, while the failure of alloys containing lithium to replace conventional aluminium alloys had more to do with cost and decreasing fuel prices than any alloy development problems. It can, however, be expected that, as in the twentieth century, military aircraft will exploit larger mass fractions of advanced materials and at earlier dates than civil transport aircraft, given their very different operational requirements and much shorter design lives. The likely advent of unmanned combat aircraft may well accentuate this difference.

The first centennial of man's first powered flight, which was performed by Wilbur (1867–1912) and Orville (1871–1948) Wright (Fig. 1) will be celebrated in 2003. These brothers' unique and trendsetting enterprise, their skills to develop, build and commercialise controllable and load-carrying flying machines, formed the first example of a private interdisciplinary aerospace development and design initiative. It was at the same time a rare example of entrepreneurial engineering. Their work involved wind-tunnel testing of lifting devices and full-scale tests of major structural components. Equally if not more importantly they developed an essential propulsion system consisting of a lightweight 36hp engine with four cylinders in line and a fuel injected carburettor. This engine propelled two pusher propellers through a drive system of chains. Moreover they developed the systems to control their flight. The twistable wing tips that control rolling and heading during the flight were the last remains of the former trend to mimic bird flight.

This paper looks to future developments and concepts in Systems and Avionics. One hundred years ago neither ‘avionics’ nor even ‘systems’ would have been recognised as having a place in aeronautics. The concept of aircraft systems developed, as the complexity of each element of the aircraft grew, requiring specialism in the design, operation and maintenance of those elements. Early examples would have been the propulsion and flying controls systems. By the 1930s passenger aircraft might have carried, in addition to the pilots, a navigator, flight engineer and radio operator, each responsible for his own collection of systems, with the aircraft itself probably having an embryonic electrical system.

Flight simulation has definitely kept pace with powered flight through the past century, and its future is seemingly unlimited. To understand where the future might lie, it is important to consider the current situation, in terms of training, engineering and entertainment industry (consumer) uses of simulation. As will be shown, simulation has become a critical tool for use in aircraft design and validation, as well as playing a key and well-known role in flight training. Of course, entertainment uses of simulation are becoming more common; ranging from PC-based games to rides at the mall. By reflecting on these uses of simulation and the drivers behind them, it is possible to project into the future; both near-term, and well into the next 100 years. The projections will hopefully lead to healthy discussion and further speculation in academic and industry forums – and ultimately to new and better ideas.

In writing this essay on rotorcraft I have chosen to confine my interests to the flying machines themselves, their development and the pressures that are shaping their future.