Flight that is unconventional now may not be unconventional in the future. In 1903 all flight by man was unconventional. Although the 1903 limitations in knowledge and convention have dropped away, certain kinds of flight remain unconventional for practical, if not good, reasons. Unconventional flight is flight outside the mainstreams of research and development. This implies that it includes flight modes for which little or no money is available and which, therefore, can attract only few knowledgeable and dedicated enthusiasts. Hence these modes lag behind the contemporarily directly useful aspects of flight.

A survey is made of the effects on aircraft of the main atmospheric factors and of the way they are dealt with, in design and operation, at the present time. Possible developments in the pattern of the relationships of aircraft to the atmospheric environment are discussed, in the light of expected advances like operational VTOL, and orbital-type flight, reliable weather forecasting, and effective turbulence avoidance and gust alleviation systems. These developments should all be conducive to safer and more comfortable flight. Marked further benefits would accrue from weather control in the vicinity of airfields, of which there are some prospects, improvement in en-route operation through weather control appears less probable, and the prospects of smoothing turbulence ahead of the aircraft are speculated on.

Power generation for civilian aircraft can only be considered in terms of what kind of flying people will want to do in the 2nd century because the weight and cost of the fuel which will be best are dependent on how much people can afford to pay, how large and how fast they want the planes to be and what the world's total aircraft fuel consumption will be in relation to the world's total supplies of various fuels.

The predictable primary power sources of the second century are the fossil chemical fuels, oil and natural gas, the nuclear fuels (fission and fusion) and solar energy.

Having been delivered about 3 years ago of a paper for the Society's Centenary Journal on the subject of rotorcraft in retrospect—without, apparently, undue birth pains—I was led to think some months ago, when I was asked to write a similar paper—this time on the prospect for rotorcraft in the next 100 years—that the process would perhaps be equally painless. However, unwittingly, I had made one grave logical mistake: I did not realise that this time I was involved with an altogether different bairnie!

In looking backwards one is concerned with collecting and collating factual matter from various sources, comparing present views with the views held at the time, and with such hindsight arriving at fairly positive conclusions, a more or less routine logical process, the quality of which is mainly measured by the care taken in considering all important factors in sufficient detail to ensure valid conclusions.

Developments in computer technology will result in a capacity for structural analysis and definition of structural geometry in intimate detail, and this capacity will be used to the full for design and fabrication in the relatively brittle materials of high specific strength and stiffness that will become commonplace. However, only evolutionary developments in basic structural form are anticipated for the future, with stressed-skin structure remaining dominant. The structure will be windowless.

Mass-produced personal aircraft will be required for leisure purposes, and glass is likely to be a favoured structural material for these.

The computer is seen as the greatest invention in history, in that it has a universality which transcends all other known inventions. It will ultimately be capable ot any process describable in terms ot an open or closed logical structure.

In a deterministic science such as aeronautics, it has clear capabilities in the solution of the equations governing fluid flow, structures, propulsion, navigation and so on. The speed and size of future computers, together with all sorts of new software techniques, will facilitate almost instantaneous solutions of any problems, within the next century.

There will be two major constraints on these developments which we can predict with confidence. The first is financial. The second is more subtle: there may develop sociological resistance to technological advances, especially to those wielding the power implicit in future generations of computers, and this carries important implications for scientists.

This is a personal attempt to take a long view into the Second Century and to describe prospects for further possible developments in aviation, with particular emphasis on the part played by aerodynamics in the evolution of aircraft. The overall view is necessarily broad and wide, and the material is taken from the results of earlier papers(1-2). An attempt is made to put the future prospects into the perspective of past developments, and it is concluded that aviation can look forward not only to a vast expansion on the technical side into most promising and as yet unexplored fields, but that it may also be built into a more rational social system with the aim of serving mankind as a whole.

The introduction to a book called “An Anthology of Partly Baked Ideas” states that it was compiled to provide an opportunity for the publication of ideas either half or partly baked, which might not otherwise be suitable for publication in established learned journals.

However, the Royal Aeronautical Society's decision to solicit articles on aeronautical achievement in the latter half of the twenty-first century is a direct invitation from a learned society to expound on, what at best, can only be some very partly baked ideas.

The author of this admirable anthology, I. J. Good, has defined partly baked ideas (PBIs) in some detail in the opening chapters where he gives a clear indication that reputable scientists and engineers should at very least endeavour to incubate their proposals to the point where the degree of “bakedness” should be greater than 0·5, i.e. better than half-baked.

In the first contribution to “Looking Ahead in Aeronautics” Dr. Küchemann writes “The task of viewing the prospects over a whole century may be regarded as being at once impossible, presumptuous and not without a touch of the absurd”, which lies close to the first response of the present author. But on reflection, the very impossibility of reliable prediction a century ahead surely stands to change the tune somewhat. Over this large time-scale, bold flights of fancy into the unknown must take equal place with cautious realism and an author may presume to feel released from some at least of his usual conditioned restraints. In turn, yielding of constraint strengthens the writer's arm, until, not without a certain sense of trepidation, one is at length tempted to plunge into the guessing pool along with a goodly company of fellow men.

Predicting the future for Agricultural Aviation is rendered even more uncertain than predictions for most forms of aviation because in this case the future depends on two entirely separate sets of unknowns. These are the normal unknowns affecting aeronautical development but, more important, there are the unknowns affecting the development of agricultural chemicals. Also, in predicting the future evolution of any activity one must normally look back over the rate and the trend of developments in the activity, so far as they are relevant, from the past and then project this rate and trend into the future, bending and extending the line of projection in accordance with known or foreseeable influences. Here again we get a third set of unknowns related to future farming techniques, although these unknowns are perhaps less significant because the main expansion in agricultural aviation will probably lie in the vast undeveloped regions of the world where the farming techniques will merely be brought up to present standards, or just introduced where there was literally no agriculture before.

This paper introduces the series of Second Century papers which will appear in the Journal during 1968. The reasons which led the Publications Committee to arrange this series is explained and the authors and the titles of their papers are listed. The papers consider possible changes in aeronautical science, engineering and operations from now until a century ahead on many topics including Propulsion, Aerodynamics, Computing, Navigation, Control, Space Flight, Hovercraft, Aeronautical Education and Law for Aerospace.

This paper sets the scene for the others by reviewing how the aeronautical future looked to Cayley in the early nineteenth century, to those attending the 1893 International Conference, to Lanchester, Thurston and Roxbee Cox. The changing nature of forecasting is illustrated by the Lockheed SST market study of 1965 which is given as an example of present-day predictive techniques using computers.

On 31st December 1966, General McKee of the Federal Aviation Administration announced that The Boeing Company and the General Electric Company had been selected to develop the prototype airframe and engines for the United States supersonic transport. The announcement ended a long, intense competition and was the culmination of the nine years of effort on the part of Boeing, where since January 1958 there has been an identified, separate project devoted to the SST.

The NASA Langley Research Center has conducted an intensive and broad research programme on supersonic cruising aircraft for some 10 to 12 years. During the course of this effort to advance the state of technology of supersonic flight, a number of interesting research or design techniques and approaches have evolved. Several of these which have application to present and future aircraft design are discussed. The use of highspeed computing equipment in the application of linear theory to the problems of optimising supersonic cruising efficiency is treated. Experimental techniques employed in the study of drag at transonic speeds in wind tunnels are described. In the area of aircraft operations, attention is directed toward unique simulation methods employed in studying the relationship between air traffic control systems and supersonic aircraft.

Almost exactly ten years ago the National Research Development Corporation (NRDC) decided to support Christopher Cockerell's ideas for what soon became known as hovercraft. Since then there have been remarkably rapid developments in marine hovercraft and in other applications of the air cushion principle, and there is little need to remind this audience of what has been achieved during that time. Indeed, the large cross-Channel SRN4, and the smaller new Hovermarine sidewall craft, as well as the recently announced design by Vosper-Thornycroft, all speak for themselves and demonstrate vividly the major strides that have been made within a single decade.

During this period there has naturally been a strong emphasis on development work closely related to specific engineering and design projects, but experimental and theoretical investigations of a more general and basic nature have also been encouraged in this country. It is always difficult to separate clearly research from development and this is particularly so in the first decade of hovercraft.

Since this is a Tizard Memorial Lecture, I think it is appropriate that I should tell you something about Operational Research in the Royal Air Force as it is carried on today. The RAF has a great tradition of actively using operational research to promote the efficiency of the Service and it was Sir Henry Tizard who initiated this tradition and sustained it until it was well established. Indeed, he was responsible for the much wider application of science to air warfare, but I am not attempting to cover the wider field in this lecture.