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.

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 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.

Responsibility for the overall inadequacy of this history rests with the compiler, and it is a statement of fact, not an excuse for a mediocre document, to say that the disappointingly numerous gaps in it are at least partly attributable to the surpassing reticence and modesty of the men who were Martinsyde: Helmuth Paul Martin and George Harris Handasyde. They sought no publicity and did not even advertise their products in the early years of their partnership. Indeed, one of several mysteries about the firm is what it subsisted on in the pre-1914 period, for its products did not seem to sell in significant numbers.

I am most conscious of the honour of being invited to give the Sixth Handley Page Memorial Lecture, particularly in view of the renown of the previous speakers. Since these lectures are jointly sponsored by the Royal Aeronautical Society and the Cranfield Society, I am especially delighted at being the first ex-student of Cranfield who has been invited to present this paper.

In past years, flying a basic X-15 from launch through a dead stick landing on a precise speed and altitude profile was considered a demanding piloting task. The success of each mission was determined by the pilot's ability to perform under the physiological and psychological stresses of flight into a hostile flight environment of high Mach numbers, high accelerations, high altitude, and limiting temperatures. Today the aircraft has been extensively modified to qualify the X-15 as a test bed vehicle for a ramjet engine, which will be carried in place of the movable ventral, providing real time flight environment for testing and developing an operational prototype ramjet for use on future hypersonic cruise vehicles. The additional systems pictured in Fig. 1 (external tanks, ramjet, external window, and ablative coating), their associated emergency procedures and the degraded flying characteristics of the X-15A-2 have increased the pilot's workload significantly over the standard X-15 mission.

The slender-body theory of Ward is applied to a configuration consisting of a slender, pointed wing, carrying directly beneath it a pointed half-body of revolution divided along a meridian plane.

Expressions for lift and drag due to incidence are found which are valid in both subsonic and supersonic flow if the flow is attached. The lift result can be used to find pitching moment. For the supersonic case the drag at zero incidence is also found and the expressions for a conical configuration are developed so that a limiting form of these can be compared with the results of ref. 3.

The attitude dynamics of a spinning axi-symmetric satellite, free to librate in roll, is studied using the WKBJ method. Applicability of the method to the linearised equation of motion is first verified. To facilitate the evaluation of the WKBJ solution and to make it more amenable to the phase space analysis, second order terms in eccentricity are neglected. The form of the solution suggests the presence of phase and amplitude modulation effects for non-circular orbits. The comparison between the WKBJ analysis and ‘exact’ numerical solutions showed that the approximate analysis predicts the period and amplitude of motion with an accuracy adequate for the preliminary design purposes.

Tests of the first experimental VTOL aircraft using tiltable wings and propellers indicated that practical operational aircraft are possible and can operate with a high degree of effectiveness.

The flight tests accomplished up to the present time with the second generation tilt-propeller and tilt-rotor aircraft are discussed and analysed. The XC-142 and the CL-84 tilt-wing aircraft have been performing well throughout their projected flight envelope and good pilot ratings have been obtained with each in hover, transition, and the normal cruise mode. The X-19 tandem wing tilt propeller was flown only up to 100 knots and was lost due to a structural failure in one nacelle. Although the operation of the aircraft had been satisfactory up to this point, this programme was terminated due to shortage of funds.

A study of the various VTOL aircraft configurations operating at low radius of action indicates that the tilt wing/ tilt propeller type are the most cost-effective as long as speed is an important parameter in the operating mission. There are missions where speed is of secondary importance, and therefore, the helicopter will continue to be one of the most effective VTOL for these missions.

Since the tilt-wing /tilt-rotor aircraft tend to be only slightly higher in cost than the helicopter and with development the complexity and maintainability will be reduced to acceptable levels, it is anticipated that further work will be done in the development of these vehicles, and successful and useful machines will be built in the future.