The purpose of this paper is to attempt to examine the relations between airworthiness and safety.

It seems to me that the problem of safety in aviation is fundamentally a problem of human behaviour. The human controlled aeroplane is mechanically extended man. To quote Sherrington

If we exclude the effect of the counter strategies of competition an accident is a measure of the incompleteness of this dominance.

When in 1937, I last had the privilege of lecturing to the Royal Aeronautical Society on the subject, the automatic pilot was still in its infancy. The automatic pilot then described was known as the Mark IA. It may now be revealed that it had developed out of researches at the Royal Aircraft Establishment in the field that came to be known during the Second World War as Special Weapons. The Royal Navy had been backing the work, primarily with the object of developing a pilotless target aeroplane.

Under the guidance of R. McKinnon Wood, at that time in charge of the Aerodynamics Department of the R.A.E., the World's first successful pilotless aeroplane was developed as an anti-aircraft target in 1925, after a series of abortive attempts in which failure was due primarily to instability arising from the unsuspected coupling between the yawing and rolling motions caused by downward tilt, in relation to the flight path, of the rotor axis of the azimuth gyroscope used to control the rudder.

When, in the course of his visit to Paris in May 1948, Dr. Roxbee Cox invited me to lecture to the Royal Aeronautical Society on our work in the field of turbopropeller and turbo-reaction engines, I was torn between two sentiments; the great honour which was done to me, and the seeming temerity for a French engineer to discourse on aircraft turbines before some of the people who had been responsible for the W2 700, the Nene, Ghost, F2, Theseus, Mamba, and other engines. The first of these sentiments however carried the day, as it could hardly fail to do in view of Dr. Roxbee Cox's extreme kindness.

Therefore I ask for the indulgence of my audience in listening to this, the first account to be given of the modest work done since 1941 by a team of French technicians, who were specialists in steam and industrial gas turbines, who had foreseen the possible development of the latter for aircraft, and who, completely cut off from the engineering world during the Occupation, at first worked literally in complete isolation, unaware even of the existence of the British and German achievements.

The Fifth British Commonwealth and Empire Lecture was given before the Royal Aeronautical Society by Mr. E. H. Atkin, B.Sc, F.R.Ae.S., on the 15th September 1949 in the Lecture Hall of the Institution of Civil Engineers, Great George Street, S.W.I. Sir John Buchanan, C.B.E., F.R.Ae.S., President of the Society, presided.

The 777th Lecture was read before the Royal Aeronautical Society on 7th April 1949 at the Institution of Civil Engineers, Great George Street, London, S.W.1. Dr. H. Roxbee Cox, D.I.C., F.R.Ae.S., F.I.Ae.S., President of the Society, introduced the Lecturer, Air Commodore Vernon Brown, C.B., O.B.E., M.A., F.R.Ae.S., Chief Inspector of Accidents, Ministry of Civil Aviation.

The title of this paper clearly has a wide scope. None will dispute the presence of many problems in aircraft development. It was suggested in the first place that this paper might take the form of a description of the workings of a chief designer's mind when a new aeroplane is conceived. Such a paper would deal largely with technical considerations, such as choice of engines, wing loading, plan form and so on.

The diversity of uses to which the modern aeroplane is put gives rise to great differences between types. A jet fighter, for example, will be influenced by considerations far removed from those controlling the design of a long—range civil transport. To attempt to cover in detail such a wide field would result in an encyclopaedia rather than a paper; to tackle it in general terms would beget a vagueness lamentably devoid of interest.

Therefore, it has been thought wiser to attempt an assessment of some of the more fundamental problems confronting aviation.

France, paralysed during many years of a cruel occupation, has been unable to maintain a sustained technical effort, comparable with that of England.

Nevertheless, the work of French engineers was never discontinued. In difficult and sometimes dramatic circumstances, more often than not with only restricted facilities, their work of research continued, stubbornly and in silence.

The 773rd Lecture was read before the Society on the 17th March 1949 at the Institution of Civil engineers, Great George Street, S.W.I. Dr. H. Roxbee Cox, B.Sc., D.I.C., F.R.Ae.S., F.I.Ae.S., President of the Society, introduced the lecturers, Mr. G. C. I. Gardiner, A.F.R.Ae.S., Chief Engineer and Mr. J. Mullin, B.Sc., A.F.R.Ae.S., Chief Aerodynamicist of de Havilland Propellers Ltd.

Despite the high standard of workmanship employed in its fabrication, a propeller, like any other manufactured article, invariably differs from the ideal product in some respect which may, or may not, be of functional significance according to the nature of the disparity. The component blades of a propeller are no exception to this rule and it is the author's object to examine the consequences of dimensional deviations of the actual blades from those of an assumed standard and to describe apparatus devised to minimise or eliminate the most undesirable of them, namely, the tendency to induce vibration in the aircraft. From the earliest day, aircraft vibration has been attributed to the engine propeller combination and has come to be regarded as an inevitable characteristic. It can be demonstrated, however, that where aerodynamically balanced blades are employed, vibration difficulties are not an inherent property of the propeller. This is a matter of considerable importance to the turbo-propeller in which the prime mover is virtually vibrationless and consequently any unbalance of the propeller would be thrown into prominence.

It is many years since aircraft were first A operated under extreme low temperature conditions, mainly by bush pilots pioneering the northern latitudes of Canada.The aircraft used were of the light and semi—medium type fitted with simple, low—powered engines. Consequently, crude methods could be adopted to keep them operating.

With the advent of high—powered boosted—engined aircraft, with their complexity and numerous complicated installations, together with other associated equipments, the difficulties became manifold and the earlier methods used were either impracticable or inadequate.

For this reason, some intensive testing and research has been done on the latest type of aircraft, engines and equipment, in an endeavour to solve the problems and, if not entirely successful, find what medium of success can be achieved with the least amount of subsidiary aid.

Prizes were presented and The Thirty-seventh Wilbur Wright Lecture was delivered before The Royal Aeronautical Society at the Royal Institution, 21 Albemarle Street, London, W.l, on Thursday 28th April 1949. Dr. H. Roxbee Cox, B.Sc., D.I.C., F.I.Ae.S., F.R.Ae.S., President, presided at the meeting.

The 778th Lecture to be read before the Royal Aeronautical Society (the second main Society Lecture to be given at a Branch centre) was read under the auspices of the Portsmouth Branch, at the Portsmouth Municipal College, on 21st April 1949, by R. R. Duddy, B.Sc., A.F.R.Ae.S., on “ High Lift Devices and their Uses.” Sir John Buchanan, President-Elect of the Society, presided over the meeting with Mr. E. C. Green, Chairman of the Portsmouth Branch.

The Mamba engine has now been in existence some two–and–a–half years and in that comparatively short period of time it has been developed to the stage of being a type tested engine with over 5,000 hours test bed running and 100 hours flying as a background. The purpose of this paper is to give a brief account of the progress of the development and of the many problems which have been met and overcome during the period. Because of the many aspects of the development work it is not possible to deal in great detail with any particular item but rather to present the over–all picture, from the original design conception to the complete power plant of to–day.

The theme of flutter has not often been the subject of lectures before this Society, but the earliest of these was given as long ago as 1929 by my friend and former colleague Dr. R. A. Frazer. At that time a secure foundation for flutter theory had been laid and the principal methods for flutter prevention were already known. However, both theory and practice have developed much since 1929 and flutter has become of greater relative importance.

The 776th Lecture was read before the Society on the 31st March 1949 at the Institution of Civil Engineers, Great George Street, London, S.W.I. Dr. H. Roxbee Cox, B.Sc, D.I.C., F.R.Ae.S., F.I.Ae.S., President of the Society, introduced the lecturer, Dr. P. B. Walker, M.A., F.R.Ae.S., Head of the Structures Department at the Royal Aircraft Establishment.

Apart from its normal functions in aviation the applications of radar have been few. In the post-war period T.R.E., in conjunction with the Meteorological Office, have been making a study of possible uses of radar to the science of meteorology and the results of these investigations are described in this paper.

1. In the experimental work radar has been used to: —

2. (a) investigate precipitation,

3. (b) detect clouds dangerous to flying,

4. (c) measure cloud height, and

5. (d) measure wind speed and direction.

An account is given of how radar may be used to measure the density of the atmosphere at altitudes up to many tens of miles and of some problems still to be solved in the design of a radar sonde system for measuring pressure, temperature and humidity profiles.

It is concluded that radar will become an established meteorological tool and some possible profitable future lines of research are indicated.

It has long been the practice in engineering to use direct manual operation of the controlling parts of a machine, so long as it was within the strength of the operator, and so long as design of the operating gear was relatively simple. In innumerable applications, however, the increased demands for power by the controls, and the need for greater accuracy, have necessitated the development of servo mechanisms to drive them; that is, we have to sever, partially or completely, the direct mechanical link from operator to control, and use the inserted backlash, elasticity, and so forth, to meter power from an external power source.

In the flying control field we have come at this time to the transition stage, in that we have realised that, for a large number of applications, direct manual operation is impractical, and we are feeling our way towards suitable forms of servo controls for our various needs.

Safety in the air in simple terms means a reduction in the number of accidents. There are many factors which influence air safety, some of which are being dealt with by other lecturers; for my part I propose to consider a vital one, namely, the human link in the mechanism of control of heavier-than-aircraft which, for all practical purposes, is the pilot. However much importance is placed, and rightly, on such factors as aircraft structure and performance, meteorological aids, ground traffic control, and the many other details which are concerned with an aircraft's safety, the ultimate factor in this, as in practically every form of transport, is almost always the human one.

Although there may be, and usually are, contributory causes leading up to an accident, subsequent enquiries frequently record an error of judgment on the part of the pilot as being the final precipitating factor.