The rigid airship in its modern form is a German conception, but the nature of the strength calculations employed by the Germans has been a carefully guarded secret. When the U.S. Navy undertook the construction of rigid airships it was arranged to have one ship designed and built in the United States, the ZR. 1, and one ship designed and built in England, R.38 (ZR.2). Lacking practical information and experience, fundamental theory had to be resorted to in undertaking the design of ZR.i, and all available information had to be analysed,, compared and, so far as possible, tested. After the unfortunate loss of R.38 the calculations for ZR. 1 were reviewed and additional calculations and investigations undertaken.

The authors of this paper, under the direction of Rear-Admiral W. A. Moffett, Chief of the Bureau of Aeronautics, U.S. Navy Department, have been charged with the design of ZR.i and have had in the course of duty to make, or cause to be made, such studies and investigations as would assist in analysing and simplifying the problem as much as was possible in advance of full-scale experiments in flight.

I may as well confess at once to the fact that when I was asked to lecture some time ago the term “Airmanship at Sea” was selected as the title whilst my subject was still at the back of my mind. On settling down to my task, however, I found that the field was too wide for me to attempt to cover it conveniently in one paper. I propose, therefore, with your kind permission, to confine my remarks to that part of airmanship which concerns the handling and maintenance of seaplanes on the water, or as has been suggested to me the “harbour” side, rather than the “deep sea” side, which covers rising from the sea and landing, flying over the sea, and the many important air duties the pilot must be master of before proceeding on patrol, reconnaissance or a bombing expedition. I trust that I shall be forgiven if it is found necessary to deviate into side issues occasionally for the purposes of illustration and comprehensive understanding.

I must apologise for the many shortcomings of this paper and plead in excuse that it has been very hurriedly prepared. When I was asked at short notice to write a paper in place of Squadron-Leader Maycock’s, I somewhat rashly undertook to do so, but it has proved a formidable task in the very limited time available.

When asked to read a paper on the Thermodynamics of Aero Engines I felt very doubtful in the first place whether I ought to attempt such a subject at all, for, though I have posed often as a mechanic, I have not posed before as ascientist, at least not in public. In the second place I felt doubtful, if I attempted anything so rash, how to deal with the subject. Clearly I must adopt one or other of two lines, either play for safety and stick firmly to the fundamental thermo-dynamic laws which are unassailable but also inapplicable to practical working conditions, or take the plunge and endeavour to argue or at least to speculate as to how these fundamental laws must be qualified to meet actual working conditions. In adopting the latter course I realise that I must touch upon many highly controversial questions, and if in places I appear to lay down the law on what at best is little more than mere conjecture, I must ask you to forgive me and to realise from the start that the last thing I intend is to appear didactic.

When I was invited to deliver this lecture I proposed to deal with some aspects of Aeroplane Photographic Survey in which I have been especially interested, but in view of an event which happened on October 13, 1923, viz., the death of Major J. C. Griffiths in a flying accident at Coventry, I have felt that it is my duty to devote some part of this lecture to a consideration of the contributions made by my late friend to the advance of our knowledge of some of the fundamental features underlying the practice of aerial survey. For morethan three years, Griffiths, working under the direction of Prof. B. M. Jones, toiled at certain problems which were by no means easy to attack, which were absolutely of first-rate importance as a basis for certain types of survey work, and which when fully investigated provided results which had nothing spectacular about them, but which have laid a firm foundation for future work. Underconditions which were seldom easy and were frequently most discouraging, he worked unremittingly towards the solution of the problems which he was investigating, and has produced results which are of lasting worth.

In April, 1919, the lecturer had the honour to address the Society on the subject of Air Navigation, the Chairman being Air Commodore Brooke Popham, who had just been appointed as the first “ Director of Research ” at the Air Ministry. During the introductory remarks made by the Chairman at that lecture, an aircraft was described as being an “ encumbrance ” unless “ one could get it where it was wanted.” Now since it happens that one of the main purposes for which aircraft instruments exist is to enable such craft to be got “ where they are wanted,” the importance of our subject to-night will not be denied. Moreover, according to a recent most able paper in our Journal, Leonardo da Vinci himself stated his conviction that “ Instrumental or mechanical science is very noble, and useful beyond all others.“

Just a month or two more than twenty years ago, Orville Wright made the. first flight on a power-driven man-carrying aeroplane. This original Wright biplane was very far from being the first serious attempt to produce a man-carrying aeroplane, and it is not unfair to say that the machine itself was in its essential principles, and in respect to the skill and ingenuity displayed in its design and construction, no revolutionary advance upon certain previous machines which had been designed for the same end.

As a matter of fact, the machine, including engine, was designed and built in little more than a year, and regarded purely as an engineering structure it was considerably cruder than certain earlier aeroplanes which never succeeded in flying. The explanation of the Wrights’ success in this matter is, I think, to be found in the fact that they had learnt to fly before they attempted to build an aeroplane rather than in any remarkable qualities possessed by the aeroplane which they produced.

There are various considerations which govern the use of materials in engineering construction. The use of many of them is founded on precedent, and in the case of the older branches of engineering the original reason for their use is sometimes obscured.

From time to time as new classes of materials are developed they aregradually incorporated, often breaking their way with difficulty through the wall of prejudice with which engineering caution so often surrounds its designs.

For many years the claim has been put forward that the Royal Aeronautical Society is the oldest aeronautical body in the world through its unbroken existence since its inception on January 12th, 1866. This is a proud title—though not perhaps so proud as that of being the most active and up-to-date—which it has interested the writer to examine in the light of various documents bearing on the history of similar French societies which he possesses in his own collection of early aeronautical literature or has found in the admirably complete historical library at 7, Albemarle Street. In the hope that these researches may prove of interest to others, and of assistance to future historians, he has set down the results here in the form of notes on the various French societies, grouped under the four heads into which they seem to fall, the authorities for various statements made being inserted in brackets.

The growing importance of the study of Sound has been shown in many ways during the last few years and most particularly in its applications to military intelligence. Since the classical experiments of Tyndall in 1872 and following years, there is no very definite record of open–air experiments until L. V. King in 1919 performed some experiments for the Canadian Government on fog horns.

A new era of investigation has now been opened up by the realisation of the importance of observation by sound during the late war. The distant gun was located very effectively on most of the Army fronts, and towards the latter end of .the war the aeroplane, invisible at night, was being located by sound also.

The urgency of the problem to be solved resulted in the development of new and effective apparatus which is now available for peace applications as they arise. New microphones and new electrical accessories, particularly the new thermionic valve, have given acoustical research a new interest and have led to the hope of our being able to produce standards, thus bringing sound into line with the other branches of physics.

I am indebted to the Air Ministry for permission to use the material contained in the various official reports dealing with this subject, and I wish to say that the views expressed in this paper are my own personal views and do not in any way represent the official view of the Air Ministry, nor indicate the policy to be pursued.

I am also indebted to the makers of the aircraft for supplying information in such detail and for permission to make use of this information.

In the Aeronautical Journal of September, 1922, the writer published an article setting out a brief description of the work that is being undertaken by aircraft in Canada, and describing more fully the details of the problems that were peculiar to the country, more particularly the technical work in connection with winter flying, and, in order to avoid repetition as much as possible, it is necessary to refer occasionally to that previous paper.

Fuel consumption in flight is dependent on three main factors—the aerodynamic efficiency of the aeroplane, the thermal efficiency of the engine, and the efficiency of navigation, which entails a study of the most advantageous height, speed and direction of flight under any conditions of wind. Fuel consumption is therefore the ultimate measure of the overall efficiency of the complete aeroplane, the pilot, and the organisation ; its complete study would require far more time than can be given to it in a single lecture. I propose, therefore, to confine myself to fairly general considerations, with particular reference to the commercial aeroplane. There have been distinct advances in the direction of fuel economy in flight since the war period, but even now the weight of fuel carried in a commercial machine operating over the comparatively short London-Paris route of 230 miles and capable of a cruising speed of 100 miles per hour is approximately half the full paying load carried, so that a reduction of the fuel load by 40 per cent., which is by no means outside the range of possibilities, would increase the paying load by 20 per cent., other things being equal.

In surveying the mass of aerodynamic data presented to the designer of aeroplanes, one is struck by the fact that so much attention has been devoted to quantitative measurements upon bodies in a flow of air, so little to the equally important qualitative measurements. It is known that any body subjected to a flow of air is the means of creating eddies, yet relatively little attention has been given to the study of these eddies. Possibly the assumption has been that such eddies are of little importance since in the case of the aeroplane thev are left behind the body that is causing them and so cannot exert a secondary effect upon it. In fact, an aeroplane in flight is the means of creating a vast number of whirls and eddies in the air, the majority of which are left harmlessly astern, some of which react upon its own structure. Of these whirls and eddies practically nothing is known. Indeed, they are so little considered that it comes almost as a surprise to a practical designer to see the vast disturbances that become evident behind an aeroplane “ skywriting.”

The problems connected with the material used in the construction of aircraft are very numerous, and the time available in one lecture is far too short to consider them in any kind of detail. It seems to be more appropriate to approach the matter broadly and to consider some of the basic problems with a little thoroughness than to examine a number of details in a superficial manner. The main objection that can be urged against this method is that the conclusions reached are by no means confined in their application to aircraft materials, but apply almost equally to most of the arts in which the same or similar materials are employed. After all, the aeronautical engineer is mostly concerned to obtain the ideal sample of any chosen material.

If I were to take my title literally, my task would be light, and this paper would end here. For there is not, nor has there been for some six years, a Panel of the Aeronautical Research Committee on Scale Effect. It would be unfair to cast the responsibility for this error on our Secretary, as I could have changed the title when I replied to his letter asking me to read a paper before you. But as it did not seriously misrepresent the facts, and was less cumbersome than any alternative I could think of, I let it stand.

The Panel to whose work I am permitted to draw your attention is the Design Panel of the Aerodynamics Sub–Committee. It has been my privilege to be Chairman of this Panel for the last year or more. It may not be out of place to mention that the justification for its title is that it deals with the part of the Sub–Committee's work which most directly concerns the design of aeroplanes.