The present Paper is a record of experimental work carried out with a view to overcoming the phenomenon of “ burbling.” As is well known, the total pressure on an aerofoil is the sum of the positive pressure on the under side and the negative suction on the upper. If this negative suction can be made to increase progressively with increasing angle of incidence to angles greater than heretofore, the maximum value of the aerofoil lift coefficient will be increased. The effect of such an increase on aeroplane design depends upon the magnitude of the increase and the extra structure weight of the device necessary to obtain it. The present method which, is now described has been evolved from experimental data, and an outline of the results is given below.

In a Paper which I read before the Royal Aeronautical Society in April, 1911—ten years ago—I attempted an analysis of the somewhat meagre results then available on the pressures on plane and curved surfaces moving through the air.

Arithmetic. —The principles and processes of arithmetic applied to whole numbers and vulgar and decimal fractions. The metric system. Approximations to a specified degree of accuracy. Contracted methods of multiplication and division of decimals. Ratio and proportion. Percentage. Averages. Practical applications of arithmetic. Algebra.—Symbolical expressions. Equations of the first or second degree (and problems leading thereto). Square root. Graphs of simple rational integral algebraic functions. Arithmetic and harmonic progression. Geometric progression. Theory of indices. Logarithms. Theory and use of the slide rule. Binomial theorem for a positive integral index. Geometry.— The subjects covered by Euclid I.-IV. with simple deductions, including easy loci and the areas of triangles and parallelograms of which the bases and altitudes are given commensurable lengths. (Euclid proofs will not be insisted upon.) Trigonometry.—Up to and including the solution of triangles, together with the practical solutions of triangles and applications, and numerical examples involving the use of logarithmic and other tables.

I feel it a great honour to have the privilege of addressing the members of the Royal Aeronautical Society on the subject of Airship Piloting, especially in view of the interest you have taken in furthering and generally assisting in the development of all types of aircraft.

Although the airship has hitherto not occupied the thought and brains of Aeronautical Engineers to the same extent as the aeroplane and seaplane, I feel sure the confidence and support of the Society will lead to a more general and scientific interest being taken in lighter-than-air craft, which is bound to result in more rapid progress in the near future.

I hope the discussion to follow will provide the foundation for solving some of the problems that will have to be faced, when piloting the airships over routes to various parts of the world, where totally different atmospheric conditions are likely to be encountered.

An earlier article dealt with so many matters in connection with wire cables that it was possible to pay but scant attention to sockets. A socket is a neat, light and convenient form of end connection for a cable. It is widely employed in general practice, but its use in connection with aircraft appears to have been confined to airships. The photograph shows different types and sizes of sockets viewed in several directions.

The design and construction of light hulls and floats suitable for flying boats and seaplanes is a very highly specialised branch of shipbuilding. This being the case, all matters pertaining to same Should be in the hands of naval architects. At a recent lecture before this Society, Commander Hunsaker, of the United States Navy, stated that British aircraft designers followed the naval architect's methods more than in any other country; he thought this was natural as he gave us the credit of being the first maritime power of the world. This may be perfectly true with regard to airships, but I cannot endorse his opinion that the majority of flying boats built in this country show the impress of the trained hand of a naval architect. I do not imply that the American boats are superior to ours, as for instance, a large American boat with twin engines built in the United States, which we used for the North Sea patrol, was by no means typical of good boat-building ; there were no less than four consecutive planks butted—not even scarfed—on the same timber, which had a siding of 5/8in., the line of butts being in line with the step where the boat was naturally weakest.

The Air Ministry, in granting me permission to deliver this lecture, have asked me to make it clear that “ the statements made are based entirely on my own knowledge and the opinions expressed in no way reflect the official views.” I should like to acknowledge the courtesy of the Air Ministry in giving me permission, and to say that I should be surprised if some of my opinions were in accord with the official view.

Towards the end of the war, although submarines were still doing a considerable amount of damage to shipping, the Navy was rapidly getting their measure.

Submarines were being sunk faster than the enemy could build ; their submarine service had been made so hazardous that it was increasingly difficult for the enemy to man their submarines and maintain the morals of the crews during attempted operations.

This result was not achieved by any one arm of the Navy, nor by any particular invention, but was effected by the intensive use and close co-ordination of praqtically all the resources which the Navy could command.

It is a very great honour to me to have to speak this evening before this learned assembly, and I have to thank you very sincerely for the occasion which you have offered me of discussing before you a very important question, one which is of interest to the whole of the aeronautical world, namely, the problem of the helicopter.

My aim will be but modest, for I shall simply attempt to develop those essential arguments which have given me such entire confidence in the practicability of this type of heavier-than-air machine, and I shall be content if at the end of this paper I have been able, not to convince you, but at least to interest you in the cause which I have at heart.

The helicopter is not a competitor of the aeroplane. It is an entirely different type of aircraft, but the one is the complement of the other, and if their respective uses are not the same, they nevertheless will be of equal importance in that immense future which we all believe to be reserved for aircraft.

The development of aircraft during the war was such that a new and reliable means of transport had come into existence before the Armistice was signed. It possessed the supreme advantage of greater speed than any other form of public transport, although the commercial possibilities of the new service had still to be proved.

A committee was formed under the chairmanship of Sir Frederick Sykes, and as a result of a series of meetings held during March and April, 1919, framed the first Air Navigation Regulations and the directions issued thereunder, which became a part of the law of the land on April 30th, 1919.

In this paper I propose to deal with the sections of the regulations and directions concerning ground engineers.

In the following paper the writer's aim is to indicate certain possible lines of development and research which his own investigations and preliminary experiments have shown to be at least worthy of serious consideration.

If we review the present state of the art we find the position to be substantially as follows :—From a thermodynamic point of view the performance of the modern aero engine has approached so nearly to the ideal obtainable from the cycle on which it operates that there is little scope for improvement.

The Cairo-Cape flights of 1920 brought into prominence many peculiarities of conditions arising from the high temperature combined with high altitude ot the aerodromes on the route. The conditions were for the most part new, for flight from elevated aerodromes in Europe and the United States has been made as a rule in temperate climates, where the temperature at such altitude was low. These peculiarities, which led to great difficulties for the pilots, may be divided into two classes :—

(1) Engine peculiarities, especially defects of carburation and unequal heating of the cylinder jackets owing to the high temperature of the air.

(2) Aerodynamical peculiarities, owing to the tenuity of the atmosphere. In the former class the difficulties were not to be foreseen, and much valuable information has been obtained as a result of these flights.

The latter class of difficulty, on the other hand, was one that could have been predicted with certainty by anyone who has had experience in the testing of the performance of aeroplanes under varying conditions of the atmosphere.

All methods of transport must be judged by their cost of operation and the revenue they produce, and the comparison, therefore, of the cost of ton-miles provides a useful but not the only basis from which conclusions can be drawn as to the efficiency and utility of such services. Vehicle, train, ship, or air miles and their cost must also be considered as well as ton-miles, and above all the factors of speed and the completeness of the service from the point of view of the user must be taken into account.

We have seen during the last few years attempts made to bolster up certain methods of transport on the ground that they are beneficial as a whole to the community, to special trades, or to the welfare of particular places or classes. But sooner or later the practice of subsidising any kind of transport out of taxes or rates, or out of the proceeds of other allied concerns, will have to be recognised as unsound, though there are exceptional cases where one service is naturally complementary to another kind of service, and in the end the methods of transport that will survive will be those that can stand upon their own bases.

In his recent lecture on “ Airship Mooring and Handling,” Captain Butcher refers to certain experiments carried out with the use of models in connection with three-wire mooring. It is, perhaps, useful to add some further details of these special experiments, which were conducted at the National Physical Laboratory.

Mention was made by Captain Butcher of the original or “ fixed ” three-wire system (see Fig. 1), which originated from the emergency mooring of R.9. Its defects lie in the occasional slackening and subsequent impulsive tightening of one or more of the mooring cables when the airship is riding in gusty weather. In the particular modifications introduced by the N.P.L., breakdown due to this contingency is eliminated.

In my last lecture I promised to try and show how the pilot can foresee and effectively eliminate practically all the danger which attends the art of flying. You will probably notice that most of the danger arises, at least indirectly, from some misbehaviour of the engine; so that in estimating the danger I shall be compelled to lay considerable emphasis on the possibility of engine failure, in spite of the fact that it is comparatively remote. If we look back to the infancy of any mechanical means of locomotion, we realise how unreliable it was in the initial stages; we may therefore look forward with absolute confidence to the future reliability of the aero engine and its installation.

Every day almost marks an improvement, and if the early pioneers who lost their lives could trace its development what surprise they would express ! At the same time the possibility of one unreasonable engine failure is a menace to the whole of flying, which cannot and must not be blinked at.

Flying is an art. A pilot may actually fly a small manoeuvrable aeroplane of the present day without knowing much about aerodynamics, just as a musician may draw exquisite music from an instrument without a knowledge of the laws of sound. There is a flying instinct just as there is a musical instinct; an unerring perception of the modes and measures of the art ; a subconscious obedience to laws which are at most but dimly realised. I do not say that a pilot can design a successful aeroplane without a certain knowledge of the fundamental truths of aerodynamics, of the distribution of stresses in a structure, any more than a musician can compose a sonata without a knowledge of the laws of sound, the laws of harmony and counterpoint, the practice of great masters in the traditions of sonata writing ; but I do maintain that he can fly the aeroplane.