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Aviation History
1918
1918 - 0715.PDF
JUNK 27, 1918, SOME OUTSTANDING PROBLEMS IN AERONAUTICS.* By Dr. DURAND. SIR WILLIAM WEIR, Secretary of State to the Air Ministry, who presided at the sixth Wilbur Wright lecture, in openingthe proceedings, announced that the King had been pleased to grant permission to the Aeronautical Society-—the oldest aeronautical society in the world, having teen founded in 1868—to be known in future as the Royal AeronauticalSociety. His Majesty recognised the importance of the work which the society had performed in the interest of the nation. Sir William Weir then went on to pay a much merited tribute to the skill, ingenuity, and capacity of our aircraft designers.He said that our policy of entrusting the design to the industry itself has been very successful, and the country owes a deep debt of gratitude to those firms who are devoting so much skill to the development of our designs, and more particularly thosepioneer firms who worked so many years without any immediate prospect of reward. During the past three years of war, that great advance has been accelerated, and designers and engineers in this country had played an outstanding part in thisprogress. Their combined achievement was one to be proud of. Our technical superiority over the enemy at the present time was equalled by the superiority of the human qualities of skill, enterprise, endurance, and pluck displayed by our pilots. In aerial warfare, the assistance the United States had already rendered us in the way of personnel was very great. Herofficers and men had won golden opinions from all with whom they had come in contact. The universal opinion was that they were unsurpassed in their energy and modesty, and for their willingness to learn and their desire to co-operate in everything.So far as personnel was concerned, they entertained the fullest confidence in the future success of the American Air Force. With regard to material, we might now begin to speak with equal confidence. The tests which had recently been applied inFrance and in this country, to the latest American engine j ustified them in predicting 1hat it would prove a most valuable contribution to the Allied resources, and the United States could go ahead and push its production with every confidence.The results of experiments so far obtained placed the engine in the very first line of aero motors. It was well understood that some criticism would be directed against the slowness of production of these motors during the last three or four months.Every engine, even the best designed in the country, with the greatest resources and facilities, could not escape a period of what was called teething troubles, before the motors were produced on anything like a large scale. The Liberty engine was anexample of what the Allies might expect in the matter of aircraft production from the scientists and designers of America whom Dr. Durand represented. The various methods of utilisation of aircraft in warfare were growing very rapidly—so rapidlythat even with all the help that America could give, the fullest demands which could be made to fulfil all the different functions of aircraft would never be met during this war. We should always require more aircraft with personnel than could possiblybe supplied to-day. Dr. Durand then gave his lecture as follows :— Under the circumstances which have determined the direc- tion and character of the development of the aeroplane during the past decade, and especially under those which have been controlling during the past three or four years, it is only to be expected that at the present moment we should find ourselves with many partly solved problems on our hands, with others which we have hardly more than begun to attack on the outskirts and confronted by others still, the character and significance of which we have hardly begun as yet to apprehend. The Problem of Constructive Materials. Perhaps nowhere is there to be found a better illustration of the interdependence of technical and scientific research and study than in the manifold advances in various technical and scientific lines which conjointly have made the aeroplane in its present form a structural possibility. Broadly, the modern aeroplane comprises a body of some sort or form fitted with wings to provide the supporting surfaces, with a prime mover or source of power and with a propeller of some type to transform the power provided by the prime mover into propulsive work, and, by the reaction of the relative air stream on the under-side of the wings, to secure the sustaining or lifting force necessary to carry the weight. This construc- tion calls for a wide range of constructive materials. Thus the body and wings, comprising the aeroplane proper, require the following fairly distinct classes of structural elements :—(1) Those intended primarily to give form, strength and coherence to the structure. They represent in effect the skeleton or foundation on which the entire function of the aeroplane as such must depend. (2) Various secondary elements intended to [so tie or connect the principal members together as to secure homogeneity of structure as a whole, and mutually responsive action on the part of the different elements com- prised under No. 1.—The elements here considered are those which, from a purely structural view-point, may be classed as struts and ties or tension members. (3) Surface covering for the body and wings. This gives outer form and continuity of surface and provides furthermore the actual surfaces on which the air lifting and supporting forces may act. Broadly speaking, the fundamental problem in all aeroplane construc- tion is adequate strength or function on minimum weight. In no other form of engineering construction is the necessity forweight-saving so rigorous. In a very real sense every ounce of material entering into the structure must be able to show a competent passport. The structural problem of the aero- plane is therefore one of strength in relation to weight. For the main elements comprising the skeleton of the structure, wood has, thus far, held the main place with metal construc- tion steadily attracting more and more interest and assuming a place of growing importance, at least in the study of new designs. It is not necessary to our present purpose that we should consider in detail present practice in aeroplane construction. The trend of development since the earliest days of the art has • The Sixth Wilbur Wright Lecture, read at the Central Hall, Westminster _ 00 June 25th. tended to show that wood construction under suitable designand safeguard was able to provide the easiest and on the whole the most satisfactory solution of the many problems andrequirements which aeroplane construction presents, and so we have been content, for the most part, with this type ofconstruction. We may, however, be well assured that however good may be any solution which we may reach of themany problems presented to us in the industrial arts, there are, as a matter of fact, series of better ones only awaitingour patient study. This is indeed a fundamental truth of which we should never lose sight. We may be, for the moment,satisfied with our solution of a problem in technical industry ; we may be able to see nothing better, and yet we may be wellassured that, as a simple matter of fact, there is something better. This is a perfectly safe assertion, if only as based onthe law of probability of our having, at any given time, reached the final optimum possible combination capable of furnishinga solution of the problem. Thus, as applied to the problem of constructing the framework of the fuselage of an aeroplane orof combining together wing spars and ribs in such manner as to form a wing skeleton, we may be sure, however good ourpresent practice may be and however satisfactory it may seem, that in reality it is not the best and that long series ofbetter solutions only await our intelligent and patient study. In this and in all such problems there are always two fairlydistinct though inter-related parts: (a) What materials are best suited to the purpose in view, (b) What disposition shallbe made of the materials adopted. Thus, in the case of the fuselage, granting wood material to be adopted, there remainsthe question as to the very best distribution of such material as between the main longitudinal elements, or longerons,and the intermediate elements ; also as to the extent to which reliance may be placed on the outer covering, especially if ofply-wood. What aeroplane designer can feel sure that, even with given materials, he has reached the optimum distribu-tion of function as between the main and secondary elements of the fuselage and of a ply-wood outer covering ? Muchless, what aeroplane designer can feel any confidence in having now reached an optimum combination, once we admit thepossibility of metal construction, or of seme combination of metal and wood, with all the possibilities of the new lightmetal alloys and of the new alloy steels with their astonish- ing physical characteristics. So far as conditioned by theapplication of the ordinary loading tests, static in character, and aside from the possible results Of dynamic attack, shock,long-continued vibration, &c, we may perhaps frankly admit that the present state of metallurgy is able to supply us withmaterial, either in the way of light aluminium alloys or special steel alloys, which if properly used, will enable us to meet allsuch static tests in an aeroplane construction, and on even terms or better as regards weight compared with wood. Ifsuch is the case, it certainly stands before us as a problem for the near future to pass in review most thoroughly the entirerange of constructive materials, metallic as well as wood, and to determine, in the light of the experience which we are so. 713
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