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Aviation History
1923
1923 - 0104.PDF
wireless, but within this radius further position finding becomes difficult. A scheme is being tried at Croydon whereby the position is rapidly taken by sound and the information transmitted to the aeroplane by wireless, thus relieving the pilot of the necessity for asking for his position when he i s much occupied with flying the machine. Moreover, the lapse of time between taking his position and giving him the information is reduced. The problem of actually landing through the fog remains, and we are now investigating the possibility of laying a cable carrying an electric current round the aerodrome convenient for an aeroplane in flight to follow. The aeroplane will carry apparatus capable of detecting it and of measuring the energy received. The amount of such energy gives an inverse measure of the height. By this means, it is hoped to enable the pilot to locate the actual confines of the landing ground, and, finally, to glide down, even in conditions of very low visibility, with an accurate knowledge of his height at any given moment. The disadvantage of this method is in having to carry apparatus which will only be used for a few minutes on a small minority of flights. Electrical methods of fog dispersion are being tried on a small scale, and have given certain results, but to do this on a large scale is a more difficult problem. Aerial Survey.—The value of aerial survey is largely dependent upon the accuracy with which the camera can be held vertical and at a known constant height. To determine the probable degree of accuracy, a series of experiments has been carried out by Prof. B. M. Jones and Major J. C. Griffiths ; the method consists in photographing a strip of flat and conspicuously marked country. From a comparison of the photograph and a map of the country, the tilt of the camera and the height above ground may be checked by noting the relating distortion of opposite sides of the plate and by a comparison of the scales of map and plate. FEBRUARY 22, 1923 Considerable progress has been made in the art of aerial photography since 1914, and photographs have now been taken from 8,000 ft. in which it is possible to distinguish birds feeding on the ground. A film camera, replacing plates, is now under development, which, if successful, will save weight and space. At present we are dependent for our supply of film on sources which are outside the British Empire, a factor which must be taken into account before a film camera can be standardised. Foreign-made flying and engine instruments for test purposes have now been replaced for the first time by a complete series of British instruments of equal or greater accuracy. Wireless.—Progress is being made in the use of fixed wireless aerials in aircraft, which have great advantages over trailing aerials, and are particularly applicable to large airplanes. They should be of special utility to civil aircraft. Such aerials are operative even when an aircraft is taxying, and will facilitate " position finding " under conditions of very low visibility, and also fog landing when a trailing aerial could not be used. Progress in directional wireless continues, the plains of Iraq and the Middle East generally proving ideal for this work, the errors in bearings from natural causes being negligible. The abolition of accumulators in aircraft on account of their weight is a difficult problem, which has received much thought during the past year. The two main difficulties are to drive wind-driven generators at constant revolutions irrespective of the air speed of the aircraft, and to provide a source of electric supply to aircraft when stranded. Both these problems are now well on the way to solution. In the concluding part of his paper the author gave a review on the research work carried out on materials—fatigue of metals, use of light materials, etc.—and on inspection methods. GLIDERS AND THEIR VALUE TO AERONAUTICAL PROGRESS By Colonel ALEC OGILVIE, C.B.E., F.R.Ae.S. Early Experiments.—The interest of man in the flight of birds goes back to very early days and although "to fly " was commonly considered to be an impossibility until quite a few years ago, numberless men watching birds sailing along with motionless wings have expressed disbelief in the impossi- bility of such a feat for human beings. There can be no doubt that in several cases, some many hundreds of years ago, attempts to glide met with partial success, and nothing is more astounding to a student of aeronautical history than the immensity of the effort in money, in time and in brains of a high order of excellence, which has been put into abortive experiments in aeronautics. These experiments ranged from model flying machines which were frequently successful to full-scale efforts which were invariably failures. The reason for these failures is to be found in the essential difficulty in making the first flight. As it was not thought possible to work up gradually to a successful flying machine, numerous problems of lift, resistance, power, stability, control and starting all had to be solved simultaneously, and failure in any one particular caused failure in the whole. It was, in fact, necessary for the flying machine to reach a considerable degree of develop- ment before it could work at all. About 1875 a German and an engineer, Otto Lilienthal by name, became convinced, after studying the flight of large birds, that the principal obstacle in the way of human flight was lack of practice in the art of flying, and after a series of laboratory experiments lasting several years, with wings of various shapes and curvatures, he embodied his results in a glider or rather a series of gliders with which he made at least two thousand flights between 1891, when the full-scale experiments commenced, and 1896, when he was accidentally killed. The importance of the work of this man to the progress of aeronautics cannot be over estimated. In fact, he is justly considered to be the originator of the modern flying machine. When the Wrights took up gliding, they did so purely from a sporting standpoint, but they showed from the begin- ning that they had a very clear grasp of the problem, and that they appreciated that the heart of the difficulty was control in the air, both lateral and fore and aft. Their machines were simply-made biplanes of ample strength, and the design of which progressed from year to year as knowledge of the requirements was obtained. This problem of control was far harder than they had anticipated, and it took these two very exceptional men three years' work with gliders and models before they dared to attempt a power-driven machine. The deduction which the writer would wish to make from this is that the control problem might well not be solved at this present day, if it had not been for the availability of the glider as an instrument to get at the fundamentals of the problem in a simple, inexpensive and reasonably safe manner ; since the fundamentals are known, their application to attain practical results is quick and easy. Development of Practical Flying.—During the War period lives, brains and money were freely spent to meet the rapidly increasing requirements, and the expansion in the four years was to be measured in hundreds of fold. If the War had continued for another year or two, it was to be expected, judging by the rapid rate of progress, that the aircraft weapon would have predominated over all others. From the technical standpoint the necessity of maximum, performance in speed, in climb, and in weight-carrying was so paramount that other aerodynamic qualities were perforce neglected. It was futile to spend much time improv- ing any particular type of machine, in the direction of better control, or of greater economy or safety, when the same result or nearly the same result could be obtained by putting a more powerful engine into the same machine or by designing another machine to take the bigger engine. Demands upon the pilots for greater skill in landing and in controlling their machines were promptly met. Another noteworthy result of this intensive activity in design was the standardisation of such wing sections as gave specially good results from the performance point of view. Judging from some recent trials, details of which the writer is not at liberty to give, it would appear that it is fully time that the designers of this country should seriously turn their attention to wing sections other than the standard ones. There is A clear piece of evidence that very considerable improvements in all-round results can be obtained with a thick-sectioned monoplane over the thin-sectioned biplane standardised in this country. Present Position of Aeronautical Development.—It must be understood that the writer is looking at this matter from the point of view of aircraft for civil transport purposes. From this standpoint, the present position of aeronautical develop- ment cannot be considered to be satisfactory. Civil aircraft are not sufficiently safe in the event of a break- _ down of the motive power, necessitating a forced landing." They are also much too expensive to buy, to run and maintain in running order, and until very considerable improvements can be effected in this respect it cannot be claimed that they are transport vehicles of a really commercial character. It is hoped that these remarks will not be misinterpreted. 104
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