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Aviation History
1914
1914 - 0482.PDF
1705m] 6 per cent., or even 5 per cent, may prove to be attain able. Body resistance was then dealt with, and under the heading of total resistance it was shown diagram- matically how soon with increased flight speeds the question of body resistance becomes a dispropor tionate factor; but, as will be readily understood, with increasing weight and power of the machine, the effect of such body resistance may be rendered less important, since an increase in weight and power does not require a proportionately serious increase in the size of the members to which the body resistance is due. The author calls attention to an important matter in this sub division of his paper, as it illustrates the extent to which theory can anticipate the results attainable in actual practice. As far back as 1907 he tabulated the results of calculations for gliding angles as ranging for complete machines from 12" (approximately 1 in 5) to 6° (1 in io), and the worst gliding angle recorded in the Military Trials was 1 in 5-3, while in present day practice the smaller angle is gradually being reached. The questions of Propulsion and the Motive Power Installation next received attention, after which the design of the aerofoil and the arrangement and structural features of the machines were discussed, and two methods of calculation of stresses in the aerofoil members were outlined—one in which the aerofoil struts are treated as being pin jointed members, and the other in which the theory of continuous girders is applied to the main longitudinals. A memorandum on the latter method, which has been developed by the staff of the National Physical Laboratory and adopted by the Royal Aircraft MAY 9, 1914. Factory and various manufacturers, will be included in the Advisory Committee's Report for 1912-13. ^This memorandum should be of value because, as the author remarks, while the pin-joint hypothesis usually gives results that are on the safe side, the extent of the factor of safety so introduced cannot be relied upon. Reference was made to the vertical fin effect of the propeller, from which it appears that the "propeller equivalent in terms of vertical surface is a very large and serious factor, and one that under no circumstances should be ignored." This will also be published in the Advisory Committee's Report and is the result of an investigation carried out by Mr. T. W. K. Clarke. Attention was then directed to the dynamic loading of the planes and the factor of safety that should be employed ; and after various types of landing gear had been discussed, the Acentric type of machine, that is, one in which the line of propeller thrust is situated consider ably above the centre of gravity and probably above the centre of resistance, and its behaviour in flight under certain conditions was considered. The paper con cluded with a reference to stability and control, which is more or less merely an index to the various literature that has appeared dealing with this question, but an appendix is added relating to skin friction. We feel confident that our readers will, when it is pub lished in our pages, read this paper, which is copiously illustrated by diagrams, with great interest, and it should stimulate the desire for an early perusal of the forth coming report of the Advisory Committee, which, as is now well known, will contain much valuable and useful information. O/ w A snap of M, C. Howard Pi.en f,yinB tne S^wlth^W at Monaco d^ng^ec^, flight for the 4S2
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