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Aviation History
1913
1913 - 0662.PDF
I/O GHT 06 at 150. The aspect ratio for which these values were obtained was 6 to i. Some experiments have also been made on wing sections, of which the surfaces are reflexed towards the trailing edge, in order to determine whether a reduction in the movement of the centre of pressure could be secured by this means. The experiments are not yet completed, but it appears probable that it will be possible to confine the movement of the centre of pressure within very small limits. As is to be expected, there is some loss of efficiency, but this is not of very serious amount. A complete series of measurements has been made to determine the forces and moments acting on a warped aeroplane wing. The observations showed that no loss Of lift resulted from warping at ordinary flight angles, but, as was to be expected, there was some increase in resistance. The effect of the movement of the centre of pressure for variation in the angle of incidence was negligible, and the lateral force tending to produce side slip was quite small. As regards the rolling and yawing moments at small angles of incidence, the result of warping is to give a maximum rolling moment with practically no yawing effect, which is exactly what is required in practice. As the speed of the machine decreases and the angle of incidence increases, the effectiveness of the warp control gradually diminishes, while the yawing increases. Further experiments have been made on aeroplane struts, including a systematic examination of a series of struts with sections of different fineness ratio. These tests, says the report, are of great theoretical and practical interest, and throw light on various points that arise on the one hand in connection with the design of airship JUNE 28, 1913. envelopes, and on the other hand in relation to the tests of wings. The strut tests confirm the view expressed at an earlier date that the upper surface of a wing is of paramount importance, the effect of modification of the under surface being relatively small. Discussing the subject of stability, the report refers to an interesting phase of the subject, brought to the fore by Mr. Lanchester and by M. Alexandre See, that too high a degree of stability in relation to small disturbances is not a desirable quality in an aeroplane, and that the con dition to be aimed at is one of nearly neutral equilibrium. This view is entirely in accord with previous experience, in other problems of locomotion, among which may be mentioned the classical examples of the stage coach and the ship. In the former, too low a position of the centre of gravity, in the latter too great a metacentric height, were found to lead to unpleasant rolling motion. It will be evident, the report continues, that if, as is to be expected, the well-known theory that explains the cases cited is equally applicable to the aeroplane, it will be necessary for the conditions affecting stability to be determined with the highest possible exactitude, and with the utmost completeness, as somewhat nice adjustment will be necessary to attain the desired balance of opposing conditions. Whether as regards longitudinal or lateral stability, it would, from analogy, appear necessary that an aeroplane should be stable, but that its stability factor should not be too great. We note that emphasis is laid on the need for an increased expenditure both on apparatus and staff at the N.P.L., and we hope that the Government will not stint the money for this good work, particularly in view of great scientific activity prevailing abroad. SHOREHAM HARBOUR AS SEEN FROM ABOVE.—From a photograph taken by Mr. Clarence Winchester from Mr. Eric Pashley's biplane. 688
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