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Aviation History
1927
1927 - 0367.PDF
MAY 26, 1927 39 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT It is hoped that new methods of preventing peroxide? formation, and consequent detonation, may be discovered, when the properties of the peroxides have been more fully investigated. ON A MODIFICATION OF THE CHATTOCK GAUGE DESIGNED TO ELIMINATE THE CHANGE OF THE ZERO WITH TEMPERATURE. By W. J. DUNCAN, B.SC., A.M.I.Mech.E. R. & M. No. 1069 (Ae. 251) (5 pages and 1 diagram.) December, 1926. Price Qd. net. For the measurement of air speeds in pipes or wind tunnels a gauge known as the Chattock gauge is frequently used. In essentials this gauge consists of two cups containing liquid whose difference of level gives the suction pressure due to a given velocity. For ease of reading, an oil or similar surface of separation is used between the liquids in the two imps. The ordinary form of (Jhattock gauge develops a creep of the zero when the temperature varies, and this creep is due to thermal expansion of the liquids employed. The present type of gauge has an additional bulb which makes the gauge largely self-compensating. FULL SCALE TESTS OF A SUSPENDED AIR LOG. By J. K. HAHDV. K.A. Presented by the Director of Scientific Research. R. & M. No. 1074 (Ae. 250). '2 pages and 3 diagrams.) December, 1926. Price 4c/. net. The air log was designed to meet the need of an instrument which Mould record accurately the mean air speed under conditions such as are met with when the speed of an aeroplane approaches stalling speed. Under these conditions the limitations of control make it difficult for a reliable mean reading to be obtained from an air speed indicator or alcohol gauge. The air log records distance, and the true speed obtained corresponds to that obtained by continuously integrating the readings of an airspeed indicator corrected to standard density. A further advantage is secured in that the perishable rubber tube of the suspended static head is eliminated. The air log has been used for glides on a Bristol Fighter aeroplane, fitted with R.A.F. 30 section wings. Air speeds in the neighbourhood of the stalling speed have been recorded. The instrument has behaved satisfactorily, and the results obtained by its iise are in good agreement with those given by the standard method. In many cases it provides a better means of measuring speed than the suspended static head. FULL-SCALE PRESSURE PLOTTING EXPERIMENTS ON HULL AND FINS OF H.M.A. R.33. By LIEUT.-COL. RICHMOND. O.B.E.. of the Royal Airship Works, Cardington. R. & M. No. 1044 (Ae. 231) (26 pages and 30 diagrams). April. 1926. Price \s. 9rf. net. These experiments were undertaken at the suggestion of the Aeronautical Research Committee on the revival of airship construction in this country in 1924. The importance of a careful estimate of the aerodynamic forces which come into play on large, high-speed airships was emphasised by the R-38 disaster. Although it was possible to institute more searching investigations than had been carried out in the past into the pressure distribution on models, it was considered that there was insufficient experience with regard to the degree of accuracy with which such model results could be applied to the full-sized airship. The purpose of the investigation was to obtain an accurate estimate of the pressure distribution along one of the gener- ators of the hull and also over the surface of the fins for the purpose of comparison with model results. It was hoped by such a comparison to obtain a more accurate estimate of scale effect than exists at present with regard to pressure distribution on airships. No model data on pressure dis- tribution of an airship in circling motion exist at present. Results of pressure plotting experiments on a model of R.33 are given in R. & M. 801. Theoretical methods for obtaining the pressure distribution on a spheroid and applying this to the determination of the pressure distribution over the whole of the ship have also been worked out. The method for rectilinear flight is included in R. & M. 600 ; the method for curvilinear flight is included in R. & M. 780. It was hoped from the tests with R.33 in circling flight to investigate the degree of accuracy to be expected from the application of such theoretical methods. Observations were taken in straight flight at three different speeds and in circling flight with 5\ 10 and 15 rudder. In another series of experiments observations were made in pitched flight with excess buoyancy covering a range of pitch from 4'' to 12'. The results obtained are of great value for airship construction, especially in relation to two 5-million cub. ft. airships now under construction. Owing to the method of experiment there was a shift of the zero from which the pressure measurements were estimated, but it is expected that this shift was spurious. Making allowance for this effect, the curves obtained for the pressure distribution along the hull are in good agreement with existing model experiments. In the experiments on the fins the same shift of zero was observed, but the results cut out when comparing the pressures on opposite sides of the fin. The results in all cases agree well amongst themselves. ( urves of pressure distribution on hull and fins of the model are required for the case of circling flight (i.e.. on the whirling arm). Further full-scale pressure plotting experiments are required on a shape having a more truly ellipsoidal form (as, for example R.101) for the purpose of comparison with purely theoretical methods, which are based on the pressure distribution over an ellipsoid. In these tests a method should be devised which will eliminate the shift in the zero which has occurred with the present experiments. FULL-SCALE MEASUREMENT OF LIFT AND DRAG OF A BRISTOL FIGHTER WITH SLOTTED UPPER WINGS AND STANDARD LOWER WINGS. By J. K. HARDY. B. A. Presented by the Director of Scientific Research. R. & M. No. 1073 (Ae. 255) (3 pages and 3 diagrams). December, 1926. Price 4d. net. The present report is an extension of experiments on slotted wings previously published (R. & M. 1007).* Standard F.2B section lower wings were substituted for the Handley Page slotted wings on the Bristol Fighter aeroplane, which was used for the previous experiments. The large leading aerofoil only was used on the upper plane, and this was not altered. Measurements of lift and drag have been made over a range of incidence from 10c to above stalling. The maximum lift coefficient is 0-74, as compared with 0 • .54 for a Bristol Fighter with the standard F.2B wing section, and 0-86 with both wings slotted. The lift and drag of a model of the machine have yet to be determined. • R. & M. 1007. Full-scale and model measurements of lift and drag of Bristol Fighter with Handley Page slotted winus.—By E. T. Jones, B.Sc,and L. E. Caygill, B.Sc. These Reports are published by His Majesty's Stationery Office, London, and may be purchased directly from H.M. Stationery Office at the following addresses : Adastral House, Kingsway, W.C. 2; 28, Abingdon Street, London, S.W.I; York Street, Manchester ; 1, St. Andrew's Crescent, Cardiff ; or 120, George Street, Edinburgh; or through any book- seller. 330*
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