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Aviation History
1925
1925 - 0135.PDF
MARCH 5, 1925 AERONAUTICAL RESEARCH COMMITTEE REPORTS FROM the number of enquiries we receive it appears that there is a desire in aircraft circles to Lnow approximately the contents of the various technical publications of the Aeronautical Research Committee. All the aircraft firms probably receive these reports regularly, whether or not they contain anything of immediate interest or utility. In the case of draughtsmen, however, and others interested in aeronautics who cannot afford to purchase all the reports, the problem of deciding whether any publication interests him is often a difficult one. As it is obviously desirable that the knowledge of aeronautics should be made available to all who take an interest in the subject, we have arranged with the Air Ministry to publish in FLIGHT summaries of all the technical publications as soon as these are issued, or shortly before they are published. All A.R.C. publications can be purchased from H.M. Stationery Offices at Adastral House, Kingsway, London, W.C.2 ; 28, Abingdoii Street, London, S.W.I ; York Street, Manchester ; 1, St. Andrew's Crescent, Cardiff ; 120, George Street, Edinburgh, and through any bookseller. Reports and Memoranda, No. 929 (Ae. 151). Some Experiments on a Slotted Aerofoil. By H. B. Irving, B.Sc, and A. S. Batson, B.Sc. Price Is.'net. Messrs. Handley Page initiated some years ago a wind tunnel research on the properties of slotted wings, having as its object the increase of the maximum lift coefficient, or, in other words, to obtain the maximum lilting capacity of an aeroplane for a given area of wings. Summaries of these results have been published in Reports and Memoranda, Nos. 834 and 930. The present paper is a continuation of this work at the National Physical Laboratory on an aerofoil measuring 6 in. by 36 in., f.t "K.A.I-". 15 section, with a single slot. A systematic exploration ot the effect of varying the position of the leading aerofoil (corresponding with the portion of the wing in front of the slot) in relation to the main aerofoil has been made over a range ol wind speeds between 20 and 90 ft./sec. In addition, some autorotation experi- ments were made for comparison with similar experiments on the standard K.A.F. IS aerofoil. As a result of variation in the position of the leading aero- toil the maximum lift coefficient was increased from the figure for maximum lift coefficient of 0.85 obtained by Messrs. Handley Page for the same sections of main and leading aerofoils to nearly 0.9. The speed effect on the arrangement tested was found to be considerable at the lower speeds, but between 65 and 90 ft. see. it was very slight below the stall and not great above the stall. The maximum autorotative couples on the slotted aerofoil were nearly four times those on the R.A.F. 15 aerofoil ; the range and speed of autorotation were also much greater, although autorotation did not begin until a large angle of incidence was reached. There is a possibility that difficulty in control may arise at low speeds with the full-scale aeroplane, and such is indi- cated by the model experiments and needs investigation. The model research will be continued at the X.P.L. on the sections K.A.F. 26 and 31. Reports and Memoranda, No. 937 (Ae. 158). Measure- ments of Lift, Drag, and Pitching Moment on the 1 '5th scale Model of the Bristol Fighter with Airscrew running. By E. F. Kelt. ARC.St., and L J. Jones. July, 1924. Price 1>. net. The usefulness ol model work depends upon adequate comparison tests between the model and the full-scale aero- plane. From the nature of the full scale tests, it is cleany impossible to test a large number ot aeroplanes, and accord- ingly some particular aeroplane is chosen every few years tor careful comparative work on the two lines. A summary of comparisons so made is given in the Report of the Design Panel (K. & M. 900) on the scale effect on lift, drag and C.P. of complete aeroplanes and an earlier report of the scale effect Sub-Committee, R & M. 374. Further work is being conducted on the Bristol Fighter aeroplane, both full-scale and model. The present report is a continuation ot the work described in an earlier paper. Reports and Memoranda, No. 876, which presented the results of measurement of lift, drag and pitch- ing moment on the Bristol Fighter at angles below the stall. In those experiments the airscrew was not present, except in one series of measurements, which was made with airscrew stationary for direct comparison with gliding tests at the Royal Aircraft Establishment The tests of the present report can be briefly summarised as follows :— (1) Lift, drag and pitching moment with airscrew stationary, at angles above the stall. • • , £ (•>) Similar measurements at all angles ol incidence from 0* to 36 with airscrew running at various values ol VnD, with various tail and elevator settings, and without tail. (3) Torque measurements on the airscrew under the <."ii- ditions of (2). (4) Thrust and torque of airscrew alone, with a " minimum body " to enclose the motor. The results are mainly given as tables, but a few have been plotted in illustrative figures. Reports and Memoranda, No. 940 (Ae. 161). An Analysis of the Pressure Distribution on a Model Airscrew by Means of the Vortex Theory. By A. Page, A.R.C Sc. November, 1924. Price 6r/. net. Several papers have been published in the Reports and Memoranda series on the application of the Prandtl vortex theory of aerofoils to the case of an airscrew. The original papers on this; subject are R. & M. Nos. 786 and 869, and the general accuracy with which the theory therein described predicts thrust, torque and the distribution of thrust along the blade has been considered in a further paper, R. & M. 892. In this last, comparisons have been made between theo- retical and experimental results for a number of airscrews belonging to the same family. The pressure results now analysed include determinations of thrust and torque for each blade element at the working conditions of maximum efficiency, climb and zero advance, and so permit a close examination of the theory against practical data for the particular case of an airscrew of medium pitch. It is found that the vortex theory when applied to this airscrew over-estimates the thrust by amounts which vary from 12 per cent, at zero advance to 5 per cent, at maximum efficiency. The measured and calculated values of the torque agree within 3 per cent., except at zero advance, where the error amounts to 7 per cent. Comparisons with the results of the pressure experiments show that both the thrust and the torque at the tip are considerably over-estimated. It is shown that better agreement with experiment is obtained if the theoretical values of the translational inflow factor are increased at the tip sections. A comparison of pressure diagrams indicates, however, that the discrepancies at the tip cannot be completely accounted for by an under-estima- tion of the translational inflow factor. Reports and Memoranda, No. 928 (Ae. 150). Test of Four Thick Aerofoils, R.A.F. 30. 31. 32, and 33 By F. B. Bradfield, Math, and Nat. Sci. Trip., and A. S. Hartshorn. B.Sc. September. 1924. Price 6d. net This report describes a routine wind tunnel test on lour thick aerofoils, the theory of the design of which has been described elsewhere in Reports and Memoranda No. 946. R.A.F. 30 is a symmetrical section, twice the thickness of R.A.F. 15. R.A.F. 31 and 32 are derived from R.A.F. 30 by curving the centre line to circular arcs of cambers 0-02 and 0 05. R.A.F. 33 is derived from R.A.F. 30 by using a reHexed centre line of the same camber as R.A.F. 32, and is designed to have a fixed centre of pressure. Lift, drag, and centre of pressure were determined at VL = 40 on aerofoils of 8-in. chord and 48-in. span, and lift and drag also at VI. -— 53-3. The main characteristics at YL -^ 40 are given below. The results for R.A.F. 15 measured in the same channel (6-in. chord at V ---- 80 ft./sec.) are added for comparison. R R Aerofoil .A.F. .A.F. 30 ... 31 ... 32 ... 33 ... 15 ... AY max. 0-415 0-52.S 0-656 0-620 0-531 kD min. 0-0054 0-0065 0-0083 0-0087 0 0063 k -0- -0- -0- -0 -0 MO. 003* 029 067 •009 •014 L u ma 18-2 19-1 18-1 17-5 20-5 It is understood that full-scale experiments will be mack with the sections R.A.F. 31 and 32. * Measured value, due to assymetry of model. 135
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