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Aviation History
1929
1929 - 0865.PDF
APRIL 25, 1929 35 THE AIRCRAFT ENGINEER SUPPLEMENT TOFLIGHT The procedure for the right-hand side of the nomogram i.e.. core properties, is similar except that, of course, the core sectional area of the bolt is used instead of the full sectional area. TECHNICAL LITERATURE SUMMARIES OF AERONAUTICAL RESEARCH COMMITTEE REPORTS 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. EXPERIMENTS ON THE DESIGN OF AX AUTOMATIC SLOT FOR R.A.F. 28 SECTION, AND ON INTER- CONNECTION WITH AILERONS. By F. B. Bradfield, Math, and Nat. Sci. Triposes, and K. W. Clark, B.Sc., D.I.C. Presented by the Director of Scientific Research, Air Ministry. R & M. Xo. 1165 (Ae. 329). (20 pages and 14 diagrams.) April, J928. Pricela.net. The investigation aroge in connection with fitting an autoslot system tothe " Atlas," and includes the development of a system of interconnecting i he slot «ith tbo ailerons.The free settings and lift have been measured for a 12 JKT cent, auxiliary on a wing of R.A.F. 28 section, with a wide range of variation of linkages,and the drag and centre of pressure of the slotted wing were measured in some cases. Boiling and yawing moments have been measured for twolinkages for the autoslot, and for the interconnected autoslot and ailerons, The forces necessary to work the interconnection have been determined,and the force on the auxiliary aerofoil measured. The maximum lift coefficient obtained was 0 75, the stall on the slottedtip being delayed to about 8° greater incidence. The simple autoslot improves the aileron control somewhat by Increasing the rolling moment, but theratio of yawing moment to rolling moment is not much altered. By inter- connecting the slot with the ailerons, a greater increase of rolling momentis obtained, and the sign of the yawing moment can be reversed at and over the stall, as in previous slot and aileron control systems. The automaticcharacter of the slot is unaltered when the ailerons are neutral ; and the additional force on the control column can be kept small. Full-scale tests of this slot are proceeding. THE DISTRIBUTION OF PRESSURE OVER THE HULL AND FINS OF A MODEL OF THE RIGID AIRSHIP R.101, AND A DETERMINATION OF THE HINGE MOMENTS ON THE CONTROL SURFACES. By Dr. R. Jones, M.A., and A. H. Bell. R. & M. No. 1169. (Ae. 333). (37 pages and 13 diagrams). July, 1927. Price 1«. 9d. net. The work described in this report and in R. & M. 11(58 was conducted atthe request of the Koyal Airship Works, Bedford, in connection with the design of the airship K. 101.The following were the measurements made on the particular model tested :— (i) Distribution of pressure over the hull (circular section). Xo fins.(II) Distribution of presure over the flns and control surfaces (fins 2 of It. ,Y M. 1188').(iii) Binge umnenU ou the control surfaces as used in (ii) and on modified forms.(iv) The magnitude and direction of the wind speed near the hull. The pressure on hull, fins and control surfaces have been integrated andcompared with balance measurements. The comparisons are in accord with previous experience Inclining the rudders appreciably affects the pressure'"I the fixed fins well in front of the hinge. The rudders are underbalanced over the greater part of the range con-siilt-red, but there is a range of angle over which there is considerable over- "siliince. Hinge moment coefficients are less than on a type previouslyexamined even though the balancing area is less. This refers to under- ualancine.The fall of wind Bpeed is very rapid in the immediate neighbourhood of the ''•"I; the rate of the change in speed decreased towards the after cud of themodel. ^^ * Experiments on a model of the Airship R. 101. Jones and Bell. R. * M.yw may be regarded as Part 1 of the work on B.101, the present report '"•Uii: 1'art II, HKPOHT OF THE AIRWORTHINESS OF SEMI-RIUID AIRSHIPS SUBCOMMITTEE. R. & M. No. 1170. (Ae. 334.) (15 pages and I diagram.) November, 1928. Price 9d. net. I h> general considerations affecting the airworthiness of non-rigid and The method of using the water model to find the pressure loadinglonTtheactual airship is described and a method of calculating the fabric tensions at all points is outlined (see Appendix). A factor of safety of 4 is recom-mended for the breaking tension of the fabric based on a quick-break test, this factor being the ratio of such tension divided by the greatest tensionwhich it is calculated the fabric is called upon to withstand. Bagging attach- ments are required to have the same factor of 4, but for gome purposes afactor of 3 only is required. Mention is made of performance requirements according to the duty forwhich the airship is designed, of the proper use of gas valves and balloneta, of the carrying of ballast, of stability and control, of wireless equipment, ofprotection from electrical discharges and of fire prevention measures. Included at the end of the report is a bibliography of a number of reportsand published papers to which the Suit-Committee have referred or used in the preparation of their report. THE THEORETICAL RELATIONSHIPS FOE AN AEROFOIL WITH A MULTIPLY HINGED FLAP SYSTEM. By W. G. A. Perring, R.N.C., A.M.I.N.A. Presented by the Director of Scientific Research, Air Ministry. R. & M. Xo. 1171. (Ae. 335). (14 pages and 5 diagrams). April, 1928. Price 9d. net. Theoretical expressions for tiie lift and pitching moment of an aerofoilin two dimensional motion were developed in JR.. k M. 910.* This theory was extended in R. & Si. lOya.t to include the hinge moment of a flap in thecase of a rectangular aerofoil of finite span. The analysis has now been extended to an aerofoil fitted with a multiply-hinged flap system, and theoretical expressions for lift and pitching moment of the aerofoil, and the hinge moment about any hinge position have beendeduced in the case of a rectangular aerofoil of finite span. Application of the theoretical expressions to the particular case of an aerofoil fitted witha servo-operated flap is considered, and the theory compared with experi- ment. The agreement between theory and experiment is found to be verysatisfactory in the case of a flap 0 • 3 of the aerofoil chord, but ceases to be as good when the flap or servo chord becomes very small. • H. <fc SI. 910. A theory of thin aerofoils. By H. Glauert.t 11. & M. 1095. Theoretical relationships for an aerofoil with hinged flap. By H. Glauert. FULL SCALE DETERMINATION OF THE EFFECT OF HIGH TIP SPEEDS ON THE PERFORMANCE OF AN AIRSCREW. By W. G. Jennings, B.Sc. Presented by the Director of Scientific Research, Air Ministry. R. & M. No. 1173. (Ae. 337.) (10 pages and 8 diagrams.) August, 1928. Price 9d. net. This report describes a full-scale investigation which had for its objectthe determination of how far conclusions arrived at from model results as to the effect of high tip speeds on the performance of an airscrew are applic-able to full-size airscrews in free flight. The aircraft used for the experiments was a Fairey " Fox " fitted with aCurtiss 1J.12 enaine. The engine was calibrated on the test bed at two positions of the throttle and flight tests were carried out at heights of 3,000,5.000 and 15,000 feet in order to determine the tip speed effect on the torque and thrust coefficients of the airscrew.Wind tunnel tests on a model of a similar airscrew are analysed and the results compared with the full-scale tests.The comparison of the full-scale with the model results shows that there is a considerable scale effect (due to difference in size) at high tip speeds andthat the conclusions arrived at from model test* may not be applicable to full-scale airscrews in free flight. WIND TUNNEL TESTS WITH HIGH TIP SPEED AIRSCREWS. SOME EXPERIMENTS UPON AN AIRSCREW OF CONVENTIONAL BLADE SECTION, AEROFOIL R. AND M. 322, No. 3, AT HIGH SPEEDS. By G. P. Douglas, D.Sc, and W. G. A. Perring, R.N.C. Presented by the Director of Scientific Research, Air Ministry. R. & M. No. 1174. (Ae. 338.) (8 pages and 4 diagrams.) July, 1928. Price9i.net. The present experiments continue the investigation into the effect of tipspeed on airscrew perlormance, described in R. <fc II. Nos. 10S6*, 1091+. and 11241. The tests have been made to extend the results of E. & 31. 1124, onthe conventional airscrew section E. it SI. 322, No. 3, to higher Beynolds' numbers.A variable pitch airscrew having a conventional type of blade section has been tested under the same eonditious as the airscrews described in theprevious reports, but the present airscrew had a constant chord width of 2 in. It had a blade section of maximum thickness 10 per cent, of the chord,the section being similar to that tested and described in R. A'M. 1124. The thrust and torque gradings have been measured at. two pitch settings for tipspeeds up to 1-15 times the velocity of sound, and the results have been analysed to show the variation of lift and drag with speed.Tlie analysis of the tests does not produce consistent lift curves at low speeds and'this apparent failure of the airscrew theory detracts from thevalue of the experment as a test of the influence of Keynolds' number at high speed, which should rather be investigated by using tapered airscrewsof larger scale, pome full scale tests are proceeding. It seems reasonable, however, to infer from this experiment that Reynoldsnumber is an important factor, and that the transition from " low speed ". to " high speed " types of flow is delayed by increasing the scale. • R. & M. 1086.—Wind tunnel tests with high speed airscrews. Thecharacteristics of the aerofoil section B.A.F.3U at high speeds.—G. P. Douglas and W. fi. A. Perring.t R. & SI. 1091.—Wind tunnel tests with high tip speed airscrews. The characteristics of a bi-convex aerofoil at high speeds. Dougla . and J E. & St. 1124.—Wind tunnel tests with high tip speed airscrews. Thecharacteristics of a conventional airscrew section, aerofoil R. & M. 322, No. 3, at high speeds.—Douglas and Perring. 338k
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