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Aviation History
1928
1928 - 0446.PDF
42 SCTPFLXUSKT TO FLIGHT THE AIRCRAFT ENGINEER MAT 31, 1928 R. W. Penning, M B.E., B.Sc., D.I.C.). This general question of dissociationhas been dealt with in a paper communicated to the Royal Society by Mr. H. T. Tizard (Proc. Roy. Soc, A., Vol. 115, 1927, page 318), who used the collectionof experimental data here given. WIND TUNNEL AND DROPPING TESTS OF AUTOGYRO MODELS. By L. E. Caygill, B.Sc., A.M.I.M.E., and A. E. Woodward Nutt, B.A. Presented by the Director of Scientific Research, Air Ministry. R. & M. No. 1116 (Ae. 289). (5 pages and 4 diagrams.) November, 1926. Price 6cf. net. Wind tunnel and dropping tests under free flight conditions were carriedout with models of autogyros to obtain further information, particularly as to their behaviour during vertical descent.Two model autogyros, one of 2-2 ft. span of R.A.F. 30 section and the other of 10 ft. span of Gottingen 429 section, were constructed and droppedfrom a height of 90 ft., records of rate of descent and speed of rotation of the vanes being taken. The lift and drag of the 2 -2 ft. model were also measuredin the wind tunnels. The values of normal force coefficient per unit disc area in vertical descentfound in these tests for the two models were :— 2 • 2 f t. model in 7 ft. tunnel, 0 • 67 to 0 • 71.2 • 2 ft. model in free descent, about 0-6. 10-0 ft. model in free descent, 0 • 58 to 0 • 71. No evidence has been found of the very high value indicated by the fullscale demonstration flights. No further dropping tests are proposed. Wind tunnel tests are being madeby the National Physical Laboratory and further full-scale tests will be made by the Royal Aircraft Establishment. SCALE EFFECT ON THREE AEROFOILS AT LOW VALUES OF LV, R.A.F. 32, GOTTINGEN 433, and GOTTINGEN 410 WITH 2 PER CENT. CENTRE LINE CAMBER. By F. B. Bradfield, Math, and Nat. Sci. Triposes. Presented by the Director of Scientific Research, Air Ministry. R. &. M. No. 1117 (Ae. 290). (6 pages and 4 diagrams.) August, 1927. Price 6rf. net. Lift and drag have been measured at low values of LV on three aerofoilsections in connection with their use as pilot planes in model experiments. Lift and drag were measured down to LV = 2i.Minimum drag at LV = 21 is about 0 025 for R.A.F. 32 section or for Gottingen 410 (cambered), and about 0-04 for Gottingen 433. As the scaledecreases the no lift angle occurs at a more and imore positive incidence, the slope of the lift curve remaining roughly constant. In the case of Gottin-gen 433 and GQttingen 410 (cambered), the ordinary stall has disappeared from the lift curves at the lowest LV's tested, the lift increasing graduallyover a 40° incidence range. 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. AMERICAN NATIONAL ADVISORY COMMITTEE REPORTS. The National Advisory Committee for Aeronautics in the United States of America corresponds to our own Aero- nautical Research Committee. Two distinct classes of reports are issued, the first being known as Technical Reports. These Technical Reports are printed, and are illustrated by photo- graphs and /or drawings. The second class are known as Technical Notes, and are issued in mimeographed form so as to enable them to be rapidly distributed to a somewhat smaller, but directly interested, circle of readers. Copies of the Reports and Notes may be obtained from the Superin- tendent of Documents, Government Printing Office, Wash- ington, D.C., U.S.A. T.R. No. 257. " PRESSURE DISTRIBUTION OVER A WING AND TAIL RIB OF A VE-7 AND OF A TS AIRPLANE IN FLIGHT." By J. W. Crowley, Jun., N.A.C.A. This investigation was made at the Langley Memorial Aeronautical Labora-tory, to determine the pressure distribution over a rib of the wing and over a rib of the horizontal tail surface of an aeroplane in flight, and to obtaininformation as to the time correlation of the loads occurring on these ribs. Two aeroplanes, VE-7 and TS, were selected in order to obtain the informationfor a thin and a thick wing section. In each case the pressure distribution was recorded for the full range of angle of attack in level flight and throughoutviolent manoeuvres. Particular attention was given to the high and low angle of attack condittone. The multR Show i («) That the present rib load apecifl-cationg in use by the Army Air Corps and the Bureau of Aeronautics,Navy Department, are in fair agreement with the loads actually occurring in flight,but could be slightly improved ; (6) that there appears to be no definite sequence in which wing and tail surface ribs reach their respective maximumloads in different manoeuvres ; (c) that in accelerated flight, at air speeds less than or equal to 60 per cent, of the maximum speed, the accelerations mea-sured agree very closely with the theoretically possible maximum accelerations. In manoeuvres at higher air speeds, the observed accelerations were smallerthan those theoretically possible. T.R. No. 258. " SOME FACTORS AFFECTING THE REPRO- DUCIBILITY OF PENETRATION AND THE CUT-OFF OF OlL SPRAYS FOR FUEL-INJECTION ENGINES." By E. G. Beardsley,N.A.(*A. y This investigation was undertaken at the Langley Memorial AeronauticalLaboratory, in connection with a general research on fuel-iujectlon engines for aircraft. The purpose of the investigation was to determine the factorscontrolling the reprodueibility of spray penetration and secondary discharges after cut-off. The development of single sprays from automatic injection valves wasrecorded by means of special high-speed photographic apparatus capable of taking 25 consecutive pictures of the moving spray at a rate of 4,000 per second.The effects of two types of injection valves, injection-valve tube length, initial pressure in the injection-valve tube, speed of the injection controlmechanism, and time of spray cut-off, on the reproducibility of spray pene- tration, and on secondary discharges were investigated.It was found that neither type of injection valve materially affected spray reproducibility. The initial pressure iu the injection-valve tube controlledthe reproducibility of spray penetrations. An increase inthe initial pressure or in the length of the injection-valve tube slightly increased the spray pene-tration within the limits of this investigation. The speed of the injection- control mechanism did not affect the penetration.Analysis of the results indicates that secondary discharges were caused in this apparatus by pressure waves initiated by the rapid opening of the cut-offvalve. The secondary discharges were eliminated in this investigation by increasing the length of the injection-valve tube. T.R. No. 259. " CHARACTERISTICS OF PROPELLER SECTIONS TESTED IN THE VARIABLE DENSITY WIND TUNNEL." ByEastman N. Jacobs, N.A.C.A. Tests were carried out in the variable density wind tunnel at the LangleyMemorial Aeronautical Laboratorv on six aerofoil sections used by the Bureau of Aeronautics as propeller sections. The sections were tested at pressuresof 1 and 20 atmospheres corresponding to Reynolds Numbers of about 170,000 and 3,500,000. The results obtained, besides providing data for the designof propellers, should be of special interest because of the opportunity afforded for the study of scale effect on a family of aerofoil sections having differentthickness ratios. T.R. No. 260. " THE EFFECT OF A FLAP AND AILERONS ON THE N.A.C.A. M6 AIRFOIL SECTION." By George J.Higgins and Eastman N. Jacobs, N.A.C.A. This report contains the results obtained at the Langley Memorial Aero-nautical Laboratory, on an N.A.C.A. M 6 aerofoil, fitted with a flap and ailerons and tested in the variable-density wind tunnel at a density of 20 atmospheres.Aerofoil characteristics are given for the model up to 48 degs. angle of attack with the flap set at various angles, and also with the ailerons set at similarangles. The approximate lift distribution and the centre of pressure variation along the span are determined with the model at 18 degs. angle of attack andwith the ailerons displaced 20 degs. Approximate rolling moment and yawing moment coefficients are determined for the various aileron settings. A comparison of the calculated angles of zero lift and the calculated lift andmoment coefficients with those observed is given in the appendix. T.R. No. 261. " RESISTANCE AND COOLING POWER OF VARIOUS RADIATORS." By R. H. Smith, Construction Department, Washington Navy Yard. This report combines the wind-tunnel results of radiator tests made atthe Navy aerodynamical laboratory in Washington during the summers of 1921, 1925 and 1926. In all, 13 radiators of various types and capacitieswere given complete tests for figure of merit. Twelve of these were tested for resistance to water flow and a fourteenth radiator was tested for air resistancealone, its heat-dissipating capacity being known. All the tests were conducted in the 8 by 8 ft. tunneC or in its 4 by 8 ft. restriction, under conditions asnearly the same as possible. That is to say, as far as possible, the general arrangement and condition of the apparatus, the observation intervals, theratio of water flow per unit of cooling surface, the differential temperatures, and the air speeds were the same for all. Also, for reasons of comparison,the L/D value of 6 which was assumed in the 1921 tests as the L'D of the aeroplane using the radiator, was also used in the more recent tests. No attempt is made to enter upon the theory of heat dissipation. Onlythe actual test results are given and reduced to coefficient form. The precision of the tests as representative of full-flight performance is definitelyknown only in the case of the HN.2. The McCook Field full-flight performance and the Navy tunnel performance of this radiator agree within about3 per cent. Since thi3 full-flight test was made with unusual care, and since thewind-tunnel tests on all the radiators were made not only accurately but also at almost full scale, it would seem probable that these tests representquite accurately the full-flight performances in actual service. T.R. No. 262. " FRICTION OF AVIATION ENGINES." By S. W. Sparrow and M. A. Thome, Bureau of Standards. The first portion of this report discusses measurements of friction madein the altitude laboratory of the Bureau of Standards between 1920 and 1926 under research authorisation of the National Advisory Committee forAeronautics. These are discussed with reference to the influence of speed, barometric pressure, jacket-water temperature, and throttle opening uponthe friction of aviation engines. It is concluded that (1) Changes in friction due to chances in the temperature of the air entering the engine are negligible.(2) Changes" in friction which result from changes in atmospheric pressure are due primarily to changes in pumping loss. An approximate figure forthe engines mentioned in this report is that the friction mean effective pressure decreases about one-tenth of a pound per square inch for each decrease of1 cm. Of mercury in the barometric pressure. (3) The increase in friction resulting from a decrease In throttle opening is due to the change in pumpingloss. For the engines mentioned in this report the change in freition mean effective pressure which accompanies a change in manifold suction of 1 m.(2-54 cms.) of mercury ranges from 0-20 lb. per sq. in. obtained at an engine speed of 1,200 r.p.m. to 0-39 at 1,800 r.p.m. (4) For the range of speedscovered in this report, namely, from 1,000 to 2,200 r.p.m., the friction mean effective pressure increases with speed, but ordinarily the percentage increaseis less than the corresponding percentage increase in speed. At low engine speeds the friction mean effective pressure changes much less with changeIn speed and in some instances remains practically constant. (5) I notion 404/
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