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Aviation History
1934
1934 - 1482.PDF
SUPPLEMENT TOFLIGHT 96 THE AIRCRAFT ENGINEER DECEMBER 27, 1934 1592. (8 pages and 10 diagrams.) February 9, 1934. Price is.No.net. The mathematical expressions for the form of a heavy cable in a wind have beenknown for many years, but not systematic numerical results are available. Calcula- tions have been made to derive a family of curves, depending on the weight-dragratio of the cable, which should suffice to cover all practical problems, involving the towing of a heavy body. The use of the curves is illustrated by a typical numericalexample. THE EFFECT OF WIND ON THE TAKE-OFF OF SEAPLANES. By E. T.Jones, M.Eng. Communicated by the Director of Scientific Kesearch, Air Ministry. R. & M. No. 1593. (14 pages and 16 dia-grams. January 12, 1934. Price is. net. Take-off times have been observed on four seaplanes in winds varying from zeroto 25 m.p.h. and correction formulae have been deduced from the results. Some results were also obtained from take-offs made down wind. The validity of appli-cation of the formula to all seaplanes has been examined and theoretical support to the formula is given. The effect of wind on the maximum weight at which aseaplane can take-off is also examined. The take-off time and distance in zero wind for all seaplanes can be fairly accuratelygiven by formulae quoted in the paper. The maximum weight at which a modern seaplane fitted with a fixed pitch airscrew can rise from the water is almost inde-pendent of the direct effect of wind speed up to the highest wind in which the fully loaded seaplane is capable of being handled on the water.Gusts and the effect of wind in rippling the surfare of the water have not been included in the calculations. The results of practical tests show that there areoccasions when a flying boat is unable to rise from a glassy sea but can take-off in a light wind from a lightJy disturbed sea. LANDING AND TAKE-OFF SPEEDS OF AEROPLANES. By R. S. Capon. Communicated by the Director of Scientific Research, Air Ministry. R. & M. No. 1594. (7 pages and 3 diagrams.) January 19, 1934. Price 6d. net. In landing, the pilot usually stalls the aeroplane when the wheels are at a smal'distance from the ground. Since the aeroplane is decelerating it follows that in a stalled landing the speed at the moment of contact will usually be less than thestalling speed. The effect on the landing speed is considered in relation to the height at whichthe aeroplane is stalled : it is shown that in a typical aeroplane the landing speed will be 6.5 per cent, less than the stalling speed if the wheels are 6in. from the groundat the stall. The possibility of taking off at speeds below the stalling speed is considered. Inthe type of take-oft where a sudden increase of incidence is made at theendof the run (tail up take-off), a proportion of tbr weight of the aeroplane is borne by the under-carriage, and in certain types of undercarriage there may be available stored energy to project the aeroplane upwards when the incidence is increased. It is shownthat if the whole weight of the aeroplane is borne by the undercarriage just prior to the pull off, the take-off speed may be 13.5 per cent, below the stalling speed(eugine-on), or in the more practical case when half the weight of the aeroplane is airlx>rne prior to the pull-off, 8.5 per cent. 3n many undercarriages, however,there is little available stored energy. ACCURACY OF PERFORMANCE MEASUREMENT. By J. L. Hutchinson,B.A., and E. Finn, B.Sc. Communicated by the Director of 'Scien- tific Kesearch, Air Ministry. R. & M. No. 1601. (5 pages and 4diagrams.) February 7, 1934. Price 6d. net. A number of flights were made on two aircraft to determine the consistency ofrepetition tests. The consistency of measurement of rate of climb was determined from the rangeof possible mean curves cf rate of climb against height which could be deduced according to present practice in routine performance reduction from five climbs ofFox aircraft. This variation amounted to 40 ft./mill, at sea level and 90 ft./min. at 15,000 ft. The consistency of measurement of level speed was determined from five testsof Hart aircraft. The variation between the mean curves was less than 1J m.p.h. at all heights. The accuracy of speed measurement depends, however, on thestability and controllability of the aircraft, which characteristics in the cas© of the Hart are very favourable for accurate flying. The above-mentioned accuracy oflevel speed measurement could not, therefore, be expected with all types. From a general discussion of the separate sources of error in performance measure-ment the conclusion is drawn that the actual performance in the test flight is measured accurately and that the largest errors arise in allowing for variations from idealcondit.ins. (>f these variations, vertical currents introduce the most serious errors and it ts 00 this account that a number of tests are necessary. WIND TUNNEL TESTS ON A BRISTOL FIGHTER MODEL WITH SLOTTED R.A.F.34 SECTION WINGS. By K. W. Clark, B.Sc., D.I.C. Com-municated by the Director of Scientific Research, Air Ministry. K. & M. No. 1609. (5 pages and 4 diagrams.) April 14, 1934. Price6d. net. Lift coefficient and normal slat forces have been measured in the wind tunnelon a mod«l Bristol Fighter F.2B biplane with slotted R.A.F.34 section wings, for comparison with full scale experiments recorded in Kefs. 1 and 2. The model was1/10 scale, and was represented in full detail except for the airscrew and bracing wires. The wings were square tipped and the slats extended over the whole spanexcept for the centre section of the lower plane. The slot chord was 14.5 per cent. of the wing chord.The maximum lift coefficient of the aeroplane was 0.77 at 27J degrees incidence compared to 0.84 at 30 degrees full scale. The normal force coefficients on themodel reached maxima of 1.81 at 25 degrees incidence for the mid semi-span position, and 1.91 at 30 degrees for the tip position. The coefficients measured full scalewere still increasing with incidence at the great incidence tested, with values c' 2.35 at 27 degrees incidence for the mid semi-span position and 1.8 at 30 Jegreesincidence for the tip position. THE E.M.F. BETWEEN METALS IN SEAWATER. By J. W. Willstrop,B.Sc., A.I.C. Communicated by the Director of Scientific Research, Air Ministry. R. & M. No. 1611. (10 pages and 1 diagram.) June,1934. Price 9d. net. If two dissimilar metals immersed in sea-water are connected either by actualcontact with each other or by a third conducting material, there will be a flow of current from one metal to the other and this will be accompanied by solution orcorrosion of the negative metal. This corrosion is not to be confused with any cor- rosion the metals might suffer independently as a result of sea-water attack. Thetendency for this electrolytic corrosion to occur is dependent on the E.M.F. or potential difference between the metals when immersed in sea-water. Potentials were measured between various metals and a calomel electrode takenas standard. Actual potential differences between any pair of metals were then obtainable by difference. Most determinations were made at 25CC, but a shortseries was carried out at 40°C. Of the metals tested, stainless steel of the 18:8 type and monel metal were themost positive followed in order by brasses and bronzes, " Twoscore " type stainless steels, 13 per cent, chromium stainless steels, duralumin and copper-containingaluminium alloys, ordinary steels, aluminium alloys free from copper, cadmium zinc and finally the magnesium alloy D.T.D.88 which was the most negative of themetals tested. The use of metals of widely different potentials in contaci is liable to result in serious corrosion of the more negative metal especially where salinewater is likely to be encountered. WIND TUNNEL TESTS ON A MODEL GLOSTER TROOP CARRIER. WITH AND WITHOUT SLIPSTREAM. By W. G. A. Perring, R.N.C., and C. Callen. Communicated by the Director of Scientific Research, Air Ministry. R. & M. No. 1618. (15 pages and 11 diagrams.) October, 1930. Price is. net. The tests have been carried out to supply data for design purposes.Without slipstream the maximum lift measured was 0.520 without tailplane and would be 0.524 with tailplane set to trim. The slipstream increased the maximumlift by 0.10 with the tailplane in position. The maximum lift occurred at a model incidence of about 18°, and over the range of speed, 40 to 80 feet per sec. it showedpractically no scale effect. The minimum drag occurred at about 0° incidence, when the drag coefficientwas 0.01i)l without tailplane and 0.0223 with tailplanc at a wind speed of 00 f.p.s. Tested at a wind incidence of 0.6° the drag with tailplane decreased from 0.02419measured at 40ft. per sec. to 0.02175 measured at 80ft. per sec. The slipstream increased the effectiveness of the elevator control surfaces, andat a wing incidence of 8.8°, corresponding to a kj, of 0.3 the moment produced by an angular movement of the elevator was, under full thrust conditions, 35 percent,greater than the moment produced for the same angular movement of the elevator without slipstream.The tests without slipstream show that an angular movement of about 12° was sufficient to produce a rudder power of 10 at 10° above the stalling incidence. Theslipstream increased by nearly 100 per cent, the moment produced by the rudder, but had practically no effect on the yawing moment due to yaw for zero rudder angle. COLLECTED REPORTS ON BRITISH HIGH SPEED AIRCRAFT FOR THE 1931 SCHNEIDER TROPHY CONTEST. With an introduction by H. M.Garner, M.A. R. & M. No. 1575. (96 pages and 80 diagrams.) January, 1934. Price 10s. net. This monograph describes the development of the British aircraft for the Schneider-Trophy Contest of 1931, the preparations for the Contest, the actual Contest, and the successful attempts on the speed record after the Contest. The monographis mainly concerned with the technical aspects, although a tribute is paid to the great skill of the, pilots, without which the successes could not have been achieved.The monograph is divided into sections, each written by the person or persons mainly responsible for the work described, and although the monograph forms aconnected whole, the individual reports may be read without reference to the rest of the monograph.Section 1 is an introduction by H. M. Garner, giving a brief description of the history of the 1931 Contest and a summary of the contents of the monograph. In SectionII the development of the design and construction of the S.6A and S.6B are described by R. J. Mitchell, the chief designer of Supermarine Aviation Co., (Vickers) Limited.Although the design was based on the S.fi, the Schneider Trophy winner of I!t29, there was a large number of problems which required prompt solution, and thesewere very ably dealt with by Mr. Mitchell in co-operation with the Air Ministry and National Physical Laboratory staffs. One particularly difficult problem wasthe provision of adequate water and oil cooling for the engine. Section III describes the development of the engine by Messrs. Rolls-Royce Ltd.The problem was to extract more power from the engine used in 1929, and although the external shape of the engine was hardly altered, almost the whole of the workingparts of the engine had to be redesigned. The airscrews were all of the Fairey-Keed type, designed and constructed by the Fairey Aviation Co., and a brief descriptionof the development of the airscrews with an account of the methods of construction is given in Section IV.Section V describes the wind tunnel tests, is written by W. L. Cowley, A. McMillan, W. S. Walker and Sylvia W. Skan. It was desirable that models as large as possibleshould be used, so as to make the scale effect as small as possible. The tests were therefore made on as large models as possible in the Duplex Wind Tunnel at theN.P.L. (size 14 ft. X 7 ft.), the largest wind tunnel constructed at that time in this country. For the first time in the history of these Contests a large amount of full scaledata was collected. This is described by R. K. Cushing, who was the Technical Officer for the High Speed Flight, in Sections 6 and 7 and also in a separate Report(R. & M. 1472). Section IS discusses the best method of turning, and shows that the best turns are made with a relatively small acceleration. Spectacular turns areof no value. Section 7 is a collection of airscrew performance data. Considering the difficulties of the tests, the standard of accuracy reached was very high, airscrewefficiencies being obtained with a probable error of less than ± 3 per cent. The highest efficiency obtained was 88 per cent., a high value when the high tip speedsare borne in mind. R. & M. 1472 describes the determination of the position errors of the high speed aircraft, a very important piece of work based on the automatictiming apparatus developed by the R.A.E. in 1929. The absolute accuracy of the speed measurements depends finally on this apparatus. Wing Commander Orlebar summarises the flying experiences of the High SpeedFlight in Section 8. The greatest difficulties were encountered in taking off and land- ing. The take-offs of the S.6A and S.6B fitted with certain airscrews were particularlydifficult, because of the large turning tendency. The medical aspect of high speed flying is discussed in Section 9, by Wing Com-mander G. S. Marshall. The opinion is advanced that the ordinary Royal Air Force medical examination needs little alteration when applied to high speed pilots.The monograph concludes with Section 10, giving a short descriptive account of the Schneider Trophy Contest and the two speed-record flights. It is evident thatthe speed in the Contest could have been improved had not Flight Lieutenant Booth- man been instructed to take no risks on the turns and to keep the water temperatureof the engine at a safe level by throttling. The speed record of 4071 m.p.h., made on the second attempt by Flight Lieutenant Stainforth was a very good achievement,only made possible by superb piloting. The monograph illustrates the many aspects of aeronautical research which haveto be considered in the development of racing aircraft. Close co-operation between the different specialists was necessary in order to achieve success, and the monographshows how close this co-operation was in many of the problems. The large expenditure of time and money, made possible by the generosity ofLady Houston, resulted in the retention of the Schneider Trophy by Great Britain and in a new speed record. The effort was therefore well worth while in its hmnediateresults. The effect of such work in a broader sense, as a stimulant to aeronautical development in general, is almost incalculable.
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