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Aviation History
1925
1925 - 0308.PDF
•£"« MAY 21, 1925 AERONAUTICAL RESEARCH COMMITTEE REPORTS FROM the number of enquiries we receive it appears that there is a desire in aircraft circles to know 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 can hardly be expected 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, Abingdon Street, London, S.W.I ; York Street, Manchester ; 1, St. Andrew's Crescent, Cardiff ; 120, George Street, Edinburgh, and through any bookseller. Forces and Moments (including those due to Controls) on a Model Fairey " N.4 " Flying Boat " Atalanta," at Various Angles of Yaw. By H. B. Irving, B.Sc, and A. S. Batson, B.Sc. Reports and Memoranda, No. 933'. (Ae. 154.) November, 1924. A large amount of wind tunnel data has been accumulated on the stability of complete models, including the lateral stability of S.E'. 5A aeroplane (see R. and M. 831)* and the Bristol"Fighter (see R. and M. 932)f and the longitudinal .stability of the six following (see R. and M. 705) : Tarrant " Tabor," Vickers " Valentia," Boulton and Paul " Bourges " (" Dragonfly " engines), Avro " Manchester " (" Puma " engines), Short " Cromarty," Fairey " N.4." The present investigation is the first of its kind, and was undertaken to measure the lateral stability characteristics of a flying boat. A special balance was used to obtain these measurements, and it is described in R. and M. 822. Measurements were made on a one-thirtieth scale model Fairey " N.4 " flying boat, at a wind speed of 40 ft./sec, of the forces and moments over a range of incidence 4 deg. to 36 deg., and for angles of yaw up to 30 deg. The report concludes as follows :— Lateral Force.—In general, lateral force due to yaw decreases slightly as the angle of incidence is increased. Boiling and Yawing Moments.—For angles of incidence greater than about 12 deg., rolling and yawing moments, due to yaw, increase considerably with incidence. Pitching Moment.—When the model is yawed the general tendency is to produce a pitching moment tending to increase the angle of incidence, but, excepting in the region of the stall, this effect of yaw is small. Rolling Moment Due to Ailerons.—At normal flying angles of incidence the aileron control i« slightly reduced by either negative or positive yaw ; at large angles, the variation in the aileron control is considerable and irregular. For aileron angles larger than about 10 deg. there is but little increase in control. Yawing Moment Due to Aileron?.—At normal flying angles of incidence the yawing moment due to ailerons does not vary much with yaw : at large angles this yawing moment is appreciably increased when the model is yawed more than about 15 deg. Rudder Control.—The general effect of yaw on the yawing moment due to rudder is to increase it for small angles of yaw up to about 10 deg., but to reduce it appreciably for larger angles of yaw. There is no increase in the rudder control for rudder settings greater than about 15 deg. Measurement of Pitching Moments due to Roll on Wings of Avro 504K. By F. B. Brad field, Math, and Nat. Sci. Tripos. Presented by the Director of Scientific Research. Reports and Memoranda, No. 944. (Ae. 164.) November, 1924. There are a number of difficulties associated with the con- trol of aeroplanes at low speeds, and the subject is one that is being thoroughly investigated by the Air Ministry under the direction of the Aeronautical Research Committee. In connection with the full-scale work, a number of model experiments have been made to measure the various charac- teristics of aeroplanes. The present report gives the results of the measurement of pitching moments due to rolling. Two other papers, R. and M. 787 and 848, give the results of rolling and yawing moments on model wings due to rolling, and they should be studied in conjunction with the present paper. The pitching moments were measured for angles of inci- dence up to 33°, and rotational rates up to a value defined by ps/V = 0-3, and in some cases up to 0-5. The moments so measured have been calculated from pitching moments measured without rotation. The accuracy of the results is * R. and M. 831. " On the Effect of Sideslip on the Aerodynamic Forces and Moments (including those due to the Controls) for a Model S.E.5A Aeroplane."—Irving and Batson. t R. and M. 932. "Experiments on a Model of a Bristol Fighter Aeroplane (l/10th scale)." Sections I and II. X R. and M. 822. " An Attachment to Main Balances for Measuring There Forces and Three Moments."—Lavender, Fewster, and Henderson. detracted from by large corrections which had to be made to the balance reading, but measurement and calculation are in substantial agreement as to the type of curve resulting. The change of pitching moment with rate of roll is of interest as being a possible contributory cause to the difficulty experi- enced in some types of aeroplanes in coming out of a spin. At incidences above 21° the moments measured in the model experiments become more positive with increased rate of roll, and so would help to keep an aeroplane in a spin, but the effect in magnitude is small. Lift and Drag of Junker Monoplane : Comparison of Model with Full-Scale Results. By B. I). Clarke, B.Sc., L. P. Coombes, B.Sc., H. Glanert, M.A., and A. S. Hartshorn, B.Sc. Presented by the Director of Scientific Research. Reports and Memoranda, No. 945. (Ae. 165.) November, 1924. There are many available reports of comparative tests on model and full-scale biplanes, but there are no published British tests on a monoplane except those described in the present report. There is an additional interest on account of the thick wing used in the Junker construction, the present experiments forming the first of a series on thick wings. The full-scale determination of the lift and drag has been made in the usual manner by glides with a stopped airscrew, and the corresponding model experiments cover a range of speed from 25 to 90 ft. per second with a detailed model to l/12th scale. It was found that the s»ale effect on lift coefficient was not large, but its maximum value decreased steadily with increase of the scale of test. There was a very large scale effect on the minimum drag of the complete aeroplane, the full-scale value being about 20 per cent, lower than that given by the model at its highest wind speed. The amount of scale effect due to the corrugations of the wing and body surfaces has not been thoroughly investigated, but it is hoped to carry out at a later date some experiments on another thick wing to clear up a possible large-scale effect due to this cause. Experiments to Verify the Independence of the Elements of an Airscrew Blade. By C. X. H. Lock, M.A., H. Bateman, B.Sc., D.I.C., and H. C. H. Townend, B.Sc. Reports and Memoranda, No. 953. (Ae. 172.) November, 1924. A previous paper, R. and M. 786, gives an aerodynamic theory of the airscrew based upon similar lines to the aerofoil vortex theory of Prof. Prandtl and his colleagues. The two theories differ in one essential aspect in their application. According to the vortex theory of airscrews,* the forces on an element of an airscrew for a given working condition are independent of the design of the rest of the blade,f a conclusion differing from the case of an aeroioil, and the object of the present experiments was to provide a direct experimental check. The experimental check can be accom- plished by a comparison of observed thrust grading on two airscrews which are identical in shape and blade angle at one section, but differ at other sections. Thrust grading curves were determined by measurement of total head for pairs of screws, selected from the family of airscrews, and with the blades of one member of the pair rotated so that the blade angle and section at a single radius were identical with those of the other member, while differing at other radii. The thrust grading curves should then cross at this particular radius. Two screws of extreme pitch were tested, each at four different angle settings, for com- parison with a standard screw of normal pitch at two working conditions. The agreement of experiment with theory was very good except in certain cases of measurements near the tip and boss of the airscrew, which measurements affect only slightly the calculation of the airscrew's performance. • R. and M. 786. " An Aerodynamic Theory of the Airscrew."—Glauert. t Neglecting the pressure gradient in the wake due to centrifugal force, which is shown in R. and M. 786, Appendix III, to be negligible. 308
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