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Aviation History
1928
1928 - 0322.PDF
Sx7PK,EMEJTr TO FLIGHT 36 APRIL 26, 1828 THE AIRCRAFT ENGINEER product of the mean ordinate and the base length (i.e., the mean sectional area and the length of the body) and there- fore equals the volume. For the body shown in the diagram, this total area is 39 sq. in.; therefore, as the scale of the drawing is 3 in. to 1 foot, the scale of the ordinates of the area is -fa full size and that of the base \ full size so that the total volume will be:— 39 X 16 X 4 cub. in. = 1-44 cub. ft. It also follows that the centroid of the area on the datum is vertically above the C.G. of the body (the solid body— not the shell). TECHNICAL LITERATURE. SUMMARIES OF AERONAUTICAL RESEARCH COMMITTEE REPORTS. EXPERIMENTS ON A MODEL OF A FOKKER (F. VII) MONO- PLANE WING. By A. S. Batson, B.Sc, D. H. Williams, B.Sc. and A. S. HaUiday, B.Sc. R. & M. No. 1059 (Ae. 241). (21 pages and 19 diagrams.) September, 1926. Price Is. 3d. net. Both the Fokker (F VII) monoplane and the Avro (504K) biplane havebeen reported to have a remarkable degree of control at and beyond the stall, but, whereas the Avro was fitted with a special device in the form of8lot-and-aileron control.* the Fokker was fitted with ailerons of the con- ventional type, although considerably smaller than those normally fitted toBritish machines. These experiments were made to investigate the reason for the reportedgood controllability of the Fokker (F.VII) when stalled. Rolling and yawing moments due to rolling were measured over a range ofincidence on a 0 -0444 scale model. Also rolling and yawing moments due to aileron movement, ranging from — 20° to -+- 20° by 5* steps, were measuredon the stationary model. The wind speed adopted was from 40 to 60 ft.-sec. An appreciable speed effect was found which made It difficult to predictfull-scale results from those deduced from model experiments. These tests, however, indicated that, with reference to the rolling experiments at smallrates of roll, pre-stall conditions would be maintained on the Fokker in the neighbourhood of the stall. Both rolling and yawing moments due toailerons set at ± 20° were approximately half those for the Bristol Fighter (B.F.2b). * See H. & Jt. 968. Full-scale tests on a new slot-ana-alleron lateralcontrol.—By H. L. Stevens. THE CHARACTERISTICS OF CERTAIN AEROFOIL SECTIONS FOR INFINITE ASPECT RATIO. By A. S. Hartshorn, B.Sc. Presented by the Director of Scientific Research. R. & M, No. 1072 (Ae. 254). (9 pages and 12 diagrams.) November, 1926. Price 9rf. net. For some purposes the characteristics of an aerofoil section for infiniteaspect ratio are required. This information is given in graphical form for LV = 40 for the following sections tested at the R.A.E.:—R.A.F. 15, 2a,26, 27, 28, 30, 31, 32, 33, 34 and M.2. The curves shown are :— (1) Profile drag against lift.(2) Incidence against lift, the chord line chosen for reference passing through the centres of curvature at the leading and trailing edges.(3) Pitching moment about a point on the chord as defined above and 0 25 c. back from the leading edge. THE FLEXURE OF THIN CYLINDRICAL SHELLS AND OTHER "THIN" SECTIONS. By L. G. Brazier, B.Sc., A.C.G.I., late of the Royal Aircraft Establishemnt. R. & M. No. 1081 (M. 49). 22 pages and 11 diagrams). May, 1926. Price Is. net. It is well known that thin tubes and metal aeroplane spars do not failunder bending by elastic rupture, but by instability. The present paper is an investigation of the problem of a class where some dimension* of thecross section are small compared with others, and the correction required to St. Venant's theory of flexure for this case is determined. The body is supposed strained in the manner described by St. Venant,Is then allowed to undergo a system of displacements, and the position of the system determined by the conditions that the final potential energy is a mini-mum. The results obtained should promote the formulation of the theory of rational design of thin tubes as beams and metal aeroplane spars. Thereis some uncertainty about the theoretical constants which may well be modified by later experimental results. Appended are the results for 11 types of spar calculated for fixed endsand giving the bending stresses in the web, the end load on each web. and the Euler failing load. THE FLOW OF AIR AND OF AN INVISCID FLUID AROUND AN ELLIPTIC CYLINDER AND AN AEROFOIL OF INFINITE SPAN, ESPECIALLY IN THE REGION OF THE FORWARD STAGNATION POINT. By A. Fage, A.R.C.Sc. R. & M. No. 1097 (Ae. 276). (20 pages and 8 diagrams.) July, 1926. Price la. net. A study of some of the characteristics of two-dimensional flow aroundan aerofoil mounted in a wind tunnel is described in R. * M.989.* This work included measurements of velocity in the neighbourhood of the aerofoil,and the flow pattern in the wind tunnel was also compared with that tor an inviscid flow having an equal circulation. In the present investigation experiments were first made with an ellipticcylinder of large eccentricity, this model being selected because the position of the stagnation point for an inviscid flow could be determined mathematicallyand the shape approximated to that of an aerofoil; in general, the position of the stagnation point does not agree in the two cases. Wind tunnel experiments on an aerofoil of 6-inch chord extending acrossthe tuunel show that as the angle of incidence increases the stagnation point travels around the nose towards the upper surface, and at the critical anglethere is an abrupt traverse of the stagnation point in the opposite direction ; other experiments were made on a similar model in the electrical tank.f Theresults, in general, for the same circulation gave different stagnation points in the two types of experiments, but the general results obtained for theflow from the wind tunnel experiments agree well with the theoretical flow. This difference is attributed to the method of measurement of velocity dis-tribution in the electrical tank, which is not sufficiently accurate for the present purpose. * R. & M. 989. An investigation of the flow of air around an aerofoilof infinite span. By L. W. Bryant and D. H. Williams. t R. & M. 1065. Preliminary experiments on two-dimensional flow roundbodies moving through a stationary fluid. By B. M. Jones, W. S. Farren and C. E. W. Lockyer. THE UNDERCOOLING OF SOME ALUMINIUM ALLOYS. By Marie L. V. Gayler, D.Sc. Work performed for the Engineer- ing Research Board of the Department of Scientific and Industrial Research. R. & M. No. 1102 (M. 50). (50 diagrams and 24 pages.) May, 1927. Price Is. Qd. net. In some preliminary experiments an aluminium silicon alloy was pouredinto iced water, and it was found that complete " modification " could be effected in that way. This result led to a study of the effect ofirapid chillingon aluminium-silicon alloys free from sodium, with a view to throwing more light on the process of modification. The investigation was then extendedto alloys of aluminium with copper. From the data obtained diagrams were made, which, together with microscopical evidence, threw some light onthe undercooling of alloys ; a subject which is of practical importance and of which little is known. The following aluminium alloys were studied with repsect to a definiterate of cooling, and diagrams have been drawn from the data obtained :— (1) 0 20 per cent, silicon ; normal and " modified " alloys.(2) 10 per cent, silicon with 0-2, 0-4, 0-6 and 0-8 per cent. iron. (3) 0-38 per cent, copper.(4) 7 per cent, copper wth 0 -2, 0 -6 and 0 8 per cent. iron. With regard to the undercooling of silicon-aluminium alloys it has beenshown that— (1) The supersolubility curves for "normal" alloys agree substantiallywith the accepted " modified " diagram. (2) It is not possible to obtain supersolubility curves for " modified "alloys. (3) The addition of sodium causes (a) crystallisation to take place attemperatures of spontaneous crystallisation, i.e., at temperatures in the supersolubility curves probably by suppressing the crystallisation occurringon the solubility curves, (ft) consequently it is probable that there is an increase in the number of nuclei formed. In connection with the phenomena of undercooling the macro and micro-structural changes in a 7 per cent, copper aluminium alloy and a 10 per cent, silicon alluminium alloy due to variations in the conditions of casting havebeen observed. THE THEORETICAL PRESSURE DISTRIBUTION AROUND JOUKOWSKI AEROFOILS. By W. G. A. Perring, R.N.C., A.M.I.N.A. Presented by the Director of Scientific Research, Air Ministry. R. & M. No. 1106 (Ae. 283). (13 pages and 12 diagrams.) May, 1927. Price 9d. net. The present calculations have been made to determine the influence of thethickness and centre-line camber upon the pressure distribution around an aerofoil. The calculations have been made for Joukowski aerofoils, thepressure distribution being determined for each aerofoil at three values of the lift coefficient. Three aerofoil thicknesses have been considered (0-05,0 10, and 0 15 of the chord), and calculations for each thickness have been made at three values of the centre-line camber (zero. 0-026 and 0'053). The report concludes with the following comments :—(1) That the rapid increase of pressure behind the negative-peak pressure on some of these aerofoils will cause the flow to break down, and should beavoided as far as possible. (2) That at high velocities the effect of compressibility will modify theflow locally in the regions of high negative pressure, and an aerofoil in which these high negative pressures occur will be less efficient than one in which thepressure distribution is more uniform. \ generalised type of the Joukowski aerofoil has been discussed by Mr. Glauert in R. k M. 911. 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. METAL CONSTRUCTION DEVELOPMENT. We very much regret that, owing to the length of Mr. Evans' article on " Aerodynamic Interference" and consequent lack of space, it has been necessary to hold over this month Mr. Pollard's article on " Metal Construction Development." A long instalment will, however, be pub- lished in the May issue.—ED. 286A
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