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Aviation History
1927
1927 - 0566.PDF
SUPPLBMBKT TO PLIGHT JULY 28, 1927 THE AIRCRAFT ENGINEER extremely easy and simple to operate, and it must be remem- bered that, so far as high lift and low landing speed are concerned, these devices are always in competition with the alternative method of achieving the samv object, namely, increasing the wing-chord. There is another rather important point which arises when an attempt is made to decrease landing speeds below that given by a normally proportioned ordinary aeroplane. This is the fact that the lift/drag ratio is not only relatively bad, but is rapidly getting worse with increasing incidence, and the necessary change of flight-path just before landing is difficult to achieve. This is fundamental and applies to any high lift device. If this process is carried far, some form of " crash" undercarriage becomes necessary and adds a further something to weight, resistance and cost. The best way of meeting all the requirements is, of course, not to be ascertained without much work and thought, but the situation may be summed up perhaps by saying that the speed range asked for (when taken with the other requirements) is the outstanding difficulty, always provided that it is not obtained by the sacrifice of some other desirable property. The production of an aeroplane which is much easier to fly and allows perhaps time and space for errors of judgment to be corrected would have the effect of greatly enlarging the circle of users. Increased safety and confidence would then result from mass-experience obtained, this being an indirect and long-range effect of making it easier to fly. The young man on the motor-bicycle is running no more risk than the old gentleman who has recently bought a car : statistics might indeed show that the motor-cycle is safer, for although it calls for much more skill than the car, it does, in general, get more, and a tolerable all-round degree of safety is thus attained in the use of the road. This state does not seem to be reached until the general public come in as users. This seems to be the way the promoters of the Guggenheim Competition are looking at aviation, and every one must be impressed by the public spirit and generosity they have shown in arranging it. TECHNICAL LITERATURE. SUMMARIES OF AERONAUTICAL RESEARCH COMMITTEE REPORTS. WIND TUNNEL TEST OF AEROFOIL M.2. By H. Davies, B.A., A.F.R.Ae.S., and F. B. Bradfield, Math, and Nat. Sci. Trip. Presented by the Director of Scientific Research. R. & M. No. 1070 (Ae. 252) (3 pages and 2 diagrams). October, 1926. Price 4d. net. A number of wing sections have been tested in the American Variable Density Wind Tunnel, and it is desired to get some comparative tests between the model and full-scale work in this country and the experiments in that tunnel. Certain models have been sent to America which have already been tested. The present experiments relate to an M.2 symmetrical thin wing section already tested in the National Advisory Committee for Aeronautics Wind Tunnel. Lift and drag have been measured on an 8 in. by 48 in. monoplane at speeds of 60, 80 and 90 ft. per sec. and the centre of pressure determined at 60 and 80 ft. per sec. The main characteristics at LV = 40 are EL max. 0-36 ki> min. 0-0048 at no lift 0 (L/D) max. 16-4 The aerofoil is to be tested full-scale on a Bristol Fighter and comparative tunnel tests will be made on a model of the aeroplane. WIND TUNNEL TESTS OF AEROFOIL R.A.F. 34. By H. Davies, B.A., A.F.R.Ae.S. Presented by the Director of Scientific Research. R. & M. No. 1071 (Ae. 253) (3 pages and 2 diagrams). October, 1926. Price 4d. net. R.A.F. 34 is derived from the symmetrical wing R.A.F. 30 by using a re flexed centre line of 0-02 camber. The wind tunnel tests on the sections R.A.F.30 to R.A.F.33 are described in R, & M. Nos. 928* and 946.1 Lift and drag have been measured at speeds of 60, 80, and 90 ft. per second, and the centre of pressure determined at 60 and 80 ft. per second on an 8-in. by 48-in. monoplane. The main characteristics at LV = 40 are :— i, max. 0-505 kD min. 0-0059 kj[ at no lift. -0-005 (L/D) max. 19-4 The centre of pressure varies very slightly from the position 0 -25 C. over the greater part of the normal flying range. This aerofoil is to be tested full-scale on a Bristol Fighter, and comparative tunnel tests will be made on a model of the aeroplane. • R. & 31. 928. Test of four thick aerofoils R.A.F. 30, 31, 32 and 33.-By F. B. Bradiield and A. S. Hartshorn, R.A.E. f R. * M S46. The theory of the design of aerofoils, with an analysis ofthe experimental results for the aerofoils R.A.F. 25, 26, 30 to 33.— H. Glaucrt, R.A.E. PRELIMINARY EXPERIMENTS ON TWO DIMENSIONAL FLOW ROUND R0DIES MOVING THROUGH A STATIONARY FLUID. By PROFESSOR B. MELVILL JONES, M.A., A.F.C., W. S. FARREU, M.B.E., and FLIGHT-LIEUT. C. E. W. LOCKYER, R.A.F. R. & M. No. 1065 (Ae. 247). (12 pages and 22 diagrams.) November, 1926. Price Is. 6d. A considerable study of flow past bodies in a small water channel has been carried out at the National Physical Laboratory and described in R. & M. Nos. 58*, 76| and 332.+ In these cases the models were supported at a fixed point past which a stream of water flowed. The main objection to this method is that the water channel becomes turbulent when the Reynolds number exceeds a certain value. Experiments have been made elsewhere with a model moving through still water having a free surface.§ The present tank at Cambridge University was constructed for carrying out work of a similar nature. Preliminary experi- ments have been made at a Reynolds number of 10' which it is hoped will be extended to numbers as high as 5 X 105. This is comparable with the wind tunnel range for wings, but the full-scale is greater and of the order of 107. A number of photographs illustrate the preliminary experi- ments on cylinders and aerofoils, the exposures being sufficiently short for tracks at some little distance from the model to be treated as vectors. They represent the motion of a sphere and an aerofoil starting from rest. The motion was made visible by the use of oil drops suspended in the water before the model was moved. Further experi- ments are to be conducted at higher speeds to find the type of motion resulting from the commencement of movement of an aerofoil at various angles of incidence, and for other purposes. Diagrams illustrate the method of lighting and the type of seal used to prevent water leaking past the movable attachment to which the model is fixed. • Investigation by visual and photographic methods of the flow pwtplates and models.—Eden. (K. & M. 58.) t Photographic investigation of the flow round a model aerofoil— I"'"-(R. & M. 76.) J Vortex motion.— Nayler and Frazer. (R. & M. 332.)§ Ahlborn, Naturwissenscliaitliches Verein Hamburg, Vol. XVII, 19"— (See also Science Abstracts, 1902, Xo. 430.) 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. 518/
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