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Aviation History
1926
1926 - 0129.PDF
FEBRUARY 25, 1926 23 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT objectives has, in a measure, been attained, but the second has not and cannot be attained except as the result of laborious and lengthy experiments, which have yet to be undertaken. The fore-and-aft control of stalled aeroplanes yet remains to be studied in detail. This it is proponed to do as soon as possible. From practical experience there is no doubt that the conventional aeroplane of the present day can be con- trolled fore-and-aft when stalled to moderate angles, but considerably more study of the problem is required before it will be practicable to experiment on the problem of landing whilst in the stalled state. These Reports can be obtained from H.M. Stationery Office, Kingsway, W.C. 2, and from Branch Offices. AMERICAN NATIONAL ADVISORY COMMITTEE REPORTS. Report No. 214, by Professor E. P. Warner, of the Massachusetts Institute of Technology, is entitled '" Wing >>par Stress Charts and Wing Truss Proportions."' In the introduction it is pointed out that, although the coming of the thick aerofoil section has somewhat decreased the number of aeroplanes designed with continuous wing spars externally supported at several points, the type has not by any means disappeared, and the calculation of continuous beams is still making heavy inroads upon the time of the designer. The curves given and described in this report hfve been prepared with the object of reducing the labour involved in such calculations. A series of charts have been calculated, giving the bending moments at all critical points, and the reac- tions at all supports for such members. Using these chfrfcs as a basis, calculations of equivalent bending moments, representing the total stresses acting in two-bay wing trusses of proportions varying over a wide range, have been deter- mined, both with and without allowance for column effect. Tins leads finally to the determination of the best propor- tions for any particular truss or the best strut locations in any particular machine. The ideal proportions are found to vary with the thickness of the wing section used, the aspect ratio and the ratio of gap to chord. Report No. 217, by Dr. Max Munk, is entitled ": Preliminary Wing Model Tests in the Variable Density Wind Tunnel of the X.A.C.A.," and contains the results of a series of tests with three wing models. By changing the section of one of the models and painting the surface of another, the number of models tested was increased to five. The tests were made in order to obtain some general information on the air forces on wing sections at a high Reynolds Number, and in par- ticular to make sure that the Reynolds Number is really the important factor, and not other things like the roughness of the surface and the sharpness of the trailing edge. The tests described seem to indicate that the air forces at a high Reynolds Number are not equivalent to respective air forces at a low Reynolds Number (as in an ordinary atmospheric wind tunnel). The drag appears smaller at a high Reynolds Number, and the maximum lift is increased in some cases. The roughness of the surface and the sharpness of the trailing edge do not materially change the results, so that it is felt that tests with systematic series of different wing sections will bring consistent results, important and highly useful for the designer. Copies of these reports can be obtained from the Superin- tendent of Documents, Government Printing Office, Washing- ton, D.C., U.S.A. VERSLAGEN EN VERHANDELINGEN VAN DEN RIJKS-STUDIEDIENST VOOR DE LUCHTVAART— Deel III. Part III of the Reports of the Aeronautical Research Institute of Amsterdam contains a good deal that is of interest to British aeronautical engineers and designers. The book is, of course, published in Dutch, but each report is preceded by a summary in French, English and German, and as the subject matter of the report is familiar and diagrams and tables are more or less a universal '" language," there should not be any great difficulty in following the genera] sense of the various reports and the results arrived at. Report A.33 deals with experiments on the pressure dis- tribution on the fuselage of an aeroplane model, tested with a thick wing resting directly on its upper surface, and also tested without the wing. The tests show the influence on the air flow over the fuselage of a thick wing so placed. Plottings are given both for the fuselage by itself (zonder draagvlak) and with the wing in position (met draagvlak). Report No. A.58 gives a nomogram for the. correction of incidence and drag of model aerofoils tested in an airstream of finite dimensions, and this nomogram is directly applicable to making the necessary corrections to model tests in the tunnel. In Report A.77 experiments carried out on the pressure drop in ar. air current, caused by the metal gauze, used to represent radiator,'-, are described, and the results given. Report A.96 describes experiments with and results obtained from a preliminary investigation of the influence of a rotating cylinder placed in the leading edge of an aerofoil. These tests have already been described in FLIGHT (January 15, 1925). Space does not permit of a detailed reference to the rest of the reports, but an indication of their nature i» provided by the titles, which are as follows :—M.14A : Experiments on the protection against humidity of wooden aeroplane parts by means of protective coatings of oil varnish. \ .79 : Photographic time studies of aeroplane paths. A.92 : Ex]>eriments on the cooling j^ower of two different radiators fortheFokkerC.IV. A.76 : Model experiments on modifica- tions of Fokker CIV biplane. The latter report contains some interesting data on wings of various section and plan form as fitted to the fuselage of the CIV. Copies of the Report can be obtained from Messrs. Gebr. Cleeff, £8; Spui, The Hague, Holland. PISTON TEMPERATURES AND HEAT FLOW IN HIGH- SPEED PETROL ENGINES. Under alove title a very interesting paper was read by Professor Gibson. D.Sc, of the University of Manchester, before the Institution of Mechanical Engineers, on January 22, 1926. The paper dealt in the main with the results of the measurements of piston temperatures made by the lecturer on the cylinders of various high-speed petrol engines during the past seven years. A number of the measurements were made at the Royal Aircraft Establishment, and the data obtained in these particular tests, along with the methods of obtaining the temperature readings, have been published in Report \\o. 13, L.A.S.C, May, 1918, of the Advisory Committee for Aeronautics. The results of the measurements and calculations outlined in the paper led to the following general conclusions :—• (1) Under normal operating conditions, at full load, the temperature at the hottest point of an aluminium alloy piston of 100 mm. diameter, working in an aluminium air-cooled cylinder of good design, varies from 210° to 250°, depending on the design of the piston and the composition of its alloy. This is with a clearance (cold) of about 0 -025 in. With such a clearance*the drop in temperature between the edge of the piston crown and the cylinder wall is from 25° C. to 30° C An increase in the piston clearance increases its temperature. (2) From a thermal point of view there is little to choos^ between most of the usual aluminium alloys. The difference in temperature between the best and the worst is only about 25° C. With the exception of the alloy containing 8 per cent. Cu and 1 per cent. Mn, all have very nearly the same con- ductivity at 200°, and these all give similar results in a piston. The Cu-Mn alloy has a lower conductivity and gives a hotter piston. It should be noted that if this alloy is annealed at 450° C. for a short time, its conductivity becomes as high as that of the other alloys and its behaviour in a cylinder would presumably be the same. 110&
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