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Aviation History
1932
1932 - 0508.PDF
40 SUPPLEMENT TO FLIGHT MAY 27, 1932 THE AIRCRAFT ENGINEER Other results have been compared with experimental values obtained by Sir Thomas Stanton in E. & M. 1388.* Part II discusses the assymmetrical flow and it is found, as Professor Xaylort pointed out, that this type of flow is unique. The critical values obtained are very close to those observed experimentally. * R. & M. 1888. The Variation of Velocity in the neighbourhood of the throat of a Constriction in a Wind Channel.—Stanton. t B. <fc M. 1381. The flow of air at high speeds past curved surfaces.— Taylor. AGE-HARDENING OF ALUMINIUM ALLOYS. By Marie L. V. Gayler, D.Sc, and G. D. Preston, B.A. R. & M. No. 1431. (19 pages and 12 figures.) May, 1931. Price Is. 3d. net. (1) An investigation into the age-hardening of a series of alloys made with high-purity aluminium containing 4 per cent, copper, to which iron, silicon and magnesium have been added either independently or together, has confirmed the results of previous investigators and new data have also been obtained. (2) X-ray and microscopic examination have failed, however, to give an explanation of the phenomena observed during age-hardening at room temperature; any changes in the aluminium lattice which may accompany the hardness changes which take place in these alloys cannot be detected by the existing methods of X-ray investigation. (3) The age-hardening at 200 deg. C. of a duralumin made with very pure aluminium and containing magnesium and copper is accompanied by the precipitation of CuA^, but the age-hardening of a similar duralumin made with commercial aluminium results in the precipitation of Mg2Si as well. DIMENSIONAL STABILITY OF HEAT-TEEATED ALUMINIUM ALLOYS. By J. D. Grogan, B.A., and D. Clayton, B.Sc. R. & M. No. 1435. (18 pages and 18 figures.) December 3, 1931. Price Is. net. This investigation was carried out to examine a report that serious secular changes occur in light alloys during storage. Subsequently attention was directed to the dimensional changes which occur when heat-treated material is machined. The following conclusions have been drawn from the investigations:— (1) Ho secular changes have been detected in the heat-treated aluminium alloys examined, after the normal age-hardening process is complete. (2) Considerable dimensional changes occur when material quenched in cold water is machined. Of the alloys examined these changes were greatest in •• Y " alloy, less in duralumin and " 25S " alloy, and still less in copper-silicon alloy. (3) The central length of a heatrtreated cylinder contracts less than the peripheral length when concentric rings are machined from the middle portion of the length of the test-piece ; consequently the ends become convex. (4) When a narrow groove is cut, and subsequently widened, in the middle portion of the test-piece, complicated dimensional changes occur. The first cut produces a large change both in the central and in the peripheral length. Subsequent widening of the cut produces in the central length small changes which reverse in direction, and in the peripheral length uniform changes smaller than the first. (5) In '" Y " alloy and duralumin, the only alloys examined in this manner, quenching in cold oil reduces the dimensional changes which occur on machining as compared with cold water ; quenching in boiling water reduces them to relatively small proportions. (6) Tempering subsequent to quenching in cold water reduces somewhat these dimensional changes in " 25S " alloy, but increases them to a very small extent in the copper-silicon alloy. (7) These dimensional changes do not appear in annealed material. (8) The Brinell hardness of these alloys after quenching in cold water in the form of cylinders 5 in. long and 3 in. diameter attains a value at least equal to that attained by much smaller masses. (9) Cylinders of " Y " alloy and duralumin, 5 in. long and 3 in. diameter, are satisfactorily hardened by quenching in boiling water. SOME PRELIMINARY TESTS ON THE EFFECTS OF SIDE- SLIP ON THE ROLLING AND YAWING MOMENTS DUE TO ROLL OF A BRISTOL BIPLANE. By F. B. Bradfield, Math. and Nat. Sci. Triposes, and A. S. Hartshorn, B.Sc. Communicated by the Director of Scientific Research, Air Ministry. R. & M. No. 1439. (4 pages and 10 dia grams.) June, 1926. Price 6d. net. The object of the experiments described in this report was to determin whether the effects of roll and sideslip, such as are associated with the spinning of an aeroplane, may be measured independently and their joint effect deduced by adding the component parts. The results show that the effect of sideslip and roll are not additive after the stall. It should be noted, however, that in another published paper, R. <fe M. 1418* a calculation has been made of the combined effect of sideslip and roll using the data of the present report but taking account of the variation in incidence along the span when rolling. The appropriate sideslip term for each position along the span was taken from pressure distribution data on a yawed aerofoil.t The results show that the combined effect may be calculated with considerably better accuracy than by the simple addition of the indepen dent effects, provided the additional data required in the calculation is available. _______ * R. & M. 1418. Note on the addition of rolling moments due to roll and sideslip.—H. B. Irving. t B. & M. 1203. Pressure distribution over a yawed aerofoil.—D. H. Williams. INVESTIGATION OF ATMOSPHERIC TURBULENCE BY AIR CRAFT CARRYING ACCELEROMETER S. By W. G. Jennings, B.Sc., R. P. Alston, B.A., and C. Howarth, M.I.Ae.E., A.F.R.Ae.S. Communicated by the Director of Scien tific Research, Air Ministry. R. & M. No. 1441. (6 pages and 10 diagrams.) October, 1931. Price 6d. net. The object of the experiments described in this report was to investigate the effect of atmospheric turbulence on the normal accelerometer reading recorded when flying in weather in which disturbances, described generally as " bumps," might be expected to occur. The normal accelerations of four aircraft when flying in types of weather in which large disturbances might reasonably be expected to occur were measured in S.E. England. The maximum and minimum values of the normal accelerometer readings recorded were 2-3 g. and 0-3 g. respectively, and both occurred when flying in the neighbourhood of cumulus clouds. On the hypothesis of a simple sharp-edged gust the corresponding gust velocities are 17 ft./sec. upward and 9 ft./sec. downward. Owing to the absence of suitable weather conditions it was not possible to carry out a useful systematic investigation of the effect of speed and wing loading on the normal acceleration. There is little likelihood of meeting bumps of greater severity over S.E. England, except perhaps in types of weather not experienced this summer, e.g., in abnormally hot or abnormally squally weather. Further tests carried out in the Northern Highlands produced maximum and minimum accelerometer readings of 3•0 g. and 0 g. respectively. The corre sponding vertical gust velocities are 30 ft./sec. upward and 15 ft./sec. down ward respectively. Other experiments are to be made in winds of greater strength as these experiments were limited to 20 m.p.h. FULL-SCALE DETERMINATION OF THE MOTIONS, AT THE STALL, OF A BRISTOL FIGHTER AEROPLANE FITTED WITH AUTO-CONTROL SLOTS AND INTERCEPTORS. By A. Ormerod, B.Sc. Communicated by the Director of Scientific Research, Air Ministry. R. & M. No. 1442. (4 pages and 24 diagrams.) October, 1931. Price 4d. net. Qualitative flight trials have been made of the control at the stall of a Bristol Fighter fitted with slot-and-interceptor control. This control was found to be the most satisfactory type yet tested on a Bristol Fighter. Quan titative measurements were required for comparison with similar records obtained with other types of control. An analysis of the records shows that the aileron control is powerful and effective and appears to cause yawing moments in the beneficial direction. FLIGHT TESTS ON AN AEROPLANE WITH A CONTROL COLUMN GIVING WARNING OF DANGEROUS WING LOADS. By H. E. Wimperis, C.B.E., M.A., F.R.Ae.S., M.I.E.E. Communicated by the Director of Scientific Research, Air Ministry R. & M. No. 1446. (6 pages and 4 dia grams.) July, 1931. Price 6d. net. Since the speed capacity of modern aeroplanes continually rises, whilst the reaction time of the human body remains unchanged, it becomes necessary to consider the manoeuvre stresses likely to arise in the future on account of this increasing disproportion. The highest stress that can arise during any manoeuvre carried out without loss of height is measured by the ratio of the square of the top horizontal speed to the square of the stalling speed, being indeed given in the usual " accelerometer reading " by this very ratio; hence the load coming on to the wing of an aerobatio machine (constructed to present-day load factors) during such manoeuvres will not produce dangerous loads on the wing. It is only when height is lost, so that the speed may rise much above top horizontal speed, that mishandling of the controls by the pilot may lead to structural failure. In view, therefore, of the increase in speed of modern aircraft it became necessary to consider the possible introduction of a device to give warning to the pilot when the load on the wings grew dangerously high. A special form of control column containing an accelerometer device was made for this purpose and tried in the air. The device was tested in the laboratory at R.A.E. to determine the speed of conveyance of the signal in relation to the reaction time of the human body and subsequently in the air when fitted to a Siskin aeroplane. It was found that the signal was rapidly given and was easily noticed. FULL-SCALE LIFT AND DRAG CURVES OF A STANDARD SEAPLANE. By A. S. Crouch, D.I.C., A.CG.I. Com municated by the Director of Scientific Research, Air Ministry. R. & M. No. 1448. (4 pages and 7 diagrams.) December, 1931. Price 6d. net. R. <fc M. No. 1354* describes full-scale lift and drat' measurements made on the Blackburn " Iris II " in which n method proposed by Mr. McKinnon Wood for obtaining zero thrustt was adopted. This method has now been used in tests on a standard seaplane with a R.A.F. 15 modified wing section, and the lift and drag curves have been compared with those of the aircraft with airscrew fixed. From the two drag curves thus obtained the drag of the stopped airscrew is deduced. The drag coefficient of the fixed airscrew is practically constant up to about 10° incidence and equal to 0-004. This is equivalent to a drag of 5-5 lb./sq. ft. of projected blade area at 100 ft./second. * R. <fe M. 1354. Full-scale measurement of lift and drag of large Seaplanes —experiments on Blackburn "Iris."—Coombes and Gushing. t R. <fe M. 1447. Thrust integrating tubes. Wind tunnel experiments.— Lock, Johansen and Nixon. THE INTERFERENCE ON THE CHARACTERISTICS OF AN AEROFOIL IN A WIND TUNNEL OF CIRCULAR SECTION. By H. Glauert, F.R.S. Communicated by the Director of Scientific Research, Air Ministry. R. & M. No. 1453. (12 pages.) December, 1931. Price 9d. net. Approximate formula? for the interference on an aerofoil in a tunnel have been in general use for many years, and attemps have been made to develop more accurate formulte, but the analysis does not take account of the change of lift distribution caused by the tunnel constraint. A general method of analysis has been developed for an aerofoil in a tunnel of circular section, and has been applied to aerofoils of elliptic and rectangular plan form. It is demonstrated that the formulae derived from the assumption of elliptic distribution of lift are sufficiently accurate for all conventional shapes of aero foil, but that those derived from the assumption of a uniform distribution over-estimate the effect of increasing the span of the aerofoil. If the tunnel correction is required with an accuracy of 10 per cent, only, it is unnecessary to allow for the change of the. correction factor with the span of the aerofoil. 468 h
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