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Aviation History
1921
1921 - 0116.PDF
FEBRUARY 17, 1921 ADVISORY COMMITTEE REPORT FOR 1919-20 IN the years before the War it was customary to publishannually the reports of the Advisory Committee for Aero- nautics, and dissatisfaction was often expressed on accountof the long delay before the reports of wind tunnel tests became available. Since the armistice a different procedurehas been followed, i.e., each report has been issued as a separate booklet, thus saving valuable time. Lists of thesereports (Reports and Memoranda) have been published in FLIGHT from time to time. In consequence of the newprocedure the latest report of the Advisory Committee for Aeronautics for the year 1919-20, which ha"s just been issued" as a white paper, does .not contain the actual technical reports, but merely a broad outline of the work which isdescribed in detail in the Reports and Memoranda, etc. Incidentally this is the last report of the Advisory Committeeas at present constituted, its work in the future being dele- gated to the Aeronautical Research Committee, of whichSir Richard Glazebrook is chairman. A perusal of the report brings out little that is fiew tothose who have read the Reports and Memoranda series now published by the Stationery Office. A few items in the reportmay, however, be of interest to readers of this journal. For instance, it is not, we think, generally known that thereexists at the Royal Aircraft Establishment at Farnborough a complete installation capable of carrying out tests onaircraft engines of all sizes up to 1,200 h.p., including pro- vision for tests under high altitude conditions, with variationof air pressure and temperature, for engines up to 250 h.p. With one exception there is no indication in the report ofaltitude tests having been made of complete engines, such as has been the case, for instance, in the American altitudelaboratory, efforts at Farnborough having apparently been confined chiefly to tests on single cylinders. The exceptionis a series of tests on a Liberty engine fitted with a Rateau supercharger, which has given ground level power underconditions corresponding to an altitude of 15,000 ft. Of other work in connection with, engines, mention maybe made of development work on air-cooled cylinders. Here a very considerable amount has been done, with apparentlygood results, as the following quotation from the report indicates :— " Air-cooled Cylinders.—The development work on air-cooled cylinders has made good progress, and present-day air-cooled cylinders are capable of performing equally wellunder the same full-load conditions as the most efficient water-cooled types. The improvements, principally tocylinder cooling fins and shape of combustion chamber, have permitted the increase of the compression ratio from4-6 to 5-3, with a gain in power and reduction in fuel con- sumption . " The cylinders are of composite construction withaluminium head cast on to a steel barrel, and a series of tests has been carried out to determine the most satisfactoryshape of key joint between barrel and head to give unity and gas tightness. " Cylinders designed and made at the R.A.E. of the samebore and stroke as the Dragonfly type were mounted on a Dragonfly crankcase, and the power was increased from295 b.h.p. at 1,650 r.p.m. to 350 b.h.p. at the same speed; at the same time decreasing the consumption from 0-64 lb.to 0-54 lb. per b.h.p. hour. The added weight was about 40 lbs. Other cylinders were made to replace those of theWasp engine, keeping the bore and stroke the same, and in addition modifications were made to improve the fueldistribution. The power was in this case increased from 150 b.h.p. to 185 b.h.p. at i,8oo r.p.m., the consumptionbeing at (the same time reduced from 0-59 lb. to 0-49 lb.per b.h.p. hour. The added weight was 27 lbs. " In order to obtain the performance of large air-cooledcylinders an 8-iri. bore and 10-in. stroke cylinder has been .-•, made andjis now under test. Much trouble is being experienced. with the valve gear. An 8-in. by 11-in. water-cooled cylinder has also been made and is under test. This cylinder has beendelayed by valve gear trouble, the design of which for large ^high-speed engines requires careful consideration. " A cylinder with aluminium head secured to the barrelby bolts and nuts has been experimented with and may possibly give results almost equal to those obtained froma cast on head cylinder." In the matter of wind tunnel tests a great deal of workhas been done, not only experiments with the usual parts and models of machines, but also on the wind tunnels them-selves, and air speeds as high as 130 ft./sec. have been attained in one of the channels at the R.A.E. If it becomepossible to use such high speeds, the accurate determination of scale effects should be within measurable distance ofaccomplishment. Perhaps one of the most useful spheres of research undertaken is that on stability of aeroplanes.It has been arranged that a complete model of any new type of aeroplane shall be submitted to the N.P.L. for a thoroughinvestigation of its stability, and one of the 7 ft. wind channels has been set-aside for this work. This work will necessarilybe of a lengthy character, but it is hoped that the results will be of general interest, especially in conjunction withfull-scale tests of the machines in flight, suitable methods of - which have now been developed. It is gratifying to find that a number of tests have beenmade on high-lift wings, among others that of the Fokker machines, to which the following reference is made in thereport:— " Aeroplane Wings.—Tests on wing sections still form aportion of wind channel work. An advance in the design of aeroplane wings has lately been made possible by theintroduction of a new feature which renders possible the conversion of a high speed low-lift wing into a high-lift wing.The experiments on this invention are still of a preliminary nature, but sufficient data are available to show that thespeed range of aeroplanes in the near future will be very greatly increased. " Experiment has continued on a number of wing sectionsof the fixed camber type. The Fokker thick aerofoil section . has been tested and gave a maximum lift coefficient of0-765 compared with 0-845 for the R.A.F. 19 section, and similar values for some of the American high-lift wings,such as U.S.A.T .S. 5. Two Bristol aerofoils with characteristics similar to the section R.A.F. 15, together with modificationsof the last-named, have been tested, but they provide no new developments ; similar remarks apply to the biplanetest of R.A.F. 19, with maximum lift coefficient of 0-797. In considering these and other sections, attention may,however, be drawn to a method of comparing the relative merits of various aerofoil sections based on the principleof plotting horse power necessary against forward speed. " Of greater interest is the result of an investigation onthe performance of a wing of variable camber. The form of the section is variable by means of a narrow front flapand a fairly wide rear flap, both being moved simultaneously so that the new chord is always parallel to the original.A strut-shaped section was taken and the resulting aerofoil was'as good as R.A.F. 15. Similar experiments on a betterprimary, such as R.A.F. 15, promise a,, greatly increased performance ; these are now in hand. The form of camberedwing here tested had not the disadvantage of a large change in the position of the centre of pressure such as is usuallyassociated with the introduction of flaps on the wings." While not denying the advantages of variable camber,with both leading and trailing edges variable, we would mention that several investigators have found that thestresses set up in such a wing may be very considerable, and that this should be kept in mind when contemplatingits aerodynamic advantages. There is a delightful bit of naivete in the report dealingwith wind tunnel tests on a model of the ill-fated T arrant triplane "Tabor." "They" (the experiments), the reportstates, " show that with the machine taxi-ing at the observed attitude and speed at the time of the accident, the effectof the upper airscrews, when suddenly switched on, would be to cause the machine to turn over on its nose if the con-trols be not moved." The solemnity of the announcement of this self-evident fact is most amusing. Air-Trouble in Ireland ' - ^ '•'"'"-'AN official note from Dublin Castle states that on Feb- ruary 11 Aeroolane 187 made a forced landing at Ballinamina,near Kilnnane?" county Limerick, at 4 p.m. The pilot, whose name was Moreton, went for assistance, leaving his observer,Mackey, by the machine. During his absence a number of armed men attacked the machine, and'when the pilot returnedhe found his comrade missing and the machine in flames. It was officially stated on Monday that Mackey had beenreleased and had reported at Buttevant Barracks. Residents were warned that unless Mackey was released reprisalswould take place. On Saturday some traders in Kilfinane received notice, it is reported, that their houses were to bedestroyed. No details of Mackey's experiences during captivity areforthcoming.
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