FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1931
1931 - 1252.PDF
SUPPLEMENT 10 FLIGHT 88 THE AIRCRAFT ENGINEER NOVEMBER 27, 1931 of about 3 per cent, (r) With the amount of altitude control limited bystops fitted by the engine makers. This corresponds to ordinary Service use. The greatest maximum range at all heights for this aircraft was obtainedby the use of sufficient altitude control to cause a fall in the K.l'.M. of about 3 per cent. (" Weak Mixture.") The maximum range then appears to remainconstant with height. With the maximum amount of altitude control possible without a fall inB..P.J1. (" Normal A.(J."), the maximum ranges are lower throughout, and there is a slight increase in maximum range with height. This increase ismuch smaller than that found for the Vickers' Venture. With the amount of altitude control limited by the stops, as in ordinary Service use of theaircraft, the ranges at all heights are considerably lower, and the maximum range appears to decrease with height. Under both Normal A.C. and Weak Mixture conditions, the altitudecontrol and throttle levers must be manipulated with more than ordinary precision to obtain consistently low consumptions, and when running onweak mixtures, the engine is unpleasantly " rough." Ketarding the ignition from 42<J advance to 35° appears to cause increasedconsumptions at the lower throttle openings. MEASURED SPINS ON AEROPLANE 11. By S. B. Gates, M.A. Communicated by the Director of Scientific Research, Air Ministry. R. & M. No. 1403 (Ae. 524). (5 pages and 3 diagrams.) April, 1931. Price 6d. net. As a preliminary to spinning experiments with a raised tailplane, a cautiousexploration of the spin of Aeroplane H was attempted, liccords of normal acceleration, rate of turn and rudder movement were made in spins to rightand left under conditions to give maximum ease of recovery. The entrant rudder angle was limited to 12° in right-hand spins. Spins in either Rense are characterised by a few slow steep turns, followedby a Hick into an extremely fast and ilattish spin (time of turn 1-2 sees., Incidence 57°). .Recovery is immediate it attempted before the Hick, and notdifficult in spins to the left if delayed till after the flick. Kecovery from the fast spin to the right is extremely difficult, and the experiment was dis-continued after two such spins, in which 40 and 34 turns were made before recovery, had been done.The high rate of rotation has a confusing effect on the pilot, who is liable to lose his sense of direction of the rudder control, and also may find itdifficult to hold full rudder against the spin for a long enough time to ensure recovery. TAKE-OFF AND LANDING OF AIRCRAFT. By D. Rolinson, M.Eng. Communicated by the Director of Scientific Research, Air Ministry. R. & M. No. 1406 (Ae. 527). (25 pages and 20 diagrams.) June, 1931. Price Is. 9d. net. There have always been considerable differences in the measurements oflanding and take-off runs of an aircraft on a given day. The standard method used to determine these distances is direct measurement, the points oftouching the ground and taking off being spotted by two observers. To deter- mine height cleared, a photograph of the aircraft is taken at an arbitrarydistance from the start of a run and the scale for measurement depends for accuracy to some extent on the judgment of an observer. Errors of measure-ment are considerable but do not account for the marked differences obtaining. Further, the standard method does not give distance to clear a given heightcither taking off or landing. A camera was therefore made up at this station to give a reproduction of a take-off by taking a series of photographs athalf-second intervals ou one plate, from the start of the aircraft, to the time when it was 80 ft. or more above the ground. By this means the flight pathof the aircraft was obtained, and it was possible to give a reasonable estimate of the distance necessary to clear a given obstacle. The accuracy of thismethod depended only on the accuracy of measurement of the distance from the- camera to the course along which the aircraft took off. A secondInstrument, a modification of a panoramic camera, was made at H.A.E., and with thin camera runs of seven aircraft, four biplanes, and three monoplaneswere obtained. The rraults form the basis of this report. Lift and drag coefficients have been calculated from the results calculatedfrom the film records, and for two aircraft, the Wapiti and the Virginia, full scale determination of the (Wfiiciontu WUK made at a height of 2,500 ft. forcuinpiiriitivc pur|PCiws, A few (cut* were carried out to discover whether a rapid increase oi angle oi attack gave an increase of lift-coefficient showed aslight increase. It has definitely been established that an aircraft can take off and laudat a speed much below that appropriate to the incidence obtaining ; that the lift-coefficient for an aircraft near the ground is much higher than wouldbe expected for the same incidence in free air in steady flight. It is shown that it is possible to obtain the distance necessary for a landing or take-offto be effected when a given height has to be cleared. It is also shown that it is within the power of the pilot to modify this distance considerably. ON THE RELATION BETWEEN HEAT TRANSFER AND SUR- FACE FRICTION FOB LAMINAR FLOW. By A. Page, A.R.C.Sc, and V. M. Falkner, B.Sc. R. & M. No. 1408 (Ae. 529). (30 pages and 12 diagrams.) April, 1931. Price Is. 6d. net. The heat transfer from a surface immersed in a moving fluid depends notonly on the surface friction, but also on the general fluid flow in the neigh- bourhood of the surface. Any attempt to obtain a theoretical relation betweenheat transfer and surface friction necessarily involves therefore the establish- ment of a connection between surface friction and the neighbouring fluidflow, and consequently the problem must be restricted to those types of motion for which such a connection can be found. There apjiear to be only two typesof motion for which this requirement can be fulfilled ; first, flow in pij>es. the second, How past surfaces, for which the boundary layer theory is applicable. The paper gives a mathematical theory of the heat transfer from a surfaceover which the fluid flow in the boundary layer is laminar and two-dimensional, when the heat flow is steady. A general differential equation for heat transferhas been obtained from a consideration of the heat balance at any point in tho boundary layer, and after simplification, this equation has been solvedby artifices similar to those used to obtain n solution of the boundary layer equations. The solutions obtained were adapted to two problems of practical interest,(o) the heat transfer from a plane placed in a fluid stream in the direction of motion, and (h) that from a generator strip of a circular cylinder. In eachcase relationships were obtained between the intensity of heat transfer and surface friction. These theoretical relationships were compared with thoseobtained from measurements of the heat transfer from a thin platinum fo i 1 placed in a wind stream and from a nickel strip embedded just below th esurface of a cylinder. The intensity of surface friction for the platinum foil was known theoretically, and that for the cylinder was taken from earlierexperiments. The agreement between theory and experiment was close for both the plateand cylinder. SUMMARIES OF N.A.C.A. TECHNICAL REPORTS The National Advisory Committee for Aeronautics is the American equivalent of our Aeronautical Research Committee, with headquarters at Washington, D.C. The Technical Reports issued By the N.A.C.A. are obtainable from the Superintendent of Documents, Washington, D.C., U.S.A. In the summaries printed below the prices of Reports are given. These prices are net, and a small amount should be added to cover postage. For the guidance of potential purchasers it may be pointed out that the Reports rarely exceed 5 oz. in weight. No. 380. PRESSURE DISTRIBUTION OVER THE FUSELAGE OF A PW-9 PURSUIT BIPLANE IN FLIGHT. By Richard V. Rhode and Eugene E. Lundquist. Price 20 cents. This report presents the results obtained from pressure distribution testson the fuselage of a PW-9 pursuit aeroplane in a number of conditions of flight. The investigation was made to determine the contribution of thefuselage to the total life in conditions considered critical for the wing structure, and also to determine whether the fuselage loads acting simul-taneously with the maximum tail loads were of such a character as to be of concern with respect to the structural design of other parts of the aeroplane.The tests were conducted by the National Advisory Committee for Aero- nautics at Langley Field, Va., during the spring of 1929. The results showthat the contribution of the fuselage toward the total lift is small on this aeroplane, ranging from slightly less than 3 per cent, at the lower anglesof attack to about 4 per cent, at the higher angles, which approximately compensates for the portion of the wing area replaced by the fuselage.Aerodynamic loads on the fuselage are, in general, unimportant from the structural viewpoint, and in most cases they are of such character that, ifneglected, a conservative design results. In spins, aerodynamic forces on the fuselage produce diving moments of appreciable magnitude and yawingmoments of small magnitude, but opposing the rotation of the aeroplane. A table of cowling pressures for various manoeuvres is included in thereport. No. 381. STATIC, DROP, AND FLIGHT TESTS ON MUSSEL- MAN TYPE AIRWHEELS. By William C. Peck and Albert P. Beard. Price 15 cents. This Investigation was conducted at the Langley Memorial AeronauticalLaboratory of the National Advisory Committee for Aeronautics during the period from January to July, 193i, for the purpose of obtaining quantitativeinformation on the shock-reducing and energy-dissipating qualities of a set of 30 by 13-6 llUSSClman type airwheela. i'he Investigation consisted ofstatic, drop, and flight tests. The static teats were made with inflation pressures of approximately, 0, 5, 10, 10, 20 and 25 lb. per sq. In., and loftd-inga up to 9,600 lb. The drop tests were made with inflation pressures of approximately 6, 10, 15, 20 and 25 lb. per sq. in., and loadings of 1,840,2,440, 3,050 and 3,585 lb. The flight tests were made with a VE-7 aeroplane weighing 2,153 lb., with the tyres inflated to 5, 10 and 15 lb. per sq. in. Thelanding gears used in conjunction with the airwheels were practically rigid structures. The results of the testa showed that the walls of the tyres carrieda considerable portion of the load, each tyre supporting a load of 600 1b with a depression of approximately 6 in. The Bhock-reducing qualities,under severe tests, and the energy-dissipating characteristics of the tyres, under all tests, were poor. The latter was evidenced by the rebound presentin all landings made. In the severe drop tests, the free rebound reached as much as 60 per cent, of the free drop.The results indicate that a shock-reducing and energy-dissipating mechan- ism should be used in conjunction with airwheels. No. 384. THE COMPARATIVE PERFORMANCE OF SUPER- CHARGERS. By Oscar W. Schey Price 5 cents. This report presents a comparison of superchargers on the basis of thepower required to compress the air at a definite rate, and on the basis of the net engine power developed at altitudes from 0 to 40,000 ft. The investiga-tion, which was conducted at the Langley Memorial Aeronautical Laboratory, included geared centrifugal, turbine-driven centrifugal, Boots, and vane-type superchargers. It also includes a brief discussion of the mechanical limitations of each supercharger, and explains how the method of controlaffects the power requirements. The results of this investigation show tnai for critical altitudes below 20,000 It. there Is a maximum difference of about6 per cent, between the amounts of net engine power developed by the various types of superchargers when ideal methods of control are employed, outfor critical altitudes above 20,000 ft. an engine develops considerably more power when equipped with a turbo centrifugal supercharger than wltn.,"fother type. The Hoots type gives the lowest net engine power of all at nig" critical altitudes, because It hag the least efficient type of compression.The throttling method of control used on the geared-centrlfugal typ« "' supercharger is very unsatisfactory at low altitudes from ft net e?»J"power standard when compared with the method used on the iBoow turbine centrifugal type. 1174 h
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
