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April, 1931 AIRCRAFT ENGINEERING 101 Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued attemp t to reverse the rate of roll beyond the counting mechanisms a t either end of th e course JAPAN stall. The rudder appears to lose no power are controlled by a single instrument. AERONAUTICAL RESEARCH a t the stall and is effective in reversing the A detailed account is given of the apparatus INSTITUTE rat e of roll and yaw at both incidences. for this system which was developed for measur IMPERIAL UNIVERSITY, TOKYO ing the speeds of racing seaplanes over the (The University, Komaba, Tokyo) 3-kilometre course at Calshot during 1929. R. & M . No. 1342 (Ae. 474). June, 1930. Two cinema cameras were used and these, in Vol. VI, Part I. Report No. 67. January, Airscrews for High Speed Aeroplanes. By addition to recording the passage of the aircraft 1931. Air Flow Through an Exhaust Valve H . Glauert. (Price 1s.) a t either end of the course, by a scries of with a Conical Seat. By Keikiti Tanaka. Since little is known of the characteristics of photographs, recorded the time at which each an airscrew a t the high rates of advance which exposure was made in terms of vibrations of a The paper is a continuation of the author's occur with modern racing aeroplanes, it is tuning fork, which was in electrical connection former work on the air flow through a suction desirable to examine theoretically the most with counters in both cameras. valve with conical seating (Reports of the suitable type of airscrew for modern and future institute Nos. 50 and 51). In the case of a The apparatus, which is built up from com high speed aeroplanes, to determine the suction valve, air flows from a suction pipe into mercially produced components, has proved a cylinder of larger diameter. In the present efficiency of these airscrews, and to consider very reliable in service. The accuracy with case of an exhaust valve, on the contrary, air th e possibility of improving the low static which th e time of any one transit of th e aircraft thrus t which usually accompanies a high pitch/ flows from the cylinder into an exhaust pipe can be determined is not less than 1/20 second diameter ratio. of smaller diameter. In other words, air flow so tha t speeds of about 350 m.p.h. over 3 kilo diverges through a suction valve and converges Adopting a few simplifying assumptions, the metres may be measured to the nearest ½ m.p.h. through an exhaust valve. This difference characteristics of a series of high pitch air This is sufficient for experimental work, but it between the two cases is fundamental and screws have been calculated, and these results could be considerably improved by a modifica results in their having different flow character hav e been used to establish a relationship tion to the design of the apparatus if occasion istics. between the pitch/diameter ratio, torque demanded. The necessary modifications are coefficient and solidity of an airscrew operating briefly discussed, and two alternative schemes The present paper deals with this case of an exhaust valve. Some remarks are also made near th e state of maximum efficiency. Another outlined. A theory of time determination for on mathematical study; in divergent flow approximate formula has been derived for the an apparatus functioning ideally on th e principle efficiency of the airscrew, and these formulae of th e present design is given in an Appendix. such as with a suction valve two-dimensional have been used to determine the most suitable flow is similar to the practical flow of three typ e of airscrew for a high speed aeroplane. dimensions. In convergent flow such as with R. & M . No. 1348 (Ae. 480). July, 1930. A simple formula has also been derived for the an exhaust valve, however, this is not the case On the Validity of Large Scale Tests in an static thrus t of a high pitch airscrew. and particular consideration is necessary to Open Jet Wind Tunnel. Tests on a One-Fifth apply it to the practical flow. Th e analysis suggests that the tip speed of Scale Bristol Fighter in 5-ft. Open Jet Tunnel. th e airscrew may be limited to the moderate By W.G.A . Perring and C Callen. (Price 9d.) value of 900 f.p.s. and, using a suitable gear GREAT BRITAIN ratio, an efficiency of over 80 per cent may The tests were undertaken to investigate the n be anticipated. For a modern racing th e possibilities of experiments in an open jet AERONAUTICAL RESEARCH aeroplane, the most suitable airscrew is one tunne l upon aeroplanes of wing span greater COMMITTE E wit h two blades of diameter 10-ft., and it is tha n the jet diameter. Interest in the tests (H.M. Stationery Office, London) was chiefly concerned with the measurement necessary to use a gear ratio of the order of of changes in the force along wind, due to 0.6, bu t as the speed of th e aeroplane increases R. & M. No . 1341 (Ae. 473) . May, 1930. th e need of a gear ratio will disappear and the changes in the parts of the aeroplane situated Full Scale Determinations of the Motions, at most suitable airscrew will be one of smaller near the centre of the jet. the Stall, of a Bristol Fighter Aeroplane with diameter with a larger number of blades. The Th e tests were carried out in a 5-ft. open jet Slot and Aileron Control on both Planes. By relatively poor static thrust is an inevitable tunnel (R. & M. 1364. The 5-ft. open jet wind K. W. Clark. (Price 9d.) consequence of th e high speed of the aeroplane, tunnel, R. A. E.—F. B. Bradfield) on a one- being directly proportional to the power of fifth scale model Bristol Fighter. Lift and These experiments continue the investigation th e engine and inversely proportional to the drag without airscrew, and with stopped air of the behaviour of aeroplanes at large angles speed of the aeroplane, irrespective of the screw, and the lift and net thrust with airscrew of incidence when certain controls are applied. Previous reports have dealt with a standard diameter of the airscrew or of the gear ratio; running have been measured at angles of th e only hope of improvement is to use a Bristol Fighter (R. & M. 1181), a Fokker incidence varying from —4 deg. to 8 deg. variable pitch airscrew. F.VII 3 M monoplane (R. & M. 1228), and an Fro m the results the pitching moments have been calculated, the additional drag due to a Avro 504 N (R. & M. 1263). The flying for the stopped airscrew has been deduced and the results shown was carried out between June, R. & M. No. 1343 (Ae. 475). February, effective thrust of the airscrew has been 1929, and January, 1930. 1930. A System for the Automatic Timing determined. The results are compared with A Bristol Fighter aeroplane fitted with slot of Aircraft over a Speed Course. By J. K. those for similar tests carried out on the same and aileron control on the top and bottom Hardy and K. V. Wright, with an Appendix model in the Duplex tunnel at the National planes was used. The motions of the aeroplane, by S. B. Gates. (Price 1s.) Physical Laboratory, Teddington. together with th e angles of incidence and side slip and the movements of the controls, when Accurate timing of an aircraft over a speed I n addition, some exploration of the jet was certain controls were applied at two initial course with watches by observers stationed at made with the model in position. incidences, were recorded photographically. either end of the course has been found un The tests have demonstrated the possibility Below and above the stall th e lateral control satisfactory, even when the most elaborate of measuring in an open jet wind tunnel the produces a rolling moment of the right sign, precautions have been taken. A system has changes of drag or thrust resulting from but above the stall it is not always powerful been devised which eliminates the errors, both modifications to parts of th e aeroplane situated enough t o reverse angles of bank over 60 deg. huma n and instrumental, that were associated near the axis of the jet, even when the aero A considerable amount of yaw results from any with the older system. In this, the timing plane span greatly exceeds the jet diameter.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Apr 1, 1931
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