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Aviation History
1936
1936 - 1362.PDF
MAY 21, 1936. FLIGHT. 559 The D.H. Gipsy Six (left) will shortly appear in a new form. Rather more power will be avail able and there will be provision for the D.H. V.P. airscrew. The Gipsy Major (right) gives 130 h.p. recent design and gives 200 h.p. from its six inverted air-cooled cylinders; the Major is similar in many respects but has four cylinders. Its power is 130 h.p. Top overhauls of the Major are unnecessary, and 750 hours may be run between complete overhauls. A new version of the Six, designated the Gipsy Six Mk.II has been developed and should interest commercial operators, par ticularly because its design .makes provision for the new De- Havilland variable-pitch airscrew, and because a higher con tinuous power is available. The new engine has a compression ratio of 6 : 1 compared with the standard ratio of 5.25 : 1. Fuel of a higher octane number than that specified for the Gipsy NAPIER The sixteen-cylinder Rapier engine, with its cylinders ar ranged in four blocks of four each, has been flying for a con siderable time in an Airspeed Courier and Saro Cloud aircraft. Its success has been such that not only is it being specified for the new Blackburn H.S.T.10 transport monoplane, but the upper component of the Short-Mayo '' composite '' machine for the transatlantic service will be fitted with four of these engines. The Rapiers in this particular machine are likely to be of the fully supercharged variety known as the Rapier V. This model has recentty completed its type test and gives a maximum output of 330-340 h.p. at 4,000 r.p.m. at 13,000 ft. For take off at sea level the engine offers 325-335 h.p. at 3,500 r.p.m. Another current version of the Rapier, desig nated the Mk. VI, is a moderately supercharged engine rated at 360 h.p. at 3,500 r.p.m. at 4,000 ft., and delivering a maximum of 395 h.p. at its full-throttle height of 5,800 ft. This is the type of Rapier which is being used in the new Blackburn monoplane. It operates on fuel of 87 octane num ber, and should give the new machine a very high performance. A larger type of Napier engine, and one which has not yet been installed in a commercial aeroplane, is the Dagger, which is available in fully and moderately supercharged forms. These are known as the Series II and III respectively. The former is rated at 695 h.p. U.i 10,000 ft. and the latter at 725 h.p. at 3,500 ft. Both operate on fuel of 87 octane number. The arrangement of the cylinders, of which there are twenty-four, is similar to that used for the Rapier. The latest version of the Pobjoy Niagara is the Mk. Ill, which gives 88/95 h-P- snd weighs 156 lb. The two most recent versions of the Napier Rapier available are the V and VI, giving 330/340 h.p. (max.) at 13,000 ft. • • and 360 h.p. at 4,000 ft respectively. Six Mk.I will be used. Accordingly the cylinder heads are of a new aluminium type which will permit- the use of leaded fuel. This, of course, will be a great advantage to operators in areas where high-octane fuel can be obtained most economi cally by the addition of tetra-ethyl lead. Some idea of the benefits which may be conferred by this new engine can be gauged from the fact that the D.H.86A' four-engined biplane will cruise at 155-160 when the Mk.If engines with V.P. airscrews are fitted, whereas with standard Gipsy Sixes driving fixed pitch airscrews the machine cruises at 140-145 m.p.h. A vacuum pump is being incorporated to drive the gyros of blind-flying instruments. (Makers: The De Havilland Aircraft Co., Ltd., Hatfield. Herts.)
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