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Aviation History
1947
1947 - 0980.PDF
FLIGHT JUNE 19TH, 1947 HELICOPTERING IN LONDON In the R-4 the top of the "stick" describes a circular motion which transmits a deal of vibration to the pilot's hand. In the S.51 this has been damped, but the result is a certain stillness or heaviness in the control. There is also a better interconnection between the pitch lever and the engine throttle, so that the pilot no longer needs to keep his eyes glued on the rotor rev. counter. The twist grip at the top of the pitch lever is now more of a vernier adjustment. The Pratt and Whitney engine is mounted horizontally in the bay behind the cabin. It drives the main rotor via a gear box and clutches. The drive to the tail rotor lies in a duct on top of the fuselage, and the shaft incorpor- ates universal joints made necessary by the angles in the shaft line caused by the relative positions of the engine and tail rotor. As already announced, the Alvis Leonides engine will be fitted in the British-built S.51S. This will slightly improve the power loading, as the Alvis engine is of greater power (500 h.p. at present). Some small amount of weight will, however, be sacrificed by the fact that, as the Leonides rotates the opposite way to the Wasp Junior, an extra gear will be necessary. - • Improved Performance From the performance point of view the S.51 is, of course, very much better than the R-4. With the WTasp Junior engine the tare weight is 3,735 ib, and as the maxi- mum loaded weight is 4,985 lb, there is a disposable load of 1,250 lb. This can be used according to the service to be operated For example, if a cruising range of 245 The lowest aerial view on record ? In this group, photo-graphed from a hovering Westland-Sikorsky S.51, Mr. A. Davenport, technical director of Westlands (right), Mr. PeterMasefield, Director-General of Long-Term Planning at the Ministry of Civil Aviation, and the editor of Flight, are justbeginning to realize the possibilities of pest-destruction by helicopter. The demonstrations given at Harrods' sports ground includedthe transport of a section of a bridge to an otherwise inac- cessible location. A special hoist on top of the fuselage of the S.51 is push- S button operated by the pilot. miles at 85 m.p.h. is needed, the payload becomes 390 lb. composed of two passengers and 50 lb of luggage. For a range of 150 miles the machine will carry three passengers and 70 Ib of luggage, and for really short hops, say of 50 miles, the luggage or other cargo can go up to 280 lb. The cruising speed of 85 m.p.h. corresponds to 65 per cent of the engine power. The top speed, which is of no great importance in a helicopter, is about 103 m.p.h., and the landing speed is, of course, anything from zero upwards. It is not always appreciated that a helicopter requires much more power for vertical than for slanting ascent, due to the fact that the airflow through the rotor disc changes a great deal. Similarly it requires more power for hovering than for slow forward flight. This fact is well brought out by the two ceiling figures. For hovering,
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