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Aviation History
1950
1950 - 0471.PDF
FLIGHT, 9 March 1950 31J Simple mechanical layout—afforded by the use of a jet-pro-pelled rotor—and a clean fuselage design characterize the S.O. 1110. A radial engine drives the Turbomeca compressor. ahead of the main rotor blades, and regulate the pitch of the latter as a function of their own flapping. This reduces flapping of the main rotor blades and so reduces vibration. The rotor head can also be displaced parallel to itself in the longitudinal sense to trim for e.g. variation and take load off the stick. Correction of lateral displacement of the e.g. when carrying pilot and passenger of different weights is made automatically by mounting the seats on a balance linkage coupled to the lateral control. Tests of the Nord 1700 during the past year have demon- strated that there is practically no inter-action of one con- trol on another, this being due to the tail arrangement and the automatic correction for torque reaction. S.E.3110 - The S.E. 3110 helicopter has*been designed by the rotating wing department of the Societe Nationale de Constructions Aeronautiques du Sud Est, under the direction of MM. Marchetti and Renoux and its general layout has been determined by the following considerations: (1) to obtain as high a rate of climb as possible; (2) to land in auto- rotation with as low rate of vertical descent as possible. Other performance characteristics, and in particular high- speed performance, have been controlled by these two con- siderations and the designers have tried to ensure that the maximum power of the engine can be used, without any limitations being imposed by vibration, by avoiding stall- ing of the retreating blade even when flying at altitude. A monocoque fuselage is used, giving low drag for mini- mum weight and maximum useful volume. A Salmson GNH nine-cylinder air-cooled radial engine (203 h.p. at take-off) is mounted with crankshaft vertical, giving low installed power-unit weight per h.p., steadier torque, and lower height than would be necessary with an in-line or flat engine. This arrangement makes it possible to arrange a large cargo compartment under the e.g. Controls are similar to these already tried out on the S.E. 3101, with the addition of trimming by means of longitud- inal cyclic-pitch control. Simplification of pilotage has been obtained by adequate linkage of controls in order to obtain automatic correction of torque reaction and pitch / throttle co-ordination*? The engine is boltecl^ferectlv on to the lower face of the transmission box (which is of welded steel and provides the support for the engine /rotor assembly) and the box itself is attached to the fuselage by a pyramid structure of welded steel tubes. The transmission box contains the gear trains driving the two cooling fans ; a centrifugal clutch ; a double epicyclic reduction gear; a pawl-type free-wheel; the gear train for the tail rotor drive ; and the main rotor-drive shaft, Drive for the tail rotors is via an oblique, shaft in the fuselage, an auxiliary multiplier drive with pick-up for the rev-counter drive, and a iong shaft extending to the tail and supported in four floating bearings. The tail unit con- sists of a gearbox carrying two struts on which the two two-bladed rotors are mounted. Pitch / throttle anti-torque linkage is provided to ensure as good co-ordination as possible between the main rotor pitch, engine power, and tail-rotor pitch, and so make it unnecessary for the pilot to have to make constant adjust- ments to throttle and tail-rotor pitch. The system is based on the fact that over the range of speed used the engine torque only depends on the extent to which the throttle is opened. Its novel feature lies in a direct connection be- tween the anti-torque controls and the carburettor lever, so^RiJCWed that the torque correcting movement is pro- pdftionaJVo engine torque, and in a linkage between the pitch imer and the motor cycle throttle grip providing: (1) Starting and warming up the engine by rotation of the throttle grip at low pitch; (2) in flight, maintenance of constant rotor speed (or one slightly increasing with pitch) when the collective-pitch lever alone is adjusted; (3) ad- justment of rotor speed by the throttle grip. There is no action of the pitch lever on the throttle or anti-torque controls when the throttle grip is closed (i.e., energy land- ing in auto-rotation). S.N.C.A.S.O. JET ROTORS The rotating-wing department of the Societe Nationale de Constructions Aeronautiques du Sud Ouest, under the direction of M. Paul Morain, has devoted itself to the development of jet-propelled helicopters, a type which is, of course, the subject of considerable research all over the world. Many have succeeded in flying, the first in Austria towards the end of the war, others in America during the last two years. The principal characteristic of jet-propelled helicopters is the absence of a mechanical drive to the rotors, the blades instead being driven by gases expelled from nozzles at their tips. This simplification brings the benefits of low first cost and low maintenance cost because it does away with clutches, free wheels, and gears operating under very severe conditions. Moreover, single-rotor mechanically driven helicopters have to have some torque compensating device such as a tail rotor, which causes a pure loss oi some 10 per cent of the engine power and can be the cause of many mishaps when manoeuvring near the ground. Jet propelled types are quite free from this dis- advantage. To offset the quoted advantages, the jets have the disadvantage of using more fuel—though this, in turn, is compensated by the increased useful load and •ii. A blade-tip jet unit (above) and rotor head of the S.O. 1110.
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