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Aviation History
1944
1944 - 0962.PDF
500 FLIGHT MAY IITH, 1944 BRITISH HELICOPTERS tical engineering oi the theories then obtaining was later described by Lord Weir as " a monu ment to mechanical engineering." In this connection it is interesting to find that his studies and researches have led Igor Sikorsky to the same basic rotor system so far as cyclic pitch change and rotor drive are concerned. Reference has been made earlier to the problem of counteracting torque reaction in a single-rotor helicopter.- When G. and J. Weir decided to initiate research into rotor systems, it was decided that by employing two rotors, side by side, running in opposite directions, at least that problem would be side-stepped. The two-rotor arrangement was never regarded by them as the ultimate solution, but it did give an opportunity to study other problems without having to tackle that one at the same time. Moreover, the Focke-Wulf concern of Bremen (who earlier had obtained the German licence to build Cierva Autogiros) had built a side-by-side rotor helicopter which had performed well, so there was justification for believ ing that for a "flying test bed," which was all the first Weir helicopter was in tended to be, this arrange ment would short-circuit some of the problems. Just to make absolutely sure that there - was no easier'' way, a unit with two superimposed coaxial rotors was designed ~.nd some components tested. It was concluded, however, that this arrangement intro duced so many aero dynamic and constructional difficulties that the side-by side arrangement was finally selected. One of the reasons for this was also that, in an experimental machine such as that contemplated tfe- if Mr R. A. Pullin flying the W.6. This machine carried many passengers, on one occasion two of a combined weight of 300 lb. and it was thus necessary to guard against serious accidents by ensuring that the machine would be able to descend en Autogiro (with tjjr^- •HBJHKr blades autorotating) at a •<••—ww—1 iy 1. .1...in.,,i.i reasonable rate. This en tailed rotors of fairly large disc area. The rotor hubs for the side - by - side arrangement were designed to operate on the direct-pitch-controi principle instead of on the tilting-rotor-head principle used in the Autogiros. For control while hovering, two methods were tested. In one, control about the roll ing and pitching axes was by tilting the lift vector by the application of harmonic pitch change; in the off ^i control about the rolling axis was obtained by con tinuous ^differential pitch change (adding pitch to one rotor and reducing the pitch of the other), and Mr. R. A. Pullin in the cockpit of the W.6 during a flight, snapped by his passenger. The instrument panel does not look very terrifying. the possibility of mechanical failures could not be ruled out. about the pitching axis by harmonic pitch change. Both were found to work satisfactorily, but less displacement of the aircraft occurred when the rolling control was by differential pitch change, and most of the flying was done with that arrangement. Normal flapping and drag hinge articulation were in cluded, together w-ith a free wheel on the final rotating member of the hub. This permitted autorotation as soon as the desired condition arose. The first Weir helicopter, known as the W.5, was ol wooden construction. The outriggers which carried the side-by-side rotors were also of wood and were plain boxes without fairings. The engine- was the little Weir four- cylinder air-cooled engine- Test rig for the special coo!-, ing fan on the Gipsy Six. &
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