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Aviation History
1957
1957 - 1106.PDF
196 FLIGHT, 9 August 1957 (Left) A rotor-blade root, showing re-infor- cing skin laminations,at- tachment fittings, fuel pipe in leading edge, and the trifurcated air- duct union. (Right) Pre- paring the rotor head for one of the many test programmes; this pic- ture g'rres a mid idea of its size. ROTODYNE air from the auxiliary compressor is delivered upward, ahead ofthe firewall, into a Nimoruc 75 elbow which connects with the duct in the leading edge. Apart from this and the differentialpropeller-pitch control, the only major non-standard feature in the Eland installation is the fan-cooled oil cooler, for whichNapier supplied a special drive. Rotor System. This is essentially an all-steel structure (toovercome the fatigue-life problems associated with high-strength light alloys), considerable resort being made to nickel alloys inthe combustion- and compressed-air-delivery zones. Rotor Blades. Each 45-ft rotor blade is a two-piece unit—theaerofoil structure and the inner spar (in this connection one regards the combustion chamber as a separate entity, even thoughit has a considerable influence upon the blade structure). The blade aerofoil is a symmetrical one of low drag, but notlaminar flow. Because of the great importance of fore-and-aft e.g. position on flutter, the blade is designed with a solid steel leading-edge and very thin light-alloy trailing-cdge. The load-carrying torsion box has a massive machined-steel (D.T.D.730) front sparand a 16 s.w.g. stainless-steel (D.T.D.166) rear spar made from two folded L-plates riveted together to form a channel section.The pierced rib blanks, closely spaced, are made in thin-gauge D.T.D.171 stainless steel. They are attached to the 20 s.w.g.D.T.D.166 skin by countersunk Monel rivets. Down the interior of the blade run the three Accles and Pollockair-delivery tubes of T.58 steel, each in one piece, with the gauge reduced in steps from 20 s.w.g. at the root to 29 s.w.g. at thetip. These tubes are constrained at the root only and they are passed through clearance holes in the ribs until they are locatedas a free sliding fit in the intake cuffs on the combustion chamber. Fluon rings are used to position the tubes at alternate ribs andprevent raiding. Fluon is a plastic which retains self-lubricating Cockpit layout: 1, fuse panel; 2, circuit breaker; 3, fuel system; 4, warning lights; 5, G.M. Mk 48 compass control panel; 6, flight instru- ments; 7, engine and auxiliary instruments; 8, engine transition panel; 9, collective pitch control (dual on port side); 10, screen-wiper control; 11, toe brakes; 12, propeller pitch control levers; 13, power levers. \ Basic performance (estimated): cruising speed, 170 m.p.h.: payload, 40 to 48passengers for ranges up to 430 miles; vertical rate of climb at sea level at maximum power, 1,670 ft/min; direct operating cost per passenger mile, about 3 pence at100 miles range, falling to 2 pence at 250 miles and 2.3 pence at 450 miles. properties up to 250 deg C, so there is no restriction on thesliding of the tubes. The leading-edge spars are worthy of note, for they aremachined in pairs from a 3 5-ft rolled billet supplied by the English Steel Corporation—believed to be the longest high-tensile-steelbillet made in this country. After parting and rough machining they are returned to Sheffield for heat treatment. Final machiningintroduces two spanwise grooves in the leading edge which form recesses for the fuel pipe and the |in diameter steel e.g. balancerod—lateral e.g. is adjusted by weights at the root end and shims on the blade skin at the tip. The aim is to provide fully inter-changeable balanced blades. The steel skin is formed from a single piece—root to tip andtop to bottom flange of the rear spar. The leading-edge radius is cold-drawn by Fairey on a special apparatus. Assembly of theskin to the ribs is done in a type of double envelope jig developed for the purpose. At the tip of the blade spars are the simple fittings for thecombustion chambers. At the root the aerodynamic torsionai loads are diffused by skin laminations into the flanges of fittingsbolted to the two spars. The high centrifugal loads (a blade
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