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Aviation History
1963
1963 - 1708.PDF
FLIGHT International. 19 September 1963 519 400 - 300 C/S 500 ^ Tubing by Flexible Ducting Ltd: Featherflex running horizontally in background and insulated Flexflyte (dark coloured, vertically in centre) Avicaflex duct assembly with g'.moal joints Sangamo Weston frequency-meter miniature INDUSTRY International. bal joints in the high-temperature air ducting systems, fuel piping, drain lines, fuel feed and air supply piping. The undercarriage units are operated at 4,0001b/sq in, with DTD585 fluid; a typical duct assembly embodies 3£in gimbal joints CE16158 and 4in gimbal joint CE15216. Integral fuel tanks and pressure cabins in the Belfast are sealed with p.r.c. (poly- sulphide rubber compounds) supplied by BRITISH PAINTS LTD, Britannic Works, Portland Road, Newcastle upon Tyne 2. These are two component compounds, the white base being supplied either in paste form or as a liquid. After mixing with the chocolate-coloured curing agent, the mixed components are applied by gun or brush to give firmly adhering, flexible rubbers. By suitable formation techniques, a range of different application *iives is made available for different purposes. Long-application- life material is applied to mating surfaces, allowing riveting through the liquid material before it sets. In fuel areas, after the seal ants have cured, a brush coat of one-part synthetic rubber coating is applied to all exposed sealants. Over a hundred separate ducting items for the Belfast have been supplied by the Aviation & Electronics Division of FLEX IBLE DUCTING LTD, 55 Lattimore Road, St Albans, Herts, who comment that the special lightweight properties of these ductings results in a weight saving of 401b. Their lightness, coupled with flexibility, permits easy and quick installation and eliminates the possibility of damage to other parts during installation. Standard Flexflyte has been used for radio cooling. Special flexible ducts were designed by the company to act as fuel shrouds, encasing pressure refuelling 'ines. Externally, these ducts deal with cabin pressure at altitude; internally, they are designed to deal with fuel at 501b/sq in in the event of leakage during refuelling. The majority of the ducts are used for hot air and air-conditioning feed lines. These are Featherflex ducts, a relatively recent development and notable for extreme light ness—a 1ft length, ljin in diameter, weighs les s than £oz. The Belfast is the first aircraft to incorporate Featherflex. . All but one of the sealed micro-switches >n the Belfast are made by HONEYWELL CONTROLS LTD at their Newhouse, Lanark shire, factory. Approximately 200 sealed rnicro-switches of the HS, SE and EN types are htted in the Belfast according to the require ments of the various applications. The EN type, used on the undercarriage, has an O-ring seal in the plunger mechanism, glass-to-metal terminal seals and potted leadwire terminations which prevent entry of dust, moisture or air into the switching chamber. An ice scraper ring on the actu ator shaft removes ice or mud which could cause jamming. A particular application for the HS type switch is in the throttle box, where almost a hundred switches are employed in signal and interlock circuits associated with throttle positions. This switch in the Belfast is a special variant of the standard HS, giving a lower differential travel. All HS switches are hermetically sealed, being metal-cased with glass-to- metal seals, and filled with dry nitrogen. Honeywell add that among the special micro switches produced for the Belfast one "particularly exacting example" was for a three-pole sealed switch with gold contacts and independently screened sec tions between each switch, along with special screened cables. This switch, 421-EN-I, is used in triplicate in rudder trim controls. LUCAS GAS TURBINE EQUIPMENT LTD, Shaftmoor Lane, Birmingham 28, supply Lucas GTE low-pressure-shaft governor the fuel system for the Belfast's four Tyne engines. This system consists of a fuel pump, fuel control unit, variable datum governor and duplex type sprayers. Fuel is supplied from the aircraft tanks to the positive displacement variable stroke pump via a heater, strainer, backing pump and filter. It is then passed at high pressure through the fuel control unit incorporating manual and automatic controls which enable the correct flow of fuel to be supplied to the engine as necessary under all flight conditions. Over the range of conditions from flight idling to maximum reverse, this fuel is controlled by a variable-datum governor driven from the engine low- pressure shaft. This governor limits the speed of the low-pressure shaft, that for the high-pressure shaft being limited by a governor in the pump V ~1 Rotox I7± h.p. 28V electric starter Approximately 100 Rotax components (ROTAX LTD, Willesden Junction, London NW10) are fitted in the Belfast, the majority in the Rotax-designed generating and engine-starting systems, the former a com bined system using 200V variable-frequency three-phase ax., and 28V d.c. Each engine has two 50kVA, 200V brushless rotating- diode alternators, one of which is primarily used to supply its own engine and propeller de-icing loads, while the other supplies a.c. current for navigation instruments, tail and windscreen de-icing and air condition ing. The second alternator also supplies, via transformer/rectifier units, the d.c. supply. A further 50kVA alternator is operated by an a.p.u., and is used for ground operation on a.c. checkouts, and supplies, via a regulated t.r.u., d.c. power for engine starting if required. Rotax components in the engine-starting system consist of one 17J h.p. electric starter to each engine, with associated relays and resistor-unit as semblies. Two Rotax high-energy igniters are fitted to each engine. In view of the aircraft's strategic role, several methods of engine starting have been provided, including ground supply, internal batteries, batteries plus a.p.u., and batteries plus a.p.u.
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