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Aviation History
1956
1956 - 0574.PDF
574 FLIGHT D.H. Super Sprite. A.t.o. droppable rocket pack. Basic motor: length, 117^in,diameter, 20 in. Empty weight, 620 Ib; fuelled weight, 1,460 Ib. Standard thrust, 4,200 Ib for 40 seconds duration; total impulse, 120,000 Ib-sec. Propellants: 57 galhydrogen peroxide at 80 to 85 per cent concentration and 5 gal jet fuel. Feed by 3,690 cu in nitrogen initially at 2,900 to 3,100 Ib/sq in. Nacelle: approximateoverall dimensions, length, 150in, height 32in and width 28in. Total weight of nacelle and fuelled motor, about 1,900 Ib: fall-weight during parachute-jettison cycle, 1,080 1b. AERO ENGINES 1956 . . . in the Comet 1 as a removable unit, complete with tanks from whichthe peroxide and a liquid catalyst were injected under pressure from gas bottles. This unit was not produced in quantity, but a development namedSuper Sprite is in full production as a a.t.o. motor for the R.A.F. (see accompanying data), and holds the first British Type Certificate fora jettisonable, liquid-propellant rocket motor. The tanks of the Super Sprite are of greater capacity than those of the Sprite, and the catalyst,instead of being injected, takes the form of a metal gauze through which the peroxide is injected. The specific impulse in the SuperSprite is also greater than that of its predecessor owing to the fact that it is a "hot" motor, kerosine being injected into the combustionchamber to burn in the free oxygen from the decomposed peroxide. In the much more powerful Spectre the propellants are fed by aturbine-driven pump energized by steam from decomposing peroxide. No details of the Spectre may yet be published but it can be statedthat it is being developed both as a jettisonable a.t.o. unit and as a permanently installed motor for supersonic fighters. HAWKER SIDDELEY. The Hawker Siddeley Group, Ltd., 18St. James's Square, London, S.W.I. All the multifarious nuclear-power interests of the Group are being brought together within the newHawker Siddeley Nuclear Power Company. Initially the new organ- ization will be principally charged with the task of collecting personneland conducting a broad programme of research. NAPIER. D. Napier and Son, Ltd., The Vale, Acton, London, W.3.After some 40 years of fame as manufacturers of high-quality piston aero engines, this long-established company is now concentrating itsaviation activities upon other types of powerplant. The bulk of this work is devoted to various types of shaft-drive gas turbine and athorough research and development programme into axial compressors (and the aerodynamics and thermodynamics of advanced engines gener-ally) is now paying off in the company's present range of products. This programme was carried out at the company's research station atLiverpool, which was the largest in Europe when the company built it in 1947. All the company's present engines are single-shaft units ofsmall diameter with excellent component efficiencies, automatic single- lever control and features which make them unusually easy to maintain.In their design the company have kept one eye, and sometimes two, on the power requirements of future helicopters. Design and prototype manufacture is undertaken at the headquartersat Acton, nearer the centre of London than any other major company in the aircraft industry. Large-scale production is allocated to thelarge factory at Liverpool which has been filled since 1952 with Rolls- Royce Avons, chiefly for Canberras, production of which is now drawingto a close. Flight development is conducted at an ad hoc establishment at Luton Airport where the company also undertake sub-contract workfor other companies. Also at Luton are departments engaged in the development of rocket motors and ramjets, this work being partly forthe guided-weapon programme of the English Electric Group (of which Napier is a member). Eland. A background of research into highly rated axial compressorswas a necessary pre-requisite to the evolution of this engine. Although it is of the single-shaft layout, the Eland has a higher work-per-stagethan any other engine in production, coupled with single-lever control and exceptionally easy handling. The basis of the design was theminimum size of spinner for a 3,000-h.p. airscrew, the intake following the spinner periphery and the remainder of the engine and accessorieslying within the 36in-diameter, minimum-drag cowling. For servicing, the Eland can be readily sub-divided into its con-stituent parts. Points worth commenting upon include the unusually efficient self-centring, single-stage reduction gear (three ratios are avail-able up to almost 14 : 1) incorporating a hydraulic torquemeter; auto- matic ice protection afforded by the multiple oil-cooler pads around the magnesium-alloy intake casting; aluminium-bronze compressor blading;upstream-injection nozzles in the low-pressure-drop tubular combus- tion chambers (which can be removed in situ); automatic variable-incidence guide vanes which improve handling and acceleration; top-temperature control governed by mercury-vapour sensing units;and provision for a reverse-pitch airscrew. The first engines were rated at 2,690 s.h.p. (3,007 e.h.p.) and weighedbetween 1,600 and 1,700 lb. Such units have been extensively flight- developed in a Varsity, Elizabethan and Convair 340. Last June aprice of £28,600 was quoted in America for Elands of this type. A change in turbine-blade material has now allowed a useful increase inmaximum temperature, which has resulted in the establishment of the NE1.6 rating of 3,500 e.h.p., with an s.f.c. of not more than 0.595.For a considerable period, development has been proceeding upon an advanced family of Elands with still higher temperatures and a pressureratio of 8 : 1. This new family of engines has resulted in the establish- ment of the NE1.5 rating of 4,200 e.h.p., at an s.f.c. of 0.56 and a specificweight of 0.43 lb/e.h.p. Cruising at 25,000ft and 400 m.p.h., the s.f.c. of the NE1.5 is expected to be not greater than 0.44. Although instal-lationally interchangeable with the NE1.1 and 6, the NE1.5 is consider- ably more advanced in design and incorporates an air-cooled turbine.In December a slightly earlier cooled-turbine variant, designated NE1.4, Napier: ramjet vehicle test firing with rocket boost. first run 13 months ago, was stated in America to cost £35,000,A completely separate development is the NE1.3 powerplant for the Fairey Rotodyne helicopter. This engine incorporates an auxiliarycompressor driven via a hydraulic coupling from the main power section. When the coupling is filled with oil the auxiliary compressoris accelerated until eventually the two rotating assemblies are clamped together to form, in effect, a single-shaft engine, the sole function ofwhich is to supply fresh compressed air to the helicopter rotor for combustion jets at the blade tips. Exhaust gas is taken out throughseparate tailpipes on either side of the hydraulic clutch. During this take-off, or hovering, condition the airscrews are held in super-fine pitchand used for directional control. In forward flight the hydraulic coupling is drained, and all cruising power is applied to the airscrews,the rotor being allowed to autorotate. It may also be commented that this powerplant has obvious attractions for use in fixed-wing aircraftwith blown flaps. Gazelle. In some respects this unusual power unit can be consideredas a free-turbine, shaft-drive Oryx with the layout described in the Napier Eland E.151 (NEI.3). Rotodyne powerplant. Ten-stage compressor,six combustion chambers and three-stage turbine, the rotating assembly being coupled to an airscrew reduction gear at the front and (via a fluid clutch) a nine-stage auxiliary compressor at the rear. Overall diameter, about 40in (basic, 36in); length, 158.25in; dry weight, 2,350 Ib; mass flow, 31 Ib/sec; pressure ratio, 7:1;maximum power (forward flight), 3,000 e.h.p. (2,800 s.h.p.+ 500 Ib) at 12.500 r.p.m. with s.f.c. of 0.624.
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