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Aviation History
1955
1955 - 0845.PDF
FLIGHT, 17 June 1955 843 SINGLE-SPOOL TURBOPROP . . . mind, each of the four major assemblies was arranged as a self-contained unit as shown in Fig. 5. A new or reconditioned com- pressor, reduction gear, turbine or individual combustion chamberscould therefore be removed and replaced very readily. It was intended ultimately that the overhaul life of the cold com-ponents of the engine would be 2,000 hr and of the hot parts, 1,000 hr. Some of the more important features of the enginewere then described in detail by Mr. Penn and, although most of these points were covered in our previously mentioneddescription, some are well worth reiterating. For example, Mr. Penn emphasized the advanced design of the reduction gearwhich, although designed initially for a power of 2,700 s.h.p., had satisfactorily run at 3,700 s.h.p. over long periods. The geometryof the gearing was such that tooth deflections largely cancelled each other out and gearing assemblies were arranged to be self-centering; also the construction of the torquemeter was such that the gearing was not mechanically fixed to the casing. Thesefeatures had resulted in mechanical efficiencies exceeding 99 per cent, together with a very low noise level. The torquemeter hadproved to be consistently accurate within ± 1 per cent of the calibrated dynamometer readings over the entire normal operatingrange, and had proved itself very valuable during flight trials. A feature of the compressor was that the blading was of aluminium bronze, which had high fatigue strength and goodcorrosion resistance. Another important factor was that, as such alloys are bearing materials, a tip rub did not have a disastrouseffect. Intensive development had resulted in a compressor with characteristics very satisfactory from the point of view of enginehandling; without recourse to blow-off, good efficiencies were obtained well away from the surge line, giving the desiredacceleration characteristics (Fig. 4) without loss of design efficiency. It was therefore possible to ground-idle the Elandat approximately 6,000 r.p.m. (compared with a maximum speed of 12,500 r.p.m.), so resulting in low fuel consumption and noiselevel during ground waiting-time. Upstream injection had made possible a very short design ofcombustion chamber and the relighting characteristics had been found to be very satisfactory up to 30,000ft."Double-failure" philosophy had been applied throughout the design of the Eland interconnected fuel and airscrew controls, sothat failure of any component was safeguarded by a primary control which was backed up by a further control safeguardingagainst failure of both the component and the primary safeguard. The basic control system was of the hydro-mechanical type andwas so designed that the pilot had complete control of the engine from a single lever. Once set to the desired position, no trimmingof this lever was necessary, since any change of flight condition was compensated for automatically. A NEW BOMBING-RANGE LAUNCH FOR THE R.A.F. "COLLOWING an "off-the-drawing-board" order for six new•*- launches, John I. Thornycroft and Co., Ltd., have completed the first of a new class of 43ft range-safety launches for the R.A.F.Powered by two Rolls-Royce C6. SFLM water-cooled marine diesel engines delivering 190 h.p. each, the new craft can make20 kt and has a range of 200 n.m. Manoeuvrability, good fdl= round view for the coxswain and ease of handling have all beenprovided to a marked extent; in addition, there are separate galley and radio operator's compartments, toilet, and full airconditioning and deck insulation for both tropical and arctic operation. An auxiliary air-cooled diesel engine drives a stand-bygenerator for services and communications. The beam is 12ft 6in and draught 4ft. The hard-chine hull, which is planked with a double skin ofteak, is so designed that it can be hauled up on a level slipway without special cradles. A number of items of equipment havebeen standardized as far as possible with those of other launches in service. Normal duties of the craft will be the supervision and servicingof practice bombing ranges at sea, for which purpose a two-ton capacity towing hook is fitted. Air/sea rescue is, however, alsowithin the boat's capabilities and provision is made for the carriage of standard R.A.F. rescue equipment, four stretcher cases or atotal of thirty passengers. Handling characteristics are demonstrated in Chelsea Reach prior to delivery of the first of six of the new launches to the R.A.F. TWO BRISTOL RETIREMENTS TWO members of the Bristol Aeroplane Company's staff withnearly seventy years' service between them have just retired. They are Mr. F. W. Whitehead, F.R.Ae.S., M.I.Mech.E.,M.I.P.E., chief production engineer of the engine division, and Mr. C. W. Tinson, F.R.Ae.S., M.I.Ae.E., sales liaison engineerof the aircraft division. Mr. Whitehead Mr. Tinson Mr. Whitehead began his career early in the century in thetoolroom of Coventry Ordnance, followed by a period as jig and tool draughtsman at Daimler. His first task on joining theBristol company in 1921 was the preparation of the original Jupiter engines for production, and a major part of the enginedivision as it is today was planned by him. In 1939 he was responsible for procuring from America the machine tools neededfor wartime production of Bristol engines. His name appears on many of the company's patents, and he introduced the lost-waxcasting process and the machining of cylinder heads, with their close-pitched fins, from solid forgings; he also played a majorpart in making possible the production of Bristol sleeve-valve engines. Mr. Tinson was engaged on aircraft construction as early as1911, assisting in the design and manufacture of a metal wing for a Bleriot monoplane. Shortly afterwards he joined the Britishand Colonial Aeroplane Co.—Bristol's predecessors—under the late Frank Barnwell, and during the following years assisted himin the design of several famous types, including the Bristol Scout. After holding further posts, in the Admiralty Air Departmentand the industry, he rejoined Bristol in 1922 and became chief draughtsman—an appointment he held for ten years. In May1936 Mr. Tinson was made one of four senior technical assistants, and three years later became test flight development engineer. Hereturned to the design side early in 1941, and after the war was appointed sales liaison engineer.
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