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Aviation History
1954
1954 - 0985.PDF
FLIGHT, 9 April 1954 , 449 Aero Engines 1954 exit cowl and fan cooling for low airspeeds. In B.E.A. service the 661 has averaged 14,000 hr per feathering, a good figure for a new installation, and the A.R.B. has just approved a 1,000 hr overhaul period. Military and naval Centaurus con tinue to give good service. Proteus. The original Proteus prototype ran in February 1947, and retained the Theseus reverse-flow, free-turbine layout, the latter feature making for great flexibility and ease of control. From the basic Proteus was developed the Coupled Proteus, used in the Princess flying boat, which is illustrated here to give an idea of the performance and layout of the first form of the engine. The Coupled Proteus power sections were geared to a single shaft from which a contra gearbox supplied power to a contra-rotating airscrew; this is in contrast to the layout of the Double Mamba. In 1950 the Proteus was completely redesigned, and made more compact, lighter and more efficient and powerful. The centri fugal compressor was brought up against the axial, the mass flow and pressure ratio were increased, and the power turbine was given two stages; in addition, fully shrouded blading was incorporated on the first three turbine stages. The first 15 Britannias (Series 100) have the Proteus 705, of this revised type. But the performance of this engine has proved so encouraging that a further development is in hand to permit operation at still higher power. The new engine, the Proteus 755, will run at 12,000 compressor r.p.m. and, with increased gas tempera tures, will provide 3,650 s.h.p. +1,320 lb thrust, or 4,150 e.s.h.p. Proteus 705s are already running at this rating on development tests. All Proteus are fully protected against ice, and are also equipped to supply bleed air from the compressor for cabin pressure and de-icing. An Ultra electric control system is fitted to permit ex tended cruising at precisely controlled compressor speed, inde pendent of airspeed and altitude; this unit also controls accelera tion and prevents excessive jet-pipe temperature. Auto-synchro nization is standard on the Britannia. A safety device has also been developed to prevent overspeeding of the power turbine when torquemeter pressure falls below a given limit. Altogether, the Proteus is a very valuable engine; present flying is on a 200 hr basis, but this will rise rapidly as experience is gained. New Turboprop. For what it is worth, we record an Ameri can report to the effect that a new Bristol turboprop is on the way. A two-spool engine roughly half the size of the Olympus, it is stated to be throttled to 4,000 h.p. at sea level so that this take-off power can be utilized under any condition of altitude or temperature; not until 15,000ft is reached does the power begin to fall, and the full-throttle curve then gives a power of 2,900 h.p. at 36,000ft. The report links the engine with a "Super Britannia." Bristol's engine division are not prepared to com ment on this report. Olympus. First of the production Bristol turbojets, the Olympus was the first two-spool engine in the world, antedating the Pratt and Whitney J57 by some two years. It is probably unmatched in its stability, response to control changes, general behaviour and re-lighting at extreme altitude (the Olympus has been regularly tested at over 60,000ft) and, for an engine of its size and weight, performance and economy. According to American reports, the compressor power has been split between only two turbines, resulting in the low- and high-pressure com pressors having six and eight stages, respectively. The extremely compact combustion chamber is reported to be a stainless-steel drum housing 10 cans and supplied with fuel from 10 duplex burners. The starter drives the high-pressure assembly. The thrust rating quoted was established nearly two years ago, and the company have hardly been standing still in the meanwhile. The Olympus is in super-priority production for the Vulcan, and is also mentioned under the American Curtiss Wright company. Orpheus. Late last year work began on a new turbojet, designed to provide an extremely modern, efficient and compact source of about 5,000 lb thrust. Its development is proceeding unusually rapidly and there is every indication that it will be widely used in a variety of fighters, trainers and, possibly, missiles. The first announced application is the Folland Gnat. It should be stressed that this engine is in no sense a development of the Saturn. Saturn. A small axial turbojet of some 3,800 lb. thrust. Some Saturns were built and run over the past few years, but the engine has been abandoned and is not representative of current Bristol practice. de Havilland. The de Havilland Engine Co., Ltd., Leaves- den Airfield, near Watford, Herts. Ever since 1927, when the first Gipsy engine appeared, de Havilland piston engines have been steadily developed, to a common basic pattern and, in fact, by a team led by the same men who designed the first Gipsy. Bristol Centaurus 661 18-cylinder, two-row, sleeve-valve, air-cooled radial geared and fitted with two-speed supercharger. Bore, 5.7Sin; stroke, 7in; swept volume, 3,270 cu in (53.6 litres); diameter, S6.4in; length, 74in; dry weight, 3,400 lb; maximum power, 2,705 b.h.p. at 2,800 r.p.m. at 13.8 lb boost at 4,000ft. Bristol Proteus 705 free-turbine reverse-flow turboprop. Compressor has 12 axial and one centrifugal stage, driven by two-stage turbine. Airscrew gearbox (0.09:1) driven by separate two-stage turbine. Eight, reverse-flow combustion chambers. Diameter, 39.5in; length, 113in; dry weight, 2,850 lb; mass flow, 44 lb/sec; pressure ratio, 7.2:1; maximum power, 3,320 s.h.p. plus 1,200 lb thrust, giving 3,780 e.s.h.p., at 11,700 compressor r.p.m.; cruising s.f.c. at 35,000ft, 0.495 lb/hr/e.s.h.p. Bristol Coupled Proteus 610, consisting of two Proteus 600-series power sections geared to a common contra-gearbox. Width, 83.2in; height, 41.4in; length, 179.8in; dry weight, 7,730 lb; maximum power, derated to 5,000 s.h.p. plus 1,660 lb thrust, giving 5,640 e.s.h.p. at 10,000 compressor r.p.m. Note .-This engine is included principally for historical interest, and is of early conception. Bristol Olympus BOI.1 two-spool turbojet. The compressor consists of two independent axial units driven by separate turbines. An annular combustion chamber is fitted. Diameter, 40in; length, 124in; dry weight, 3,520 lb; maximum power for publication, 9,750 lb thrust, with s.f.c. of 0.766 Ib/hr/lb.
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