FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1959
1959 - 0448.PDF
221 BRISTOL ORPHEUS BOr.3 Mk 803 I by Bristol Siddeley Engines, depicts the standard Orpheus turbojet now in bulk ight tactical tighter and strike aircraft. The inherent simplicity of the engine is iesulted in the rapid achievement of a standard of reliability and ease of repair ched only after several years of intensive operation. Other types of Orpheus tie bleed-air de-icing and have different accessory configurations the expenditure on tooling. It is also appropriate to note that for many years SNECMA have been the French licensees of Bristol engines, and this agreement would permit them to manufacture the Orpheus should this be necessary. Licence negotiations have also been opened with B.M.W., a world-famous West German company. In the U.S.A. a licence to manufacture the Orpheus as the TJ-37 is held by the Wright Aeronautical division of the Curtiss-Wright Corpn. While the firm market for the Orpheus was materializing for the NATO strike machines, the enterprise of Folland Aircraft was being rewarded by increasing foreign interest in the Gnat. The first, and most important, order to be received was that from the Indian Government, who in September 1956 signed a con- tract for 25 Gnat Mk Is, supplied from Folland, together with pans for a further 15 for assembly by Hindustan Aircraft (leading to an eventual all-Indian machine). At the same time the courageous step was taken of establishing a factory at Bangalore for the manufacture of the Orpheus. This was the first decision to manufacture a gas-turbine in non-Communist Asia. The engines, which should begin to appear this year, will be employed initially in Gnats constructed wholly by Hindustan Aircraft, but the advanced BOr.lZ may later go into production for an indigenous fighter (as described later). Second country to adopt the Gnat was Finland. Late in 1956 the Finnish Air Force decided to purchase twelve Gnat Mk Is (which have been delivered) and plans are in hand to manufacture the Gnat airframe in Finland. For this purpose Bristol-built engines will be supplied initially, but Finland may decide to make the engine under licence. Last summer two Gnat Mk Is were delivered to Yugoslavia for evaluation, and the type may be adopted—and possibly manufactured—by that country. Today the standard production NATO engine is the Orpheus 803. This differs from the 801 chiefly in having several very minor improvements, such as blade-polishing, which have com- bined to raise the rating to 5,000 lb. Other data appear on the KIT TO 1 intake rubber Mating ring 2 Intake pitot 3 Starter breeches 4 Gas feed pipe 5 Turbo-itartar4 Shaft extension far front bear- ing and accessory drive 7 Fourth-stag* air to interior ofcompressor and shaft • Duplex burners locate frontends of flame tubes • Turbine stators (nozzle guide OKAWINO vanes) integral with flametubes in groups of nine 10 Stator sliced through to showhollow wrapped construction 11 Construction permits axial andradial float without gas leakage 12 Cooling-air pipe for rear bear-ing with central Off feed 13 Combined control unit14 Lucas GD fuel pump 15 Fixed inlet guide vanesIt Magnesium-xirconium coat in- take tinted panel at the foot of this column. Total running time for engines of BOr.3 standard now amounts to some 15,000 hr. Engines are being sampled to confirm an initial hie with user squadrons of 150 hr, and this figure should soon be increased. The corresponding time for the Mk 701 (BOr.2) of the Gnat Mk 1 is 200 hr. Although initially designed strictly for combat purposes, the simplicity and reliability of the Orpheus have made it an attrac- tive powerplant for trainers. Most important of the trainer engines is the BOr.4, which was announced early in 1957 as the powerplant of the forthcoming Gnat T.I for the Royal Air Force. Although almost identical to the BOr.2/3, the trainer engine has a turbine of increased size and a rating of only 4,230 lb. The resultant reduced turbine inlet temperature and compressor speed gives lower specific fuel consumption and will almost certainly permit the attainment of an exceptional overhaul life, extended components-lives and consequent low-cost operation. The BOr.4 is the standard engine for the Fuji TIF-2 transonic trainer now under development for the Japanese Air Self-defence Force. As an alternative powerplant it is available for the North American Model 249 (T2J-1) naval trainer. Although operating economy was not a dominant factor in the engine's basic design, the specific fuel consumption of the Orpheus is by no means uncompetitive with other engines in its class and a commercial version—with different accessories, steel first-stage compressor rotor blading and full de-icing— has already been planned for light transport aircraft. The first machine in this category to use the Orpheus was the Lockheed Jetstar, initially planned to meet the U.S. Air Force UCX require- ment for a crew-readiness trainer and executive transport. This specification called for four engines, but the non-availability of American powerplants caused Lockheed to approach Bristol, and the fitting of two relatively low-powered Orpheus—supplied by Bristol's American licensee as the Wright TJ-37—permitted the first prototype to fly on September 4, 1957. So outstanding was the performance of these engines, and of the 4,850/5,100 Ib-thrust Orpheus 810s which were later fitted, that similar powerplants were installed in the second prototype and a twin-Orpheus production version was also planned. In a recent paper on the Jetstar, Clarence L. "Kelly" Johnson, Lockheed's v-p. for advanced development projects, said: "These Orpheus engines . . . have been the best engines the writer has ever used in a prototype aircraft. They were and are so good that it was decided at an early date to make all Jetstars from serial number two up capable of using two. Orpheus engines [as an alternative to four American units]. The Orpheus version . . . is fully competitive in performance (except with one engine out) and will be offered to those who want its lower cost, simplicity and—at least for some time—reliability." Rather larger transports have now been developed around the engine. Three important British projects are the Hunting H-107 (two Orpheus), the Handley Page H.P.I 13 (two Orpheus pro- viding propulsion and shaft power to blowers for boundary-layer control) and the Bristol 205 (a 58-seat airliner employing four Orpheus or two more powerful engines). Most of the aircraft so far mentioned employ engines of essen- tially BOr.3 type, with a rating of either 4,850 Ib-thrust (Mk 801) or 5,000 lb thrust (Mk 803). The essential features of these extremely simple engines can be deduced from the cutaway draw- ing, but a few words of amplification are necessary. Owing to its modest length and considerable rigidity, the main rotating assembly is supported in only two bearings, a ball thrust bearing being mounted ahead of the compressor and a roller bearing being situated behind the turbine. The compressor rotor ORPHEUS MK M3Single-shaft turbojet. Fixed intake geometry, seven-stage axial com- pressor driven by single-stage turbine, can-annular combustion chamberwith seven flame tubes and burners and two igniter plugs, fixed exhaust system, shaft drives to fuel pump end accessories and provision forbleeding air. Overall diameter (common to all Orpheus), 32.4in; length from intakeflange to exhaust cone, 75.45m; equipped dry weight, 825 Ib; maximum rating, 5,000 Ib dry thrust at 10,000 r.p.m. with mass flow of 84 Ib/iec,pressure ratio of 4.4:1 and specific fuel consumption of 1.06.
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
