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Aviation History
1959
1959 - 0447.PDF
FLIGHT, 13 February 1959 13 This drawim production I outstanding, which is no ORPHEUS... advantage of improved techniques and, in particular, to avoidthe aerodynamic overloading of the high-pressure end which slightly marred the performance of the BOr.l compressor. Inaddition, the cooling-air supply to the turbine stators was slightly reduced, resulting in a useful reduction in specific fuel consump-tion. The difference between the BOr.2 (Mk 700 series) and BOr.3 (Mk 800 series) is of an even more minor nature. Asalready noted the NATO engine incorporates the larger fuel pump, and exists in several forms to suit the various installationrequirements of the three NATO machines; and, owing to the diminutive size of the Gnat, the BOr.2 or Mk 701 has a slightlyslimmer wheelcase and more compact accessories. During 1957 the final development to the 4,850 lb type testtook place on the various types of BOr.3 specified for the NATO programme. The programme was slightly delayed by the non-delivery of certain items—such as the Labinal D.C. generator and ORPHEUS SUB-TYPES Rating Initial BOr.1BOr.2 BOr.3 BOr.3 BOr.3/5 BOr.4 BOr.11 BOr.12BO.12SR Fan Mk _ 701 801803 810 100 — Thrust (Ib) 3.28S •4,050 4,520 4,8505.000 4,850 4,230 5.760 6.810 8,000 > Weight (Ib) 760 750790 825 825 915 890 985 1.100 1,100 i Length (in) 73.0 73.073.0 75.45 75.45 75.45 75.5 79.27 79.27 82.7 i Type- test 1955 1956 1956 1957 1958 1957 — Remarks For Gnat, Lucas GBB fuel pump D-size fuel pumpStandard NATO engine All-weather, extra acces- sories, 5,100 Ib in produc- tion versionAll-weathjer, derated Simple reheat (afterburner) Messier hydraulic pump—which were designed in France for thispowerplant, but the final type test was successfully completed in May 1957, more than a month ahead of schedule. The competingaircraft for the NATO strike order were evaluated in a series of technical trials at the C.E.V. Bretigny, near Paris, duringSeptember and October 1957. Present at these trials were tht- Fiat G.91, Dassault Etendard VI and Breguet 1001 Taon,together with the Atar-powered Sud Baroudeur and Dassault Etendard IV. Apart from the Baroudeur, these aircraft were all relativelyuntried prototypes, and it is therefore particularly commendable that serviceability was exceedingly high throughout. Accordingto Bristol "the primary inspection [of the engine] was found 10 take less than 30 min . . . the intermediate inspection was foundto take 1 hr . . . the minor inspection took approximately 4 hr. All these times may be expected to be reduced with increasingexperience on the part of the maintenance personnel. ... An engine in one of the aircraft taking part was changed in anelapsed time of 44 min." Throughout the three weeks of the trials each Orpheus-powered aircraft averaged more than twoflights per day. Winner of the contest was announced as the Fiat G.91; and,probably as a palliative to the French aircraft industry, it was stated that a developed version of the Taon would be producedwith the BOr.l2 engine (described later) for use as a "second- generation" machine from 1961 onwards. Current orders for theG.91 appear to total at least 100 aircraft; 25 development aircraft have been built, batches of 50 are believed to have been orderedby Italy and Germany, and the United States have stated their willingness to duplicate NATO orders in order to provide aircraftfor such countries as Greece and Turkey. In order to provide a continental source of engines, Fiat SpA. signed an agreement fortechnical collaboration with Bristol Aero-Engines in November 1955, and under the terms of this document the Orpheus will bemanufactured in Italy by Fiat should the number required justify
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