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Aviation History
1957
1957 - 0918.PDF
22 FLIGHT, 5 July 1957 The Orpheus BOr.3 after successful completion of the full 150-hr type test early in May. Above the compressor is the cartridge starter. PROGRESS WITH THE ORPHEUS . . . of the engine. Although the first engine was run with a six-stagecompressor, the rig tests showed that seven stages were entirely practical. The second and subsequent engines therefore incor-porated the additional stage. In order to clear engines for flight in the Gnat, an OrpheusBOr.l was submitted for an official 150-hour type-test, at the relatively low rating of 3,285 lb-thrust, within five months of thefirst run. This type-test was successfully completed on May 6, 1955, and an engine was despatched to Folland Aircraft thefollowing month. The Gnat made its first flight on July 18 in the hands of S/L. E. A. Tennant, Folland chief test pilot. Thehandling of the Orpheus received considerable praise, particularly for its rapid acceleration. Meanwhile, early in 1956, the BOr.l was type-tested at itsdesign rating of 4,050 lb. By April 1956, when over one hundred flights had been made by the Gnat, an Orpheus BOr.2 wasinstalled in an underwing pod on Bristol's Avro Ashton flying test bed in order to supplement the engine performance measure-ments. The BOr.2 is the standard engine for the Gnat. In August of the same year, the first flight of the Fiat G91lightweight tactical fighter took place at Casella Torinese near Turin. The G91 was the first to fly of the three lightweight strikeaircraft ordered for evaluation by SHAPE, the other two being the Dassault Etendard VI and the Breguet 1001 Taon. Theseaircraft were built to a specification issued by SHAPE, the philosophy behind which was concerned with the provision oflarge numbers of light and mobile aircraft for the support of ground troops in Europe. The requirement envisaged that theseaircraft would have a first-class flight performance at low altitudes but with limited range and armament, and that they would avoiddestruction on the ground through exceptional mobility which would be ensured by operating from grass fields and semi-pre-pared strips. In this way immense concrete aerodromes would be rendered unnecessary and the reduced need for fuel, ammunitionand spares would simplify the logistics problem. The Orpheus BOr.2, for the Folland Gnat, was type-tested atits full rating of 4,520 lb in November 1956. Here it is convenient to mention how the various Marks of Orpheus differ from oneanother. The BOr.2 is almost identical with the BOr.l except for aerodynamic improvements which give it the higher take-off thrust. The BOr.3 is aerodynamically the same as the BOr.2,but has a larger wheelcase carrying a fuel pump of increased size, and increased-capacity accessories which were particular require-ments of the European lightweight strike machines. The larger fuel pump gives the BOr.3 an increased thrust at take-off and atlow altitudes, to meet the specialized needs of support aircraft; above heights of the order of 10,000 feet (the exact height depend-ing on forward speed) the thrusts delivered by the BOr.2 and BOr.3 are identical. By the end of February 1957 the BOr.3 was cleared for flight,and engines of this type were delivered to Geneiale Aeronautique Marcel Dassault at Saint-Cloud, near Paris, and to Fiat SpA atTurin, for installation respectively in the Etendard VI and the G91. The Etendard VI flew for the first time on March 15,although Marcel Dassault had already obtained flight experience with the earlier Etendard IV powered by the larger Atar engine,and the Etendard II with twin Turbomeca Gabizos. The Orpheus-powered Breguet 1001 Taon is due to fly shortly,though an essentially similar aircraft known as the Breguet 1100, and powered by two Turbomeca Gabizos, was flown for the firsttime on March 31 at Istres. Powerplants for the Dassault, Breguet and Fiat machinesare all basically similar BOr.3 units, but they have individual superficial distinguishing features. The length of jet-pipe isgreatest in the Breguet 1001, shortest in the G91 and of inter- mediate length in the Etendard. On the Fiat and Dassault machinesthe fuel filter is on the left side of the compressor, whereas it is directly below the engine on the Breguet. The Fiat engine hasa single hydraulic pump on the rear face of the port side of the wheelcase, supplied with the powerplant; for the French aircraftthe Orpheus are delivered without such units and the airframe firms add twin hydraulic pumps on the front and rear faces ofthe same wheelcase. A particular feature of the Etendard units is that they are run into the fuselage on small rollers carried onbrackets on the compressor casing. The prospect of using afterburning in advanced versions of theOrpheus has already been mentioned, and this feature is most likely to find application in transonic or supersonic militarymachines. The Orpheus has already been run with Bristol Simplified Reheat,* the degree of thrust augmentation in this casebeing approximately 15 per cent. A development which has civil as well as military applications,however, is thrust reversal; a thrust reversal system has already been tested on the Orpheus and has been successfully operatedup to a reverse thrust of 1,500 lb. This would undoubtedly give a considerable braking effect, and would enable the ground rollon landing to be substantially reduced while avoiding undue wear and tear on the tyres and brakes of the aircraft. Orpheus thrust-reverse is now almost fully developed. An unusual application for a jet engine is as a thrust booster forheavily-loaded piston-engined transports, examples of this being the application of small turbojets to such twin-engined machinesas the Packet, Provider and Noratlas. The Orpheus, by reason of its excellent thrust/weight ratio and relatively low specificfuel consumption, would be eminently suitable for boosting a large aircraft in this manner. Another application made possible by the excellent thrust/weight ratio is for the provision of vertical thrust in high-speed VTOL aircraft. In this application the engines might be pivoted;alternatively the lift-engines would be used only for take-off and initial climb and the final stages of descent and landing, whilehorizontally-mounted turbojets would be used for normal flight. The Orpheus has already been selected for a number of veryadvanced projects in various countries; those which may be revealed include the Aerfer Leone, a mixed-power interceptordesigned by Ing. Stefanuti in Italy; the Hispano HA-300, designed under the direction of Professor Willi Messerschmitt in Spain;and the Japanese Fuji TIF-1 trainer. *Bristol Simplified Reheat, or B.S.R.: a neat and rudimentary form ofafterburning in which fuel is injected from behind the engine tailcone, used in conjunction with a fixed-area propelling nozzle. Watching the type-test are Mr. J. H. Dale, Orpheus chief develop- ment engineer, and Dr. S. G. Hooker, director and chief engineer.
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