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Aviation History
1962
1962 - 2066.PDF
FLIGHT International, 13 September 1962 457 reversers for civil aircraft, Rolls-Royce have many schemes for fitting variable-direction deflectors to both lift and propulsion engines to give extra control or lift respectively, and perhaps also as a means for reducing ground erosion from vertically positioned engines. On their stand, Bristol .Siddeley Engines concentrated atten tion on the vectored thrust principle for VTOL. A number of important submissions for the NATO BMR-3 strike fighter competition have been made, fitted with the 35,000-40,0001b- thrust BS.100, and on the stand were shown two nameless models probably closely representative of the Fokker/Republic D.24 Alliance and the Hawker P. 1154. Another interesting model was of a large military transport with four swivelling- nozzle engines mounted in pods under the high wing and probably very like the BAC 208 and WGA 681 for Operational Requirement 351. The only development of the basic Pegasus arrangement which can yet be mentioned is plenum-chamber burning, whereby fuel is burnt in the relatively cold air of the front nozzle to give up to 30 per cent more thrust for a slight increase in s.f.c. This system is more efficient than normal reheat because of the lower initial temperature of the by-pass air, which results in greater expansion for the amount of fuel burnt. Again, no new details were available on the BS.59 jet lift turbofan which will shortly run for the first time; or of the BS.94 swivelling nozzle version of the 7.000-10,0001b by-pass BS.75. In view of the joint BAC-Sud announcement on the super sonic airliner, speculation over 1he question of powerplant was the other important aspect of the propulsion scene. This question is perhaps even more fundamental to the companies involved than is any one of the VTOL propulsion contracts, and the eventual decision on this single giant programme is bound to have far-reaching long-term repercussions. Both United Kingdom engine manufacturing groups capable of per forming the programme have unique combinations of experi ence vital to this project, laboriously acquired over the years. The experience of one of them will be wasted by the decision. The complicated flight-profile of a supersonic airliner com- Schematic diagrams of Bristol Siddeley's supersonic civil Olympus package Production Bristol Siddeley Pegasus lift/thrust fan engines on final assembly at Patchway, Bristol plying with airfield noise limitations, restrictions on the choice of transonic acceleration point to avoid boom annoyance on the ground, coupled with the enormous range of speed and thrust requirements, pose some difficult problems for the engine designer. In order to match the powerplant as closely as possible to all phases of flight, ihe intake and nozzle must become integral parts of the powerplant. Bristol Siddeley Engines' proposal for a civil Olympus powerplant package to go beneath the wing of a supersonic airliner such as the BAC- Sud design is shown here schematically in a number of sec tioned drawings illustrating the configuration during various stages of the flight plan. In the take-off condition the effective intake area is increased by opening flaps on the lower surface, and fhe exhaust nozzle is slightly choked to give maximum thrust without reheat. During initial climb-out the engine is throttled and the nozzle opened to reduce exhaust velocity and so maintain a low noise- level in the vicinity of airports. For transonic acceleration, the intake and nozzle are positioned to give maximum thrust with reheat to achieve rapid acceleration during the climb to a sufficient altitude for minimum disturbance on Ihe ground from the sonic bang. In the supersonic cruise condition the lower intake flaps open to spill excess ram air, and the nozzle is opened to provide optimum conditions for cruise economy. The twin-spool arrangement of the Olympus allows it to operate throughout the entire speed range without the need for blow-off valves or variable-incidence blading. Boundary-layer air is ducted above the intake and engine, and re-injected at the nozzle. Bristol Siddeley's twelve years of work on ramjets for missiles has given them much valuable aerodynamic experience of the intake-design problem. The supersonic civil Olympus is derived from the version of the engine that has been under development for the TSR.2 strike/reconnaissance aircraft. Olympus engines under test with Solar variable reheat have been achieving a thrust of 33.0001b, three times that of the original production engine. Bearing in mind that the airliner will probably require thrust in the region of 30,0001b without reheat for take-off, then the civil Olympus development work will not only involve extensive engineering changes to comply with civilian regulations and requirements, but an increase in mass flow will probably mean one or two extra stages on the compressor and turbine. Air-cooled blades will be mandatory, and the company have substantial experience in this field (although Rolls-Royce would certainly consider themselves to have more). Rolls-Royce were not displaying anything of their many years' work on civil supersonic powerplants, although it was unofficially reported that their various proposals for the changing BAC-Sud designs bore the family name of RB.169. It can almost certainly be assumed that these engines have a twin-spool layout and air-cooled turbine blades—of which latter Rolls-Royce have considerable experience on a number of engine types in world-wide military and civil operation.
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