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Aviation History
1964
1964 - 1377.PDF
762 FLIGHT International, 7 May ENTERS SERVICE POWER FOR THE VC10 Development of the Rolls-Royce Conway RCo.42 "One was very conscious of the 82,0001b of thrust available" says an airline captain in an assessment (pages 756-759) of the VC10. In the following article, a Rolls-Royce engineer tells the story of the pains- taking development of the Conway RCo.42 by-pass engine which has brought this most powerful civil powerplant to its present remarkable level of performance and reliability. THE Rolls-Royce Conway RCo.42 was conceived in 1958 as alogical development of the RCo.12, which has demonstratedits reliability and low operating cost in service during the past four years in versions of the Boeing 707 and Douglas DC-8 operated by nine international airlines. Four tail-mounted RCo.42s power the VC10. The civil range of Conways stems back to 1955, when proposals were made for an engine of 15,0001b take-off thrust suitable for use in the Boeing 707 and Douglas DC-8. From this initial figure the basic RCo.10 and RCo.12 engines have been developed to a minimum take-off thrust of 18,0001b, an increase also accompanied by useful improvements in cruise s.f.c. Performance Development At the time when the first RCo.l2s were being delivered for initial flights an investigation was made into the possibilities of radically improving the performance level while at the same time retaining as many existing components as possible. The result was the engine now known as the RCo.42 and designated Conway Mk 540 for installation in the VC10. Improvement in take-off thrust and cruise s.f.c. demanded more airflow and hence a larger 1-p compressor. Scaling-up of the complete 1-p compressor of the RCo.12 was not feasible without resorting to a further 1-p turbine stage, and even then there would have been serious unbalance between the pressures of the by-pass and hot gas streams at the mixing plane. The preferred solution was to scale-up the first four stages of the seven-stage 1-p com- pressor and to scale down the last three stages to h-p compressor size, the by-pass ratio being increased from 0.3 to 0.6. This ensured the required increase in airflow without seriously increasing the 1-p shaft work and resulted in a 16 per cent increase in take-off thrust at the same turbine entry temperature and compressor delivery pressure as on the RCo.12, and a 7 per cent improvement in cruise s.f.c. The 1-p turbine was slightly increased in diameter but the whole of the h-p system was left unchanged. Work has continued to improve the RCo.42's performance still further. Compressor development has led to the replacement of the last three stages of the 1-p compressor by a four-stage unit of appreciably higher efficiency yet of the same length. Adoption of this compressor results in the RCo.43 rating, which gives 7 per cent higher take-off thrust with no increase in turbine entry tem- perature and an improvement in cruise s.f.c. RCo.43 engines will be used in the Super VC10 and also in VClOs for the RAF Transport Command. Salient performance data illustrating the development of the civil range of Conway engines are summarized in the table. Comparison with the RCo.12 As already implied, the basic principle followed in the design of the RCo.42 was to use as many RCo.12 parts as possible, so that service experience and develop- ment background could be read across. The h-p section was virtually the same as that in the RCo.12 engine, including the compressor and turbine, combustion system, internal wheelcase, Derivation of the Con- way RCo.42 from the RCo.12. The latter engine was described in detail in this journal on January 15, I960
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