Advancements in Technology The United Kingdom study is being under- taken by British Aerospace (Filton and In Reference 1 the authors have reviewed Weybridge)with engine data supplied by the application of advancements in tech Rolls-Royce.In this study British nology to the performance improvement and Aerospace are evaluating operating costs noise reduction of supersonic transport and noise levels of a family of aircraft. aircraft.It is shown how performance The study covers variations in: requirements for subsonic aircraft have led to the adoption of low specific thrust, Range high bypass ratio engines,with a consequent Number of Passengers reduction in jet velocities and hence in Wing Area airport noise.It is also shown that this Aspect Ratio is not the case for supersonic cruise air- Engine Bypass Ratio craft where increasing bypass ratio beyond a certain value will degrade the mission Class II technology is being assumed,with performance (Figure 3). For such aircraft a cruise Mach No of 2.0. the requirements of performance and noise are conflicting. Engine Studies The various means of improving perfor- To provide the required engine data a mance and reducing noise were discussed in preliminary design study and part load per- some detail,in the Reference,and the con- formance estimate was made of four mixed straints to their application described. flow turbofan engines.These were two spool engines with the fan on the LP spool, In the next few sections the studies and the remainder of the core compression that have recently been made of engines for being carried by the HP spool,which was the next generation of supersonic trans- envisaged as an Olympus 593 HP spool with ports are described.These studies have some extra stages of compression. As is assumed a defined advancement in the level the case for the olympus 593,sufficient of technology available. nozzle area variation is provided to enable the appropriate LP spool rpm and TET ICAO Studies to be obtained simultaneously over a large range of flight conditions.This is an In November 1976 the ICAO Committee on essential feature of a supersonic cruise Aircraft Noise,CAN 5,set up Working engine. The ground rules for the study are Group E with the task of reporting to the given in Table 1,and some leading par- Committee (CAN 6)in late 1978 on recom- ticulars of the resulting engines are given mendations for SST noise regulations and in Table 2. guide lines.France,UK,US and USSR (as the countries who have a direct interest in SST development)have representation rights Cruise Design Point on the Working Group. Same core flow and overall pressure ratio as olympus 593 As part of their programme Working 16000K TET Group E set up a Parametric Study sub-group with the somewhat formidable task of evalu- Chosen bypass ratio ating the relationship between the noise Equal Mach Number and static pressure at mixing plane level and the operating cost of a supersonic (leads transport.Each country was to perform its to low operating point on fan chic) own studies,and report to the sub-group who would correlate the studies and report to Take-off Operation the Working Group,To assist in the cor- Cruise to take-off fan rpm relation simi- relation further sub-groups were set up, lar to olympus 593 LP compressor one on noise prediction,with the aim of 17000K TET achieving a common prediction method,and Highest safe operating point on fan chic another on economics having the task of Bypass ratio and overall pressure ratio agreeing a common method for cost follow estimation. NB Improved cruise performance is obtained Working Group E,when initiating the by allowing high operating point on fan Parametric Studies,made a forecast of the chic with unequal mixing Mach numbers timescale in which it expected the various technologies would be available for com- mencing a serious design.The technologies Table 1.-Mixed Turbofan Family m Engines were classified as: A,B,C.D.Ground Rules set at the Beginning of the Study Class I 1977-1980 Class II 1980-1985 Evident from Table 2 is the significant Class III Beyond 1985 reduction in bypass ratio from cruise to take-off which has resulted from the use The detailed classification of the various of variable bypass and optimising the cycle technologies is given by Foster in Table I matching during the course of the study. of Reference 2. In fact engine A is virtually a pure jet at 3Advancements in Technoloqy In Reference 1 the authors have reviewed the application of advancements in tech￾nology to the performance improvement and noise reduction of supersonic transport requirements for subsonic aircraft have led to the adoption of low specific thrust, high bypass ratio engines, with a consequent reduction in jet velocities and hence in airport noise. It is also shown that this is not the case for supersonic cruise air￾craft where increasing bypass ratio beyond a certain value will degrade the mission performance (Figure 3). For such aircraft the requirements of performance and noise are conflicting. - aircraft. It is shown how performance The various means of improving perfor￾mance and reducing noise were discussed in some detail, in the Reference, and the con￾straints to their application described. In the next few sections the studies that have recently been made of engines for the next generation of supersonic trans￾ports are described. These studies have assumed a defined advancement in the level of technology available. ICAO Studies In November 1976 the ICAO Committee on Aircraft Noise, CAN 5, set up Working Group E with the task of reporting to the Committee (CAN 6) in late 1978 on recom- mendations for SST noise regulations and the countries who have a direct interest in SST development) have representation rights on the Working Group. Y guide lines. France, UK, US and USSR (as As part of their Droaramme Workina GrouD E set UD a Parametric Studv Sub-Orom .,I with' the SomEwhat formidable task of evalu￾ating the relationship between the noise level and the operating cost of a supersonic transport. Each country was to perform its own studies, and report to the sub-group who would correlate the studies and report to the Working Group. To assist in the cor￾relation further sub-groups were set up, one on noise prediction, with the aim of achieving a common prediction method, and another on economics havino the task of ~ agreeing a common method for cost estimation. Working Group E, when initiating the Parametric Studies. made a forecast of the The United Kingdom study is being under￾taken by British Aerospace (Filton and Weybridge) with engine data supplied by Rolls-Royce. In this study British Aerospace are evaluating operating costs and noise levels of a family of aircraft. The study covers variations in: Range Number of Passengers Wing Area Aspect Ratio Engine Bypass Ratio Class I1 technology is being assumed, with a cruise Mach No of 2.0. Enaine Studies To provide the required engine data a preliminary design study and part load per￾formance estimate was made of four mixed flow turbofan engines. These were two spool engines with the fan on the LP spool, and the remainder of the core compression being carried by the HP spool, which was envisaged as an Olympus 593 HP spool with some extra stages of compression. As is the case for the Olympus 593, sufficient nozzle area variation is provided to enable the appropriate LP spool rpm and TET to be obtained simultaneously over a large range of flight conditions. This is an essential feature of a supersonic cruise engine. The ground rules for the study are qiven in Table 1. and some leadina -. Dar￾ticulars of the Gesulting engines are given in Table 2. Cruise Design Point Same core flow and overall pressure ratio as Olympus 593 16000K TET Chosen bypass ratio Equal Mach Number and static pressure at mixing plane (leads to low operating point on fan chic) Take-off ODeration Cruise to take-off fan rpm relation simi￾lar to Olympus 593 LP compressor 17000K TET Highest safe operating point on fan chic Bypass ratio and overall pressure ratio follow E Improved cruise performance is obtained by allowing high operating point on fan chic with unequal mixing Mach numbers timescale in which'it expected the various technologies would be available for com- mencing a serious design. The technologies were classified as: A. B, C, D Ground Rules set at the Table 1 - Mixed Turbofan Family - Ensines Beqinninq of the Study Class I 1977-1980 Class I1 1980-1985 Evident from Table 2 is the significant Class 111 Beyond 1985 reduction in bvDass ratio from cruise to take-off which-kas resulted from the use The detailed classification of the various of variable bypass and optimising the cycle technologies is given by Foster in Table I matchinq durinq the course of the study. of Reference 2. In fact-engine-A is vihually a pure jet at 3