MACH 03 ISA 10%C 6…40H公2必 DECREASING MOISE SdB ITERVLS- 名Edit时 SCALED 595 心老 62 X7a北RFLOW RELA公和PS53 Fig 6. AST Take-off (Sideline)Noise-Four Fig 8. Payload Total Airflow and Noise Engines,2310 ft Slant Range Comparison 175 ALTITUDE Integrated Aircraft/Engine Study POUR ENGINE FREE FIELD .Whilst the mission fuel plus powerplant weight studies outlined above can give the relative merits of self-consistent engine proposals,for accurate assessments there is no substitute for a combined aircraft/ engine study where the aircraft design can be modified and optimised in accordance with the characteristics of the powerplants, which can also be tailored to the specific aircraft. 25 As mentioned earlier,British Aerospace have been conducting such studies 20 EPNdB 30 as part of their contribution to the work +©% of the ICAO Parametric Study sub-group,and 2时 some preliminary results have been published in Reference 5. TAM NET7HRT=CO他E4落T包) The British Aerospace project assessment programme used for these studies can handle Fig 7.AST Cutback (Flyover)Noise a range of aircraft geometries,mission ranges,passenger payloads and engine Iturning up the tapt on each engine of the designs. Noise at each of three measuring family. The increased cruise thrust capa- points defined by ICAO 1971 Annex 16,based bility gives a smaller engine,but it on measured Concorde noise levels,is calcu- should be noted that the transonic regime lated, The noise calculations are in the will require a proportionately higher TET course of being checked by methods proposed increase to give the thrust. If this is by the ICAO noise sub-group,and the noise not practical,some reheat may be required scale has been omitted,l0dB bandwidth and the benefit of increased TET will be intervals being shown on the curves to indi- eroded,Furthermore,it must be remembered cate trends.No special silencing means, that the benefits of increased TET can also apart from the use of acoustic liners,has be eroded by a higher replacement cost for been assumed for these curves. hot end parts. Figures 9 and 10 reproduced from Reference 5 show the results of the cal- Figure 8 also shows the effect of changing the weight fraction of the in- culations for fixed range and fixed payload takes,nacelles,and secondary nozzles of respectively for the engines discussed above. The engines are sized to the cruise the datum engine powerplant from the thrust requirement of each aircraft,and Concorde value to 0,6 of the Concorde reheat boost is assumed for take-off,where value,which would be more appropriate to necessary.As expected,the lower noise second generation axisymmetric pods. The levels require higher bypass ratios,and penalty for increased mass flow is result in increasing gross weight for a diminished.However,Figure 8 ignores given range and mission, installation loss,(eg skin friction etc) which will tend to offset this trend,as is A very significant feature of these shown in Figure 3.It should be noted that curves is how the lower bound tends to if this change in datum weight fraction become vertical for a given range and could be achieved without any structural or payload.Thus there is a minimum noise other weight penalty,an improvement in level that cannot be bettered at a given payload of 27%would be obtained. level of technology. 6Fig 6. AST Take-off (Sideline) Noise -Four Engines, 2310 ft Slant Range a. W6,NE FEE WCLD N75 AL77WDE Fig 7. AST Cutback (Flyover) Noise 'turning up the zap' on each engine of the family. The increased cruise thrust capa￾bility gives a smaller engine, but it should be noted that the transonic regime will require a proportionately higher TET increase to give the thrust. If this is not practical, some reheat may be required and the benefit of increased TET will be eroded. Furthermore, it must be remembered that the benefits of increased TET can also be eroded by a higher replacement cost for hot end parts. Figure 8 also showsthe effect of changing the weight fraction of the in￾takes, nacelles, and secondary nozzles of the engine powerplant from the .Concorde value to 0.6 of the Concorde value, which would be more appropriate to second generation axisymmetric pods. The penalty for increased mass flow is diminished. However, Figure 8 ignores installation loss, (eg skin friction etc) which will tend to offset this trend, as is shown in Figure 3. It should be noted that if this change in datum weight fraction could be achieved without any structural or other weight penalty, an improvement in payload of 27% would be obtained. Fig 8. Payload Total Airflow and Noise Comparison Intearated Aircraft/Enqine Studv .Whilst the mission fuel plus powerplant weight studies outlined above can give the relative merits of self-consistent engine proposals, for accurate assessments there is no substitute for a combined aircraft/ engine study where the aircraft design can be modified and optimised in accordance with the characteristics of the powerplants, which can also be tailored to the specific aircraft. As mentioned earlier, British Aerospace have been conducting such studies as part of their contribution to the work of the ICAO Parametric Study sub-group, and some preliminary results have been published in Reference 5. ~ The British Aerospace project assessment programme used for these studies can handle a range of aircraft geometries, mission ranges, passenger payloads and engine designs., Noise at each of three measuring points defined by ICAO 1971 Annex 16, ba~sed on measured Concorde noise levels, is calcu￾lated. The noise calculations are in the course of being checked by methods proposed by the ICAO noise sub-group, and the noise scale has been omitted, lOdB bandwidth intervals being shown on the curves to indi￾cate trends. No special silencing means, apart from the use of acoustic liners, has been assumed for these curves. Reference 5 show the results of the cal￾culations for fixed range and fixed payload respectively for the engines discussed above. The engines are sized to the cruise thrust requirement of each aircraft, and I-eheat boost is assumed for take-off,where necessary. As expected, the lower noise levels require higher bypass ratios, and result in increasing gross weight for a given range and mission. Figures9and 10 reproduced from A very significant feature of these curves is how the lower bound tends to become vertical for a given range and level that cannot be bettered at a given level of technology. payload. Thus there is a minimum noise \