Abstract
Meeting the Silent Aircraft Initiative (SAI) design goal during take -off drives the aircraft and engine design towards a multi -engine configuration with low specific thrust and high cruise altitude. These design choices enable the engine fan to operat e at part -speed during take -off, significantly increasing the benefit of a variable area nozzle in relation to fan and jet source noise reduction. By optimizing t he thrust and climb gradient for low jet noise during the entire take -off it is possible to re duce jet noise to the SAI target of 60 dBA . Using this approach overall aircraft noise meets the SAI target at the sideline location but is approximately 5dB A above the target at the flyover location. By considering turbomachinery and airframe noise source s when optimizing thrust and climb gradient it is possible to match the peak noise produced at all times during take -off giving an overall noise level of 62 dBA .
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