Wind tunnel measurements of the airframe noise of a high-speed civil transport

Abstract

A model-scale airframe noise test of a high-speed civil transport (HSCT) was conducted in the Boeing Low-speed Aeroacoustic Facility. The test had the following objectives: provide an estimate of HSCT airframe noise levels; identify the major HSCT airframe noise sources; and assess the accuracy of the current HSCT airframe noise predictions. The noise levels were estimated by projecting data from free-field microphones to full-scale conditions. The result was an approach level of 91 EPNdB, well below current requirements. The sources of airframe noise were identified by using a phased microphone array. The identified sources included the landing gear, the wingtips, the nacelles, and the tail. The NASA ANOPP prediction procedure was shown to be adequate for current needs, and empirical adjustments were suggested that could improve it for HSCT applications. theoretical investigations have dealt primarily with conventional subsonic airplane designs. Much less is known about the noise produced by supersonic delta wing planforms. In order to support the development of an HSCT, a better understanding of the airframe noise sources and levels is necessary. This understanding will allow for more accurate estimates of the HSCT noise levels, and will provide information for developing a low-noise HSCT airframe. The test program discussed in this paper was undertaken as a joint NASA/aircraft industry effort, with the following objectives: provide an estimate of HSCT airframe noise levels; identify the major HSCT airframe noise sources; and assess the accuracy of the current HSCT airframe noise predictions.