New reference day atmosphere for analyses of quiet supersonic overflight

Abstract

New reference day atmospheric conditions have been defined for future supersonic aircraft en route noise certification procedures. As field measurements are acquired, in a variety of atmospheric conditions, it is important to relate those measurements back to a common reference atmosphere to provide uniformity in method across applicants for noise certification. Because of the long propagation distances involved between the aircraft flight altitude and the ground, en route noise certification measurements can be substantially affected by the atmosphere. Properties, such as pressure, density, temperature, humidity, and winds, vary with altitude. Therefore, the definition of reference atmospheric profiles as a function of altitude are needed instead of the coarse layered atmosphere and homogeneous humidity used in subsonic aircraft landing and takeoff noise certification. Ground loudness levels from overflight of a quiet supersonic demonstrator concept, calculated with atmospheric data from sites across the world, were compared with the results from several candidate reference atmospheres to identify a reference that would minimize the required adjustment to certification test measurements. The existing ICAO 7488/3 profiles for temperature and pressure, combined with a modified ISO 5878 humidity profile, were found to offer the best results.