How to satisfy the takeoff noise requirements for a supersonic transport

Abstract

The noise during takeoff of a supersonic transport is calculated for the flyover and the lateral reference noise measurement points defined by ICAO Annex 16. Only the contribution of jet mixing noise is considered. The influences of the following parameters are considered: jet speed, aircraft weight, aircraft wing loading, aircraft lift-to-drag ratio, and the amount of power cutback after takeoff. The influence of the takeoff procedure is also studied. It is shown that jet speed has the largest influence of all parameters and that values of about 400 m/s or less are required to satisfy the noise limits that are currently valid for subsonic aircraft. Such low jet speeds can be achieved by choosing large engine bypass ratios or by employing ejector mixers with large nozzle exit diameters. The first solution may be difficult to realize technically for a supersonic transport, the second solution requires that the mixer can be fully retracted, which may be impossible because of its size.