The new EU helicopter noise model NORAH

To support the monitoring activities required by the European Environmental Noise Directive (END) as well as ICAO noise standard setting, an adequate noise modelling capability is required that encompasses all types of aircraft, including rotorcraft. However, the international guidance to model aircraft noise such as ICAO Doc 9911 and ECAC Doc 29 is limited to fixed-wing aircraft, thus not covering rotorcraft. The interim approach in the Environmental Noise Directive (END) is to handle helicopters as a fixed-wing aircraft. Although this assumption has been considered to be acceptable when used at macroscopic level, it lacks in robustness when applied to the assessment of airport noise or other urban noise. A more robust modelling method, better accounting for the specific noise characteristics of helicopters, is therefore required.