Noise-minimal approach trajectories in mountainous areas

The optimization of approach trajectories with respect to noise taking into account visibility aspects in mountainous areas is considered. A simulation model based on the BADA database published by EUROCONTROL is utilized for this purpose. For the computation of the noise cost function, a noise model based on the INM/ANP database is used. The model is specifically tailored for gradient-based trajectory optimization tasks and allows computing time histories of A-weighted sound pressure levels. The commonly used noise metrics - "sound exposure level" (L_AE) and "maximum level" (L_Amax) - can be determined from the sound pressure level histories. The cost function is either based directly on L_Amax or on the "the number of awakenings" as a function of L_AE. For the optimization in mountainous areas, the visibility between the noise emitter (i.e. the aircraft) and the receiver is taken into account via a visibility surface concept. Noise-minimal approach trajectories are computed for two different airports in mountainous areas, namely Bolzano in Italy and Innsbruck in Austria.