Operational and conceptual measures for aircraft noise reduction
Beside the reduction of CO2 and NOx emissions, the optimisation of the aircraft noise footprint is becoming increasingly important. Naturally, take-off and landing are most relevant for the noise target definition of the International Civil Aviation Organization (ICAO). For the concept studies of the inner-city airport CentAirStation and the corresponding aircraft configuration CityBird, noise aspects are highly relevant.
To enable a preliminary assessment of noise emissions, Bauhaus Luftfahrt integrates well-proven, semi-empirical source noise models for relevant components in its aircraft design platform. The considered take-off and approach procedures defined by the ICAO yield to a cumulative noise level of the CityBird of 233 EPNdB, which is clearly below the certification limits for the year 2040. A short undercarriage and advanced, aft-mounted engines shielded by a U-tail contribute to this. Further, unswept wings with a high-lift system that runs along the whole span as well as plasma actuators enable a comparatively low approach speed of 102 knots, which reduces the noise emissions significantly.
To ensure public acceptance of a centrally located CentAirStation, inner-city noise standards have to be satisfied. Therefore, various design and operational measures can be taken. For instance, the runway on top of the building is enclosed by noise shielding barriers. Furthermore, a higher glide path angle during approach increases the distance between the noise emitter and the noise receiver. This results in a considerable reduction of urban areas, which are exposed to aircraft noise.
- Exemplary noise footprint of railways in Berlin city centre: Rail traffic and heavily frequented roads are the dominant urban noise sources and set the benchmark for an inner-city airport.
- Effects of a higher approach angle: Comparing a steep approach with 5.5° to the standard level approach, the area exposed to aircraft noise can be reduced significantly.