Noise Mitigation by Altered Aircraft Approach

Abstract

As the amount of aircraft with high by-pass ratio engines has increased, noise of departing aircraft has decreased while the noise of approaching aircraft has not decreased correspondingly. As a consequence, the need for approach noise mitigation will continuously grow.

To support the development of optimal air traffic management procedures and other noise mitigation options, quantification of available noise benefits is essential. However, current, publicly available noise prediction models rely on calculation of noise only as a function of thrust, ignoring the effects of airspeed and aircraft configuration on noise emission. Thus, they cannot be directly used to compare different approach procedures.

In this study, an improved way of using a widely known noise prediction model INM was developed. The improved way was based on an idea to divide the noise prediction process into separate calculation of airframe and engine noise. The airframe noise was calculated as a function of airspeed and only the engine noise as a function of thrust. Results were compared with measurements carried out around Helsinki-Vantaa Airport.

The developed method was applied to quantification of available noise mitigation potential at Helsinki-Vantaa for MD80 and A320 aircraft. The results of calculations explained well the scatter of measurements at long distances to touchdown. Differences of up to 6 dB were calculated for considered profiles. However, the final noise reduction potential is dependent on the performance of air traffic management and the extent on which the optimal approach procedures can be applied.

Data analysed in this study indicated that noise of an aircraft at idle power approach is rather a function of airspeed than thrust. Thus, approach noise prediction as a function of airspeed is suggested for a subject to further research.