Aircraft noise modeling of dispersed flight tracks and metrics for assessing impacts

Abstract

The implementation of Performance Based Navigation (PBN), such as Area Navigation (RNAV) and Required Navigation Performance (RNP), has led to aircraft being able to fly designed flight tracks very precisely. This has led to communities citing the concentration of aircraft along one flight track as a noise issue because of the frequent overflights above specific areas. In order to assess the impact of frequent overflights, metrics for understanding the annoyance mechanism were necessary. The metric Nx, which is a count of the number of overflights above the A-weighted maximum sound level (L[subscript A,max]) of xdB during the day and (x-10)dB during the night, was investigated. The metric Nx required analysis of the L[subscript A,max] noise level to count as an overflight, as well as the number of overflights that represented the annoyance threshold. N₆₀ on a peak day with 50 overflights was shown to represent at least 80% of the complaint locations at BOS, MSP, LHR, and one runway at CLT. Alternatively peak day DNL is also shown to be a possible representative noise metric and will also be investigated. A noise metric representative of the impacts of frequent overflights allowed for communication of analysis results for possibilities for dispersed flight tracks. Important ways to communicate analysis results to stakeholders included: overall increase or decrease in population exposure to N₆₀ on a peak day with 50 overflights, the change in the number of N₆₀ overflights for the areas of impact, and presentation of the data that allowed stakeholders to understand the impact within the boundaries of their specific representative area. These tools will allow communities to understand the noise impacts of the procedures considered and will support the stakeholder decision processes.