Enhanced Modeling of Aircraft Taxiway Noise, Volume 2: Aircraft Taxi Noise Database and Development Process (2013)

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ix EXECUTIVE SUMMARY This aircraft taxi noise modeling research funded by the Airport Cooperative Research Program of the National Academy of Science is in response to a growing understanding that continuing reduction of noise levels related to aircraft flight operations means that previously ignored noise from aircraft ground operations (such as taxiing), now has potentially more of an effect on nearby communities. Taxiing and idling in runway queues, especially during peak hour operations or at night, can significantly contribute to noise contours and Day-Night Average Sound Levels (DNL). This is particularly true when taxiways are very close to the airport property lines and near neighborhoods or other noise sensitive locations. The Federal Aviation Administration’s (FAA) Integrated Noise Model (INM) is the agency’s required tool for environmental impact statements, environmental assessments (Boeker, et al., 2008), and Part 150 studies. Under FAA development is the Aviation Environmental Design Tool (AEDT) (Koopmann, et al., 2012) which will eventually replace INM for such purposes. Currently, noise modelers who need to assess the contribution of noise from aircraft ground operations must develop a workaround approach within the models or externally. This report documents the procedures developed and employed in the creation of a Taxi Noise Database for INM / AEDT. Under ACRP project 11-02 (Page, et al., 2009, Page & Hobbs, 2010) aircraft taxi noise acoustic sensitivity studies were conducted, to document the importance of the modeling elements within INM and AEDT in three areas: source noise, operations, and environmental propagation. The key recommendation was the development of a new taxi source noise database for INM / AEDT. The current project, ACRP 02-27, built on the taxi noise and INM/AEDT modeling understanding developed under the prior project, developed a methodology for creation of a Taxi Noise dataset and applied it to the full fleet of commercial Turbofan (Jet) and Turbo- prop aircraft in the INM/AEDT database. Modeling fixed wing Turbofan (Jet) and Turboprop commercial transport taxi noise data in INM / AEDT requires three fundamental database components: • Noise-Power-Distance tables for the taxi operating condition for each aircraft; • Spectral Classes for the taxi operating condition; and • Turbofan (Jet) and Turboprop Directivity Functions for the taxi operating condition. A prioritized hierarchy of three technical processes were developed and are documented. The hierarchical process is necessary due to limited data availability for each specific aircraft- engine configuration. Thrust-noise sensitivity trends were developed from first principles modeling via NASA’s Aircraft Noise Prediction Program (ANOPP) applied to the taxi operating condition. For a given aircraft, there are three possible database methods, based on the availability of data: Method I. Empirical Taxi Noise Data and ANOPP data; Method II. Empirical Taxi Noise Data Only; and Method III. No Empirical Taxi Noise Data.

x Method I is a hybrid technique that uses the empirical taxi noise data, assigns a thrust value based on FDR data, applies an ANOPP delta-dB vs. delta-Thrust relationship to develop the Taxi thrust-noise sensitivity and the taxi NPD curve. Method II is similar to method I, in that the “nominal Taxi Thrust” is based on empirical data, then adjusted to other thrust levels based on a generalized ANOPP delta-dB vs. delta-thrust relationship to obtain the taxi noise-thrust sensitivity. The generalized ANOPP noise-thrust relationship is based on aircraft size. Methodology III is the least accurate of the three methods because it has no aircraft specific empirical taxi noise data. This method utilizes generalized empirical noise data and ANOPP thrust-noise sensitivity data.