National Academies Press: OpenBook

Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping (2009)

Chapter: Chapter 7. AEDT Implementation Concept

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Page 86
Suggested Citation:"Chapter 7. AEDT Implementation Concept." National Academies of Sciences, Engineering, and Medicine. 2009. Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping. Washington, DC: The National Academies Press. doi: 10.17226/22992.
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Suggested Citation:"Chapter 7. AEDT Implementation Concept." National Academies of Sciences, Engineering, and Medicine. 2009. Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping. Washington, DC: The National Academies Press. doi: 10.17226/22992.
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Suggested Citation:"Chapter 7. AEDT Implementation Concept." National Academies of Sciences, Engineering, and Medicine. 2009. Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping. Washington, DC: The National Academies Press. doi: 10.17226/22992.
×
Page 88
Page 89
Suggested Citation:"Chapter 7. AEDT Implementation Concept." National Academies of Sciences, Engineering, and Medicine. 2009. Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping. Washington, DC: The National Academies Press. doi: 10.17226/22992.
×
Page 89
Page 90
Suggested Citation:"Chapter 7. AEDT Implementation Concept." National Academies of Sciences, Engineering, and Medicine. 2009. Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping. Washington, DC: The National Academies Press. doi: 10.17226/22992.
×
Page 90
Page 91
Suggested Citation:"Chapter 7. AEDT Implementation Concept." National Academies of Sciences, Engineering, and Medicine. 2009. Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping. Washington, DC: The National Academies Press. doi: 10.17226/22992.
×
Page 91
Page 92
Suggested Citation:"Chapter 7. AEDT Implementation Concept." National Academies of Sciences, Engineering, and Medicine. 2009. Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping. Washington, DC: The National Academies Press. doi: 10.17226/22992.
×
Page 92

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86 CHAPTER 7. AEDT IMPLEMENTATION CONCEPT The core concept behind AEDT is that of modularity. Many of the computational modules were replicated (to varying degrees) in multiple legacy software algorithms and were integral to their respective applications. Under the new AEDT architecture, these core components are being decoupled and integrated to create a common set of modules that can be leveraged to create new tools. A primary feature of the AEDT approach is the ability to quickly and seamlessly add new modules by simply adding them to the suite of tools and exposing their interface for developers to use. The AEDT taxiway noise module concept presented here draws upon capabilities that are suggested to be added to INM Version 7 (Step 1) and capabilities already existing in EDMS Version 5 and slated for implementation in AEDT. The Step 2 AEDT implementation concept and has been structured in a manner compatible with the current AEDT system design (36). 7.1. EDMS Description EDMS (3) is a combined emissions and dispersion model for assessing air quality at airports, was developed by the Federal Aviation Administration (FAA) in cooperation with the United States Air Force (USAF). The model is used to produce an inventory of emissions generated by sources on and around the airport or air base, and to calculate pollutant concentrations in these environments. Within EDMS, taxiway emissions are modeled for on- ground, non-runway operations of aircraft. The simplest way to generate an emissions inventory and obtain a coarse estimate of the total annual emissions is to use the ICAO/EPA default times in mode along with the default operational profiles, and the annual average weather from the EDMS airports database. Doing so only considers the total number of operations for the entire year without regard to when they occurred If a more precise modeling of the aircraft taxi times using the Sequencing module is desired (required if dispersion is to be performed), then the user must define the airport gates, taxiways, runways, taxi paths (how the taxiways and runways are used) and configurations (weather dependent runway usage). 7.2. Airport Description EDMS contains modules that allow the user (when needed for sequence modeling) to define in detail an airport’s taxiway layout, outbound pathways for every gate - runway pair and inbound pathways for every runway exit - gate pair. The airport layout of EDMS defines the physical “fixed” infrastructure components of the airport, while the airside network components include the runways, gates and taxiways, which are optional for performing an emissions inventory. This information will be needed by the taxi module. Airport Description Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features High Easy* 0 0 None * Already a planned part of AEDT

87 7.2.1. Taxi Tracks EDMS allows users to identify one taxi path for each departure gate-runway pair and each arrival runway-exit-gate pair. Inbound taxiway paths are defined for each runway exit to allow aircraft of different sizes to be assigned the first possible runway exit and to automatically determine the pathway to be followed based on an aircraft’s gate and runway assignments and flight profile. Each departure is assigned a unique taxi path when the appropriate gate-runway pair is identified and similarly, each arrival operation is assigned a unique taxi path when the appropriate runway-exit-gate pair is identified. For computing taxi noise the inputs, operational assignments and taxi paths should be made accessible to the taxi noise module in AEDT. Taxi Tracks Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features High Easy* 0 0k None * Already a planned part of AEDT 7.2.2. Taxi Profiles At present information about the aircraft engine height is not a part of the AEDT Fleet Database. If a feature to automatically populate the aircraft engine height is to be implemented in AEDT this will need to be added to the AEDT Fleet database. If this data is already gathered as part of an INM implementation effort, the task will not need to be repeated and the engine height data only added to the AEDT database. Taxi and Hold Profiles Implementation Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features Medium Moderate 160 24k Aircraft Engine Height Dataset Aircraft Engine Height Dataset - Assimilation from Public Data Sources Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features Medium Moderate 60 9k Taxi and Hold Profiles GUI 7.2.3. Gates A gate is a physical point of arrival and departure for an aircraft, and is defined as a polygon. The location of the gate can affect the overall annual emissions inventory by changing the distance (and hence the taxi time) needing to be traversed between the gate and the runway. Within EDMS taxi paths are only required to have some overlap with the gate. If a taxiway is supposed to connect to a gate (or runway or intersect with another taxiway), then the taxiway must be constructed such that it has some overlap with the connecting gate (runway, or taxiway). There are three approaches for handling taxi operations directly to the gates. The suggested EDMS implementation is option b.

88 This approach does not require any EDMS modification. The current day EDMS (5.x), permits one to model aircraft operations in higher level of detail by defining a taxiway or taxi path to each aircraft parking position. In this way, a gate is represented by a point, and the total number of gates, taxiways and taxi paths will be (significantly) increased. To extend a taxi path to a point inside the gate polygon to account for a portion of a taxi path that aircraft traverses within a gate area, all aircraft would traverse the same path to get into or exit the gate. This approach requires a slight modification of EDMS. To define a network of paths within each gate. Each aircraft traverses a path (within the gate area) assigned in a (pseudo) random manner. This approach would require much larger implementation effort. The Check Taxipaths feature in EDMS performs a check of whether the taxiways used in the taxi paths have proper linkages. Since the aircraft position at the gate is not specifically defined in EDMS a mechanism for defining the aircraft resting location will be needed. This could be determined without significant user input by utilizing the connecting taxi path and creating a geometric extension into the gate polygon area, considering the known aircraft lengths and procedures; however, this would require the creation of an aircraft database of geometric parameters which is information that is readily available for the range of aircraft types in INM. The interface should display this location graphically within the GUI so that the user can verify that the taxi path extension and gate polygon area are properly defined or apply any necessary changes (Figure 69). Figure 69. Taxi path extension into the gate polygon area. Gate Polygon Geometry and Assignments Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features High Easy* 0 0k None * Already a planned part of AEDT

89 Taxi Path Extension into the Gate Polygon Area Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features Medium Medium 80 12k Aircraft Geometry Database 7.2.4. Terminal Area Terminal Areas are neither defined nor used in EDMS, however they serve a useful function in the prediction of taxi noise when using lower fidelity inputs. The terminal area may be defined as a polygon (similar to the gate area) and used when specifying operations, namely by connecting terminals to runways rather than specific gates. A GUI input similar to the gate definition (Figure 69) may be utilized in conjunction with the current EDMS gate geometric extension to define track ends. A feature such as this would most likely be implemented for airports where known aircraft and airline types utilize predominantly specific terminals thereby relieving the user of modeling specific gate usage. Terminal Area Geometry and Assignments in GUI Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features Low Medium 40 6k None 7.2.5. Taxi Speed Speed is the taxi speed of an unimpeded aircraft on that segment of the taxiway and in EDMS it is entered by the user. This parameter, input as part of the Taxiways screen (Figure 70) should be shared with the taxi noise module in AEDT. In the event that multiple speeds are needed for different analyses, the ability to easily copy and edit taxiways, as well has define multiple taxiways whose only difference is speed, should be permitted. Figure 70. Taxiway input in EDMS.

90 Taxi Speed Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features Medium Easy* 0 0k None * Already a planned part of AEDT 7.2.6. Buildings The Buildings window of EDMS enables the user to specify the identification and location of each building at the airport. In dispersion analyses, buildings affect the emitted point source plumes, and therefore can have a significant impact on concentrations. In taxi acoustic analysis, buildings can provide a significant shielding effect primarily via blockage of line of sight. The acoustic module in INM 7 has the capability to utilize Maekawa’s shielding to determine the building attenuation and will therefore be able to take advantage of the building geometry which has been defined for dispersion modeling. Within AEDT this building information (location and height) should be shared with the Taxi Noise Module. Building Definitions Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features Low Easy* 0 0k None * Already a planned part of AEDT Acoustic Impact of Building Definitions Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features Medium Medium Acoustic Module Implementation 7.3. Operations 7.3.1. Times in Mode “Times in mode” refers to the amount of time an aircraft spends in different portions of a landing-takeoff cycle (LTO). In EDMS an LTO cycle is divided into six phases: approach, taxi- in, startup, taxi-out, takeoff and climb-out. Within EDMS Version 5.1, the landing roll portion of the approach segment is incorporated into the taxi-in time. For computation of taxi noise based on times in mode data, the taxi-in time in EDMS needs to be differentiated into separate landing roll and taxi-in segments. Landing roll noise is computed as part of the flight contribution whereas taxi-in noise is considered part of the taxi operation. There are two options for determining the times in mode for the aircraft being modeled: Performance Based and ICAO/USEPA Default. Performance based modeling uses the specific airframe and engine characteristics along with weather data to model each flight dynamically. ICAO/USEPA defaults are standardized values read from a table.

91 Taxi times generated from either form of modeling should be made available to the taxi module. As was suggested in the sensitivity study under some circumstances it could be appropriate to simply distribute the times in multiple distinct locations by taking guidance from runway and taxiway usage statistics. Times in Mode Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features Medium Easy* None * Already a planned part of AEDT 7.3.2. Taxi Time Modeling EDMS contains two options for determining taxi times: User-specified taxi times for each aircraft and Delay and Sequence Modeling. For user-specified taxi times, the user can define defaults for taxi-in and taxi-out times that apply to each aircraft added to the study. These taxi times can then be changed for each aircraft if necessary. Delay and Sequence modeling takes into account the aircraft operational schedule demands, active runway configurations, and delays associated with airport capacity to model the ground movement of the aircraft and determine specific taxi times for each aircraft operation. Taxi times generated from either form of modeling should be made available to the taxi module. Delay and Sequence Modeling Results Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features High Easy* None * Already a planned part of AEDT 7.3.3. Aircraft Schedule Options User defined schedule files containing scheduled pushback and landing times can be used by EDMS as the basis for sequence modeling. If no schedule file is available, EDMS can generate a “pseudo-schedule” from the annual operations and operational profiles, and use that as the basis for sequence modeling when that is selected. This sequence data can be used within the noise module to make day, evening and night time assignments to operations for computation of acoustic metrics. Aircraft Schedules Importance Difficulty ROM Effort (Hrs) ROM Cost ($) Other Required Features High Easy* None * Already a planned part of AEDT

92 7.4. Acoustic Computation As stated in the introductory sections, Step 2 implementation details have been structured with the understanding that those features cited for Step 1 have been made available. With regards to the Aircraft Acoustics Module no additional AEDT features will be needed to permit taxi noise computation. The primary changes will be those necessary to access and utilize the aforementioned input data from EDMS and other AEDT modules. 7.5. Thrust-Noise Sensitivity The sensitivity study made some assumptions to link together acoustic and operating state data, and projected reasonable acoustic changes with changes in thrust. Given a lack of concurrent acoustic and FDR data, this assessment was performed for one very common aircraft engine type (CFM56 series) for which we had isolated acoustic (B737) and isolated FDR (A319, A320, A321) data. For this engine series, based on an approximate 0.70 dB/klb thrust, one would expect for a thrust change from 5 to 15% to result in less than +/- 1dB (or a total spread of about 2dB) for a single operation. While this acoustic change in source level is not very large, there could be situations at certain airports where such changes could accumulate over repeated operations and cause a localized bulge in the taxi noise contours. Taxi operations occurring frequently in a specific location with regular operational increases in thrust (i.e., in a holding taxi queue leading up to a specific runway during periods with flight delays) might therefore require a higher fidelity modeling of thrust-noise sensitivity. In regions where the community is in close proximity to the holding queues or if there is demonstrated community concern, such higher fidelity thrust-noise modeling could be warranted. The short term approach suggested here addresses only a ‘nominal’ taxi condition and makes no allowance for changes in noise with changes in thrust. This is due in part to the lack of concurrent measurement and operating state (FDR) data and the expectation that a reduced number airport noise studies will require such high fidelity modeling. The “Comprehensive Long Term Solution” to this situation suggests that further measurements be conducted in order to obtain this thrust-noise data experimentally. In order to utilize such data, further changes will need to be made to AEDT in order to provide the capability to model thrust-noise sensitivity for taxi operations. The ROM level of effort and cost to conduct these acoustic measurements and AEDT thrust-noise sensitivity programming changes are not included in this report.

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TRB’s Airport Cooperative Research Program (ACRP) Web-Only Document 9: Enhanced Modeling of Aircraft Taxiway Noise, Volume 1: Scoping explores ways to model airport noise from aircraft taxi operations and examines a plan for implementation of a taxi noise prediction capability into the Federal Aviation Administration's integrated noise model in the short term and into its aviation environmental design tool in the longer term.

ACRP Web-Only Document 9: Enhanced Modeling of Aircraft Taxiway Noise, Volume 2: Aircraft Taxi Noise Database and Development Process documents the procedures developed and employed in the creation of a taxi noise database for the U.S. Federal Aviation Administration’s Integrated Noise Model and Aviation Environmental Design Tool (AEDT). The AEDT is currently under development.

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