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TR N EW S 28 8 SE PT EM BE Râ O CT O BE R 20 13 42 Harback is Principal Economist, and Mahashabde is Senior Multidiscipline Systems Engineer, MITRE Corporation, McLean, Virginia. Much of the recent focus on sustainabilityfor aviation has been on airports, throughthe development of sustainability planning documents for achieving airport-specific goals. These documents identify initiatives for improving envi- ronmental performance, such as energy-efficiency programs and Leadership in Energy and Environ- mental Design certification, as well as for attaining economic benefits while fostering collaborative rela- tionships with local communities. The scope of aviation sustainability goals and efforts, however, can expand beyond airports to the national airspace system as a whole. With evolving air transportation needs, revised traffic growth fore- casts, and tighter government budgets, sustainability principles can provide insights for assessing priori- ties and making investment decisions. The Federal Aviation Administrationâs (FAAâs) Next-Generation Air Traffic Management System (NextGen) offers opportunities to improve systemwide environmental performance yet balance economic and social objec- tives. Systemwide Goals FAAâs most recent strategic plan, Destination 2025, recognizes the need for systemwide sustainability goals and emphasizes the agencyâs commitment to âensuring America has the safest, most advanced and efficient, and sustainable aviation system in the worldâ (1). Although the previous strategic plan included environmental goals embedded within capacity goals (2), Destination 2025 advances a specific goal âto develop and operate an aviation system that reduces aviationâs environmental and energy impacts to a level that does not constrain growth and is a model for sus- tainability.â This represents a move toward a system- level approach to sustainability. Destination 2025 characterizes sustainability in terms of environmental and energy goals. Sustain- ability often is treated as synonymous with the envi- ronmental goals of the triple bottom line, because the social and economic components typically are addressed by other means, and the motivation for a more balanced, sustainable approach was driven by a heightened awareness of environmental outcomes. Sustainability in Airspace System Planning K A T H E R I N E H A R B A C K A N D A N U J A M A H A S H A B D E Environmental Sustainability in Transportation P H O TO : S A N D IEG O C O U N TY R EG IO N A L A IR PO R T A U TH O R ITY Six new gates in Terminal 2 West, part of The Green Build project at San Diego International Airport in California, opened in the spring. Aviation sustainability encompasses airspace as well as airport initiatives.
TR N EW S 288 SEPTEM BERâO CTO BER 2013 43 In addition to the goal of environmentally oriented sustainability, Destination 2025 addresses safety, a workplace of the future, access, and global collabo- ration. These goals represent a complementary blend of social and economic considerations. Although comprehensive economic guidelines call for trade-off analysis (3), the triple-bottom-line approach prompts a clear dialog about diverse, explicit priorities for informing decisions. This ele- vates social and environmental considerations that historically were difficult to quantify and offers an opportunity to reassess priorities in an evolving sys- tem. Economic and social considerations can change with the system, opening up opportunities to improve environmental performance. Changing Priority on Delay For instance, the emphasis on managing delay is changing, as expectations of traffic growth in the national airspace system decreased with the recent economic recession and the accompanying changes in air carriersâ business models. Current aircraft oper- ations levels are approximately 74 percent of the 2000 level (4) at airports with FAA and contract traf- fic control service. FAAâs 2013 aerospace forecast esti- mated the number of aircraft operations in 2030 at 86 percent of the level observed in 2000 (4). This contrasts starkly with the high-demand growth envi- sioned years earlier. In 2005, 2016 was forecast at 115 percent of the 2000 levels (5), and the 2011 fore- cast predicted operations at 99 percent of the 2000 level in 2030 (6). Although congestion in the national airspace sys- tem is as much a function of traffic distribution as of overall volumeâsome airports and airways are more capacity-constrained than othersâthe long-term delay problem may not be as dire as predicted. Within a framework of sustainable system planning, reductions in future anticipated delay may present an opportunity to reevaluate priorities in the context of reductions in future traffic volumes. This scenario represents a potential shift in the relative importance of each component in the triple bottom line and could result in specific outcome goals that could lead to even greater improvements in the environmental performance of the national airspace system than those described in Destination 2025. In a future characterized by less delay, a reeval- uation of priorities may elevate initiatives that were not as highly valued when the expectations of greater delay governed decision making. Delay in the national airspace system is an eco- nomic, social, and environmental driver, raising costs and limiting system access by operators and passen- gers and creating negative environmental impacts through excess fuel burn. Consequently, reductions in delay typically translate into improvements in all three aspects of the triple bottom line. NextGen Trade-Offs In some cases, however, NextGen procedures may improve environmental performance while produc- ing no improvements or even decreases in some mea- sures of operational efficiency. For example, continuous descent approaches for landing at air- ports can reduce fuel burn, emissions, and noise impacts by eliminating the level flight segments typical of conventional descent approaches (see Figure 1, above). Level flight segments during descent, however, are often imposed to accommodate other traffic such as departures; therefore eliminating all level flight segments may adversely affect airport capacity or increase the fuel consumption by other flights. In contrast, optimized deployment of continuous descent approaches, known as optimized profile descents, represent an implicit trade-off across the triple bottom lineâmaintaining or maximizing throughput by allowing for some level flight seg- ments to manage flows into and out of the airport, but eliminating the unnecessary level segments. In the future, trade-offs within the environmen- tal dimension may also be necessaryâfor example, between noise and emissions. Continuous approaches are winâwin for fuel and noise, but this is not necessarily the case for all potential changes in the airspace system. Flight paths strictly designed to reduce fuel use may not be acceptable to local com- munities if the changes concentrate noise over sen- sitive areas or shift noise to areas previously unexposed. Local communities historically have placed a greater weight on noise reduction in their FIGURE 1 The continuous descent approach creates a conflict with traffic departing an airport. The optimized profile preserves much of the continuous descent fuel savings, without reducing capacity or increasing fuel burn for departing flights.
TR N EW S 28 8 SE PT EM BE Râ O CT O BE R 20 13 44 trade-offsâbut how noise may be weighted in com- parison to fuel burn, carbon dioxide emissions, and local air quality is not often explicitly addressed. In general, translating performance trade-offs into meaningful impacts and considering their proper- ties across the triple bottom line will facilitate improved performance in most if not all of the dimensions. Transparent, thorough trade-off analy- sis, along with strong collaborative relationships among stakeholders, will be critical in resolving some of these challenges. Relevant Metrics Addressing difficult tradeoffs and triple-bottom-line analysis of NextGen to support a reevaluation of pri- oritiesâand in general, FAAâs move toward social, economic, and environmental sustainabilityâwill require data and analytical capabilities that are inte- grated and consistent across NextGen programs, as well as detailed performance benchmarking and care- ful development of metrics across the three sustain- ability domains. Much of this work to evaluate the benefits of NextGen and the expected performance improve- ments in the national airspace system is under way through FAAâs Office of Environment and Energy and the Office of NextGen. Opportunities to improve the metrics to support system-level decision making and performance monitoring include ongoing integration of the tools for evaluating trade-offs among the sus- tainability objectives. In developing metrics, a first step is to correlate with a desired outcome that FAA can control through investments and actions. For example, flight fuel con- sumption depends not only on FAA procedures and air traffic management concepts and technologies, but Nighttime contrails from aircraft over a Phoenix, Arizona, neighborhood. Efforts to change flight paths for reduced fuel use must be balanced with the noise concerns of surrounding neighborhoods. P H O TO : B IA W A K_ G ILA, F LIC K R I n 2008, a group of airport stakeholders gath-ered to discuss the need for an industrywide resource that could provide consistent guidance for sustainability planning and for sustainable design and construction. Individual airports had begun developing or improving sustainability plans, as well as sustainable design and construc- tion guidelines to meet sustainability commit- ments. Recognizing the duplication in many of these efforts and that many airports lacked the resources to produce sustainability documents, the volunteer stakeholder group founded the Sustainable Aviation Guidance Alliance (SAGA) to pool resources and create consistent, compre- hensive, and consensus-based sustainability resources for airports. In the years since, SAGA has proved that a proactive and comprehensive stakeholder collaboration can produce tools and resources that initiate change across an industry and beyond. SAGA sought to consolidate the available information about sustainability, including intro- ductory material on what sustainability is and how it is applied at airports, processes for plan- ning and maintaining sustainability programs, and sustainable design and construction prac- tices. Participants included members from indus- try groupsâsuch as the American Association of Airport Executives, Airports Council Interna- tionalâNorth America, the Airport Consultants Council (ACC), and Airlines for Americaâand the Federal Aviation Administration (FAA), as well as and various airports and consultants. Approxi- mately 100 people have participated in SAGAâ the planning group consisted of 20 volunteers from a diverse set of employers, 10 volunteers executed the work, and approximately 80 volun- teers served as reviewers of the final products. SAGA conducted a comprehensive literature review to identify sustainability initiatives and The Sustainable Aviation Guidance Alliance Stakeholder Collaboration Yields Practical Resources K R I S T I N L E M A S T E R The author is Principal, CDM Smith, Inc., San Francisco, California.
TR N EW S 288 SEPTEM BERâO CTO BER 2013 45 also on factors that FAA does not control, such as air carrier fleet use, operating practices, and fleet com- position. Fuel burn therefore is an imperfect metric for describing the environmental performance of the air navigation service providerâs operation of the national airspace system. An example of a metric that overcomes this prob- lem is the United Kingdomâs NATS 3Di, which gener- ates an environmental inefficiency score by comparing the trajectory flown by an aircraft with the optimal or airline-preferred trajectory (7). The metric was devel- oped in collaboration with airlines and provides a financial incentive for NATS to improve its annual average 3Di score. Metrics like 3Di that pinpoint system-level ineffi- ciencies and identify specific measures to improve performance along the social, economic, and environ - mental dimensions could be used to assess NextGen performance. In summary, a more comprehensive understanding of national airspace system behavior can be facilitated with appropriate sustainability met- rics and modeling capabilities; these metrics and mod- els may provide better information for decision makers and may allow for more flexibility in reassess- ing priorities for NextGen investments. Acknowledgments This article is based on copyright work produced by the MITRE Corporation for the U.S. government and is used with permission. The contents of this article reflect the views of the authors and do not necessar- ily reflect the views of FAA or the U.S. Department of Transportation (DOT). Neither FAA nor U.S. DOT makes any warranty or guarantee, or promise, expressed or implied, concerning the content or accuracy of the views expressed. References 1. Destination 2025. Federal Aviation Administration, 2011. 2. 2009â2013 Flight Plan. Federal Aviation Administration, 2008. 3. Guidelines for Preparing Economic Analyses. EPA 240-R- 10-001, Environmental Protection Agency, December 2010. 4. Aerospace Forecasts, FY 2013â2033. Federal Aviation Administration, 2013. 5. Aerospace Forecasts, FY 2005â2016. Federal Aviation Administration, 2005. 6. Aerospace Forecasts, FY 2011â2030. Federal Aviation Administration, 2011. 7. How 3Di Works. NATS, United Kingdom, 2012. www.nats. co.uk/wp-content/uploads/2012/07/3di_Infocard.pdf. On-time flights add to airport efficiency and environmental friendliness. Aircraft towing conserves fuel and is among the many sustainability measures employed by airports and included in the Sustainable Aviation Resource Guide. developed a process for starting, maintaining, and enhancing a sustainability program at an air- port. The final products included a searchable online database of approximately 1,000 sustain- ability practices and a handbook for airport sus- tainability, the Sustainable Aviation Resource Guide, both of which are available on the SAGA website.a The website was developed to serve as a one- stop sustainability resource for airports of varying sizes, geographies, and operating conditions. The handbook and database include content that other industries can applyâsuch as energy- efficiency measures. A series of conference pre- sentations and committee announcements intro- duced SAGAâs resources to the industry in 2009 to a favorable reception. The resources were used in FAAâs development of a Sustainable Master Plan Pilot Program and received the prestigious Jay Hollingsworth Speas Award in 2011 from the American Institute of Aeronautics and Astronau- tics, the American Association of Airport Execu- tives, and ACC. Despite the practical value of the searchable database, the content was static and soon became outdated. In addition, because the data- base was developed through a volunteer effort in a short time, many features that would have enhanced its usability could not be included. To improve the resources, the Transportation Research Boardâs Airport Cooperative Research Program has launched two projects, Enhancing the Airport-Industry SAGA Website,b and Airport Sustainability Practices: Tools for Evaluating, Mea- suring, and Implementing,c both scheduled for completion in 2014. awww.airportsustainability.org. bACRP Project 02-30, http://apps.trb.org/cmsfeed/TRBNet ProjectDisplay.asp?ProjectID=3031. cACRP Project 02-28, http://apps.trb.org/cmsfeed/TRBNet ProjectDisplay.asp?ProjectID=3029. P H O TO © B R ISB A N E A IR PO R T P H O TO : S IM O N L A W , F LIC K R