Improving the Air Transportation System
The air transportation system is changing and will continue to change. Over the long term, however, it will be difficult for the air transportation system to change rapidly enough to meet changing requirements related to capacity, environmental effects, consumer satisfaction, safety, and security, while meeting ongoing requirements for the economic viability of service providers.
Most efforts to increase system capacity are focused on evolutionary or incremental changes that address specific constraints while aircraft are en route, in terminal areas, or on the ground at airports. For example, parallel arrival streams may be used when airport visibility is restricted to restore capacity to levels typical of clear weather (VMC, or visual meteorological conditions). Another option would be the use of advanced systems to adapt traffic flow in response to convective weather fronts to minimize or eliminate reductions in capacity. Meeting demand over the next 25 to 50 years, however, is likely to require a more revolutionary approach that seeks to increase capacity significantly beyond the level that the system currently enjoys even under ideal weather conditions. This may require completely different system operating concepts. The key point is that long-term goals may need to focus on fundamental, revolutionary structural changes in the air transportation system. One approach to defining future operational concepts is to propose solutions to shortcomings in the current system. To facilitate revolutionary change, however, a better approach would be to begin with a vision of the capabilities desired for the air transportation system of the future and then investigate how to provide those capabilities.
IMPETUS FOR CHANGE
The air transportation system in the United States and around the world is changing and will continue to change in response to many different factors. Although new technologies have the potential to enable more efficient operations, the current economic crisis faced by most major airlines makes it difficult for them to make large investments in new technologies or infrastructure. Public concerns about safety and security, poor conditions in the general economy, and other factors that temporarily suppress demand can be economically devastating to the air transportation industry. Demand for air transportation services can also be suppressed by the reluctance of passengers to travel when delays from undercapacity or intrusive security procedures become too onerous. Airlines’ business decisions are also constrained by the competitiveness of the industry and the desire of each service provider to maintain market share, regardless of the economic climate. However, temporary setbacks notwithstanding, demand for passenger and cargo services has always increased over the long term and is expected to continue increasing in the future.
Even before 9/11, the government played a key role in ensuring safety, in part because it is so difficult for the public to assess risks in systems as complex as the air transportation system. In addition, high-profile accidents and incidents create tremendous public and political pressure for the government to act, even when it’s too early to know for sure the cause of a particular tragedy. Other factors that will shape the future of air transportation include new methods of communications and other changes in the world that may cause the demand for business travel, leisure travel, or air cargo to grow more slowly—or faster—than current long-term projections.
Predicting the future of the air transportation system is difficult because it depends on the actions of—and interactions among—many different factors and organizations, many of which are themselves changing in ways that are unprecedented and hard to predict. Nonetheless, the parameters used to measure the performance of the system—comfort, convenience, costs, and societal impact—are not likely to change any time soon, and they can be used to guide the development of technologies even if the environment in
which they will be employed cannot be precisely determined in advance.
Operational concepts can be used to describe how the air transportation system might advance, from the reasonable certainty of near-term requirements, technologies, and schedule implementation to a less certain vision of the long-term future.
Today there is no single national vision for the air transportation system 25 to 50 years from now. The visions that do exist, however, have a unifying theme—namely, improving performance in terms of capacity, environmental effects, safety, and security. Chapter 1 describes a larger set of system performance parameters that future visions should embrace. Existing public policy on access to the airspace and equitable use of the facilities in the air transportation system is expected to continue, and air operations are expected to increase overall, growing with the population and the economy. Long-term operational concepts should support a broad vision that encompasses all of these expectations.
Near-term operational concepts should ideally be derived from clearly understood transportation system needs. The pace of their implementation will be limited by the availability of mature technology and a host of nontechnological factors. Long-term operational concepts can serve as a guide for examining technological and nontechnological proposals and societal presumptions. To prepare for the future, a range of operational concepts should be developed, examined, and revised using an iterative process that considers potential changes in technology, society, and the air transportation system itself. This requires the ability to test and examine operational concepts for the future in a comprehensive manner. For example, these operational concepts should consider environmental needs and benefits. In the future it may be desirable to control the cruise altitude or flight path of an aircraft to avoid the formation of contrails that affect climate. In general, improvements in system efficiency can be expected to improve environmental performance by reducing fuel consumption, but trade-offs between emissions and community noise may need to be balanced.
The process of developing operational concepts also provides an opportunity to achieve national consensus among the various agencies and stakeholders at a level of detail that permits more focused agreement and planning. The salutary effect of this unifying activity is that it can stimulate and guide research in both technical and nontechnical areas.
The FAA’s Operational Evolution Plan represents a general consensus on one way to bring known technology, infrastructure development, and system needs together and implement them to increase the capacity of the air transportation system over the next 5 to 10 years. However, the Operational Evolution Plan is not intended as a basis for examination and testing of longer term concepts or as a guide for research that will impact needs over the next 25 to 50 years. In particular the modeling and simulation tools of today are not sufficient to evaluate many long-term concepts and transition issues.
The vision published by RTCA, Inc., discusses how to accommodate growth in demand through 2020 and beyond.1 It states that “operations are increasingly aircraft centric, focusing on performance rather than equipment standards, with use of required navigation performance as a key step in enabling greater efficiency, flexibility, and capability enhancements. Access to real-time information for decision-making supports efficient operation of the air transportation system when capacity limitations such as weather adversely impact the system. Enhanced system supported coordination and decision support capabilities allow the system to migrate beyond human centric operations” (RTCA Free Flight Steering Committee, 2002). The same RTCA document contains an evolutionary concept of operations that proposes changes in the air transportation system in three time periods (through 2005, 2005 to 2010, and beyond 2010). As with any future operational concept, this concept should be tested through simulation and modeling to estimate the technological and nontech-nological needs, benefits, and costs. The concept should then be refined and reevaluated as a basis for guiding research, identifying transitional issues, and determining if it is likely to succeed as a unifying effort in guiding future development of the air transportation system.
Looking out to 2050, it is not too early to begin identifying notional operational concepts, developing evaluation tools, and supporting research that enables the process to go forward. Simulation and modeling capabilities more powerful than today’s will be required to better understand the complexities of the suite of systems that comprise or will contribute to the future air transportation system. An iterative operational planning process is essential for articulating the direction in which the air transportation system is most likely to proceed as performance improves.
Finding 2-1. The Challenge. Developing meaningful and useful operational concepts stemming from a broadly defined vision of the air transportation system 25 to 50 years hence is a critically important task in the process of improving the performance of the system.
Recommendation 2-1. Operational Concepts 2050. The federal government, working with other stakeholders in the air transportation system, should develop a coherent set of
operational concepts to support a vision for the air transportation system in 2050 to guide (1) long-term research and (2) the evolution of and transition to a more advanced air traffic management system. The set of operational concepts should be continually, objectively, and rigorously evaluated (for example, through comprehensive simulation and modeling) and iterated to reflect feedback from stakeholders, conflicts between alternative concepts, and the best understanding of the future costs, benefits, and requirements that are likely to evolve in response to changes in the real world, the current state of technology and systems operations, and future expectations. Strong national leadership should coordinate the efforts of all involved federal agencies and other stakeholders in the air transportation system to build toward concepts that best support the vision.
RESEARCH AND TECHNOLOGY
To a large extent, operational concepts dictate specific technology needs. However, regardless of the specific operational concept, many attributes of the future air transportation system can be predicted that point to general research and technology needs.
The first attribute is that the future air transportation system will involve much more automation both on the ground and in the air. Many modern aircraft are already so highly automated that, once programmed by the pilots, they can perform almost all guidance, navigation, and control tasks autonomously. This automated capability would need to be enhanced, however, to fit into many future operational concepts that require new functions—for example, required time of arrival at fixes, self-spacing or station-keeping, and self-separation. The modern air traffic control and management system is not highly automated, and it may prove nearly impossible to develop and test the underlying algorithms for fully automatic control in all situations, especially in the face of disruptions and emergencies; the same is generally true for airline operations centers. Therefore, some functions may be fully automated (e.g., aircraft guidance), others may be supported via automated decision aids (e.g., controller decision aids; and automated monitoring and alerting systems), and still others may rely on human decision making while using information systems for communications, visualization and situation assessment, and prediction of future conditions. The automation of many of these functions requires continued research and development.
Second, humans will be an integral part of the future air transportation system until the (unforeseen) day when the system can be automated to the extent that it requires neither intervention nor monitoring. Rather than framing the allocation of functions as a matter of “machines versus humans,” emphasis should be placed on creating synergy between humans and machines where their combined performance is better than either alone could achieve. Substantial research into flight deck automation has demonstrated a wide range of problematic interactions between humans and automation that can be generalized to broader applications in air traffic management; other studies demonstrate similar issues with decision aids (Wiener and Curry, 1980; Sarter and Woods, 1992; Layton, Smith, and McCoy, 1994; Pritchett, 2001). Automation design often appears to be driven by technological capability with neither (1) sufficient insight into its functioning within the larger system nor (2) the ability to predict commensurate changes in coordination between system elements and the training required of human operators. Automation must be demonstrated to work with humans in the larger context of system performance in both nominal and off-nominal conditions. Additionally, the humans in the system will also require coherent procedures and training designed in concert with the technology.
Third, the future air transportation system will be more fully integrated. For example, systemwide optimization of traffic flows may negate the effectiveness of localized traffic flow management within air traffic control centers and sectors unless it is integrated into a nationwide discussion at all levels of air traffic operations. Likewise, functions traditionally assigned only to aircraft, sector controllers, traffic managers, or industry representatives (e.g., airline dispatchers) will need to incorporate joint decision making that involves several entities and considers their disparate objectives.
Fourth, the integration of functions into the future air transportation system will require distributing responsibility and decision making between and among disparate entities. These entities may be geographically distributed and will often represent the interests and viewpoints of different organizations. The distribution of authority and responsibility with a large system presents technical and organizational challenges that should be studied and evaluated rigorously. Likewise, enabling distributed operations will require more insight into communication, coordination, and collaborative work mediated over distances via information technology and automation.
Fifth, the future air transportation system will be complex by almost any measure of complexity, yet will need to achieve the highest levels of performance and safety in a wide range of anticipated and unanticipated conditions. The ability to imagine changes to the system outpaces the ability to develop implementing technologies and procedures, integrate them into a reliable and highly capable air transportation system, continuously operate the system, collect and assess data on system performance, and make future improvements. In addition to the simulation and modeling capabilities recommended in Chapter 3, suitable system engineering models are needed for guiding systems analysis, design, integration, and implementation, especially in the case of large software developments.
Finally, aircraft separation standards, at least where they form bottlenecks that limit system capacity, will need to be reduced. Current separation standards were based on system shortcomings that future technologies may address. Some of
these factors are related to aircraft design and are described in Chapter 4. Factors relevant to air traffic management technologies include the following:
Errors in control and knowledge of aircraft position, which might be reduced or functionally eliminated by ubiquitous and transparent communication, navigation, and surveillance technologies.
Lack of situation awareness, especially with regard to current and future separation, which might be mitigated by improved sensors and displays, such as synthetic vision, cockpit display of traffic information, and controller displays.
Safety buffers to account for monitoring failures and late detection of potential conflicts, the size of which might be reduced by air- and ground-based conflict detection and resolution systems.
Wake vortices, which might be better understood and predicted or which might be sensed and avoided in real time.
Advanced technologies in some of the above areas could also produce important secondary benefits. For example, technology to directly sense the magnitude and location of wake vortices might also help avoid clear air turbulence, which is an ongoing threat to safety and passenger comfort.
Recommendation 2-2. Enabling Technologies. Enabling technologies applicable to a wide range of operational concepts should be developed in parallel with development and evaluation of long-term operational concepts so that the necessary technologies will be ready for whichever operational concept proves to be most beneficial. Technology areas of particular interest include the following:2
Automation technologies applicable to fully automated systems; automated decision aids; and information systems for communication, visualization, situation assessment, and the prediction of future conditions.
Technologies that support distributed, collaborative decision making and that foster coordination and interactions among multiple human and automated elements of the system.
Methods and technologies for moderating and abating the impact of noise and emissions locally, regionally, and globally.
Methods and technologies for predicting or directly sensing the magnitude, duration, and location of wake vortices and the potential to reduce separation standards without compromising safety.
Methods for identifying (1) the information required for situation awareness when humans are assigned novel (untried) tasks in future operational concepts and (2) sensor, computing, and display technologies for better supporting situation awareness, judgment, decision making, and planning. Relevant technologies include synthetic vision, cockpit and controller displays for novel air traffic management functions, fast-time simulation and computational functions for predicting future conditions, and alerting. These methods and technologies should be investigated for their potential to (1) reduce separation standards without compromising safety and (2) enable changes in the roles of humans within the system.
Systems-engineering methods that are (1) capable of conceiving and analyzing systems of the complexity of air transportation and (2) suitable for governing the design, testing, and implementation of these systems.
Avionics technologies that will provide ubiquitous and transparent communication, navigation, and surveillance capabilities; enable cost-effective, reliable air traffic management; and contribute to the reduction of separation standards without compromising safety.
Recommendation 2-3. Design of Complex Human-Integrated Systems. The design of human-integrated systems—that is, systems that rely on the combined activities of humans and machines—presents significant challenges at every level, from the systems level (e.g., creating effective teamwork within operations involving many human operators and automated system elements) to the detailed design level (e.g., developing operating procedures and system displays). Research in the following areas is required to understand and address these challenges:
A broad, interdisciplinary approach that includes technology designers, users, and experts in human and organizational performance from the earliest stages of conceptual design through final implementation to develop technology that effectively supports human behavior and recognizes the need for concurrent design of procedures, training, and technology.
Geographically distributed activities, such as coordinated decision making and planning, that are mediated by computers and automated system elements.
Human factors, human-automation interactions, and functioning of teams of humans and automated system elements.
Specific impact of newly automated functions and changes in human roles.
System engineering methods for addressing organizational and systemwide issues.
BEYOND TECHNOLOGY DEVELOPMENT
The air transportation system includes aircraft, air traffic control and air traffic management systems covering every phase of flight, airports, labor, airlines, and other organizations involved in research, development, manufacture, operation, certification, and regulation of aircraft and aviation systems. The previous sections of this chapter focus on air traffic control and air traffic management systems. Chapter 4 focuses on aircraft and aircraft technologies. These are the segments of the air transportation system where government research and technology development have the most direct impact. However, the ability to introduce and manage change, including technological change, is also a function of many other factors. The federal government, in particular, has tremendous leverage in its power to set economic policy, regulate the aviation industry, and collect and disburse billions of dollars in aviation taxes and general revenue each year. In addition to technological research to improve the performance of aircraft and air traffic management systems, the air transportation system would also benefit from research that addresses institutional issues; processes for modifying regulations, certification requirements, and operating procedures; societal concerns about aircraft noise and emissions; demand; and economic factors.
Most organizations fear both technological and business risk as well as changes that could create risk. Although current organizational structures and policies have shortcomings, they tend to be known and manageable. Change offers the potential to improve the current situation, but it also creates uncertainty and the risk of unforeseen consequences. Change is of particular concern if it could damage the vested interests of some organizations (e.g., by changing existing job descriptions or organizational missions or, in the extreme, by eliminating jobs or business units). Change will also be resisted if it might allow some organizations to succeed at the expense of others. All of this creates tremendous inertia that must be overcome to change the status quo. Along with strong leadership (see Chapter 1), the air transportation system would benefit from research on processes to predict, identify, and resolve the conflicting objectives of different stakeholders. Such a program of research should recognize that air passengers, shippers, and aircraft owners pay the bills of the other stakeholders, even though customers often are not directly represented in stakeholder debates about the future vision. With the ultimate customers kept in mind, it is still possible, however, to suggest specific research to avoid or minimize the consequences of behavior that undermines the overall effort to implement new operational concepts and achieve the future vision.
The FAA must certify new aircraft and air traffic management systems and approve operational procedures prior to use. Current handbooks used in the certification of aircraft and aircraft systems do not cover many innovative system concepts, such as the shift of some air traffic management responsibilities to the cockpit. For such systems, criteria for certification and operational approval will need to be developed concurrently with the systems and procedures themselves to prevent substantial delays in implementation. Improved processes are also needed to (1) facilitate changes to current operational concepts and (2) implement new operational concepts and the new technologies needed to support them. In many cases, proposed changes will need to be coordinated with other nations and international organizations prior to implementation. Aircraft manufacturers and airlines, responding to the changing market for their products and services (as well as new government policies), make choices determining the size, speed, fuel efficiency, environmental characteristics, and other performance parameters of new aircraft. Those choices influence the comfort, cost, convenience, and societal impact of air transportation and hence the aggregate level of commercial air transportation activity. The structure of the airline industry and the operational strategies followed by the individual airlines evolve in response to government decisions and policies in three broad categories:
Public and private research and development efforts that produce the particular facilities, equipment, and systems available to manufacturers and airlines.
The provision of infrastructure and support services, principally airports and air traffic control services, and the related system of taxes and fees imposed at the national, state, and local levels.
Rules and regulations established by U.S. and foreign governments and by international regulatory bodies regarding operational procedures, safety, and business practices.
Economic factors directly affect system demand and capacity and levels of service available to various system users. Airlines attempt to maximize economic performance through decisions that weigh the impact of incentives and penalties built into the system of rules, regulations, taxes, and fees. These incentives and penalties should be carefully constructed to avoid encouraging behavior that makes it more difficult to achieve the future vision. Currently this may not be the case: The cost-benefit analyses used to justify new certification standards and regulations often lack credibility with the owners, operators, and manufacturers who must bear the costs of implementation. In addition, the process for setting U.S. government rules, regulations, taxes, and fees for airfield and airways capacity is not well supported by economic research that considers the likely responses of system operators and users to changes in aviation economic policies. For example, the tax on airline passenger tickets is calculated at $3 per passenger enplanement plus 7.5 percent of the value of the ticket. Because of the wide range in ticket prices, passengers on the same flight receiving the same level of service will be assessed different levels
of tax, even though passengers paying higher fares impose no more burden on the air transportation system than do discount passengers on the same flight. Weight-based landing fees exacerbate the distortions of the ticket tax. Large aircraft carrying many passengers impose essentially the same burden on system capacity as smaller aircraft. Large aircraft may require a larger investment in runways, but not in proportion to the higher fees they must pay. In fact, a small aircraft may place a larger burden on the air traffic management system if it has a low approach speed and must be merged into a landing stream of large aircraft with higher approach speeds.
The size, speed, fuel efficiency, environmental characteristics, and passenger comfort offered by future generations of aircraft, as well as the capabilities of the air traffic management system, will directly influence the cost and convenience of commercial air transportation and, hence, the aggregate level of demand for air transportation services. In order to appreciate the costs and benefits, understanding economic factors is especially important in small communities where the government subsidizes commercial air service because it cannot be justified based purely on market factors. Economic analyses should also be used to help assess different approaches for improving capacity—for example, by assessing the feasibility of various economic incentives or by comparing the cost of building more runways with the cost of developing a more capable air traffic management system that increases the capacity of existing runways. Improving safety and reducing environmental effects can reduce costs in terms of total, long-term costs and even, in many cases, of direct operating costs. Foresight, planning, and vision play an important role in determining the feasibility of achieving future goals; costs and consequences need to be recognized early on rather than waiting until after a system is deployed to recognize, for example, that it creates noise or air quality problems that will limit its implementation and benefits.
Finding 2-2. Nontechnological Impediments to Success. Technological research alone is insufficient to achieve the future vision. Research is also needed to (1) better understand the economic, environmental, political, institutional, and managerial factors involved in achieving key goals, (2) take advantage of synergies among these factors, and (3) overcome related impediments.
Recommendation 2-4. Research Needs Beyond Technology Development. The federal government should also support research to develop improved processes and methods in the following nontechnology areas:
Assessment of economic factors, such as taxes, fees, and subsidies established by the government, that influence (1) the demand for and the supply of air transportation services and (2) key decisions made by organizations and individuals involved in the provision and use of the air transportation system.
Modification of regulations, certification requirements, and operating procedures.
Prediction and resolution of conflicting objectives of different stakeholders in the air transportation system.
Understanding societal concerns about aircraft noise and emissions.
Layton, C., P. Smith, and C. McCoy. 1994. Design of a cooperative problem-solving system for en route flight planning: An empirical evaluation. Human Factors 36(1):94–119.
Pritchett, A. 2001. Reviewing the roles of cockpit alerting systems. Human Factors in Aerospace Safety 1(1):5–38.
RTCA Free Flight Steering Committee. 2002. National Airspace System Concept of Operations and Vision for the Future of Aviation. Washington, D.C.: RTCA, Inc., p. v.
Sarter, N., and D. Woods. 1992. Pilot interaction with cockpit automation: Operational experiences with the flight management system. International Journal of Aviation Psychology 2(4):303–321.
Wiener, E., and R. Curry. 1980. Flight-deck automation: Promises and problems. Ergonomics 23(10):995–1011.