EXECUTIVE SUMMARY

INTRODUCTION

Throughout the latter half of this century the U.S. aeronautics industry has been one of the undisputed success stories in global competitiveness. From the end of World War II into the last decade, U.S. aircraft, engines, and parts have been among the leaders of, and in most cases have dominated, both the domestic and the foreign markets for subsonic transports, general aviation, commuter, and military aircraft. The buildup of the global transportation infrastructure (i.e., airports and air traffic management systems) has also been driven by U.S. technology and products. The aeronautics industry is the largest positive industrial contributor to the U.S. balance of trade, plays a vital role in maintaining the safety and convenience of air travel throughout the world, and provides important contributions to the defense of U.S. interests. Further, U.S. aircraft are flown in even the most remote parts of the world, engendering national pride and international prestige.

The importance that foreign governments ascribe to developing their domestic aeronautics industries is evidence of the perceived benefits from a strong aircraft industry. Europe and the Pacific rim countries have spawned numerous government and industry consortia aimed at producing aircraft and components across the entire range of the market. The European consortium, Airbus Industries, has moved into second place in the market for commercial transport aircraft, while the emerging Taiwanese, Japanese, and Korean aircraft industries have begun to forge alliances with the two dominant U.S. companies, Boeing and McDonnell Douglas. Foreign interests dominate the commuter aircraft industry and are making inroads into the general aviation market. European and Far Eastern nations have begun to apply significant effort toward developing the technological base needed to compete even more effectively over the next several decades. The inference is obvious—these nations believe it is in their national interest to maintain a healthy, broad-based domestic aircraft industry.

In keeping with the charter of the National Aeronautics and Space Administration (NASA) to preserve ''the role of the United States as a leader in aeronautical technology,''1 NASA's Office of Aeronautics and Space Technology asked the Aeronautics and Space Engineering Board of the National Research Council to assist in assessing the current status of

1  

National Aeronautics and Space Act, 1958.



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Aeronautical Technologies for the Twenty-First Century EXECUTIVE SUMMARY INTRODUCTION Throughout the latter half of this century the U.S. aeronautics industry has been one of the undisputed success stories in global competitiveness. From the end of World War II into the last decade, U.S. aircraft, engines, and parts have been among the leaders of, and in most cases have dominated, both the domestic and the foreign markets for subsonic transports, general aviation, commuter, and military aircraft. The buildup of the global transportation infrastructure (i.e., airports and air traffic management systems) has also been driven by U.S. technology and products. The aeronautics industry is the largest positive industrial contributor to the U.S. balance of trade, plays a vital role in maintaining the safety and convenience of air travel throughout the world, and provides important contributions to the defense of U.S. interests. Further, U.S. aircraft are flown in even the most remote parts of the world, engendering national pride and international prestige. The importance that foreign governments ascribe to developing their domestic aeronautics industries is evidence of the perceived benefits from a strong aircraft industry. Europe and the Pacific rim countries have spawned numerous government and industry consortia aimed at producing aircraft and components across the entire range of the market. The European consortium, Airbus Industries, has moved into second place in the market for commercial transport aircraft, while the emerging Taiwanese, Japanese, and Korean aircraft industries have begun to forge alliances with the two dominant U.S. companies, Boeing and McDonnell Douglas. Foreign interests dominate the commuter aircraft industry and are making inroads into the general aviation market. European and Far Eastern nations have begun to apply significant effort toward developing the technological base needed to compete even more effectively over the next several decades. The inference is obvious—these nations believe it is in their national interest to maintain a healthy, broad-based domestic aircraft industry. In keeping with the charter of the National Aeronautics and Space Administration (NASA) to preserve ''the role of the United States as a leader in aeronautical technology,''1 NASA's Office of Aeronautics and Space Technology asked the Aeronautics and Space Engineering Board of the National Research Council to assist in assessing the current status of 1   National Aeronautics and Space Act, 1958.

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Aeronautical Technologies for the Twenty-First Century aeronautics in the United States and to help identify the technology advances necessary to meet the challenges of the next several decades. The Aeronautics and Space Engineering Board established the Committee on Aeronautical Technologies, which defined an approach to helping NASA determine the appropriate level and focus of its near-term technology development efforts to maintain a leadership role in the years 2000–2020. The Committee discussed the transportation infrastructure that would likely exist in 2020. From this, an estimate was made of the types and capabilities of aircraft required to compete in the global market in the 2000–2020 time frame. Based on these projections, the Committee identified the high-leverage technologies that offer the most significant advances in aeronautics to ensure long-term competitiveness for U.S. aircraft, engines, and components, and to enhance performance and safety in the total air transportation system. THE TECHNOLOGICAL CHALLENGE The fact that U.S. market share in aeronautics is eroding is well documented and is discussed in detail throughout this report. The ultimate cause of eroding market share is that, for a variety of reasons, foreign competitors are able to market products that have lower total ownership costs than U.S. products.2 This can be achieved, for example, through implementation of new technologies that reduce long-term operating costs, or through products that enter the market with significantly lower purchase price. This presents a challenge to the industry and to the U.S. government. U.S. aircraft, engine, and parts manufacturers must improve the quality, capability, and timeliness of their products, at reduced cost, to maintain or increase their market share. Without advanced technology, market share will certainly be lost, but advanced technology cannot, by itself, ensure competitive products. Foreign governments have undertaken determined, coordinated efforts to compete in all sectors of the market from general aviation through supersonic aircraft, and in most cases they have been successful. In terms of the current impact on the U.S. industry, this attack is most visible in the subsonic transport market that has historically been dominated by Boeing, Lockheed, and McDonnell Douglas. This segment of the market generates the highest revenues for aircraft, engine, and parts manufacturers.3 A long and successful history does not imply that there are no significant future gains to be realized. McDonnell Douglas and Boeing project a potential growth of 1 trillion passenger-miles each decade—to 2 trillion in the year 2000, and 4 trillion by 2020, most of which will be carried on advanced subsonic transport aircraft. Such estimates indicate that 2   Gellman Research Associates. 1990. An Economic and Financial Review of Airbus Industries. Prepared for U.S. Department of Commerce International Trade Administration. Jenkintown, Pa. 3   According to information published by the Aerospace Industries Association in 1991 (Aerospace Facts and Figures 91–92), subsonic transport aircraft accounted for $27.64 billion in sales in 1990 (in then-year dollars), commuter aircraft accounted for $2.81 billion, and aircraft engines (predominantly for subsonic transports) accounted for $10.73 billion.

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Aeronautical Technologies for the Twenty-First Century technical advances resulting in increased range and safety, and reduced fuel consumption, noise, and emissions can have significant effects on the competitive posture of the nation that produces them. Although increased research into advanced subsonic aircraft technologies is needed to bring about a near-term competitive advantage, without continued resources applied to the environmental and economic viability of supersonic aircraft, U.S. participation in that important future market may be forfeited. Similarly, advances in the technology of the global air traffic management (ATM) system can reduce congestion both in the air and on the ground, and make traveling by air safer and easier for everyone. NEEDS FOR THE FUTURE The Committee identified seven needs that must be addressed by the U.S. aeronautics community, including NASA, the Federal Aviation Administration (FAA), aircraft manufacturers, and air carriers, if the United States is to maintain or increase its share of the global aircraft market: lower cost and greater convenience, greater capacity to handle passengers and cargo, reduced environmental impact, greater aircraft and ATM system safety, improved aircraft performance, more efficient technology transfer from NASA to industry, and reduced product development times. Neither the Committee's charter nor its makeup allowed detailed consideration of the latter two needs, so these are not discussed in detail in this report. The remaining five are discussed below in terms of the needs of industry and the nation. Lower cost/greater convenience: Generally, people choose air travel over automobile, bus, ship, or rail because their desire for shorter trip times justifies the cost. Also, in many cases, air travel is the only choice, so that if the cost is excessive the potential traveler does not make the trip. To open new markets in developing nations and to expand current markets, the cost of the service must remain low enough to maintain that justification. Furthermore, the level of convenience of the service must not be compromised such that passengers in existing markets are driven to other forms of transportation. In short, advances in the speed, range, or payload of the various classes of aircraft must not be accompanied by large increases in cost or degradation of service. Thus, greater fuel efficiency and reduced operational costs must be vigorously pursued, and increases in airport and ATM system capacity must not come at the expense of convenience. Greater capacity to handle passengers and cargo: A major factor that may impose a ceiling on the ability of the aviation industry to respond to the growing demand for air travel is airport and ATM system capacity. Where local restrictions allow, it is simplest to build more airports and runways. However, this is not possible in most cases. Rather, to open up new markets or to expand existing markets, it is imperative that both the ATM system and the existing airports be capable of dealing with more people and packages flying on more and different kinds of aircraft. Safe reductions in aircraft separation, better real-time weather reporting, and facilities for a wide variety of long- and short-range aircraft all contribute to the

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Aeronautical Technologies for the Twenty-First Century ability to move more people and cargo through the system, and thus to the growth of both the industry and the economy. Reduced environmental impact: The impact of aircraft on the environment is a limiting factor on the growth of the industry. Aircraft noise restrictions limit the proximity of airports to major population centers, the utility of rotorcraft within cities, and the potential for supersonic flight over land. In addition, a change in the ozone level that results from the emission of nitrogen oxide and hydrocarbons by aircraft is an area of growing concern that may, in the near future, limit the number and types of aircraft that fly over the United States and other environmentally conscious countries. Greater aircraft/ATM system safety: As more planes takeoff and land each year, it is vital that the rate of accidents continues to decrease to avoid the perception that air travel is unsafe. Improved aircraft performance: Advances in performance of conventional subsonic aircraft, rotorcraft, short takeoff and landing aircraft, and supersonic aircraft will enable more viable expansion into new markets and expansion of existing routes. The Committee grouped advanced aircraft into three classes, within which recommendations were prepared that cut across specific technologies. advanced subsonic transport aircraft; high-speed civil transports (HSCTs), the next generation of supersonic transports; and short-haul aircraft (commuters, rotorcraft, and general aviation aircraft). Similarly, the Committee identified five generic disciplines that encompass the technologies that will provide the greatest overall benefit toward meeting future needs: 1. aerodynamics, 2. propulsion, 3. materials and structures, 4. avionics and controls, and 5. cognitive engineering.4 Table ES-1 relates these five disciplines to the five needs that were considered, and shows the primary benefits that will be gained from their development. THE NASA CIVIL AERONAUTICS PROGRAM In the course of this study, there was much discussion on the respective roles of government, industry, and universities in developing, verifying, and applying technology. One conclusion emerged clearly: without strong cooperation between commercial interests, universities, and government to define the technologies with the greatest potential payoff, 4   Cognitive engineering is defined as the use of knowledge developed by the information, cognitive, and ergonomic sciences to enable more effective interactions among humans, vehicle systems, and ATM systems. Among other factors, it deals with how data are presented to an aircrew to produce effective information integration and decision making. In short, cognitive engineering uses knowledge about humans and technology to increase the effectiveness of the aircrew, flight controllers, and air transportation in general.

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Aeronautical Technologies for the Twenty-First Century TABLE ES-1 Primary Benefits from Each Discipline Need Discipline Primary Benefits   Lower cost/greater convenience Avionics and control More effective crew Increased reliability Cognitive engineering More effective crew Enhanced training     Structures and materials Longer life/lower maintenance   Propulsion Lower fuel costs/reduced maintenance/higher reliability   Aerodynamics Lower fuel costs   Greater capacity Avionics and controls Global positioning (ground and air) Real-time weather alerting       Optimized traffic management       Cognitive engineering   Optimized traffic management   Reduced environmental impact Propulsion Fewer emissions   Less noise   Aerodynamics Less noise   Greater safety Avionics and controls Lowered demands on crew   Fault-tolerant systems   Cognitive engineering Reduced crew fatigue   Enhanced teamwork/crew interactions   Optimized human/machine interactions   Improved performance Propulsion Greater range and speed (reduced fuel consumption)   Aerodynamics Greater range and speed (increased lift/drag ratio)   Structures and materials Greater range and speed (lower weight)   Avionics and controls Increased reliability   and to work in a concerted fashion toward their development, U.S. standing in aeronautics will continue to erode. The government cannot adequately address the needs of industry unless industry is involved in the process from the beginning. This does not imply that industry should guide government efforts, nor does it imply that the government should be involved in choosing which technologies are most appropriate for commercial application. The Committee believes that an approach is possible wherein government agencies, universities, and commercial entities work together to define and develop the appropriate technologies without jeopardizing the autonomy of basic research or the constraints of fair trade. A good example is the Energy Efficient Engine (E3) program that began in the late 1970s in response to the energy crisis. The E3 program was a jointly funded, cooperative effort by NASA and the two largest U.S. engine

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Aeronautical Technologies for the Twenty-First Century manufacturers, which established and met an aggressive goal for improved fuel economy. Much of the technology that is currently implemented in U.S. transport engines was a result of the E3 program. The need to form stronger alliances among all members of the aeronautics community, coupled with the importance aeronautics plays in the U.S. economy, has led the committee to identify four primary recommendations regarding NASA's future in aeronautics: NASA should emphasize the development of advanced aeronautical technologies in the following order: (1) advanced subsonic aircraft, (2) high-speed (supersonic) aircraft, and (3) short-haul aircraft. Advanced subsonic aircraft will continue to provide the bulk of the future market, even if a viable HSCT is developed. The Committee strongly believes technological advances in subsonic aircraft are possible that could provide U.S. industry with a major competitive edge. At the same time, the potential future market for HSCT is significant, and NASA should continue research on noise, sonic boom, and emissions, and should be on the forefront of the technology research and development required to bring about a technically and economically viable HSCT. In short, it is vital that an appropriate balance be struck between programs with immediate benefits to the nation and those that lay the groundwork for the future. NASA should work with aircraft manufacturers, the airline industry, and the FAA to bring about major improvements in the utility and safety of the global ATM system. Everyone who flies benefits from the safety and convenience of the ATM system, and it is in the national interest for U.S. technology to continue to lead the future development of the global system. Although the FAA is the lead agency in this area, NASA has much to contribute to a coordinated, national effort that includes ground, air, and space systems. NASA should commit to a greater level of technology validation to reduce the risk of incorporating advanced technology into U.S. products. Incorporation of new technology in production aircraft is risky. The major aircraft and engine manufacturers have significant aeronautics research and technology development capabilities, but they do not have the resources to engage in nonspecific, precompetitive research. Most major universities have facilities and talented people, but they are not equipped, staffed, or funded to perform the range and scope of validation that is required before industry can make effective use of a given technology. The FAA has capabilities to perform applied research, but its focus is regulatory in nature and not aimed at providing a competitive edge. Only NASA combines talent and experience in aeronautics research with a nationwide network of test facilities and research aircraft. Thus, NASA is the only organization in the United States with both the capability and the mandate to perform the basic research as well as the ground and

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Aeronautical Technologies for the Twenty-First Century flight testing necessary to validate new concepts to the extent that they can begin to be incorporated into commercial aircraft. Although it is not NASA's role to be concerned with specific, product-oriented applications, to ensure a smooth transition of generic technologies into such applications, joint efforts among NASA, industry, and academia can improve the rate at which technology is validated for use. The magnitude of NASA's civil aeronautics budget should be increased. The attention paid to civil aeronautics in the NASA budget is not commensurate with the importance the industry plays in the nation's economy. This is particularly true, in the opinion of the Committee, when the NASA aeronautics budget is compared to its space research and development budget.5 When new aircraft begin to enter service in the next century, whatever their configuration, the contribution to the U.S. economy from their manufacture and operation will continue to meet or exceed even the most significant contributions from space-related activities. Thus, the development of technologies to help make U.S. aeronautical products more competitive, and air travel safer and more convenient in the next century requires, and deserves, increased attention. Accordingly, the Committee further recommends that the Office of Aeronautics and Space Technology (OAST) perform a review of its budget in light of the technologies discussed in this report and determine the level of funding appropriate to NASA's role in helping to offset the erosion of U.S. standing in the global market and to position the United States to capture future markets. OAST should report the results of its budget review to the NASA Administrator for review and consideration of the total program balance. In most cases, the technologies recommended in this report represent areas in which NASA has existing programs. Where possible, the Committee has identified these existing programs and recommended that they be enhanced as appropriate. In some cases, however, the recommended technologies require new starts or restarts of old programs. The Committee has also attempted to identify proposed new programs wherever possible. Tables ES-2 and ES-3 show the current (1992) NASA aeronautics budget (also see Chapter 1 and Appendix C). Chapter 1 of this report includes a discussion of the relative funding of each vehicle class and discipline shown in Tables ES-2 and ES-3. The Committee believes that the relative funding shown in Tables ES-2 and ES-3 is generally appropriate given the challenges identified in this report, with two exceptions. First, as mentioned above, the Committee believes that research into advanced subsonic aircraft should be emphasized relative to other classes of civilian aircraft. This is not currently the case. If the civilian portion of NASA's aeronautics budget is increased as the Committee has recommended, the portion devoted 5   According to information published by the Aerospace Industries Association in 1991 (Aerospace Facts and Figures 91–92), and the U.S. Commerce Department (Space Business Indicators, 1992) civil space sales accounted for approximately $3.4 billion in 1990, while NASA devoted nearly $5.1 billion to space-related research and development. Shipments of civil aircraft, engines, and parts accounted for more than $33 billion in 1990, whereas the 1990 NASA budget devoted only $0.889 billion (including research into military aircraft, construction of facilities, and research and operations support) to aeronautics research and development.

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Aeronautical Technologies for the Twenty-First Century TABLE ES-2 NASA Research and Development Funding Mix (1992)   1992 Research and Development Program Funding (millions of 1992 dollars, percent of total funding)a,b Category Research and Technology Basec Systems Technology Programsd Total Advanced subsonic transport aircraft 48.6 8.5% 44.9 7.8% 93.5 16.3% High-speed civil transport 6.3 1.1% 86.5 15.1% 92.8 16.2% Short-haul aircraft 23.8 4.1% 8.2 1.4% 32.0 5.6% Critical disciplinese 140.6 24.5% 62.4 10.9% 203.0 35.4% Hypersonic/transatmos. technologyf 30.2 5.3% – – 30.2 5.3% High-performance aircraftg 111.6 19.4% 11.1 1.9% 122.7 21.3% Total 361.1 62.8% 213.1 37.2% 574.2   Source: NASA Office of Aeronautics and Space Technology. a Research and development funding only. Excludes wind tunnel refurbishment ($62.8 million) and other construction of facilities funding ($22.9 million), as well as research and operations support ($210.1 million). b Percentages are based on the total ($574.2 million). Percentages may not add to 100% due to roundoff error. c The research and technology base includes efforts in all aeronautical disciplines: aerodynamics; propulsion and power; materials and structures; controls, guidance, and human factors; systems analysis; and flight systems. d Systems technology programs are technology and validation efforts aimed at specific vehicle or component applications. e This category includes research and technology development in the traditional aeronautical disciplines that is not aimed at specific vehicle or component applications, or that applies to all vehicle classes. f This category is primarily made up of the National Aerospace Plane Program (NASP). g This category is made up of research that applies to high-performance military aircraft. NASA receives no funding from the Department of Defense for this research.

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Aeronautical Technologies for the Twenty-First Century TABLE ES-3 1992 NASA Aeronautics Funding by Discipline.   1992 Research and Development Funding (millions of 1992 dollars, percent of total funding)a,b Discipline Advanced subsonic transport aircraft High-speed civil transport Short-haul aircraft Critical disciplinesc Hypersonic/transatmos. technologyd High-performance aircrafte Total Aerodynamics 12.9 2.2% 2.1 0.4% 16.5 2.9% 93.6 16.3% 12.6 2.2% 33.9 5.9% 171.6 28.1% Propulsion 16.8 2.9% 19.4 3.4% 3.0 0.5% 31.4 5.5% 11.6 2.0% 29.8 5.2% 112.0 19.5% Materials and structures 28.1 4.9% 10.1 1.8% 3.3 0.6% 30.1 5.2% 3.1 0.5% 1.4 0.2% 76.1 13.3% Controls, guidance, & human factorsf 29.4 5.1% 0.7 0.1% 3.3 0.6% 25.8 4.5% 1.3 0.2% 3.9 0.7% 64.4 11.2% Systems and operationsg 2.3 0.4% 0.6 0.1% 5.9 1.0% 5.1 0.9% 1.6 0.3% 53.7 9.4% 69.2 12.1% Environmental Compatibility — — 59.9 10.4% — — — — — — — — 59.9 10.4% Otherh 4.0 0.7% — — — — 17.0 3.0% — — — — 21.0 3.7% Total 93.5 16.3% 92.8 16.2% 32.0 5.6% 203.0 35.4% 30.2 5.3% 122.7 21.4% 574.2   Source: NASA Office of Aeronautics and Space Technology. a Research and development funding only. Excludes wind tunnel refurbishment ($62.8 million) and other construction of facilities funding ($22.9 million), as well as research and operations support ($210.1 million). b Percentages are based on the total ($574.2 million). Percentages may not add to 100% due to roundoff error. c This category includes research and technology development in the traditional aeronautical disciplines that is not aimed at specific vehicle or component applications, or that applies to all vehicle classes. d This category is primarily made up of the National Aerospace Plane Program (NASP). e This category is made up of research that applies to high performance military aircraft. NASA receives no funding from the Department of defense for this research. f This category includes the disciplines identified in this report as avionics and controls, and cognitive engineering. g The category includes both flight systems research and systems analysis studies. h The advanced subsonic transport category includes $4 million for aging aircraft, and the critical disciplines category includes $17 million for high-performance computing.

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Aeronautical Technologies for the Twenty-First Century to advanced subsonic transport aircraft should garner a substantial fraction of that increase in comparison with other vehicle classes. If the NASA budget remains at current levels, the Committee believes that resources should be shifted from areas that are less vital to the nation's economy into technology development for aeronautics, particularly for advanced subsonic transport aircraft. Second, the Committee believes that NASA's current emphasis on rotorcraft in the short-haul category should be balanced with additional funding for general aviation and commuter aircraft or, if new sources of funding cannot be found, there should be a reallocation of resources from rotorcraft to conventional short-haul aircraft. Although the Committee was not asked to address the source of additional funding or reallocation of existing funding, it cannot be ignored that reallocation of military or space-related resources may be an option for increasing civil aeronautics' funding if sources outside of NASA cannot be found. This, however, is a matter for NASA and policy makers within the government to determine. AIRCRAFT OF THE FUTURE The following discussion summarizes issues that are treated in detail in the body of the report. The recommendations are labeled "general" and "specific" to distinguish between those that pertain to the overall direction of research and technology development and those that relate to specific programs. The specific recommendations pertain to existing programs that the Committee believes should be enhanced and new efforts that should be undertaken. The recommendations are listed in order of importance. Advanced Subsonic Aircraft The following recommendations pertain to NASA's approach to developing technology and its potential interactions with industry to ensure that the proper technologies are advanced. General Recommendation: NASA should increase its investments in research and technology development to support future subsonic transports to reflect the importance of this segment of the market. Specific Recommendation: NASA should plan and execute a major technology development and validation activity for advanced subsonic transports that is more extensive than that proposed for the HSCT program. This should include improvements in operational performance of subsonic transport aircraft; and

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Aeronautical Technologies for the Twenty-First Century complementary, cohesive, long-term cooperation with academia and industry.6 High-Speed Civil Transports Although the potential market for HSCT appears to be significant, there are scientific and technological barriers to the development of an economically viable HSCT. These technical barriers include the need to better understand the effects of engine emissions on atmospheric phenomena and the level of sonic boom that can be tolerated over populated areas, if such a level exists. Once these issues are better understood, engineering solutions must be developed to meet the associated restrictions. The concept of an HSCT is technically viable—the supersonic transport (SST), which was developed by the British and French in the 1970s and continues to fly a regular schedule, is evidence of that. However, although the SST is a technological success, it is an economic failure. Due, in part, to the fact that, more than 20 years after the SST was first seriously proposed, the sonic boom generated precludes it from operating over populated land areas. Furthermore, in the last decade it has become increasing clear that the ozone-depleting emissions from a fleet of supersonic transports could do significant damage to the environment, thus precluding wide-scale operation of a U.S. HSCT. In short, the Committee believes the issues of sonic boom generation over land and ozone depletion must be adequately addressed before a major design and development effort is undertaken for an HSCT. This leads to the following recommendations: General Recommendation: NASA should be the primary contributor to technologies that identify and reduce the environmental impact of HSCT, including ozone depletion, airport noise and emissions, and sonic boom. Specific Recommendations: NASA should enhance its atmospheric research program to determine whether acceptable levels of ozone-depleting emissions from HSCT exist. If they exist, NASA should perform the necessary propulsion research and validation to meet those levels. NASA should continue its work toward advances in HSCT propulsion technology that reduce noxious emissions and engine noise. 6   According to NASA's Office of Aeronautics and Space Technology, the current proposed funding for Phase 2 of the High-Speed Research (HSR-2) program is $1.233 billion over the years 1994–2000. This funding level includes $549 million for airframe-related technology, $569 million for propulsion technology, and $115 million for flight-deck systems.

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Aeronautical Technologies for the Twenty-First Century The HSCT program should be tailored to ensure that propulsion, aerodynamics, structures and materials, and overall vehicle management and control technologies are adequately represented. Although industry is not currently planning HSCT supersonic flights over populated areas, NASA should continue an aggressive program to define acceptable sonic boom levels and should continue its program to investigate approaches to meeting those levels. Short-Haul Aircraft Given the projected increase in congestion at hub airports, commuter aircraft and rotorcraft will be used increasingly over the next several decades, and the market that bypasses major hubs is likely to expand. Furthermore, a significantly enhanced ATM system will likely reduce the difficulty in obtaining and maintaining the skills needed for a private pilot's license, which will spark an increase in general aviation traffic over the next several decades. In other words, short-haul aircraft will continue to be an indispensable segment of the market and so deserve adequate attention. The following recommendations pertain to NASA's efforts to incorporate short-haul aircraft into its overall aeronautics program: General Recommendation: NASA should enlarge its support of the key technologies for general aviation, commuter aircraft, and rotorcraft through extensive validation, and should both sponsor and participate in comprehensive system studies to define total aircraft systems, with investigations into their technical and economic characteristics. This should include a more equal balance between rotorcraft and conventional short-haul aircraft. Specific Recommendations: NASA should undertake an aggressive safety research program focused on cognitive engineering and the features that are unique to the operation of commuter, rotorcraft, and general aviation aircraft. NASA's unique capabilities in simulation and training should be focused toward enhancing the initial training and skill maintenance programs of all aircraft pilots and mechanics. NASA's extensive capabilities in aerodynamics, structures, and acoustics should be applied toward major improvements in rotorcraft economics, speed, and efficiency. NASA and the FAA should undertake a study to establish the degree to which existing airport capacity could be increased by shifting some short-haul traffic

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Aeronautical Technologies for the Twenty-First Century to helicopters and tiltrotors, using vertiports integrated into available airport real estate. NASA should undertake an extensive research and technology development effort to improve rotorcraft passenger comfort. ENVIRONMENTAL AND OPERATIONAL ISSUES Environmental and operational issues relate to all classes of aircraft and encompass each of the generic disciplines. NASA has a significant role to play in determining acceptable limits for the environmental impact of aircraft, defining approaches for their safe and cost-effective operation, and developing appropriate technologies. Environmental Issues The future operation of all aircraft classes will be increasingly constrained by a complex system of national and international restrictions on both noise and emissions. Without significant effort to make U.S. aircraft less intrusive, substantial competitive advantage may be forfeited. The following recommendations address the issues involved in reducing the environmental impact of aircraft in an effort to focus NASA's ongoing noise and atmospheric research programs. General Recommendation: NASA, the U.S. aircraft industry, and the FAA must work together to address national and international environmental concerns both to help the United States gain a competitive edge and to avoid increasing the adverse environmental effects of aircraft on the ground and in flight. Specific Recommendations: Current and proposed research programs sponsored by NASA should be continued to enhance understanding of the impact of engine emissions on atmospheric ozone. It is imperative that improved modeling, data collection, and verification of models of the chemistry and dynamics of the troposphere also be included in NASA's long-term subsonic aircraft program. NASA is strongly encouraged to investigate worst-case scenarios for stratospheric ozone depletion to establish a basis for reasonable regulation aircraft emissions and to begin developing engineering solutions.

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Aeronautical Technologies for the Twenty-First Century To enable a successful commercial HSCT fleet, NASA must continue or accelerate its current programs in advanced emission reduction technology related to the chemistry and dynamics of the stratosphere. NASA's aggressive research and development program for aircraft noise reduction must include HSCT jet engine noise suppression, subsonic engine fan noise suppression, airframe noise reduction, and noise abatement flight operations. NASA should continue its research and development program in sonic boom reduction for HSCT. Operational Issues There are increasingly serious constraints on the movement of all classes of aircraft at many U.S. airports, and the condition is as bad, or worse, in Europe and the Far East. The problem lies in the limited capacity of airports to accommodate aircraft on the ground, the limited capacity of the air traffic management system to accommodate aircraft in the air, and the difficulties in integrating the two. Unfortunately, opportunities to expand existing facilities will be severely limited in the future. Thus, the best hope for addressing the problem of congestion over the long-term is through the application of advanced technology to develop new airport and air traffic management systems. The following recommendations address the issues of capacity and congestion as they relate to airport systems and to current and future ATM systems. General Recommendation: Coordinated activity should be undertaken between NASA and the FAA to significantly increase the capacity of the worldwide aviation system, beginning with the U.S. domestic ATM system. Specific Recommendations: NASA should increase its current cooperative effort with the FAA, the airlines, and aircraft manufacturers to bring about implementation of the Global Positioning System (GPS) for use in the ATM system as soon as possible. NASA should focus its efforts, in cooperation with the FAA and industry, to expedite full integration of on-board communication, navigation, and flight management systems;

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Aeronautical Technologies for the Twenty-First Century control and standardization of software for both on-board and ground-based computer systems; development of a mission monitor to address any unacceptable developments that occur on-board the aircraft, in the satellite system, or in the communication system, whether in flight or on the ground; development of a satellite communication system along with a global infrastructure to ensure clear and redundant communications; and refinement of inertial navigational systems, including the use of fiber optics. AERONAUTICAL DISCIPLINES The generic disciplines are discussed below. The Committee believes that some discussion of the emerging field of integrated design is also warranted. The increasing maturity of computational approaches in various disciplines provides new opportunities to couple the disciplines early in the design process. Routinely treating aerodynamics, structures, propulsion, and controls virtually simultaneously and continuously throughout each step of the design has large payoffs. Although the Committee has no specific recommendations in this area, it hopes that continued attention will be paid throughout the community to enhancing the scope and utility of integrated design techniques. The following sections discuss the key technological concepts in each discipline and present recommendations for focusing NASA's efforts in the near-term to ensure long-term results. Aerodynamics The aerodynamics discipline encompasses a wide range of analytical and computational technologies, as well as design and test facilities. NASA, and the National Advisory Committee for Aeronautics before it, traditionally served as the focal point for civilian aerodynamics research and validation in the United States. Such a focus is needed if the United States is to remain at the forefront of research in aerodynamics. The following recommendations reflect the Committee's concerns about the level of technology validation that is performed in this discipline and include several specific areas in which NASA should enhance its capabilities. General Recommendation: NASA must continue to provide the necessary resources for aerodynamics research and validation, including resources focused on specific key technologies, resources to maintain and enhance ground and flight test facilities, and resources for enhanced analytical and design capabilities.

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Aeronautical Technologies for the Twenty-First Century Specific Recommendations: The following research topics are of vital importance to NASA's research effort in aerodynamics. (The order of importance is strongly dependent upon industrial marketing decisions in the next decade.) aerodynamic cruise performance, including subsonic and supersonic laminar flow control technology; aircraft propulsion/airframe integration for both subsonic and supersonic aircraft; low speed and high lift for subsonic configurations, including wake mechanics, wake vortex, and measurement technology; computational fluid dynamics for aircraft design, including validation of codes; low speed and high lift for supersonic configurations; and aerodynamics of rotorcraft. In order of importance, the following should be the focus of a program to enhance NASA's ground-based experimental facilities: revitalization of existing facilities on an expedited basis; establishment of an intensive program to develop high-resolution nonintrusive instrumentation; fitting of the 40' x 80' tunnel at the Ames Research Center with acoustic lining; development of a low-speed (Mach 0.1–0.5), low-disturbance test capability to operate at chord Reynolds numbers in excess of 50 million; and research to examine the feasibility of a supersonic (Mach 2–6) low-disturbance test capability to operate at full-chord Reynolds numbers of 400 million to 500 million. In order of importance, the following should be the focus of a program to enhance NASA's experimental flight facilities: revitalization of flight research capability and in-flight technology validation efforts in all speed regimes; and development of advanced measurement technologies for flight research.

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Aeronautical Technologies for the Twenty-First Century Propulsion Propulsion technology offers the greatest single contribution to improvement of the cruising economy of aircraft and to lessening their environmental impact. The past three generations of gas turbine engines, for example, have seen increased turbine inlet temperatures, increased compressor pressure ratio, increased bypass ratio, and improved fan and nacelle performance, all leading to greater thrust-to-weight ratios, reduced fuel consumption, reduced noise and emissions, and improved reliability. The following recommendations reflect the Committee's belief that this rapid pace can be maintained over the next two decades, thus providing superior propulsion systems well into the next century. General Recommendation: NASA must vastly strengthen its current propulsion technology program to include: much greater emphasis on subsonic transport propulsion systems where the United States has lost its technological edge over foreign competitors; continued support for the HSCT propulsion program; and a strong, broad-based propulsion technology program to position the United States for the post-2000 short-haul markets, including a better balance between vertical takeoff and landing commuter systems and conventional systems. Specific Recommendations: NASA should increase its support for generic computational and experimental propulsion research. In addition, NASA must lead in the development of technical communication with industry in computational science applied to propulsion. NASA should take the initiative in setting up a joint NASA/industry program for innovative subsonic propulsion technology that is at least equivalent to the NASA/industry HSCT propulsion program. NASA must increase its support for the development of specialty materials not currently available as commodities that, if properly developed, will become common in aircraft engines. The basic research effort at the Lewis Research Center (LeRC) in low nitric oxide combustors for the HSCT has produced excellent results and the momentum should be maintained. NASA should put in place the planned Joint Technology Acquisition Program between LeRC and industry. NASA should take advantage of its unique position to mount a substantial program in active control technologies for aircraft engines.

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Aeronautical Technologies for the Twenty-First Century NASA's turbomachinery research program, should be strengthened to the point at which NASA can recapture its leadership role. NASA's LeRC should direct increased effort toward the enabling technologies in compressor, combustor/turbine, and control accessories for engines appropriate to short-haul aircraft. Materials and Structures Structural weight is the single largest item in the empty weight of an aircraft and is, therefore, a major factor in the original acquisition and operating costs. The durability of the materials used affects both maintenance costs and useful lifetime of the aircraft. Advanced materials and innovative structural design concepts hold the promise of reducing overall structural weight while maintaining strength, stiffness, and durability. NASA has a long history in developing innovative structural and materials concepts that have found wide application in both commercial and military aircraft. However, it takes a great deal of time to build the experience base that is needed to establish confidence in new materials and structural concepts. On one hand, commercial interests are unlikely to aggressively pursue the incorporation of new structures into their airframes or engines until this confidence has been built but, on the other hand, they lack the time and resources required to build that base of operational experience. Thus, in its development of new materials and structural concepts, NASA must include extensive testing aimed at building confidence in them to a level at which industry can begin to incorporate them without undue risk. General Recommendation: NASA's structures and materials program should emphasize continuing fundamental research to achieve both evolutionary and revolutionary advances in materials and structures, as well as focused technology programs in materials and structures to address specific aircraft system requirements. This should include: a major role in establishing the data base that is required for realistic materials- and structures-related regulations; a significant increase in NASA's investment in the technology of shaping, forming, and fastening; and a lead role in stimulating innovative structural design and manufacturing research for both airframes and engines in a program conducted jointly with industry.

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Aeronautical Technologies for the Twenty-First Century Specific Recommendations: The highest priority in NASA's long-range engine materials research program should be on ceramic matrix composite developments including fabrication technology, although intermetallics should continue to be an active part of engine materials research for the longer term, with emphasis on improving damage tolerance. NASA's existing program of basic research in materials and structures should improve understanding of failure modes in composites, increase damage tolerance, and introduce advanced means of nondestructive evaluation. Automated sensing and feedback control should be an increasing part of NASA's research program, capitalizing on ''smart structures'' advances. The introduction of metal matrix composites into high-pressure compressor disks deserves major emphasis in NASA's engine programs for the nearer term. NASA's program of materials and structures research for the HSCT should give high priority to developing basic composite materials, advanced metallic systems, and design concepts and processing techniques for 225–375°F operations. Avionics and Controls The 1980s saw a significant change in the nature of commercial air transportation and military aircraft operations as a consequence of remarkable growth in application of new avionics. These innovations provided increased functional capability without adverse impact on the weight of aircraft. However, advances in avionics have brought a new set of problems including inadequate testing and validation to ensure that such systems meet all requirements when they are introduced, and the often massive cost and schedule overruns resulting from software development and validation problems. Further, demand has increased for coordination and standardization in areas as diverse as microwave landing systems, software standards, electromagnetic vulnerability standards, and certification and testing requirements. Current research and development in avionics and controls is expected to result in operational solutions to many of the problems anticipated because of air traffic growth. Techniques for more effective use of computer automation to manage air traffic are being developed, but integration of that technology into the national and worldwide system is a major challenge. A primary hope for meeting the challenge of increasing congestion in the air and on the ground is full-scale implementation of the GPS. Emerging technologies also offer significant enhancement of the pilot's situational awareness, which is fundamental to improved safety and mission effectiveness. NASA has a great deal of expertise in developing and validating advanced avionics and control concepts for spacecraft. Where appropriate, NASA should be aggressive in

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Aeronautical Technologies for the Twenty-First Century incorporating these concepts into research aircraft and simulator systems, in close relationship with the FAA and industry, with the goal of building an adequate experience base. The following recommendations reflect this belief. General Recommendation: NASA should play a major role in the development and validation of the key technologies in avionics and control, including system development and integration, simulator and/or experimental flight validation, and serving in a technical advisory capacity for industry and other agencies of the government. Specific Recommendations: NASA should enhance its current efforts, in conjunction with the FAA, academia, and industry, to produce advances in: flight path management; pilot/vehicle interface (i.e., establish a cognitive engineering effort in this area); avionics and controls integration; control function applications; and aircraft power and actuation. Cognitive Engineering For the next two to three decades the information sciences and human factors disciplines will play a different and more fundamental part in aeronautics than in the past. As the power of computers increases, the next step is to allow the aircrew to do what people do best and use the computer to support these activities and carry out whatever other tasks are necessary. This human-centered approach involves multidisciplinary engineering activities and is represented in this report by the term "cognitive engineering," to express the synergy between the traditional disciplines of information sciences and human factors. The recommendations for this discipline relate to two specific goals: improvement of the overall ATM system (capacity and operations) and enhancement of safety. NASA has a wide range of expertise in cognitive engineering as related to both aircraft and space systems, but NASA's current programs should be enhanced and focused to produce real improvements in flight systems. Application of this expertise to future systems, both on-board aircraft and in ground systems, will lead to safer, more convenient air travel in the next century.

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Aeronautical Technologies for the Twenty-First Century General Recommendation: NASA should expand its efforts to conduct broad-based, interdisciplinary research into the causes, nature, and alleviation of human error, with specific reference to airborne and ATM environments. The most promising theories and experiments should be pursued as part of a continuing, long-range effort aimed at accident reduction. NASA should lead in the development and validation of training and operational strategy and tactics that are intrinsically tolerant to situations demanding divided attention operations by the individual or crew. NASA should work with the FAA and industry to address the total human/system concepts and develop methods to ensure valid and reliable system operations. Specific Recommendations: NASA should conduct research to develop and demonstrate techniques to improve the pilot's situational awareness and spatial orientation. In addition to its work with the National Incident Reporting System, NASA should work with the FAA and the National Transportation Safety Board to analyze all available data on aircraft accidents and incidents to determine the history and trend of human errors, contributing factors, type of equipment involved, and other relevant matters. NASA's current research in error alleviation should be expanded to include: systems that can detect developing critical situations, independent of the crews's alertness, and inform and assist the crew regarding appropriate corrective measures; concepts, methods, criteria, and the technology for error-tolerant system design; and development of prototype, "massively smart" interfaces, both in the simulator and in the air. NASA, with FAA involvement, should extend its investigations of highly reliable avionics to total system concepts applicable to ATM automation. NASA should continue its research into four-dimensional guidance algorithms and simulation techniques for ATM.

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