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Study Overview and Aims

Background information on the general aviation (GA) technology research programs of the National Aeronautics and Space Administration (NASA), including its Small Aircraft Transportation System (SATS) concept and plans to further it through a 5-year technology development and demonstration program, is provided in this chapter. As a key part of its SATS concept, NASA envisions small aircraft being flown between small airports in currently lightly used airspace to provide an increasingly larger share of the nation’s intercity personal and business travel. The approach taken in this study to examine the SATS concept vision and the 5-year program to advance it are then described.

BACKGROUND ON THE SATS VISION

Aviation, which had a niche role in transportation before World War II, has grown to become a central part of the nation’s transportation system, providing long-distance passenger service that links thousands of communities scattered across the United States. Perhaps more than any other mode of transportation, aviation has benefited from a constant stream of technological innovations, which at times have had revolutionary effects on air travel. Only 25 years passed between Charles Lindbergh’s 33-hour transatlantic flight in 1927 and the introduction of the first commercial jet airliner, the De Havilland Comet, in 1952. The larger, faster, and better-designed passenger jets that followed the Comet dramatically increased travel speeds, cutting the time of transcontinental flights by more than half. Between 1955 and 1970—the year after Boeing introduced the 550-seat 747 “jumbo” jetliner—the number of passengers flying on U.S. airlines more than quadrupled, from 40 million to nearly 175 million per year as the jet age took hold (TR News 1996). A decade later, air travel was transformed again by economic deregulation of the airline industry. Now free to extend and reconfigure their route systems, airlines formed hub-and-spoke networks, offering many more flights between many more cities. The number of air travelers increased sharply beginning in the 1980s, and any visions of the wide-body jetliner coming to dominate transcontinental passenger service ended abruptly as airlines shifted to smaller narrow-body jets better suited to short and medium-length domestic hub-and-spoke routes.

By and large, the revolutions in air transportation have been unanticipated, often the culmination of many technological advances interacting and coinciding with economic, demographic, and political developments. The jet engine, which was developed for military use during the 1930s and 1940s, became practical for commercial



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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 1 Study Overview and Aims Background information on the general aviation (GA) technology research programs of the National Aeronautics and Space Administration (NASA), including its Small Aircraft Transportation System (SATS) concept and plans to further it through a 5-year technology development and demonstration program, is provided in this chapter. As a key part of its SATS concept, NASA envisions small aircraft being flown between small airports in currently lightly used airspace to provide an increasingly larger share of the nation’s intercity personal and business travel. The approach taken in this study to examine the SATS concept vision and the 5-year program to advance it are then described. BACKGROUND ON THE SATS VISION Aviation, which had a niche role in transportation before World War II, has grown to become a central part of the nation’s transportation system, providing long-distance passenger service that links thousands of communities scattered across the United States. Perhaps more than any other mode of transportation, aviation has benefited from a constant stream of technological innovations, which at times have had revolutionary effects on air travel. Only 25 years passed between Charles Lindbergh’s 33-hour transatlantic flight in 1927 and the introduction of the first commercial jet airliner, the De Havilland Comet, in 1952. The larger, faster, and better-designed passenger jets that followed the Comet dramatically increased travel speeds, cutting the time of transcontinental flights by more than half. Between 1955 and 1970—the year after Boeing introduced the 550-seat 747 “jumbo” jetliner—the number of passengers flying on U.S. airlines more than quadrupled, from 40 million to nearly 175 million per year as the jet age took hold (TR News 1996). A decade later, air travel was transformed again by economic deregulation of the airline industry. Now free to extend and reconfigure their route systems, airlines formed hub-and-spoke networks, offering many more flights between many more cities. The number of air travelers increased sharply beginning in the 1980s, and any visions of the wide-body jetliner coming to dominate transcontinental passenger service ended abruptly as airlines shifted to smaller narrow-body jets better suited to short and medium-length domestic hub-and-spoke routes. By and large, the revolutions in air transportation have been unanticipated, often the culmination of many technological advances interacting and coinciding with economic, demographic, and political developments. The jet engine, which was developed for military use during the 1930s and 1940s, became practical for commercial

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 use by the early 1950s. However, many other technological advances had to occur during this period to enable the transformation to the jet age, such as stability augmentation systems and the adoption of swept-wing designs. The shift in U.S. population westward spurred demand for faster transcontinental airline service, making private investment in more expensive jet airliners feasible. Likewise, the revolution in airline operations that followed industry deregulation in the 1980s coincided with a revolution in computing and information technologies, allowing the development of equipment management, scheduling, and computer reservations systems that made the operation of complex hub-and-spoke networks much more practical and efficient. The technological advances and innovations in air transportation, and aviation in general, have emerged from a mix of military, industrial, university, and other public and private sources. NASA and its predecessor organization, the National Advisory Committee for Aeronautics, have made many significant contributions to aviation’s advancement, from more efficient wing and airframe designs obtained from years of aerodynamics and structures research to occupant protection improvements obtained from crash studies.1 NASA analytical tools and test facilities, such as wind tunnels, simulators, and acoustic laboratories, have provided valuable data for designing safe, efficient, and environmentally acceptable aviation systems. NASA continues to have a prominent role in the advancement of aeronautics research and technology. Much of its research is aimed at developing capabilities that can be applied to many different classes and configurations of aircraft. For example, NASA researchers are working on ways to improve icing detection and mitigation, engine and airframe material durability, and the fuel efficiency of wing designs. Through its aviation safety and weather information programs, NASA is seeking to develop more effective pilot training procedures and aids, improved tools for turbulence forecasting, and materials and technologies that reduce the incidence and severity of postcrash fires. In recent years, NASA has identified several goals to help guide and inspire its aeronautics research programs:2 Reduce the aircraft accident rate by a factor of 5 within 10 years and by a factor of 10 within 25 years. Reduce oxides of nitrogen emissions of future aircraft by 70 percent within 10 years and by 80 percent within 25 years, and reduce carbon dioxide emissions of future aircraft by 25 percent and by 50 percent in the same time frames. Reduce the perceived noise levels of future aircraft by a factor of 2 (10 decibels) within 10 years and by a factor of 4 (20 decibels) within 25 years. Reduce the cost of air travel by 25 percent within 10 years and by 50 percent within 25 years. Double the capacity of the aviation system within 10 years and triple its capacity within 25 years. 1 For examples of NASA research and technologies used in at least one aviation sector, GA, see Appendix C, General Aviation Task Force Report, prepared for NASA, September 1993. 2 See www.aerospace.nasa.gov/goals/ra.htm.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 Reduce door-to-door travel time by half within 10 years and by two-thirds within 25 years. Reduce transcontinental travel time by half within 25 years. Whether or not these ambitious goals can be achieved as targeted, NASA’s research and technology programs are undoubtedly contributing toward the overall objective of improving aviation capacity, efficiency, safety, and environmental compatibility. As is often the case with research, however, progress in accomplishing these goals can be difficult to perceive when the potential systems in which they may be used are so diverse. NASA has thus sought to organize some of its research activities around specific segments of aviation, including GA. NASA’s General Aviation Program Office works closely with GA manufacturers, suppliers, and users to better understand their research and technology needs and to find opportunities for NASA to help meet them. GA Research at NASA The civil aviation sector consists of two major components: commercial aviation and GA. Commercial aviation comprises mainly scheduled airlines and charter operators, which carry most of the passengers and cargo moved by air. Nearly all the country’s large civilian jets are operated by commercial airlines, which provide for-hire passenger and freight transport services. Aircraft used for all other purposes—such as recreational flying and corporate jet travel—are classed as GA. GA is the oldest segment of aviation, predating scheduled air service by more than two decades. Beginning in the early 1980s, however, the GA industry in the United States experienced a sharp and sustained drop-off in demand for new aircraft, especially smaller piston-engine aircraft normally used for personal flying. Some longstanding GA aircraft manufacturers, such as Piper Aircraft, went out of business, while many others dramatically changed their product lines, shifting away from piston-engine airplanes to turboprops and jets used for corporate travel and commercial applications. The causes of this decline, occurring during a period of increased air passenger travel generally, have engendered much debate. Changes in tax laws, attrition among private pilots trained during World War II, and high product liability costs are often cited. Another cause cited is that the GA industry had become stagnant technologically. Many aircraft manufactured in the 1970s and 1980s were based on designs that were two to three decades old, having been modified only slightly over time. Concern over the magnitude of the decline in demand for small private aircraft during the 1980s and 1990s prompted concerted efforts by the public and private sectors to enhance the utility and appeal of GA aircraft. In passing the General Aviation Revitalization Act of 1994, Congress sought to reduce the cost of producing GA aircraft by limiting manufacturer liability. To boost demand further, the GA industry began sponsoring national programs to promote GA flying for business and recreation.3 NASA then began to examine how its own research and technology programs 3 For instance, see “Be-A-Pilot” Foundation (www.beapilot.com), which is aimed at encouraging more student pilots and is sponsored by GA flight schools, manufacturers, and industry associations.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 could aid GA. At the time, NASA was sponsoring work on cockpit systems intended to be more user oriented; low-cost aircraft design and manufacturing methods; and propulsion systems that are quiet, produce less exhaust emissions, and provide a comfortable ride. The application of these advances to GA, however, had been given little direct consideration. NASA convened a General Aviation Task Force to advise on ways to better coordinate and target research to the benefit of the GA sector. Composed mostly of GA aircraft manufacturers, the task force noted that NASA had long worked with the Federal Aviation Administration (FAA), other public agencies, and private industry and universities to meet civil aviation needs—for instance, by seeking to enhance aviation safety, reduce aircraft noise, and increase the capacity of the airspace system. It urged NASA to undertake more focused research on aerodynamics, propulsion, flight systems, and materials and structures that have the potential for application in smaller, less expensive GA aircraft. It also urged NASA to make available its tools and test facilities to the GA community and to work more closely with GA manufacturers and suppliers through public-private R&D partnerships.4 In response to these recommendations, NASA’s General Aviation Program Office created two new public-private partnerships—the Advanced General Aviation Transport Experiments (AGATE) program in 1995 and the General Aviation Propulsion (GAP) program in 1996. AGATE members, including more than 70 companies, universities, industry associations, and state aviation departments, have shared expertise and resources to develop affordable new airframe and avionics technologies for small airplanes, enhanced certification and manufacturing processes, improved weather information and navigation displays, and easier-to-operate flight controls. GAP participants have likewise shared public- and private-sector expertise and resources in an effort to improve the reliability and maintainability of reciprocating engines and develop lower-cost turbine propulsion systems. Both of these consortia were created for a fixed period of 5 years and are now nearing completion with some notable accomplishments, such as the development of a lightweight turbofan engine that offers the potential for high thrust with low emissions and fuel consumption.5 The purpose of having a fixed program life was to help turn around the nation’s GA industry by focusing activities on those technologies with the potential to be commercially viable within a short time frame. NASA’s longer-range goal in establishing the partnership programs was to lay the groundwork for a technological revolution that would transform the GA industry into a central element of the nation’s transportation system. Genesis of the SATS Concept The promise of technological advances making small aircraft safer, easy to operate, and more affordable for transportation dates back to the “auto-planes” that were conceived even before World War II. Yet, the fact that widespread public use of small aircraft has not emerged as anticipated can be traced to many factors—among them the flexibility and cost advantages provided by the automobile and airlines for most 4 See pp. 4–5, General Aviation Task Force Report, September 1993. 5 See Williams International’s FJX-2 turbofan engine at www.williams-int.com.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 trips, the reluctance of many people to fly in small aircraft because of safety concerns, and an inability to devote the time and resources necessary to learn how to pilot small aircraft and to maintain skills. Many of the technological advances that have made large aircraft more efficient and safer for passenger transportation—from inertial guidance systems to fully coupled autopilots—have not filtered down to the smaller GA aircraft used for personal and recreational flying, largely because of the high costs associated with acquiring, maintaining, and learning how to use them. Thus, NASA set forth as central goals of both the AGATE and GAP programs not only the development of affordable advanced technologies, but also the development of a whole new generation of small aircraft that are less expensive to manufacture, maintain, and fly than are small aircraft today. AGATE was charged with developing more efficient small aircraft manufacturing processes and low-cost materials, as well as faster and less expensive means of training private pilots and maintaining proficiency. GAP was charged not only with developing more reliable and quieter small aircraft propulsion systems, but with developing systems that are much less expensive to build, maintain, and operate than those used by existing small aircraft. Indeed, AGATE first conceived of a small aircraft transportation system as a “decision-making framework” for its research and technology planning. AGATE planning documents6 describe the following key goals that would need to be achieved for advanced small aircraft to become practical and popular for use in personal and business transportation: Safety rates comparable with those of commercial airlines, Portal-to-portal costs and times per trip that are competitive with those of cars and airlines for mid-range travel, Operational reliability similar to that of cars, Availability in low-visibility conditions through the GA infrastructure, Complexity of operations and time and cost to achieve operator proficiency that are commensurate with a cross section of user abilities and needs, and Features that increase the comfort of travel to a level comparable with travel by automobile and airline. Recognizing that two 5-year R&D programs focused primarily on vehicle technologies could make only limited progress toward such far-reaching goals, NASA and other AGATE and GAP participants began discussing ways to further the SATS concept and build acceptance by FAA, the broader GA community, and state and local transportation officials. NASA’s General Aviation Program Office devised a “General Aviation Road Map” laying out a 25-year strategy for the development of a national small aircraft transportation system through a series of public and private partnerships.7 The early (10-year) goal would be to make conventional GA safer, more reliable, and more 6 See pp. 6–9, “Small Aircraft Transportation System Concept Document,” AGATE, Reference No. WP12.0-1200070-065, July 1996. 7 General Aviation Road Map, document presented to study committee by B. Holmes, NASA General Aviation Program Office Manager, June 7, 2000.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 useful through improvements in small aircraft avionics, airframes, pilot training, navigation and control systems, and engine technologies. The longer-range (25-year) goal would be to create new markets for small aircraft by developing and integrating features and capabilities that make small aircraft safer, more affordable, and easier to operate. In particular, NASA envisioned flights of advanced, self-piloted small aircraft between the thousands of GA airports located across the country, using the nation’s uncontrolled airspace. This system, NASA postulated, could reduce congestion and delay in the commercial air transportation system and greatly expand travel options for people and businesses located in communities without convenient access to commercial air services (SAIC 2001). To better understand the opportunities and challenges facing this transportation system vision, NASA commissioned a series of precursor studies of possible economic, engineering, environmental, and other issues likely to affect the development and introduction of SATS. As a guide for these studies, NASA developed a SATS Operational Concept, which defined desirable characteristics of a mature small aircraft transportation system 25 years hence. The kinds of capabilities that NASA envisioned for SATS and how these capabilities would be applied are portrayed in Box 1-1, which is derived from the Operational Concept. The precursor studies were completed between 1999 and 2001, as NASA sought congressional funding for a 5-year program to advance the concept by developing and demonstrating key airborne technologies for the precision guidance of small aircraft at small airports. The topics covered in several of these initial studies, many of which evolved into exercises designed to promote the concept, are summarized in Box 1-2. In October 2000, Congress appropriated $9 million to be used for operational evaluations, or proofs of concept where operational evaluations are not possible, of four new capabilities that promise to increase the safe and efficient capacity of the National Airspace System [NAS] for all NAS users, and to extend reliable air service to smaller communities. These capabilities are: high-volume operations at airports without control towers or terminal radar facilities; lower adverse weather landing minimums at minimally equipped landing facilities; integration of SATS aircraft into a higher en route capacity air traffic control system with complex flows and slower aircraft; and improved single-pilot ability to function competently in complex airspace in an evolving NAS.8 Congress further directed NASA to undertake the program in a collaborative manner by encouraging industry and university teams to compete for awards by involving FAA aircraft certification, flight standards, air traffic, and airport personnel in planning the evaluations. It noted that NASA will “develop and operationally evaluate these four capabilities in a five-year program [with subsequent funds to be considered in future appropriation legislation] which will produce sufficient data to 8 House Report 106-988, accompanying Public Law 106-377, Departments of Veterans Affairs and Housing and Urban Development, and Independent Agencies Appropriations Act, 2001.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 Box 1-1 SATS Operational Capabilities: Concept Envisioned for 2025 (SAIC 2001) Aircraft will be capable of operating in low-visibility conditions (visibility of ¼ mile) at small, rural (nonmetropolitan) airports with runways 2,400 feet or longer and without radar cover or assistance from air traffic control towers. Aircraft will require neither ground-based navigation aids nor approach lighting. Aircraft operations will be contained within existing airport terminal areas and protection and noise exposure zones. Operations will be environmentally compatible with communities near airports. Most of the nation’s 5,000 public-use airports will be able to accommodate SATS operations. Operators will vary widely in training, experience, and capability, having skills ranging from those required to pilot an airline to those required to drive an automobile. Automation will replace human manipulation and decision making as primary control inputs, although operators will be able to exert varying degrees of control. Onboard computers will provide realistic, real-time tutorials and training, even during flight. Digital data link capabilities will provide the operator and aircraft with real-time and integrated weather, traffic, and airport information for dynamic modifications to flight plans. Interactions with air traffic management and control will be largely automated and will not require positive control. Aircraft will operate autonomously, providing guidance for self-separation from other aircraft and obstacles. SATS users will interface with air traffic services only to the extent that they operate in controlled airspace and airports. A fully digital communication system will be in place, alleviating frequency congestion difficulties. Aircraft separation and sequencing will be accomplished by interaction of aircraft systems using the Global Positioning System (GPS) and automatic dependent surveillance and broadcast messages (ADS-B). Primary navigation service will be provided by GPS at all altitudes. Terrain and obstacle databases with data up-link capabilities, automation, and intuitive displays of the information in the cockpit will aid operators in avoiding collisions. Dynamic approach procedures will be calculated by onboard computers in real time to any runway end or touchdown point. New materials and engine and airframe designs, as well as mass production of aircraft, will allow for greatly reduced aircraft acquisition, maintenance, and operating costs. Ride-smoothing and envelope-limiting protections will ensure ride comfort and safety. Aircraft will be used for on-demand and scheduled passenger transportation by individuals (owner-operators), air taxis, businesses, and corporate flight departments for trips ranging from 150 to 1,200 miles. Trips may include as many as 10 passengers, depending on aircraft size and configuration.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 Box 1-2 SATS Precursor Study Topics User needs: Researchers modeled the life-cycle cost of acquiring and operating various sizes and types of small aircraft (piston-engine, turboprop, turbofan) under different ownership (individual ownership, shared ownership leased, private) and usage (private, corporate) scenarios. Using Orlando, Florida, as a case study, they tried to assess how SATS would affect travel speeds for users and whether SATS operations would prompt delays in commercial airline service. They also sought to examine how the availability and reliability of SATS operations might compare with those of commercial airlines by comparing the number of people living within a 30-minute drive of a commercial airport in Florida with the number living near smaller, non-commercial airports. Market potential: More than 70 businesses in Virginia were queried about their potential use of SATS. Ten of the respondents were selected for further study and shown a video of the SATS concept that both explained and emphasized its positive aspects, while pointing out the problems associated with existing transportation options. The respondents were then asked to judge their potential use of a new small aircraft transportation system and their willingness to pay for it. Consequential economic benefits: An order-of-magnitude estimate of the potential national economic benefits derived from the introduction of a new small aircraft transportation system was sought. For illustrative purposes, it was estimated that if SATS increases annual growth of gross domestic product by 0.01 to 0.05 percent, national income gains on the order of $3 billion to $15 billion per year would result. Other conjectural estimates were provided for illustration. Noise effects: Two noise studies were conducted at airports in Virginia to provide benchmarks to compare noise levels around airports today with those anticipated after the introduction of a small aircraft transportation system. One, a study of Newport News/Williamsburg International Airport, concluded that GA was the dominant source of the noise footprint at the airport and that SATS aircraft, if quieter than existing GA aircraft, would likely reduce overall noise levels and be welcomed by residents. A more thorough study of Manassas Regional Airport noted that air traffic growth as a result of SATS, especially jet traffic, could raise noise levels and require abatement. However, the report also noted that as both the population near the airport and GA traffic grow, noise concerns are likely to increase, which the quiet-aircraft technologies introduced as part of SATS could mitigate.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 support FAA decisions to approve operational use of the capabilities, and FAA and industry decisions to invest in the necessary technologies.” The initial phase of the 5-year program is under way, and a plan for the staging of operational evaluations is being developed, as described in the next section. SATS 5-YEAR PROGRAM PLAN In carrying out the congressional charge, NASA intends to develop technologies and procedures that can be used to demonstrate the potential for the following four capabilities:9 Higher-volume operations at nontowered, nonradar airports; Lower landing minimums at minimally equipped landing facilities; Increased single-pilot crew safety and mission reliability; and En route procedures and systems for integrated fleet operations. NASA is seeking industry and university partners to help plan and stage the demonstrations. SATS program managers have established tentative goals to guide these plans and criteria to judge the program’s success in demonstrating each of the four capabilities. The target goals—accompanied by more ambitious “stretch” goals—and the metrics for judging the success of the demonstrations are given in Table 1-1. The target for the first capability is to demonstrate technologies and procedures that can enable at least two aircraft to operate simultaneously10 in instrument meteorological conditions—that is, during limited visibility—at an airport that does not have conventional radar surveillance or a traffic control tower for safely directing and separating aircraft. Presumably, this capability would allow minimally equipped small airports to remain open for landings and takeoffs during lower-visibility conditions and allow some small airports to handle even more flights during good weather when demand is high. For many operators of GA aircraft, the option of being able to use more airports with fewer contingencies for weather and traffic could make flying easier, safer, and more useful. In the context of an envisioned small aircraft transportation system, the ability of many airports to handle multiple operations is essential for a convenient system that encompasses most desired origins and destinations. The target for the second capability is to demonstrate technologies and procedures that can give approach and landing guidance that is nearly as reliable (in terms of weather minimums) as that provided by conventional ground-based landing systems. Presumably, this aircraft-based capability would make it possible for more pilots to fly between more airports, on a more reliable and planned basis, without the public expense of constructing and maintaining instrument landing systems and other airport-based guidance systems. Systems that employ the Global Positioning System are already being deployed that offer such capabilities, but mainly for skilled, professional pilots operating advanced aircraft at large airports. For GA pilots with more limited skills, the emergence of additional technologies that offer the ability to access more airports under more weather conditions—and be assured of this access— 9 The information in this section is derived from the SATS Program Plan, Version 8. 10 For instance, allowing one aircraft to take off while another is approaching for landing.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 Table 1-1 Goals and Objectives for NASA’s SATS Technology and Demonstration Program Objective Current Situation Stretch Goal Minimum Success Requirement 1. Higher-volume operations at nontowered, nonradar airports Current regulations and procedures require ATC to maintain “procedural separation” between aircraft in IMC in nonradar airspace, which results in one operation (in terminal airspace at landing facilities) at a time (about three landings per hour) Demonstrate the use of vehicle-to-vehicle collaborative sequencing and self-separation algorithms and automated flight path management systems to allow 10 operations at a time in nonradar airspace (about 30 landings per hour) Demonstrate the ability to eliminate “procedural separation” requirements in IMC in nonradar terminal airspace and allow two or more simultaneous operations at a time (more than six landings per hour) 2. Lower landing minimums at minimally equipped landing facilities Current airports without navigation aids or instrument approach procedures are limited to VFR minimums for ceiling and visibility, which can be as restrictive as 1,000 feet and 3 miles, respectively. Access to airports with instrument approaches (precision and nonprecision) can be limited to higher minimums Demonstrate the ability to provide near-precision approach and landing guidance that requires no new land acquisition, no approach lighting, and minimal new ground-based equipment with no ceiling requirements and a visibility requirement of ¼ mile at a currently VFR-only airport Demonstrate the ability to provide near-precision approach and landing guidance that requires no new land acquisition, no approach lighting, and minimal new ground-based equipment with minimum ceiling and visibility requirements of 200 feet and ½ mile, respectively, at a currently VFR-only airport 3. Increased single-pilot crew safety and mission reliability The current baseline is a single instrument-rated pilot flying with current instrumentation (“steam” gauges and basic radio navigation avionics) Demonstrate single-pilot precision, safety, and mission reliability equal to that of two air transport crew members with current instrumentation Demonstrate single-pilot precision, safety, and mission reliability equal to that of a single air transport pilot with current instrumentation 4. En route procedures and systems for integrated fleet operations It is not currently possible to analyze the impact of operations enabled by SATS technologies on higher en route air traffic flows or terminal airspace operations in the current NAS Show, through analysis, that operations enabled by SATS technologies have no negative impact on higher en route air traffic flows or terminal airspace operations in the current NAS Show, through analysis, the potential impact of operations enabled by SATS technologies on higher en route air traffic flows and terminal airspace operations in the current NAS NOTE: ATC = air traffic controllers; IMC = instrument meteorological conditions; VFR = visual flight rules. SOURCE: SATS Program Plan, Version 8.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 would enhance the utility of flying small aircraft. With regard to the envisioned small aircraft transportation system, the ability to reliably access many small airports helps ensure a convenient system with wide reach. The target for the third capability is to demonstrate technologies and procedures that can enable single, nonprofessional pilots to operate with a level of precision, safety, and reliability equivalent to that of a single professional pilot today using conventional instrumentation. Such an outcome, if achieved, would confer safety benefits on much of the GA community, since many GA accidents involve aircraft operated by private pilots and are caused by errors in pilot performance and decision making. In the context of an envisioned small aircraft transportation system, the achievement of this capability would bring nearer the day when more individuals will fly advanced small aircraft for their own transportation. Finally, rather than seeking to develop a specific technology or procedure to demonstrate the fourth capability, NASA will undertake a study of how the first three capabilities, if achieved, would affect aircraft operations in the higher en route air structure where most commercial airliners and private jets operate, as well as in other airspace frequented by aircraft that do not have the new capabilities. While limited use of the three operating capabilities in GA might have minor effects on the operations of commercial airliners and other nonequipped aircraft, the widespread use of these and other capabilities envisioned for SATS would raise many important questions about the integration of SATS and non-SATS users. NASA’s plan for the program consists of three phases. In the first phase, researchers will identify and develop candidate airborne technologies to achieve the desired capabilities listed above. One development project will focus on instrument panel and flight deck technologies with the potential to improve the safety and efficiency of single-pilot operations by integrating the pilot-aircraft interface and underlying flight systems using visually intuitive, multifunction cockpit displays and software-based controls. Another development project will focus on automated flight path management technologies that can make small airports easier, safer, and more reliable to use by enabling collaborative sequencing and self-separation of aircraft and conflict detection. Candidate technologies for the two projects include Self-separation and collaborative sequencing algorithms—software that allows pilots and avionics to maintain appropriate separation without controller direction; Highway-in-the-sky guidance—graphical depictions of flight path guidance for en route and terminal procedures that are intuitive to pilots; Emergency automated landing controls—computer-based flight control systems for fail-safe recovery of aircraft and occupants following pilot incapacitation or other emergency situations; and Software-enabled controls—simplified flight controls and autopilot functions integrated in graphical displays that reduce the complexity of controlling aircraft attitudes, power settings, and rates of motion, while also providing limited flight path control and compliance with clearances that ensure traffic separation. Promising technologies in each of the two projects will be screened and selected for further development using simulations, flight tests, and other means, including benefit-cost analyses.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 In a follow-up phase, the selected technologies will be integrated to demonstrate each of the capabilities requested by Congress. This initial series of demonstrations will be conducted through a combination of simulations, flight tests, and other means in the third and fourth years of the program. In the final year of the program, NASA anticipates a larger demonstration that integrates promising technologies relevant to all of the capabilities; this integrated demonstration will be staged for the public and will include flight demonstrations. Concurrent with the technology development and demonstration phases of the program, NASA plans to sponsor a series of “transportation system analyses” studies. These studies, scheduled for completion in the final year of the program, will examine the economic viability, market potential, environmental impacts, and community acceptance of a small aircraft transportation system. The results will be used to identify changes needed in regulations, certification procedures, and airport and airspace design to enable the SATS concept. During the final stages of this National Research Council study, NASA was in the process of examining proposals from four teams comprising members from the public and private sectors to develop plans for the flight demonstrations. It was also seeking a single consortium manager to act as the interface between NASA and the planning teams. STUDY AIM AND APPROACH At its most elementary level, the SATS concept is an envisioned outcome of the use of small aircraft to fly between small airports in currently uncontrolled airspace to provide a much larger share of the nation’s intercity personal and business travel than is now the case. The influence of this vision is manifest throughout the 5-year technology program. It provides inspiration for the program, compatible with NASA’s strategic goals (cited earlier) to dramatically reduce the cost of air travel; increase travel speeds; and enhance the safety, capacity, and environmental compatibility of the aviation system. It is also helpful in promoting the technology program in a competitive environment for government R&D funding. As the central element of NASA’s GA research program, the SATS vision has come to define the goals of the General Aviation Program Office. More specifically, however, the long-range SATS vision has clearly influenced the kinds of capabilities and technologies being pursued in the program. In the program plan,11 NASA states the following: The technologies targeted for development are aimed at small aircraft used for personal and business transportation missions within the infrastructure of small airports through the nation. These missions include transportation of goods and travel by individuals, families, or groups of business associates. Consequently, the aircraft are of similar size to typical automobiles and vans used for non-commercial ground transportation…. The technology investments are selected and prioritized for the purpose of trans- 11 SATS Program Plan, Version 8, p. 2.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 portation of people, goods and services…. The program focuses on airborne technologies that expand the use of underutilized airports (those without precision instrument approaches) as well as underutilized airspace (such as the low-altitude, non-radar airspace below 6,000 ft and the en route structure below 18,000 ft). Hence, NASA appears to be looking beyond early uses of the new capabilities and viewing them as components of a new and much different kind of small aircraft transportation system. Its interest in developing systems such as emergency automated landing and highway-in-the-sky guidance, which hold the promise of making flying easier for the general public, and self-sequencing and separation capabilities, which are relevant to higher-density operations at small airports, is a reflection of the program’s orientation toward the longer-term SATS vision. Absent from the program is an explanation of how these desired capabilities might prove useful to GA as it is used today, which is most likely the way it will be used in the future without the highly uncertain and ambitious SATS. Presumably, an assessment of the probability of SATS, if made, would influence the array of capabilities and technologies being pursued in the program; hence, the absence of such a probability assessment is notable. Likewise, the plan to integrate the capabilities in flight demonstrations reflects the emphasis placed on SATS as the intended outcome of the technology program. Although each capability has potential utility, the SATS vision emphasizes the integration of many capabilities in a class of aircraft. A central aim of the integrated demonstrations themselves and the involvement of industry, FAA, and state and local officials in these demonstrations is to spur interest in the concept and prompt necessary changes in certification processes, regulations, and supporting infrastructure. Indeed, a stated goal of the program is to “provide the technical and economic basis for national investment and policy decisions to develop a small aircraft transportation system,” including the “coalescing of private sector segments into SATS architectures” and “the coalescing of state authorities to support and advocate implementation of SATS technologies.”12 An important reason for taking a closer look at the merits of the SATS vision is the influence of the vision on the NASA GA technology program. Another important reason, however, is that in promoting the SATS outcome NASA anticipates large public benefits—benefits that are not self-evident and that warrant more careful consideration. NASA’s initial aim in creating AGATE was to help rejuvenate the GA industry. In establishing the SATS R&D program, NASA’s aim is much more comprehensive— to prompt the creation of a new kind of transportation system benefiting the general public. In particular, the widespread use of advanced small aircraft operating between small airports is perceived by NASA as a means of increasing overall transportation system capacity and transportation options for underserved small communities. These are the key benefits NASA anticipates from SATS; they are the justification for using government funds to develop and demonstrate technologies aimed at achieving SATS. 12 SATS Program Plan, Version 8, p. 5 (SATS Goals).

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 The aims of this study are to examine more closely the rationale for promoting and pursuing the SATS vision and to offer NASA recommendations on the suitability of this vision as a guide for research and technology programming. The study was undertaken at the request of NASA, which specifically asked the study committee to address the following questions pertaining to the SATS concept and its relevance for technology development and deployment planning:13 Do the relative merits of the SATS concept, in whole or in part, contribute to addressing travel demand in coming decades with sufficient net benefit to warrant public investment in technology and infrastructure development and deployment? What are the most important steps that should be taken at the national, state, and local levels in support of the SATS deployment? The committee interprets the first question as a request for an assessment of whether the small aircraft transportation system envisioned and being pursued by NASA is sufficiently plausible and desirable to justify a focus of government resources on development and deployment of enabling technologies and infrastructure. If the concept in its entirety does not justify such an investment, then NASA asks whether aspects of the SATS concept—assumed to mean individual capabilities and technologies—merit public investment in development and deployment. The second question, predicated on an affirmative answer to the first, asks for recommendations on steps that should be taken at various levels of government to further the advent of SATS and the development and deployment of the individual capabilities and technologies. While specific advances in technology cannot be predicted with certainty, the overall magnitude of the technological challenge ahead for the emergence of SATS can be surmised, given what is understood about the factors influencing the nature and pace of technology development and deployment in the air transportation sector. Likewise, it is possible to gain an understanding of the practical challenges facing the system by examining such factors as the number, condition, and location of small airports and their ability to accommodate SATS operations and attract large numbers of users. Whether the SATS outcome holds the promise of net public benefits and is indeed desirable will depend on more than its technical feasibility and potential to meet transportation demands. This outcome must also be compatible with other public policy goals, such as ensuring transportation safety and environmental acceptability, which are key considerations in this study. REPORT ORGANIZATION The remainder of this report consists of four chapters. In the next two chapters, background and statistical information are provided; the committee’s analyses and assessment of SATS are given in the final two chapters. An overview of the aircraft, infrastructure, and use characteristics of the current civil aviation sector in the United States, including recent and emerging trends in air 13 The statement of task that contains these two questions, including several secondary questions and tasks, is provided in the report preface.

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Future Flight: A Review of the Small Aircraft Transportation System Concept - Special Report 263 transportation, is provided in Chapter 2. This information is helpful in understanding the terminology and issues covered in the report. The key capacity, service, safety, and environmental challenges facing the aviation sector today and for some time into the future are examined in Chapter 3. An appreciation of these challenges is important, because the aim of SATS is to help meet them. Although a close review of these two chapters is not essential for readers with a general understanding of the U.S. aviation and air transportation sectors, many of the statistics and findings that are cited in the later analytical sections of the report appear there. The study committee’s analyses of the SATS concept’s plausibility and desirability are described in Chapter 4. Consideration is given to the probability of NASA’s SATS vision emerging in light of what is known about (a) the influence of safety assurance requirements on aviation technology development, affordability, and deployment; (b) the physical condition and operational characteristics of the nation’s airport and airspace infrastructure; and (c) intercity travel demand and the factors that influence it. The desirability of the system and potential effects on overall transportation system capacity, accessibility, safety, and environmental compatibility are also examined. The committee’s responses to the questions and its recommendations, which are based on the findings of these analyses, are given in Chapter 5. REFERENCES Abbreviation SAIC Scientific Applications International Corporation SAIC. 2001. Small Aircraft Transportation System (SATS) Operational Concept Update. Version 4. AGATE Document NCA1-183, WBS 7. March. TR News. 1996. The Revolution in Passenger Aviation. No. 182, Jan.–Feb., p. 25.