The Small Aircraft Transportation System (SATS) program has been established by the Office of Aerospace Technology in the National Aeronautics and Space Administration (NASA). In the initial 5-year phase of the program, NASA is working with the private sector and university researchers, as well as other federal and state governmental agencies, to further various aircraft-based technologies that will
Increase the safety and utility of operations at small airports lacking traffic control towers, radar surveillance, or other conventional ground-based means of monitoring and safely separating aircraft traffic in the terminal airspace and on runways and taxiways;
Allow more dependable use of small airports lacking instrument landing systems or other ground-based navigation systems that are now required for many night-time and low-visibility landings; and
Improve the ability of single-piloted aircraft to operate safely in complex airspace (that is, at airports and in airways with many and diverse operators).
Guiding this program is a longer-range SATS vision of the routine use of advanced, small fixed-wing aircraft—of a size common in general aviation (GA) (4 to 10 passengers)—for personal transportation between small communities. NASA envisions tens of thousands of advanced small aircraft being used in this role. Key to this guiding vision are advances anticipated by NASA in technologies and processes that will make small aircraft much less expensive to produce, maintain, and operate; more environmentally acceptable; and much easier, safer, and more reliable to fly than are small GA aircraft today.
NASA envisions that such a transportation system, once developed and deployed, could reduce congestion and delays in the commercial aviation sector by diverting passenger traffic from large airports and could improve transportation service in many more communities by making better use of the nation’s small airports and least-traveled airways. Currently, NASA’s SATS technology research program is being justified on the basis of these anticipated benefits and the expectation that major challenges to the development and deployment of such a system—from technological and economic considerations to safety and environmental requirements— can be met.
NASA asked the Transportation Research Board to convene a study committee to review the plausibility and desirability of the SATS concept, giving special
consideration to whether its potential net benefits—from user benefits to overall environmental and safety effects—are sufficiently promising to warrant public-sector investment in SATS development and deployment (see Box P-1 of the Preface for the statement of task). The absence of credible examinations of SATS by NASA compelled the committee to undertake its own analyses of the concept’s plausibility and desirability, which are presented in Chapter 4. The committee’s conclusions and advice derived from these analyses are provided in detail in Chapter 5; they are summarized in the following paragraphs.
The committee does not share NASA’s vision for SATS, nor does the committee support the use of this vision to guide technology development and deployment investments. Numerous findings, summarized below, suggest that such a system is neither likely to emerge as conceived nor to contribute substantially to satisfying travel demand. Nevertheless, the committee endorses NASA’s efforts to develop and demonstrate technologies that can help further the highly desirable outcomes listed in the three bullets above. To help achieve these outcomes, the committee urges NASA to prioritize, without regard to the SATS concept, the capabilities and technologies now being pursued in the 5-year program according to a clearly delineated set of civil aviation needs (such as improved GA safety) that these new capabilities and technologies can help meet.
NASA has a traditional and vital role in advancing aeronautics technologies that can enhance civil aviation safety, capacity, accessibility, and environmental compatibility. Technological capabilities to reduce the probability of air traffic conflicts in more places, permit more reliable and safe operations during inclement weather at more airports, and enhance the safety of single-pilot operations could improve the safety and utility of the nation’s civil aviation system. The full-scale SATS concept, however, should not be used to guide the R&D program because it presents an unlikely and potentially undesirable outcome. Analyses of the concept suggest the following:
Limited potential for the use of SATS aircraft to be affordable by the general public. The aircraft envisioned for SATS would need to be far more advanced and sophisticated than even the highest-performing small GA aircraft of today to achieve the standards of safety, ease of use and maintenance, and environmental friendliness that would attract large numbers of users. The committee found no evidence to suggest that such aircraft could be made affordable for use by large numbers of people and businesses.
Limited potential for SATS to attract large numbers of users because of its orientation to travel markets outside the nation’s major metropolitan areas. Most people and businesses are located in metropolitan areas, which are the origins and destinations of most time-sensitive business travelers and most intercity passenger trips overall. The expectation that large numbers of people will use advanced small aircraft to fly between airports in small, nonmetropolitan communities runs counter to long-standing travel patterns and demographic and economic trends.
Limited appeal to price-sensitive leisure travelers, who use the automobile for most short or medium-length intercity trips. Most intercity travelers are highly sensitive to the price of travel, especially in the short- to medium-length trip markets
envisioned for SATS. Leisure travelers, who account for the majority of all intercity trips under 1,000 miles, usually travel by automobile, largely because of the versatility it offers and the low additional cost per passenger.
Significant obstacles to SATS deployment because of infrastructure and ancillary service limitations at small airports, as well as potential environmental concerns at such airports, including increases in aircraft noise and air pollutant emissions. Most of the country’s 5,000 public-use airports have minimal infrastructure and support services, which limits their suitability for frequent and routine transportation usage. About half of all public-use airports have a paved runway that is at least 4,000 feet long and thus potentially capable of handling small jet aircraft; yet, most of these airports would likely require further infrastructure investments.
The implausibility of expeditious and nonevolutionary deployment of SATS technologies because of technical challenges and the need for high levels of safety assurance that have been notably neglected in the SATS program. Safety is paramount in aviation, particularly for passenger transportation. Hence, any changes in aviation, from new methods of air traffic control and pilot training and certification procedures to new aircraft materials and manufacturing processes, are subject to intense and thorough safety evaluations and validations that can take much time. The idea that many nonevolutionary changes in aircraft design, propulsion, flight control, communications, navigation, surveillance, and manufacturing techniques could emerge at about the same time and be accepted as safe by users, manufacturers, insurers, and regulators is highly questionable.
A genuine potential for many undesirable congestion, safety, and environmental effects from SATS deployment. If SATS does not access major metropolitan markets, it will likely have little, if any, meaningful effect on operations at the nation’s busiest and most capacity-constrained large airports, where most delays in the commercial air transportation system occur. Yet, if SATS does access these markets, the mixing of SATS with non-SATS aircraft in heavily used, controlled airspace and airports could create significant traffic management challenges. Moreover, a well-used SATS could have negative net effects on aviation’s environmental compatibility by shifting travelers from larger aircraft, each carrying dozens of travelers, to smaller aircraft, each carrying a handful of travelers.
More generally, the committee believes that positing any such preconceived system, in which a single and definitive vehicle concept is used to guide research and development, could inhibit the evolution of alternative outcomes that may result from technological opportunities and economic and social needs. The heightened emphasis on aviation security in recent months (discussed in the Afterword to this report) is an example of how difficult it is to accurately predict change in the aviation sector. NASA’s strength in civil aeronautics is in technology research and development, and not in defining, developing, and promoting new transportation systems.
Although it does not share NASA’s vision for SATS, the committee commends NASA for using its resources and expertise to leverage and stimulate private-sector investment in civil aeronautics research and development. Indeed, it is essential that NASA researchers work closely with commercial developers and users, since the private sector understands the current market for technologies and can provide
guidance on applications that appear likely. Furthermore, NASA must seek the active involvement of the Federal Aviation Administration (FAA) and state and local agencies in the technology program. Their involvement is necessary in reaching an understanding of the constraints on technology deployment, such as environmental, safety, and public finance concerns.
To ensure the continuation of forward-looking aeronautics R&D, the committee urges NASA to join with other relevant government agencies, led by the Department of Transportation, in undertaking studies of future civil aviation needs and the opportunity for technology advancements to meet them and potentially stimulate new uses for civil aviation. Working with FAA, the National Transportation Safety Board, and other governmental agencies with operational and technological expertise should give NASA a better understanding of such needs and opportunities. The capabilities and technologies being developed under the SATS program may prove useful in ways that are not now apparent; for instance, they may benefit many different users by increasing the safety and utility of both general and commercial aviation. Indeed, many system and vehicle configurations that are not envisioned for the current SATS concept may prove useful. The committee urges NASA to keep such possibilities in mind.
The committee commends NASA for requesting and sponsoring this review, which offers the opportunity for the perspectives and advice of experts in transportation and other disciplines not involved in the conception of SATS to be brought to bear. Such external reviews are a valuable means of obtaining fresh perspectives on R&D program goals, plans, and accomplishments, and additional policy-level and technical reviews are desirable as the restructured program proceeds.