This document is intended to be a companion to previous books by the author: Partners in Freedom: Contributions of the Langley Research Center to U.S. Military Aircraft of the 1990's, and Concept to Reality: Contributions of the Langley Research Center to U.S. Civil Aircraft of the 1990's. Material included in the previous volumes provides informative and significant examples of the impact of applications of aeronautics research conducted by the NASA Langley Research Center on important U.S. civil and military aircraft of the 1990s. These contributions occurred because of the investment of the Nation in the innovation, expertise, and dedication of a staff of researchers and their unique facilities at Langley. Within that research environment, literally thousands of revolutionary concepts and advanced technologies for aeronautics have emerged, directed at challenges and barriers that impede the advancement of the state of the art in aircraft design and mission capabilities. Unfortunately, in the world of technology only a handful of advanced concepts are ever applied, due to a number of reasons. Factors that inhibit the application of advanced research technology are numerous and varied in nature, including cost, environmental impact, safety, complexity, reduced or inadequate funding and human resources, world events, perceived or actual risk, technical barriers, and others. The objective of this publication is to discuss the importance of innovation and the role of revolutionary advanced concepts within the aeronautics research community, and to provide information on typical advanced research projects conducted by Langley and its partners on topics that have not yet been applied by the military or civil aviation industry to production aircraft. Detailed information is first provided to describe each advanced concept, the projected benefits that could be provided if the technology is applied, and the challenges faced by the NASA research team to reduce the risk of application. Next, descriptions of specific research activities on the concepts identify the key projects, accomplishments, personnel, and facilities involved in the development of each concept. Finally, perspectives are provided on the current status of the subject concepts, including discussions of factors or future events that might intensify interest in their use for future applications. Many of the concepts described herein are subjects of ongoing NASA research thrusts, for which significant technical challenges are in the process of being addressed. Some of the research activities discussed were conducted and completed in past NASA projects; however, evolving requirements for military or civil aircraft systems demand a reexamination of the potential and current feasibility of the principles involved. This document is intended to serve several purposes. As a source of collated information on revolutionary concepts, it will serve as a key reference for readers wishing to grasp the underlying principles and challenges related to specific revolutionary concepts. Hopefully, such information will provide valuable background that can serve as starting knowledge bases for future research efforts and minimize the so-called "reinvention of the wheel" syndrome. The information identifies major obstacles to advanced aeronautics technology, thereby providing a sensitivity for multi-faceted research projects to ensure a higher likelihood of application. A definition of current barriers to application is extremely valuable for use in the future, when new breakthroughs in various technical disciplines may eliminate or minimize some of the critical barriers that have traditionally blocked the application of some of these specific revolutionary concepts. Finally, a review of the material will hopefully inspire the nontechnical (as well as technical) communities that aeronautics is not a "mature science" and that considerable opportunities exist to revolutionize the future.

For over 80 years, Langley Research Center has exemplified the cutting edge of world class aeronautics research for civil and military aircraft. Established in 1917 as the nation's first civil aeronautics research laboratory under the charter of the National Advisory Committee for Aeronautics (NACA), Langley initially existed as a small, highly productive laboratory with emphasis on solving the problems of flight for the military and the civil aviation industry. During World War II (WWII), the Langley Memorial Aeronautical Laboratory directed virtually all of its workforce and facilities to research for military aircraft. Following WWII, a more balanced program of military and civil projects was undertaken. The emergence of the Space Age and the incorporation of the NACA and Langley into the new National Aeronautics and Space Administration (NASA) led to a rapid growth of space related research and the cultural change of the old laboratory into a major research center. Today, Langley research efforts encompass critical areas of both aeronautics and space technology. Throughout its history, Langley has maintained a close working partnership with the Department of Defense, U.S. industry, universities, and other government agencies to support the defense of the nation with fundamental and applied research. Many of the legendary contributions of Langley to military aircraft technology have been discussed and documented by specialists, the media, and historians. Langley contributions to famous military projects such as the aircraft drag cleanup studies of WWII, the advent of supersonic flight and the X-1, the development and tests of the Century-series fighters, the X-15, and many, many others have been archived in detail. The objective of this particular undertaking is to document the contributions of Langley Research Center to specific military aircraft that were operational in the 1990's. Virtually all military aircraft that participated in Operation Desert Storm, Kosovo, and other peacekeeping missions of this era have Langley technical contributions to their design, development, and support. In some instances Langley research from one aircraft development program helped to solve a problem in another development program. At the conclusion of some development programs, Langley researchers obtained the research models to conduct additional tests to learn more about previously unknown phenomena. These data also proved useful in later developmental programs. Perhaps the most consistent element in all of the research programs is the length of time for the development and maturation of new research concepts before they are implemented in new aircraft. Many of the military aircraft in the U.S. inventory as of late 1999 were over 20 years old. Langley activities that contributed to the development of some of these aircraft began over 50 years prior. This publication documents the role-from early concept stages to problem solving for fleet aircraft-that Langley played in the military aircraft fleet of the United States for the 1990's. The declassification of documents and other material has provided an opportunity to record the contributions of Langley personnel and facilities and discuss the impact of these contributions on Department of Defense aircraft programs.

For over 80 years, Langley Research Center has exemplified the cutting edge of world class aeronautics research for civil and military aircraft. Established in 1917 as the nation's first civil aeronautics research laboratory under the charter of the National Advisory Committee for Aeronautics, Langley initially existed as a small, highly productive laboratory with emphasis on solving the problems of flight for the military and civil industry.

The state of the art in aeronautical engineering has been continually accelerated by the development of advanced analysis and design tools. Used in the early design stages for aircraft and spacecraft, these methods have provided a fundamental understanding of physical phenomena and enabled designers to predict and analyze critical characteristics of new vehicles, including the capability to control or modify unsatisfactory behavior. For example, the relatively recent emergence and routine use of extremely powerful digital computer hardware and software has had a major impact on design capabilities and procedures. Sophisticated new airflow measurement and visualization systems permit the analyst to conduct micro- and macro-studies of properties within flow fields on and off the surfaces of models in advanced wind tunnels. Trade studies of the most efficient geometrical shapes for aircraft can be conducted with blazing speed within a broad scope of integrated technical disciplines, and the use of sophisticated piloted simulators in the vehicle development process permits the most important segment of operations-the human pilot-to make early assessments of the acceptability of the vehicle for its intended mission. Knowledgeable applications of these tools of the trade dramatically reduce risk and redesign, and increase the marketability and safety of new aerospace vehicles.

The state of the art in aeronautical engineering has been continually accelerated by the development of advanced analysis and design tools. Used in the early design stages for aircraft and spacecraft, these methods have provided a fundamental understanding of physical phenomena and enabled designers to predict and analyze critical characteristics of new vehicles, including the capability to control or modify unsatisfactory behavior. For example, the relatively recent emergence and routine use of extremely powerful digital computer hardware and software has had a major impact on design capabilities and procedures. Sophisticated new airflow measurement and visualization systems permit the analyst to conduct micro- and macro-studies of properties within flow fields on and off the surfaces of models in advanced wind tunnels. Trade studies of the most efficient geometrical shapes for aircraft can be conducted with blazing speed within a broad scope of integrated technical disciplines, and the use of sophisticated piloted simulators in the vehicle development process permits the most important segment of operations-the human pilot-to make early assessments of the acceptability of the vehicle for its intended mission. Knowledgeable applications of these tools of the trade dramatically reduce risk and redesign, and increase the marketability and safety of new aerospace vehicles. Arguably, one of the more viable and valuable design tools since the advent of flight has been testing of subscale models. As used herein, the term "model" refers to a physical article used in experimental analyses of a larger full-scale vehicle. The reader is probably aware that many other forms of mathematical and computer-based models are also used in aerospace design; however, such topics are beyond the intended scope of this document. Model aircraft have always been a source of fascination, inspiration, and recreation for humans since the earliest days of flight. Within the scientific community, Leonardo da Vinci, George Cayley, and the Wright brothers are examples of early aviation pioneers who frequently used models during their scientific efforts to understand and develop flying machines. Progress in the technology associated with model testing in worldwide applications has firmly established model aircraft as a key element in new aerospace research and development programs. Models are now routinely used in many applications and roles, including aerodynamic data gathering in wind tunnel investigations for the analysis of full-scale aircraft designs, proof-of-concept demonstrators for radical aeronautical concepts, and problem-solving exercises for vehicles already in production. The most critical contributions of aerospace models are to provide confidence and risk reduction for new designs and to enhance the safety and efficiency of existing configurations. The objective of the material presented here is to provide the reader with an overview of some of the more interesting free-flight model testing techniques that have been developed and the role that the testing has played in fundamental and applied research, as well as in support of the development of some of the Nation's more important civil and military aerospace programs. The material also includes discussions of the development of the specialized facilities and equipment required for dynamic model tests.

The Langley Memorial Aeronautical Laboratory was established in 1917 as the Nation's first civil aeronautics research laboratory under the charter of the National Advisory Committee for Aeronautics (NACA). With a primary mission to identify and solve the problems of flight, the highly productive laboratory utilized an extensive array of wind tunnels, laboratory equipment, and flight research aircraft to conceive and mature new aeronautical concepts and provide databases and design methodology for critical technical disciplines in aircraft design. Prior to World War II (WWII), research at Langley on such diverse topics as airfoils, aircraft structures, engine cowlings and cooling, gust alleviation, and flying qualities was widely disseminated within the civil aviation community, and well-known applications of the technology to civil aircraft were commonplace. During WWII, however, the facilities and personnel of Langley were necessarily focused on support of the Nation's military efforts. Following WWII, aeronautical research at Langley was stimulated by the challenges of high speed flight and the associated problems that were exhibited by high-speed aircraft configurations operating at relatively low speeds, such as those used for takeoff and landing. Much of Langley's research during that time would ultimately be useful to both the civil and military aviation industries. With the emergence of the new National Aeronautics and Space Administration (NASA) in 1958, Langley retained its vital role in aeronautical research and assumed a leading position as NASA Langley Research Center, along with Ames Research Center, Lewis Research Center (now Glenn Research Center), and Dryden Flight Research Center. Langley's legacy of critical contributions to the civil aviation industry includes a wide variety of activities ranging from fundamental physics to applied engineering disciplines. Through the mechanisms of NASA technical reports, technical symposia, meetings with industry, and cooperative projects, the staff of Langley Research Center has maintained an awareness of the unique problems and challenges facing the U.S. civil aviation industry. With a sensitivity toward these unique requirements, Langley researchers have conceived and conducted extremely relevant research that has been applied directly to civil aircraft. These applications have resulted in increased mission performance, enhanced safety, and improved competitiveness. This document is intended to be a companion to NASA SP-2000-4519, "Partners in Freedom: Contributions of the Langley Research Center to U.S. Military Aircraft of the 1990s." Material included in the combined set of volumes provides informative and significant examples of the impact of Langley's research on U.S. civil and military aircraft of the 1990s. As worldwide advances in aeronautics and aviation continue at a breathtaking pace, documenting the significant activities, individuals, and events that have shaped the destinies of U.S. civil and military aviation has become increasingly important. In the research and development communities, many instances have occurred where fundamental, groundbreaking efforts have been forgotten or confused because of turnover of staffs, loss of technical records, and lack of documentation. This volume, "Concept to Reality: Contributions of the NASA Langley Research Center to U.S. Civil Aircraft of the 1990s," highlights significant Langley contributions to safety, cruise performance, takeoff and landing capabilities, structural integrity, crashworthiness, flight deck technologies, pilot-vehicle interfaces, flight characteristics, stall and spin behavior, computational design methods, and other challenging technical areas for civil aviation.

The goal of this publication is to provide an overview of the topic of revolutionary research in aeronautics at Langley, including many examples of research efforts that offer significant potential benefits, but have not yet been applied. The discussion also includes an overview of how innovation and creativity is stimulated within the Center, and a perspective on the future of innovation. The documentation of this topic, especially the scope and experiences of the example research activities covered, is intended to provide background information for future researchers.