INNOVATION IN FLIGHT: 

RESEARCH OF THE NASA LANGLEY RESEARCH CENTER 

ON REVOLUTIONARY ADVANCED CONCEPTS FOR AERONAUTICS 

By 

Joseph R. Chambers 

NASA SP-2005-4539 
 

Library of Congress Cataloging-in-Publication Data 

Chambers, Joseph R.

 Innovation in fight : research of the NASA Langley Research Center on 

revolutionary advanced concepts for aeronautics / by Joseph R. Chambers.

 p. cm.

 Includes bibliographical references and index.

 “NASA SP-2005-4539.”

 1. Aeronautics--Technical innovations--United States. 2. Research 

aircraft--United States. 3. Langley Research Center--Research. I. 

United States. National Aeronautics and Space Administration. History 

Ofce. II. Title. 

TL521.312.C44 2005

 629.130072’073--dc22

 2005026776 
ACKNOWLEDGMENTS 

I am sincerely indebted to the dozens of current and retired employees of NASA who consented 

to be interviewed and submitted their personal experiences, recollections, and fles from which 

this documentation of Langley contributions was drawn. Te following active and retired Langley 

personnel contributed vital information to this efort: 

Donald D. Baals Louis J. Glaab Vivek Mukhopadhyay 

Daniel G. Baize Sue B. Grafton Daniel G. Murri 

E. Ann Bare Edward A. Haering, Jr. (NASA Tomas A. Ozoroski 

J.F. Barthelemy Dryden) Arthur E. Phelps, III 

Dennis W. Bartlett Andrew S. Hahn Dhanvada M. Rao 

Steven X. S. Bauer Roy V. Harris Richard J. Re 

Bobby L. Berrier Jennifer Heeg Wilmer H. Reed, III 

Jay Brandon Jerry N. Hefner Rodney H. Ricketts 

Albert J. Braslow William P. Henderson A. Warner Robins 

Dennis M. Bushnell Paul M. Hergenrother Gautam H. Shah 

Richard L. Campbell Joseph L. Johnson, Jr. William J. Small 

Peter G. Coen Denise R. Jones Stephen C. Smith (NASA Ames) 

Fayette S. Collier Donald F. Keller M. Leroy Spearman 

Robert. V. Doggett, Jr. Lynda J. Kramer Eric C. Stewart 

Samuel M. Dollyhigh Steven E. Krist Dan D. Vicroy 

Cornelius Driver John E. Lamar Richard D. Wagner 

Clinton V. Eckstrom Robert E. McKinley Richard A. Wahls 

James R. Elliott Domenic J. Maglieri Richard M. Wood 

Michael C. Fischer Mark D. Moore Jefrey A. Yetter 

Charles M. Fremaux Robert W. Moses Long P. Yip 

Neal T. Frink Tomas M. Moul Steven D. Young 

I would like to express my special gratitude to Noel A. Talcott and Dr. Darrel R. Tenney, who 

provided the inspiration and mechanism to undertake this activity. 

Te eforts of the following active and retired industry members in reviewing the material 

signifcantly enhanced the accuracy and content of the fnal product: Te Boeing Company: 

A. L. “Del” Nagel, Rudy N. Yurkovich, Eric Y. Reichenbach, M. Emmett Omar, Michael J. Janisko, 

Robert A. Woodling, D. L. “Tony” Antani, Norbert F. Smith, Daniel Smith, Arthur G. Powell, 

Robert H. Liebeck, and William E. Vargo. Lockheed-Martin Corporation: Barry Creighton. 

Gulfstream Aerospace: Michael P. Mena. Northrop Grumman Corporation: Heinz A. Gerhardt, 

Dave H. Graham, Dale J. Lorincz and Vince Wisniewski. 

Tanks also to Percival J. Tesoro for the book design, Alicia V. Tarrant and Jefrey B. Caplan for 

outstanding assistance in photographic research in the Langley fles, Denise M. Stefula and Kay V. 

Forrest for editing, and Christine R. Williams for printing coordination. 

iii 
Special thanks and gratitude go to Dennis M. Bushnell, Senior Scientist of the NASA Langley 

Research Center, for his support and comments in the preparation of this document. His personal 

example and dedication to the pursuit of revolutionary technology have served as the stimulus 

and encouragement sought by thousands of his peers during his outstanding and remarkable 

NASA career. 

Joseph R. Chambers 

Yorktown, VA 

August 22, 2005 

iv 
 

 

 

 

 

 

 

CONTENTS 

Acknowledgments ..................................................................................................... iii 

Preface ......................................................................................................................vii 

Innovation: Te Seed Corn of Tomorrow ....................................................................1 

Selected Examples of Langley’s Research On Revolutionary Advanced Concepts 

Supersonic Civil Aircraft ......................................................................................7 

Te Blended Wing Body....................................................................................71 

Synthetic Vision ................................................................................................93 

Laminar-Flow Control.....................................................................................123 

Upper Surface Blowing ....................................................................................163 

Control of Aeroelastic Response ......................................................................191 

Te Joined Wing .............................................................................................227 

Te Vortex Flap................................................................................................247 

Innovative Control Efectors ...........................................................................269 

Personal Air Transportation Concepts .............................................................299 

Te Future of Innovation: Priming the Pump .........................................................319 

Bibliography ...........................................................................................................323 

Index ......................................................................................................................349 

NASA History Series ..............................................................................................371 

About the Author ...................................................................................................389 

v 

PREFACE 

Tis document is intended to be a companion to previous books by the author: NASA SP-2000-

4519, Partners in Freedom: Contributions of the Langley Research Center to U.S. Military Aircraft 

of the 1990’s, and NASA SP-2003-4529, 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 signifcant 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. Tese contributions occurred because of the investment of the Nation in the innovation, 

expertise, and dedication of a staf 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. 

Te 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 frst provided to describe each advanced concept, the projected 

benefts 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 specifc 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 signifcant 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. 

Tis 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 specifc revolutionary concepts. Hopefully, such information 

will provide valuable background that can serve as starting knowledge bases for future research 

vii 
eforts and minimize the so-called “reinvention of the wheel” syndrome. More importantly, the 

information identifes major obstacles to advanced aeronautics technology, thereby providing 

a sensitivity for multi-faceted research projects to ensure a higher likelihood of application. A 

defnition 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 specifc 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. 

Te written material has been prepared for a broad audience and does not presume any signifcant 

technical expertise. Hopefully, it will provide informative and interesting overviews for researchers 

engaged in aeronautics activities, internal NASA policy makers, national policy makers, NASA 

stakeholders, the media and the general public. A bibliography is provided for technical specialists 

and others who desire a more in-depth discussion of the concepts. 

viii 
INNOVATION IN FLIGHT: 

RESEARCH OF THE NASA LANGLEY RESEARCH CENTER 

ON REVOLUTIONARY ADVANCED CONCEPTS FOR AERONAUTICS 

By 

Joseph R. Chambers 

Innovation: The Seed Corn of Tomorrow 

“Te pointy end of NASA’s technological spear must stretch beyond “good work and evolutionary ideas” 

to revolutionary, high-payof concepts–with a sensitivity to the barriers that limit application.” 

Te foregoing statement by Dennis M. Bushnell, Senior Scientist of the NASA Langley Research 

Center, captures what many believe to be the critical strategy in maintaining a superior and vibrant 

aeronautical research capability for the United States. In his 42-year career at Langley, Bushnell 

has authored more than 240 technical papers on an impressive variety of technical subjects and 

presented over 260 invited lectures and seminars at numerous international meetings. Widely 

regarded as an international leader for his personal contributions to innovative research and his 

futuristic perspectives in science and technology, he is an outspoken advocate for creativity and the 

pursuit of “stretch goals” that challenge NASA’s aeronautics program. Bushnell’s perseverance and 

actions have nurtured one of NASA’s key missions in aeronautics–the conception and maturation 

of breakthrough, revolutionary technologies. By defnition, revolutionary technologies–such as the 

swept wing and jet propulsion–can radically change the very nature of aeronautical technology, 

resulting in unprecedented levels of capability, rather than incremental benefts. 

Dennis M. Bushnell, Senior Scientist of the 

NASA Langley Research Center. 

1 
In today’s world, where the public is generally unaware of NASA’s activities and contributions 

in aeronautics, the subject of innovative, revolutionary NASA research is even more unknown. 

Previous NASA publications, such as NASA SP-2000-4519, Partners in Freedom: Contributions 

of the Langley Research Center to U.S. Military Aircraft of the 1990’s, and NASA SP-2003-4529, 

Concept to Reality: Contributions of the Langley Research Center to U.S. Civil Aircraft of the 

1990’s, document some of the more important contributions of NASA that have been applied to 

modern military and civil aircraft. However, thousands of revolutionary, high-risk, high-payof 

research projects have not yet resulted in applications for various reasons, including technical risk, 

economics, and environmental impact. 

Te goal of this publication is to provide an overview of the topic of revolutionary research in 

aeronautics at Langley, including many examples of research eforts that ofer signifcant potential 

benefts, but have not yet been applied. Te discussion also includes an overview of how innovation 

and creativity is stimulated within the Center, and a perspective on the future of innovation. Te 

documentation of this topic, especially the scope and experiences of the example research activities 

covered, is intended to provide background information for future researchers. By nature, the 

technical interests of the aircraft industry—and by necessity those of NASA—are highly cyclical 

and often shaped by external factors. For instance, laminar fow control and powered lift tend 

to reemerge in priority every two decades or so. Being able to go back and review what has been 

done in the past is quite valuable. Hopefully, reviewing the extent of specifc past projects will 

identify appropriate points of departure to advance these concepts to future applications. With 

this background, repetitive or unproductive research options might be fltered at an early stage in 

order to avoid so-called “reinvention of the wheel”. In addition, discussions of specifc technical 

challenges that blocked the application of the example concepts will prove to be valuable in the 

future, if breakthroughs in enabling technologies result in removal of the past barriers. Examples 

of such occurrences include advances in composite fabrication technology permitting the 

previously unacceptable application of forward-swept wing confgurations, and the introduction of 

turbofan engines (with relatively cool exhaust fow) permitting the use of externally-blown faps 

for high-lift confgurations. 

Within an aeronautical “research and development” community, such as the Langley Research 

Center, the knowledgeable observer can distinguish two distinct thrusts of activity, both of which 

provide critical advances in the leadership of this Nation in aerospace technology and its end products. 

In a simplistic view, the “development” eforts tend to address evolutionary opportunities, with an 

emphasis on providing incremental improvements in capabilities, solving known or unexpected 

multidiscipline systems-level problems that arise, ensuring that the technology readiness level is 

sufciently high, and that risk has been lowered to an acceptable level for applications. At the 

2 
other end of the spectrum, “research” eforts address revolutionary, breakthrough concepts within 

disciplines or at the integrated confguration level. Tese activities are typically high risk, involve 

radical departures from conventional technology, and are capable of providing revolutionary benefts 

that can change the conventional paradigm. Such research is typically viewed with skepticism by 

many, and numerous challenges and barriers must be addressed before the development stage 

can be reached. What is appreciated, however, is that innovative research is the “seed corn” that 

provides tomorrow’s advances in aeronautics. 

NASA research centers are populated with inquisitive, highly capable research stafs that can, 

with appropriate resources, facilities and stimulation, lead the world in innovative research. 

Virtually every research professional enters his or her frst work duties at these locations with innate 

curiosity and interest in advancing technology in selected technical disciplines. Te attributes of an 

innovative person include not only the technical prowess and expertise to accomplish revolutionary 

breakthroughs, but also an appreciation of the current state of the art, past research eforts, and 

barriers to successful applications. 

Te environment available to the researcher within NASA has provided resource opportunities to 

fund the cost of conducting research studies, including the use of unique wind tunnels, laboratories, 

computational facilities, and fight testing. With the encouragement and approval of management 

Filters that limit the ultimate application of advanced technology. 

3 
and technical peers, a continuous stream of revolutionary concepts has come from the imaginative 

minds of Langley’s staf for potential transition to aeronautical applications. Unfortunately, the 

path from idea or concept to application is mined with severe challenges and barriers, and only a 

handful of thousands of advanced concepts survive to emerge as applications, as depicted in the 

accompanying sketch. 

Initially, the new idea must meet and satisfy technical requirements for its intended usage. To pass 

through this frst flter, the researcher is challenged to prove that the concept will work as envisioned, 

and that the technical beneft can be realized. Some research ideas at Langley have passed this level 

of maturity in relatively quick order, but others have required decades of frustrating attempts to 

reach technical closure, requiring extraordinary dedication and eforts by researchers. 

When the technical/scientifc flter has been successfully met by new technology, a second, even 

more daunting flter must be faced–a determination of the “real-world” feasibility of the concept. 

Embedded in the feasibility issue are assessments of the technical readiness level, cost/beneft trades, 

environmental impact, safety, market demand, risk, and numerous economic issues. Such issues 

typically pose a signifcant challenge to NASA researchers, who have limited experience in the 

proft-making stimuli of the business world, and the highly proprietary methods used by industry 

to evaluate and calibrate the worthiness of new technology. Nonetheless, appropriate systems-level 

studies or teaming arrangements with industry or others with sufcient qualifcations to predict 

these factors must be undertaken to determine the application value of the new concept. 

Bushnell refers to the challenges in this flter as the “ilities”, which for advanced aeronautical concepts 

(individual disciplinary concepts or unconventional airplane confgurations) can include: 

Engineering Economics Safety/Environmental 

Producability Afordability Environmental (icing, etc.) 

Maintainability Operational proft Noise 

Reliability Fuel usage Emissions 

Inspectability Product liability Robustness 

Capability (performance) Timeliness Failure modes 

Flexibility (growth capability) Exclusivity Flying qualities 

Repairability Regulatory issues Ride quality (turbulence) 

Operability Certifcation Contrails 

Durability Risk Sonic boom 

Compatibility (airport) Competitive status Structural integrity 

Resource availability Emergency egress 

4 
Obviously, the tasks facing the researcher and his/her team for applications of new concepts involve 

many, many potential “show stoppers” that demand attention and solution. Despite the scope 

of assessments required, NASA has successfully contributed critical technology to the Nation’s 

aircraft military and civil aircraft feets. 

Te remainder of this document is designed to provide an overview of some of the revolutionary 

technology concepts that have emerged from Langley studies, but have not yet been applied because 

of certain factors referred to in the previous discussion. Following these examples, a fnal section 

describes the eforts that have taken place at Langley to preserve and stimulate its reputation for 

the conception and development of innovative aeronautical technologies. 

5 
6
Supersonic Civil Aircraft: The Need for Speed 

Concept and Benefts 

Since the frst days of commercial airliners, passengers have always placed high priorities on speed, 

cost, safety, reliability, and comfort in air transportation. Travel speed, and its benefcial impact 

on personal mobility and business interactions, has been one of the more dominant factors for the 

traveler. In the late 1950s, as faster swept-wing jet transports replaced their propeller-driven ancestors 

for public transportation, and the military began to pursue large supersonic bomber designs such 

as the XB-70, the aviation industry and the government began serious eforts to develop the next 

logical progression in the quest for speed: a supersonic commercial transport. If an economically 

feasible, environmentally friendly supersonic transport (SST) could be introduced into the air 

transportation system, the benefts of signifcantly increased cruise speed would attract a large 

segment of the passenger market (especially in the business sector), possibly driving conventional 

subsonic transports from a large portion of the international air transport marketplace. 

Te subsequent international rush to SST applications resulted in abortive programs. An illfated national efort within the United States for a U.S. SST was terminated in 1971 without 

a viable aircraft, a brief and unsuccessful introduction of the Russian Tu-144 SST occurred, 

and the commercial introduction of the French/British Concorde proved to be an impressive 

technical success but a hopeless economic failure. Nonetheless, the quest for supersonic civil 

Supersonic transports ofer revolutionary benefts in travel time and personal productivity. 

7 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Comparison of international travel times for a conventional subsonic transport and an 

advanced Mach 2.4 high-speed civil transport. 

aircraft has sporadically persisted. In the 1990s, visions of second-generation supersonic transports 

that could fy 300 passengers at more than 1,600 mph (Mach 2.4) were the focus of extensive 

research eforts involving U.S. industry and government, as well as Europe and Japan. Such an 

airplane could speed across the Pacifc from Los Angeles to Tokyo in a mere 4.5 hours, 

revolutionizing air travel and, perhaps, conventional business paradigms. Unfortunately, a multitude 

of technical and nontechnical obstacles has prevented supersonic air travel and its 

potential benefts. 

Challenges and Barriers 

Obstacles to the introduction of supersonic commercial transports are arguably the most demanding 

of any aircraft type. In addition to a formidable array of technical challenges within virtually all 

critical aircraft engineering disciplines, a multitude of issues involving environmental protection 

and international politics must be addressed and resolved. Although research agencies such as NASA 

are uniquely qualifed to help provide the technology necessary to meet mission requirements for 

SST operations, the resolution of many barriers to implementation, such as political and emotional 

issues, are far beyond the capabilities of researchers. Te enormous difculty in introducing viable 

supersonic civil aircraft into the commercial feet is highlighted by the fact that, although the 

world has seen almost continuous, yearly introduction of new subsonic jet transport aircraft into 

service over the last 45 years, no new supersonic civil aircraft have entered operations in the last 

30 years. 

Te following discussion of technical, environmental, economic, and political issues provides a 

background of some of the more critical factors preventing operational application of supersonic 

8 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

civil aircraft. Many of these issues have been identifed and resolved by NASA and its partners, but 

many important issues continue to remain unresolved, preventing the deployment of a U.S. SST. 

Technical Issues 

Te most fundamental technical challenges to an SST confguration involve the ability to meet 

the mission requirements in an efcient, economically viable, environmentally acceptable fashion. 

At the forefront of these requirements is the need for efcient aerodynamic performance at 

supersonic speeds. Geometrical shaping of the airframe, efcient performance of the propulsion 

system at subsonic, transonic, and supersonic speeds, and airframe/propulsion integration must 

be accomplished in a manner to provide sufcient lift/drag (L/D) ratio for efcient supersonic 

and subsonic cruise, as well as during takeof and landing. At supersonic speeds, the dominant 

aerodynamic challenge is drag reduction. Whereas current subsonic jet transports can exhibit L/D 

ratios approaching 19 at cruise conditions, the most efcient supersonic transport designs today 

exhibit L/D ratios of less than 10, indicative of the tremendous drag increase associated with 

additional wave drag created in supersonic fight. With relatively low L/D values, the supersonic 

transport will require signifcantly more fuel per minute at cruise conditions. Obviously, supersonic 

aerodynamic design methodology is a mandatory part of the designer’s tool kit for this class 

of aircraft. 

Stability and control requirements for supersonic transports employing highly swept wings can 

result in confguration compromises and trade-ofs that markedly decrease supersonic aerodynamic 

performance. For example, the low-speed longitudinal stability and control characteristics 

of supersonically efcient, highly swept arrow wings are usually unacceptable. In particular, 

aerodynamic fow phenomena over such wings at low-speed conditions result in fow separation on 

the outer wing at moderate angles of attack. Tis separation leads to the intolerable longitudinal 

instability known as “pitch up” and also to marginal ability to control lateral motions, particularly 

in sideslip conditions during approach to landing. As a result, the nearly optimum arrow-wing 

planform may have to be modifed to a less efcient supersonic shape (approaching a delta wing) 

to ensure satisfactory fying characteristics at low speeds. 

Te aerodynamic performance of an SST confguration at of-design conditions, such as subsonic 

cruise or during extended air trafc landing delays or diversions to other airports, is a key factor 

in the fuel and weight required for mission capability. Because highly swept confgurations exhibit 

aerodynamic and propulsive efciencies that are much less than conventional transport designs 

at subsonic speeds, a large fuel reserve requirement must be met for contingencies during normal 

operations. In fact, for typical supersonic transport confgurations the weight of fuel reserves can 

Innovation in Flight 9 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

be equal to or greater than the useful payload. As an example of the signifcance of this issue, 

the Concorde exhibited an L/D ratio of only about 4 at subsonic loiter and approach conditions, 

resulting in heavy fuel usage, poor engine efciency, and high noise levels. On fights from Europe, 

the airplane arrived at New York with 15 tons of spare fuel (1.5 times the payload), and an additional 

30 tons of mission fuel was needed to carry the 15 tons of spare fuel. 

Integrating airframe and propulsion components into the SST confguration is especially 

challenging. In addition to maximizing aerodynamic and propulsive performance, the designer 

must also minimize weight to achieve adequate payload capability. Representative supersonic 

transports designed for Mach 2.0 carry a payload of only about 6 percent of takeof gross weight 

compared with subsonic transports that typically accommodate about a 25-percent payload 

fraction. Tus, aircraft empty weight (and weight-saving concepts) becomes especially critical for 

supersonic vehicles. 

In the area of aircraft materials, the supersonic transport may have to incorporate exotic and 

expensive fabrication techniques and materials. In this regard, selection of design cruise Mach 

number may dictate a departure from conventional structures. Conventional aluminum materials 

are not able to withstand the withering temperatures at cruise speeds much above Mach 2.5, 

requiring the use of stainless steel or titanium for the airframe. Resulting cost associated with these 

advanced materials has been a major factor in limiting design cruise speeds, even though some 

supersonic airplane productivity studies show maximum benefts near Mach 3.0. 

Along with strenuous aerodynamic and structural design challenges, the supersonic transport 

must meet demanding propulsion requirements. Efcient engine operations over the subsonic 

and supersonic fight envelopes must be attained, engine inlet and nozzle confgurations must be 

efcient and robust, and engine components and subsystems must be capable of extended hightemperature operations with minimal maintenance and maximum reliability. Efcient engine cycles 

for supersonic cruise typically lead to low bypass ratio engine confgurations in contrast to the high 

bypass ratio designs used by subsonic transports. Te low bypass ratio engine produces a high 

velocity jet efux that creates extremely high noise levels if not attenuated by noise suppressors. 

Operational feld length requirements impose severe constraints on engine sizing and attendant 

issues, such as takeof noise, for supersonic cruise vehicles. Te inherent low-lift, high-drag 

characteristics of highly swept supersonic wings may result in long takeof runs, driving designers 

to higher thrust engines that are mismatched for optimum cruise applications. In addition, higher 

engine settings may exacerbate takeof noise levels and afect the ability to comply with noise 

regulations. Extremely large, heavy engine noise suppressors may be required, further aggravating 

10 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

the inherent weight issues previously noted. Takeof and airport community noise is one of the 

most difcult barriers to implementation of future supersonic civil transports, especially with 

advanced subsonic transport aircraft having successfully met dramatic reductions in noise levels 

required by new regulations. 

An aircraft traveling through the atmosphere at supersonic speeds (above about 660 mph) 

continuously produces air-pressure waves similar to waves created by a ship’s bow. When supersonic 

fight became a reality around 1950, the impact of these waves and the accompanying sonic boom 

was unexpected. Aerodynamicists were aware of the shock waves associated with supersonic 

motion, but they did not expect these shock waves to reach the ground for high fying aircraft. 

However, when supersonic fghters were introduced in the 1950s, people were startled by the booms 

and some buildings and structures were damaged by low-fying supersonic aircraft. As military 

aircraft increased their supersonic missions over populated areas, complaint and damage claim 

numbers grew. 

Pressure felds created by supersonic shock waves result in sonic booms. 

Innovation in Flight 11 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

A typical airplane generates two main shock waves, one at the nose (bow shock) and one of the 

tail (tail shock). Local shock waves coming of the canopy, wing leading edges, and engine nacelles 

tend to merge with the main shocks at some distance from the airplane. Te resulting pressure 

pulse is a characteristic “N” shape. To an observer on the ground, this N pulse is felt as an abrupt 

compression above atmospheric pressure, followed by a rapid decompression below atmospheric 

pressure and a fnal recompression to atmospheric pressure. Te total change takes place in less 

than half of a second (about 0.23 seconds for Concorde) and is felt and heard as a double jolt 

or boom. Te relative strength of the boom overpressure is dependent on several factors, 

including the altitude, speed, length, shape, and weight of the generating aircraft as well as 

atmospheric conditions. 

Te strongest sonic boom is usually felt directly beneath the airplane and decreases on either side 

of the fight path. A turning, or accelerating, supersonic airplane may concentrate the set of shock 

waves locally where they intersect the ground and produce a focused “super boom.” For example, 

the SR-71 airplane, maneuvering at Mach 3.0 and an altitude of 80,000 ft, creates window-rattling, 

double-crack sonic boom signatures on the ground. Human subjects have strongly opposed 

unexpected encounters with sonic booms. Te highly undesirable efects run from structural 

damage (cracked building plaster and broken windows) to heightened tensions and annoyance 

of the citizenry because of the startle factor. Ground-based research and subjective evaluations 

during actual aircraft fybys have produced extensive sets of data that have calibrated sonic boom 

signatures and human responses for specifc aircraft and operating conditions. Currently, civil 

supersonic fight over land is prohibited by law in the United States and most other nations due to 

the disruption and annoyance caused by sonic booms. Tis restriction in fight path options has 

had a deep, negative impact on the economic feasibility and operational fexibility of supersonic 

transports, and solving the sonic boom issue remains one of the most vexing technical challenges 

facing the designer. 

Supersonic transports may require special crew-station design features to meet the demands of 

operations in the air trafc system, especially during takeof and landing. For example, visibility 

from the pilot’s location may be unacceptable during the landing approach for streamlined, highly 

swept wing designs that must operate at relatively nose-high attitudes to generate the lift required 

for low-speed operations. Te frst generation of supersonic transports resolved this problem with 

variable-geometry “drooped-nose” confgurations that were capable of being streamlined for 

cruise fight and reconfgured for good visibility during landing. Unfortunately, weight penalties 

associated with this approach are large and more innovative concepts, such as synthetic vision 

(discussed in a separate section of this document), have been explored to minimize this penalty. 

12 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Te Tu-144 supersonic transport used a variable-geometry drooped nose for improved visibility 

during low-speed operations. 

Te unique, slender shaping of the supersonic transport creates fying quality issues and control 

system considerations radically diferent from conventional subsonic transports. For example, the 

slender shape of such airplanes may result in roll response and lateral-directional handling qualities 

that difer substantially from those of conventional subsonic transports. Slender aircraft also require 

certain unconventional augmentation systems in the control system design. Pilot cockpit displays 

may require additional information beyond that used for subsonic fight, especially for the sensitive 

cruise fight conditions. In addition, the efcient and safe integration of SST aircraft in the airport 

terminal area requires analysis of the impact of the speed diferential between supersonic and 

subsonic confgurations during loiter, approach, and landing. 

Other technical issues posing special challenges for supersonic commercial aircraft are concerns 

over potential hazardous efects on aircrew and passengers due to radiation exposure at the high 

altitudes (over 55,000 ft) appropriate for supersonic cruise and the potential harmful impacts of 

supersonic transport feet emissions on the Earth’s ozone layers. Depletion of signifcant amounts 

of upper atmosphere ozone could result in an increase in skin cancer incidences on Earth. Tese 

environmental challenges have been prominent research topics in all supersonic transport studies. 

Nontechnical Issues 

In addition to the foregoing technical challenges, commercial introduction of supersonic transport 

confgurations must address and resolve certain nontechnical hurdles involving economics, industry 

Innovation in Flight 13 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

market projections and investment strategies, and actual or perceived risk. Foremost among these 

concerns is the level of surcharge for passengers, which is above that associated with typical subsonic 

jet travel. Te fact that supersonic air travel will cost the passenger more than comparable subsonic 

fares is accepted as a primary characteristic of this air transportation mode. For example, the cost 

to fy as a passenger on the Concorde on a typical transatlantic trip was 10 times (1,000 percent) 

more than fares available on some subsonic transports. However, the passenger base upon which 

revenues will depend for this mode of travel will probably consist of business people in need of 

rapid business interactions, or the wealthy in need of exclusive and unique travel experiences. Te 

operational experiences with the Concorde feet revealed that 80 percent of its passengers were 

business travelers and close to 80 percent were repeat travelers. In contrast to the business traveler, 

however, the general public regards air travel as a commodity, readily willing to sacrifce in-fight 

cruise speed (with surcharges) for lower ticket prices ofered by airlines fying large wide-bodied 

subsonic transports. Te level of surcharge and the public’s willingness to accept it are, therefore, 

key factors determining the ultimate economic feasibility of supersonic transportation. 

Business strategies and industry market projections play an important role in the potential insertion 

of supersonic transports in the international air transportation system. Competing sectors of the 

market, such as extremely large subsonic transports (over 500 passengers), very efcient long-range 

subsonic transports, and other travel options play key roles in the willingness of industry to invest 

in supersonic technology. Evolving technologies in other felds, such as telecommunications and 

virtual, computer-based meetings, also have large impacts on the demand for business travel, the 

prime market for supersonic transports. 

Arguably, one of the most powerful negative infuences afecting supersonic transports is the 

continuing worldwide rise in aviation fuel prices. Airline concerns over fuel costs have consistently 

resulted in abrupt rejection of near-transonic or supersonic cruise capability in new transport 

aircraft. Instead, in times of fuel crises airlines seek fuel-efcient aircraft and a willingness to reject 

high cruise speeds if necessary in order to remain economically viable. 

Finally, the unprecedented costs and risks associated with developing and certifying a revolutionary 

new product line like a supersonic transport could easily result in catastrophic consequences for 

the aviation industry and business investors. Tis factor—combined with the disappointing 

experiences with Concorde and the Tu-144, and an appreciation of the high technical and political 

risks associated with developing a supersonic transport—has resulted in a pessimistic, disinterested 

atmosphere within the aviation community except for the business jet sector. 

14 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Langley Activities 

Background 

No other undertaking in the aeronautics research activities of the National Aeronautics and Space 

Administration (NASA), or its predecessor, the National Advisory Committee for Aeronautics 

(NACA), approaches the magnitude of human and monetary resources expended on the 

conception, development, and assessment of supersonic civil airplane confgurations. Tousands 

of researchers—contributing expertise from a wide variety of technical disciplines and representing 

all NASA (and NACA) research centers, NASA Headquarters, and NASA’s industry, military, 

and university partners—have participated for over 40 years in the quest for economically and 

environmentally feasible supersonic airplanes. Te scope and details of this huge research efort 

are far beyond the intent of this book. Even a constrained attempt to identify key individuals 

and events within Langley will undoubtedly result in unintentional omissions of central fgures 

and events. Te following discussion is an attempt to collate and provide a high-level summary 

highlighting some Langley roles in this monumental endeavor. Hopefully, the casual reader will 

understand and appreciate the challenges and barriers unique to applying the technology and the 

role that Langley has played in attempting to resolve these issues. 

Excellent additional sources suitable for the technical specialist and others interested in the details 

of domestic and international activities in this area are readily available in the literature. Much 

of the NASA formal document base has now been declassifed, but the results of some programs 

are not in the open literature at this time. In addition to the extensive technical papers and 

reports of NASA and its contractors, excellent overviews of the international supersonic transport 

experiences are available. Two publications are particularly recommended for further information 

and perspectives. Te technical summary Supersonic Cruise Technology (NASA SP-472) by F. 

Edward McLean provides an in-depth review of the advancement in technology and NASA’s 

role in supersonic transport technology through the early 1980s. In High Speed Dreams, Erik M. 

Conway constructs an insightful history that focuses primarily on political and commercial factors 

responsible for the rise and fall of American supersonic transport research programs. Material from 

both publications has been liberally used in this document. 

Chronology of Langley Involvement 

Te research eforts of Langley Research Center in supersonic technology involve fve distinct 

phases. Te frst phase of research, during the NACA era, began in the mid-1930s and lasted until 

the NACA was absorbed by NASA in 1958. During those years, the fundamental understanding 

Innovation in Flight 15 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

of supersonic fight was developed and refned, the aerodynamics of basic shapes and aircraft 

confgurations were explored, experimental methods and facilities were developed, and manned 

supersonic fight was demonstrated with several NACA and military research aircraft. Results of 

this pioneering NACA research from Langley on supersonic technology and design methodology 

were subsequently used by the U.S. industry and the Department of Defense (DoD) in designing 

the famous military “Century-Series” fghters and other high-speed vehicles of the 1950s. 

Chronology of supersonic research at NASA Langley Research Center. 

In the next phase of U.S. supersonic research, from 1958 to 1971, Langley became a major participant 

in support of the development of two high-priority national projects: the supersonic cruise XB70 bomber and the SST. In those years, supersonic aerodynamic design methods were refned, 

critical phenomena such as the sonic boom became research topics, and efcient supersonic-cruise 

confgurations emerged. 

When the SST Program was terminated by Congress in 1971, NASA continued to seek out solutions 

to the technical issues of supersonic fight in a third phase of supersonic research, known as the 

NASA Supersonic Cruise Research (SCR) Program, which was led by Langley and conducted 

between 1971 and 1981. In the SCR Program, aggressive technical advances were made in the 

areas of propulsion, noise, and takeof and landing performance. Unprecedented accomplishments 

in the development of unique materials and fabrication processes for supersonic-cruise applications 

16 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

were also contributed. Following the SCR Program’s termination in 1982, NASA’s supersonic 

research eforts declined signifcantly. 

During the Reagan administration of the late 1980s, growing domestic and international 

enthusiasm over the potential benefts of hypersonic fight and the X-30 (National Aerospace Plane) 

Program spun of a renewed interest in high-speed fight. Tis interest resulted in a fourth major 

phase of NASA’s focused supersonic research, known as the NASA High-Speed Research (HSR) 

Program, which was managed by Langley for the Agency. Extensive NASA/industry research and 

development activities in the HSR Program began in 1989 and ended in 1999. 

Te ffth (current) phase of NASA’s supersonic research and development program began 

following the termination of the HSR Program in 1999. After the program’s cancellation, interest 

in and funding for commercial supersonic transports plummeted. However, sporadic interest in 

economically feasible supersonic business jets began to surface within industry, and collaborative 

eforts involving systems-level analysis and a few key technical disciplines (such as noise and 

sonic boom) were established within NASA. Several of these activities continue within NASA’s 

aeronautics program today. 

Early NACA and NASA Supersonic Confguration Research 

Fundamental research related to fight at supersonic speeds had occurred within the NACA and 

NASA for at least three decades before the emergence of any serious consideration of supersonic 

civil aircraft. Early activities included rapid advances in areas such as analysis of compressible 

fows, development of unique testing techniques and facilities for transonic and supersonic studies, 

development and validation of analytical and computational methods for aerodynamic analyses, 

and extensive experimental investigations in wind tunnels and fight. An expansive discussion of 

Langley’s early contributions to high-speed fight and the key staf members involved is given in 

James R. Hansen’s book, Engineer in Charge (NASA SP-4305). 

Pioneering eforts in compressible aerodynamics and high-speed fight by such Langley legends 

as Eastman Jacobs and John P. Stack provided the technical and managerial leadership to keep 

Langley in the forefront of supersonic activities on an international scale. Stack’s hard driving, 

personal interest in advanced high-speed aircraft and his aggressive tactics in international research 

activities and committees played a key role in the advancement of research maturity and relevance 

of the contributions from Langley’s staf. His dedication and advocacy for a transonic research 

airplane helped spark the national interest that resulted in the remarkable accomplishments of the 

X-1 project, the conquest of the sound barrier, and the race for supersonic capability. 

Innovation in Flight 17 
 

 

 

 

SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

John P. Stack, leader of Langley eforts in high-speed fight. 

Langley staf members responded to Stack’s leadership and challenges with unprecedented 

research accomplishments that led to international recognition for leadership in the feld. Langley’s 

contributions were remarkable: 

• Leadership and participation in the X-1 and subsequent high-speed X-series aircraft 

programs that demonstrated the feasibility of supersonic and hypersonic fight 

• Robert T. Jones’ sweepback theories, which led the way toward future high-speed 

wing confgurations 

• Richard T. Whitcomb’s development of the area rule, which unlocked the puzzle of efcient 

transonic and supersonic fight 

• Conceptual development and implementation of slotted walls for transonic wind 

tunnels, which permitted valid ground testing at transonic speeds 

• Acquisition of extensive and valuable design data on the efects of confguration variables, 

such as wing sweep, on high-speed characteristics 

18 Innovation in Flight 
 

 

SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

• Development of a series of unique wind tunnels that became national treasures, including 

the 4- by 4-Foot Supersonic Pressure Tunnel and the Unitary Plan Wind Tunnel 

• Establishment and stafng of a new high-speed fight center that would become known as 

the Dryden Flight Research Center 

• Initiation of pioneering research of operating problems associated with 

high-speed fight 

• Leadership in the assault on hypersonics that led to the X-15 program’s 

historical accomplishments 

• Pioneering research by Harvey H. Hubbard, Domenic J. Maglieri, and Harry W. Carlson 

on the sonic boom phenomenon, which would become the ultimate barrier to civil 

supersonic overland fight 

One notable contribution made by Langley’s staf during the NACA years was development of 

airplane confgurations for efcient fight at supersonic and hypersonic speeds. Tis pioneering 

research resulted in concepts and design methodology still in use today. Much of this research 

resulted in innovative “arrow wing” designs with highly swept leading and trailing edges. Such 

confgurations became the cornerstone of Langley’s high-speed research activities. 

Highly swept arrow wings are nearly optimum shapes for supersonic fight. 

Innovation in Flight 19 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Te supersonic arrow wing designed by Langley’s Clinton E. Brown and F. Edward McLean 

appears in the NASA insignia. 

One particular arrow wing design has endured throughout NASA’s history. In the late 1950s, 

Clinton E. Brown and F. Edward McLean developed an arrow wing for supersonic applications 

based on analytical studies and subsequent wind-tunnel tests that verifed the confguration’s high 

aerodynamic efciency at high speeds. Following the test program, the wind-tunnel model was 

put on display and observed by James J. Modarelli, a visitor from the NACA Lewis Laboratory. 

Modarelli headed the Lewis Research Reports Division when NACA Executive Secretary John 

Victory requested suggestions for an appropriate seal for the new NASA organization. Impressed 

by the sleek, futuristic aspects of the Langley model, Modarelli and his graphic artists included an 

interpretation of it in a seal design that was subsequently adopted and later modifed to an insignia 

that became unofcially known as the NASA “meatball.” In the logo, the sphere represents a planet, 

the stars represent space, the red chevron is the rendering of the Brown/McLean wing representing 

aeronautics, and an orbiting spacecraft going around the wing represents the space program Tis 

insignia was ofcially used from 1958 to 1975, when it was replaced by a stylized NASA “worm,” 

and was then returned to NASA usage as directed by Administrator Daniel S. Goldin in 1992. 

Brown and McLean later advanced during their careers to become historic NASA managers in 

high-speed research. 

Perhaps the most descriptive characterization of Langley throughout its history in aeronautical 

research has been its capability as a “one-stop shopping center” of technology in most of the 

critical disciplines required for aircraft applications. Certainly this personality emerged in the area 

of supersonic aircraft design, with world-class staf and facilities associated with aerodynamics, 

20 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Te XB-70 bomber, designed for supersonic cruise at Mach 3.0. 

structuresandmaterials,fightdynamics and control,noise and other environmentalissues,advanced 

instrumentation, and computational methods. Coupled with a high demand for consultation by 

industry peers and active participation in aircraft development programs (especially leading-edge 

military activities), Langley’s staf of experts was poised and ready when the Nation’s interest 

turned to supersonic cruise vehicles. 

Te Military Incubator 

Langley’s intimate partnership with the military community resulted in extensive use of Langley’s 

vast collection of aerodynamic design data, wind-tunnel facilities, and expertise in military 

supersonic programs during the 1950s, such as the famous Century Series fghters (F-102, F-105, 

etc.), the B-58 bomber (capable of short supersonic “dash” mission segments), and planning for 

advanced supersonic vehicles within the Air Force. In the late 1950s, a single Air Force program— 

the XB-70 bomber—was to stimulate NASA’s involvement in what would ultimately become the 

basis for a civil supersonic transport program. 

With projected entry into service for the 1965 to 1975 time period, the XB-70 (known initially 

as the highly secret WS-110A project) was initiated as a result of Air Force interest in a supersonic 

strategic bomber replacement for the B-47. North American Aviation was awarded the XB-70 

contract in December 1957, but the excitement of potential production was quickly chilled 2 

years later when the Eisenhower administration decided that the intercontinental ballistic missile 

Innovation in Flight 21 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Delwin R. Croom (left) led tests of an early XB-70 design in the Langley High Speed 7- by 10-

Foot Tunnel in 1957. 

Free-fight model testing of the early XB-70 design was conducted in the 30- by 60-Foot Tunnel 

in 1957. 

22 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Te XB-70 was used in NASA research on supersonic drag and sonic booms. 

(ICBM) had replaced the manned bomber as primary deterrent for potential enemies of the United 

States. Tis directive was eventually amended, then reimposed by Defense Secretary Robert S. 

McNamara of the Kennedy administration. In 1964, the program was reduced to construction 

of two XB-70 aircraft for research fights. In addition to the ICBM issue, one factor possibly 

leading to the cancellation of XB-70 production was that another supersonic cruise aircraft—to 

be developed as the SR-71—was already underway and had, in fact, been fying as the Lockheed 

A-12 for 2 years before the XB-70 was rolled out. Te decision to eliminate production of the 

XB-70 signaled the end of acknowledged interest within the Air Force for a long-range supersonic 

cruise bomber. 

Te frst XB-70 research aircraft few in September 1964 and attained its design cruise speed of 

Mach 3.0 (2,000 mph) on October 14, 1965. Tis remarkable airplane was engineered before 

high-speed computers or automated procedures would be incorporated into the design process. 

Te XB-70 had two windshields. A moveable outer windshield was raised for high-speed fight to 

reduce drag and lowered for greater visibility during takeof and landing. Te forward fuselage was 

constructed of riveted titanium frames and skin. Te remainder of the airplane was constructed 

almost entirely of stainless steel. Te skin was a brazed stainless steel honeycomb material. Six 

General Electric turbojet engines, each in the 30,000-lb-thrust class, powered the XB-70. Flight 

testing of the two research aircraft provided unprecedented data on aerodynamics, structures and 

materials, fying qualities, and sonic boom phenomena. 

Innovation in Flight 23 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Small wind-tunnel models used in the Langley 4- by 4-Foot Supersonic Tunnel to study pressure felds associated 

with sonic booms. 

Because of its relative size and speed capability, the XB-70 became the technological focal point 

of an embryonic industrial and governmental interest in supersonic civil transports. Langley had 

conducted developmental wind-tunnel testing of the airplane confguration in some of its tunnels, 

and staf members, such as Cornelius (Neil) Driver, had responded to requests from the Air Force 

for independent assessments of the XB-70 design’s supersonic efciency. NASA began formulating 

a supersonic transport technology research program around the XB-70 in 1962. In early 1966, 

NASA allocated funding for elaborate instrumentation for the second XB-70 airplane with plans 

to collect extensive data for supersonic design purposes. Unfortunately, this particular airplane was 

destroyed in a crash following a midair collision during a military photographic session at Edwards 

Air Force Base on June 8, 1966. Following an instrumentation retroft of the frst XB-70 by the Air 

Force and NASA, initial fights were begun to measure sonic boom characteristics and exploration 

of SST fight envelopes. Te Air Force subsequently withdrew from the program and NASA took 

over as the sole XB-70 sponsor in March 1967. 

During its research missions, the XB-70 was used by NASA for sonic boom characterization and 

supersonic drag correlations between fight and wind-tunnel predictions. Both areas involved 

participation of Langley’s staf, including Domenic Maglieri and John P. (Jack) Peterson. Boom 

study results produced unprecedented details on the physical characteristics of boom propagation 

and coverage from various altitudes and speeds. Te drag correlations showed that several 

24 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

improvements in the extrapolation of wind-tunnel data to fight conditions were required. Te 

fnal fight of the XB-70 was on February 4, 1969, when it was delivered by NASA to the Air Force 

Museum at Wright-Patterson Air Force Base, Ohio, where it is on display today. 

The U.S. National Supersonic Transport Program 

Te XB-70’s demise as a potential production aircraft for the U.S. Air Force in the early 1960s was 

regarded as a major blow by those interested in seeing the normal extension of military technology to 

commercial use. Te loss of a potential proving ground for supersonic cruise technologies impacted 

the entire industry outlook for supersonic civil transports. In addition, opposition to supersonic 

fight had already risen from environmentalists concerned over noise, pollution, radiation, safety, 

and sonic booms associated with a feet of such aircraft. 

NASA, however, had continued to produce an extensive background of supersonic technology that 

was rapidly maturing for applications to supersonic cruise fight. Within its research mission, the 

Agency could logically focus some of its talents toward the potential benefts of this vehicle class. 

Langley’s John P. Stack exerted his powerful leadership in many venues. After Federal Aviation 

Administration (FAA) representatives visited Langley in November 1959 to review prospects for 

a U.S. SST, Stack orchestrated a pivotal briefng by Langley staf members to top FAA ofcials 

the following month on the status and outlook of supersonic transports. Tis meeting and Stack’s 

enthusiasm helped begin the advocacy for an SST Program within the FAA. Contributors included: 

John Stack and Mark R. Nichols—state of the art and performance; Harvey H. Hubbard and 

Domenic Maglieri—noise and sonic boom; Eldon Mathouser—structures and materials; Tomas 

L. Coleman—loads; Ralph W. Stone—fying qualities; Joseph W. Wetmore—runway/braking 

requirements; James B. Whitten—operations; John M. Swihart and Willard E. Foss—propulsion; 

and Tomas A. Toll—variable geometry. 

Stack represented NASA in 1961 during discussions with the FAA and the DoD to formulate a 

cooperative U.S. SST Program and to defne agency responsibilities. President John F. Kennedy 

charged the FAA with responsibility to provide leadership and fscal support to the program, 

with NASA providing basic research and technical support. Te FAA published a Commercial 

Supersonic Transport Report in June 1961 stating that the DoD, NASA, and the FAA were the 

appropriate government agencies to defne the program. Stack had formed an in-house Supersonic 

Transport Research Committee in June 1961 to coordinate and guide Langley’s supersonic research. 

While the FAA sought and obtained funding from Congress in 1962 for the proposed program, 

NASA researchers at Langley, Ames, Lewis, and Dryden explored confguration concepts and 

technologies that might meet the requirements of a commercial SST. 

Innovation in Flight 25 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Stack left NASA in 1962, and Chief of the Full-Scale Research Division, Mark R. Nichols and his 

assistant, Donald D. Baals, became Langley leaders in the formulation of SST research. Nichols 

and Baals were central fgures for NASA SST eforts, and their personal leadership led to the success 

of NASA’s supersonic cruise eforts at that time. More importantly, they set into motion research 

programs producing results that have endured to the present day in terms of design methodology 

and technology for future supersonic vehicles. Te research team that Nichols and Baals led during 

the U.S. SST Program consisted of some of the most outstanding high-speed aerodynamic experts 

in the history of Langley. Aerodynamic theory and performance optimization were contributed by 

Harry W. Carlson, Roy V. Harris, F. Edward McLean, and Richard T. Whitcomb; and supersonic 

transport conceptual designs were conceived by A. Warner Robins. M. Leroy Spearman, another 

key researcher, was head of Langley’s supersonic wind tunnels. (Spearman retired from Langley in 

2005 after 61 years, the longest career service in Langley’s history.) With jurisdiction over the highspeed tunnels and staf, Nichols’ organization was poised to lead the Nation in SST research. 

A signifcant initial act of Nichols and Baals was to challenge their staf with designing candidate 

supersonic transport confgurations for assessments of relative merits and research requirements of 

diferent approaches. With designs submitted by several staf members and teams, Langley began 

extensive in-house analyses and wind-tunnel tests in 1959 of 19 diferent SST designs referred to 

as supersonic commercial air transport (SCAT) confgurations, also known as SCAT-1 through 

SCAT-19. Over 7 years additional derivative confgurations were also evaluated, resulting in about 

40 concepts. Subsonic, transonic, and supersonic wind-tunnel tests of selected confgurations were 

conducted in the Langley facilities. In February 1963 four potential candidate confgurations were 

chosenformoredetailedanalysis.AlthoughLangley’sexpertiseinsupersonicaerodynamictechnology 

was ideally suited to defne aerodynamically efcient confgurations, assessment efort needed the 

unique experiences and systems-level expertise of industry to fully assess economic viability and 

technical advantages of the NASA confgurations. NASA, therefore, used part of its funding from the 

FAA to contract industry feasibility studies of NASA candidate confgurations in a SCAT 

feasibility study. 

Langley researchers conceived three of the four down-selected NASA SCAT confgurations— 

SCAT-4, SCAT-15, and SCAT-16—while the fourth confguration, SCAT-17, was developed at 

Ames Research Center. Te Langley designs were heavily infuenced by Langley’s expertise and 

experiences with arrow wing concepts and with the variable-sweep concept, also made feasible 

by Langley personnel. Many Langley leaders, including Mark Nichols, believed that variablesweep confgurations might be the only way to meet the contradictory demands of subsonic and 

supersonic fight. SCAT-4 was an elegant arrow wing design sculpted by Richard T. Whitcomb, 

and A. Warner Robins conceived the SCAT-15, which was an innovative variable-sweep arrow 

26 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Langley SCAT designs: SCAT-4 (above left), SCAT-15 

(above right), and SCAT-16. 

wing design that used auxiliary variable-sweep wing panels. Robins also designed the SCAT-16, 

which was a more conventional variable-sweep design. Following contracted industry evaluations 

by the Boeing Airplane Company and the Lockheed California Company—as well as an in-house 

assessment by NASA—for a representative SST mission (3,200-nmi mission with 125 passengers 

at cruise Mach of 2 or 3), it was concluded that a Mach 3 airplane with titanium (rather than 

aluminum) construction would be required. Te SCAT-16 and SCAT-17 designs were identifed 

by industry as the most promising confgurations, while the SCAT-15 and SCAT-4 were judged to 

have major issues. Te SCAT-15, with its dual wings, would have excessive weight; and the SCAT4, with its optimized arrow wing, would have major stability and control issues. 

Study results were reviewed at a conference on supersonic transport feasibility studies and 

supporting research held at Langley in September 1963. At this historically signifcant meeting, key 

papers that would infuence SST eforts for decades thereafter (to the present day) were presented 

by Langley researchers, and general perspectives and conclusions were drawn that have proven 

timeless. Key Langley presenters were Laurence K. (Larry) Loftin, Jr., Mark R. Nichols, Donald 

D. Baals, Roy V. Harris, Jr., F. Edward (Ed) McLean, Harry W. Carlson, M. Leroy Spearman, A. 

Warner Robins, Richard T. Whitcomb, Jack F. Runckel, Emanuel Boxer, Richard R. Heldenfels, 

Tomas A. Toll, Herbert F. Hardrath, Richard A. Pride, Robert W. Boswinkle, Jr., Harvey H. 

Innovation in Flight 27 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Hubbard, and Domenic J. Maglieri. Tis elite group of researchers quickly became national leaders 

in their respective felds of specialization for supersonic vehicles. 

Although review results were informative and illuminating, technologists recognized the 

tremendous amount of work that would have to be accomplished before the SST could be a feasible 

venture. Considerable research would be necessary to mature required technologies in virtually all 

areas, especially in propulsion and sonic boom. Despite the cautious conclusions of the 1963 study, 

which indicated that a commercial supersonic transport was not yet feasible, a few months later the 

FAA initiated a request for proposals (RFP) that began the U.S. SST Program. 

Several factors, including international politics and concern, had precipitated the decision to 

progress with the SST Program, even with the recognized technical immaturity and environmental 

challenges. Te Nation was still responding with concern and technical embarrassment to the Soviet 

Union’s launching of its Sputnik satellite on October 3, 1957; and an announced agreement of the 

British and French to collaborate on their own SST in 1962 sent waves of concern over potential 

technical inferiority through the U.S. technical community and Congress. On June 5, 1963, in 

a speech before the graduating class of the United States Air Force Academy, President Kennedy 

committed the Nation to “develop at the earliest practical date the prototype of a commercially 

successful supersonic transport superior to that being built in any other country in the world . . .” 

and designated the FAA as the manager of the new program. 

During FAA proposal evaluations of submissions from Lockheed, Boeing, North American, 

General Electric, Pratt and Whitney, and Curtiss-Wright, over 50 NASA personnel participated 

by defning evaluation criteria and evaluating proposals, with additional wind-tunnel testing and 

analytic studies wherever required. Most evaluators were from Langley, with William J. (Joe) 

Alford, Jr., serving as the lead interface with the FAA. Design requirements for the U. S. SST were 

driven by an attitude that the airplane had to be faster and larger than the competing Concorde 

design. Tus, the specifcations for the competition included a cruise Mach number of 2.7, a 

titanium structure, and a payload of 250 passengers. 

Te proposals of Boeing, Lockheed, General Electric, and Pratt and Whitney were accepted, but 

North American and Curtiss-Wright were eliminated early during evaluations. North American had 

chosen a delta/canard design (Model NAC-60) similar in some respects to the XB-70; however, the 

design’s aerodynamic drag was excessive. Boeing had been working potential supersonic transport 

designs since the mid-50s and had narrowed its candidates to either a delta design or a higher risk 

variable-sweep airplane potentially capable of more efcient and quieter operations during takeof 

and landing. Although concern existed over the weight of this confguration (massive 40,000-lb 

28 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

pivots would be required for the variable-sweep wing), it was chosen as the Boeing entry in the 

competition (Model 733-197). Lockheed chose a fxed-wing double-delta design (Model CL-823), 

which it felt would be a simpler, lighter airplane. Te performances of both designs were judged 

to be substantially short of the design goals and the contractors conducted extensive design cycles 

during the development process. Boeing’s fears of weight growth for the variable-sweep design 

had become real, and the confguration had required extensive changes due to other concerns, 

including moving the engines to the airplane’s rear under the horizontal tail (Model 2707-100). 

Te FAA advised Boeing and Lockheed to explore potential use of a derivative of the NASA SCAT15 design, which was showing substantial performance improvement over industry designs. 

Researcher Delma C. Freeman, Jr., inspects a free-fight model of the Lockheed L-2000 Supersonic Transport design (left) 

used in tests in the Langley 30- by 60-Foot Full-Scale Tunnel. 

Time-lapse photography shows the variable sweep wing of early Boeing Model 733-290 Supersonic Transport design. 

Free-fight testing was conducted in the Langley Full-Scale Tunnel. 

Innovation in Flight 29 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Boeing continued to develop its variable-sweep design (Model 733-290), encountering heating 

problems with the low horizontal tail position and pitch-up problems when the tail was moved to 

a T-tail position. In the next design cycle, a revised confguration (Model 733-390) retained the 

low tail and featured an arched fuselage, long landing gear struts, and upturned engine nacelles. 

Evolution of the fnal Boeing Supersonic Transport confguration. 

30 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Engineering mock-up of the Boeing 2707-300 Supersonic Transport. 

Te revisions, however, led to high weight and degraded performance. Ten, in a dramatic change, 

Boeing moved the four engines to beneath the horizontal tail (Model 2707-200). Meanwhile 

Lockheed had been concurrently developing a refnement of its double delta (Model 2000-7A) as 

well as a version of the refned NASA SCAT-15 (Model L-15-F). Boeing was ultimately declared the 

competition winner on December 31, 1966, with its 2707 design. After the award, Boeing fnally 

gave up on its variable-sweep airplane concept in 1968 and adopted a double-delta SST design, 

known as the Model 2707-300. Boeing complied with an FAA directive to continue analysis of its 

refned SCAT-15 design (Model 969-336C) and make a fnal confguration selection by late 1968. 

Boeing then selected the 2707-300 but continued its studies of the SCAT design. 

Research activities at Langley during the SST competition were, of course, intensive eforts 

involving wind-tunnel tests, controversial assessments, and consultation in several areas including 

aerodynamics, structures, materials, fight controls, noise, sonic boom, propulsion integration, 

aeroelasticity, landing loads, stability and control, operating problems, integration of SST and 

subsonic air trafc, and fight dynamics (including free-fight models). Detailed discussion of the 

very important contributions of Langley’s staf during the SST Program is not feasible in the 

present document, and the reader is referred to the formal NASA reporting publications listed in 

the bibliography for details and sources of additional information. 

Innovation in Flight 31 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Charles L. Ruhlin inspects a 1/17-scale semispan futter model of the Boeing 2707-300 during 

futter clearance testing in the Langley 16-Foot Transonic Dynamics Tunnel in 1970. 

An important contribution by Langley during this period was the vital role played by Harry W. 

Carlson, Roy V. Harris, Jr., and Wilbur D. Middleton in the development of analytical tools and 

theory for the design and evaluation of complex supersonic confgurations. Until their eforts, 

supersonic design processes were based on simple isolated wings, and attempts to combine volume 

and lift efects produced inconsistent results. Te breakthrough came when the Langley researchers 

attacked the problem by treating the efects of volume at zero lift and the efects of lift at zero 

volume—a much more manageable approach. Tey then added optimization codes to further 

embellish the analysis, and the resulting methodology was enthusiastically embraced by industry 

(especially the Lockheed SST team). Along with the advanced design process, Langley contributed 

the frst application of high-speed computers to the aerodynamic design of supersonic aircraft. Tis 

advance in technology, spearheaded by Roy Harris, dramatically shortened the time required for 

analysis of supersonic aerodynamics, resulting in a quantum leap in engineering analysis capability. 

First applied by Harris in his adaptation of a Boeing code for the prediction and analysis of zerolift supersonic wave drag, his computer methods shortened the manual task of analyzing wave 

drag for a single Mach number for a single confguration from over 3 months to just a few days. 

His work also represented the frst “wire frame” rendering of aircraft confgurations for analysis. 

Computer programmer Charlotte B. Craidon used Langley’s massive IBM 704 Data Processing 

32 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

System to provide Harris valuable assistance in his time-savings breakthrough. When Harris’ 

zero-lift drag program was coupled with analysis methods by Clinton E. Brown and F. Edward 

McLean for lifting conditions, the combination provided designers with powerful tools for analysis 

of supersonic aerodynamic performance. Industry has adapted many of these Langley-developed 

computer-based techniques and still uses them today. 

Langley’s application of computer use to supersonic aerodynamic design was a major 

breakthrough in design capability. Shown is the SCAT-15F design. 

Troughout the Boeing-Lockheed competition, NASA personnel at Langley, Ames, Lewis, and 

Dryden provided data and analysis to the individual contractors as well as consultation on how to 

improve their designs. Langley also pursued improved versions of its original SCAT concepts as 

potential alternatives to the Boeing and Lockheed designs. In 1964, advances in the sophistication of 

aerodynamic theory and computer codes at Langley allowed a team of Harry Carlson, Ed McLean, 

Warner Robins, Roy Harris, and Wilbur Middleton to design an improved SCAT confguration, 

called the SCAT-15F. Tis fxed-wing version of the earlier variable-sweep SCAT-15 confguration 

was designed using the latest, computer-based supersonic design methodology that Langley had 

developed, resulting in a L/D ratio of 9.3 at Mach 2.6, an amazing 25 to 30 percent better than the 

previous state of the art at that time. Te new Langley theories permitted the researchers to shape 

the wing with refex, twist, camber, and other parameters that nearly optimized its supersonic 

capability. When informed by the design team of the SCAT-15F’s projected performance, Larry 

Loftin (Langley’s top manager for aeronautics) did not believe the prediction. Subsequent windtunnel results, however, proved the estimates accurate and the SCAT-15F remains to this day 

one of the most aerodynamically efcient SST designs ever conceived. Carlson, McLean, Robins, 

Harris, and Middleton were awarded a patent for the SCAT-15F design in 1967. 

Innovation in Flight 33 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

SCAT-15F model being prepared for fow visualization tests in the 

Langley Unitary Plan Wind Tunnel. 

In 1966, the FAA requested that NASA examine the feasibility of an advanced domestic SST with 

acceptable levels of sonic boom. In conducting the necessary studies, a very advanced aerodynamic 

confguration was required. Analysis and further development of the SCAT-15F design quickly 

became a high priority activity at Langley, and Mark Nichols and Don Baals directed extensive 

computational analysis and wind-tunnel testing of several models in virtually every subsonic, 

transonic, and supersonic tunnel at Langley. Key facilities and test leaders included the 16-Foot 

Transonic Tunnel (Richard J. Re and Lana M. Couch), the 8-Foot Transonic Pressure Tunnel 

(Ralph P. Bielat and John P. Decker), the 30- by 60-Foot (Full-Scale) Tunnel (Delma C. Freeman), 

the Unitary Plan Wind Tunnel (Odell A. Morris, Dennis E. Fuller, and Carolyn B. Watson), 

and the High-Speed 7- by 10-Foot Tunnel (Vernon E. Lockwood and Jarrett K. Hufman). 

Te aerodynamic studies were augmented with an investigation of the predicted sonic boom 

characteristics of the confguration (Harry Carlson and Domenic Maglieri). 

Dynamic stability studies using free-fight models were also undertaken in the 30- by 60-Foot 

Tunnel, and piloted ground-based simulator studies of the handling qualities of the SCAT-15F 

during approach and landing were conducted using Langley simulators. Although studied by 

teams at both Lockheed and Boeing as an alternate confguration, the SCAT-15F was not adopted 

by either contractor during the SST Program. A major issue with the SCAT-15F design was its lowspeed stability and control characteristics. Te highly swept arrow-wing planform exhibited the 

longitudinal instability (pitch up) tendency typically shown by arrow wings at moderate angles of 

attack, as well as the possibility of a dangerous unrecoverable “deep stall” behavior. Te deep stall 

followed the pitch-up tendency and was characterized by an abrupt increase in airplane angle of 

34 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

attack to extremely high values (on the order of 60 degrees) where the L/D ratio became much less 

than 1, and longitudinal controls were inefective in reducing the angle of attack to those values 

required for conventional fight. Tis potentially catastrophic characteristic was unacceptable. 

Several Langley tunnel entries were directed at the pitch-up problem and the development of 

modifcations to alleviate it. 

Model of the SCAT-15F design mounted in the Langley Full-Scale Tunnel for tests to alleviate an 

unacceptable “deep stall” characteristic. 

Meanwhile, Marion O. McKinney and Delma C. Freeman, Jr. led exhaustive tests to alleviate 

the unacceptable SCAT-15F deep-stall characteristic in the Langley 30- by 60-Foot (Full Scale) 

Tunnel. After extensive testing, a combination of modifcations—including a 60-degree defection 

of the wing leading-edge fap segments forward of the center of gravity, a “notched” wing apex, 

Fowler faps, and a small aft horizontal tail—eliminated the deep-stall trim problem. 

All Langley research eforts to make the SCAT-15F a satisfactory confguration were quickly 

exchanged with Boeing on a virtually real-time basis during 1968, and formal reports were collated 

and transferred to the industry in 1969. Many lessons learned and design approaches derived 

from the SCAT-15F experience in solving low-speed problems were critical inputs for later NASA 

supersonic transport technology programs in the 1980s and 1990s. 

Innovation in Flight 35 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Despite promising progress in confguration research, the most critical obstacle to the SST 

remained the sonic boom issue. In June 1961, DoD, NASA, and the FAA had released the 

“Commercial Supersonic Aircraft Report,” known as the SST Bluebook. Tis report concluded 

that the development of a commercial supersonic transport was technically feasible, but that a 

major research and development program would be required to solve a major problem: the sonic 

boom. It became essential to know the level of sonic boom exposures that might be accepted 

by the public. Special supersonic overland fight projects were needed to augment disjointed Air 

Force data, calibrate theory, assess community reaction, defne structural damage due to booms, 

and assess boom efects on the environment. Domenic J. Maglieri, Harvey H. Hubbard, David 

A. Hilton, Vera Huckel, and Roy Steiner participated in these studies. Special fight tests were 

conducted at St. Louis from November 1961 through January 1962 (B-58 fights to confrm theory), 

at Edwards Air Force Base in 1963 (F-104 fights to determine efects of booms on two general 

aviation airplanes in fight and ground operations), and public exposure fights at Oklahoma City 

in 1964 and Chicago in 1965. Langley staf also participated in supersonic overland fights of an 

F-104 aircraft in Colorado to determine if booms could trigger avalanches on mountains covered 

with heavy snow. 

Te Ofce of Science and Technology established a Coordinating Committee on Sonic Boom 

Studies in 1965 under the management of the U.S. Air Force with members from the Air Force, 

NASA, Stanford Research Institute, the Environmental Science Services Administration, and 

the U.S. Department of Agriculture. Tis organization sponsored a concerted study of human 

acceptance and response of typical house structures to booms from 1966 to 1967 using overland 

fights of XB-70, F-104, F-106, B-58, and SR-71 aircraft at Edwards Air Force Base. NASA 

contributed data requirements, data scheduling, and test operations and boom research (including 

equipment installation, pressure signature acquisition, and analysis). Te program conducted over 

350 supersonic overland fights and extensive analysis of boom characteristics. 

In some tests, the public was exposed to sonic boom overpressures of up to 3 lbs/ft2

. SST overland 

fights were expected to result in levels of 1.5 to 2.0 lbs/ft2

. No one level of overpressure was 

found below which public acceptance was assured; but the results clearly indicated that levels 

of 1.5 to 2.0 lbs/ft2 were unacceptable for human exposure. Further, the results suggested that 

exposure must be considered in terms of frequency, intermittency, time of day or night, and the 

particular signature. 

Te Acoustical Society of America summed up the state of the art of sonic boom during symposia at 

St. Louis in 1965 and Houston in 1970. Survey papers were given on the nature of the sonic boom, 

sonic boom estimation techniques, design methods for minimization, atmospheric efects on sonic 

36 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

boom, the impact of airplane operation on sonic boom signature, and the efect of sonic booms 

on people. Te fnal survey paper at that conference emphasized that the operation of a supersonic 

transport would probably be constrained to supersonic fight over water only or supersonic in low 

population corridors. Research and technical meetings on sonic boom continued at a steady pace 

between 1965 and 1970, with NASA hosting conferences in Washington DC in 1967, 1968, and 

1970. Langley’s sonic boom experts, including Maglieri, Carlson, McLean, and Hubbard, were 

major participants in all the foregoing activities. 

Langley’s overall support of SST research also included several novel studies, one being an in-fight 

simulation of SST confgurations using the Boeing 367-80 transport (prototype for the 707 series). 

Langley contracted with Boeing to modify the “Dash 80” as a low-speed in-fight simulator for 

assessments of the approach and landing characteristics of representative double-delta and variableBoeing’s 367-80 was used at Langley for in-fight simulator studies of handling qualities 

of supersonic transport confgurations. 

Innovation in Flight 37 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

geometry SST concepts during instrument fight rules (IFR) conditions. Te program’s objectives 

were to study the handling qualities of two representative SST confgurations, evaluate potential 

problem areas and stability augmentation requirements, obtain indications of the minimum 

acceptable handling qualities, determine efects of operation on the unconventional “backside” 

of the power required curve, and obtain approach and landing data applicable to criteria and 

certifcation requirements for SST transports. Flown at Langley by pilots from NASA, Boeing, 

the FAA, and airlines from May to October 1965, the venerable Dash 80 used computer-based 

aerodynamic inputs from Langley staf to replicate the responses of SST designs to pilot inputs, 

producing pioneering information on the handling qualities and control system requirements for 

SST designs during approach and landing. Key Langley participants in the program included 

Project Manager Robert O. Schade, Harold L. Crane, Albert W. Hall, William D. Grantham, 

Robert E. Shanks, Samuel A. Morello, and test pilots Lee H. Person and Jere B. Cobb. Philip 

M. Condit, a new Boeing engineer, was the lead Boeing participant for the study as an expert in 

aerodynamics and stability and control. Condit later became President of Te Boeing Company in 

1992 and then Chief Executive Ofcer in 1996. 

Amid extensive controversy, technical issues, international politics, and environmental concerns, 

the U.S. Congress reduced the SST Program’s funding in December 1970 and canceled the 

program in March 1971. Te House, by a vote of 217 to 203, deleted all SST funds from the 

Department of Transportation (DoT) appropriation for fscal year 1972. An amendment to restore 

SST funds was defeated in the Senate 51 to 46. On May 1, 1971, the Senate approved $156 

million in termination costs. Tus, after 8 years of research and development and an expenditure of 

approximately $1 billion, the United States withdrew from the international supersonic transport 

competition. Te program’s cancellation was a severe blow to the enthusiasm of NASA researchers, 

especially the Langley participants in supersonic cruise research. In addition, the cancellation 

dampened and obscured the signifcant impact of advances in the state of the art that had occurred 

due to Langley’s involvement. Supersonic aerodynamic theory and design methodology had been 

aggressively advanced and validated thanks to the introduction of high-speed digital computer 

codes that included the efects of extremely complex aerodynamic phenomena. Langley’s researchers 

had also contributed unprecedented advances in the knowledge of sonic boom phenomena. Te 

signifcance and understanding of sonic booms had clearly not been fully appreciated by the 

technical community before the SST program. Langley personnel developed and validated sonic 

boom estimation procedures, including analysis of near-feld sonic boom characteristics that led to 

a new feld of sonic boom minimization. Extensive participation by Langley during measurement 

of sonic booms from various supersonic aircraft, including data gathered on atmospheric efects and 

possible damage to dwellings, resulted in extremely signifcant information for future supersonic 

aircraft programs. 

38 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Other Langley Research center eforts and contributions during the SST Program included valuable 

improvements in understanding the characteristics, design variables, and fabrication problems of 

titanium material. As previously discussed, conventional aluminum material will not survive in the 

500 °F temperature environment encountered at cruise speeds of Mach 2.7 and above, requiring 

the use of alternate materials. Design methodology, including the use of advanced computer codes 

for structural design, was developed. Also, Langley began a major efort in stratospheric emission 

technology, contributing to a much better understanding of atmospheric pollution phenomena. 

Finally, Langley researchers contributed a substantial database on stability, control, and handling 

qualities for advanced arrow-wing type confgurations that emerged as the most efcient approach 

for future SST designs. 

The Supersonic Cruise Research Program 

Program Genesis 

In early 1972, the Nixon administration directed NASA to formulate a supersonic research 

program that would answer difcult technical and environmental problems requiring resolution 

for a viable commercial supersonic transport. Under the leadership of William S. Aiken, Jr., of 

NASA Headquarters, an intercenter team formulated a program called the NASA Advanced 

Supersonic Technology (AST) Program. Agency lead role for the program was assigned to Langley. 

Te new program’s goals were to build on the knowledge gained during the SST program and to 

provide—within 4 years—the supersonic technology base that would permit the United States to 

keep options open for proceeding with the development of an advanced supersonic transport, if 

and when it was determined that it was in the national interest. 

Several events at Langley infuenced the ultimate leadership of the AST Program. At the time of 

the request, Robert E. Bower had become Director for Aeronautics and an Aeronautical Systems 

Ofce (ASO) had been formed under Tomas A. Toll. Within ASO, the Advanced Supersonic 

Technology Ofce (ASTO) headed by David G. Stone was given responsibility for the emerging 

AST activities. In 1971, Langley’s Cornelius (Neil) Driver had been assigned to a temporary position 

for presidential and congressional assistance in assessing emerging military aircraft (U.S. Navy F14 and U.S. Air Force F-15). Driver spent his early career in supersonic wind-tunnel research, 

including participation in the XB-70 and early SST studies. During his congressional assignment, 

he became personal friends with ex-test pilot William M. (Bill) Magruder, the top FAA ofcial 

in the fnal, turbulent months of the SST Program. Magruder regarded the possible breakup of 

industry SST design teams as a potential disaster for national interests in aviation and impressed 

Driver with devising a program that would keep the national expertise in place. Upon his return 

Innovation in Flight 39 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

to Langley, Driver joined the ASTO organization as Stone’s deputy and became active in planning 

the AST efort, which maintained a sensitivity to including industry teams in the NASA efort. 

Meanwhile, Mark Nichols’ High Speed Research Division had started to ramp up planning for a 

technical program in support of AST. 

In 1972, an AST Working Group was formed to defne a technical program plan under the 

leadership of F. Edward McLean. McLean, who would later become manager of the technical 

AST efort in 1974, was also a key participant in the activity’s startup and operations. His 

outstanding contributions in the areas of advanced aerodynamics and sonic boom theory were 

impressive credentials for his role in the program. Like Driver, his technical expertise in supersonic 

confgurations, industry relations, and hard-driving personal dedication and management style 

were keys to the successful accomplishments of the new NASA activity. Both Driver and McLean 

operated within the new Aeronautical Systems Division (ASD) of Adelbert L. (Del) Nagel that 

replaced Toll’s ofce in 1974. Driver headed the Vehicle Integration Branch while McLean 

led the Advanced Supersonic Technology Project Ofce. Langley was extremely fortunate to 

have two such outstanding leaders assigned to the AST Program. In 1978, McLean retired 

and Nagel departed NASA for Boeing. Driver then headed up the ASD organization, while 

management of the Advanced Supersonic Technology Ofce passed from Vincent R. Mascitti to 

Domenic Maglieri. 

Because of concern that potential opponents of future SST programs would misinterpret the 

program acronym as a program for developing an advanced supersonic transport, the name was 

changed to Supersonic Cruise Aircraft Research (SCAR) in 1974. Further sensitivity over the use 

of the word “aircraft” led to yet another modifcation in the program name, resulting in the fnal 

name, Supersonic Cruise Research, or SCR, in 1979. Te SCR Program’s pace and funding were 

intentionally cut back by Congress to delay the issue of another SST battle, and the funds available 

to NASA researchers were extremely limited. Tis situation led to a fundamental integrated 

technology approach, which NASA referred to as a “focused” program. Te SCR activity involved 

all NASA aeronautical centers and many aerospace companies, research organizations, and 

universities. Although the program was managed by NASA Headquarters, day-to-day operations 

were the responsibility of Langley’s ASD with research tasks being accomplished by NASA 

Center stafs and industry. the program’s sponsored disciplinary research included aerodynamic 

performance (Langley and Ames), propulsion (Lewis), structures and materials (Langley, Dryden, 

and Ames), stability and control (Ames, Dryden, and Langley), and stratospheric emissions impact 

(all Centers). 

Te program also included an important element known as systems integration studies, which 

40 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

attempted to quantitatively measure the potential impact of various disciplinary technology 

advances on representative supersonic cruise aircraft. Te systems integration activity participants 

included Boeing, Lockheed-California, and McDonnell Douglas, as well as in-house NASA and 

local Langley contractor (Ling-Temco-Vought) personnel. In addition to the enthusiastic and 

capable contributions of industry airframe companies, SCR eforts included the participation 

of propulsion groups from the General Electric Company and the Pratt and Whitney Aircraft 

Company. In this approach, the Nation was able to maintain the invaluable expertise and talent 

that had participated in earlier SST studies, as desired by Bill Magruder and Neil Driver. 

Initially, a baseline supersonic transport confguration, known as the AST-100, provided a common 

reference for the integration teams from industry and NASA. As the program evolved, Rockwell 

International also came onboard, and each team developed a refned design based on a diferent 

cruise speed, generating fve slightly diferent confgurations with cruise Mach numbers ranging 

from 2.2 to 2.7. McDonnell Douglas chose a highly swept arrow-wing confguration similar to the 

Mach 2.7 NASA SCAT-15F but designed for a lower cruise Mach number of 2.2. Lockheed also 

chose an arrow-wing concept designed for cruise at 2.55, but with two of its four engines located 

unconventionally above the wing for noise shielding. Te NASA concept used an improved version 

of the SCAT-15F with a proposed cruise Mach number of 2.7. 

Aerodynamics 

Within the aerodynamic performance element of the SCR Program, major tasks involved 

developing and testing advanced aerodynamic supersonic transport concepts, as well as developing 

and validating aerodynamic design and analysis tools. Work areas included concept development, 

theory development, and sonic boom. 

As previously discussed, the state of the art in supersonic aerodynamic design technology had 

been brought to a high level of maturity by the SST program’s end in 1971. Te unprecedented 

aerodynamic efciency of the NASA SCAT-15F stood as an example of what could be achieved, 

but the highly efcient supersonic arrow-wing concept faced defciencies in subsonic performance, 

resulting in major issues in of-design performance and poor noise characteristics. Tus, a major 

efort was directed to improve the low-speed behavior of arrow-wing concepts during the SCR 

Program, whereas relatively limited efort was expended on improving supersonic cruise efciency. 

Tis low-speed research was especially critical from the McDonnell Douglas perspective, and 

numerous models of various arrow-wing confgurations were explored cooperatively in the Langley 

30- by 60-Foot (Full Scale) Tunnel, the Langley 7- by 10-Foot High Speed Tunnel, and the 

Langley V/STOL Tunnel (now the Langley 14- by 22-Foot Tunnel), as well as tunnels at Ames. 

Innovation in Flight 41 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

An exhaustive low-speed aerodynamic program led by Langley’s Paul L. Coe, Jr., and Joseph L. 

Johnson, Jr., explored methods to improve low-speed performance (lift and L/D) while retaining 

satisfactory stability and control. Te scope of research included extensive studies of wing planform 

efects and leading-edge devices as well as innovative technical concepts, such as thrust vectoring 

to augment lift. Additional studies—for example, an evaluation of the low-speed characteristics 

of an advanced blended arrow-wing confguration designed by A. Warner Robbins—were also 

conducted. Te collaborative eforts with industry teams led to solutions for many of the stability 

and control problems, and the low-speed aerodynamic efciency of arrow-wing concepts was 

dramatically increased. 

In addition to wind-tunnel research to improve low-speed aerodynamic characteristics, Langley’s 

staf also conducted ground-based and in-fight piloted simulator studies of the low-speed handling 

characteristics of advanced supersonic transports. In 1977, William D. Grantham and Luat T. 

Nguyen led simulator studies of two advanced confgurations: a canard version of the SCAT-15F 

and a powered-lift arrow-wing airplane with engines located over and under the wing. Conducted in 

a fxed-base simulator at Langley and in fight using the Calspan Total In-Flight Simulator (TIFS) 

airplane, the study defned details of the longitudinal and lateral directional stability augmentation 

systems required for satisfactory characteristics. Another study highlight was the identifcation of 

a critical roll-control power defciency for the airplanes during crosswind operations. Tis problem 

is inherent for the highly swept supersonic transport confguration, and these results provided 

guidance for meeting handling quality requirements. 

Much of the data, concepts, and design methodology derived from aerodynamic research in the 

SCR Program proved invaluable in other NASA and DoD programs. One outstanding example of 

the value of Langley’s supersonic aerodynamic design expertise and methods was the cooperative 

venture initiated by a request from General Dynamics (now Lockheed Martin) for a joint design 

efort to develop a supersonic cruise wing for the F-16 fghter. General Dynamics was in close 

communication with the Langley staf during the SCR period and viewed the vast experience and 

mentoring of the researchers in supersonic wing design methodology as an extremely important 

ingredient of the new fghter design. As discussed in NASA SP-2000-4519, Partners in Freedom, 

this joint activity produced the highly successful F-16XL version of the fghter. 

Sonic Boom 

In 1972, Christine M. Darden and Robert J. Mack continued to advance sonic boom theory. 

Computer codes were developed to advance boom predictions for various atmospheric conditions, 

42 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Te F-16XL benefted from a cooperative supersonic wing design study between 

Langley and General Dynamics. 

nose-bluntness efects were analyzed, and models were fabricated for wind-tunnel tests to verify 

theories. Six-inch models of three wing-body concepts for cruise at Mach 1.5 and Mach 2.7 were 

prepared for testing and were at that time the largest sonic boom models tested in the Langley 

4- by 4-Foot Unitary Plan Wind Tunnel (models tested in the tunnel during the 1960s were from 

0.25 in. up to 1 in.). Model size was driven by the need to measure far-feld signatures to ensure 

linear theory was valid—about 30 body lengths away. As confdence in the extrapolation methods 

grew, signatures could be measured closer to the body and model size could become larger. 

Te SCR Program continued to explore airplane shaping for minimizing sonic booms. Various 

design concepts of vehicles having minimum boom design-shaped signatures were derived, and 

other studies indicated that by altering the boom signature shock rise time and waveform from that 

of a normal far-feld N-wave, the perception of loudness was reduced. Darden and Mack were in 

the process of additional planning when the SCR Program was canceled, and NASA funding for 

sonic boom research was then dropped for nearly 6 years. 

Innovation in Flight 43 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Stability and Control 

Te stability and control work area in SCR developed methods for accurately assessing the stability 

and control characteristics and requirements for large, fexible supersonic cruise aircraft, including 

the design of active control systems. Tis area was led by Ames and Dryden, with some participation 

by Langley in the active controls area. 

Propulsion 

Te propulsion element of SCR was directed at the development of a propulsion system concept 

that would efciently meet the conficting requirements of subsonic and supersonic operations. 

Specifc problems addressed by this critical area at the Lewis Research Center included noise and 

pollution issues. 

Te accomplishments and contributions of the superb propulsion research conducted at Lewis 

under sponsorship of the SCR Program covered engine concepts, noise, and emissions. Many 

of these activities resulted in design methodology, concepts, and technologies that were rapidly 

matured for supersonic cruise vehicles. Te frst 3 years of propulsion-related activity by Lewis and 

its industry partners resulted in the most important propulsion development in the SCR Program: 

the variable-cycle engine. In the variable-cycle engine concept, a special engine fow-through 

design permits operation like a turbojet during supersonic cruise and a turbofan during subsonic 

fight. Both General Electric and Pratt & Whitney conducted engine test-stand assessments of 

proposed variable-cycle confgurations. Te engine concepts did not represent signifcant advances 

in propulsion cycle efciencies over previous supersonic turbofan or turbojet engines. Instead, the 

new engine concepts provided airfow control appropriate for each phase of fight, thereby enabling 

low specifc fuel consumption, less weight, and reduced noise. NASA then spun of a Variable 

Cycle Engine (VCE) Program from the SCR Program in 1976, maintaining a close relationship 

and communications between the two eforts at Langley and Lewis. 

Noise technology was a major part of the SCR Program eforts, including exploratory studies of 

inverted velocity profle nozzles, mechanical noise suppressor technology, acoustic shielding (such 

as placing engines in an over/under arrangement on the wing), and the use of “minimum noise” 

fight profles during terminal area operations. Te substantial noise reduction potential of these 

concepts gave rise to optimism about the potential noise compliance for future supersonic cruise 

aircraft. Te situation was a vast improvement over the state of the art at the end of the SST 

Program in 1971, when the only noise reduction technology was a vastly oversized, heavy noise 

suppressor system that severely degraded airplane mission capability. 

44 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Structures and Materials 

SCR-sponsored structures and materials research attempted to develop structural concepts and 

materials that would withstand the large load and temperature variations experienced during 

representative supersonic transport fight operations. Work areas included structural concepts, 

development of design data and tools, material applications, and fuel-tank sealants. Richard R. 

Heldenfelds from the Structures Directorate of Langley provided leadership for most of these 

activities (tank sealant work was led by Ames). 

HighlightsoftheLangleycontributionsinstructuresandmaterialsincludedimprovedcomputational 

methods for structural design and analysis, with an emphasis on rapid design methods to produce 

structures that met the requirements for strength, divergence, and futter, including the use of active 

controls. Other SCR-sponsored research eforts included the development of low-weight, lowcost structural concepts with low-cost fabrication techniques. Many consider the most important 

output of the entire SCR Program to be a demonstration of the potential use of superplastic 

forming and difusion bonding (SPF/DB) of titanium. Te process involves heating a sheet of 

titanium in a mold until the titanium reaches a malleable temperature. Gas is then injected into 

the mold, and the titanium is either blown into a shape or bonded to another titanium sheet. Using 

this revolutionary process, potential applications to various parts seem limitless. During the course 

of the SCR activities, Rockwell (which had accrued experience with the technique as part of its 

XB-70 activities) and McDonnell Douglas fabricated SPF/DB panels and structural components. 

Using the SPF/DB process in the design of supersonic transports showed signifcant advantages over 

the titanium honeycomb that was used in the Boeing SST design of the 1960s. For example, 

projected weight savings of changing to a titanium SPF/DB sandwich construction for a fuselage, 

compared with titanium skin stringer concepts, indicated a reduction of fuselage weight by 

about 22 percent. 

Emissions 

Research in stratospheric emissions was a critical area directed at assessing the impact of upper 

atmosphere pollution by high-fying aircraft. Issues addressed included the chemistry, propagation, 

and dissipation of jet wakes as well as the natural causes of pollution. Te NASA Ofce of Space 

Science funded and managed research in this area after October 1976. A number of emission research 

programs had emerged after 1972, including the Climatic Impact Assessment Program (CIAP), 

the High Altitude Pollution Program (HAPP), and the NASA Emissions Reduction Research and 

TechnologyProgram.AmajorLewisundertaking,theEmissionsReductionResearchandTechnology 

Programidentifedmeansforreducingthepollutionofjetengines.Byfarthemostimportantoutcome 

Innovation in Flight 45 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

of the 1970s research was the accidental discovery of the ozone problem. By 1980, DoT and NASAfunded research had demonstrated that SSTs were less threatening to the ozone layer than initially 

thought, leading to a relatively well-accepted belief that future combustor technology could lead 

to acceptable transport confgurations. By-products of this research activity included the fact that 

the major threat to the Earth’s ultraviolet shield was chlorofuoromethanes (CFM), 

which subsequently led to a ban on CFM-powered aerosol sprays in the United States 

in 1978, a worldwide ban on CFM manufacture in 1987, the formalization of stratospheric research 

at NASA, and a permanent NASA program to monitor the stratosphere’s composition. 

Other Activities 

Teprogram’smissionperformanceintegrationelementassessedtheimpactofindividualdisciplinary 

advances, including a measurement of the technological advances of the integrated disciplines. Te 

work was critical to determine whether progress was being made toward an economically viable, 

environmentally acceptable commercial supersonic transport. Along with providing systems-level 

progress assessments of technology advances for industry and NASA vehicle concepts, systems 

studies enabled the SCR team to assess the impact of vehicle sizing, wing/body blending, and 

large-payload supersonic airplanes. 

Te SCR Program encouraged innovation and new ideas from the disciplinary specialists. Research 

stimulated at Langley included several examples of novel technology, such as active control of 

aeroelastic characteristics (especially futter), resulting in the potential for signifcant structural 

weight savings and cost. Active landing gear technology was pursued by the structural dynamics 

group at Langley, providing concepts to reduce landing loads on the supersonic transport’s structure 

during landing impact and ground taxi operations. 

Unconventional supersonic cruise confgurations were also examined, including the use of a 

novel twin-fuselage SST confguration for high-payload, high-productivity applications. John C. 

Houbolt and M. Leroy Spearman initially pursued the twin-fuselage confguration for enhanced 

performance and productivity for subsonic transports. Teir approaches used dual fuselages as 

wingtip “end plates” and an unswept, long-chord wing section between the fuselages. Houbolt was 

interested in such designs for favorable trades between geometric internal volume and aerodynamic 

skin friction drag. Spearman’s interest, on the other hand, was in larger capacity (900 passengers) 

transports with acceptable “footprint” and ground handling. Te interest in supersonic transport 

applications was generated by results of computational and wind-tunnel studies conducted by Samuel 

M. Dollyhigh and other Langley researchers. Te aerodynamic principle involved in the supersonic 

application is using a pressure feld generated by one airplane component to favorably modify 

46 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Unconventional supersonic transport designs, such as this high-payload twin-fuselage concept, 

were explored in the Supersonic Cruise Research Program. 

A 1981 conceptual Boeing design for a supersonic business jet. 

Innovation in Flight 47 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

the pressures on another component. In the twin-fuselage confguration arrangement, supersonic 

drag is reduced because of the positive fuselage forebody compression pressures emanating from 

each forebody and impinging on the rearward facing surface of the half portion of the adjacent 

body, thereby increasing the afterbody pressure and reducing the drag. Langley data indicated 

that a two-fuselage vehicle could have 25 to 30 percent lower pressure drag than a single 

fuselage confguration. 

Finally, the SCR interactions with industry sparked the interest of a number of industry design 

teams for supersonic business jets. Several confgurations were brought forward, and the potential 

benefts of a smaller airplane over a large supersonic transport in areas such as sonic boom and 

noise were recognized. Years later, in the early 2000s, the concept of supersonic business jets would 

again arise, as will be discussed. 

Termination of the SCR Program 

Nearly 1,000 reports and presentations resulted either directly or indirectly from research supported 

by the SCR Program. In addition to day-to-day contact with pertinent industry personnel, annual 

reviews of the disciplinary research were conducted, and two major NASA conferences were held 

at Langley in 1976 and 1979, both well attended by members of the aerospace, military, and 

academic communities. Technology transfer from the program was especially efective because of 

the intimate working relationships that existed with program participants and the focused nature 

of research eforts. Te approach of active industry involvement in NASA research activities has 

been continually demonstrated as the most productive approach to technology maturation and 

application of advanced concepts, and the legacy of the SCR Program serves as an outstanding 

example of this success. 

In the late 1970s, the anti-SST movement was still very active in the United States, worldwide fuel 

shortages and price increases were encountered, the Concorde had proven an economical disaster, 

and low-fare availability on wide-body subsonic transports attracted the interest of the fying 

public. NASA faced major funding issues in its Space Shuttle programs, and the Agency decided to 

terminate the SCR Program in 1982. Although the program did not result in a second-generation 

SST, it produced technology of immediate value to the subsonic transport industry, including 

SPF/DB, materials such as advanced metal matrix composite structures, and aerodynamic design 

tools such as advanced fow modeling. 

48 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

The NASA High Speed Research Program 

Program Genesis 

After cancellation of the SCR Program, the sporadic NASA interest in supersonic transports 

once again greatly diminished. In November 1982, an interagency group under the direction 

of the White House Ofce of Science and Technology Policy (OSTP) conducted a study on the 

state of aeronautical research and the role of the government in supporting that research. Te 

study concluded that revolutionary advances in aeronautics were possible and that industry and 

government must work together to realize the benefts. In 1985, a committee of government, 

industry, and academic experts reviewed the study and specifed three goals for future research, 

one of which was Supersonic Goal: To Attain Long-Distance Efciency. It was noted that from a 

strategic and economic perspective, the Pacifc areas were constrained by distance, a factor adding 

signifcance to the supersonic goal. In February 1987, OSTP reinforced the supersonic research 

goals by adding emphasis on the need to resolve environmental issues and proposed a plan to 

achieve the goals. 

Meanwhile, a new subject in high-speed fight abruptly burst on the international scene with 

widespread support and enthusiasm. Hypersonics, once an area of extremely low national interest 

(at one point in the 1970s, Langley was the only signifcant United States participant in hypersonic 

research), suddenly became a high priority target, as a result of emerging hypersonic propulsion 

concepts within NASA and DoD, with perceived military and civil benefts. Te rising support 

for hypersonics even penetrated the White House, and in his 1986 State of the Union Address, 

President Ronald W. Reagan praised the virtues of an “Orient Express,” a Mach 25 hypersonic 

transport that could fy from New York to Tokyo in 2 hours. 

In response to the OSTP call for technology development to support a long-range high-speed 

transport as one of the national goals in aeronautics, NASA awarded 2-year contracts for market 

and technology feasibility studies of a high-speed civil transport (HSCT) to Boeing Commercial 

Airplanes and Douglas Aircraft Company in October 1986. Te scope of the studies requested a 

broad consideration of civil supersonic, hypersonic, or transatmospheric vehicles for high-speed 

transportation. Tese studies were coupled with independent in-house NASA team assessments. 

Te assessments included the market potential of an HSCT, candidate vehicle concepts and the 

critical technologies that each concept would require, and the environmental issues relevant to 

each concept. Environmental issues were the focus during fnal contract phases in order to verify 

feasible technological resolutions. 

Innovation in Flight 49 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Te in-house Langley systems studies were organized by Charlie M. Jackson (Chief of the HighSpeed Research Division) and his deputy, Wallace C. Sawyer, and conducted by a team led by 

Samuel M. Dollyhigh and Langley retiree A. Warner Robins. Te results of the industry studies, 

as well as the in-house study, dismissed the “Orient Express” hypersonic transport concept as 

infeasible due to its projected impact on airport infrastructure costs, technology shortcomings, 

and vehicle performance limitations. At the same time, other studies were underway including a 

major workshop at Langley in January 1988 to discuss the status of sonic boom methodology and 

understanding. Industry and NASA both concluded that an economically viable HSCT would be 

feasible if the environmental issues, such as noise and emission problems, could be resolved. Te 

cruise speed recommended from the study results was in the range between Mach 2 and 3.2. 

High-Speed Research Phase I 

As a result of these systems studies, and growing U.S. industry and government concern over the 

threats of emerging European and Japanese interests in a second-generation SST, NASA formally 

initiated a High Speed Research (HSR) Program in 1990 to identify and develop technical and 

economically feasible solutions to the many environmental concerns surrounding a secondgeneration supersonic transport. In the phase I HSR studies, all eforts were directed toward 

resolution of the three great environmental demons that had devastated the frst U.S. SST program: 

ozone depletion, airport and community noise, and sonic boom. Before the HSR activities could 

be assured of further support from Congress or industry, the HSR team had to prove that the 

HSCT would be ozone-neutral, that it could meet the current airport noise requirements (FAR 36 

stage III), and that the sonic boom generated by the HSCT could be made acceptable for overland 

or overwater fight. Te HSCT envisioned by the HSR participants would fy 300 passengers at 

2.4 times the speed of sound—crossing the Pacifc or Atlantic in less than half the time presently 

required on modern subsonic, wide-bodied jets—at an afordable ticket price (estimated at less 

than 20 percent above comparable subsonic fights), and be environmentally friendly. Te Mach 

2.4 cruise speed was selected by program participants because of a desire to use conventional jet 

fuel at worldwide locations instead of more exotic or expensive fuels required for higher cruise 

speeds. At Langley, Allen H. Whitehead, Jr., was assigned responsibility for the airframe-related 

research of phase I HSR studies, while Robert J. Shaw of Lewis Research Center managed the 

propulsion elements from Lewis. Langley took an aggressive lead in attacking the environmental 

issues of phase I. In the sonic boom area, for example, a major workshop had been held at Langley 

in January 1988 to discuss the status of sonic boom methodology and understanding. 

Te frst HSR workshop was hosted by NASA Langley in May 1991 at Williamsburg, Virginia. 

Troughout the program’s duration, NASA and its industry partners placed special emphasis on 

50 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Researcher David E. Hahne inspects a 1/10-scale model of a McDonnell 

Douglas Mach 2.2 transport in the Full-Scale Tunnel in 1992. 

the fact that technology included in the HSR Program was commercially sensitive, and all data and 

program results throughout the program’s lifetime were protected by a special limited distribution 

system. Many research contributions of the HSR Program are still sensitive, and the discussion 

herein will only highlight the scope of activities. 

Attendance at the frst HSR workshop was by invitation only and included industry, academic, 

and government participants who were actively involved in HSR activities. Te workshop 

sessions were organized around the major task elements, which addressed the environmental 

issues of atmospheric emissions, community noise, and sonic boom. Sessions included airframe 

systems studies, atmospheric efects, source noise, sonic boom, propulsion systems, emission 

Innovation in Flight 51 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

A McDonnell Douglas High-Speed Civil Transport concept during the early High Speed Research Program 

reduction, aeroacoustics and community noise, airframe/propulsion integration, airframe and 

engine materials, high lift, and supersonic laminar fow control. Key Langley presenters included 

Samuel D. Dollyhigh, Ellis E. Remsberg, William L. Grose, Lamont R. Poole, John M. 

Seiner, Christine M. Darden, Langley retirees Domenic J. Maglieri and Percy J. (Bud) Bobbitt, 

Robert A. Golub, Gerry L. McAninch, Kevin P. Shepherd, Tomas T. Bales, Paul L. Coe, Jr., 

and Michael C. Fischer. 

At the end of phase I studies, the industry and NASA team had provided convincing results that 

airport noise and emission problems could be conquered with advanced technology, but the lack 

of a solution to the sonic boom issue resulted in a restriction to overwater supersonic fight. Major 

questions remained as to the airplane’s economic viability and the acceptability of the advanced 

technology costs. 

High-Speed Research Phase II 

Phase II of the HSR Program began in 1995 and was designed to assess and enhance the economic 

competitiveness of the HSCT. NASA and its industry team had begun to crystallize the advocacy 

and benefts of the HSCT. Industry experts predicted that the number of fights to the Pacifc Rim 

would quadruple by the next century, spurring demand for over 500 next-generation supersonic 

passenger transports. Terefore, the frst country to develop a supersonic transport that was 

competitive (i.e., less than a 30-percent ticket surcharge) with existing fares for subsonic transports 

would capture a signifcant portion of the long-haul intercontinental market. 

52 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Technician Michael E. Ramsey inspects a 19-ft long model of the High-Speed Civil Transport 

Reference H confguration during tests of takeof and landing characteristics in 

Langley’s 14- by 22-Foot Subsonic Tunnel. 

Te NASA HSR phase II team was led by the Agency’s HSR Program Ofce at Langley and 

was supported by Dryden Flight Research Center, Ames Research Center, and Lewis Research 

Center. Major industry partners in the HSR Program were Boeing Commercial Airplane Group, 

McDonnell Douglas Aerospace, Rockwell North American Aircraft Division, General Electric 

Aircraft Engines, and Pratt & Whitney. 

Te HSR Program Ofce was led by Wallace C. Sawyer, who began as the Agency’s Director of the 

High-Speed Research Program in 1994. Sawyer was assisted by his deputy Alan W. Wilhite, and 

research tasks were accomplished by a unique teaming of NASA-industry team, with personnel 

divided into integrated disciplinary work units. As the program progressed, Boeing was declared 

the industry manager for HSR activities, and the program ofce at Langley instituted technology 

ofces focused on topics that included technology integration (William P. Gilbert), aerodynamic 

performance (Robert L. Calloway), materials and structures (Rodney H. Ricketts), environmental 

impact (Allen H. Whitehead, Jr.), and fight deck technology (Daniel G. Baize). 

Innovation in Flight 53 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Advanced technologies in the areas of aerodynamics, structures, propulsion, and fight deck 

systems were applied to a baseline Mach 2.4 vehicle concept called Reference H. In late 1995, 

the participants produced a new transport design known as the Technology-Concept Airplane 

(TCA). Te TCA was also a Mach 2.4 aircraft with a 300-passenger capacity and a range of more 

than 5,000 nmi. During HSR phase II, NASA was spending a quarter of its annual $1 billion 

aeronautics budget for high-speed research. 

Phase II technology advances needed for economic viability included weight reductions in every 

aspect of the baseline confguration because weight afects not only the aircraft’s performance 

but also its acquisition cost, operating costs, and environmental compatibility. In materials and 

structures, the HSR team attempted to develop technology for trimming the baseline airframe 

by 30 to 40 percent; in aerodynamics, a major goal was to minimize drag to enable a substantial 

increase in range; propulsion research was directed at environment-related and general efciency 

improvements in critical engine components, such as inlet systems. Other research involved 

ground and fight simulations aimed at the development of advanced control systems, fight deck 

instrumentation, and displays. 

In addition to maintaining close coordination of industry and NASA research activities on a daily 

basis, the various disciplinary ofces within the HSR Program Ofce organized and conducted 

extensive workshops in their technical areas, summarizing and disseminating the latest advances in 

technology and assessing the progress toward goals set for the HSR Program. For example, annual 

HSR sonic boom workshops from 1992 to 1995 brought together NASA’s scientists and engineers 

with their counterparts in industry, other Government agencies, and academia to review the 

program’s sonic boom element. Specifc objectives of these workshops were to discuss theoretical 

aspects of sonic boom propagation, experimental results of boom propagation, results of boom 

acceptability studies for humans and animals (including sea life), and low-boom confguration 

design, analysis, and testing. 

In the sonic boom area, the frst low-boom designs developed by Christine Darden and Bob Mack 

as part of the HSR Program were updated to include more features of real airplanes than the simple 

fat wing-body designs that had been used in signature modifcation testing of the mid 1970s. In 

1990, Mach 2 and Mach 3 twisted wing-body-nacelle model concepts were designed to produce 

tailored “fat-top” or “ramp” type signatures. During wind-tunnel tests of these models, large, 

unpredicted shocks emanating from the fow-through nacelles were encountered (the frst windtunnel models had no fow-through nacelles). Te next generation of low-sonic boom designs, 

begun in 1991, had two objectives: to correct the nacelle integration concerns and to improve the 

overall aerodynamic performance of the low-boom concept. Analysis methods were modifed to 

54 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

ensure that inlet shocks were predicted. Also, for the frst time analysis was accomplished with 

powerful, nonlinear computational fuid dynamics (CFD) methods. Because the traditionally used 

sonic boom theory is only valid at mid- to far-feld distances, CFD methods are the only means of 

generating a near-feld signature, one that can be compared directly with wind-tunnel data, and 

one wherein signature features can be directly correlated with confguration features. 

For several models in this cycle, CFD methods were used to iteratively design the desired signature. 

Te use of CFD had also become more imperative as wind-tunnel models became larger in order 

to incorporate the increasingly realistic features, such as twist and camber, and nacelles. Larger 

models necessitated measuring the signatures at closer and closer distances. All sonic boom models 

built during the HSR Program were 12 in. long and measurements were taken at 2 to 3 bodylengths away. Test results on this generation of models met with moderate success. Shocks from 

the nacelles were successfully embedded within the expansion wave of the vehicle and, while the 

predicted ground signature was not an N-wave, the slope of the pressure growth was much steeper 

than predicted. Because the initial signatures were now being measured quite close to the model, 

concerns for three-dimensional efects or uniform atmosphere efects began to arise. Because of the 

varying levels of systems analysis accompanying the low-boom designs begun in 1991, and because 

the impact of sonic-boom reduction techniques on the mission performance was a critical measure 

of success, an attempt was made to conduct a consistent analysis of the mission performance on 

all the designs. Extensive laboratory and feld research on boom signature acceptability by J. D. 

Leatherwood, Kevin P. Shepherd, and Brenda M. Sullivan played a key role in the evolution of the 

target overpressure levels and boom shaping characteristics for low-boom aircraft. 

Early in the HSR Program, Langley retiree Domenic Maglieri had pointed out that real-world 

demonstrations of boom signature modifcations were needed to validate that a benefcial shaped 

boom signature (which had only been accomplished on wind-tunnel models out to about 10 to 

30 body lengths) would persist for large distances in the atmosphere, for example, to 200 or more 

body lengths. Potential approaches to obtaining the necessary data were addressed, including the 

use of nonrecoverable supersonic target drones, missiles, full-scale airplane drones, very large wind 

tunnels, ballistic facilities, whirling-arm techniques, rocket sled tracks, and airplane nose probes. 

Under Maglieri’s leadership, it was found that the relatively large 28-ft supersonic Teledyne-Ryan 

BQM-34E Firebee II drone would be a suitable test vehicle in terms of its adaptability to geometric 

modifcations, operational envelope capabilities, availability, and cost. A program was funded from 

1989 through 1992 that included CFD analyses and wind-tunnel tests on models of the baseline 

Firebee II, including one in which the vehicle forebody was lengthened and reshaped so as to 

provide a “fat-top” sonic boom signature. Before funding was terminated when NASA’s HSR 

Innovation in Flight 55 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Program ended, a fight-test plan was developed that involved measurements read at ground level 

and also in the vehicle near-feld using microphones mounted on a Pioneer uninhabited aerial 

vehicle (UAV). 

Another fight demonstration that was proposed to prove the persistence of a “shaped” boom 

signature from an aircraft fying in a real atmosphere used a modifcation of the SR-71. Initial 

studies suggested that a signifcant amount of airframe modifcations of the baseline airplane 

would be required in order to acquire the desired shaped boom signature. Te SR-71 proposal 

also died due to the subsequent termination of the NASA HSR Program. However, interest in the 

of-body pressures. 

SR-71 as a test article initiated a NASA fight test program to probe an SR-71 in fight to measure 

NASA’s SR-71 and F-16XL during sonic boom research at Dryden in 1995. 

During 1995, a NASA team at Dryden conducted a series of fights in the vicinity of Edwards 

Air Force Base with an SR-71 aircraft to study the characteristics of sonic booms. On each fight, 

two other NASA aircraft took in-fight sonic boom measurements to augment ground-based 

measurements and to aid in the analysis. A NASA YO-3A propeller-driven “quiet” airplane few 

subsonically between the SR-71 and the ground, while a NASA F-16XL few supersonically near 

the SR-71 to measure the sonic boom at distances as close as 85 ft below and to the rear of the 

generating aircraft. Speeds fown by the two aircraft ranged between Mach 1.25 and Mach 1.8 at 

altitudes of about 30,000 ft. Tis successful technique of in-fight probing was to be used later in 

a NASA-DARPA boom-shaping study, as will be discussed. 

56 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

In 1997, Robert L. Calloway and Daniel G. Baize organized an HSR aerodynamic performance 

workshop that included sessions on confguration aerodynamics (transonic and supersonic cruise 

drag prediction and minimization), high-lift, fight controls, and supersonic laminar fow control. 

Single- and multipoint optimized HSCT confgurations, HSCT high-lift system performance 

predictions, and HSCT motion simulator results were presented, along with executive summaries 

for all aerodynamic performance technology areas. Key Langley presenters were Steven X. S. Bauer, 

Richard A. Wahls, Steven E. Krist, Richard L. Campbell, Francis J. Capone, Guy Kemmerly, 

Wendy Lessard, Lewis Owens, and Bryan Campbell. Subsequent workshops were held in 1998 and 

1999 simultaneously with annual reviews of activities in materials and structures, environmental 

impact, fight deck, and technology integration. 

Another critical area of the HSR Program was materials durability. An objective of the activities 

was to demonstrate the ability of candidate materials to withstand mechanical and environmental 

factors that contribute to long-term degradation of properties under conditions simulating HSCT 

fight. Among the objectives was the development of associated predictive and accelerated tests, 

Extensive testing of the High Speed Research Reference H confguration was conducted in 

many Langley tunnels, including the 16-Foot Transonic Tunnel (left) and the National 

Transonic Facility (right). 

methods, and assessment of durability protocols for design. Langley’s Tomas S. Gates led research 

in the area for the Center. Te HSCT was intended to have a design life of 60,000 fight hours. 

At speeds of Mach 2.4, the maximum operating temperature could reach 350 °F under conditions 

of varying oxygen, moisture, solvents, and other environmental stress factors. Materials chosen for 

the vehicle would have to withstand at least one lifetime of this mechanical and environmental 

loading prior to production go-ahead. With the introduction of new materials and material forms, 

not all candidate materials could be subjected to adequate long-term tests; therefore, the necessity 

Innovation in Flight 57 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

of accelerated and predictive methods requires development of validated techniques for screening 

materials for long-term durability. Gates directed eforts at predictive and accelerated test methods 

that use empirical and analytical relationships to simulate long-term durability performance and 

provide the engineer a standard and simple approach to screening new materials for long-term 

durability performance. 

Langley also organized studies of appropriate materials for HSCT applications, including advanced 

aluminums and composite materials. Tomas T. Bales led the eforts on aluminums, and starting 

in 1991, Paul M. Hergenrother led a team in the development of new high temperature composites, 

adhesives, sealants and surface treatments. After sorting through over 200 candidate materials, in 

1995 they arrived at a highly promising candidate known as PETI-5. PETI-5 is the commonly 

used term for phenylethynyl terminated imide oligomers. PETI-5 is a chemical material that can 

be used as both a composite resin and an adhesive. It also combines superb mechanical properties 

and extreme durability with easy processing and environmental stability. Te material met the 

temperature/fight hour targets for the HSCT and was prepared from commercially available 

materials. Curing was done with the application of heat and mild pressure, which resulted in the 

formation of a strong, resistant polymer. Due to the nature of this polymer, it was fairly easy to 

create large, complex parts using PETI-5. Unacceptably high manufacturing cost was one of the 

major barriers to applications of the technology. 

A series of highly successful fabrication demonstrations by Langley raised excitement over the 

material’s potential use in the HSCT; however, developmental testing required for the application 

could not be accomplished within the lifetime of the HSR Program. Nonetheless, the material was 

recognized as a major materials breakthrough and quickly gained interest for other applications. 

PETI-5 won the NASA Commercial Invention of the Year award for 1998, and the material 

received Research and Development Magazine’s R&D 100 award. Trough licensing from 

Langley, companies have positioned themselves for markets in the areas of electronic components, 

jet engines, and high performance automotive applications. 

Langley’s research on improving cruise efciency for HSCT confgurations included wind-tunnel, 

computational, and fight studies of supersonic laminar fow control (SLFC). Eforts with industry 

in the development of SLFC in the HSR Program are discussed in detail in a separate section herein 

on laminar fow control. Tat joint efort by Langley, Dryden, Boeing, McDonnell Douglas and 

Rockwell had resulted in fight evaluations of the state of design theory and the robustness of SLFC 

using an active suction panel gloved to the wing of an F-16XL airplane in fight tests at Dryden. 

Michael C. Fischer was Langley’s manager for the fight experiment. Several technical concerns 

had resulted during the fight tests, including contamination of fows by shocks emanating from 

58 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

the airplane’s canopy and forebody. In addition, the F-16XL was deemed too small for convincing 

proof of the feasibility of SLFC applied to a large supersonic transport, and other potential airplane 

test beds were explored. 

NASA’s F-16XL was modifed with an active suction 

laminar fow glove on its left wing for exploratory 

assessments of supersonic laminar fow control. 

Te Russian Tu-144LL takes of on a research fight sponsored by the NASA High Speed 

Research Program in 1998. 

Innovation in Flight 59 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Several larger airplanes had been considered by NASA for follow-up experiments, including a 

Concorde. Late in 1992, Langley’s Dennis Bushnell had discussed refurbishing one of the surviving 

Russian Tu-144 SSTs for use in supersonic fight research with the aircraft’s manufacturer, 

Tupolev. Following several in-house staf discussions at Langley, Joseph R. Chambers, Chief of 

Langley’s Flight Applications Division (sponsoring organization for the SLFC HSR efort), sent a 

formal proposal to NASA Headquarters (with the approval of Roy V. Harris, Langley’s Director 

for Aeronautics) for using a Tu-144 for SLFC fight experiments. Meanwhile, Headquarters had 

independently funded a study contract to Rockwell to conduct a feasibility assessment of restoring 

a Tu-144 for use in the HSR program. Informal discussions between Headquarters and Tupolev 

had taken place at the Paris Air Show with positive results. Te proposal met with approval at 

Headquarters, and a cooperative Tu-144 project was enabled by an agreement signed in June 1994 

in Vancouver, Canada, by Vice President Albert A. Gore and Russian Prime Minister Viktor 

Chernomyrdin. Tis was the most signifcant post-Cold War joint aeronautics program to date 

between the two countries. Unfortunately, the original Langley interest in SLFC research on the 

Tu-144 was not accommodated within the ensuing activities. 

A Tu-144 was modifed by the Tupolev Aircraft Design Bureau in 1995 and 1996. Te newly 

designated Tu-144LL Flying Laboratory performed fight experiments as part of NASA’s 

HSR Program for studies of high temperature materials and structures, acoustics, supersonic 

aerodynamics, and supersonic propulsion. Te Tu-144LL rolled out of its hangar on March 17, 

1996, to begin a 6-month, 32-fight test program. Six fight and two ground experiments were 

conducted during the program’s frst fight phase, which began in June 1996 and concluded 

in February 1998 after 19 research fights. A shorter follow-up program involving seven fights 

began in September 1998 and concluded in April 1999. All fights were conducted in Russia from 

Tupolev’s facility at the Zhukovsky Air Development Center near Moscow. Langley’s Robert A. 

Rivers and Dryden’s C. Gordon Fullerton became the frst American pilots to fy the modifed Tu144LL during the 1998 experiments. during their evaluations, Rivers and Fullerton were primarily 

concerned with the Tu-144LL’s handling qualities at a variety of subsonic and supersonic speeds 

and fight altitudes. 

Te HSR fight deck studies at Langley contributed enabling eforts in synthetic vision that might 

eliminate the need for the heavy drooped nose concept used on the frst generation SSTs. Te very 

signifcant accomplishments of this program are presented in another section of this document. 

Under the management of Daniel G. Baize, the synthetic vision program accelerated following the 

demise of the HSR Program as the technology was widely appreciated for its potential use for all 

types of aircraft. Te work area became part of the new NASA Aviation Safety Program following 

the end of the HSR activities. Te technology ultimately transitioned into a broader applications 

60 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

arena for the subsonic commercial airplane feet, including aggressive applications by the business 

airplane community. Tis area is also covered in detail in a separate section herein. 

Langley’s HSR activities also included participation in eforts to resolve issues regarding the impact 

of emissions from commercial aircraft. A NASA Atmospheric Efects of Aviation Project (AEAP) 

was organized to develop scientifc bases for assessing atmospheric impacts of the exhaust emissions 

discharged during cruise operations by feets of subsonic and supersonic civil aircraft. Te AEAP 

comprised two major entities, a Subsonic Assessment (SASS) project and an Atmospheric Efects of 

Supersonic Aircraft (AESA) project. Te SASS project was conducted under the auspices of NASA’s 

Advanced Subsonic Technology Program (ASTP), and the AESA project was conducted under the 

HSR Program. Because of the shared focus on environmental impact, program management of 

the two assessment eforts was consolidated into an overall program, the AEAP. Te AESA project 

was designed to assess the impacts of a potential future feet of HSCTs with cruise operations at 

midstratospheric altitudes. 

HSR activities also focused on yet another environmental issue: the efects of radiation exposure 

to aircrew and passengers of an HSCT. Te National Council on Radiation Protection and 

Measurement (NCRP) and the National Academy of Science (NAS) had concluded that the 

data and models associated with the high-altitude radiation environment needed refnement and 

validation. In response, NASA and the Department of Energy Environmental Measurements 

Laboratory (EML) created the Atmospheric Ionizing Radiation (AIR) project under the auspices 

of the HSR Program. In AIR, international investigators were solicited to contribute instruments 

to fy on an ER-2 aircraft at altitudes similar to those proposed for the HSCT. Te fight series 

took place at solar minimum (radiation maximum) with northern, southern, and east/west fights. 

Te investigators analyzed their data and presented preliminary results at an AIR workshop in 

March 1998. 

Termination of the High-Speed Research Program 

In the late 1990s, Boeing assessed its seriousness in future commitments to pursuing the HSCT. 

Te development cost of this relatively high-risk airplane was estimated to be over $13 billion. Key 

technologies had not advanced to an acceptable level, especially in the areas of propulsion, noise, 

and fuel tank sealants. Tese technical shortcomings, together with production problems with 

its existing line of subsonic transports, major commitments to its new B777 transport, and other 

considerations led to a Boeing perspective that refected critical technical obstacles that required 

solutions confrmed by full-scale component demonstrations and continuing study regarding the 

marketability and economics of supersonic aircraft. 

Innovation in Flight 61 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Te HSR Program was dependent on an active partnership between the government and industry. 

NASA terminated HSR in 1999 after Boeing dramatically reduced support for the project, 

shrinking its staf devoted to HSR from 300 to 50 and pushing the operational date for a highspeed supersonic transport from 2010 to at least 2020. Boeing’s action was the result of market 

analysis and technology requirement assessments indicating that, from an economically and 

environmentally sound perspective, the introduction of a commercial HSCT could not reasonably 

occur prior to the year 2020. Industry and NASA also questioned whether the technologies being 

pursued would appropriately address environmental standards and other challenges in 2020. 

In response, NASA reduced activity in the HSR Program to a level commensurate with 

industry interest. 

NASA terminated the program in 1999 in order to add $600 million to the budget for the 

International Space Station (ISS). Te extra money was needed as part of a $2 billion, 5-year 

commitment to back up Russian delays on the ISS. Daniel S. Goldin, NASA Administrator, speaking 

to the House’s Subcommittee on Space and Aeronautics on February 24, 1999, summarized the 

termination of the HSR activity: 

“We are proud of our past accomplishments in two focused programs, High Speed Research and 

Advanced Subsonic Technology. Although dramatic advances were made against the original HSR 

Program goals, our industry partners indicated that product development would be signifcantly 

delayed, which led to the decision to terminate this program at the end of 1999.” 

Post–High-Speed Research Activities 

Following the NASA HSR Program termination in 1999, the subsequent retirement of the Concorde 

feet, rising fuel prices, and the demise of a large number of commercial airlines, worldwide interest 

in large commercial supersonic transports plummeted to new lows. Langley’s research activities 

in supersonic civil aircraft were severely reduced in scope and funding, and the remaining funds 

and researchers were reoriented toward more fundamental research on a few critical technologies, 

with a limited focus on notional vehicles, such as supersonic business jets, and demonstrations 

of selected technologies, such as sonic boom shaping. Meanwhile, industry expertise and design 

teams from the previous supersonic transport programs were disbanded and reassigned to other 

programs, leaving a wide void nationally in experienced supersonic civil airplane capability. 

In 2004, the NASA Headquarters Aeronautics Research Mission Directorate sponsored a Vehicle 

Systems Program (VSP) on notional advanced aeronautical vehicles, including studies of associated 

technology goals and development roadmaps to help focus NASA research eforts in civil aircraft. 

62 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Te research community is developing new interest in supersonic business jets. 

As part of its VSP responsibilities, Langley participated in vehicle-specifc studies to identify 

breakthrough capabilities and resolve barrier issues for subsonic and supersonic civil vehicles. 

Coordinated by Langley’s Peter G. Cohen, the supersonic segment of the program included 

three major thrusts: fundamental research in propulsion, aerodynamics, emissions, and noise; 

participation in cooperative programs with the military and industry; and participation in advocacy 

planning for new initiatives in supersonics. At Langley, specifc tasks included aerodynamic design 

optimization, sonic boom, low-boom confgurations, systems studies, and aeroelastic phenomena. 

In addition to Langley activities, the research program supported research eforts at the Glenn and 

Dryden Centers, as well as cooperative investigations with industry partners. 

Notional supersonic civil aircraft studies in the VSP efort included business jet and large commercial 

transport applications. Compared with Concorde state-of-the-art characteristics—Mach 2.0, 

400,000 lbs, 100 passengers, overwater cruise—Langley investigated a near-term (5 to 10 years) 

supersonic business jet—designed for Mach 1.6 to 2.0, 100,000 lbs, 6 to 10 passengers, and 

overland cruise—known as the Silent Small Supersonic Transport. Te studies also included a farterm (15 years), second-generation transport (Mach 0.95-2.0, 400,000 lbs, 150 to 200 passengers, 

“corridor fight path”). Te Langley VSP sponsored basic research in a number of areas, including 

advanced supersonic design methods and assessments of unconventional supersonic transport 

confgurations, such as multiple-body designs. 

Sonic Boom Shaping 

One key technology target addressed by the VSP Program is the eternal sonic boom issue. Widely 

accepted as the single largest barrier to economically feasible supersonic civil fight operations, 

the boom continues to receive research focus. Perhaps no other aspect of supersonic fight has 

created such a polarization of attitudes regarding the possibility of solutions. Many within the 

Innovation in Flight 63 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

aviation community regard the boom as a fact of life— generated by fundamental laws of physics 

unyielding to modifcation. However, Langley’s past research on methodology to modify sonic 

boom signatures and make them more acceptable is providing optimism and guidance to today’s 

eforts. Te extensive results of computational analysis, wind-tunnel tests, fight tests, and human 

response evaluations have resulted in a relatively mature understanding of key sonic boom physical 

characteristics and the objectionable nature of certain critical boom phenomena. 

While it is universally agreed that lifting the ban on commercial supersonic overland fight would 

represent a signifcant breakthrough in aviation history, the technology to do so has not yet been 

demonstrated. Mitigation of the sonic boom via specialized shaping techniques was theorized 

nearly four decades ago; but, until recently, this theory had never been tested with a fight vehicle 

subjected to actual fight conditions in a real atmosphere. 

A major fnding of sonic boom research from the 1960s is that noise reductions in the boom 

signature could potentially be achieved by the use of boom shaping. In particular, if the 

classical sharp-edged “N” waveform could be modifed so that the onset of the initial shock 

was systematically reduced and shaped (lower initial pressure increase, resulting in a longer rise 

time and a less abrupt change in pressure), the booms might be less objectionable, as confrmed 

by Langley research using human test subjects experiencing sonic booms in a high-fdelity 

simulation facility. 

Te overpressure level of sonic boom that would be acceptable to the general population has been 

investigated in ground-based simulation as well as actual supersonic overfights of populated areas. 

Based on these results and studies of community response to other high-level impulsive sounds 

(artillery, explosions, etc.), criteria were developed for acceptability of sonic booms. Analysis has 

indicated that overpressure levels for a representative large HSCT-type supersonic transport would 

be about 3 lb/ft2

, and that signifcant reductions would be necessary to achieve acceptance by the 

bulk of the population (the smaller Concorde generated an unacceptable level of 2 lb/ft2

). 

Te aerospace community has, of course, been aware that sonic boom overpressures are directly 

relatable to size, weight, and length of the vehicle under consideration, and that smaller aircraft, 

such as business jets, could have a lower level of sonic boom than large transports. In addition, the 

Langley results discussed earlier in other supersonic transport programs had indicated that shaping 

of the boom signature might be accomplished through aircraft geometric shaping. In particular, 

wind-tunnel and computational results showed that features—such as placement of engine nacelles, 

wing planform shape and lift distribution, and fuselage forebody geometry—could modify boom 

characteristics in a favorable matter. 

64 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

Stimulated by the possibility that sonic boom minimization might be achievable for supersonic 

business jets, thereby permitting overland supersonic cruise with its favorable economics, industry 

has continued its interest in the design methodology for this application, but the lack of full-scale 

fight data to validate approaches to boom minimization has continued to block applications. 

After NASA’s termination of the HSR efort, essentially all activity on sonic boom minimization 

ceased with the exception of small Langley contracts with industry. In 1999, a small cooperative 

research program was conducted with Lockheed to study the feasibility of a supersonic business 

jet. Both Langley and the Ames Research Center conducted design and testing in this efort. In 

2003 a contract was awarded to Raytheon to study the feasibility and technology requirements for 

supersonic business jets. 

In 2000, the Defense Advanced Research Projects Agency (DARPA) initiated a Quiet Supersonic 

Platform (QSP) Program directed toward the development and validation of critical technology for 

long-range advanced supersonic aircraft with substantially reduced sonic boom, reduced takeof and 

landing noise, and increased efciency relative to current technology supersonic aircraft. Improved 

capabilities would include supersonic fight over land without adverse sonic boom consequences, 

with an initial boom overpressure rise less than 0.3 lb/ft2

, unrefueled range approaching 6,000 nmi, 

and lower overall operational cost. Advanced airframe technologies would be explored to minimize 

sonic boom and vehicle drag, including natural laminar fow, aerodynamic minimization (aircraft 

shaping), exotic concepts (plasma, heat and particle injection), and low weight structures. 

DARPA’s Program Manager for QSP was Richard W. Wlezien, a Langley researcher on assignment 

to DARPA. In formulating the advocacy and content of his program, Wlezien had received major 

briefngs on the state of low-boom research by Peter Coen, William P. Gilbert, and Langley retirees 

Domenic J. Maglieri and Percy J. (Bud) Bobbitt. Tese briefngs played a major infuence on 

DARPA’s management in the fnal program approval. 

Northrop Grumman, Boeing, and Lockheed Martin all performed phase I design studies for 

DARPA. In phase II, DARPA focused on military variants and attached particular signifcance to 

a fight demonstration of boom shaping and validation of propagation theories in real atmospheric 

conditions as had been advocated by Maglieri. DARPA subsequently initiated a Shaped Sonic 

Boom Demonstration (SSBD) Program with Northrop Grumman Corporation, including 

major participation from NASA Langley and Dryden, Naval Air Systems Command, Lockheed 

Martin, General Electric, Boeing, Gulfstream, Wyle Laboratories, and Eagle Aeronautics. Eagle 

Aeronautics’ participation was particularly valuable to the team. Maglieri and Bobbitt represented 

Eagle, bringing with them decades of valuable experience and expertise in the areas of sonic boom 

Innovation in Flight 65 
real fight conditions. For the demonstration, Northrop Grumman modifed an F-5E fghter 

aircraft that was provided by the U.S. Navy’s Naval Air Systems Command. Te company designed 

and installed a specially shaped “nose glove” substructure and a composite skin to the underside of 

fuselage. Te fnal nose shape designed by Northrop Grumman met boom, pilot vision, 

drag, trim drag, and stability and control requirements. 

SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

and applied aerodynamics. Maglieri’s leadership and creativity in sonic boom technology played a 

key role in the formulation and approach used in the program; while Bobbitt’s extensive knowledge 

of applied aerodynamics provided guidance in aerodynamic integration and wind-tunnel testing. 

Te SSBD project was yet another example of close working relationships between NASA research 

centers. In addition to wind-tunnel tests conducted by the Glenn Research Center, the efort 

included valuable contributions by Dryden personnel in the planning and conduct of the fight 

experiment. Dryden’s Edward A. Haering, Jr. was a critical participant in the project working 

with Peter Coen and others to create valid and successful sonic boom experiments. Haering also 

conceived, designed, and led an inlet shock spillage measurement test that was used to calibrate 

Northrop Grumman CFD methods for the design of the SSBD. 

Te objective of the SSBD Program was to demonstrate the validity of sonic-boom shaping theory 

in 

the wave 

Te F-5 shaped-boom demonstrator aircraft. 

Aircraft used in the shaped-boom tests. From top: the NASA F-15B survey 

airplane, the F-5 shaped-boom demonstrator, and the baseline F-5E. 

66 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

On August 27, 2003, the frst ever in-fight demonstration of boom shaping occurred at Dryden. 

During the experiment, the modifed F-5E aircraft few through a test range at supersonic speeds. 

Dryden sensors and industry sensors on the ground and in a Dryden F-15B research plane 

measured the shape and magnitude of the sonic boom’s atmospheric characteristics. During some 

of the demonstrations, a NASA F-15B few behind the modifed F-5E in order to measure that 

First proof that the sonic boom signature can be altered in actual fight conditions. Te signature of the shaped 

sonic boom demonstrator clearly shows a benefcial softening of the bow shock signature compared with the 

baseline F-5E. 

aircraft’s near-feld shockwave patterns. Te F-15B’s specially instrumented nose boom recorded 

static pressure measurements while fying behind and below the modifed F-5E at a speed of about 

Mach 1.4. As previously discussed, this innovative in-fight data gathering technique had been 

developed by Dryden in 1995, when a Dryden F-16XL aircraft probed the shockwave patterns of 

a SR-71 research aircraft. 

On three other fights, the modifed F-5E SSBD was followed about 45 seconds later by an 

unmodifed F-5E to determine the efect of aircraft shaping on sonic booms. Te ground-based 

and airborne instruments measured the world’s frst shaped (fat top) sonic boom, followed by the 

normal, unshaped (N-wave) sonic boom from the unmodifed F-5E. Te data comparison of the 

two aircraft signatures clearly showed the persistence of the shaped boom, which was the highest 

priority of the study. A reduction in the sonic boom intensity was an attendant beneft. Another 

Innovation in Flight 67 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

signifcant result was a demonstration of the robust nature of the intensity reduction. An identical 

test performed later that day confrmed the original results. 

Te results of this remarkable fight project have made history as the frst demonstration of the 

persistence of a shaped sonic boom waveform. Te impact of the demonstration has proven 

numerous critics of the technology wrong and has instilled considerable excitement in the research 

community over the potential tailoring of sonic boom characteristics. Te extensive data that 

have been gathered over a total of 26 fights for shaped-boom features will be used extensively 

for correlation and calibration of computational codes for boom predictions and will be used for 

future developments of supersonic cruise vehicles. Finally, the project has served as an illustration 

of the highly successful leveraging of national resources for an aggressive research attack on a 

very difcult aeronautical phenomenon. Follow-up activities include the use of higher order CFD 

methods for the integration of low-boom confgurations, including the difcult job of engine inlet 

integration and drag minimization. 

Status and Outlook 

Te evolution of supersonic cruise technology applicable to civil vehicles has progressed rapidly 

from the fundamental eforts of Langley, whether functioning as a member of NACA, NASA, or 

an industry team. Virtually every critical discipline has experienced revolutionary advances in the 

state of the art, and some areas, such as supersonic aerodynamic design methods, have reached 

a remarkable level of maturity. Focused eforts of the U.S. SST Program, and the Langley-led 

SCR and HSR Programs, have accelerated technology development in highly relevant national 

eforts. Although tremendous progress has been made toward providing the technology required 

for economically feasible and environmentally compatible civil supersonic aircraft, several major 

barriers—both technical and nontechnical—still limit the introduction of this class of vehicle. 

Te sonic boom issue remains a most formidable challenge to supersonic overland fight, along with 

airport noise and reaching closure for a supersonic transport airplane with acceptable economic 

return. Skyrocketing fuel costs, increased bankruptcy by major airlines, low-fare competition 

from very efcient advanced subsonic transports, and emerging alternatives to business travel also 

stand in the way of progress. Finally, the high risk and astounding development costs associated 

with developing and certifying such a revolutionary airplane in today’s climate of economic 

uncertainty and environmental sensitivity closes the door for further developments. In view of these 

considerations, large supersonic transport aircraft are far removed from the aerospace community’s 

venue for near-term commercial applications. 

68 Innovation in Flight 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

In early 2000, NASA requested the Aeronautics and Space Engineering Board (ASEB) of the 

National Research Council to conduct an 18-month study to identify breakthrough technologies 

for overcoming key barriers to the development of an environmentally acceptable and economically 

viable commercial supersonic aircraft. Te ASEB responded with a Committee on Breakthrough 

Technology for Commercial Supersonic Aircraft, composed of ex-NASA, industry, DoD, and 

academic experts in virtually every critical discipline involved in supersonic cruise vehicles, many 

of which had participated in past supersonic transport eforts. Te committee’s job was made more 

difcult by the fact that breakthrough technologies were guarded as proprietary and competitionsensitive for most of the HSR Program’s results. 

Te committee members concluded that an economically viable supersonic aircraft will require 

new focused eforts in several areas, as well as continued development of technology on a broad 

front. Furthermore, NASA must advance key technologies to a readiness level high enough to 

facilitate the handof of research results to the aerospace industry for commercial development. Te 

committee concluded that maturation of key technologies could enable operational deployment 

in 25 years or less of an environmentally acceptable, economically viable commercial supersonic 

aircraft with a cruise speed of less than approximately Mach 2. Tey concluded that the time 

required for deployment could be considerably less if an aggressive technology development 

program were focused on smaller supersonic aircraft. Te committee’s rationale was that goals in 

many critical areas would be easier to achieve with smaller aircraft; however, it will certainly take 

much longer to overcome the more difcult technological and environmental challenges associated 

with building a large commercial supersonic aircraft with a cruise speed in excess of Mach 2. 

Despite the challenges, a glimmer of hope exists in the business aircraft sector where a continuation 

of interest and sporadic projects continue to fourish for potential supersonic business jets (SBJ). 

SBJ aircraft have been discussed since the days of the NASA SCR Program, and several aborted 

industry programs arose in the 1980s, including a collaboration between Gulfstream and Sukhoi. 

Now, new SBJ eforts are appearing in the United States and abroad. Tese upstart activities reason 

that the smaller SBJ will present a lower technology challenge in the areas of sonic boom and 

airport noise requirements, and several proposed new SBJ projects have surfaced for a foothold in 

what might become a revolutionary sector of aeronautics. Also, the economic factors for the SBJ 

market may not be as critical as those for large transports, since a smaller number of high income 

individuals, companies, and even governments would be willing to pay the price for a business 

time advantage. 

In October 2004, at the National Business Aircraft Association (NBAA) convention, Aerion 

Corporation and Supersonic Aerospace International (SAI) announced plans to launch full-scale 

Innovation in Flight 69 
SUPERSONIC CIVIL AIRCRAFT: THE NEED FOR SPEED 

development of supersonic business jets. Aerion’s design makes use of an unswept, sharp leadingedge wing, a T-tail, and a novel natural laminar fow wing. SAI teamed with Lockheed Martin’s 

Skunk Works, with its design incorporating low sonic boom (overpressures of less than 0.3 lb/ft2

) 

design features, such as an inverted tail and careful integration of the fuselage, wing, and engine 

components, with an arrow wing. Both teams are investigating aircraft with a stand-up cabin, a 

range of 4,000 nmi (one-stop transpacifc and nonstop United States to Europe) at a cruise speed 

of Mach 1.6 to 1.8. 

In 2005 NASA refocused its Vehicle Systems Program for aeronautics as the Agency directed its 

priorities on a new Vision for Space Exploration approved by President George W. Bush. Te revised 

VSP places priority on four fight demonstrations of breakthrough aeronautical technologies, with 

one of the fight projects directed to the mitigation of sonic boom phenomena. Te NASA Sonic 

Boom Mitigation Demonstration Project is managed by the Dryden Flight Research Center. In 

addition to NASA Intercenter participation and eforts, industry teams have been tasked to defne 

technology and design requirements in preparation for a request for proposals for a low-sonicboom demonstration aircraft. During a fve-month study, the team’s research will determine the 

feasibility of modifying an existing aircraft or whether a new design will be required as the quiet 

boom demonstrator. 

NASA awarded a grant to American Technology Alliances (AmTech) to fund the industry studies 

which are being conducted by four industry teams. Te teams include individual eforts by Boeing 

Phantom Works and Raytheon Aircraft, while Northrop Grumman has teamed with Gulfstream 

Aerospace and Lockheed Martin has teamed with Cessna Aircraft Company. Te same grant also 

funded Allison Advanced Development Company, GE Transportation, and Pratt and Whitney to 

support the teams with engine-related data. 

In summary, past contributions and leadership of NASA Langley Research Center in supersonic 

cruise technology have led the way toward potential application to civil aircraft. Much of the 

technology intended for supersonic aircraft has already been applied to existing and emerging 

subsonic aircraft. Together with its industry partners, the Center has provided disciplinary design 

methodology, concepts, and integrated assessments that have raised technology to relatively 

high levels of maturity. It remains to be seen if the existing technical hurdles, economic factors, 

and environmental obstacles can be removed for future applications to the civil aircraft 

transportation system. 

70 Innovation in Flight 
The Blended Wing Body: Changing the Paradigm 

Concept and Benefts 

One highly motivating factor in innovative research for aeronautics is a desire to achieve the most 

efcient aircraft confguration for specifc missions. For a high-performance military fghter, this 

challenge entails providing extreme maneuverability, low-observable radar signature, and sustained 

cruise performance. To a large extent in the highly competitive world of commercial air transports, 

efciencies and economic considerations govern the introduction of innovative designs that change 

the standard paradigm. 

Te history of aircraft design evolution since the frst powered controlled fight by the Wright 

brothers depicts an interesting perspective on an emerging focus toward the most efcient layout 

for airplane confgurations. In the years following the revolutionary events of 1903, an amazing 

injection of innovative confgurations occurred involving the evolution from biplanes to monoplanes, 

propellers to turbojets, and open cockpits to pressurized passenger cabins. Technical contributions 

rapidly accelerated within the key technical disciplines of aerodynamics, structures and materials, 

fight systems, and propulsion, which led to the development and frst fight of the swept-wing 

Boeing B-47 exactly 44 years later on December 17, 1947. In contrast to earlier airplanes, the B-47 

confguration included unconventional external features, such as a swept wing and empennage as 

well as podded turbojet engines mounted to pylons beneath and forward of the wing. 

Progress in the mission capabilities of civil and military aircraft has, of course, improved 

signifcantly since the days of the B-47. Te continuous application of new technologies—such as 

Aircraft evolution. 

Innovation in Flight 71 
THE BLENDED WING BODY: CHANGING THE PARADIGM 

Artist’s concept of a blended wing body commercial transport. 

supercritical wings, advanced structures and materials, and high-bypass turbofans—has permitted 

the introduction of wide-body transports and extended-range missions. However, a cursory 

examination of the external features of current-day subsonic commercial transports indicates 

confguration features not unlike those used by the B-47 over 57 years ago. Te historical attraction 

to the “tube and wing” arrangement has involved numerous firtations with novel, unorthodox 

aircraft confgurations, but the results of experimentation and experiences with prototype aircraft 

have usually led back to the paradigm set by the B-47. Nonetheless, leading-edge researchers and 

innovators continue to pursue the challenge to conceive unconventional confgurations that might 

exhibit signifcant benefts and capabilities due to continued improvements and breakthroughs in 

aerodynamic, propulsive, and structural technologies. 

Te blended wing body (BWB) is a radical new concept for potential use as a future commercial 

passenger transport or as a military transport for troop deployments, cargo delivery, or air-to-air 

refueling missions. Te airplane concept is a thick hybrid fying wing that, in commercial transport 

versions, could carry up to 800 passengers (almost twice the capacity of a Boeing 747-400) more 

than 7,000 miles in a double-deck centerbody that blends into the outer wings. By integrating 

engines, wing, and body into a single lifting surface, designers have maximized overall aerodynamic 

efciency. Te BWB confguration allows the entire aircraft to generate lift with minimal drag, 

provide signifcantly improved fuel economy with reductions in undesirable emissions, and 

72 Innovation in Flight 
THE BLENDED WING BODY: CHANGING THE PARADIGM 

potentially lower passenger-seat-mile costs, especially for large transports. In addition, the unique 

engine placement provides further operational benefts, such as reduced community noise during 

takeof and landing operations. 

Flying-wing aircraft confgurations are not new, having been introduced and evaluated as early as 

the 1930s and 1940s within the United States and abroad. Today, the highly successful military 

B-2 bomber provides an example of a change in the paradigm, necessitated in its case by the 

need for low observables and international range. Like the B-2, the BWB incorporates advanced 

structural materials and fight control technologies to ensure safe and efcient operations across 

the fight envelope. Engineering analyses conducted to date by industry and NASA indicate that 

an advanced aircraft of this type could weigh less, generate less noise and fewer omissions, and 

operate at less cost than a conventional transport confguration using similar levels of technologies. 

Te unprecedented levels of internal volume provided by the confguration ofers revolutionary 

capabilities, such as passenger sleeper berths for transpacifc fights and large weapon or troop loads 

for the military. 

Challenges and Barriers 

Te unconventional confguration of the BWB design results in signifcant challenges and potential 

barriers in the technical disciplines, operational and regulatory requirements, and economic 

strategies for industry and commercial airlines. 

Disciplinary Challenges 

Te concept of carrying as many as 800 passengers within a BWB confguration requires extensive 

research and development in the areas of aerodynamics, stability and control, structures and 

materials, and propulsion integration. 

Aerodynamic design challenges for the BWB are present in all phases of fight operations: from 

takeof, through cruise, and to landing. Many of these aerodynamic issues have proven difcult 

or impossible to solve for fying-wing type aircraft of the past. For example, the absence of a 

conventional aft-fuselage-mounted horizontal tail results in the need to defect the wing trailing 

edge upward to provide trim for the nose-up attitudes required to produce lift for takeof and 

landing. Tis trailing-edge defection degrades the wing’s lift potential and has resulted in 

unacceptable lift penalties for many past fying-wing aircraft. At high-subsonic cruise speeds, a 

particularly challenging requirement for the BWB is to ensure an acceptable level of aerodynamic 

drag for the large, thick wing centerbody. 

Innovation in Flight 73 
THE BLENDED WING BODY: CHANGING THE PARADIGM 

Schematic of Blended Wing Body passenger cabin showing side view 

(upper sketch) and front view (lower sketch) of layout. 

Stability and control problems have proven to be some of the most formidable barriers for past fyingwing aircraft confgurations. Te lack of a conventional aft tail results in potential longitudinal and 

directional stability and control defciencies. Without a tail, aerodynamic stability variations with 

increasing angle of attack must be carefully assessed and designed to ensure that uncontrollable 

phenomena, such as “pitch up” or “tumbling,” will not occur. Also, the absence of a conventional 

vertical tail results in directional stability and control requirements that require the use of wingtipmounted fn or rudder confgurations, as well as symmetric defections of split upper and lower 

outer-wing trailing-edge segments for yaw control. Te highly successful application of advanced 

digital fight controls and envelope limiting concepts to aircraft such as the B-2 has demonstrated 

that proper anticipation and design can meet these challenges. 

Another daunting challenge to the successful design of BWB confgurations involves the integration 

of engine and engine pylon concepts on the upper-aft surface of the blended fuselage centerbody. 

Shock-induced infow conditions can severely degrade the operational efciencies of large bypass 

ratio turbofans in proximity to uppersurface fows, and the engine installations can, in turn, 

lead to highly undesirable interference efects for the wing-body components and trailing-edge 

control surfaces. 

Finally, of all the disciplinary design challenges facing the BWB concept, perhaps none is as important 

as the design of a highly noncircular pressurized cabin. Te structural weight advantage of circular 

fuselage shapes for airplanes has been exploited since the earliest days of pressurized structures, 

74 Innovation in Flight 
THE BLENDED WING BODY: CHANGING THE PARADIGM 

and the experience base, design and evaluation methodology, and regulatory requirements are well 

known within the aviation community. In contrast, very little experience has been accumulated 

with noncircular pressurized structures and the integration of passenger and payload structural 

accommodations will require careful consideration if the advantages of span loading are not to 

be lost in an inefcient and unacceptably heavy structure. Possible solutions to these formidable 

requirements might be provided by current and near-term advanced composite materials and 

innovative approaches to structural design. 

Operational Challenges 

To date, studies of the BWB confguration concept’s advantages, when compared with a conventional 

airplane, indicate that the concept becomes especially superior for very large (450 to 800 passenger) 

aircraft designs. Tus, in addition to operational challenges related to its unique confguration, the 

BWB is challenged by considerations of the safe and efcient accommodation of large numbers of 

passengers and payload. 

Planform view of an 800-passenger Blended Wing Body compared with an Airbus A380 

(orange) and a Boeing B747-400 (green). 

Innovation in Flight 75 
THE BLENDED WING BODY: CHANGING THE PARADIGM 

From a passenger’s perspective, a unique characteristic of the BWB confguration is the provision of 

passenger volume within the centerbody structure. Versions of the BWB envision upper and lower 

seat accommodations in multiple side-by-side seating bays (150 in. wide) similar to Boeing 737 

and 757 arrangements. Te lack of windows for orientation and interest must be countered with 

the provision of appropriate systems for passenger comfort and relief of anxieties. Because some 

passengers will be distributed in a spanwise direction rather than the conventional arrangement 

near the center line of the airplane, the infuence of rolling motions on passenger comfort 

during turbulence or intentional maneuvers must be resolved and satisfactory ride qualities must 

be ensured. 

Provision for timely enplanement and deplaning procedures as well as emergency egress of such 

large numbers of passengers must be anticipated and provided within the airplane’s structural 

layout and passageways. 

Operational considerations, such as the dimensions of its wheel track and its operational weight 

for runway and taxiway operations will impose constraints on the span and length of the BWB 

(and other conventional “super jumbo” aircraft). Te challenge of processing such large numbers 

of passengers will also need to be met by the airports. 

Economic Challenges 

Te bottom-line answer that determines whether unconventional aircraft become feasible and 

procured by commercial airlines is economic payof. Despite the inherent appeal of an aircraft 

confguration due to novelty, airlines will not acquire transports that are not proftable and 

competitive, passengers will not procure tickets that are not competitively priced or ride in 

airplanes with poor ride qualities, and industry will not design and build unconventional designs 

that expose signifcant new problems or certifcation issues requiring large expenditures of funds 

and market time to solve. 

Te foregoing problem areas and issues are well known to those interested in BWB designs, and 

the research and development required to mature the BWB concept has been evolving and making 

progress for over a decade. Although studies to date indicate this revolutionary confguration might 

contribute signifcant benefts, the BWB will require continued eforts to bring it to a sufcient 

level of technical maturity before it can begin to challenge the entrenched paradigm. 

76 Innovation in Flight 
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Langley Activities 

Initial Activities 

Dennis M. Bushnell, Senior Scientist of NASA Langley Research Center, is internationally 

recognized as one of the most credible and brilliant free-thinking innovators in the aerospace 

community. Troughout his career, Bushnell has personally challenged and encouraged researchers 

to embark on studies of fresh ideas and revolutionary approaches to age-old problems and barriers. 

Te genesis of Langley’s activities on the BWB concept began with a series of invitational workshops 

planned and conducted by Bushnell during the 1980s to stimulate aeronautical innovators across 

the Nation toward a vision of the unthinkable, the undoable, and the revolutionary. In 1988, he 

addressed a gathering of innovative leaders within the aeronautical community at Langley with this 

question: “Is there a renaissance for the long-haul transport?” Bushnell’s question was stimulated 

by his perspective that advances in the aerodynamic performance of commercial transports had 

declined from revolutionary leaps to evolutionary gains wherein incremental benefts were becoming 

smaller and smaller. In particular, metrics such as airplane L/D ratio for subsonic transports had 

not increased signifcantly in modern times. 

Bushnell encouraged the community to explore novel approaches for aircraft designs that might 

provide a breakthrough in what was rapidly becoming a stagnant area with diminishing advances. 

He especially suggested that unorthodox aircraft confgurations deviating from the normal tube 

with wings might provide breakthrough performance if solutions to potential problems could be 

achieved within the technical disciplines. 

One of the individuals accepting Bushnell’s challenge in 1988 was Robert H. Liebeck of the Long 

Beach, California, division of the McDonnell Douglas Corporation (now Te Boeing Company). 

Stimulated by his discussions with Bushnell, Liebeck and his associates conducted a “clean piece 

of paper” brief study and arrived at a revolutionary confguration that used adjacent pressurized 

passenger tubes aligned in a lateral plane and joined with a wing in an arrangement that vaguely 

resembled a tadpole. Comparisons made by the McDonnell Douglas team with a conventional 

confguration airplane, sized for the same design mission, indicated that the blended confguration 

was signifcantly lighter, had a higher L/D ratio, and had a substantially lower fuel burn. Tis frst 

rudimentary design was the embryonic beginning of the BWB confguration. 

Liebeck and his team held briefngs that inspired immediate excitement and interest from the 

Langley researchers based on the performance potential and the clear technical disciplinary 

challenges that would have to be addressed by researchers in Langley’s areas of expertise. Special 

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First Blended Wing Body confguration conceived by McDonnell Douglas team. 

interest was especially exhibited by a Langley group responsible for the systems analysis of advanced 

aircraft confgurations. Tis group specialized in assessing the ability of advanced confgurations to 

meet specifed mission requirements within current and future technology capabilities. William J. 

Small, Head of Langley’s Mission Analysis Branch, sponsored a small study contract in April 1993 

to allow Liebeck and his associates to further refne the confguration and compare its capabilities 

with those of a conventional subsonic transport confguration having similar advanced technologies 

(such as composite structures and advanced technology turbofans). 

In this study, Liebeck and his associates made a critical decision when they decided that the 

unconventional transport would not use conventional tubular passenger compartments and that 

an advanced structural approach would permit more fexibility in designing the fuselage shape. 

With the assumption that the structures issue could be solved, the team moved forward into an 

78 Innovation in Flight 
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assessment of various blended fuselage shapes that might result in an integrated wing-fuselage 

with minimal exposed (wetted) area design for minimum aerodynamic drag. Te refned design 

incorporated an advanced supercritical wing, winglets with rudders for directional control, and 

“mailbox slot” engine intakes designed to swallow the boundary layer fow from the wing upper 

surface for enhanced performance. A double-deck pressurized passenger structure was designed, 

and all aspects of this unique confguration began to be addressed. Future development of BWB 

designs would begin to undertake issues not addressed by this initial concept, but the basic character 

of this frst generation confguration persists to this day. 

System Studies 

Interactions between McDonnell Douglas and Langley on BWB-type confgurations intensifed in 

the middle 1990s. Langley was particularly interested in new confgurations for very large subsonic 

transports (VLSTs) that might ofer signifcant reductions in cost per passenger mile, and the BWB 

seemed to be a very promising approach. Langley’s interest was stimulated by the state of air travel 

and projections of its growth in the future. Worldwide air travel passenger demand, measured in 

revenue passenger miles, was expected to triple within the next 15 to 20 years. Historically, the 

number of aircraft, aircraft size (i.e., passenger capacity), and the number of aircraft operations have 

all increased to accommodate the growing number of passengers; however, fewer new airports are 

being constructed, and the current airspace operations system is becoming saturated, thus making 

larger aircraft more attractive. Besides the benefcial efect on the air trafc control system, larger 

aircraft have also been one of the airlines’ main means of reducing operating costs. Carrying more 

passengers on fewer planes is a proven way of reducing costs, assuming load factors (i.e., percentage 

of seats flled per aircraft) remain constant, as was experienced by the introduction of wide-body 

aircraft such as the Boeing B747. VLST concepts like the BWB are defned as intercontinentalrange aircraft that carry more than 600 passengers. 

Te focal point of BWB interest at Langley was the Aeronautics Systems Analysis Division under the 

direction of Joseph R. Chambers. In 1995, several researchers led by Samuel M. Dollyhigh, Head 

of the Systems Analysis Branch, conducted independent research analyses of the BWB concept. 

Lead researcher for the group was Henri D. Fuhrmann, who conducted analyses of the mission 

performance capabilities of the McDonnell Douglas airplane and arrived at results that generally 

confrmed the beneft projections of Liebeck’s team. At that time, the vehicle design focused on an 

800-passenger BWB transport designed for a 7,000-nmi mission at a cruise Mach number of 0.85. 

Te performance estimates by both the McDonnell Douglas group and the independent NASA 

team indicated extraordinary capabilities. McDonnell Douglas estimated that, compared with an 

800-passenger conventional transport with the same advanced technologies, the BWB exhibited 20 

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percent lower fuel burned, 10 to15 percent less weight, and 20 percent lower direct operating costs. 

Both groups, however, recognized that many technical challenges would have to be met to reach 

the maturity levels required for a feasible confguration. Aerodynamics, structures and materials, 

fight controls, and propulsion technologies all presented formidable problems. Obviously, many 

research projects and data would be required to address these issues. 

Te Advanced Concepts Program 

In 1994, NASA initiated a new program named the Advanced Concepts for Aeronautics Program 

(ACP) to stimulate revolutionary research in aeronautics, encouraging the participation of NASA 

researchers, industry, and academia in teamed eforts to investigate precompetitive and potentially 

high payof aeronautical concepts. Te systems analysis studies and interactions that had already 

occurred between Langley and McDonnell Douglas ofered an excellent technical foundation for 

a potential ACP project for the BWB. After Joe Chambers presented the advocacy for the project 

proposal to managers at NASA Headquarters, a 3-year project on BWB confgurations was awarded 

to a team composed of McDonnell Douglas (team leader), NASA Langley, Stanford University, 

NASA Lewis (now NASA Glenn), the University of Southern California, the University of Florida, 

and Clark-Atlanta University. Te latest version of the McDonnell Douglas 800-passenger, 7,000-

nmi confguration was used for the study. 

Langley members of the ACP efort in 1995 included Cheryl A. Rose, Daniel G. Murri, Vivek 

Mukhopadhyay, Tomas M. Moul, Robert E. McKinley, Marcus O. McElroy, Ty V. Marien, 

Henri D. Fuhrmann, James R. Elliott, Dana J. Dunham, and Julio Chu. Elliott, who was initially 

ACP team lead was followed by McKinley in 1997. 

Te BWB concept for the ACP study had two full passenger decks in a typical long-range, threeclass arrangement within a thick (about 17-percent thickness) centerbody. Te seating was laid 

out in fve parallel single aisle compartments on each deck. Each compartment was approximately 

equivalent to a very short narrow body aircraft, and even though the passenger complement was 

relatively high, the overall egress paths for passengers were shorter than most large conventional 

confgurations. Te estimated takeof gross weight of the aircraft was 823,000 lbs (about threequarters composites and one-quarter metal), and it used three 60,000-lb class turbofan engines. 

Te engines were located on top of the wing, aft of the passenger compartment. Tis arrangement 

worked well for balance and had several benefcial side efects. Te turbines and compressors were 

completely clear of the main structural elements, pressurized compartments, and fuel, which could 

improve safety. Also, the large fans on the high-bypass ratio engines were shielded from the ground 

by the centerbody, which was expected to improve the community noise characteristics. 

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Te traditional low-speed, high-lift challenge associated with defecting trailing-edge faps (trim 

and net lift) was recognized in this design. Trailing-edge surfaces were not used as faps, resulting 

in a maximum lifting capability less than that of a conventional fapped-wing design. To provide 

sufcient lift, the BWB wing loading was made substantially lower than the conventional norm by 

increasing the wing area. Leading-edge slats were used for additional lift at high angles of attack. 

One of the numerous highlights of the ACP study was the highly successful development and 

fight testing of a large-scale, remotely controlled model of the BWB confguration by a team at 

Stanford under the direction of Professor Ilan Kroo. Te Stanford group designed, fabricated, 

instrumented, and few a large, 6-percent scale (17-ft wing span) model to explore the low-speed 

fight mechanics of the BWB as a relatively low-cost frst step to defne the stability and control of 

the confguration, especially at high angles of attack. Powered by a pair of pusher propellers, the 

“BWB-17” was dynamically scaled to predict the fight characteristics of a full size BWB. Stability 

augmentation and control laws were provided by an onboard computer that also recorded fight 

test parameters. 

Initially, Kroo’s students constructed and conducted exploratory fight tests of a 6-ft span model, 

which was fown in 1995 as a glider and later under powered conditions (using pusher propellers). 

Tey also conducted innovative semiconstrained car-top testing to check out the model prior to 

free fight. In this technique, they mounted the model to a test rig above an automobile, and the 

Te 6-percent remotely controlled blended wing body model fown by the Stanford University Advanced Concepts 

for Aeronautics Program team. 

model was free to rotate about all three axes. By releasing the model from a fxed angle of attack 

and observing the ensuing motions, the students were able to assess the efectiveness of an angleof-attack limiter that guards against possible stall departure. Te students tested the limiter using 

increasingly aggressive inputs and found it to be highly efective at preventing unwanted high 

angle-of-attack excursions. Te students also developed a piloted simulator and studied several 

aspects of stability augmentation, including gain scheduling. 

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In 1997, the BWB-17 model underwent numerous research fights demonstrating the satisfactory 

fying characteristics of the BWB confguration. It was also fown before a highly impressed VIP 

audience of industry, NASA, and DoD representatives at El Mirage, California. 

Meanwhile, other ACP team members were contributing additional data and results. Te Langley 

team continued to conduct systems analyses of the mission capability of the BWB, estimates of 

aerodynamic performance for the airframe, and analyses of structural concepts that might meet 

the demanding requirements of the pressurized noncircular centerbody. 

Te NASA ACP-sponsored BWB study ended in 1998. At the end of the study, refned analysis 

had concluded that the performance of the BWB relative to a conventional confguration for 

the mission selected was indeed revolutionary. In comparison with the conventional design, the 

McDonnell Douglas estimates for BWB benefts included a reduction in takeof gross weight 

of 15.2 percent, an increase in cruise L/D ratio of about 20 percent, a reduction in fuel burned 

of about 28 percent, and a reduction in direct operating costs of about 13 percent. Langley’s 

independent analysis projected benefts about half as large as the McDonnell Douglas values, with 

diferences attributed to higher NASA estimates of centerbody structural weight. 

In comparison with the operational Boeing B747-400 airplane, the BWB had a 60-ft wider wing 

span, was 70-ft shorter in length, carried twice as many passengers, weighed about 7 percent less, 

and used fewer engines. Despite the excitement of the study projections, the team cited that many 

challenges and technology verifcation demonstrations would be required in the areas of structures 

and materials, aerostructural integration, aerodynamics, controls, propulsion-airframe integration, 

systems integration, and airport infrastructure. 

Advanced Subsonic Technology Program 

In 1997, Richard J. Re conducted wind-tunnel tests of a rudimentary BWB model (no engines or 

winglets) in the Langley National Transonic Facility (NTF) as part of the NASA-industry Advanced 

Subsonic Technology (AST) Program led by Samuel A. Morello. Part of the AST Integrated Wing 

Design element, the project’s objective was to evaluate the capability of advanced CFD methods to 

predict the aerodynamic characteristics of an advanced, unconventional confguration. 

Boeing personnel generated CFD solutions using several codes, including the Langley-developed 

CDISC code, developed by Richard L. Campbell. Separate but coordinated CFD eforts were 

also conducted at Langley and results used to assess engine inlet conditions and wind-tunnel sting 

interference efects. Te data and detailed pressure distributions guided many design refnements 

82 Innovation in Flight 
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to the BWB confguration. Te CFD tools accurately predicted the aerodynamic data from cruise 

to bufet onset. Tis test was the frst high-speed wind-tunnel study of the BWB confguration, 

and it was deemed particularly important because test data indicated that a confguration 

with a relatively thick centerbody could be designed for efcient cruise at high subsonic speeds 

(Mach 0.85). 

Blended Wing Body model undergoing tests in the Langley National Transonic Facility. 

Interest in X-Planes 

In the late 1990s, NASA expressed a renewed level of interest in X-plane projects, such as those that 

had generated so much enthusiasm and interest in past NACA and NASA aeronautics programs. 

Serious discussions occurred within industry and NASA for a manned, subscale jet-powered BWB 

airplane that would be capable of high-subsonic cruise evaluations during fight tests at NASA 

Dryden. In October 1996, a proposal white paper from industry and Langley BWB enthusiasts 

reached senior industry management and NASA Administrator Daniel S. Goldin. Te proposed 

X-plane BWB confguration was for a 26-percent scale vehicle having a wingspan of 74 ft and a 

projected program cost of about $130 million. Te NASA Administrator initially appeared to be 

supportive, but did not approve the proposal for go ahead. 

McDonnell Douglas merged with Boeing in August 1997, and an immediate activity was 

undertaken by Boeing to reevaluate the BWB concept for its maturity, mission suitability, and its 

ability to conform to company strategies and outlook for future air travel requirements. Results of 

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the Boeing study indicated that a very large 800-passenger airplane was not an appropriate vision, 

and that the BWB studies should refocus on a smaller, 450-passenger (240-ft wingspan) airplane. 

Also, certain confguration features, such as the propulsion installation, changed and the engines 

were mounted on upper surface pylons. Issues such as X-planes were put on hold. 

Flight Research Revisited 

In 1997, Darrel R. Tenney, Director of the Airframe Systems Program Ofce, initiated a series of 

in-house team studies to determine if Langley could support the fabrication and development of 

a series of unmanned, remotely controlled air vehicles that could be fown to support Langley’s 

interest in revolutionary confgurations. Langley’s Director, Jeremiah F. Creedon, strongly 

supported the studies. At the same time, Joseph R. Chambers’ staf in the Aeronautics Systems 

Analysis Division proposed a related new program based on the selection of precompetitive 

advanced confgurations that would be designed, evaluated, fabricated, and test fown using 

remotely piloted vehicle technology at Dryden. Te program, known as Revolutionary Concepts 

for Aeronautics (RevCon), would be based on a 4-year life cycle of support for concepts selected. 

Initial reactions to the proposed program from NASA Headquarters and Dryden were favorable, 

and following intercenter discussions, a formal RevCon Program was initiated in 2000, which was 

led by Dryden. Following a review of other advanced vehicle concepts by an intercenter team, the 

team selected the BWB as one of the concepts for further studies. 

Under the Revolutionary Airframe Concept Research and System Studies (RACRSS) element of 

Airframe Systems, Robert E. McKinley led the interactions among Langley, Dryden, and Boeing. 

Initially, Boeing had proposed to fabricate a low-speed fight model of the BWB and Langley was 

planning to commit to fabrication and testing of a high-speed unpowered drop model. However, 

when Boeing could not support the low-speed model, Langley assumed responsibility for the design 

and fabrication of a model with Dryden supporting development of the fight control system. Te 

14.2-percent scale BWB low-speed vehicle (LSV) was to have a wingspan of 35 ft, a maximum 

weight of about 2,500 lbs, and be powered by three jet engines of the 200-lb class. Te BWB 

confguration would be based on the BWB-450 design from the Boeing studies and was given the 

formal designation of X-48A. Project Manager of the RACRSS program was Bob McKinley, with 

the assistance of LSV Project Managers Wendy F. Pennington and Kurt N. Detweiler, and Chief 

Designer William M. Langford. 

Te LSV Program encountered major problems as fight control system development had to be 

put on hold when commitments to other programs changed the Agency’s priorities and resource 

allotments. However, the program had successfully completed a preliminary design and review of 

84 Innovation in Flight 
THE BLENDED WING BODY: CHANGING THE PARADIGM 

Construction of the Blended Wing Body Low-Speed Vehicle 

in a Langley shop. 

the vehicle’s airframe, an initial round of structural material coupon and element testing, structural 

design of proof-of-concept wing box testing, and fabrication/assembly of the centerbody and wing 

molds for the composite LSV. Te LSV Program was subsequently terminated by NASA because 

of higher priority program commitments. 

After cancellation of the LSV, Langley moved toward the possibility of conducting lower cost 

low-speed free-fight tests of a smaller 5-percent scale model in the Langley Full-Scale Tunnel. In 

2002, Boeing contracted Cranfeld Aerospace Limited in England for the design and production 

of a smaller, 21-ft span LSV-type vehicle. 

Flight Dynamics 

Research of fight dynamics (stability, control, and fying qualities) is a particularly challenging 

area for unconventional confgurations, such as the BWB. Tus, exhaustive studies have been 

conducted by the Langley staf to provide critical information for design refnements. Te early 

eforts started with testing of a 4-percent scale model of the 800-passenger design in the Langley 

14- by 22-Foot Tunnel during 1997. Te research team, headed by Daniel G. Murri, obtained 

quantitative stability and control characteristics for low-speed fight conditions, including the 

efects of power and fow visualization. 

In the later LSV commitment, Langley researchers conducted timely wind-tunnel tests and other 

analyses to support the project. Tree diferent models were tested in three diferent wind tunnels. 

A team led by Dan Murri, Dan D. Vicroy, and Sue B. Grafton tested a 3-percent scale model of 

the BWB-450 in the Langley 14- by 22-Foot Tunnel in late 1999. Te scope of testing included: 

conventional unpowered static tests to defne performance and stability and control characteristics 

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BWB-450 model used for initial tests in the Langley 14- by 22-Foot Tunnel. 

(including ground efects), unique forced-oscillation tests to determine dynamic aerodynamic 

characteristics, assessments of wing leading-edge slat confgurations, and extremely large angle 

tests to determine aerodynamic characteristics over a complete 360° angle-of-attack range, giving 

a range of sideslip angle of –90° to +90°. Te latter tests were conducted to obtain input data for 

analysis of tumbling characteristics, as will be discussed. During these tests, unexpected results 

were obtained on aerodynamic interference efects between the high-lift leading-edge slats and the 

rear-mounted engines, providing design information on how to alleviate a potential problem. Te 

data also provided information on trailing-edge control allocation strategies for efcient lift, trim, 

and stability. Te team conducted additional trailing-edge aerodynamic control interaction studies 

in a low-speed 12-ft tunnel at Langley. 

Other models were used to examine the confguration’s characteristics at extreme angles of attack. 

A team led by Charles M. (Mike) Fremaux and Dan Vicroy tested a 1-percent scale spin model of 

the BWB-450 in 1999 in the Langley 20-Foot Vertical Spin Tunnel, and they used a 2-percent 

scale model in rotary-balance testing in 2001 to determine the aerodynamic characteristics 

associated with spinning attitudes and angular rates. In free-spinning tests, the team assessed 

spin and recovery characteristics of the 1-percent scale model, determined the size of emergency 

spin recovery parachute required for the proposed LSV vehicle, and explored the confguration’s 

tumble characteristics. 

Experiences with fying-wing confgurations during the 1940s and 1950s raised concern about an 

uncontrollable tumbling phenomenon, during which the vehicle would autorotate in pitch with 

86 Innovation in Flight 
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BWB-450 model used for unconventional large angle tests. 

Model is positioned for airfow coming into the upper rear. 

continuous 360° pitching motions. Te tumbling motions were precipitated either by stalls or by 

fight at high angles of attack that resulted in massive separation of fow on the wing. Researchers 

in the Langley Spin Tunnel have conducted extensive studies up to the current day for predicting 

the phenomenon and identifying airplane characteristics that precipitate the problem. Even though 

it is generally agreed that a modern BWB transport confguration will use an angle-of-attack 

limiting concept in its fight control system to prevent tumbling, information on behavior during 

forced-tumble motions is of great value to the fight control designer. Mike Fremaux and Dan 

Vicroy conducted tumbling tests of the 1-percent scale model using a special 1-degree-of-freedom 

model mounting system in late 1999 and early 2000. Tese experimental results were augmented 

by theoretical calculations of the tumbling motions conducted by Dan Murri and Eugene Heim 

Free-spinning tests of a Blended Wing Body model in the 

Langley 20-Foot Vertical Spin Tunnel. 

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using aerodynamic data from static and dynamic wind-tunnel tests. Te calculated motions were 

in close agreement with the observed free-tumbling results, providing good calibration for the 

mathematical model approach used in the simulated motions. 

Langley researchers have also formulated and used piloted simulator studies of BWB confguration 

handling qualities to assess stability and control characteristics. Dan Murri led initial terminal-area 

(low-speed) studies of a BWB-800 confguration in the Langley Visual Motion Simulator (VMS), 

with Langley research pilot Robert A. Rivers and Boeing pilot Mike Norman providing assessments 

of the confguration’s handling qualities. Other simulator studies have been implemented and 

checked out for use on the Generic Flight Deck (GFD) simulator. Objectives of these simulator 

eforts were to evaluate fying and handling qualities in the terminal area and to develop and refne 

control system elements and logic, including control allocation and envelope protection schemes. 

Aerodynamic Performance 

Aerodynamic performance refnements have continued to improve the BWB’s predicted capabilities. 

Langley’s expertise and tools have contributed valuable guidance and direction in these eforts. 

For example, Boeing’s use of the Langley-developed CFD codes CDISC and CFL3D (developed 

by Richard L. Campbell and James L. Tomas, respectively) permitted extensive benefcial 

modifcations of pressure distributions while maintaining constraints within cabin geometry, 

pitching moments, and span load distributions. Tese advances evolved the confguration’s 

centerbody into a thinner section, resulting in a higher level of L/D ratio at cruise. Using these 

powerful design tools has also contributed to the sophistication of the wing airfoil characteristics. 

In the past, fying wings achieved longitudinal trim by using wing sweep and downloading the 

wingtips, resulting in a severe induced-drag penalty. With this approach, fying wings have not 

lived up to the performance potential. In contrast, the use of advanced wing design methods has 

permitted the BWB to be trimmed by careful distribution of wing trailing-edge camber and by the 

judicious use of wing twist (washout). 

In 2004, Richard L. Campbell and Melissa B. Carter used CDISC, coupled with the USM3D 

unstructured grid Navier-Stokes fow solver, to improve the propulsion-airframe integration 

characteristics of a BWB confguration with boundary layer ingestion nacelles. Wind-tunnel 

models incorporating the baseline and redesigned geometry were built by Langley and tested in 

August 2004 at high Reynolds numbers in the NTF to verify the CFD design method. Campbell, 

Carter, and Odis C. Pendergraft, Jr., led the testing team. NTF force and moment data correlated 

well with CFD results in general, and matched predicted cruise drag reduction for redesign within 

the data’s uncertainty. Experimental data also confrmed predicted changes in wing pressures in 

88 Innovation in Flight 
THE BLENDED WING BODY: CHANGING THE PARADIGM 

the design region near the nacelles. An intercenter team led by Langley’s A. Neal Watkins, William 

K. Goad, Cliford J. Obara, and Ames’ James H. Bell contributed a revolutionary fow visualization 

method for the unique environment of cryogenic fow in the NTF. Te visualization results were 

used to further verify the CFD design method, indicating that fow features such as wing shock 

and boundary layer separation were accurately located in the computations. 

Structures and Materials 

Langley and Boeing interactions have addressed the formidable multidisciplinary challenges of 

designing a centerbody for the BWB with satisfactory structural weight, passenger accommodation, 

and pressurization within the confguration’s aerodynamic lines. In a conventional circular fuselage 

section, a thin skin carries internal pressure efciently via hoop tension. If the fuselage section is 

noncircular, internal pressure loads also induce large bending stresses. Te structure must also 

withstand additional bending and compression loads from aerodynamic and gravitational forces. 

Critical contributions from Langley staf in structures for the BWB have included development 

of a rapid structural code for preliminary design known as Equivalent Laminated Plate Solution 

(ELAPS). Developed by Gary L. Giles, this analysis method generates in a timely manner conceptuallevel design data for aircraft wing structures that can be used efectively by multidisciplinary 

synthesis codes for performing systems studies. Samuel M. Dollyhigh’s systems analysis groups 

used ELAPS for early conceptual studies during BWB assessments. 

Researcher Vivek Mukhopadhyay conducted preliminary studies of structural concepts for 

noncircular fuselage confgurations, focusing on multiple fuselage bays with noncircular sections. 

In his studies, fat and vaulted shell structural confgurations were analyzed using deep honeycomb 

sandwich-shell and ribbed double-wall shell construction approaches. Combinations of these 

structural concepts were analyzed using both analytical and simple fnite element models of isolated 

sections for a comparative conceptual study. Weight, stress, and defection results were compared 

to identify a suitable confguration for detailed analyses. Te fat sandwich-shell concept was found 

preferable to the vaulted shell concept due to its superior buckling stifness. Vaulted double-skin 

ribbed shell confgurations were found to be superior due to weight savings, load difusion, and 

fail-safe features. Te vaulted double-skin ribbed shell structure concept was also analyzed for an 

integrated wing-fuselage fnite element model. 

Additional problem areas such as wing-fuselage junction and pressure-bearing spar were 

identifed. Mukhopadhyay also teamed with Jaroslaw Sobieski to analyze and develop a set of 

structural concepts for pressurized fuselages of BWB-type fight vehicles. A multibubble fuselage 

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confguration concept was developed for balancing internal cabin pressure load efciently using 

balanced membrane stress in inner cylindrical segment shells and intercabin walls. Additional 

cross-ribbed outer shell structures were also developed to provide buckling stability and carry 

spanwise bending loads. In this approach, it was advantageous to use the inner cylindrical shells 

for pressure containment and let the outer shells resist overall bending. 

Support for the proposed LSV development challenged the Langley design and engineering group 

in the area of structures. William M. Langford designed and Regina L. Spellman analyzed an 

approach to LSV structural design. Te dynamic scaling requirements for the LSV caused great 

difculty in designing an airframe with the necessary strength and stifness within the strict 

weight limits. Due to the vehicle’s unusually large size, there were limitations to Langley’s in-house 

composite fabrication capabilities and resources. Tese combined restrictions limited the design 

to a room temperature cure composite design. Te design group also implemented an extensive 

materials characterization efort to identify materials and processes to meet the demanding 

requirements, and a proof-of-concept article was fabricated and tested. 

Acoustic tests of the BWB-800 confguration in the Langley Anechoic 

Noise Research Facility. 

Noise 

Te unique layout of the BWB confguration places the noise generating engines above and at the 

rear of the wing-centerbody upper surfaces, suggesting that a signifcant reduction in projected 

noise might be obtained from structural shielding as compared with conventional confgurations. 

To investigate and quantify any benefts of the BWB confguration, Langley researchers Lorenzo 

R. Clark and Carl H. Gerhold conducted acoustic tests of a 4-percent scale, 3-engine nacelle 

90 Innovation in Flight 
THE BLENDED WING BODY: CHANGING THE PARADIGM 

model in the Anechoic Noise Research Facility at NASA Langley Research Center. Te test team 

placed a high-frequency wideband noise source inside the nacelles of the center engine and one of 

the side engines to simulate broadband engine noise. Tey also measured the model’s sound feld 

with a rotating microphone array that was moved to various stations along the model axis and with 

a fxed array of microphones that was erected behind the model. While no attempt was made to 

simulate the noise emission characteristics of an aircraft engine, the model source was intended 

to radiate sound in a frequency range typical of a full-scale engine. Clark and Gerhold found that 

the BWB confguration provided signifcant shielding of inlet noise. In particular, noise radiated 

downward into the forward sector was reduced by as much as 20 to 25 dB overall at certain fullscale frequencies. 

Status and Outlook 

NASA sponsorship of early BWB concept studies in 1993 has played a key role in the development 

of subsequent designs. Currently, disciplinary studies in several areas have continued at Langley, 

and the BWB concept as a future transport has become one of the focal points of NASA’s vision 

of future air vehicles. Such focal points are being used to steer the direction of fundamental 

disciplinary research conducted within NASA toward high-payof areas. Boeing has continued its 

close working relationship and cooperative studies with Langley while pursuing other markets for 

the BWB, including potential applications such as a large cargo transport or a military in-fight 

refueling transport to replace the aging KC-135 feet. As a tanker, the BWB ofers signifcant 

advantages, such as the ability to refuel more than one aircraft at a time. Many believe that the frst 

applications of the BWB confguration will be for military uses with civil applications to follow. 

Dan D. Vicroy is leading an investigation of the free-fight characteristics of a 5-percent scale BWB 

model in the Langley Full-Scale Tunnel in 2005. Te model fight tests are designed to provide 

further information on the fight dynamics of the confguration, including an assessment of stability 

and control characteristics for engine-out conditions at the edge of the low-speed envelope. One 

innovative example of this research will be the possibility of using thrust vectoring of the center line 

engine for auxiliary yaw control when one of the outer engines becomes inoperative. If successful, 

this application would be the frst example of thrust vectoring used for a transport confguration. 

In addition to these low-speed tests, Boeing is also planning cooperative acoustic testing of a 

3-percent model. 

Under leadership of Robert M. Hall and Charles M. Fremaux, Langley is now assessing 

the ability of advanced CFD codes to predict static and dynamic stability characteristics of 

BWB confgurations. Te CFD team includes Paul S. Pao, Robert E. Bartels, Robert T. Biedron 

and Neal T. Frink. 

Innovation in Flight 91 
THE BLENDED WING BODY: CHANGING THE PARADIGM 

Artist’s concept of a military blended wing body application. 

Langley is now considering variants of advanced versions of the BWB in continual system studies 

of the benefts of various confgurations in future air transportation scenarios. In these studies, 

advanced technologies, such as hybrid laminar fow control and buried engines, result in BWB 

designs with even more potential than those researched thus far. Finally, piloted simulator studies 

of the BWB-450 confguration are planned for the Langley GFD simulator, and (with additional 

wind-tunnel data) far-term plans include eventual full-envelope simulation that will include the 

efects of compressibility and aeroelasticity. 

Te excitement and revolutionary capabilities of the BWB concept have not gone unnoticed 

by other international aircraft industries. France and Russia have conducted research on BWB 

confgurations since the early 1990s. Tis interest has intensifed and spread to other European 

nations, as evidenced by exhibits at the Berlin International Aerospace Exhibition held May 6–12, 

2002. Airbus, ONERA/DLR, and TsAGI presented elaborate displays of BWB models and research 

activities at that international gathering of aerospace industry members. European collaboration 

on the BWB is obvious and accelerating, and the future global market for such confgurations will 

be very competitive. In addition, the celebrated frst fight of the super jumbo Airbus A380 in April 

2005 has ushered in a new era of interest in very large transports. 

In summary, the NASA Langley Research Center funded and stimulated the creation and initial 

development of the BWB concept, and the Center’s interaction with industry and universities 

has resulted in valuable technical contributions that have brought continuing maturity to the 

concept. Langley’s involvement in the BWB concept has been based on two traditional NASA 

roles in aeronautics: (1) the assessment of disciplinary design issues (especially of-design problems) 

for revolutionary vehicles, and (2) a credible independent assessment of revolutionary concepts 

that signifcantly advances the state of the art of aeronautics with the potential to change 

the paradigm. 

92 Innovation in Flight 
Synthetic Vision: Enhancing Safety and Pilot 

Performance Through Virtual Vision 

Concept and Benefts 

Arguably, the most important physical human sense for piloting an aircraft is that of sight. 

Visibility is a key requirement for situational awareness, orientation, defensive warning and collision 

avoidance, and precision maneuvers. All aspects of aviation, including the airborne and ground 

operation of military, commercial, business, and general aviation airplanes, are severely impacted 

by limited visibility, resulting in degraded (perhaps catastrophic) safety and signifcant delays or 

cancellation of scheduled fights. 

Restricted visibility is a major contributor to a class of accidents referred to as controlled fight 

into terrain (CFIT) wherein a fully functional aircraft collides with the ground, water, or other 

obstacles due to pilot disorientation, lack of awareness, or confusion. More than 1,750 people 

have died worldwide in airliner accidents due to CFIT since 1990, and a recent Boeing study 

indicates that a worldwide average of over 200 commercial jet CFIT fatalities occur per year. Such 

accidents may be precipitated by loss of orientation, unanticipated terrain features, and loss of key 

navigational and maneuver cues, especially under weather-related conditions or at night. 

In addition to potentially catastrophic visibility-related conditions encountered during fight, a 

signifcant safety issue has been experienced during aircraft ground operations in low-visibility 

conditions. Te world’s worst aviation accident involved runway incursion, which involves potential 

collision hazards caused by the inadvertent intrusion of aircraft, vehicles, people, or other objects 

on runways. On March 27, 1977, a collision between a KLM 747-200 transport and a Pan Am 

747-100 transport at Tenerife, Canary Islands, killed 578 passengers and crew members. Because 

of limited visibility and communications difculties between air trafc control and the KLM 

aircraft, the KLM 747 started its takeof while the Pan Am aircraft was on the same runway, 

resulting in a horrible fatal collision. 

In reaction to an increasing number of nonfatal runway incursion incidents, the topic of runway 

incursion has ranked among the top fve items on a list of high-priority issues identifed by the 

National Transportation Safety Board (NTSB) for the last 6 years. 

Today, unprecedented advances in modern computer capabilities and remote sensing technologies 

that can rapidly and accurately provide Earth-referenced models of geographic features—such as 

terrain, vertical obstructions, airport runways and taxiways, and advanced cockpit displays—have 

led to exciting new research on the development of cockpit display technologies. Tese technologies 

could eliminate low visibility accidents by providing the pilot with an accurate, realistic virtual 

image of the environment surrounding the aircraft, as well as guidance for safe maneuvers within 

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physical constraints. Developments in this area have initially focused on enhanced vision systems 

(EVS), which use sensors such as forward looking infrared (FLIR) systems, systems, millimeter 

wave sensors, and other approaches based on information obtained from active onboard sensors. 

Results obtained from EVS studies and applications indicate improvements in awareness and 

safety; however, an innovative new technology involving “synthetic” vision promises to provide 

revolutionary all-weather operations without the loss of visibility. 

Synthetic vision systems (SVS) difer from EVS technology in that they consist of a computer 

database-derived system (rather than sensors) that uses precise Global Positioning System (GPS) 

navigation, stored models of geospatial features, and integrity-monitoring sensors to provide an 

unrestricted synthetic view of the aircraft’s external environment, including trafc depiction during 

airborne and ground operations. SVS provides an intuitive perspective view of the outside world in 

a manner sufcient for aircraft tactical guidance. Te system is driven by airplane attitude from an 

inertial reference unit, GPS position, and a predetermined internal database that contains airport, 

terrain, obstacle, and path information for specifc locales. Te technology paints and displays 

a three-dimensional computer picture of the outside world so that pilots can see runways and 

obstacles, and they are given guidance information independent of weather conditions and time of 

day. In addition, SVS uses maneuver guidance features, such as “highway in the sky” concepts to 

reduce workload and potential disorientation in restricted visibility. 

Artist’s concept of advanced cockpit display with synthetic vision head-down 

and head-up displays. 

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For ground operations, SVS provides an electronic moving map of the airport surface— indications 

of obstacles, hold short locations, and other trafc—to help prevent inadvertent runway incursions. 

Other surface hazards can be avoided using SVS, such as wrong turns, taking of on the wrong 

runway, pilot confusion/disorientation at unfamiliar airports, and confusion resulting from 

language barriers. 

Te monumental challenge of building accurate airport and terrain databases for worldwide SVS 

operations has been met in large part thanks to data derived during dedicated Space Shuttle 

missions as well as other terrain measurement activities. During these focused missions, 80 percent 

of Earth’s land surface (99.96 percent of land between 60° N and 56° S latitude) was mapped 

sufciently for SVS enroute requirements. Shuttle Endeavor was launched in February 2000 (Shuttle 

Radar Topography Mission) on a 10-day efort to map the Earth, resulting in an 18-month data 

processing output. Te primary objective of the DoD mission, conducted jointly with the National 

Imagery and Mapping Agency (NIMA), now called the National Geospatial-Intelligence Agency 

(NGA), was to acquire a high-resolution topographical map of the Earth’s land mass. Tis activity 

represented a breakthrough in the science of remote sensing by producing topographical maps of 

Earth many times more precise than those previously available. Such databases (i.e., models) are 

currently being produced by both government and commercial entities on a global basis. 

Challenges and Barriers 

SVS promises unprecedented capability, but it also faces numerous operational issues and technical 

challenges, including the generation of reliable computer-based airport and terrain features, 

requirements for efective displays and onboard computational capability, certifcation issues, 

maintenance requirements, integration of fight-critical SVS into the airspace and transportation 

system, and the all-important issues of afordability and retroftability. Te following discussion 

identifes disciplinary and operational issues that have surfaced during NASA research on the 

technologies associated with SVS, most of which have been addressed and resolved by the eforts 

of Langley and its partners. 

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Disciplinary and Operational Challenges 

Requirements for successful implementation of SVS technology are dominated by the fact that 

the concepts must meet fight-critical system requirements. Te robustness of databases and 

computational systems is obviously critical, and failure modes and recovery strategies must be 

defned. Large deviations in database requirements will exist between various classes of aircraft 

(such as commercial transports versus general aviation), and the augmentation requirements for 

sensors of the various classes of vehicles must be addressed. 

Development and demonstration of afordable, certifable display confgurations for aircraft involves 

major retroft issues associated with this advanced display technology because to measurably impact 

safety and operations, a majority of the feet has to be impacted positively. Te actual and projected 

worldwide jet aircraft feet shows that the majority of transports are now, and will remain, those 

equipped with glass cockpits. Te display drivers, graphics drivers, and drawing capability necessary 

to host a synthetic vision display system are not in place for most aircraft. Additional equipment 

required for SVS includes GPS, an inertial reference unit (IRU), pilot controls/interfaces, several 

databases, and a computing host. 

An opportunity may exist to use emerging head-up display (HUD) systems as a cost-efective retroft 

path for SVS in HUD-equipped aircraft. Tis display concept is analogous in many respects to the 

EVS now certifed and ofered to customers on the Gulfstream V (GV) business jet, although the 

SVS raster image is synthetically derived rather than being a direct imaging sensor output. Also, 

evaluations of the potential advantages or disadvantages of head-down displays (HDD) must be 

conducted, particularly as a potential low-cost alternative for general aviation. 

Display issues include the luminance, feld of view, resolution, and display details required for 

satisfactory operations. Display content and computational onboard power requirements, cost, 

failure modes, and other details must also be studied. Ensuring accuracy and integrity of the 

terrain and global topology data used by SVS is a mandatory and critical task. Inadvertent use of 

inaccurate or misleading information will not be tolerated for potential applications. 

Langley Activities 

NASA Langley Research Center has conducted extensive research on pilot-vehicle display interfaces 

with a view toward safer, more efcient fight operations. In its early days as an NACA research 

laboratory, Langley led the world in studies of aircraft handling qualities and pilot-control system 

interface requirements, and explored IFR factors that result in accidents. As a NASA research 

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Conceptual head-up and head-down synthetic vision displays. 

center, Langley has contributed some of the most signifcant technology ever produced on topics 

such as loss of control and orientation in limited visibility conditions; glass-cockpit technology; 

windshear detection and avoidance; advanced displays to simplify piloting tasks (particularly for 

general aviation pilots) such as “highway in the sky” and takeof-performance monitoring displays; 

and fundamental human-display interface issues. Two past NASA programs, known as the Low 

Visibility Landing And Surface Operations (LVLASO) project and the HSR Program External 

Visibility System (XVS) element were crucial to start up and development of the SVS research 

conducted at the Center. Langley researchers have therefore exercised considerable expertise and 

experience in advancing the SVS concept. 

In conducting its research mission in the SVS area, Langley is intensely integrating its eforts 

with those of the FAA, industry, DoD, and academia. In view of international interest and the 

signifcant potential payof in reducing aviation accidents, this coordinated, teamed arrangement 

is accelerating the state of the art and maturing the technology base required for safe and efective 

applications in future civil and military aircraft. 

Te following discussion provides an overview of signifcant activities undertaken by Langley on 

SVS technology. 

Te NASA Aviation Safety and Security Program 

In response to White House Commission on Aviation Safety and Security recommendations in 

1997, NASA created an Aviation Safety Program (AvSP) to research and develop technologies 

focused toward a national goal of reducing the fatal aircraft accident rate by 80 percent by 2007. 

With aviation security taking on new importance, the program has been expanded to the Aviation 

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Safety and Security Program (AvSSP) to directly address the safety and security research and 

technology needs of the Nation’s aviation system. Safety research in AvSSP develops prevention, 

intervention, and mitigation technologies and strategies aimed at one or more causal, contributory, 

or circumstantial factors associated with aviation accidents. Within the program, AvSSP contains 

an element called vehicle safety technologies, which includes synthetic vision systems. Te SVS 

project started as a fully funded segment of AvSSP in 2000 with a planned project life of 5 years. 

Langley’s Michael S. Lewis initially served as the Director of the AvSP, with George B. Finelli 

serving as Deputy Director. Daniel G. Baize was assigned as Project Manager for SVS, and Russell 

V. Parrish was the project’s Chief Scientist. Key Langley team members of the initial SVS project 

included James R. Comstock, Jr., Dave E. Eckhardt, Steven Harrah, Richard Hueschen, Denise 

R. Jones, Lynda J. Kramer, Raleigh (Brad) Perry, Jr., John J. White, III, and Steven D. Young. Te 

team also included representatives from NASA Ames and Dryden Research Centers. 

Synthetic vision research attempts to replicate the safety and operational benefts of clear-day fight 

operations for all weather conditions. Te Aviation Safety Program envisions a system that would 

use new and existing technologies, such as GPS navigational information and terrain databases, 

to incorporate data into displays in aircraft cockpits. Te displays would show terrain, ground 

obstacles, air trafc, landing and approach patterns, runway surfaces and other relevant information 

to the fight crew. Te display includes critical fight path aids for reducing pilot workload and 

ensuring the appropriate and safe maneuver is followed. 

Remarkable accomplishments of the SVS project have included critical technologies that enable 

key capabilities of the synthetic vision concept. With extensive in-house studies, as well as precisely 

planned cooperative activities with government, industry, and other partners, the Langley team 

has rapidly matured technologies and provided impressive demonstrations of the efectiveness of 

this revolutionary concept for both the commercial transport and general aviation communities. 

Te SVS project is composed of three elements or subprojects: commercial and business aircraft, 

enabling technologies, and general aviation. Te element on commercial and business aircraft 

focuses on issues particular to large jet transport aircraft and considers more expensive sensor 

augmented systems. Research on enabling technologies focuses on required supporting technologies 

such as the geospatial feature databases; communication, navigation, and surveillance (CNS) 

technologies; hazard detection functions; sensors; and system integrity approaches. Te general 

aviation element focuses on the particular needs and applications of general aviation aircraft, with 

sensitivity to relative expense of SVS. 

98 Innovation in Flight 
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Before reviewing the impressive accomplishments of the SVS project team, a brief review of various 

segments of past Langley research programs that have culminated in SVS technology is provided 

for background information. 

“Highway in the Sky” 

As early as the 1950s, researchers within civil and military communities began intense eforts to 

provide more intuitive and valuable artifcial guidance concepts for use in cockpit displays. Eforts 

in the United States were led by the military, which conducted extensive ground and fight studies 

of concepts that depicted the intended and actual aircraft fight paths on electronic instruments. 

Much of this research was led by the Navy’s George W. Hoover, who pioneered an early concept 

that became known as Highway in the Sky. Langley conducted eforts on conceptual pathwayin-the-sky technology in the 1970s, and although several research papers were written on the 

topic, little interest was shown from industry. In the early 1980s, Langley’s research eforts on 

fight problems associated with poor visibility included studies of critical factors that precipitated 

inadvertent loss of control incidents for typical general aviation pilots under IFR. A key research 

activity known as the Single Pilot IFR (SPIFR) project, led by John D. Shaughnessy and Hugh 

P. Bergeron, used piloted simulator studies and actual fight tests of representative subjects to 

highlight the difculty and potential dangers associated with such fight conditions. During the 

studies, a concept known as the “follow-me box” received considerable attention as an intuitive aid 

to inexperienced pilots during IFR fight. James J. Adams conducted in-depth simulator studies of 

the display, which used simplifed rectangular lines to form a guidance box to be followed in fight 

by the human pilot on a projected display. 

Later, the follow-me box concept was refned by Eric C. Stewart during simulator studies, where 

it was found that signifcant improvements in the piloting skills of relatively inexperienced 

general aviation pilots could be obtained using displays that provided the aircraft’s current and 

future fight path in a visual depiction similar to driving an automobile. Stewart’s research was 

conducted as part of the Langley General Aviation Stall/Spin Program, within a project known as 

“E-Z Fly.” Te project’s objective was making piloting tasks more natural for new pilots. Stewart 

further developed the highway in the sky concept, using a graphic consisting of line segments 

that provided an automotive highway depiction, even to the point of providing objects such as 

telephone poles for improved orientation. Using this concept, Stewart evaluated the performance 

of numerous test subjects, including nonpilots who had no airplane fight training before fying 

the simulator. Results obtained with the display were remarkable, with signifcant improvements 

in pilot guidance and response. In fact, individuals with no exposure to pilot skills were able to 

rapidly adapt to the guidance system and successfully fy full operational missions. Despite the 

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signifcant improvement observed in pilot performance, the fact that the concept was directed 

at the general aviation community’s low end, where computational requirements and cost were 

immediate barriers, stifed further research. 

In the mid 1990s, NASA formulated the Advanced General Aviation Transport Experiments 

(AGATE) Program to revitalize the ailing general aviation industry. With over $52 million and a 

consortium of NASA, FAA, and 80 industry members, the program included an element to develop 

more intuitive fight instruments. Te AGATE team recognized the potential value of advanced 

graphical displays designed to enhance safety and pilot awareness. Such systems would depict all 

fight parameters, as well as aircraft position, attitude, and state vector on the fight display. Noting 

industry’s movement toward a system that resembled a pathway-in-the-sky concept, AGATE 

planners decided to further develop such a system, reduce its cost, and enhance its commercial 

viability. Te system was designed to be a low-cost replacement for instrument panels with graphical 

displays. In 1998, a competitive cost-sharing contract focused on development of the frst phase 

of a highway-in-the-sky (HITS) display system was awarded to AvroTec Corporation. Te HITS 

system consisted of a navigational display showing horizon and relative attitude and a weather 

display depicting weather information. Avidyne replaced AvroTec during further development 

of the HITS concept. In July 2000, the HITS system was installed and successfully tested on 

a production Lancair Columbia aircraft. Led by Walter S. Green, the Langley AGATE Flight 

Systems Work Package Leader, the project culminated in a highly successful demonstration of the 

HITS display at the EAA AirVenture 2001 activities in Oshkosh, Wisconsin. 

Te NASA High-Speed Research Program 

While highway-in-the-sky concepts were being pursued in Langley’s General Aviation Program, 

additional research was being conducted to guide eforts for future applications to more sophisticated 

commercial transports and business jets. From 1994 to 1996, Langley held a series of interactive 

workshops focused on highway-in-the-sky concepts for commercial transports. Tese workshops 

brought together government and industry display designers and pilots to discuss and fy various 

concepts in an iterative manner. Te frst workshops primarily focused on the utility and usability 

of pathways and the pros and cons of various features available. Te fnal workshops focused on the 

specifc high-speed research applications to the XVS. Te NASA High-Speed Research Program 

was concerned with replacement of the forward windows in a second-generation high-speed civil 

transport with electronic displays and high-resolution video cameras to enable a “no-droop” nose 

confguration. By avoiding the Concorde-like drooped nose for low-speed operations, the future 

supersonic transport design could save considerable weight. Primary concerns in XVS application 

were preventing display clutter and obscuring of hazards as the camera image was the primary 

100 Innovation in Flight 
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Highway-in-the-sky concept in NASA AGATE Program. 

Highway-in-the-sky display in Cirrus SR-20 airplane. 

means of trafc separation in clear visibility conditions. Tese concerns were not so prominent in 

the frst workshops, which assumed an SVS application wherein hazard locations are known and 

obscuration is handled easily. 

Langley researchers led by Russell V. Parrish, James R. Comstock, Jr., Dave E. Eckhardt, Lynda 

J. Kramer, Steve Williams, Jarvis J. (Trey) Arthur, III, and Louis J. Glaab contributed to XVS 

from 1993 to 1999. Te XVS group conducted many simulation and fight test evaluations and 

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established overall requirements for displays. Lynda Kramer and her Boeing team members 

developed a surveillance symbology system and proved the no-droop nose concept’s feasibility. 

Early XVS fight tests used the U.S. Air Force’s Total In Flight Simulator (TIFS) and Langley’s 

B-737. Te fight research range covered issues regarding the adequacy of computer-generated 

outside views with camera views, horizontal feld of view requirements, conformal display and 

camera location issues, surveillance symbology, and guidance and fight control issues. Te project 

culminated in validating the no-droop nose concept cockpit with a full 50-degree vertical by 40-

degree horizontal feld of view. With this highly successful accomplishment, the high-speed civil 

transport research transitioned to the SVS element of AvSP. 

Conceptual synthetic vision system for a high-speed civil transport. 

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Te NASA Terminal Area Productivity Program and the Low Visibility Landing 

and Surface Operations Project 

From 1993 to 2000, NASA conducted a Terminal Area Productivity (TAP) Program aimed 

at developing requirements and technologies for terminal area operations that would safely 

enable at least a 12-percent increase in capacity at major airports in instrument meteorological 

conditions (IMC). TAP research activities comprised four subelements: air trafc management, 

reduced separation operations, aircraft-air trafc control integration, and LVLASO. LVLASO 

research was aimed at investigating technology as a means to improve the safety and efciency of 

aircraft movements on the surface during the operational phases of roll-out, turn-of, in-bound 

taxi, and out-bound taxi. Tis investigation was critical in the face of growing demands for air 

travel, the increasing number of reported surface incidents and fatal accidents, and the economic, 

environmental, and geographic infeasibility of constructing new airports or runways. During the 

LVLASO project, a prototype system was developed and demonstrated in order to validate an 

operational concept proposed to meet the project’s objective. Tis system concept was used to help 

defne international requirements for future advanced surface movement guidance and control 

systems defned by the International Civil Aviation Organization (ICAO). 

Te LVLASO system concept was built upon two display concepts called the Taxiway Navigation 

and Situational Awareness (T-NASA) system and the Roll-Out Turn-Of (ROTO) system. 

Te T-NASA system provided head-up taxi guidance and head-down moving map functions, 

whereas the ROTO system provided head-up guidance to pilot-selected exits during landing rollout. Te underlying system used GPS; an accurate airport database, including the locations of 

runways, taxiways, and center lines; and data link technology that provided trafc information 

and controller-produced routing, or path instructions. Te concept also included ground-based 

surface surveillance systems and controller displays. 

Because the LVLASO concept was based on using an accurate airport database and precise 

positioning via GPS, it is considered a form of SVS constrained to the landing and surface operational 

phases. At the onset of the SVS project, it was apparent that the lessons learned during LVLASO 

were directly applicable to SVS operational goals and objectives. Te SVS project challenge (2000 

to 2005) became integrating the LVLASO surface display concepts such as taxi path, hold-short 

locations, and surface trafc with those of the in-fight display concepts such as tunnel, terrain, 

and obstacles. Detection of runway incursion events and subsequent alerting became an important 

add-on capability of the original LVLASO display suite. 

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Key researchers during the LVLASO project were Wayne H. Bryant (Project Manager), Steven 

D. Young, Denise R. Jones, Richard Hueschen, Dave Eckhardt, Dave Foyle, Rob McCann, 

and Tony Andre. 

SVS Operational Concept Development 

Langley research on crew-centered display concepts for synthetic vision systems includes activities 

to defne concepts (tactical and strategic); retroft analog systems; forward-ft (includes advanced 

display media); display information content, media, and format; operator interfaces; and simulation 

and fight evaluations. Te display research is coupled with research on operational concepts, 

requirements, and integration. Critical elements in operational research include operations and 

requirements, procedures defnition, operational enhancements, reversionary mode assessments, 

interface with the air trafc system, certifcation strategy, and operational benefts assessment. 

Finally, supporting research in crew response evaluation methodologies contributes information on 

situation awareness measurement techniques, crew performance assessments, and the application 

of measurement techniques in simulation and fight evaluations. 

Key Langley research areas and lead individuals include: terrain database rendering (Trey Arthur 

and Steve Williams); pathway concepts (Russ Parrish, Lawrence J. Prinzel, III, Lynda Kramer, and 

Trey Arthur); runway incursion prevention systems (Denise R. Jones and Steven D. Young); CFIT 

avoidance using SVS (Trey Arthur); loss of control avoidance using SVS (Douglas T. Wong and 

Mohammad A. Takallu); database integrity (Steven D. Young); SVS sensors development (Steve 

Harrah); and SVS database development (Robert A. Kudlinski and Delwin R. Croom, Jr.). 

Enabling Technologies for SVS 

For the SVS concept to reach its fullest potential, several enabling technology developments 

are required. A large portion of the SVS project focused on concern over the availability and 

quality of terrain, obstacle, and airport databases. Tese issues were addressed through large-scale 

assessments, acquisitions, and development of representative prototypes. International standards 

were developed and published that established requirements for content, quality, and exchange. 

Sensor research, including FLIR and X-band radar, addressed integrity concerns by implementing 

data fusion, feature extraction, and monitoring techniques. Hazard detection algorithms were 

developed to address the runway incursion, runway alignment, and obstacle avoidance issues. Key 

researchers on the SVS team were Rob Kudlinski (lead), Steven D. Young, Denise R. Jones, Steve 

Harrah, and Delwin Croom, Jr. 

104 Innovation in Flight 
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Researchers Lynda Kramer (left) and Denise Jones conduct SVS study. 

Partnerships 

In addition to extensive in-house research, Langley is engaged in several partnerships and cooperative 

activities to develop synthetic vision systems. For commercial and business aircraft applications, 

an agreement partnership exists for a synthetic vision information systems implementation team 

led by Rockwell Collins, Inc., of Cedar Rapids, Iowa, with members from Jeppesen, Te Boeing 

Company, American Airlines, Delft University of Technology, Embry-Riddle Aeronautical 

University, and Flight Dynamics, Inc. Another partnership on future fight deck information 

management and display systems is led by BAE Systems, Inc., CNI Division, Wayne, New Jersey, 

with members from BAE Systems Canada, Inc., and BAE Systems Astronics Company. 

Enabling technology research was accomplished in large part through three cooperative research 

agreements. Database issues were addressed by a team led by Jeppesen and included members from 

American Airlines, the Technical University of Darmstadt, and Intermap Technologies Corporation. 

Runway incursion detection schemes were developed and tested by Rannoch Corporation. Lastly, 

Ohio University’s Avionics Engineering Center contributed signifcant research results with respect 

to database integrity monitoring. 

Specifc research eforts are also directed at general aviation community needs where weatherinduced loss of situational awareness has traditionally led to fatal accidents. In this area, Langley 

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partners with an afordable, certifable low end thrust synthetic vision system team led by AvroTec, 

Inc., Portland, Oregon, with members from B.F. Goodrich, Elite Software, Lancair/PAC USA, 

Massachusetts Institute of Technology, Raytheon Aircraft, Seagull Technologies, Inc., and 

FAA Civil Aerospace Medical Institute. In addition, a low cost synthetic vision display system 

capability for general aviation team is led by Research Triangle Institute, Research Triangle Park, 

North Carolina, with members from Archangel Systems, Inc., Flight International, Inc., Seagull 

Technologies, Inc., Dubbs & Severino, Inc., and FLIR Systems, Inc. Finally, a low-cost attitude and 

heading reference system (AHRS) to enable synthetic vision team is led by Seagull Technology, Inc., 

Los Gatos, California, with members from Dynamatt, BARTA, S-Tec Unmanned Technologies, 

Inc., Reichel Technology, Rockwell Collins, Inc., Stanford University, and Raytheon Aircraft. 

Flight Demonstrations of SVS Technology 

Troughout the SVS project’s 5-year term, the rapidly advancing state of synthetic vision technology 

has been demonstrated by NASA in high-profle events with extensive participation by other 

government agencies, industry, airlines, and airport ofcials. Since 1999, the fight demonstrations 

have shown an increasingly sophisticated SVS capability with obvious benefts to piloting tasks 

and attendant safety in low-visibility conditions. Te scope of the demonstrations has included 

airborne as well as ground operations designed to show the potential of SVS to minimize or 

eliminate CFIT and runway incursion accidents. 

Asheville, North Carolina 

As part of the AvSP, initial SVS fight eforts used the TIFS, a highly modifed propeller-driven 

Convair 580 built in the 1950s and transformed into a fying simulator in the early 1970s. Te 

TIFS aircraft is outftted with two cockpits: a conventional safety cockpit that is always available to 

fy the plane and a forward research cockpit that is used to test advanced concepts. Te simulation 

cockpit is equipped with special instruments and displays. Operated by the Veridian Corporation, 

the TIFS vehicle was confgured to simulate fight characteristics of a representative high-speed 

civil transport for SVS fight research at Asheville, North Carolina, in 1999. In a demonstration 

of photorealistic synthetic vision, Langley researchers used an experimental terrain database of 

the Asheville Regional Airport that had been augmented by sophisticated computer rendering 

techniques. Te use of photorealistic versus generic terrain texturing provided the researchers with 

an early look at display size and feld of view issues. 

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Te Total In-Flight Simulator research airplane during NASA fights 

at Asheville, North Carolina. 

Display implementation for Asheville research fights 

Te Asheville demonstration was led by Langley’s Russ Parrish, Lynda Kramer, Lou Glabb, and 

Veridian’s Randy Bailey (who would later become a Langley researcher and join the SVS team), 

and it included the participation of Veridian, Boeing, Honeywell, the Research Triangle Institute, 

and various airlines. During October and November 1999, three evaluation pilots few over 60 

approaches, including three to fnal touchdown. Pilot comments on Asheville Regional Airport’s 

nested database with photorealistic overlay were very favorable. Te state-of-the-art terrain, obstacle, 

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and airport databases worked extremely well in actual fight. Pilots said that tactical control of the 

aircraft using synthetic vision was intuitive and characterized by low workloads. NASA researchers 

gathered information data on transitioning from lower to higher resolution nested databases, as 

well as grid size requirements. Tey also assessed photorealistic terrain texture overlays compared 

with computer-generated terrain texture overlays. 

Pilot comments during the demonstration were very impressive. Te display’s realism and the 

obvious impact on fights in low-visibility conditions during airline-type operations were cited as 

monumental contributions with tremendous potential for enhanced safety. 

Armed with these very exciting early results, Langley researchers continued the pursuit of additional 

challenges and barriers, including SVS retroft issues and technical questions, such as head-down 

display size and feld-of-view requirements head-up opaque display concepts, terrain texturing 

issues, generic versus photorealistic views, and database integrity. 

Dallas-Fort Worth International Airport, Texas 

During September and October 2000, Langley researchers and their cooperative research 

partners—Rockwell-Collins, Rannoch, the FAA’s Runway Incursion Reduction Program, 

Jeppesen, Ohio University, and the Dallas-Fort Worth Airport Authority—conducted an extensive 

fight demonstration/evaluation of synthetic vision at the Dallas-Fort Worth (DFW) International 

Airport. In this series of demonstrations, the Langley team used the Langley Boeing 757-200 

Airborne Research Integrated Experiments System (ARIES) research aircraft with SVS displays. 

Te DFW demonstration was planned as part of the previously discussed NASA LVLASO project 

that was slated to end with this specifc demonstration, culminating 7 years of Langley research 

on surface display concepts and systems for low visibility ground operations. Te demonstration 

included an assessment of a Runway Incursion Prevention System (RIPS). A government study 

predicts runway collisions will be the single largest cause of aviation fatalities over the next 20 

years unless something is done, and near misses on runways are up sharply in recent years. In 

one tragic example in 1991, 34 people died at Los Angeles International Airport during a runway 

incursion accident. 

Langley’s RIPS integrates several advanced technologies into a surface communication, navigation, 

and surveillance system for fight crews and air trafc controllers. RIPS combines a head-down 

cockpit display of an electronic moving map of airport runways and taxiways with a head-up 

display that gives the pilot real-time guidance. 

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In-fight SVS concepts were also included in the evaluation so that they could be assessed in a 

busy terminal environment. Te in-fight SVS testing was decoupled from the RIPS testing; that 

is, both components of what would later be the integrated Langley SVS were tested and evaluated 

separately at DFW. Six pilots few 76 landing approaches to evaluate the SVS concept, including 

about 18 research fight hours. RIPS was fown and assessed by four evaluation pilots. One of 

the other key investigations of this activity was an evaluation of a Langley opaque HUD concept 

during night operations. 

Langley’s B757 ARIES research aircraft at Dallas-Fort Worth 

International Airport. 

Night scene during practice fights for Dallas-Fort Worth showing SVS display and out-thewindow runway lights. 

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Te evaluation pilots provided extremely favorable comments, including observations that synthetic 

vision appeared to be viable and efective, situational awareness was enhanced, and pilots liked the 

immersive feel of the HUD. 

Two incursion events were emulated at DFW. For the frst runway incursion event, the ARIES 

pulled onto an active runway upon which another aircraft (simulated by an FAA van) was landing. 

In another scenario, the ARIES performed a coupled instrument approach while trafc (the FAA 

van) proceeded across the hold-short line crossing the active runway. Tese emulated incursions 

demonstrated the efectiveness of RIPS. 

Runway incursion prevention displays. 

Key researchers for the DFW demonstrations included Lou Glaab, Denise Jones, Richard Hueschen, 

Lynda Kramer, Trey Arthur, Steve Harrah and Russ Parrish, as well as Langley research pilots 

Harry A. Verstynen and Phillip Brown. 

Eagle County Regional Airport, Colorado 

In August and September of 2001, Langley and its partners provided demonstration fights of SVS 

for the third time in 3 years to NASA, airline, FAA, and Boeing pilots at the Eagle County Regional 

Airport near Vail, Colorado. Led by Randy Bailey, the project team’s objective was to demonstrate 

SVS in an operationally realistic, terrain-challenged environment. Vail-Eagle is nestled in a valley 

with mountains close to the runway on three sides. Runway incursion prevention systems were not 

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evaluated in this project. Te vision of operational SVS concepts had matured to database-derived 

systems using precise GPS navigation and integrity monitoring sensors to provide an unrestricted 

synthetic view of the aircraft’s current external environment, regardless of weather or time of day. 

Te Langley ARIES B757 research airplane was again used for the demonstration, which was fown 

by seven evaluation pilots for 11 research fights that included a total of 106 airport approaches. 

Specialized systems on the 757 aircraft included dedicated SVS pallets, special SVS display panels, 

a HUD, vision restriction capability for simulated instrument conditions, and an 18.1-in. (1280 

Langley’s ARIES B757 research airplane during fight at Vail-Eagle airport. 

Head-up and head-down displays used during demonstration fights. 

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by 1024) fat panel display. Subject pilots included current B757 captains from American Airlines, 

United Airlines, Delta Airlines, FAA, Boeing, and NASA. Te pilots were provided prefight 

training in Langley’s simulators before the demonstration. 

During the fights at Vail-Eagle, the evaluation pilots provided comments on two diferent HUD 

concepts and four diferent head-down concepts developed by NASA and Rockwell Collins. Te 

pilots provided comments on the relative efectiveness of display sizes, felds of view, and computer 

graphic options. 

In addition, EVS applications were investigated, both as a sensor for gathering images of the 

runway environment and as a database integrity monitor. Likewise, multiple radar altimeters and 

diferential GPS receivers gathered height-above-terrain truth data for database integrity monitoring 

algorithm development. 

Key Langley researchers included Principal Investigator Randy Bailey, Russ Parrish, Dan 

Williams, Lynda Kramer, Trey Arthur, Steve Harrah, Steve Young, Rob Kudlinski, Del Croom, 

and pilots Harry Verstynen and Leslie O. Kagey, III. Boeing, Jeppesen and Rockwell Collins, and 

Ohio University joined Langley as part of the synthetic vision project team. Approximately 70 

representatives from the FAA, DoD, and the aviation industry participated in prefight briefngs 

and in-fight demonstrations of SVS display concepts. 

One impressive demonstration of the capabilities provided by SVS came during “circle-to-land” 

approaches on Vail-Eagle’s runway 7. Commercial pilots get special training to land at mountain 

airports like Vail-Eagle, but until the NASA tests, pilots had never made the circle-to-land, which 

puts the jet very close to the surrounding terrain under instrument fight conditions. Published 

navigational charts require that the landing be fown with a visual approach. Te technology 

provided by Langley and its partners worked fawlessly during the unprecedented approaches. 

Reno-Tahoe International Airport, Nevada 

In July 2004, Langley’s consortium of government, industry, and university partners culminated 

an impressive 5-year demonstration of accelerated technologies for prototype SVS concepts with 

an in-depth series of fight tests at the Reno-Tahoe International Airport. Te demonstration 

integrated a number of SVS elements to highlight the benefts to pilots in both airborne and ground 

operations in low visibility conditions. Dan Baize’s team of government and industry participants 

used a GV business jet and a variety of Langley- and Rockwell Collins-derived SVS concepts that 

left indelible impressions on evaluation pilots for potential enhancement of fight safety. Using the 

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Details of the synthetic vision system display used in the demonstration fights. 

Gulfstream V airplane used in demonstration fights at Reno International Airport. 

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GV was especially noteworthy because the aircraft was equipped with a production option known 

as the Gulfstream enhanced vision system, which uses a nose-mounted forward-looking infrared 

sensor to provide information depicted in terrain displays on a cockpit HUD panel and an HDD 

fat panel display, both of which provide symbology and fight path information. As of 2004, over 

80 units of this concept had been produced for Gulfstream customers. 

Langley’s Randy Bailey led the project, while Denise Jones was Principal Investigator for the runway 

incursion technology, Lynda Kramer and Trey Arthur led the SVS display development, Steve 

Young and Del Croom led the data integrity eforts, and Steve Harrah led sensors-related eforts. 

Industry participants included Rockwell-Collins, Gulfstream, Northrop Grumman, Rannoch 

Corporation, and Jeppesen, and Ohio University participation in the area of data integrity. 

Two diferent runway incursion prevention systems developed by NASA/Lockheed Martin and 

Rannoch Corporation, respectively, were evaluated. A dramatic demonstration of the NASALockheed Martin concept’s efectiveness involved a simulated potential collision with the team 

using a NASA aircraft acting as an intruder by accelerating on an intersecting runway during a GV 

takeof. With unmistakable visual and aural cues, the RIPS quickly identifed the situation and 

prompted the pilot for immediate action (in this case, deploying brakes and engine thrust reversers 

to stop the Gulfstream test vehicle). 

Langley’s SVS terrain and guidance displays used in the demonstration were intentionally conceived 

to be futuristic in terms of guidance displays, pathway-in-the-sky details, and terrain detail. As 

part of the SVS demonstration team, Rockwell Collins provided its version of a more near-term 

SVS/EVS display concept, highlighting the accelerated development that has occurred in synthetic 

vision capability and the potential for certifcation and widespread applications of the technology 

in the near future. 

Terrain database integrity monitoring was also demonstrated during the Reno fights. In this 

element of the NASA program, Langley teamed with Ohio University and Rockwell Collins to 

use sensors—such as a radar altimeter, advanced weather radar, and forward-looking infrared 

information—to cross check the accuracy of the digital SVS database in real time during fight. 

Te pilot was alerted if questionable data were detected during the correlation of sensor and digital 

information, and erroneous data were deleted from the displays. During the demonstration fights, 

the GV’s standard infrared-based “all-weather window” produced by Kollsman, Inc., provided 

thermal imagery of features such as runway lights and terrain for cross checking of digital 

SVS data. 

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View of the synthetic vision system head-up and head-down displays (left) 

and the standard Gulfstream V display (right). 

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Details of synthetic vision system display evaluated in Reno tests. 

Runway incursion prevention display. 

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Simulated runway incursion by NASA King Air airplane (left) during Reno evaluations of 

incursion prevention systems on Gulfstream V airplane (right). Note the deployed engine thrust reverser doors on the 

Gulfstream V as the pilot takes corrective actions to avoid the potential collision. 

Te integrated SVS concept also included a voice recognition system for display control. Insensitive 

to individual voice or accent characteristics, the system proved to be extremely reliable during the 

fight demonstrations. 

All evaluation pilots who assessed the SVS technology at Reno were extremely positive and 

enthusiastic over the capability of this revolutionary technology. Te system’s potential to ease 

pilot workload and provide a signifcant improvement in safety during low-visibility airborne and 

ground operations was readily apparent and appreciated by all participants. 

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General Aviation Activities and Flight Demonstrations 

Langley researchers are also addressing technological and operational challenges facing the 

implementation of synthetic vision systems within the general aviation community. Low-visibility 

accidents are especially prevalent among inexperienced pilots. General aviation aircraft comprise 

about 85 percent of the total number of civil aircraft in the United States. In a recent NTSB 

accident database, general aviation accounted for 85 percent of all accidents and 65 percent of 

all fatalities. Te combination of night and instrument fying increased the proportion of fatal to 

total accidents to 64.3 percent, making low-visibility conditions the most deadly general aviation 

fight environment. 

Working with the FAA, industry, universities, and the general aviation pilot community, Langley 

is conducting extensive simulator and fight test evaluations to assess and demonstrate the benefts 

of SVS technology compared with current general aviation systems. As previously mentioned, 

the constraints on technical concepts directed toward the general aviation sector are unique, 

including low cost, no sensors, no HUD applications, and use of existing strategic terrain displays. 

Dominant in these considerations is the tremendous degree of variability in pilot background 

and capabilities. 

Lead researchers for Langley’s general aviation element of the SVS project include Louis J. Glaab 

and Monica F. Hughes. Initially, their team of researchers conducted piloted simulator studies 

using a generic general aviation workstation equipped with variants of SVS characteristics, such as 

terrain features and guidance information. Following the fundamental simulator studies, the more 

promising displays were incorporated in actual fight evaluations at two Virginia airports. 

Flight Demonstration of Head-Down Displays 

Glaab and Hughes conceived and conducted a series of fight evaluations to attack technical questions 

regarding terrain presentation realism and the resulting enhancements of pilot situational awareness 

and performance. Comprising coordinated simulation and fight test eforts, terrain portrayal for 

the head-down display (TP-HDD) test series examined the efects of digital resolution and terrain 

texturing. Te TP-HDD test series was designed to provide comprehensive data to enable design 

trades to optimize all SVS applications, as well as develop requirements and recommendations to 

facilitate the implementation and certifcation of SVS displays. Te TP-HDD fight experiment 

used the Langley Cessna 206 research aircraft and evaluated eight terrain portrayal concepts in an 

efort to confrm and extend results from a previously conducted TP-HDD simulation experiment. 

Fifteen evaluation pilots, of various qualifcations, accumulated over 75 hours of dedicated research 

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Langley’s Cessna 206 research airplane. 

fight time at the Newport News-Williamsburg International and Roanoke Regional airports in 

Virginia from August through October, 2002. 

Overall, a comprehensive evaluation of specifc components of SVS terrain portrayal methods 

was conducted through an extensive simulation and fight-test efort. Project results indicated 

pilots were able to use SVS displays efectively with dramatically increased terrain awareness. In 

general, all SVS concepts tested provided results that correlated with other data produced by nonNASA researchers, suggesting that ultimate terrain portrayal fdelity (photorealism) might not be 

as important as efective terrain portrayal presentation (elevation-based generic). 

Te FAA’s Alaskan Region Capstone Program 

Langley has traditionally maintained a close partnership with the FAA and other government 

agencies in its aeronautical research and development activities, and this legacy has been maintained 

in the SVS project element for general aviation. In addition to frequent communication and 

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partnership activities with the FAA, Langley has hosted two separate workshops, in 2002 and 

2004, to ensure real-time transfer of its technology and to receive guidance and comments from 

appropriate FAA ofces regarding future research. 

An important FAA activity involving Langley participation has been the Alaskan Region Capstone 

Program. Capstone is an accelerated FAA efort to improve aviation safety in Alaska. No state 

relies as heavily upon aviation as Alaska does to provide many of life’s bare essentials, yet Alaska 

ranks at or near the bottom in U.S. aviation safety because of its terrain, climate, and lack of such 

infrastructure as weather observation stations, communications, and radar coverage below 10,000 

ft, where most general aviation and commercial carrier aircraft fy. Te Capstone program was 

created to address Alaska’s high accident rate for small aircraft (those weighing 12,500 lbs or less). 

Tese accidents occur at nearly fve times the national average. Plans call for up to 200 aircraft to 

be voluntarily equipped with Capstone avionics. Te program includes the installation of ground 

infrastructure, GPS-based avionics, and data link communications in commercial aircraft serving 

the Yukon-Kuskokwim Delta/Bethel area. 

Te Capstone Program equips over 150 aircraft used by commercial operators in Alaska with a 

combined data link and GPS-based avionics package designed to increase the situational awareness 

of pilots in averting mid-air collisions and CFIT accidents. 

In 2001, the FAA released a Request for Proposal (RFP) for a Capstone phase II activity that 

would incorporate technologies matured in phase I, build on lessons learned, and explore other 

risk-mitigating technologies to reduce accidents and fatalities in the Southeast area of Alaska. 

Te project would include technical elements representative of SVS concepts, such as the frst 

certifcation of HITS technology for navigational guidance, use of forward-looking threedimensional terrain, adjustable feld of view on primary fight displays, and use of conformal 

perspective runway presentation and conformal obstructions on primary fight displays. In April 

2002, Chelton Flight Systems of Boise, Idaho, received the phase II award for this revolutionary 

project. In March, 2003, Chelton Flight Systems received the frst FAA approval for synthetic 

vision, highway-in-the-sky technology. Chelton’s system incorporates synthetic vision, a fight path 

marker, and HITS technology, providing a three-dimensional series of boxes along the fight path 

from takeof to touchdown. Selected for the FAA’s Capstone Program, the certifcation of this 

technology was a groundbreaking partnership between industry and a progressive FAA. 

Langley participated in the development of the RFP for Capstone II, including membership on the 

technical evaluation board. As part of the TP-HDD simulation experiment, the lead certifcation 

pilot for the FAA Capstone-II efort, as well as three potential Capstone-II equipment users from 

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Juneau, Alaska, participated in the TP-HDD data generation process as subject pilots. Due to this 

participation and extensive discussions during the previously mentioned workshops, Langley was 

able to efectively direct its research toward FAA-requested certifcation issues. 

Status and Outlook 

Research conducted to date on SVS addresses low-visibility-induced incidents and accidents 

with a visibility solution, making it possible for every fight to be nearly equivalent to clear-day 

operations. Te key remaining challenges to actual commercial use appear to be: (1) certifcation 

and systems engineering, that is, how to map SVS functions to certifed avionics and prove failsafe operations; (2) operational approval for fight-critical uses, or how to prove that pilots can 

trust the system when fying close to the ground in low visibility; (3) efective crew procedures 

and interfaces; and (4) justifying investment in new technology in today’s economic environment. 

Safety improvements are rarely implemented without operational benefts unless mandated. SVS 

may provide operational benefts by enabling lower landing minima and/or landing at unequipped 

runways and airports. Technical challenges such as database integrity and avoidance of hazardously 

misleading information also remain major concerns. 

NASA strives to work cooperatively with the FAA, academia, and industry to ensure successful 

implementation of SVS. A large number of commercialization eforts are underway to bring the 

SVS concept to reality; certifcation is being pursued, and it is expected that the technology will 

be routinely used in commercial and general aviation in the near future. 

Langley’s SVS project is scheduled to end in 2005, completing an exceptionally productive program 

that has helped push this remarkable technology to the forefront of aviation. At this time, almost 

every general aviation manufacturer has a synthetic vision concept in its design pipeline for nearterm application. Te Gulfstream EVS system has set the mark for applications to business jets, 

and Chelton’s FlightLogicTM system is leading the way for SVS. 

Research conducted by Langley Research Center and its partners has had a profound efect on the 

state of the art in synthetic vision cockpit displays. Te highly professional eforts contributed by 

Langley on fundamental pilot-display technology, enabling avionics technologies, computational 

requirements and methodology, and interactive demonstrations to the aviation community have 

greatly accelerated the implementation, database development, and confdence level required to 

pursue the certifcation and application of SVS. NASA has concentrated on futuristic systems and 

operations, becoming leaders in technology beyond that which is emerging today. Te partnerships 

between Langley and industry have been especially productive, continuing a long Langley legacy 

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of success in such arrangements. In addition, the accumulated expertise and experience of the 

Langley staf represents a national asset that is being applied to the solution of visibility-related 

safety issues for the U.S. aviation feet for years to come. 

122 Innovation in Flight 
Laminar-Flow Control: The Holy Grail of Aerodynamics 

Concept and Benefts 

When an aircraft fies through the atmosphere, the efects of viscosity cause frictional forces as the 

fow in a thin layer of air next to the aircraft surface—known as the boundary layer—decelerates 

relative to the aircraft’s speed. Tese frictional forces generate a signifcant amount of aerodynamic 

drag for all classes of aircraft. Tis drag, referred to as skin-friction drag, has a large efect on 

the amount of fuel consumed by most aircraft during cruise. For example, at subsonic cruise 

conditions, the skin-friction drag of a conventional subsonic transport accounts for about one-half 

the fuel required for fight, and, for a future supersonic transport, skin-friction drag could account 

for about one-third the fuel burned at cruise conditions. Very complex fuid dynamic interactions 

that occur within the boundary layer determine the specifc level of skin-friction drag experienced 

by an aircraft. Tree distinct types of boundary-layer fow states may occur: laminar, transitional, 

and turbulent. In the case of laminar boundary-layer fow, the fuid near the surface moves in 

smooth-fowing layers called laminae. 

Te sketch shows a representation of boundary-layer conditions (greatly magnifed) resulting from 

Efect of airfoil surface condition on boundary-layer fow. 

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air moving over an airfoil from left to right. For ideal conditions, the fow would follow the curved 

airfoil surface smoothly, in laminae. Unfortunately, for most full-scale aircraft fight conditions 

of interest, the thin boundary layer enters a state of transition wherein the adjacent layers of fow 

begin to intermix and destroy the desirable laminar condition. Following transition, the boundary 

layer is completely turbulent and laminar-fow features are completely lost. In turbulent fow, 

secondary random motions are superimposed on the principal fow within the thin boundary 

layer, such that slow-moving fuid particles speed up, and fast-moving particles give up momentum 

to the slower moving particles and slow down. Te friction force between air and moving body 

dramatically increases when the boundary-layer fow changes from a laminar state to the turbulent 

condition. Te reader is cautioned that the change from a laminar to a turbulent condition does 

not result in fow separation from the airfoil surface (as in a stalled condition). Te eddies and 

turbulence shown in the sketch serve only to emphasize the chaotic nature of the turbulent fow 

within the thin boundary layer, which may extend from just a few fractions of an inch to inches 

above the surface. 

Mechanisms causing boundary-layer fow change from laminar to turbulent are very complex 

depending on a considered airplane component’s specifc geometry (sweep, thickness, etc.), surface 

disturbances (gaps, bumps, etc.), the speed of fight (the boundary layer is thinner at high speeds), 

the relative viscosity of the air, and many other fow variables, such as pressure gradients. Te efect 

of surface roughness is depicted in the lower sketch, which shows that roughness imparts sufcient 

disturbances to the boundary layer to cause premature transition at a point farther forward on the 

airfoil, thereby increasing the turbulent region. Another fundamental factor in the transition from 

laminar to turbulent fow is the pressure gradient in the fow feld. If the static pressure encountered 

by the fow increases with downstream distance, disturbances in a laminar fow will tend to be 

amplifed and turbulent fow will result. If the static pressure decreases with downstream distance, 

disturbances in a laminar fow will damp out and the fow will tend to remain laminar. 

In 1883, scientist Osborne Reynolds introduced a dimensionless parameter giving a quantitative 

comparison of the viscous and inertial fow states. Reynolds’ parameter, which is known as the 

Reynolds number, has been used by the engineering community to gauge relative probability of 

the existence of laminar or turbulent fow, and it is a dominant variable in aerodynamic design. 

Documents cited in the bibliography give details regarding the physical variables included in the 

Reynolds number parameter and its use in aeronautical studies. For background of the nontechnical 

reader, low Reynolds number fows are usually laminar and high Reynolds number fows (typical 

of large commercial transports at cruise conditions) are mostly turbulent. 

124 Innovation in Flight 
LAMINAR-FLOW CONTROL: THE HOLY GRAIL OF AERODYNAMICS 

Laminar fow obtained by airfoil shaping in the natural laminar fow concept (left) and active suction fow 

control in the laminar fow control concept (right). 

Te hybrid laminar fow control concept. 

Successful analysis, prediction, and control of the boundary-layer transition process for improved 

aerodynamic efciency has been the ultimate goal—the Holy Grail—of aerodynamicists since 

the earliest days of aviation. For some confgurations with relatively small-chord unswept wings, 

designers have used shaping of the wing airfoil to promote favorable pressure gradients that, together 

with smooth composite wing structures, and, in some cases, high-altitude fight (low Reynolds 

number), result in extensive laminar fow. Examples include high-performance gliders and the 

military U-2 reconnaissance aircraft. In this passive manner, laminar fow is obtained in what is 

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referred to as natural laminar fow (NLF). A previous book by the author, NASA SP-2003-4529, 

Concept to Reality, discusses Langley Research Center’s past contributions to NLF technology and 

applications by industry. For larger aircraft, which cruise at relatively high subsonic speeds and are 

subject to surface irregularities, the principles of NLF do not normally result in appreciable laminar 

fow. As a result, researchers have turned their interests to laminar fow control (LFC) concepts 

that use artifcial (active) mechanisms to delay or possibly eliminate the existence of turbulent 

fow over a large region (perhaps even full-chord length) of the wing. Two approaches to actively 

prolonging laminar fow are surface cooling and removing a small portion of the boundary-layer 

air by suction through slots or porous surfaces. 

LFC concepts for aircraft applications from the late 1930s to the late 1980s focused on suction 

concepts, most of which used full-chord deployment of suction to encourage full-chord laminar 

fow. Unfortunately, LFC is a mechanically complex concept involving auxiliary power sources 

or engine bleed air for suction, extensive ductwork throughout the wing internal structure, and 

weight and maintenance penalties. However, in the late 1980s application studies were instituted 

by NASA and industry on the practical combination of LFC and NLF, a concept known as 

hybrid laminar fow control (HLFC). HLFC combines some features of both NLF and LFC to 

promote laminar fow for medium-sized transports in a manner that reduces the level of suction 

requirements and mechanical system complexity previously encountered with LFC. With HLFC, 

the wing geometry is tailored to provide favorable pressure gradients (per NLF), and suction is only 

applied in the leading-edge region back to the front wing spar (about 15 percent of the local chord 

length) to alleviate some adverse efects due to wing sweep. 

Next to labor costs, jet fuel is the second largest operating cost for an airline. For an international 

airline in 2004, jet fuel usually made up roughly 10 to 15 percent of its total cash operating costs. 

For a regional carrier, fuel costs can be up to 25 percent of its operating costs. Te diference is 

mainly due to the higher labor rates and newer, more fuel-efcient planes of the major carriers. 

At a consumption rate of 18 billion gallons per year, the Air Transport Association estimates that 

each 1-cent rise in fuel prices increases the industry’s annual expenses by $180 million. Jet fuel 

price increases have consisted of large excursions that can abruptly occur over short time periods 

of months. For example, the average monthly cost of domestic jet fuel from January 1999 through 

July 2000 rose from a low of 43.8 cents per gallon to a high of 77.8 cents per gallon, a 78-percent 

increase. In early 2005 the rise of crude oil prices to over $55 per barrel caused fnancial chaos 

throughout the U.S. air and ground transportation systems. 

Aerodynamic performance predictions by researchers indicate that LFC might decrease the fuel 

burned on long-range fights for transport-type aircraft by a phenomenal 30 percent. By reducing 

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the amount of fuel burned, LFC would also reduce emissions and pollution caused by aircraft. 

Although the aerodynamic performance improvements of HLFC are not as great as LFC, the 

potential gains are substantial (up to about 15-percent reduction in fuel burned) and represent 

a signifcant beneft for cash-strapped airlines. Of course, the benefts of LFC and HLFC will 

be largest for fuel-intensive long-range missions rather than short routes. Studies also indicate 

that applications of LFC and HLFC at initial design phases of a new aircraft (versus retroft 

applications to existing aircraft) may allow the airplane to be resized for weight reduction, smaller 

engines, and other benefts. For years the domestic and international aviation communities have 

widely recognized the benefts of LFC and the technology is currently being pursued for potential 

applications to civil and military aircraft. 

Challenges and Barriers 

Requirements for aircraft performance, economic viability, operational suitability, and safety must 

be addressed and demonstrated before active laminar fow concepts, such as LFC and HLFC, can 

be applied to operational aircraft. Obviously, technology maturation is required to a relatively 

high level, including demonstrations with actual aircraft. Te following discussion highlights 

issues and concerns that surfaced early during research on LFC. NASA in-house, contracted, and 

cooperative research has addressed virtually all of these early concerns, but this section discusses 

these issues here to provide the reader with an appreciation of the breadth of research provided by 

NASA to solve potential problems and barriers to LFC and HLFC. 

Disciplinary Challenges 

Aerodynamicists face fundamental challenges in LFC technology. Developing reliable design 

methods that accurately predict characteristics of the inherently unstable boundary layer as afected 

by a myriad of aircraft and atmospheric parameters such as geometry, sweep, pressure gradients, 

surface conditions, suction levels and distribution, and Reynolds number is formidable. Inherent 

to the task is a full understanding of the physics and processes associated with the laminar to 

turbulent boundary-layer transition process. 

Aerodynamicists must master transition mechanisms related to spanwise crossfows, eddies, and 

critical waves within the boundary-layer fow, and other aerodynamic phenomena that promote 

or inhibit transition. Tey must also develop and validate predictive tools for design. Within 

this efort, the transition-inducing efects of surface roughness, waviness, steps, and gaps must 

be determined and tolerances defned for manufacturing. Aerodynamic advantages of slotted, 

porous, and perforated suction distribution concepts must be evaluated and demonstrated. 

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Concerns and issues addressed by laminar-fow technology. 

Aircraft systems engineers must analyze the impact of losing laminar fow through mechanical or 

other causes, and acceptable of-design characteristics must be ensured. Aerodynamic issues also 

cause designers to assess the compatibility of laminar-fow concepts with conventional solutions 

to other aerodynamic considerations. For example, designers sometimes use vortex generators to 

inhibit wing fow separation for satisfactory high-speed control and bufet characteristics, but this 

approach would not be compatible with laminarization of wing surfaces. Management also wants 

to see if LFC- and HLFC-type systems can provide synergistic benefts that help such a concept 

“buy its way” onto the aircraft. 

Issues relating to manufacturing materials with precise, economically feasible features for suction 

are especially critical. Te layout, dimensions, and drilling of suction holes in wings, fuselages, 

tails, or nacelle structures are potential barrier problems that must be demonstrated with full-scale, 

production-type tooling and hardware. 

Integrated System Challenges 

Designers must also address aircraft system-level challenges for LFC and HLFC, including 

considerations of power systems for the suction system. Auxiliary pumps or other devices must 

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have acceptable capacity, weight, maintainability, and economic feasibility. If engine bleed air 

is required, the level of bleed must not result in serious increases in the aircraft’s specifc fuel 

consumption. Assessments of ducting concepts and analysis of distributed suction levels are required 

to ensure adequate suction levels compatible with the physical constraints of wing structure and 

plumbing. Total weight of the LFC or HLFC system is usually of relatively little concern for 

systems envisioned, but maintenance, complexity, manufacturing feasibility, cost, and reliability 

are critical issues, as well as compatibility with other mechanisms located in or on the aircraft 

wing, such as leading-edge high-lift devices and deicing systems. 

Operational Challenges 

Researchers have focused on the most obvious barrier problem to laminar fow: environmental 

contamination of the sensitive wing leading-edge region caused by insects, rain, ice, or other 

debris. Concepts to minimize the efects of environmental contamination must be compatible 

with aircraft takeof and landing performance, cruise performance, routine fight operations, other 

fight systems, and maintenance requirements. Using shielding concepts to protect the leading 

edge from insect debris during takeof must be efective, not degrade the high-lift aerodynamic 

performance of the airplane, and either provide or be compatible with deicing capability. In-fight 

issues, such as the efect of encountering ice crystals during fight in clouds, must be addressed 

and demonstrated with actual airplane fight tests. Maintenance issues require assessments of the 

impact of freezing rain on suction ports and systems and of the reliability and upkeep of suction 

pumps and auxiliary systems. Finally, the consequences of system failures in terms of performance, 

mission capability (range), safety, and cost implications must be thoroughly researched. 

Economic Challenges 

Modern airlines are doing everything they can to conserve fuel. Troughout the history of 

commercial aviation, airlines have insisted on the most fuel-efcient aircraft possible and have 

worked with airframe and engine manufacturers to reduce fuel consumption. Today’s commercial 

transport feet is much more fuel-efcient than the feet that was in operation at the time of the 

frst Organization of Petroleum Exporting Countries (OPEC) fuel crisis in the 1970s. Changes 

in cruise speed, sophisticated fight planning systems, lighter composite structures, and the 

introduction of improved aerodynamic aircraft designs and advanced engine technology are all 

examples of fuel-saving technology. With paper-thin proft margins and a reluctance to invest 

in new technology or aircraft in the turbulent commercial marketplace of the new millennium, 

airlines will carefully examine all cost-beneft aspects of LFC. Te lack of technical confdence in 

LFC or HLFC, coupled with the need for long-term, in-service experience in worldwide, all-weather 

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conditions with such systems, has resulted in a standof between the potentially catastrophic efects 

of rising fuel costs on the airline industry and the economic unknowns of unproven technology. 

Tis situation is somewhat analogous to that of the 1950s when a highly competitive industry 

ventured into commercial jet transport development. Tanks to the injection of new technology, a 

new era of aeronautics was opened and the risk takers fourished. 

Langley Activities 

Laminar-Flow Technology 

Te scope of in-house and contracted research by Langley on laminar fow technology is a rich 

legacy of signifcant Center contributions. Many outstanding technical reports, professional journal 

articles, formal presentations, and other media publications have ensured the dissemination of 

this important research to users of the technology as well as to the public. Te bibliography lists 

many of these documents. Te reader is especially referred to two superb resources that provide 

extensive coverage of the activities and contributions of Langley Research Center in this area. 

Albert L. Braslow’s publication, NASA Monographs in Aerospace History No. 13, A History of 

Suction-Type Laminar-Flow Control with Emphasis on Flight Research, summarizes NASA and 

international contributions to LFC technology and is written for the nontechnical reader as well 

as the specialist. Ronald D. Joslin’s NASA TP 1998-208705, Overview of Laminar-Flow Control, 

is an extensive summary directed at the technical audience. Inclusion of all activities mentioned 

in these references is far beyond the intended scope of this publication; however, some key points 

have been summarized from these documents and included herein as an introduction for the 

reader. Te material presented here focuses on recent events in LFC and HLFC technology and 

emphasizes engineering activities rather than research on fundamental fow physics and boundarylayer transition mechanisms. 

Te National Advisory Committee for Aeronautics (NACA), NASA’s predecessor, had conducted 

exploratory boundary-layer research in wind tunnels as early as 1926, and in 1939 researchers 

assessed the impact of boundary-layer suction (via slots) on wind-tunnel models. In the spring 

of 1941, Langley researchers conducted the frst LFC fight tests ever made, installing a suction 

system on an experimental low-drag test panel that had been previously used for fundamental 

studies of boundary-layer transition (nonsuction) on the wing of a Douglas B-18 airplane. Te 

modifed test panel was ftted with suction slots and pressure tubes for a fight investigation of the 

transition from laminar to turbulent fow in the boundary layer. 

130 Innovation in Flight 
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B-18 wing glove tests conducted by NACA (top) and close-up view of the glove panel used 

in natural transition studies (bottom). 

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Te legendary contributions of Eastman N. Jacobs, Ira H. Abbott, and Albert E. von Doenhof 

and the Low Turbulence Pressure Tunnel’s (LTPT) role in the development of NACA laminar-fow 

airfoils are well documented in other historical works and will not be repeated here. However, the 

key lesson learned from applications of this family of natural laminar-fow airfoils to aircraft such 

as the P-51 Mustang in World War II was that large areas of laminar fow could not be achieved in 

daily combat operations because of “real-world” wing surface conditions. Despite this operational 

shortcoming, the large favorable pressure gradients used by the NACA laminar-fow airfoils resulted 

in superior high-speed characteristics, and they were used in several airplane designs. 

Research on active suction-type LFC in Germany and Switzerland during World War II stimulated 

suction LFC testing in the LTPT during the late 1940s by Albert L. Braslow, Dale L. Burrows, and 

Fioravante Visconte. Tis team carried out a range of wind-tunnel experiments that culminated in 

the demonstration of full-chord laminar fow with LFC to very high values of Reynolds number, but 

the special porous bronze surface used for the tunnel experiment was not feasible for applications 

to aircraft. 

In the 1950s, LFC research was led by the British at the Royal Aircraft Establishment and in 

the United States by Dr. Werner Pfenninger, who had come to the Northrop Corporation from 

Switzerland. Pfenninger would serve as a technical inspiration to industry, DoD (especially the 

Air Force), and NASA. From the 1970s until his death in 2003, he served as a close consultant to 

Langley researchers in LFC and HLFC studies. 

Te Air Force became intensely interested in LFC in the early 1960s due to looming mission 

requirements for a long-range subsonic transport—which would ultimately emerge as the Lockheed 

C-5 transport. A fight demonstration of LFC by a research aircraft was of special interest to early 

development activities. In particular, the Air Force desired operational and maintenance data for 

Te Northrop-Air Force X-21A laminar-fow control research aircraft. 

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application to its new transport. Te Air Force and Northrop initiated the X-21 Research Airplane 

Program, which began fight tests in April 1963, and Al Braslow served as a NASA technical 

consultant during the fight-test reviews. Pioneering data were obtained in the fight program, 

including the efects of surface irregularities, boundary-layer turbulence induced by threedimensional spanwise fow efects in the boundary layer (referred to as spanwise contamination), 

and degrading environmental efects such as ice crystals in the atmosphere. Pfenninger 

developed a critical breakthrough understanding of and means for preventing the spanwise 

contamination phenomenon. 

Laminar fow had been attained over 95 percent of the intended area by the X-21 program’s end. 

Unfortunately, the manufacturing tolerances of the X-21 wing did not meet the requirements 

for robust LFC. Shallow spanwise grooves existed in the wing outer surface that required flling 

with body putty, and the desired data on maintenance of laminar-fow systems were therefore not 

obtained. Many regard the shallow grooves as a particularly poor fabrication experience but did 

not see the grooves as evidence of any extreme difculty in fabricating LFC wings. 

Although a technical committee of industry and government engineers recommended that a new 

wing be made for follow-up testing, the Air Force position was that the new C-5 could not wait 

for the new X-21 wing and another research program. Terefore, they dropped LFC as a possible 

new technology for the C-5 and terminated the X-21 Program. Arguably, an even more important 

reason for terminating the program was that the funding and priority required by the Vietnam 

War severely drained the Air Force of research and development funds. Another contributing 

factor was the advent of high-bypass-ratio engines, which also ofered signifcant performance and 

economic benefts. In 1968, Pfenninger’s group at Northrop was disbanded, and he accepted a new 

position in the Aerodynamic Research Unit at the Boeing Commercial Aircraft Division under the 

direction of Adelbert L. (Del) Nagel. Although Nagel had extensive aerodynamic experience, he 

had a dim view of the potential of LFC. However, Nagel was very impressed with the professional 

knowledge of Pfenninger and he became convinced that the aeronautical community should work 

the concept. Nagel left Boeing in 1970 and joined the Langley staf under John V. Becker. As will 

be discussed, both Pfenninger and Nagel later had profound impacts on Langley’s LFC research. 

Following X-21 activity termination, national interest in LFC virtually disappeared from the 

middle-1960s to the early 1970s. One of the major factors for the lack of interest was the relatively 

low price of jet fuel. In the 1970s, however, that situation changed dramatically. 

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Te Aircraft Energy EfciencyProgram 

Te oil embargo imposed by members of OPEC in 1973 caused immediate chaos and concern 

within the commercial air transportation industry. Between 1973 and 1975 the cost of aircraft 

fuel tripled. Rapidly rising fuel prices and concern over future sources of fuel were rampant, and 

congressional attention turned to potential technologies that might help mitigate rising concerns. 

At the request of NASA Headquarters, the NASA feld centers surveyed technologies that might 

help alleviate the crisis. 

Del Nagel had joined the Langley staf and had been briefed by Al Braslow on the state of the 

art of LFC technology. Nagel prepared a memo for Langley Director Edgar M. Cortright citing 

the accomplishments of the X-21 Program and the huge potential beneft of LFC that urgently 

needed national attention. Although Cortright’s senior staf was generally negative, he requested 

information as to Boeing’s position on the topic. Nagel then contacted Boeing, which sent its 

Chief Aerodynamicist and others to brief Cortright, resulting in a spark of enthusiasm for NASA 

research in the area. Al Braslow later prepared a white paper on potential technology advances that 

might contribute to fuel conservation. In his opinion, the single largest potential for reductions 

in fuel usage would come from LFC, despite the problems that had been experienced in past 

research eforts. Immediate NASA response to Braslow’s paper was lukewarm at best (from both 

management and researchers). 

As Chief of the Aeronautical Systems Division, Nagel was assigned to head the Langley contingent 

of the NASA Aircraft Energy Efciency (ACEE) Task Force, or Kramer Committee as it became 

known. Braslow and William J. (Joe) Alford, Jr., were also members of the Langley group, which 

delivered well-received briefngs on LFC at all major domestic aircraft companies, at other NASA 

Centers, and at Headquarters. With the additional inputs of a number of advisory committees and 

coadvocacy from the Air Force, Cortright gave his support and approval to the establishment of a 

LFC element under the ACEE Program in 1976 led by Robert C. Leonard. Leonard’s project was 

part of the activities of the LaRC Projects Group headed by Howard T. Wright. Other elements of 

the ACEE Program included the composite structures element and the energy efcient transport 

element. Ralph J. Muraca was assigned as Deputy Manager of the LFC element of the ACEE 

Program Ofce. 

Langley 8-Foot Transonic Pressure Tunnel Tests 

In 1975, Werner Pfenninger conceived a wind-tunnel experiment to determine the capability of 

suction LFC to control the laminar boundary layer of a large-chord, swept supercritical wing. 

134 Innovation in Flight 
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Objectives included an assessment of suction LFC (via slots or perforations) to laminarize fow 

over a supercritical region, an evaluation of the ability of transition prediction theories to predict 

suction requirements, a determination of the relative efectiveness of slotted and perforated suction 

surfaces for LFC, and an evaluation of the efects of surface conditions on laminarization. His 

advocacy led to tests in the Langley 8-Foot Transonic Pressure Tunnel, which required facility 

modifcations, such as honeycomb, screens, and a sonic choke, to ensure low levels of tunnel 

turbulence and acoustic disturbances and avoid interference with boundary-layer fow. Te test 

team modifed the test section walls with foam liners to conform with free-air predictions of the 

air-fow environment. Pfenninger designed the model wing section to integrate laminar fow and 

a supercritical airfoil. William D. Harvey, Cuyler W. Brooks, Jr., and Charles D. Harris of the 

Transonic Aerodynamics Division under Percy J. (Bud) Bobbitt led the Langley research team. 

Te frst test with a slot-suction model began in 1981 and ended in 1985; perforated-suction 

testing began in 1985 and ended in 1987; and the HLFC test began in the winter of 1987 and 

ended in 1988. Joel R. (Ray) Dagenhart, Brooks, and Harris used boundary-layer stability codes 

to optimize the airfoil design by analyzing suction requirements at various test conditions. 

Te results of the tunnel tests were impressive. Te researchers achieved full-chord laminar fow 

on the upper and lower surfaces of the slot-suction wing for Mach numbers from 0.4 to 0.85. 

Laminar fow was maintained for high values of Reynolds numbers, and drag reduction for both 

upper and lower surfaces was about 60 percent. More importantly, the experiment demonstrated 

the feasibility of combined suction laminarization and supercritical aerodynamics. 

Te Leading-Edge Flight Test Project 

In 1977, researchers at NASA’s Dryden Flight Research Center joined with Langley’s Al Braslow 

and John B. Peterson, Jr., to conduct fight tests of a modifed NASA JetStar (Lockheed C-140) 

to determine the efectiveness of new concepts for alleviation of potential insect residue problems, 

which some have viewed as one of the major barriers to LFC technology. Te potential impact 

of insect residue has remained controversial because several fight experiences (such as the X21 Program) have shown that fight at cruise conditions eroded away insect remains. Te study 

included several special surface coatings that researchers hoped might shed insect remains, as well 

as a washer-type system that would wet the wing leading edge and possibly eliminate the adherence 

of impacted insects. None of the special coatings used in the study were efective in preventing the 

accumulation of insect debris, but the washer system demonstrated favorable results if the leading 

edge was wet before encountering insects. Preliminary analysis of the amount of wetting agent 

required indicated that such a system might be feasible for large commercial transports. 

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In 1980, Richard D. Wagner replaced Ralph Muraca as Head of the Langley LFC element. Langley 

began to focus its LFC eforts in the ACEE Program on an in-fight research project called the 

Leading Edge Flight Experiment (LEFT) that would address LFC leading-edge system integration 

questions and determine the practicality of LFC systems in operational environments via simulated 

Sketch of the JetStar test panel arrangement showing the Douglas perforated panel (right wing) 

and the Lockheed slotted panel (left wing). 

Te perforated Douglas Leading Edge Flight Experiment panel. 

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airline operations. Te LFC ofce selected the NASA JetStar as its test vehicle, and the Douglas 

Aircraft Company and the Lockheed-Georgia Company were contracted to design and fabricate 

leading-edge test sections for the JetStar right and left wings, respectively. Douglas designed a 

perforated panel and Lockheed proposed the use of suction slots. Lockheed was responsible for 

designing modifcations to the JetStar for each test panel. Te actual aircraft modifcations were 

performed at Dryden, with NASA personnel leading the eforts. 

Te slotted Lockheed Leading Edge Flight Experiment panel. 

View of the Douglas test article mounted on the JetStar’s right wing. 

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Along with the laminar-fow test panels, insect and ice protection were also incorporated in the 

JetStar’s wings. Te Douglas panel used suction through approximately 1 million electron-beam 

perforated holes (at 0.0025-in. diameter, smaller than a human hair) in the titanium skin to 

maintain laminar fow only on the upper surface of the article. In addition to a leading-edge insect 

shield, a propylene glycol methyl ether-water mixture spray was used for insect protection and 

anti-icing. Te Lockheed panel used 0.004-in. wide slots (thinner than tablet paper) in a titanium 

surface and a design to provide laminar fow on both the upper and lower surfaces in cruise. 

Lockheed also used fuid for anti-icing and insect protection. 

Dick Wagner was the LEFT Program Manager for Langley (the lead Center), Andrew S. Wright, 

Jr., was the Hardware Manager, and lead researchers for the project included Michael C. Fischer 

(principal investigator), Dal V. Maddalon, Richard E. Davis, and technician John P. Stack 

(instrumentation development). For Dryden, Robert S. Baron and David F. Fisher served as Project 

Manager and Principal Investigator, respectively. Te overall objective of the LEFT fights was to 

demonstrate the efectiveness and reliability of LFC systems under representative fight conditions. 

Te design point for the tests was a Mach number of 0.75 at an altitude of 38,000 ft, but ofdesign points were also fown at Mach numbers of 0.7 to 0.8. Te fight evaluations by the Dryden 

Flight Research Center also included “simulated airline service” fights between 1983 and 1987. 

Te primary objective of this part of the project was to demonstrate the ability of LFC systems 

to operate satisfactorily under conditions representative of commercial transport operations from 

ground queuing, taxi, takeof, climb to cruise, cruise, descent, landing, and taxi to ramp. Te 

aircraft would be parked outdoors, serviced routinely, fown in good and bad weather and in ice, 

rain, and insect-conducive conditions. Results of the simulated airline service showed that no 

operational problems were evident with the LFC systems, no special maintenance was required, 

and LFC performance was proven through the realization of laminar fow on the test article. 

Te LEFT Program resulted in extensive data regarding surface roughness criteria, the impact 

of environmental contaminants, and fabrication concepts. Te Douglas panel was judged the 

superior concept. Te electron-beam drilled panel presented no fabrication difculties and easily 

met LFC criteria. Te fabrication techniques for the slotted approach used by Lockheed resulted 

in a panel that was only marginally acceptable. However, even the most enthusiastic advocates of 

LFC recognized that more research would be required for the development of larger perforated 

panels (in terms of chord and span length) for commercial transports, and that the full-span 

integration of high-lift and insect protection systems would have to be addressed. 

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Hybrid Laminar-Flow Control 

Te Boeing Company did not participate in the initial phases of the ACEE Program or the LEFT 

Program because of commitments to near-term aircraft development programs. However, members 

of advanced design teams at Boeing followed the encouraging results of LEFT activities and several 

individuals who had considerable experience and interest in laminar-fow technology began to 

infuence the interests of management. Del Nagel, who had previously led the Aeronautics Systems 

Division at Langley, had left NASA to return to Boeing, and he became an outspoken company 

advocate for LFC research and actively sought participation in NASA-funded studies. 

Assimilating results obtained during LEFT, and cognizant of LFC technology in general, Boeing 

had become interested in a modifed version of LFC wherein the trade-ofs between system 

complexity for full-chord laminar fow yielded what might be a less complex concept involving 

partial-chord suction. Boeing’s Louis B. (Bernie) Gratzer advocated a new, simpler approach to 

LFC. Te concept, known as hybrid laminar-fow control (HLFC) used advanced airfoil design 

to combine some of the principles of NLF and LFC to obtain laminar fow to 50, 60, or even 70 

percent of the wing chord. Te HLFC concept applied active suction only to the front spar region 

(about the frst 15 percent of the chord) to control the adverse cross fow and attachment-line 

efects due to wing sweep. Te concept used favorable pressure gradients aft of the suction, over 

smooth surfaces, to promote the additional run of laminar fow to more aft-chord locations before 

transition occurred. 

Following a joint NASA-Boeing meeting to discuss HLFC, Ray V. Hood, Jr., Head of the Langley 

Energy Efcient Transport (EET) element of ACEE, sponsored a Boeing exploratory study of 

the HLFC concept. David B. Middleton and Dennis W. Bartlett were the contract Technical 

Managers for Langley. Tis contract represented a milestone of increasing NASA-Boeing interest 

and collaboration in research to assess and resolve apparent issues that had to be addressed before 

applications of HLFC could be considered. One of the numerous issues to be resolved was the 

potential impact of engine noise on boundary-layer transition. Many in the aeronautical community 

had expressed concern that the interaction of engine noise pressure disturbances with the boundary 

layer might trigger fow instabilities, resulting in premature transition to turbulent conditions. Te 

efect was thought by some to be so adverse that conventional wing-mounted engines would have 

to be relocated to the remote aft rear of the fuselage in order to obtain laminar fow over the wing. 

In 1985, Dick Wagner, Head of the Laminar-Flow Control Project Ofce (LFCPO), sponsored 

a contract under the ACEE Program for Boeing to conduct fight tests of a modifed Boeing 757 

aircraft evaluating the efects of engine noise on transition for a wing “glove” test article. Te glove 

consisted of a 10-ft span smooth NLF section equipped with detailed instrumentation to measure 

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In-fight view of the natural laminar fow glove mounted on the Boeing 757’s right wing during boundary-layer noise 

sensitivity evaluations. 

the position of transition from laminar to turbulent conditions. Te right engine, which was in 

close proximity to the glove, was throttled in fight at various altitudes and speeds to determine 

the efects of noise on transition. Te results of the investigation were encouraging in that the 

near-feld engine noise did not appear to have a signifcant efect on upper-surface boundary layer 

transition mechanisms. 

Other critical research studies had to be undertaken to provide data analysis for studies of transition 

mechanisms to assist in the design of HLFC concepts. In one such study funded by the ACEE 

Program, the LFCPO at Langley, Boeing, and a team of fight researchers at Dryden conducted 

joint fight tests of a modifed Navy F-14 Tomcat airplane at Dryden in 1986 and 1987 in a 

program known as the Variable-Sweep Transition Flight Experiment (VSTFE). 

Dennis Bartlett was the Langley Principal Investigator for VSTFE, sharing program responsibilities 

with Robert (Bob) R. Meyer, Jr., Marta Bohn-Meyer, and Bianca M. Trujillo of Dryden. At 

Langley, Fayette (Fay) S. Collier, Jr., conducted extensive analysis and correlation of transition 

location predictions with boundary-layer stability theories. Te objectives of the project were to 

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Te F-14 Variable-Sweep Transition Flight Experiment airplane in fight with research gloves 

on both wing panels 

obtain fight transition data for a range of wing-sweep angles at high subsonic speeds. Detailed 

data analyses provided fundamental information on the efects of sweep, Reynolds number, 

and wing section on critical boundary-layer transition mechanisms. Te NASA research team 

chose an F-14 aircraft as the research vehicle for the VSTFE Program primarily because of its 

variable-sweep capability, Mach and Reynolds number capability, availability, and favorable wing 

pressure distribution. 

Computational work at Langley by Edgar G. Waggoner and Richard L. Campbell, and tunnel 

testing in the Langley National Transonic Facility (NTF) by Pamela S. Phillips and James B. 

Hallissy guided the project. One of the variable sweep outer-wing panels of the F-14 was modifed 

with a specially designed NLF glove to provide a test airfoil that produced a wide range of favorable 

pressure distributions for which transition locations were determined at various fight conditions 

and sweep angles. Under contract to the LFCPO, Boeing had also designed a candidate airfoil, but 

funding constraints prevented fight testing of that design. A conventional 64-series NACA airfoil 

glove article installed on the upper surface of the left wing was a “cleanup” for smoothing the basic 

F-14 wing, while the Langley-designed glove on the right wing panel provided specifc pressure 

distributions at the design point of Mach 0.7. Data gathered in this fight program provided detailed 

transition information that was vital to validate predicted NLF ranges that could be experienced 

at relatively high sweep and Reynolds numbers. With successful test data results, optimism rapidly 

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grew that the principles of NLF could be incorporated into the HLFC concept and that active 

HLFC suction could be limited to only the leading-edge region of swept wings. 

In all phases of the ACEE LFC and fundamental HLFC research at Langley, the projects included 

signifcant contributions by outstanding instrumentation and fight data support. For example, 

John P. (Pete) Stack developed hot-flm technology and instruments that provided unprecedented 

capability for boundary layer analysis. 

In March 1987, Langley hosted a national symposium, Research in Natural Laminar Flow and 

Laminar-Flow Control, to disseminate laminar-fow technology gained during the ACEE-sponsored 

research projects and to disseminate additional information gathered in activities conducted within 

the more fundamental Research and Technology Base Program. Te symposium, with over 170 

NASA, industry, university, and DoD attendees, included technical sessions on advanced theory 

and tool development, wind-tunnel and fight research, transition measurement and detection 

techniques, low and high Reynolds number research, and subsonic and supersonic research. Te 

event was one of the most important interchanges to occur within the domestic aeronautical 

community, which viewed it as an impressive success. 

In addition to a very large number of experimentalists, fight researchers, and systems engineers, 

the emergence of a new talent community led by experts in CFD and transition physics began to 

accelerate the understanding of transition fundamentals. One of the leaders in the feld was Mujeeb 

R. Malik, whose COSAL code became a primary tool in the design of HLFC experiments. 

B757 Flight Evaluation 

While NASA and Boeing geared up for increased research in HLFC, other organizations were also 

conducting assessment studies for future applications of LFC. For example, Lockheed-Georgia had 

conducted contracted studies for both NASA and the Air Force to assess potential benefts of LFC 

and HLFC for advanced military transports. As previously discussed, the Air Force had been the 

leading domestic proponent of LFC in the 1960s, as evidenced by its X-21 fight research activity. 

Langley found that the Air Force was interested in a cooperative program to assess the HLFC 

concept. Both parties subsequently signed a formal Memorandum of Understanding specifying 

the funding levels to be provided, which were equally shared by NASA and the Air Force. Te Air 

Force motivation was to demonstrate HLFC for possible applications to future transports capable 

of taking of from the United States, fying to the Middle East fully loaded, and returning to the 

United States without refueling. 

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Both Boeing and Douglas bid on a competitive contract issued by NASA for a fight research 

demonstration of HLFC. After a combined team of NASA and Air Force personnel evaluated the 

proposals, they awarded a contract to Boeing for a fight demonstration of partial-span HLFC 

on its 757 prototype airplane. In 1987, NASA, the U.S. Air Force Wright Laboratory, and the 

Boeing Commercial Airplane Group agreed that the project would be fown out of Boeing’s Seattle 

facilities. Te 3-year, $30 million program started in November 1987 as a joint NASA-Air Force 

program managed by Langley and cost shared by the participants (34-percent Boeing and 66-

percent government). Te primary objectives of the program were to develop a database on the 

efectiveness of the HLFC concept applied to a medium-sized, subsonic commercial transport; to 

evaluate real-world performance and reliability of HLFC at fight Reynolds numbers (including 

of-design conditions); and to develop and validate integrated and practical high-lift, anti-ice, and 

HLFC systems. 

Design work by Boeing on the modifcations to the 757 airplane began as scheduled in November 

1987. Boeing’s team replaced a 22-ft span segment of the leading-edge box located outboard of 

the left wing engine nacelle pylon with a laser-drilled HLFC leading-edge test panel with about 

22 million tiny holes. Tis new leading edge consisted of a perforated titanium outer skin, suction 

futes under the skin, and collection ducts to allow suction to maintain a laminar boundary layer 

from the leading edge to the front spar. Manufacturing challenges faced in the program were among 

the most demanding issues, and successful solutions to numerous problems that were encountered 

Te prototype Boeing 757 transport used for the hybrid laminar fow control fight experiments. 

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remain proprietary to Boeing. Te modifed leading edge included a Krueger shield (somewhat 

similar to that conceived by Douglas in the LEFT project previously discussed) integrated for high 

lift and insect protection and hot-air deicing systems. 

Te team positioned fush-mounted pressure taps in the perforated leading edge and used tubing 

belts to measure the external pressure distributions over the wing box. Tey used hot-flm sensors 

to determine the transition location on the wing box. For boundary-layer transition detection, they 

used infrared camera imaging. Also, wake-survey probes were located behind the wing trailing 

edge to provide data for local drag-reduction estimates. Te fight test engineers monitored the state 

of the laminar boundary layer, the internal and external pressure distributions, and the suction 

system in real time onboard the aircraft during the fight test. 

View of the instrumented left wing of the 757 test aircraft showing the test panel area, hot-flm gauges, pressure tubing, 

and the leading-edge Krueger fap/insect shield. 

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Langley researcher Dal Maddalon (right) and Boeing engineer David W. Lund (left) monitor wing transition data 

aboard the 757 during a typical research fight. 

Te Boeing 757 HLFC test bed aircraft in fight near Seattle. 

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Te design point for the 757 fight tests was Mach 0.8, but fight tests of many of-design conditions 

were performed to investigate the extent of laminar fow as a function of Mach number, Reynolds 

number, and other parameters. Twenty research fights were conducted in 1990 and an additional 

ten fights were made in 1991. Additional analysis of fight data carried on through 1992. Te pace 

of fight testing was a signifcant challenge successfully met by Boeing, who was also using the 757 

prototype for concurrent in-fight avionics development testing for the Boeing team’s entry in the 

Air Force Advanced Tactical Fighter Program, which later became the F-22. 

Te results of the 757 fight tests demonstrated that this frst-generation HLFC concept was 

extremely efective in delaying boundary-layer transition as far back as the rear spar for the design 

fight condition of Mach 0.8. Te data indicated that most of the hot flms measured laminar fow 

beyond 65-percent chord. Te wake-rake measurements indicated a local drag reduction of about 

29 percent with the HLFC system operational, resulting in a projected 6-percent drag reduction 

for the aircraft. 

In summary, the 757 HLFC demonstration showed that production manufacturing technology 

could meet the laminar-fow surface tolerance requirements and that a practical HLFC system could 

be integrated into a commercial transport wing leading edge (suction panel with ducting, Krueger 

high lift/insect shield, hot-air deicing system, suction surface purge, and suction compressor in 

pylon). Despite these impressive results, the fight results recorded a puzzling (although favorable) 

outcome—the suction rates required to achieve laminar fow to 65-percent chord were only about 

one third of those predicted during the initial design of the system. Te disparity in design suction 

levels could be attributed to an overly conservative design approach, but the 757 results indicated 

that the suction system could be further simplifed by more accurate criteria. Interestingly, Werner 

Pfenninger had forewarned that the suction levels would be less than the initial design based on 

his analysis of the application. Additional insight into the discrepancy came when Fay Collier 

conducted pioneering CFD analysis by developing a refned version (including curvature efects) 

of Mujeeb R. Malik’s COSAL code, resulting in improved agreement between CFD predictions 

and fight results. 

Following the 757 fight tests, Langley’s Mission Analysis Branch under William J. Small and the 

Vehicle Integration Branch led by Samuel L. Dollyhigh conducted independent analyses of the 

benefts of HLFC for a representative advanced transport aircraft. Te analyses were based on a 

300-passenger transport for a 6,500-nmi mission with laminar fow over the upper wing, upperand lower-tail surfaces, and over the vertical fn. Te results indicated an impressive 13-percent 

savings in fuel burned for the HLFC-equipped airplane compared with a conventional transport. 

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Transition contours showing the extent of laminar fow obtained on the wing upper surface of the 757 with hybrid 

laminar fow control. 

Roy V. Harris, Jr., Director of Aeronautics, transmitted the results of these system studies to John 

D. Warner, Vice President of Engineering at Boeing in November 1990, to call his attention to 

Langley’s projection of the potential benefts of HLFC and to ask Boeing to conduct its own studies 

for comparison. Harris was aware that Langley researchers were not exposed to highly proprietary 

industry methods and data for estimating the total economic impact of technology; therefore, a 

more refned analysis by industry would be required for a better projection of the value of HLFC. 

In 1991, Boeing formed a 40-person multidisciplinary assessment team that addressed all aspects 

of the cost-beneft trades for HLFC. Te extensive Boeing study addressed aerodynamics, weight, 

propulsion, structures, manufacturing, safety, reliability and maintainability, marketing, fnance, 

and other issues from an airplane manufacturer’s perspective. 

After extensive analysis, the Boeing team concluded that the total operating cost-beneft projections 

for HLFC at fuel prices of the time were positive, but not large enough to warrant the risks that 

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Size comparison of the 757 airplane and other civil and military transports. 

still existed for applications of HLFC to commercial applications. Certifable insect protection 

and deicing systems still required further research, and the use of a full-span Krueger for high 

lift was not an optimum solution (although the use of a Krueger for a laminar-fow airplane may 

well outweigh the Krueger’s disadvantage). In addition, the fact that the 757 fight program did 

not address the inner-wing area (where transition is expected to be a more formidable challenge 

because of longer wing-chord lengths) represented an application barrier. Another major issue is 

the aerodynamic interference on the inner upper-wing surface caused by very large high-bypassratio engine-pylon confgurations used on transport confgurations. Te interference problem 

was viewed as becoming even more critical for the larger ultra-high-bypass engines expected in 

the future. 

Finally, the challenge of successfully applying HLFC to transports larger than the 757 remains a 

signifcant issue (recall that higher Reynolds numbers are associated with large aircraft and that high 

148 Innovation in Flight 
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values greatly sensitize the transition process). At the termination of the 757 experiments, Boeing’s 

immediate interest was in applying HLFC to large aircraft (of the 747 class), and considerable 

concern existed over the feasibility of applications to such designs. Te LFCPO proposed a followup large-scale inboard HLFC wing experiment to NASA Headquarters in late 1990, but at that 

time the price of jet fuel had decreased signifcantly. Boeing ultimately refocused on transports 

smaller than the 747 and made the decision that its new transport, the B777, would not use LFC. 

Meanwhile, NASA’s focus in aeronautics had shifted to a second-generation supersonic transport. 

Te loss of momentum and support for HLFC within the aircraft industry and NASA after the 

757 fight program had a powerful, far-reaching negative impact on what had been a decade of 

rapidly accelerating development for potential future applications. 

OV-1B Nacelle Experiments 

With turbofan engine size rapidly growing with each generation of large transports, aerodynamic 

drag of the nacelle-pylon components of the propulsion system becomes signifcant. For a large 

commercial transport with wing-pylon mounted engines, an application of LFC that results in 

a 50-percent reduction in nacelle friction drag would be equivalent to a 2-percent reduction in 

total aircraft drag and cruise fuel burned. In the middle-1980s, interest began to intensify in the 

potential application of LFC concepts to nacelle confgurations. Langley and the General Electric 

Company initiated a cooperative program to explore this application of NLF technology in a 

series of wind-tunnel, computational, and fight experiments. Initially, an NLF fairing was fown 

on a Cessna Citation nacelle to develop the experimental technique and establish feasibility. In 

the second phase of the program, the General Electric-NASA team designed and evaluated fowthrough NLF nacelle concepts. Te research team positioned advanced nacelle shapes below the 

right wing of a NASA OV-1 research aircraft. Tey also used a controlled noise-generating source 

in an under-wing pod outboard of the nacelle and a second noise source in the fow-through 

nacelle centerbody. 

Earl C. Hastings, Jr., was Langley’s Project Manager for the OV-1 Program and his team included 

Cliford J. Obara (aerodynamics and fow visualization), Simha S. Dodbele (aerodynamics), 

and James A. Schoenster (acoustics). Te fight test program’s scope included measurements of 

static pressures, fuctuating pressures caused by the noise sources, and fow visualization of the 

transition pattern on the nacelle using sublimating chemicals. Te team collected data with the 

noise sources on and of and with various combinations of acoustic frequencies and sound pressure 

levels. During the acquisition, the right-hand aircraft engine was feathered to reduce propeller 

interference efects. 

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Te NASA OV-1B in fight with an NLF nacelle under the right wing. Note feathered propeller and 

underwing pod containing noise source. 

Prior to the fight tests, General Electric had teamed with Langley for tests of an isolated NLF 

nacelle as well as tests of a nacelle installed on a representative high-wing transport model in 

the Langley 16-Foot Transonic Tunnel. Te results of the tunnel tests provided guidance for the 

external geometry of the nacelle to promote NLF. Te pressure distribution on the outer walls of a 

conventional high-bypass-ratio engine nacelle is not conducive to NLF requirements. For a typical 

conventional nacelle, the lip of the inlet is relatively large, and the airfow rapidly accelerates to 

a velocity peak near the lip then decelerates over the remainder of the nacelle length. Boundarylayer transition occurs at the start of deceleration, so turbulent fow with high friction drag exists 

over most of the nacelle. An NLF nacelle is contoured to have a relatively small inlet radius and 

an accelerating fow over most of its length (about 70 percent), so transition is delayed and a 

relatively lower drag exists over most of the nacelle. Te relatively small lip radius for the NLF 

design may aggravate inlet infow distortion at of-design, crosswind, and engine-out conditions, 

thereby requiring careful analysis and design of the nacelle shape. General Electric designed and 

150 Innovation in Flight 
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Sublimating chemicals indicate laminar fow (white area) on forward region of NLF nacelle during 

research fight. 

fabricated three fberglass and aluminum structured nacelles for the fight test program, including 

instrumentation for external and internal static pressures, sound pressure levels, total pressures, 

and transition location. 

Flight test results indicated that NLF was maintained as far aft as 50 percent of the nacelle length. 

No change was observed in the boundary-layer transition pattern when the noise sources were 

operated. Tese results served to broaden interest within the aeropropulsion community for 

potential applications to reduce nacelle drag. Te unique requirements for satisfactory of-design 

characteristics were recognized as the major challenge for such applications of NLF. Signifcantly, 

this research project created widespread recognition as a catalyst to the propulsion community’s 

interest in laminar-fow applications and the real-time technology transfer that occurred between 

Langley and its General Electric partner. Tis interest was soon to grow into applications of the 

HLFC concept to nacelles. 

General Electric Nacelle 

In 1990, representatives of General Electric Aircraft Engines (GEAE) visited the LFCPO to discuss 

mutual interest in the potential application of HLFC technology to reduce the aerodynamic drag 

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of engine nacelles and pylons. In particular, GEAE sought Langley participation and consultation 

in its project with Rohr Industries, Inc., and Allied Signal Aerospace for a fight demonstration 

of the HLFC concept applied to the external surface of a current large turbofan engine nacelle. 

Te project’s objectives were to demonstrate laminar fow to 40 percent of the nacelle length using 

HLFC and to demonstrate a 1.5-percent reduction in specifc fuel consumption. 

Langley’s expertise in HLFC technology, especially the design of efective HLFC pressure 

distributions for aerodynamic surfaces, instrumentation for transition measurements, and HLFC 

systems and fight test techniques, were of great value to the GEAE team. Fayette S. Collier, Jr. 

(who succeeded Dick Wagner as Head of the LFCPO in 1991), Cynthia C. Lee (Head of the Flight 

Research Branch), and Vernie H. Knight, Jr. (Head of the Aircraft Instrumentation Branch), led 

Langley’s involvement in the cooperative project. 

In addition to design guidance and active participation in nacelle engineering design reviews, 

Langley provided the project suction-system components previously used for the JetStar LEFT 

fight tests. Tis system was based on a remarkable “sonic valve” concept conceived by Langley’s 

Emanuel (Manny) Boxer. Te Langley team designed and installed an onboard, real-time data 

monitoring display and an instrumentation package for transition detection. Te team transferred 

extensive NASA LEFT Program technology to GEAE and Rohr during the project. 

GEAE modifed a production GEAE CF6-50C2 engine nacelle installed on the starboard wing 

of an Airbus A300 testbed aircraft to incorporate an inboard and an outboard HLFC panel. Te 

panels were fabricated of a perforated composite material with suction from the highlight aft to 

the outer barrel-fan cowl juncture. Suction was applied to the surface using circumferential futes 

and was collected and ducted to a turbo compressor unit driven by engine bleed. For convenience, 

GEAE located the turbocompressor unit in the storage bay of the aircraft. Te fow through each 

fute was individually metered. Te GEAE-NASA team designed and fabricated the laminar-fow 

contour, which extended aft over the fan cowl door by using a nonperforated composite structure 

blended back into the original nacelle contour ahead of the thrust reverser. No provisions were 

made for ice-accumulation or insect-contamination avoidance systems. Te team designed extensive 

instrumentation, including static-pressure taps that were mounted on the external surface and in 

the futes, a boundary-layer rake used to measure the state of the boundary layer, and hot-flm 

gauges used for boundary-layer transition detection. Flight engineers onboard the aircraft used 

surface-embedded microphones to measure noise, and they monitored the state of the boundary 

layer and suction system in real time. Perhaps the largest constraint to the research team was 

working within predetermined cowl lines. 

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Te project’s fight-test phase during July and August of 1992 included 16 fights totaling 50 

fight hours. Te HLFC concept was efective over the range of cruise altitude and Mach number 

investigated and resulted in laminar fow to as much as 43 percent of the nacelle length (the design 

objective), independent of altitude. Langley researchers Y. S. Wie, Collier, and Wagner believed 

the General Electric objective was conservative because the Langley team had designed an HLFC 

nacelle with a potential for 65-percent nacelle laminar fow. 

Langley 8-Foot Transonic Pressure Tunnel Test 

Although the Boeing 757 HLFC fight-test experiment demonstrated signifcant runs of laminar 

fow using only leading-edge suction, the fact that the amount of suction required was less than 

one-third of the predicted level caused uncertainty in the design tools, making the technology an 

unacceptable risk for the commercial market. To provide a better understanding of complex fow 

physics over a swept-wing geometry, generate a calibration database for the LFC design tools, and 

better understand the issues of suction-system design, a joint NASA-Boeing project to conduct 

HLFC wind-tunnel experiments on a research wing model in the Langley 8-Foot Transonic 

Pressure Tunnel was designed from 1993 to 1994 and conducted in 1995. Jerome T. Kegelman 

was the Langley Technical Leader for the project (which was funded by Elizabeth B. Plentovich 

of the Advanced Subsonic Technology Ofce). His research team included Craig L. Streett and 

Richard W. Wlezien, who led the computational and experimental eforts, respectively. Streett and 

Wlezien used a unique blend of CFD and numerical simulation of complex fuid mechanics to an 

unprecedented extent to guide experiment design and execution for everything from the design of 

the test article and measurement equipment to the analysis of the results. 

Another key member of Kegelman’s team was Vernon E. (Butch) Watkins, who led eforts to solve 

numerous potential show-stopping model and instrumentation issues resulting from tolerance 

requirements, vibration levels, and other test phenomena. Kennie H. Jones also contributed a testing 

highlight in the form of real-time data transfer from Langley’s test site to Boeing’s engineering 

ofces in Seattle, Washington. All participants regarded the rapid dissemination of data for analysis 

and test planning as one of the most outstanding customer relations eforts by Langley. Over 200 

researchers, designers, machinists, and technicians worked on this unique efort. 

Te test team installed a swept-wing model with a 7-ft span and 10-ft chord in the tunnel in 

January 1995, and tests were conducted throughout the year. Tey installed tunnel liners to 

simulate an infnite swept wing. Te researchers obtained over 3,000 infrared images and 6,000 

velocity profles (hot-wire data) during the tests. Kegelman’s team analyzed the infuence of hole 

size and spacing and suction level and distribution on the transition location and correlated the 

results with predictions obtained from the design tools. Sufcient suction levels easily allowed 

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Relative size of Langley researcher Vernie Knight illustrates the massive 

size of the General Electric CF6-50 engine nacelle. 

View of the instrumented CF6-50 engine during hybrid laminar fow control nacelle fight tests. 

154 Innovation in Flight 
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laminar fow back to the pressure minimum. Te team also made detailed surface roughness and 

suction level measurements. 

Te results of the tunnel tests, coupled with breakthrough CFD analysis by Craig Streett using 

a higher order modifcation of Mujeeb R. Malik’s COSAL code, refned the suction analysis for 

HLFC and explained the major diferences in designed and required suction levels experienced in 

the 757 fight tests. As a result of Langley’s computational eforts, the accuracy of CFD predictions 

for subsonic LFC applications are considered reliable and ready for applications. 

Supersonic Laminar-Flow Control 

In the late 1980s, NASA initiated the HSR Program to develop technologies required for secondgeneration supersonic civil transports. Te potential benefts of successfully applying LFC to 

aircraft that cruise at supersonic speeds are very attractive. Increased range, improved fuel economy, 

and reduced weight are among the benefts, as is the case for subsonic transports. However, the 

impact of weight reductions aforded by laminar fow have much larger implications for supersonic 

cruise aircraft, which typically have relatively low payload-to-weight ratios. Because of the greater 

amounts of fuel needed at a representative supersonic design cruise speed of Mach 2, even a small 

percentage reduction in drag could have tremendous economic benefts. 

Te Langley LFCPO initiated two brief exploratory fight evaluations of supersonic boundary-layer 

transition in 1985 and 1986 using an F-106 testbed at Langley and an F-15 at Dryden. Langley 

fabrication teams mounted surface cleanup gloves on both the right wing (leading-edge sweep of 

60°) and the vertical tail (sweep of 55°) of the F-106. Dryden researchers installed a surface cleanup 

glove on the right wing of the F-15 to eliminate surface imperfections of the original wing. Te 

glove was 4-ft wide and extended past 30-percent chord. 

Advocacy for supersonic laminar-fow research within the NASA HSR Program was relatively 

limited, especially at NASA Headquarters. In view of the historical problems that had been 

encountered in subsonic LFC studies prior to the 757 fight demonstrations, and the technical 

difculty of avoiding early transition on the highly-swept wings envisioned for supersonic transports, 

supersonic laminar-fow control (SLFC) received a low priority within the HSCT activities despite 

its potential benefts. 

Both Boeing and McDonnell Douglas conducted beneft analyses for SLFC under contract to Dick 

Wagner’s LFCPO in 1989. Te potential mission and economic benefts of SLFC were identifed in 

both studies, but the formidable barriers to attaining feasible SLFC on supersonic transports were 

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obvious. Both contractors recommended supersonic fight research to evaluate the efectiveness of 

LFC and HLFC concepts to promote supersonic laminar fow. 

Dryden used one of two F-16XL cranked-arrow delta wing prototype aircraft, on loan from the 

Air Force, to conduct exploratory investigations of laminar-fow technology during 1992. Dryden 

researchers tested a small, perforated titanium wing glove with a turbo compressor on the F-16XL 

(ship 1, single crew). Tis fight research program ended in 1996, followed by tests with NASA’s 

two-seat F-16XL (ship 2) using a larger suction glove. 

In the spring of 1992, Boeing began working with NASA Langley and Dryden, Rockwell, and 

McDonnell Douglas in an HSR-sponsored project for the design and testing of a supersonic 

HLFC glove on F-16XL ship 2. Michael C. Fischer of the LFCPO was the NASA technical 

principal investigator for the program, and Marta Bohn-Meyer was the Dryden fight project 

manager. Boeing and Rockwell were responsible for the fabrication and installation of the glove, 

while Boeing and Douglas assisted in the analysis of fight data. 

Te SLFC glove on the F-16XL covered about 75-percent of the upper-wing surface and 60-percent 

of the wing’s leading edge. A turbocompressor in the aircraft’s fuselage provided suction to draw air 

through more than 10 million tiny laser-drilled holes in the titanium glove via a manifold system 

employing 20 valves. Te researchers instrumented the glove to determine the extent of laminar 

fow and measure other variables, such as the acoustic environment that may afect laminar fow 

at various fight conditions. 

Te fight test portion of the F-16XL SLFC program ended on November 26, 1996 after 45 test 

fights. Te project demonstrated that laminar airfow could be achieved over a major portion of a 

wing at supersonic speeds using a suction system. Te NASA-industry team logged about 90 hours 

of fight time with the unique aircraft during the 13-month fight research program, much of it at 

speeds of Mach 2. 

Status and Outlook 

Te technical status of LFC technology has advanced greatly over the last 30 years. Advances 

in design methodology, manufacturing capabilities, and the assessment and documentation of 

laminar-fow phenomena across the speed range from subsonic to supersonic fight conditions 

have continued to mature the state of the art. A highlight of these technical activities has been 

the introduction of the HLFC concept and its development and evaluation through fight tests. 

Langley’s contributions to the technology from in-house studies and experiments, as well as 

156 Innovation in Flight 
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Modifed F-16XL Ship 2 with supersonic laminar-fow glove installed in 

left wing panel. 

Size of holes in F-16XL test glove compared with a dime. 

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its contracted and cooperative eforts with other NASA Centers, industry, and DoD partners, 

represent some of the most signifcant advances to date. 

Some elements of the technology still warrant further research and development, including 

certifcation issues (such as reserve fuel requirements), concepts for insect protection, and the 

refnement and validation of design methodology for boundary-layer stabilization. Many do 

not view the use of full-span Krueger-type wing leading-edge faps for insect protection as an 

acceptable application because these types of faps are normally limited to partial-span applications 

for structural and aerodynamic reasons, and Krueger faps are not as efective as leading-edge slats 

for takeof performance. However, the relatively low Reynolds numbers experienced on the outer 

wing may lead to another approach for a leading-edge device, or perhaps none at all. HLFC’s lack 

of demonstrated success for inboard wing locations represents a serious technical challenge. Perhaps 

the largest concern in industry, however, is the lack of confdence in wind tunnels and CFD to 

work laminar-fow designs and details as opposed to building very expensive prototype aircraft. 

At this time, fight testing is recognized as the only reliable way to guarantee the performance of 

airplane HLFC applications. 

In 1994, Langley Research Center reorganized and dissolved the LFCPO with its emphasis on fight 

demonstrations and applications-oriented research. Members of the organization were reassigned 

to other duties or more fundamental boundary-layer transition studies. Since the LFCPO demise, 

there has been no known fight development activity in the United States for LFC or HLFC. 

As a fnal observation on the technical status of LFC, it should be noted that the leadership of the 

United States in LFC technology through the 1990s did not go without notice in the international 

community. Spurred on by successful American eforts, continuing European interest and research 

activities in the technology are evident today. Te European community LFC eforts are being 

pursued by aggressive research activities for future applications to commercial transports. Notable 

activities have included startup of a German national program on LFC (1988); initiation of the 

European Laminar-Flow Investigation in 1988; various laminar-fow wing, tail, and nacelle tunnel 

and fight work (1986 to 1995) by France, Germany and others; and French wind-tunnel and fight 

research on HLFC applications using the A320 and A340 (1991 to 1995). 

Unfortunately, domestic industry and airlines still regard LFC applications as an inherently high 

risk based on their own cost-beneft studies, which conclude that the risk outweighs the projected 

aerodynamic benefts of HLFC. Te results of such studies are signifcantly impacted by the 

relative cost of jet fuel and its inherent dependence on world political and economic situations. 

Te accompanying graph indicates the average domestic cost of jet fuel (not adjusted for infation) 

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Historical trend of average cost of jet fuel. 

for the last 35 years. As expected, the trends shown by the annual average cost variations follow 

major world events, recessions, and instabilities. Tree of the major recessions of the past 30 years 

can, in large measure, be attributed to the steep increases in fuel prices that accompanied the 1973 

OPEC oil embargo, the 1980 Iran Crisis, and the 1990 to 1991 Gulf War. During the 1990s, the 

average fuel price decreased and remained relatively stable compared with the traumatic increases 

experienced during the 1970s. At the same time, jet fuel costs as a percent of total operational costs 

were dramatically reduced when fight crew and personnel costs increased. For example, fuel costs 

represented about 30 percent of airline operating costs in 1980. By 1995, however, fuel costs had 

dropped to only about 10 to 12 percent of operating costs. Some have used these data to support 

a position that fuel costs have become a secondary player and do not warrant a drive for more 

sophisticated technologies to reduce fuel usage. Indeed, the decline in fuel prices of the early 1990s 

coupled with technical issues to defate the momentum of the Langley HLFC research activities 

for subsonic transports. 

Te tenuous day-to-day nature of fuel costs for the airline industry are not refected in average 

annual costs. Large fuctuations in fuel prices (as much as 50 cents/gal) have been experienced 

over time periods as short as one month. Recalling that each 1-cent rise in fuel prices increases the 

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Jet fuel cost as a percent of total operating costs. 

industry’s annual expenses by $180 million, this level of price instability causes havoc throughout 

the airline industry. 

In January 2004, jet fuel prices climbed to levels not seen since before the war in Iraq, prompting 

some airlines to raise fares and threatening to slow the industry’s recovery. Prices for jet fuel rose 

almost 40 percent since the previous September to more than a dollar per gallon. Te spot price 

for jet fuel reached $1.05 per gallon in New York and $1.08 in Los Angeles, according to the 

Department of Energy. Outlook for airline economic recovery continues to be pessimistic, with 

rising oil prices beginning to dominate concerns. About half the airline industry’s 2003 losses were 

related to increasing fuel costs. Driving fuel prices up are the declining value of the U.S. dollar, 

OPEC pricing policies, and aggressive government purchases of oil for the country’s strategic 

petroleum reserve. Each dollar increase in the price of oil translates into an additional 2 to 3 cents 

per gallon for jet fuel. 

160 Innovation in Flight 
LAMINAR-FLOW CONTROL: THE HOLY GRAIL OF AERODYNAMICS 

Te domestic airline industry cannot aford signifcant energy price increases. In 1990 and 1991, 

almost half the airline industry fled for protection under chapter 11 of the bankruptcy code, 

long standing airlines went out of business, more than 100,000 employees lost their jobs, and the 

industry went into a fnancial tailspin from which it took years to recover. Today’s record-setting 

fuel price increases (over $63 a barrel in mid-2005) take place against an even grimmer backdrop 

of economic chaos in the airline industry. In the period from 2001 to early 2005, the nation’s 

airlines posted operating losses of over $22 billion. Analysts expect domestic airlines to collectively 

lose over $5 billion in 2005, in large part because the price of jet fuel had doubled what it was 

in 2003. 

In summary, continued development of LFC technologies by NASA and its partners through the 

1990s has removed many of the barriers to applications by airlines in the future. Work remains 

to be done, including advanced insect-protection concepts and validation of design methods. 

Systems-level studies continue to include HLFC research for future commercial long-range 

aircraft, raising the bar for increases in fuel efciency and reductions in environmental impact. 

However, it is widely recognized that a continuation of relatively expensive fight investigations and 

demonstrations will be required in the future to reach adequate levels of maturity. At the present 

time, aerospace conglomerates in Europe are aggressively pursuing the fnal stages of development 

for this revolutionary technology while eforts in the United States have become stagnant. 

Meanwhile, the domestic airline feet continues to live in a paper-thin proft situation wherein 

wildly fuctuating fuel prices can result in catastrophic economic conditions. Te result of this 

economic chaos is small proft margins, even in the best of times. Trough the years airlines have 

earned a net proft between 1 and 2 percent, compared with an average of above 5 percent for 

American industry as a whole. It remains to be seen whether the continued fuel crisis (real and 

potential) can be tolerated, particularly if the persistent political instability of the Middle East 

results in new conficts that signifcantly increase the price of oil. 

Innovation in Flight 161 

Upper Surface Blowing: Effcient, Quiet, Short Takeoff and Landing 

Concept and Benefts 

Performing operational short takeof and landing (STOL) missions has been a target of innovation 

for aircraft designers since the beginning of heavier-than-air fight. Today, an increasing interest in 

using smaller airports with shorter runways for increased mobility and passenger capacity in our 

air transportation system is refocusing attention on aircraft concepts that provide STOL capability. 

Numerous aerodynamic and mechanical methods have been proposed and evaluated for such 

applications to fxed-wing aircraft, including the use of very low wing loading (ratio of aircraft 

weight to wing area), passive leading- and trailing-edge mechanical high-lift devices, boundarylayer control on leading- and trailing-edge devices, and redirection of the propeller or jet engine 

exhausts on trailing-edge fap systems. Using engine exhaust to augment wing lift is known as 

powered lift, and this approach difers from vertical takeof and landing (VTOL) systems where 

power is used for direct lift. During the middle 1950s, intense research eforts on several poweredlift schemes began in Europe and the United States, resulting in dramatic increases in lift available 

for STOL applications. Te accompanying sketch is a history of maximum lift development from 

the Wright brothers era. 

Historical development of maximum lift coefcient for aircraft. 

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Initially, the use of mechanical trailing-edge faps and the refnement of these faps led to a rapid 

rate of increase in maximum lift, but it later became apparent that airplanes would soon be using 

up most of the mechanical-fap high-lift technology made available by evolutionary advances. In 

the 1950s, researchers explored employing the efux of engines to augment wing lift using the jetfap concept to remove the limitations of conventional high-lift devices. As shown by the sketch, the 

magnitude of maximum lift obtained in this approach can be dramatically increased—by factors 

of three to four times as large as those exhibited by conventional confgurations—permitting vast 

reductions in feld length requirements and approach speeds. Tis revolutionary breakthrough to 

providing high lift led to remarkable research and development eforts. 

One of the most promising powered-lift concepts is the upper surface blown (USB) fap. Before 

discussing this innovative concept, however, some background material on powered-lift technology 

is presented for the beneft of the reader. 

Te USB concept (or any other powered-lift concept) produces lift made up of the three components 

indicated in the sketch. Te variation of total lift with engine thrust is presented along with the 

Components of lift for a powered-lift airplane. 

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UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

Powered-lift concepts for lift augmentation. 

contributions of various powered-lift components for a fxed aircraft angle of attack and airspeed. 

Te power-of conventional lift component is produced by the wing and its leading- and trailingedge fap systems and usually does not vary signifcantly with engine thrust. Te lift component due 

to defection of the thrust (i.e., the vertical vector component of the thrust) and the lift component 

due to circulation lift (additional circulation lift induced on the wing and fap by the presence of 

the attached jet sheet) are strong functions of engine thrust. Te specifc variations of all three 

components with engine thrusts are strongly dependent on the geometry of the engine-fap-wing 

geometric arrangement. 

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Some of the diferent powered-lift concepts coming from the NASA research eforts are illustrated 

in the accompanying sketch. Te blowing boundary-layer control scheme illustrated at the top 

of the fgure is not considered a true powered-lift concept because it only uses engine bleed air 

and does not make full use of the available engine thrust. In the early 1950s, John S. Antinello 

of the U.S. Air Force, along with foreign researchers in England and France, led research on the 

Te British Hunting 126 jet-fap research airplane. 

next concept, known as the jet fap. Te aerodynamic efectiveness of the jet-fap concept was 

extremely high, and initial evaluations were conducted in England on a Hunting 126 jet-fap 

research aircraft. A system of 16 nozzles positioned along the wing’s trailing edge directed more 

than half the engine’s exhaust gases over the upper surface of the faps. Another 10 percent of the 

engine’s exhaust was directed through small nozzles in the wingtips and tail to provide control at 

low speeds. Te manufacturer and the Royal Aircraft Establishment at Bedford made over 100 

experimental fights between 1963 and 1967. In 1969, the aircraft was shipped to NASA-Ames for 

full-scale wind-tunnel tests. Te jet fap was not developed further due to the impracticalities of 

the nozzle system’s complex ducting and its adverse efect on engine power. 

DeHavilland of Canada developed the augmentor wing concept in the late 1950s by incorporating 

a shroud assembly over the trailing-edge fap to create an ejector system that augmented the 

thrust of the nozzle by entraining additional air. In 1965, NASA and the Canadian government 

conducted a joint research program resulting in the C-8 augmentor wing airplane that NASAAmes and Canada subsequently used in a joint fight research program. Both the augmentor wing 

and the jet fap proved very efcient aerodynamically in that they produced a very large increase 

in wing lift for a given amount of engine thrust. In fact, internally blown jet-fap systems remain 

the most efcient form of powered lift for fxed-wing aircraft today. Unfortunately, they sufer the 

disadvantage of requiring internal air ducting that leads to increases in the weight, cost, complexity, 

and maintenance of the wing structure as well as reduced internal volume for other systems. 

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UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

Boeing-deHavilland augmentor wing jet short takeof and landing 

research aircraft. 

When it became obvious that internally blown fap airplanes would probably have unacceptable 

system penalties, NASA Langley started work in the 1950s on “externally blown” systems consisting 

of the externally blown fap (EBF) used with conventional pod-mounted engines, and the USB 

fap. Although such concepts may not achieve the levels of aerodynamic efciency exhibited by the 

internally blown concepts, the system penalties for these concepts might be much more acceptable. 

Langley frst carried out exploratory research on the EBF in 1956, and research on the USB fap 

started in 1957. Initial results appeared promising for both concepts. Langley staf conducted an 

extensive research program to develop technology for the EBF, but there were no indications of 

serious industry interest until Boeing incorporated it in its proposal for the CX-HLS (subsequently 

known as the C-5 transport) competition. Although Boeing did not win the C-5 contract, this 

show of interest by industry accelerated NASA’s research on the EBF and led to a rapid buildup of 

the technology base required for applications of the concept. As discussed in the author’s Partners 

in Freedom, the EBF concept, which John P. Campbell of Langley conceived and patented, was 

matured by years of intensive wind-tunnel research at Langley and subsequently applied by 

McDonnell Douglas to its YC-15 Advanced Medium STOL Transport (AMST) prototype in the 

1970s, and then by Boeing to today’s C-17 transport. Tis aircraft is the only U.S. production 

powered-lift fxed-wing airplane (excluding the vectored-thrust V/STOL AV-8). 

A USB aircraft produces high lift by exhausting jet engine efux above the wing in such a manner 

that it becomes attached to the wing and turns downward over the trailing-edge fap for lift 

augmentation in low-speed fight. In applications, a specially designed nozzle fattens the jet 

efux into a thin sheet. Key to the USB concept’s success is the Coanda efect, which Romanian 

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aerodynamicist Henri Coanda (1885–1972) discovered in 1930. Coanda found that a stream of 

fuid (such as air or water) emerging from a nozzle tends to follow the path over a curved surface 

placed near the stream if the curvature of the surface or angle the surface makes with the stream 

is not too sharp. 

Te USB concept’s aerodynamic performance can be equivalent to that of the EBF concept. Trust 

recovery performance is usually higher for the USB because the EBF is inherently penalized by 

thrust loss caused by the direct impingement of engine efux on the trailing-edge fap. Tis thrust 

loss will limit the fap setting selection fexibility. Te USB also ofers a critical advantage because 

objectionable noise levels generated during powered-lift operations are much lower for observers 

below the airplane. Reduced noise levels ofer substantial advantages for civil aircraft applications 

in compliance with regulatory noise restrictions near airports, as well as military applications where 

noise signatures play a key role in the detectability and “stealthiness” of aircraft for certain missions. 

USB aircraft: Te Boeing YC-14 (upper) and the NASA Quiet Short-Haul Research Aircraft (lower). 

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Use of an innovative USB-type confguration for civil transports may be compatible with shorter 

feld lengths (on the order of 3,000 ft) while retaining “good neighbor” noise characteristics. An 

additional operational advantage of the USB concept is the reduction of foreign object ingestion 

into the high-mounted engines. 

NASA and industry studied the USB concept extensively from the middle 1950s to the 1980s 

using an extensive variety of wind-tunnel investigations, static engine tests, and piloted simulator 

studies that culminated with the Boeing YC-14 prototype military transport and the NASA Quiet 

Short-Haul Research Aircraft (QSRA) technology demonstrator. NASA conducted this research 

principally at Langley, which later led to other eforts in collaboration with DoD, industry, and 

other NASA Centers. Te success of research leading to QSRA demonstrations of the USB concept’s 

viability and advantages has matured this technology to the point where it will be a primary 

candidate for any future commercial or military STOL aircraft. Te following discussion will 

highlight these past studies and examine some of the critical issues faced and solved during research 

at NASA Langley, resulting in a high degree of technology readiness. 

Challenges and Barriers 

Disciplinary Challenges 

Te use of propulsive lift provides STOL performance that signifcantly reduces feld-length 

requirements, lowers approach speeds for improved safety, and improves the versatility of fight 

path management for increased runway throughput by using steep or curved approaches. One of 

the most important metrics for STOL is the magnitude of maximum lift produced by the aircraft 

confguration. An STOL airplane does not actually conduct its landing approach at maximum lift 

conditions, it does so at considerably reduced lift because of the various angle-of-attack and engineout speed margins required for operational safety; however, the margins are based on specifed 

percentages of maximum lift conditions. It is therefore imperative that the USB concept provides 

not only high values of maximum lift, but also high levels of propulsive efciency. Te thrustweight ratio required for a representative STOL transport with a wing loading of about 80 lb/ft2 for 

a landing feld length of around 2,000 ft is about 0.5, which is approximately twice the installed 

thrust-weight ratio for conventional jet transports. Te STOL confguration must efciently use 

all of this relatively high thrust loading. 

Te powered-lift aerodynamic characteristics of the USB concept are critically dependent on 

engine nozzle-fow parameters and the geometry of the fap directly behind the engine (USB fap). 

In particular, the thickness of the jet efux and the radius of curvature of the USB fap surface 

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determine, to a large extent, the ability of the fap to turn the fow and maintain attached-fow 

conditions. Special features may be required for fattening and spreading of the engine exhaust 

to ensure the attached fow for generation of lift. Tese features may include a high-aspect-ratio 

(width much larger than height) fared nozzle exit, downward defection of the nozzle-exit fow 

(“kick down”) and the use of auxiliary fow control devices such as active BLC or vortex generators 

at the front of the USB fap. 

Signifcant trade-ofs between powered-lift efciency and cruise efciency will be required for USB 

confgurations. With engines located in an unconventional upper-surface confguration, unique 

aerodynamic propulsion-integration challenges exist to minimize cruise drag at high subsonic 

speeds. Flow separation and drag during cruise must be minimized by special geometry tailoring 

of the USB engine nozzles and nacelles, especially interference efects with the nacelles in close 

proximity to the body due to engine-out concerns. 

Aerodynamic loads imposed on the wing and fap structures by impinging jet fow must be predicted 

and accommodated by the aircraft structure. Tese loads take the form of relatively steady, direct 

normal- and axial-force loads imposed on the fap system, as well as large pressure fuctuations that 

can induce high vibration levels and acoustic loadings that may result in sonic fatigue. Te principal 

sources of turbulent pressure fuctuations can be generated within the engine by combustion, the 

mixing region of the core or bypass exhaust jet, and in the fow impingement region by boundary 

layers and separated fow. If dynamic loads induced by the pressure fuctuations are signifcantly 

high, sonic fatigue failures of secondary structures can occur, and the designer must give special 

attention to this issue during early design. 

Te USB designer must meet the requirements for structural heating issues caused by the engines 

mounted in close proximity to the wing’s upper surface. In the early 1950s when turbojet engines 

represented the only choice for powered-lift confgurations, heating issues were especially critical. 

Te advent of high-bypass-ratio engines having cooler bypass fow now permits heating barriers to 

be resolved with appropriate materials for STOL applications. 

In the area of stability and control, designers must address a number of issues inherent to the USB 

confguration. One obvious primary concern is the critical nature of controllability when one 

engine becomes inoperative during fight at high-power conditions, resulting in a major loss of lift 

on one side of the airplane and, as a result, a large rolling moment. A basic approach to minimize 

roll trim problems is by locating the engines as far inboard on the wing as possible, but special 

control devices may have to be used to aerodynamically balance the aircraft. 

170 Innovation in Flight 
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Te design of the horizontal tail’s size and location is especially critical for USB aircraft. Longitudinal 

trim is a major challenge because of large nose-down pitching moments produced by powered-lift 

faps at high thrust settings. Very large horizontal tails are required for trim at high-lift conditions, 

especially if the wing is unswept. In addition, the horizontal tail surface must be located in a 

high, relatively forward position to avoid the destabilizing efects of strong vortices generated at 

the wingtip or outboard end of the fap. Locating the tail forward removes it from the actions of 

the vortices and into a region of less destabilizing downwash. Te very low approach speeds and 

high thrust engines will also require a larger than normal vertical tail and possibly a more complex 

rudder system. 

Operational Challenges 

Te unique aerodynamic fow phenomena associated with powered-lift airplane confgurations 

require an assessment of potential problem areas during actual operations. For example, the efect 

of fight near the ground during the landing approach is an issue. Tis efect is typically favorable 

for conventional aircraft. Tat is, the presence of the ground provides a cushioning, or positive, 

ground efect that does not result in a serious performance or handling issue at a very critical 

time during the mission. However, the large turning of free-stream fow due to powered-lift 

operations may result in unconventional ground efects, resulting in loss of favorable ground efect 

or signifcant changes in trim or stability. Tus, validated experimental and analytical predictive 

tools are required early in the design stage. 

Arguably, the largest single obstacle to the implementation of STOL powered-lift technology for 

civil aircraft is the increasingly objectionable level of aircraft-generated noise for airports close to 

populated areas. Quiet engines are a key requirement for successful commercial aircraft applications; 

however, the powered-lift concepts produce additional noise that compounds the challenge. Te 

EBF, for example, produces a very large increase in aircraft noise—beyond that for the engines— 

when the faps are extended down into the jet exhausts. Te benefts gained by having the exhaust 

fow above the wing, as in the USB concept, include substantially reduced noise levels for groundbased observers during fyovers. Sufcient STOL performance may allow all low altitude operation 

to remain within the airport perimeter, thereby limiting public exposure to noise. 

Other operational issues for USB aircraft are representative of those faced by other poweredlift confgurations, especially providing crisp, coordinated control response at low speeds and 

satisfactory controllability and performance if an engine becomes inoperative. 

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Langley Activities 

Langley Research Center was recognized by the aeronautical community as an international leader 

in V/STOL research—especially in the conception and development of innovative powered-lift 

STOL confgurations—from the 1950s to 1976, at which time NASA Headquarters declared NASA 

Ames Research Center to be lead NASA Center role for rotorcraft and V/STOL. For almost 30 

years, friendly competition had existed between the two Centers in this technology area, resulting 

in accelerated development and maturity of the state of the art. It is generally recognized that 

Langley led the way in aerodynamic development of a large number of advanced STOL vehicle 

concepts, while Ames focused on fight and operational issues of STOL aircraft. 

Langley’s expertise in powered-lift STOL technology was internationally recognized, and its leaders 

maintained a closely coordinated in-house and contracted research program. Key individuals 

of this efort in the 1970s included John P. Campbell, Richard E. Kuhn, Joseph L. Johnson, 

Alexander D. “Dudley” Hammond, and Richard J. Margason. With unique world-class facilities 

that included the Langley 30- by 60-Foot (Full-Scale) Tunnel, the Langley 14- by 22-Foot (V/ 

STOL) Tunnel, large engine test stands, piloted simulators, and close working relationships with 

industry and DoD, the staf brought an immense capability and fresh innovation to the tasks at 

hand for powered-lift STOL research. 

Early Exploratory Research in the 1950s 

John M. Riebe and Edwin E. Davenport conducted initial Langley exploratory studies of blowing 

from nacelles on the upper surface of a wing for propulsive lift in the Langley 300 mph 7- by 10-

Foot Tunnel (also known as the Low Speed 7- by 10-Foot Tunnel and subsequently replaced by the 

Langley V/STOL Tunnel in 1970). Tomas R. Turner, Davenport, and Riebe quickly followed this 

work with further systematic tests. Te motivating factor for these experiments was the potential 

noise reduction provided by this approach for powered-lift confgurations, and the studies included 

several innovative concepts for trimming the large diving moments produced by the blown wing 

faps, such as a canard, a fuselage nose jet, and wingtip-mounted tail surfaces. Although limited in 

scope, results obtained from the tests, conducted in 1957, appeared promising. Te aerodynamic 

performance of the USB concept was comparable with that of the EBF, and preliminary farfeld noise studies of several diferent powered-lift model confgurations by Langley’s Domenic J. 

Maglieri and Harvey H. Hubbard showed the USB to be a potentially quieter concept because of 

the wing’s shielding efect . However, because the USB arrangement involved a radical change in 

engine location, away from the generally accepted underslung pods, and because there was at that 

time no special concern with the noise problem, research on the USB fap waned. In addition, the 

172 Innovation in Flight 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

Model confguration used in early Langley USB research in 1957 mounted to the ceiling of the 

Langley 300-mph, 7- by 10-Foot Tunnel. 

turbojet engines of that day had very hot exhaust temperatures and relatively heavy weight, making 

them impractical for providing the high thrust-to-weight ratios required for STOL applications. 

Interest in the USB concept at Langley was dropped after these initial studies. Research resumed 

in the early 1970s when it was becoming apparent that the EBF concept might have difculty 

meeting increasingly stringent noise requirements for civil applications, and lightweight, highbypass-ratio turbofan engines became available. 

Te 1970s 

In the early 1970s, a growing national interest in short-haul transportation systems for the United 

States began to emerge. As part of these activities, short-feld aircraft suitable for regional operations 

received considerable study, including assessments of the state of readiness of STOL technology 

and the economic and environmental impacts of such aircraft. During the decade, Langley focused 

extensive human and facility resources toward providing the disciplinary technology advances 

required to mature the short-haul STOL vision. 

In September 1970, Center Director Edgar M. Cortright appointed Oran W. Nicks to the position 

of Deputy Director of Langley. Nicks was a hard-driving, impatient leader who demanded 

innovation and action in Langley’s aeronautics and space programs. Although his previous NASA 

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UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

management positions had been in leadership of NASA lunar and planetary programs rather 

than aeronautics, Nicks engaged in his own research work in aerodynamics, composite materials, 

heat-resistant materials for re-entry, and other areas. When exposed to Langley’s research eforts 

on the EBF concept and growing concern over noise issues, Nicks was stimulated to explore 

other approaches to powered lift. He became intrigued with the potential capability of upper 

surface blowing and strongly advocated that it would be an optimum approach for the design of 

STOL aircraft. 

At that time, Langley operated two wind-tunnel facilities engaged in STOL research: the Langley 

Full-Scale Tunnel, under Marion O. McKinney, Jr., and the Langley V/STOL Tunnel (now the 

Langley 14- by 22-Foot Tunnel), under Alexander D. (Dudley) Hammond. Both organizations 

were heavily involved in the EBF concept’s development. Nicks met with John Campbell and 

personally tasked him and his organization to quickly investigate the potential aerodynamic 

benefts and issues of the USB concept applied to turbofan-powered transport confgurations. 

Te job of conducting this exploratory USB research—under the intense scrutiny of Nicks—was 

assigned by Campbell to Joseph L. Johnson, Jr., who formed a research team led by Arthur E. 

Phelps, III. Johnson, noted for his ability to quickly identify the benefts of innovative concepts by 

“getting 80 percent of the answer,” chose to use a rapid-response approach to the task by conducting 

tests of a model fabricated from existing EBF model components and performing the tests in 

a subsonic tunnel with a 12-ft test section (formerly the Langley Free-Flight Tunnel). Johnson 

used this tunnel as a quick-reaction, low-cost laboratory to explore innovative concepts in a low 

profle, timely manner. Phelps and his team used components from a powered semispan EBF jet 

transport swept-wing model having a full-span plain trailing-edge fap to create a USB model with 

a full-span leading-edge Krueger fap and a two-engine (tip-driven turbofan simulators) podded 

nacelle high-bypass-ratio turbofan engine confguration. Using an auxiliary fat defector plate 

attached to the nacelle exit, the team was able to thin the jet and turn the exhaust fow. Te use 

of BLC was also explored for additional fow control. Te results of this milestone investigation, 

conducted in 1971, showed that the high lift necessary for STOL operations could be achieved 

and that the performance was comparable with that of other powered-lift STOL concepts. Nicks 

was elated over the concept’s performance and gave his infuential support to further research and 

development activities for USB. 

Following this highly successful tunnel investigation, Langley geared up for accelerated USB 

research eforts in tunnels and with outdoor engine test stands. At the V/STOL Tunnel, William 

C. Sleeman, Jr., and William C. Johnson, Jr., conducted parametric studies to defne the optimum 

geometric and engine variables for USB performance. With superior fow quality over the 12-

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Sketch of upper-surface blown fap research model tested in 1971. 

ft tunnel used by Phelps in the 1971 tests, researchers were also able to obtain fundamental 

information on cruise drag, such as the efects of nozzle geometry for USB confgurations. Also, 

James L. Tomas, James L. Hassell, Jr., and Luat T. Nguyen conducted tunnel tests to determine 

the character of aerodynamic ground efects for USB confgurations and conducted analytical 

studies to defne the impact on aircraft fight path during approach to landings. 

Meanwhile, Johnson’s team changed its testing venue to the larger Full-Scale Tunnel, where they 

tested full-span USB models to provide additional performance information and pioneering data 

on the stability, control, and engine-out trim problems of USB confgurations. In 1972, Phelps 

and Charles C. Smith, Jr., conducted tests of a four-engine USB transport model, verifying the 

confguration’s aerodynamic STOL performance and investigating nozzle shape tailoring with 

contouring to direct the exhaust downward to the top of the wing for better spreading and fattening 

of exhaust fow over the wing and faps. Phelps and Smith determined that a T-tail empennage 

confguration provided longitudinal trim and longitudinal stability; and good lateral-directional 

stability was obtained for the confguration at all angles of attack below stall. 

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Full-span four-engine upper-surface blown model in the Langley Full-Scale Tunnel. 

Although the results of preliminary work with the USB concept were very encouraging, the results 

had been obtained at very low scale, and concern existed that higher Reynolds number testing 

might lead to conclusions that contradicted the small-scale results. Smith therefore conducted tests 

on a semispan, high-wing USB model assembled largely from components of a full-scale Cessna 

210 aircraft. Te investigation results indicated that the efects of Reynolds number were generally 

small for moderate to high-powered lift conditions. Once again, the aerodynamic efciency of yet 

another USB confguration was extremely high, and noise measurements indicated large benefcial 

shielding efects of the wing. 

In 1973, Joe Johnson formulated and led a multidisciplinary USB research program using a 

modifed Rockwell Aero Commander confguration. Te intent was to collect detailed information 

on subscale and large-scale models to provide data for aerodynamic performance, stability and 

control, efects of tail confguration, and the efects of actual turbofan engines on wing uppersurface temperatures and local acoustic loadings. In November 1973, Art Phelps conducted 

exploratory aerodynamic tests of an 8.8-ft span model of the confguration, providing design data 

for aerodynamic performance and engine-out trim strategies (leading-edge blowing and aileron 

defection on the failed-engine wing panel, and a spoiler on the active engine side). 

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Test of a modifed Cessna 210 in the Full-Scale Tunnel. 

With subscale aerodynamic results of the Aero Commander USB confguration in hand, the team 

turned its attention to obtaining data in the areas of structures, dynamic loads, and acoustics. An 

outdoor engine test-stand investigation and a tunnel test of a modifed full-scale Aero Commander 

airframe were used to attack these issues. James P. Shivers and Charles C. Smith, Jr., conducted the 

static test-stand investigation using an outdoor test site near the Full-Scale Tunnel. Te apparatus 

used in the study supported a JT15D-1 turbofan engine equipped with a candidate rectangular 

nozzle with an aspect ratio of 6.0 (width divided by height). Te engine and nozzle were oriented 

to direct the jet efux onto the upper surface of a boilerplate wing-fap system, which was mounted 

upside down to avoid ground efects. Te investigation’s primary objective was to establish a 

confguration that would provide acceptable static turning performance over the desired range of 

fap-defection angle without exceeding temperature constraints on the wing and faps. Tis test 

was coordinated with planning for the Aero Commander wind-tunnel test, and modifcation of the 

temperature environment measured during the test-stand study ensured an acceptable condition 

for the tunnel tests. 

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Engine test-stand investigation in preparation for tunnel tests of modifed Aero Commander airplane. Photo on right 

shows turning of fow around upper surface blown fap. 

Langley researcher Charles C. Smith, Jr., and technician Charles Schrum inspect the modifed Aero Commander 

USB research model in the Langley Full-Scale Tunnel. 

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In early 1974, Smith led a multidisciplinary test team to determine the aerodynamic performance, 

steady and laboratory aerodynamic loads, surface temperatures, and acoustic characteristics of the 

full-scale Aero Commander USB model. Te model had a full-span, leading-edge Krueger fap 

using boundary-layer control and three spanwise trailing-edge fap segments: an inboard Coanda 

fap located behind the engine, a double-slotted midspan fap, and a drooped aileron equipped with 

blowing boundary-layer control. Two Pratt and Whitney JT15D turbofan engines used to power 

the model were equipped with rectangular nozzles. Researchers designed the internal contours of 

the nozzle exits so that the exhaust fow was defected slightly downward toward the top of the 

wing, and defectors were attached to the nozzles to improve the spreading and turning of the 

jet exhaust. Te model was extensively instrumented, including pressures for aerodynamic loads, 

fuctuating pressure gauges, accelerometers, and thermocouples. Langley staf also made acoustic 

measurements to provide pioneering baseline noise data for a large-scale USB confguration 

having real turbofan engines. Tese acoustic tests included noise frequency and spectral content 

measurements for various fap confgurations and engine thrust settings. 

Te large-scale test results provided detailed engineering data and matured the technology base 

required to reduce risk for USB applications. Te aerodynamic performance of the model was 

especially impressive, as evidenced by a humorous experience that occurred during powered 

testing. At one point, the test team was in the process of evaluating the efectiveness of a horizontal 

T-tail for trim at high-power, low-speed conditions. Te puzzled test crew detected no noticeable 

change in aerodynamic pitching moment when the tail was installed on the model, even with large 

defections of the tail surface. After extended discussions over the unexpected result, the team 

surveyed the airfow in the tunnel test section behind the model and found that for high-power, 

low-speed conditions the aerodynamic turning of the USB concept was so powerful that it was 

turning the entire airfow from the wing down through the open-throat test section to the foor of 

the facility! 

Results of static load measurements by Boyd Perry, III, indicated the expected high values of 

normal force for spanwise locations directly behind the engine exhaust models. Tests with one 

engine inoperative indicated very little lift carryover from the powered to the unpowered side of the 

model. Temperature and vibration characteristics measured by James A. Schoenster and Conrad 

M. Willis indicated that the upper surface wing-skin temperatures and accelerations on the frst 

fap element were relatively insensitive to tunnel speed or angle of attack. Acoustic characteristics 

measured by John S. (Jack) Preisser confrmed the expected unsymmetrical noise radiation pattern 

due to wing shielding of the high-frequency engine noise and the production of low-frequency 

noise by jet-surface interaction. Results were in good agreement with other small- and large-scale 

model tests. 

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UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

In addition to the foregoing studies, Langley conducted several investigations of USB confguration 

dynamic stability and control characteristics. Since the early 1930s, Langley had developed and 

continually refned a wind-tunnel free-fight model testing technique to evaluate the fying 

characteristics of unconventional aircraft confgurations. Initially conducted in Langley’s Free-Flight 

Tunnel, these tests were relocated to the larger 30- by 60-ft test section of the Full-Scale Tunnel 

Technicians David R. Brooks and Benjamin J. Schlichenmayer prepare a free-fight model of a USB 

transport for tests in the Full-Scale Tunnel. 

in the 1950s. Te technique was used to evaluate the fying characteristics of USB confgurations, 

including engine-out conditions during which the development and efects of asymmetric stall 

are difcult to predict. Lysle P. Parlett led free-fight tests in 1973 for a four-engine confguration 

with pod-mounted tip-driven fan engines located on top of the wing in a twin-engine (Siamese) 

nacelle. Te results of the study showed that the longitudinal motions of the model were heavily 

damped and easy to control; however, the lateral motions of the model were difcult to control 

without artifcial stabilization because of a lightly damped roll-yaw oscillation (“Dutch roll”). With 

artifcial stabilization, the model was easy to fy. With one outboard engine inoperative, lateral trim 

could be restored through the use of asymmetric blowing on the wing leading edge and on the 

knee of the outboard fap segment. 

Dissemination of Information 

As Langley’s staf conducted the USB research in the early 1970s, representatives of industry, DoD, 

and the airlines continually visited for updates on the evolving technology. National interest was 

being stimulated by growing interest in civil short-feld transports and by an impending solicitation 

by DoD for a potential STOL replacement for the C-130 transport. In October 1972, NASA 

180 Innovation in Flight 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

sponsored an STOL Technology Conference at Ames Research Center to disseminate information 

on the Agency’s latest research results in aerodynamics, fight dynamics, loads, operational aspects, 

and powered-lift noise technology. Te primary topics of that meeting were the rapidly maturing 

STOL technologies and NASA’s experiences for EBF and augmentor-wing transport confgurations. 

However, Art Phelps and Danny R. Hoad of Langley presented summaries of the initial testing 

that had been conducted earlier that year for the USB concept. 

When the powered-lift community reconvened again at Langley for a Powered-Lift Aerodynamics 

and Acoustics Conference in May 1976, the major topic of discussion had shifted to USB technology 

and the potential noise benefts promised by the research conducted at Langley. During this time, 

STOL technology had received a tremendous injection of interest due to the Air Force’s interest in 

developing prototype advanced medium transports. When Boeing selected the USB concept for its 

candidate transport design, interest in this innovative approach to powered-lift capability reached 

a new intensity. 

Langley and the Boeing YC-14 

Development of the Boeing YC-14 AMST is covered in great detail in the excellent American 

Institute for Aeronautics and Astronautics (AIAA) case history publication by John K. (Jack) 

Wimpress and Conrad F. Newberry (see bibliography). Wimpress received the AIAA Design 

Award in 1978 for the YC-14’s conception, design, and development, and he was the only Boeing 

person to be with the YC-14 Program from its inception to its end. His publication contains 

an extremely interesting review of the program’s technical, programmatic, and administrative 

aspects. Te following section has summarized information from that document to indicate the 

interactions that occurred between Wimpress and Langley’s staf, along with the contributions of 

Langley’s research to the program. 

In July 1969, the Defense Science Board produced a report urging the use of prototyping by DoD 

to yield better, less costly, more competitive weapon systems. Deputy Secretary of Defense David 

Packard was a strong advocate of the prototyping approach and, in 1971, an Air Force committee 

recommended six systems as candidates, including a lightweight fghter (which subsequently 

evolved into the F-16) and the AMST. Later that year Boeing’s preparations for a response to 

an anticipated Air Force request for proposal (RFP) to design, build, and fight test an AMST 

Technology Demonstrator rapidly crystallized as the company began to develop its candidate for 

the competition. 

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UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

Boeing had accumulated considerable expertise in powered-lift concepts, having proposed the 

EBF concept for its unsuccessful C-5 competitor as previously discussed and having conducted 

fight research with NASA using the Boeing 707 prototype (known as the 367-80) modifed with 

sophisticated leading-edge devices and BLC on both leading- and trailing-edge faps. Along with 

most of the aeronautical community, Boeing had maintained an awareness of NASA’s development 

of various powered-lift concepts. In its RFP preparations, Boeing examined several powered-lift 

concepts, including boundary-layer control and, of course, the EBF. Early on, the company was 

convinced that a twin-engine design ofered considerable advantages for the AMST from the 

perspectives of cost and safety. BLC would not provide the level of lift required via engine bleed air, 

and the use of an underwing, pod-mounted twin-engine layout for an EBF confguration would 

require the engines to be located very close to the fuselage to minimize rolling and yawing moments 

if an engine became inoperative. Boeing was concerned that large aerodynamic interference 

efects would occur with such an arrangement, particularly at cruise conditions. Tus, Boeing 

was searching for a new concept that would permit the defection of jet fow behind a 

twin-engine arrangement. 

Boeing had analyzed the previously discussed exploratory upper-surface blowing tests published a 

decade earlier by Turner and was interested if NASA had since conducted additional research on 

the concept. While attending a conference on STOL aerodynamics at Langley in November 1971, 

Jack Wimpress was informed of the previously discussed semispan USB research being conducted 

by Joe Johnson and Art Phelps at the request of Oran Nicks in the 12-ft tunnel. An examination of 

the preliminary results by Wimpress revealed that the magnitude of lift generated was as high as had 

ever been seen for any powered-lift system. Johnson provided Wimpress with a set of preliminary 

data, which he enthusiastically took to the Boeing team working on the AMST’s presolicitation 

design. Wimpress was very excited about the Langley data because they were the key enablers for a 

twin-engine STOL confguration layout. In particular, with the engines on top of the wing, they 

could be placed close to the centerline of the airplane without causing large aerodynamic inference 

with the fuselage. Boeing immediately started to build wind-tunnel models to verify the NASA 

data with geometric and engine parameters more closely representing confgurations that Boeing 

was actually considering. By the end of 1971, Boeing was hard at work in several wind tunnels 

assessing and refning the twin-engine confguration. 

When the Air Force RFP for the AMST prototypes was released in January 1972, it called for 

the very impressive capability of operations into and out of a 2,000-ft semiprepared feld at the 

midpoint of a 500 nmi mission while carrying a 27,000-lb payload both ways. By comparison, 

the C-130 series in operation at that time required feld lengths almost twice as long to lift a 

27,000 lb payload. In February, Wimpress visited Dick Kuhn, Dudley Hammond, Jim Hassell, 

182 Innovation in Flight 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

and others at Langley to brief them on Boeing’s progress for the USB confguration, and he briefed 

Langley’s high-speed performance researchers regarding approaches to minimizing drag of the 

over-the-wing engines. 

Following the submittal of its proposal in March, Boeing conducted many wind-tunnel and 

engine test-stand investigations to refne its proposed design and to identify and solve potential 

problems. In November, Wimpress again visited Langley for an update on NASA’s USB research 

activities. Joe Johnson and Dudley Hammond both reported on testing being conducted in their 

organizations and showed Wimpress experimental data that verifed the high-lift performance that 

Boeing had submitted in its proposal. 

On November 10, 1972, the Air Force selected Boeing and McDonnell Douglas as contractors 

to work on the AMST prototypes. At the request of the Air Force, Langley’s Dick Kuhn had 

participated in the evaluation process for the AMST competition. Following the contract award, 

Boeing launched an aggressive development program to actually design the airplane. Considerable 

eforts were required for the development of an acceptable USB nozzle, and a major technical 

surprise occurred when Boeing discovered that the forward fow over the airplane during lowspeed operations had a degrading efect on the USB fap, reducing the jet spreading and causing 

separation ahead of the fap trailing edge. Tis phenomenon had not been noted in earlier NASA 

or Boeing wind-tunnel testing. Results from those earlier tests had led to the conclusion that 

forward speed efects would not signifcantly impact the fow-turning capability of the nozzle. 

Boeing added vortex generators to the YC-14 confguration to re-energize the fow and promote 

attachment on the USB fap during STOL operations. Te vortex generators were extended 

only when the USB fap was deployed beyond 30° and were retracted against the wing surface 

during cruise. 

Boeing adopted a supercritical airfoil for the wing of the YC-14 based on internal aerodynamic 

research following the 747’s design. Initially, senior aerodynamicists at the company were reluctant 

to accept such a radical airfoil shape. After reviewing ongoing supercritical wing research at 

Langley led by Richard T. Whitcomb, they were impressed by the performance of a supercritical 

airfoil applied to a Navy T-2C aircraft in a research program by Langley (see Concept to Reality 

for additional information on Whitcomb’s supercritical wing activities). Confdence in the design 

methodology for the new family of airfoils was provided by close correlation of wind-tunnel 

predictions and actual fight results obtained with the T-2C. With the NASA data in hand, Boeing 

proceeded to implement the supercritical technology for the YC-14 and for its subsequent civil 

commercial transports, including the 777. 

Innovation in Flight 183 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

During the development process, Boeing was faced with determining the size of the horizontal tail 

and its placement on the confguration. Te initial proposal airplane had a horizontal tail mounted 

on the end of a long extended body atop a vertical tail with relatively high sweep. However, 

as the design evolved it became apparent that the proposal confguration would not adequately 

accommodate the large nose-down pitching moments of the powered-lift system or ground efects. 

Boeing examined the parametric design information on longitudinal stability and trim that 

Langley tests had produced in the Full-Scale Tunnel and the V/STOL Tunnel, indicating that it 

was very desirable to place the horizontal tail in a position that was more forward and higher than 

the position that Boeing had used for the proposal confguration. Tese Langley data provided 

critical guidelines in the tail confguration’s revision for the YC-14’s fnal version. 

By December 1975, Langley had negotiated with Boeing to obtain full-scale data on a USB high-lift 

system. Boeing conducted full-scale powered ground tests of a complete YC-14 wing-fap-fuselage 

segment at its Tulalip test facility to evaluate the efectiveness and noise levels of its powered system. 

During the tests, sound levels and pressure distributions were measured by Boeing over the USB 

fap and the fuselage next to the fap. Tese data were made available to Langley under the special 

research contract. Langley’s interest was stimulated in part by the fact that the engine nozzle of the 

YC-14 design incorporated a D-nozzle (a semielliptical exit shape), which difered from the highaspect-ratio rectangular nozzles that had been used at Langley in the full-scale Aero Commander 

tests previously discussed. With the full-scale YC-14 data in hand, Langley proceeded with a test 

program to determine the adequacy of subscale models to predict such information, including the 

development of scaling relationships required for the various technologies involved. 

Under the leadership of Jim Hassell, 0.25-scale model static ground tests of the Boeing YC-14 

powered lift system were conducted at the outdoor test site near the Full-Scale Tunnel for correlation 

with full-scale test results. Te model used a JT-15D turbofan engine to represent the CF6-50D 

engine used on the YC-14. Te tests included evaluations of static turning performance, static 

surface pressure and temperature distributions, fuctuating loads, and physical accelerations of 

portions of the wing, faps, and fuselage. Results were obtained for the landing fap confguration 

over a range of fan pressure ratio for various ground heights and vortex generator modifcations. 

Te YC-14 prototype’s frst fight occurred on August 9, 1976. YC-14 and YC-15 airplane capabilities 

were evaluated in a fight test program at Edwards Air Force Base in early November 1976. By the 

end of April 1977, the very successful YC-14 Program had exceeded all its projected goals in terms 

of fight hours, test conditions accomplished, and data accumulated. Te performance goals were 

met in terms of maneuvering, feld length, and touchdown dispersion. Following the fight test 

program, Boeing demonstrated the YC-14 to U.S. forces in Europe, including an appearance at the 

184 Innovation in Flight 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

James L. Hassell inspects the 0.25-scale model of the YC-14 USB arrangement. 

Note vortex generators deployed on USB fap. 

Paris Air Show in June. Te airplane impressed the crowds at the air show, performing maneuvers 

formally considered impossible for a medium-sized transport. After the European tour, the YC14 arrived for a demonstration at Langley Air Force Base on June 18, 1977, where its outstanding 

STOL capability and crisp maneuvers stunned not only the Air Force observers but many of the 

NASA-Langley researchers who had participated in USB studies that helped contribute to the 

design and success of this remarkable airplane. 

Te YC-14 fight test program ended on August 8, 1977, exactly 1 year after it began. Unfortunately, 

the anticipated mission of the AMST did not meet with Air Force funding priorities at the end of 

the fight evaluations (the B-1B bomber was by then the top Air Force priority), and the AMST 

Program ended. In 1981, the Air Force became interested in another transport, one having less 

STOL capability but more strategic airlift capability than the AMST YC-14 and YC-15 airplanes. 

Tat airplane was ultimately developed to become today’s C-17 transport. Te two YC-14 prototype 

aircraft were placed in storage at the Davis Monthan Air Force Base, and one was later moved to 

the Pima Air Museum in Tucson, Arizona, where it is displayed next to one of the YC-15 aircraft. 

Innovation in Flight 185 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

One of the two Boeing YC-14 prototype aircraft. 

Te Boeing YC-14 demonstrates its low-speed maneuverability. 

186 Innovation in Flight 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

Te Quiet Short-Haul Research Airplane 

In 1972, Langley advocates had led a growing NASA interest in developing a contract for a highperformance STOL research airplane to be called the Quiet Experimental STOL Transport 

(QUESTOL). NASA envisioned a USB research airplane that would push the boundaries of 

technology further than the requirements of the AMST Program. Langley had examined the 

possibility of using a modifed twin-engine high-wing B-66 Air Force bomber for the confguration. 

However, this study was subsequently terminated by a new focus for a USB demonstrator aircraft. 

In January 1974, NASA began a program known as the QSRA Project. Te objective of the 

program was to develop and demonstrate the capabilities of a low-cost, versatile, quiet jet research 

aircraft with next-generation STOL performance. Te powered-lift system selected for the QSRA 

was a four-engine USB concept designed to yield high lift and very low sideline noise levels. In 

addition to demonstrating outstanding aerodynamic lift efciency, the aircraft would be used in 

conducting terminal-area research, including operations from feld lengths ranging from 1,500 ft 

to 4,000 ft with sideline noise levels of only 90EPNdB on landing approach. 

Te QSRA aircraft design was based on a modifed deHavilland C-8A Bufalo airframe, and the 

program was led by Ames with Boeing as the primary contractor. Although the research airplane 

operated only in the low-speed regime, the wing and nacelles were designed by the team to be 

conceptually representative of a high-speed commercial transport aircraft. Development of the 

airplane included tests in the Ames 40- by 80-Foot Tunnel and extensive research on the Ames 

Flight Simulator for Advanced Aircraft. First fight of the airplane took place on July 6, 1978. Te 

QSRA was tested extensively at Ames, including joint operations with the U.S. Navy in 1980 from 

the U.S.S. Kitty Hawk aircraft carrier. Te QSRA conducted 37 touch-and-go landings and 16 

full-stop takeofs and landings on the carrier without the use of an arresting gear during landing 

or a catapult during takeof. Noise levels of 90EPNdB were obtained at sideline distances of 500 

ft, the lowest ever obtained for any jet STOL design. Te acoustic signature of the airplane was 

highly directional, being projected in a small, 35° cone in front of the aircraft. Most observers were 

comfortable standing next to the QSRA without ear protection during powered operation. 

Te low-speed maneuverability of the QSRA was demonstrated by a turn radius of only 660 ft at 

an airspeed of 87 kts with the critical engine failed. To illustrate the maneuver capability, assume 

civil operations from a terminal with parallel runways. Te QSRA could take of, climb to safe 

altitude, perform a climbing curved departure, and depart with a 180° change in heading while 

operating within the airspace over the center of the terminal and within the boundary between the 

two parallel runways. Terminal area operations of this type would alleviate the dangers of aircraft 

proximity and the nuisance of noise as problems for surrounding communities. Te aircraft also 

Innovation in Flight 187 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

Te NASA-Ames Quiet Short-Haul Airplane lands on the carrier Kitty 

Hawk without arresting gear in 1980. 

demonstrated high descent paths as large as 17° during approach (faring out to 6° near touchdown) 

compared with the 1.5° fown by conventional airliners. 

With the 1976 transfer of rotorcraft and V/STOL technology from Langley to the Ames Research 

Center decreed by NASA Headquarters, Langley researchers played a minor role in QSRA 

activities, and all STOL research at Langley essentially was terminated. However, the revolutionary 

capabilities indicated by the early research at Langley had been vividly demonstrated by the research 

airplane including a breathtaking performance at the Paris International Air Show in 1983. 

Foreign Applications 

Te Soviet technical community characteristically followed development of the AMST prototype 

aircraft and ultimately produced the An-72 aircraft (North Atlantic Treaty Organization code 

named Coaler) whose features very closely resembled the YC-14. Te frst prototype few on 

December 22, 1977, and the aircraft entered service in 1979. A few years later, a derivative version 

known as the An-74 appeared at the Paris Air Show. 

In 1975, the advisory board to the Japanese government’s Science and Technology Agency (STA) 

suggested that an STOL experimental aircraft be developed. Consequently, the Japanese National 

188 Innovation in Flight 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

Aerospace Laboratory (NAL) embarked upon the Quiet STOL project in 1977. For this research, 

a Kawasaki C-1 transport aircraft was heavily modifed into an STOL aircraft with modifcations 

being completed in 1985. Designated ASKA, the modifed aircraft was ftted with four Japanesedeveloped turbofan engines on the wing’s upper surface and used a USB concept similar to the 

YC-14. Flight testing occurred between October 1985 and March 1989. 

Status and Outlook 

Te remarkable technical ingenuity and progress made by NASA and industry on the USB concept 

during a very short time in the 1970s stands as one of the most signifcant accomplishments of 

the NASA aeronautics program. Te conception of an extremely efcient powered-lift principle, 

the development of design data, the discovery of potential problems and development of solutions, 

and the fight-demonstrated capabilities of research vehicles involved NASA research capability at 

its best. Fundamental data were available when industry and DoD needed it. Te advantages of 

the USB compared with other powered-lift concepts—especially in reduced noise—continue as a 

viable reason for considering this concept a primary candidate for future military and civil aircraft 

requiring short-feld capability. 

As a result of NASA’s pioneering work, it is generally accepted that the technology challenges 

to develop medium and large transport aircraft having STOL capabilities have been met. Dayto-day demonstrations of the military C-17 EBF airplane have provided tremendous confdence 

in the engineering community and the military users of powered-lift technology. At the 2002 

International Powered-Lift Conference in Williamsburg, Virginia, the scope of papers presented 

by the engineering community emphasized the need for reexamining the potential benefts of 

powered lift for the civil transportation system rather than disciplinary technologies that have 

already been demonstrated. 

Unfortunately, from a commercial transport perspective, there is still a very limited current 

requirement for medium or large STOL airplanes in the U.S. transportation system. Airport 

space and runways have not been expensive enough to warrant compromising the capability of 

the conventional commercial transport to any extent to achieve very short feld lengths. City hub 

and spoke operations continue to be the emphasis of today’s air transportation system, although 

trafc delays, congestion, and unavailability of more fexible travel schedules continue to be a 

hindrance to the traveler. Te issue of noise generated by powered-lift aircraft continues to surface 

as a challenge to the application of the technology. Te USB concept provides an approach to attack 

this issue, and recent experiences with advanced propulsion system concepts, such as extremely 

high-aspect-ratio nozzles for stealth benefts on military aircraft, might be pursued for advanced 

Innovation in Flight 189 
UPPER SURFACE BLOWING: EFFICIENT, QUIET, SHORT TAKEOFF AND LANDING 

USB applications. Another interesting concept currently under study is the use of many small 

“distributed” propulsion units that spread out the induced circulation lift across the wing span. It 

is expected that many small engines would generate noise at high frequencies, which typically mix 

with entrained fow much faster and might further reduce the noise for powered-lift systems. 

A currently emerging NASA interest in developing the technology required for futuristic runwayindependent fxed-wing transport aircraft addresses the benefts that can accrue by the operation 

of STOL aircraft. If, as predicted by the FAA, commercial air trafc continues to increase in the 

new millennium, a fresh look at the ability of STOL technology to relieve limitations of the future 

transportation system will be in order. Tanks to research conducted by NASA and its partners 

over three decades ago, the technology appears to be ready for applications. 

190 Innovation in Flight 
Control of Aeroelastic Response: Taming the Threats 

Concept and Benefts 

Te fexible characteristics of aircraft structures can result in dramatic, sometimes catastrophic, 

behavior of civil and military aircraft. When the inherent structural fexibility of an airplane 

interplays with the aerodynamic, gravitational, and inertial forces and moments acting on it, steady 

or dynamic defections or oscillatory motions of aircraft components can result. Such interactions 

can cause reduced structural life of airframe components, undesirable coupling with control 

systems, severe reductions in ride quality, and even abrupt and violent structural failures. Te 

three most important aeroelastic phenomena for aircraft designers are loads (static and dynamic), 

futter, and bufet. Te subject of loads is concerned with the a structural airframe’s ability to 

accommodate external loads encountered during the fight envelope, with emphasis on the 

airplane’s performance, stability, control, and structural integrity. Flutter is a dynamic aeroelastic 

Photographs of B-52 airplane on the ground and in fight graphically show the structural 

fexibility of the wing. 

Innovation in Flight 191 
CONTROL OF AEROELASTIC RESPONSE: TAMING THE THREATS 

phenomenon that involves the interactions of a structure’s elastic and inertia characteristics with 

the aerodynamic forces produced by the airfow over the vehicle. It is a self-excited oscillation of 

the aircraft structure involving energy absorbed from the airstream. When an aircraft’s elastic 

structure is disturbed at speeds below futter speed, the resulting oscillatory motions decay. 

However, when the structure is disturbed at speeds above futter speed, the oscillatory motions 

will abruptly increase in amplitude and can rapidly lead to catastrophic structural failure. In some 

instances, futter oscillations are limited to just a single airplane component such as the wing, 

while in other instances the oscillations may be considerably more complex, involving coupling 

of natural structural modes of wing, fuselage, and empennage motions. Bufet is a randomly 

varying structural response often triggered by intense and chaotic aerodynamic forcing functions 

associated with stalled or separated fow conditions. Fluctuating pressures present during 

bufet conditions can cause highly undesirable responses from wings, fuselages, pod-mounted 

engine nacelles, and empennages. Dynamic loads experienced during bufet can lead to pilot 

fatigue or structural fatigue, resulting in serious reductions in the anticipated structural life of 

airframe components. 

Te traditional solution to these aeroelastic issues has been primarily to stifen the airframe structure, 

thereby either eliminating undesirable excitation of structural characteristics or ensuring that the 

undesirable phenomena occur only at conditions beyond the fight envelope. Unfortunately, this 

“passive” approach involves adding additional structure to stifen that which is already sufciently 

strong to carry normal fight loads. Tese weight penalties adversely afect manufacturing and 

acquisition costs, mission performance, and add to operational costs throughout the life of 

the airplane. 

Te state of the art in aeroelasticity has steadily advanced to the point that, by the 1960s, many 

fundamental physical phenomena, predictive methodologies, and processes for the resolution of 

problems had been identifed for conventional airplanes. Researchers began turning attention 

to the use of “active” controls technology (ACT) to favorably modify the aeroelastic response 

characteristics of aircraft to permit structural weight reduction, optimal maneuvering performance, 

and multimission capability. As the name implies, ACT uses aircraft control surfaces that are linked 

to a computer and sensors in a manner to automatically and immediately limit any unwanted 

motions or aerodynamic loads on the aircraft structure. 

Te potential benefts of active control of aeroelastic response are signifcant. For example, if 

the stifening requirements for wings can be reduced, the weight reduction could be absorbed 

in additional passengers and payload revenues for commercial transports. If an active futter 

suppression system was incorporated in the design of an advanced confguration, such as a highly 

192 Innovation in Flight 
CONTROL OF AEROELASTIC RESPONSE: TAMING THE THREATS 

swept supersonic transport, the substantial weight savings translates into increased range or 

payload, with a signifcant reduction in airplane direct operating costs. Active control of tail bufet 

for highly maneuverable fghter aircraft could result in weight savings, increased structural service 

life, and reduced maintenance and cost. 

Te transition of technology for efective control of aeroelastic response from laboratory experiment 

to extensive feet applications has involved a few success stories, but the general application to 

aircraft to date is relatively limited. For example, gust load alleviation using active control laws 

on commercial transports has only been implemented on aircraft such as the Lockheed L-1011 

and the Airbus A320, and active futter suppression has not achieved operational status on any 

civil aircraft. In the early 1970s, the frst practical demonstration of active futter suppression 

was carried out by the U.S. Air Force in its Load Alleviation and Mode Stabilization (LAMS) 

Program. A Boeing B-52 bomber was equipped with an active futter suppression system that was 

demonstrated during fight tests to increase the airplane futter speed by at least 10 kts. As will be 

discussed, another success story has been the development and application of an active system by 

McDonnell Douglas (now Boeing) to suppress an unacceptable limit-cycle structural oscillation 

exhibited by preproduction F/A-18 aircraft with certain external store loadings. Te system was 

subsequently incorporated into the production control system for feet F/A-18 aircraft. 

Challenges and Barriers 

Disciplinary Challenges 

Te primary disciplinary challenges for active control of aeroelastic response are requirements 

for highly accurate predictions of critical aerodynamic and structural phenomena at test fight 

conditions of interest; reliable prediction and analysis methods for the aeroelastic interactions 

that occur; and the design of robust, redundant control systems that are tolerant to parametric 

uncertainties. Te consequences of inadequate or invalid design methods are not acceptable, and 

concepts such as active futter suppression are viewed as inherently high risk. 

Active control of aeroelastic response is dependent on the specifc confguration and fight condition 

under analysis. For example, design of an active futter suppression system for a commercial 

transport, with a typical high-aspect-ratio wing, may focus on the interactions between the frst 

few structural vibration modes of the wing, usually relatively simple combinations of bending and 

twisting of the structure. However, futter mechanisms of a low-aspect-ratio fghter design will be 

more complicated because the structural vibration modes are more complex, including interactions 

of basic wing motions with the motion of a variety of diferent pylon-mounted external stores. 

Innovation in Flight 193 
CONTROL OF AEROELASTIC RESPONSE: TAMING THE THREATS 

Paramount to all these design challenges is the difculty of precisely predicting the complex, steady 

and unsteady, aerodynamic characteristics present at the high subsonic or transonic conditions 

where the onset of futter becomes most critical. 

Operational and Economic Challenges 

Operational issues pose special challenges for active control systems. Clearly, systems used for futter 

suppression must be reliable and designed to be totally failsafe, with requirements similar to those 

for automatic control systems used in the automatic stabilization and control of highly unstable 

airplanes. Te design of such systems clearly calls for redundancy, and multiple systems will be 

required for safety. Other concerns for active controls include manufacturing and maintenance 

costs and additional complexity. Te active control system will have to be as reliable as the structure 

that it replaces. 

As is the case for any advanced technology, the use of active control for tailoring aeroelastic 

response will be successful only if the potential benefts are feasible from a cost/beneft perspective. 

Te requirements for robust, redundant sensors, maintenance schedules and costs, environmental 

protection, and certifcation compliance and costs must be favorably addressed before widespread 

application of the technology can occur. 

Langley Activities 

Langley Research Center is the lead NASA Center for research in structures and materials, and 

it is internationally recognized as a world leader in aeroelastic research. Tis reputation stems 

from a rich legacy of contributions in technology, cooperative research, consultation and problem 

solving, and unique experimental facilities. Langley’s eforts in structures, materials, and loads as 

an NACA laboratory prior to 1958 are well documented and will not be discussed herein. Rather, 

several major contributions and research activities since the early 1960s are highlighted as examples 

of the critical role Langley researchers and facilities played in advancing the state of the art in active 

and passive control of aeroelastic response. Although Langley’s research accomplishments have 

included both fxed-wing and rotary-wing vehicles, the discussion is limited to research on fxedwing aircraft. Two areas of activities are overviewed: contributions and ongoing aeroelastic research 

over the last 35 years by the staf and facilities of the Langley 16-Foot Transonic Dynamics Tunnel 

(TDT); and the NASA ACT Program of the late 1970s. Te discussion draws extensively on the 

excellent summaries of Boyd P. Perry, III, and Ray V. Hood, Jr. (see bibliography). 

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Te 16-Foot Transonic Dynamics Tunnel 

Without question, the centerpiece facility for Langley’s research in aeroelasticity is the Langley 

TDT. Converted from an existing 19-Foot Pressure Tunnel, with operations commencing in 

1960, it is the only facility in the world capable of studying a full range of aeroelastic phenomena 

at transonic speeds. Research in aeroelasticity in the TDT ranges from futter clearance studies 

of new vehicles using aeroelastic models to the development and assessment of new concepts to 

control aeroelastic response, and to the acquisition of unsteady pressures on wind-tunnel models 

for providing experimental data to validate unsteady theories. Analytical methods are developed 

and validated to solve the aeroelastic problems of fxed- and rotary-wing vehicles, including the 

control of instabilities, loads, vibration, and adverse structural response. 

Te TDT is a closed-circuit continuous-fow wind tunnel capable of testing with either air or R134a refrigerant as the test medium over a Mach number range from 0 to 1.2. Te R-134a gas 

is very attractive for use in wind-tunnel studies of aeroelastic phenomena because, as compared 

with air, it has a low speed of sound and high density. Since the frst test was conducted in 1960, 

the tunnel’s testing capabilities have been continuously expanded by introducing a number of 

new features, such as airstream oscillators, sophisticated data acquisition systems, a variety of 

model mounting and suspension systems (including a two-cable suspension system for full-span 

“free-fying” futter models), and excellent model-monitoring visual systems. Many very signifcant 

contributions of the tunnel and its staf to military and civil aircraft programs are summarized 

in NASA SP-2000-4519 Partners in Freedom and NASA SP-2003-4529 Concept to Reality 

(see bibliography). 

Te Langley 16-Foot Transonic Dynamics Tunnel. 

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After almost 45 years of operations and over 500 tests, the TDT staf has led the way as 

experimental aeroelasticity reached relative maturity. Tis progress has involved an intense coupling 

of experimental and computational research including the use of advanced CFD and advanced 

control theory. However, the research required to mature and extend the use of active controls for 

aeroelastic response has not diminished. Understanding and predicting the efects of transonic 

aerodynamic phenomena such as shock waves, fow separation, viscosity, and the interactions of 

these complex aerodynamic features with active control systems in controlling aeroelastic response 

are still major challenges. 

Flutter Suppression 

Delta Wing Flutter Suppression Study 

Te frst practical demonstration of an active futter suppression system was accomplished during 

the early 1970s in TDT tests. Tis efort was fueled by futter concerns of large SST aircraft. 

Most studies had shown that large SST confgurations, such as those of interest in the United 

States, had relatively severe futter problems, requiring the addition of thousands of pounds of 

structural weight to provide the stifness needed to ensure that futter occurred well outside the 

operating envelope. Conceptually, an active futter suppression system would require the addition 

of perhaps only a few hundred pounds of added weight as opposed to the thousands of pounds 

of a passive system. Because there was little information available on the design, implementation, 

and operation of active futter suppression systems, a delta wing futter suppression study was 

undertaken. Te research team was lead by Langley’s Maynard C. Sandford with critical support 

provided by a number of other Langley researchers (especially Irving Abel and David C. Grey) and 

from Boeing-Wichita under contract. 

In the benchmark 1971 experiments, a simplifed 1/17-scale semispan model representative of 

the Boeing SST (2707-300) wing confguration was mounted to the wall of the TDT with a 

rigid sidewall-mounting block used to simulate the fuselage faring. Te model was equipped with 

both leading- and trailing-edge control surfaces as well as high-fneness-ratio bodies on the wing 

lower surface that were used to simulate the mass properties of engine nacelles. Te model also 

incorporated advanced, miniaturized hydraulic actuators to move the active control surfaces. 

Te development of these actuators was a signifcant advance in the state of the art for model 

construction and surface actuation at that time. 

Te futter suppression systems implemented were based on the aerodynamic energy concept 

developed by Elihu Nissim, who worked at Langley as a postdoctoral research fellow. Tree control 

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laws were studied, including Nissim’s basic method and two variations developed by Langley 

researchers. Two of the systems used both leading- and trailing-edge control surfaces, whereas the 

third system used only the trailing-edge surface. Te control laws were implemented on an analog 

computer located in the wind-tunnel control room. Response of the model was sensed by two 

accelerometers located at the same outboard station as were the control surfaces. Model response 

signals were routed to the analog computer for processing through the control laws. Te processed 

signals were then routed to servo valves that provided hydraulic power to the actuators and caused 

them to move in such a way that the aerodynamic forces generated by the motion of the surfaces 

added damping to the wing, thus preventing futter from occurring. 

When the “open-loop” futter characteristics of the model with the suppression control system of 

were compared with results obtained with the suppression control activated, it was found that all 

three active control systems demonstrated signifcant increases in the dynamic pressure for futter 

onset at transonic speeds (Mach = 0.9). Te increase in futter dynamic pressure ranged from 11 to 

30 percent for the systems. 

In addition to dramatically demonstrating the potential of active control systems to extend 

futter speeds, this investigation made major contributions to the fundamental understanding of 

aerodynamic prediction methods for complex transonic fows and the understanding of inertial 

coupling between the control surfaces and the main wing. In retrospect, this particular investigation 

is widely regarded as a landmark study and a major contribution to subsequent advances made in 

active control of aircraft aeroelastic responses. 

Wing-Store Flutter Suppression 

YF-17 Program 

High-performance military attack aircraft typically carry vast arrays of air-to-air or air-to-ground 

weapons on wing-mounted pylons. Te substantial weight and aerodynamic characteristics of 

these external stores can dramatically change the aeroelastic characteristics and structural response 

characteristics of wings, resulting in unacceptable futter constraints or airplane motions. Each of 

the literally hundreds of diferent combinations of external store confgurations is a new dynamic 

system with its own set of futter characteristics. In particular, the onset of futter can occur at 

lower airspeeds than the baseline aircraft, thus restricting the aircraft’s operating envelope and 

limiting military operations. It appeared that active control techniques might be applicable to 

the wing-store futter problem. Initial U.S. eforts to develop active wing-pylon-store futter 

suppression systems were begun by the military with the F-4 airplane in the early 1970s. Langley 

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has participated extensively in domestic and international research programs to advance and 

validate store-induced futter design methods, including assessments of active control systems for 

wing-store futter suppression. 

In 1977, Langley researchers began a cooperative program with Northrop and the Air Force Flight 

Dynamics Laboratory (AFFDL) to conduct long-term wind-tunnel investigations in the Langley 

TDT of several concepts for wing-store futter suppression. Te program’s focus was a 30-percent 

scale semispan, aeroelastic model of the YF-17 Lightweight Fighter prototype consisting of a wingfuselage and horizontal tail. Te model was mounted on a special support system that provided 

rigid-body pitch and plunge freedoms. In addition to having powered leading- and trailing-edge 

control surfaces, the model was equipped with three diferent external store confgurations that 

produced widely diferent futter characteristics (futter frequency, coupling of structural modes, 

and relative violence of the futter mode). 

Moses G. Farmer led the cooperative test team during the TDT test program. During initial 

testing in 1977, results demonstrated that active futter suppression could be achieved for the 

signifcantly diferent aeroelastic characteristics of the wing-store confgurations tested and that, 

for the frst time, the use of only leading-edge control surfaces could achieve suppression. In a 

second series of TDT tests conducted in 1979, more sophisticated multiple control loops were 

conceived and assessed for further expansion of the futter-free envelope. Concentrating on the 

store confguration with the most violent futter mode, researchers developed an innovative “futter 

stopper” electromechanical internal system to rapidly change the distribution of store mass in such 

a manner as to decouple the critical elastic modes. Tis unique system proved a valuable tool in 

suppressing futter of the model during the tunnel test. 

Trough the auspices of an Air Force data exchange agreement with certain European nations, 

an international assessment of control laws developed by individual organizations was conducted 

using the YF-17 model in the TDT. European participants included British Aerospace and 

the Royal Aeronautical Establishment (RAE) from the United Kingdom, the Ofce National 

d’Etudes et de Recherches Aerospatiale (ONERA) from France, and Messerschmitt-BolkowBlohm GmbH (MBB) from Germany. Substantial information was mutually shared on the efects 

of suppression system design, including the number of sensors and control surfaces used. Some 

concepts produced extremely efective futter suppression, including one that was tested to a 

dynamic pressure 70 percent above the passive futter dynamic pressure. Many notable frsts were 

achieved in this international program, including demonstrations of the ability to switch between 

futter-suppression control surfaces above futter speeds without undesirable transients, and the 

validation of design procedures and techniques. 

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Members of the international active store futter suppression team pose with the YF-17 model in the Transonic 

Dynamics Tunnel. 

Te initial collaborative wing-store futter suppression activities in the TDT had been based on 

the use of analog controllers, but the advances and application of digital controllers in an adaptive 

manner was the next target of researchers. During 1981, some control laws previously implemented 

on an analog computer were converted to a digital computer and retested. In 1982, another phase 

of investigations of digital controllers was conducted with the objective of demonstrating adaptive 

futter suppression. In this approach, the controller was required to discriminate between futter 

modes and select the appropriate control law with changes in fight condition. Te tests were 

highly successful and proceeded to the point of demonstrating the release of a wingtip-mounted 

store designed to transform the model confguration from a stable condition to a violent futter 

condition. Te adaptive controller rapidly recognized the unstable behavior, implemented a new 

control law, and stabilized the model in a fraction of a second. 

Te highly successful YF-17 store futter suppression program extended through seven diferent 

entries in the TDT and is known as a critical NASA accomplishment in the feld of aeroelasticity. 

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F-16 Program 

Te General Dynamics YF-16, winner of the Air Force’s Lightweight Fighter Program, was 

initially conceived as a highly agile, lightweight fghter with emphasis on close-in air-to-air combat 

maneuverability. As the Air Force developed the airplane into today’s F-16, mission requirements 

for the aircraft changed to emphasize the air-to-ground mission, thereby leading to an extensive 

application of external stores to the confguration. Early in the airplane’s development program, 

the Air Force requested Langley to support the futter clearance requirements for fight testing by 

conducting traditional futter tests in the Langley TDT. Subsequently, over 18 diferent TDT test 

entries were conducted for the F-16 to cover futter characteristics of the basic airplane and the 

airplane with external stores. With the very large number of potential external stores and aeroelastic 

characteristics to be encountered with the F-16, a cooperative program on active futter suppression 

was established between Langley, the Air Force Wright Aeronautical Laboratories (AFWAL), and 

General Dynamics. Langley’s lead researchers for the program were Moses G. Farmer, Raymond 

G. Kvaternik, Jerome T. Foughner, Frank W. Cazier, and Michael H. Durham. Using a 0.25-scale 

futter model of the F-16, the team investigated a range of potential control concepts from analogtype systems to digital adaptive systems. 

Tests of a single wing-store confguration were led in 1979 by Foughner to investigate the suppression 

of futter for that specifc confguration. Study results demonstrated that an antisymmetric futter 

mode could be suppressed with an active control system, and detailed research data and analyses 

of the details of mechanizing such systems produced vital information for further developments. 

Test program highlights included a demonstrated ability to switch control laws on above the 

Jerome T. Foughner with F-16 model in Transonic 

Dynamics Tunnel during futter tests with external stores. 

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unaugmented futter condition without undesirable transients and demonstrated futter suppression 

to a dynamic pressure 100 percent above the unaugmented futter dynamic pressure. 

Further testing of the F-16 model by Cazier in 1981 introduced a second store confguration 

with successful demonstrations of futter suppression. Additional information on the dynamic 

response requirements for the control system was determined, and assessments of the efectiveness 

of individual control surfaces to suppress futter were made. 

Based on YF-17 test program successes and the F-16 demonstrations, the joint F-16 research 

team pursued the goal of developing and demonstrating a totally digital, adaptive suppression 

system. Te work tasks included developing a suppression system for three diferent external store 

confgurations, demonstrating a 30-percent improvement in futter speed for each confguration, 

and demonstrating the suppression of futter following the separation of a store from the wing. 

Conducted in 1986 by Cazier and Moses Farmer, these TDT tests contributed critical technology 

to the development of adaptive digital suppression controls. By demonstrating the feasibility of a 

digital adaptive system that required no prior knowledge of the wing-store confguration, coupled 

with successful simulated launching of missiles from a free-fying model at conditions below and 

above the unaugmented futter boundary, this highly successful cooperative research project has 

been recognized as a benchmark event for adaptive control technology development. 

In 1999, the Air Force designed and tested a prototype active futter suppression system (AFSS) 

designed to suppress the F-16’s tendency to oscillate when fying at high speeds while carrying 

certain combinations of fuel tanks and diferent types of weapons. Te motion is known as limit 

cycle oscillation, or LCO. Although the oscillations are not serious enough to damage an F-16, 

they can afect a pilot’s ability to precisely fulfll his mission, such as accurately launching a missile 

during air-to-air combat. Referred to as being “like driving a car with an out-of-balance tire,” the 

phenomenon is caused by the antisymmetric futter mode discussed earlier. Due to this mode’s 

excitation, the pilot experiences a side-to-side rolling motion in the cockpit. Te F-16 active futter 

suppression system was designed by Lockheed Martin Tactical Aircraft Systems and uses ailerons 

for futter suppression. Te fight tests included fights with the F-16 confgured in fve diferent 

store loadings, including heavy air-to-ground weapons under the wings, AIM-9 Sidewinder missiles 

attached on the wingtips, and wing-mounted fuel tanks. Te program successfully suppressed 

LCO at the desired speeds and altitudes for each combination of loadings. Te test team few 21 

fights with the system totaling more than 48 fying hours. 

Despite the improved characteristics experienced in the fight test evaluations, the AFSS has not 

been implemented in operational F-16s at this time. 

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F/A-18 Application 

A remarkable accomplishment in the suppression of wing-store limit cycle oscillations occurred 

in the early 1980s during the development and deployment of the F/A-18 aircraft by McDonnell 

Douglas. As an attack aircraft for the U.S. Navy, the F/A-18 is required to carry a wide variety of 

air-to-ground stores up to transonic speeds. During pre-production fight tests of certain external 

store confgurations, the aircraft exhibited an unacceptable LCO of about 5.6 Hz during futter 

testing. Te resulting lateral accelerations at the pilot’s station greatly exceeded allowable levels, 

with values of as much as 1.0 g peak to peak experienced in the cockpit. Te oscillations typically 

occurred only at altitudes less than 12,000 feet and at speeds greater than Mach 0.8. 

Te specifc store loading susceptible to LCO involved wing store combinations which included 

high pitch inertia stores on the outboard wing pylons along with wingtip-mounted AIM-9 missiles. 

Te fundamental structural contributor to the LCO mechanism was an outboard pylon/store 

antisymmetric pitch structural mode. Extensive fight testing demonstrated that the oscillations 

were not due to classical futter and were not reinforced by coupling with the fight control system. 

Testing further demonstrated that the wing oscillation amplitude was not sufcient to cause a 

structural integrity or fatigue problem. However, the accelerations at the pilots station were of 

sufcient magnitude to create a very uncomfortable ride and thereby degrade pilot performance. 

A fight test program was initiated to solve the LCO problem, with an initial focus on potential 

mechanical passive solutions. Te testing results indicated that a practical wing reconfguration 

could not be found to satisfactorily reduce the oscillations over the fight envelope. 

McDonnell Douglas engineers were aware of the research being conducted at Langley on wing/ 

store futter for the YF-17 and the F-16, and the promising results of that research gave the company 

additional confdence that an active system might provide a feasible solution to the F/A-18 problem. 

Te program was in a situation requiring a rapid and reliable solution which led to development 

of a solution from fight testing. One of the major issues encountered by the McDonnell Douglas 

team was the fact that the LCO phenomenon had not been predicted by futter analyses conducted 

at that time. Te LCO had been experienced almost 200 knots below the speed predicted by linear 

futter analysis. 

An Active Oscillation Suppression (AOS) system was subsequently developed under the 

programmatic constraint of only using the existing F/A-18 fight control system components 

and interfaces. After extensive analysis and fight test evaluations, an efective AOS system was 

developed and implemented using feedback from an existing lateral accelerometer to actuate the 

aircraft’s ailerons via the fight control computer. During other fight testing, it was found that 

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McDonnell Douglas successfully developed and applied an active control system to suppress wing/store limit cycle 

oscillations in production F/A-18 aircraft 

certain outboard pylon store confgurations would not require engagement of the AOS. Tus, 

logic to interrogate the type of store confgurations carried was implemented within the AOS 

system. Since the LCO was not regarded as a classical futter problem and therefore not a safety 

of fight consideration, the use of a single string AOS concept did not violate any redundancy 

requirements. However, if more serious futter is encountered for future aircraft requiring active 

futter suppression, redundancy will have to be considered from a fight safety perspective. 

Following the highly successful development of the AOS system by McDonnell Douglas, the 

system was applied on all production F/A-18A/B/C/D aircraft and has been extremely efective for 

over 20 years. Although NASA was not an active participant in the development of the solution 

to the F/A-18 problem, the precursor research that had been conducted by Langley played an 

important role in establishing confdence and risk reduction in this critical activity. 

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Decoupler Pylon 

In concluding the discussion of wing-store futter suppression, it is appropriate to mention an 

innovative “quasi-passive” concept conceived by Langley’s Wilmer H. (Bill) Reed, III, in the early 

1980s. As an alternative to conventional passive methods of incorporating additional structure to 

increase stifness or to use advanced active control methods, Reed devised a spring-mount system 

for external stores called a decoupler pylon, which isolates or decouples the external store’s pitching 

vibratory motions from those of the wing, thereby increasing the futter speed. Te concept was 

substantiated by analysis, demonstrated in TDT tests, and validated at full-scale conditions through 

fight test using an F-16 airplane. Langley participants in studies of this revolutionary concept, in 

addition to Reed, were Frank W. Cazier, Jr., Moses G. Farmer, and Harry L. Runyon, Jr. 

Reed’s decoupler pylon concept was relatively simple yet very efective. It consisted of soft-spring 

and damper components that, in combination, isolated the wing from the pitch inertia efects of 

the external store. A low frequency, automatically controlled alignment system was provided to 

keep the softly supported store properly positioned relative to the wing during maneuvers. Te 

decoupler pylon could be made robust in that a variety of diferent stores could be mounted on the 

same decoupler pylon without changing the overall wing futter characteristics. 

Following some carefully crafted analytical studies, and after highly successful wind-tunnel studies 

in the TDT using YF-17 and F-16 futter models demonstrated increases in futter speeds of over 

100 percent could be obtained by using the decoupler pylon versus the same store mounted on a 

conventional pylon, a fight demonstration program was initiated. Te plan was to design, build, 

and fight test a decoupler pylon on an F-16 airplane. A pair of decoupler pylons was designed, 

fabricated, and ground tested by General Dynamics (now Lockheed Martin) under contract to 

NASA. Te fight tests were conducted on an F-16 from the Joint Task Force at Edwards Air Force 

Base, California. Langley’s Frank W. Cazier, Jr., served as Project Manager for the fight test in a 

joint activity with NASA Dryden Flight Research Center, the Air Force, and General Dynamics. 

Te chosen test confguration was an asymmetric loading of AIM-9J wingtip missiles, a GBU-8 

bomb near midspan, and a half-full 370-gallon fuel tank inboard. Tat particular confguration 

exhibited the well-defned limited-amplitude antisymmetric futter when the bomb is carried on 

a standard F-16 pylon. Analyses and wind-tunnel tests indicated that mounting the bombs on 

decoupler pylons in place of standard pylons would appreciably increase the airplane’s futter speed. 

Te fight test objectives were to demonstrate an improvement futter speed of at least 30 percent 

over the conventional pylon futter boundary, assess the requirements for the alignment system, 

and demonstrate that store separation from the decoupler pylon was satisfactory. 

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Flight tests for the F-16 in 1985 with a standard pylon-store confguration were frst conducted 

at an altitude of 10,000 ft and for Mach numbers above 0.7. Tis confguration experienced the 

antisymmetric LCO discussed previously. Pilots described the oscillation as a “continual pounding 

oscillation that was of sufcient amplitude to cause visual blurring of the cockpit displays.” With 

the decoupler pylon, the LCO that had been experienced with the standard pylons was suppressed 

throughout the fight envelope tested. Te investigation expanded in scope to develop methods to 

reduce friction in the pylon mechanisms, as well as assessments of the efectiveness of the alignment 

system. During one fight test, a GBU-8 was ejected, demonstrating that weapons separation from 

the decoupler pylon was satisfactory. Flight tests, including maneuvers, demonstrated an increase 

in futter speed of 37 percent over the standard F-16 pylon confguration. 

As was the case for the F-16 AFSS, technical success in the decoupler project did not lead to 

applications to the F-16 feet. 

Load Alleviation 

Te reduction of loads imposed on aircraft by maneuvers, gusts, and turbulence has been explored 

extensively by Langley researchers during in-house studies and cooperative programs with their 

partners from industry and DoD. Te range of airplane confgurations studied has included 

general aviation airplanes, commercial transports, military transports, and bombers. Although 

some activities were based on passive control that did not include elements of active control systems, 

they are included herein for background and completeness. 

C-5A Active Lift Distribution Control System 

Lockheed-Georgia was awarded an October 1965 Air Force contract for a C-5A heavy transport 

with a specifed wing fatigue life of 30,000 fying hours. Te frst fight of the new transport 

was in June 1968 and, unfortunately, static fatigue testing of a wing test specimen revealed wing 

structural cracks in July 1969. Although a structural modifcation program was immediately 

begun to reinforce the critical wing stations, structural modifcations turned out not to be an 

acceptable long-term solution to the problem. After the C-5A had been in service for several years, 

a wing tear-down inspection on one aircraft revealed cracks in the structure that projected to a 

fatigue life of less than 8,000 fying hours, approximately one quarter of the desired life. Lockheed 

proceeded to explore solutions, including an active aileron system to alleviate gust loads on the 

wing, local structural modifcations to improve fatigue life, and redistribution of fuel within the 

wing to reduce bending moments. Active ailerons were retroftted to C-5As during 1975 to 1977 as 

part of an active lift distribution control system (ALDCS) that increased fatigue life by symmetric 

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C-5 model mounted in the Transonic Dynamics Tunnel. 

defections of the ailerons in response to gusts and maneuvers. Te concept also used an automatic 

elevator defection to null out pitching moments caused by the aileron defections. Additional 

redesign of the center wing and wing box sections was also incorporated in the modifcation 

program, and by 1987 all surviving C-5As had been modifed. Also, in 1982 the decision was made 

to have Lockheed build 50 C-5Bs, which incorporated the wing improvements of the C-5A. 

Wind-tunnel tests conduced in the Langley TDT during 1973 were a key component of the 

successful development of the ALDCS. A full-span cable-mounted 1/22-scale C-5A model was 

tested to experimentally verify the efectiveness of the ALDCS system in reducing loads. Langley’s 

Charles L. Ruhlin and Maynard C. Sandford led the NASA-Lockheed team that conducted this 

frst-ever scaled model study of an ALDCS. 

Te C-5 test was very successful. Te results showed that the ALDCS was very efective in reducing 

both wing dynamic bending and torsion loads. Bending moments at the frequency of the wing 

frst bending mode were reduced by more than 50 percent across the wing span. Although the 

reduction for torsion loads was less, it was still substantial. Later correlation of results from airplane 

fight tests and the aeroelastic wind-tunnel model tests were in very good agreement for the critical 

low frequency bending mode. Once again, this study validated the use of active control technology 

to reduce aircraft aeroelastic response and further demonstrated the valid application of aeroelastic 

wind-tunnel models for developing active control technology. 

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Passive Gust Load Alleviation 

Te ride quality for passengers in light general aviation airplanes in turbulent weather is 

characteristically rough and uncomfortable. Particularly ofensive are the large up-and-down 

heave motions encountered because of relatively light wing loadings of such aircraft. Researchers 

at Langley have investigated the human response to typical accelerations encountered in fight, and 

have identifed the critical frequencies that lead to highly undesirable efects on humans, including 

airsickness. An extensive investigation into the subject of ride quality was led by Langley’s D. 

William (Bill) Conner during the 1970s. 

Although these highly undesirable passenger accelerations could theoretically be alleviated by an 

automatic control system using appropriate sensors, computers, and rapid-actuation controls, the 

complexity, costs, and maintenance of such systems are beyond the capabilities of typical airplane 

owners. Despite the long-term interest of designers in reducing the efects of turbulence on ride 

quality, and the continuing dissatisfaction of public passengers with undesirable accelerations due 

to turbulence, no current general aviation aircraft are equipped with gust-alleviation systems. As 

part of a long-term research in aircraft response to gusts, Langley Research Center has investigated 

several concepts for gust alleviation for this class of aircraft. 

In the late 1940s Langley’s W. Hewitt Phillips was exposed to an earlier French gust-alleviation 

concept by René Hirsch wherein the horizontal tail surfaces were connected by pushrods to faps 

on the wing. On encountering an upward gust, the tail surfaces would defect up, moving the wing 

faps up and thereby ofsetting the efects of the gust. Te system had been analyzed and designed 

to minimize adverse interactions on other airplane characteristics, such as pitching moments. 

(Phillips later traveled to France in 1975, met Hirsch, and inspected some of the aircraft that he 

had designed.) Intrigued by the possibility of achieving gust alleviation with automatic controls 

rather than the complex aeromechanical interconnects of Hirsch’s design, Phillips began studies of 

airplane response characteristics to sinusoidal gusts and the character of control inputs required to 

alleviate accelerations. After studying several systems, he arrived at the idea of using a gust-sensing 

vane mounted on a boom ahead of the nose to operate faps on the wing through a hydraulic 

servomechanism. 

Following analytical studies, a fight demonstration project was conceived to demonstrate gust 

alleviation in fight. A Navy C-45 twin-engine airplane was modifed to include a nose boom 

to hold an angle-of-attack vane; the wing faps, which normally defected only downward, were 

modifed for defections in both up and down directions; the elevator was split into three sections 

with two sections being linked to the faps for gust alleviation; and small segments of the wing 

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faps near the fuselage were driven separately from the rest of the fap system so that they could be 

used in either the same or opposite directions as the rest of the faps. Following these NACA tests 

at Langley, jet transports were introduced into commercial service and the higher wing loadings, 

higher cruise altitudes, and the use of weather radar to avoid storms resulted in less likelihood 

that passengers might become airsick. Also, the problem of active gust alleviation was made more 

difcult because the structural fexibility of jet transports placed structural frequencies closer to 

the range of interest for gust alleviation. Tus, the interest and momentum for gust-alleviation 

systems waned. 

Following a visit to France and meeting with Hirsch in 1975, Phillips revisited the aeromechanical 

approach to gust alleviation and initiated a Langley study of the concept. Eric C. Stewart, L. Tracey 

Redd, and Robert. V. Doggett, Jr., led analytical and experimental studies of a 1/6-scale model 

of a typical general aviation airplane equipped with an aeromechanical gust alleviation system. 

Nose boom with angle of attack vane on C-45 transport used for gust alleviation research. 

Te project was designed as a cooperative venture between NASA, Cessna, and the Massachusetts 

Institute of Technology (MIT). Te gust alleviation system consisted of two auxiliary aerodynamic 

surfaces that defected the wing faps through mechanical linkages to maintain nearly constant 

airplane lift when a gust was encountered. Te dynamic model represented a four-place, highwing, single-engine light airplane, and was rod mounted in the Langley TDT for tests. Te efects 

208 Innovation in Flight 
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of faps with diferent spans, two sizes of auxiliary aerodynamic surfaces, single and doublehinged faps, and a fap-elevator interconnect were studied. Investigation results showed that the 

gust-alleviation system reduced the model’s root-mean-square normal acceleration response by 

30 percent in comparison with the response in the faps-locked condition. Despite these 

promising results, the aeromechanical concept was not pursued and has not been applied to 

production aircraft. 

About 10 years later, Langley briefy pursued a concept for an active, computer-based gustalleviation system for general aviation aircraft. Teamed with Cessna and the University of 

Kansas, Langley researchers conducted analytical studies of the application of computer-driven 

controls with a view toward fight demonstrations using a Cessna C-402 twin-engine research 

airplane. Te analysis included the use of advanced modern control theory to develop the control 

architecture. Unfortunately, the response characteristics required of the control actuators could 

not be accommodated within the budget and time allotted for the project, and the activity 

was terminated. 

Combined Aeroelastic Control Concepts 

Although some studies examined the efectiveness of a single active control concept, others 

emphasized more than one: for example, the simultaneous application of active futter suppression 

and active load control. Some of these latter studies are described in this section. 

B-52 Control Confgured Vehicles Program 

Te B-52 Control Confgured Vehicle (CCV) Program was the frst in a number of studies addressing 

multiple applications of active controls. It was a natural follow-up to work of the 1960s in applying 

fight controls systems to attenuate the structural response (especially cockpit accelerations) of large 

military airplanes such as the B-52E and the XB-70. 

During the early 1970s, AFFDL sponsored the B-52 CCV Program at Te Boeing Company to 

demonstrate the benefts of applying advanced fight control technology to a large fexible airplane. 

Te efort was initiated in July 1971 and was completed in 1974. A highly modifed Boeing NB52E bomber was used to investigate four active control concepts: ride control, futter mode control, 

maneuver load control, and augmented stability. Te existing elevators and rudder of the B-52 

were not sufcient to implement the control systems, so it was necessary to add additional control 

surfaces consisting of three-segment faperons, outboard ailerons, and horizontal and vertical 

canards. On August 2, 1973, the B-52 CCV test aircraft made aviation history by fying 10 kts faster 

Innovation in Flight 209 
 

 

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than its futter speed. Although the fight tests were halted at this point, there was no indication 

of a decrease in damping in the structural vibration mode important to futter, so the actual 

futter speed was considerably higher. Tis event was the frst time that an aircraft had been fight 

tested above its futter speed relying solely on an active futter control system to augment the 

structural damping. 

At Langley, an investigation sponsored by AFFDL with Boeing and NASA participation was 

conducted for correlation with fight results. Te objective was to demonstrate that wind-tunnel 

models and testing techniques could be used to design and assess active control concepts. An 

existing 1/30-scale, full-span, free-fying B-52 aeroelastic wind-tunnel model was modifed and 

tested in the TDT. Although capability to study all four active control concepts was incorporated 

into the model, only active vertical ride control (VRC) and active futter suppression (AFS) were 

actually tested during three separate wind-tunnel tests in 1973 and 1974. Te Langley Project 

Managers for the wind-tunnel studies were Jean Gilman, Jr., and L. Tracy Redd. 

Te airplane VRC system was designed to reduce the gust-induced vertical acceleration at the 

pilot’s station by at least 30 percent. Tis system processed vertical acceleration signals sensed 

at the pilot’s station through a computer implemented control law to drive horizontal canards. 

Te performance of the model’s VRC closely matched the performance of the full-scale airplane 

system, resulting in a dramatic reduction in vertical accelerations at the cockpit location 

Te AFS consisted of feedback loops using signals from accelerometers mounted on the model’s 

external fuel tanks (fed back to the aileron control surfaces) and from accelerometer signals located 

near the midwing (fed back to the fap segments). Wind-tunnel tests results demonstrated that, 

with the AFS on, the damping in the futter mode showed a large improvement over that displayed 

with the AFS of, verifying the full-scale fight results and indicating the potential for a signifcant 

increase in futter speed. 

Follow-up AFS tests with yet another modifcation to the B-52 model were conducted by Robert V. 

Doggett, Jr., Rodney H. Ricketts, and Maynard Sandford in 1978. For this study, the model was 

converted from a free-fying model to a sting-mounted model. In this case, the digital-computerimplemented control laws had to simultaneously deal with two distinct futter modes, one 

involving antisymmetric wing motion and the other involving symmetric wing motion. Because 

the control laws were implemented on three separate computers, it was possible to evaluate the 

efects of system failures on the efectiveness of the AFS. Tis study provided the frst successful 

demonstration of multimode, digital active futter suppression, including considerations of 

redundancy management. 

210 Innovation in Flight 
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From a research viewpoint, the most signifcant result of B-52 CCV experiments in the TDT was 

validation that dynamically scaled, actively controlled wind-tunnel models could be used to study 

and demonstrate advanced active control concepts. Based on the proven success of this pioneering 

efort, wind-tunnel models in the TDT are now used routinely to increase the confdence level in 

active control concepts by providing data to verify analytical models and methods used in design 

and to eliminate the risks and lower the costs associated with fight testing such concepts. 

Te Aircraft Energy Efciency Active Controls Technology Program 

In 1976, NASA initiated its ACEE Program in response to the dramatic increase in fuel prices that 

began in the early 1970s. Te program included several elements of technology in aerodynamics and 

active controls with an emphasis on concepts that traded cruise speed for increased fuel efciency. 

A major part of ACEE activities was the EET Program. Langley’s leaders in the active controls 

element of the EET Program were Ray V. Hood (Program Manager) and David B. Middleton 

(Deputy Program Manager). A detailed program summary and bibliography of the EET activities 

has been prepared by Middleton, Bartlett, and Hood (see bibliography). One element of the EET 

Program included in-house research activities and cost-shared contracts with Boeing, Douglas, 

and Lockheed-California for the analysis, preliminary design, testing, and in-depth assessments of 

selected advanced concepts for ACT for improved mission efciencies. Because higher aspect-ratio 

wings quickly became a focal point for aerodynamic efciency, control of aeroelastic responses 

became a vital segment of the program. 

Active wing futter suppression concepts were pursued that increased the damping of wing structural 

modes important to futter to the extent that the futter placard speed was increased beyond the 

airplane’s expected maximum operating speed without adding any structural weight. In addition, 

maneuver load control concepts that reduced wing-bending moments during maneuvering fight 

were conceived, as well as active gust load alleviation systems that reduced structural loads during 

encounters with vertical gusts. Collectively, these two load alleviation systems comprised an active 

control function called wing-load alleviation. 

Douglas pursued the design and assessment of active systems for futter suppression and load 

alleviation on a derivative of the DC-10 confguration that had an increased wing span. Windtunnel testing to determine dynamic wing loads was conducted in industry tunnels, and control 

laws derived by Douglas using conventional methods increased futter speed by up to 19 percent 

and signifcantly decreased wing-bending accelerations. Within this coordinated efort, Langley 

supplied alternate control laws based on advanced design methods. Both NASA control system 

designs increased futter speeds by more than 25 percent. 

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Te Lockheed L-1011-500 was the frst commercial transport to 

use active load control. 

Lockheed studies involved extending the wing span of its existing Lockheed L-1011 transport 

confguration and providing a load alleviation system using symmetric operation of outboard ailerons 

at high speeds. Outboard ailerons on most conventional transports are designed to be inoperative 

at high speeds because of adverse aeroelastic issues, and inboard ailerons are used for roll control. 

Te load alleviation system for the L-1011 redistributed the wing lift and thus eliminated the need 

for signifcant structural redesign and increase in structural weight to support the extended wing 

span. Tis confguration was ultimately implemented by Lockheed with company funds and fight 

tested on Lockheed’s L-1011 research airplane, demonstrating a 3-percent fuel savings. Based on 

these very favorable results, Lockheed immediately pursued FAA certifcation of the active control 

system and later incorporated the system in its derivative long-range Advanced TriStar L-1011-500 

transport in 1980, representing the frst signifcant application of active controls to a modern widebody transport. 

Te ACEE Program’s EET element greatly accelerated the state of the art in active control of 

aeroelastic response, and the resulting application by Lockheed to the L-1011 was a major event in 

the acceptability and certifcation of such systems. 

Drones for Aerodynamic and Structural Testing Program 

In keeping with its mission for conducting high-risk research, Langley conceived and initiated a 

fight test project known as Drones for Aerodynamic and Structural Testing (DAST) in the early 

1970s to validate analysis and synthesis methods for active control of aeroelastic response and 

analysis techniques for aerodynamic loads prediction. Flight tests provided the opportunity to 

simulate characteristics that could not be accurately simulated or properly accounted for in wind212 Innovation in Flight 
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tunnel tests, such as maneuvering fight. Because of the inherent risks in fight testing advanced 

active control concepts, an unmanned, remotely controlled Teledyne-Ryan BQM-34 Firebee II 

was chosen as the test vehicle, with the fight test to be conducted at NASA’s Dryden Flight 

Research Center. Langley’s Harold N. Murrow was the Project Manager and headed a virtual 

“who’s who” team of Langley aeroelasticians, aerodynamic and structural analysts, and control 

theory specialists. Some key Langley researchers were Irving Abel, William M. Adams, Jr., Clinton 

V. Eckstrom, Jerry R. Newsom, Boyd Perry, III, Maynard C. Sandford, and Vivak Mukhopadhyay. 

An equally competent team was assembled at Dryden to conduct the fight tests. 

NASA F-8 research airplane with supercritical wing used as basis for 

design of ARW-1 wing. 

Te plan was to ft the Firebee with two aeroelastic research wings (ARW). Both wings were to be 

representative of advanced subsonic transonic transport confgurations. ARW-1 was to have the 

same planform as the research wing that had been used in Dryden fight demonstrations of the 

supercritical airfoil section on the NASA F-8 research airplane. Te ARW-1 test evaluated two 

active futter suppression systems that had been carefully selected from a number of proposals. Te 

objective was to demonstrate in transonic fight at least a 20-percent increase in futter velocity. 

Wind-tunnel tests in the TDT were conducted using a simplifed model of the ARW-1 to add 

confdence that the proper choices had been made. 

Te ARW-2 wing was an even more ambitious activity, including three active control systems: 

futter suppression, gust load alleviation, and maneuver load alleviation. Te ARW-2 had a higher 

aspect ratio than ARW-1. Te wing confguration was chosen to represent a design derived during 

a NASA-contracted Boeing study of EET confgurations. Fabrication of the ARW-2 began while 

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the ARW-1 portion of the program was still in progress. Part of the ARW-2 plan was to test one of 

the fight test wing panels in the TDT as opposed to building a separate simplifed model, as was 

done for ARW-1. TDT testing of the ARW-2 wing by Maynard Sandford began in 1978. 

Te fight-test approach involved launching the test drone from a wing-mounted pylon on NASA’s 

B-52B launch aircraft, conducting the active control experiments, then recovering the test vehicle 

by deploying an onboard parachute that was “air-snatched” by an Air Force helicopter/aircrew 

during descent. During the free-fight portion of the experiment, a NASA pilot controlled the 

drone from a remote ground-based cockpit while researchers monitored fight data transmitted via 

telemetry. In case the telemetry link between the drone and the ground was lost, the Firebee could 

also be fown to the recovery site using a backup control system in a NASA F-104 chase airplane. 

Drone with standard Firebee wing mated to 

B-52 in 1977 captive fight at 

NASA Dryden. 

Drone during fight with ARW-1 research 

wing on June 12, 1980, before catastrophic 

futter occurred. 

214 Innovation in Flight 
 

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Research fights for the DAST program at Dryden were conducted from 1977 to 1983. Initial fght 

tests were conducted with the Firebee ftted with an instrumented standard wing (also called the 

“Blue Streak” wing) to (1) develop test procedures and experience to be used during assessments of 

the futter-suppression concepts for the ARW-1, and (2) to obtain wing data on surface pressures 

and bending moments using strain gauge instrumentation. Te wing had been designed for a 

predicted futter speed of Mach 0.95 at an altitude of 25,000 ft. 

Unfortunately, the DAST project was fraught with operational problems, so only a few fights 

were completed successfully. Research studies of ARW-1 were halted unceremoniously when the 

test vehicle crashed on June 12, 1980. A programming error in implementing the active futter 

suppression control law went undetected, despite careful review by all participants. Tis error 

resulted in the system gain being only one-fourth the desired value, and the wing futtered 

unexpectedly at fight conditions where it should have been well safe from futter. Tis catastrophic 

futter resulted in the breakup of the wings and subsequent crash of the test vehicle. 

Te ARW-1 wing was rebuilt after the crash and again prepared for testing with the control law 

error corrected. On June 1, 1983, the ARW-1’s misfortune continued when, following launch from 

a Navy DC-130 airplane routinely used to launch military drones such as the Firebee, the recovery 

parachute system malfunctioned and the parachute inadvertently disconnected from the drone, 

resulting in a second crash. 

Following this second crash, the DAST project was terminated for several reasons. Te program’s 

initially planned 5-year lifetime had elapsed, and a combination of reduced funding and resource 

demands for other emerging high-priority unmanned airplane projects at Dryden made additional 

fight tests unlikely. However, the planned TDT testing of the ARW-2 wing was completed prior 

to the program’s fnal termination. 

Some view the DAST project as a technical disappointment because the program’s original 

objectives were not attained. However, all the program’s inherent research and active control 

law development considerably advanced the overall state of the art in applying active control 

techniques to favorably modify aeroelastic response. Perhaps the program’s most important legacy 

was the dramatic experience with the challenges and difculty of achieving some of these advanced 

concepts in practice. 

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Active Flexible Wing Program 

In the early 1980s, engineers at Rockwell International Corporation conceived and studied 

analytically an active control concept that became known as the active fexible wing (AFW). 

Rockwell’s early work was so promising that a cooperative research program involving Rockwell, 

the U.S. AFWAL, and NASA Langley was initiated in 1985 to further develop the concept and 

demonstrate it in tests in the TDT. 

In the AFW concept, an active roll control system was used to optimize the airplane’s rolling 

response while minimizing maneuver loads. Tis was achieved by taking advantage of inherent 

fexibility characteristics of the wings in a carefully controlled manner in conjunction with actuating 

leading- and trailing-edge control surfaces. Te system monitored both fight conditions and wing 

structural deformations. Using this information, the system selects the best control surfaces to 

produce the desired rolling motion and commands those surfaces to defect accordingly. An active 

roll control system ofers the potential for signifcant savings in structural weight. For example, 

because the system works efectively at angles of attack above the control-surface reversal condition, 

it would eliminate the need for the “rolling horizontal tail” and render unnecessary the structural 

weight required by the rolling tail. If the AFW incorporates other active control applications, 

such as active futter suppression, gust load alleviation, and maneuver load control, additional 

weight savings are possible. Rockwell predicted that by taking full advantage of the AFW concept, 

a weight savings of at least 15 percent of takeof gross weight was possible for advanced 

fghter confgurations. 

Testing of the AFW concept in the TDT was conducted between 1986 and 1991. Langley’s 

leading researchers for the AFW investigations included Boyd Perry, III, Carol D. Wieseman, 

Jennifer Heeg, Jessica A. Woods-Vedeler, Anthony S. Pototzky, Sherwood T. Hoadley, Vivak 

Mukhopadhyay, Maynard C. Sandford, Stanley R. Cole, William M. Adams, Jr., Carey S. Buttrill, 

Jacob A. Houck, and Martin R. Wazak. 

Te AFW TDT study used an aeroelastically scaled, 1/6-scale, full-span wind-tunnel model 

of an advanced fghter concept that was fabricated by Rockwell and tested during four diferent 

tunnel entries. Te model featured eight separate active control surfaces with two leading and 

two trailing edges on each side of the wing. As per the name, the wing of the AFW model was 

designed to be extremely fexible and lightweight. Te model test set up included a novel singledegree-of-freedom internal bearing arrangement, which permitted the model to roll freely about 

the wind-tunnel sting mount. Extensive instrumentation and sensors were also implemented in the 

model, including accelerometers, strain gauges, and a roll-rate gyro. Because the futter speed of 

216 Innovation in Flight 
CONTROL OF AEROELASTIC RESPONSE: TAMING THE THREATS 

the basic confguration was too high, it was reduced by the addition of a specially designed wing 

tip mounted store. A remotely controlled weight within the store could be rapidly moved to raise 

the futter speed should violent futter be encountered unexpectedly. 

Te investigation included two distinct research parts. In the frst part, the Air Force, Langley, and 

Rockwell coordinated eforts to demonstrate the efectiveness of the basic AFW concept during 

TDT tests in 1986 and 1987. In the frst of these tests, a data base of static forces and moments 

produced by control surface defections was determined. Tese data were required to provide 

accurate values of the control surface efectiveness needed to design the active roll control system. 

After several active roll control laws were synthesized by using this data base, the diferent control 

was implemented on the wind-tunnel model system and each successfully evaluated during the 

second wind-tunnel test. All the digital-computer implemented control laws performed well, with 

the experimental results being in good agreement with theoretical predictions. Te test results 

clearly showed that the AFW concept worked as advertised and, therefore, ofers a viable means of 

improving the maneuver and roll control characteristics of advanced fghter type airplanes. 

Te second part of the AFW study was considerably more complex than the frst. Te objective 

was to demonstrate multi-input/multi-output (MIMO) single function and multifunction digital 

control of aeroelastic response. Tree active control capabilities were incorporated into the windtunnel model system: active futter suppression, the roll rate tracking system (RRTS), and rolling 

maneuver load alleviation (RMLA). Te RRTS was designed to limit loads only when loads reach 

a predetermined level. Te RMLA was designed to reduce loads during rolling maneuvers up to 90 

degrees in amplitude. Te control laws were implemented on a digital computer. Single function 

MIMO studies were conducted for each control system. Multifunction studies were conducted for 

active futter suppression in combination with each of the two roll control systems 

Key accomplishments of this sophisticated investigation included successful demonstrations of 

single- and multiple-mode futter suppression, load alleviation and load control during rapid roll 

maneuvers, and MIMO active-control demonstrations above the open-loop futter boundary. 

Rolling maneuvers representative of goals defned by military specifcations were performed, and 

wing loads were controlled at dynamic pressures 24 percent above the open-loop futter condition. 

In addition to signifcantly advancing active controls technology, this study also provided 

signifcant advances in the wind-tunnel test methodology needed to evaluate active control of 

aeroelastic response. 

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Te Benchmark Active Controls Technology Project 

Te analysis and accurate prediction of aeroelastic phenomena is one of the most difcult challenges 

facing aerospace engineers. Not only are the phenomena afected by complex interactions 

of aerodynamic and structural forces, but they often are most troublesome in nonlinear fight 

regimes, such as transonic speeds. Te addition of active controls to the technology poses even new 

challenges to aeroelasticians. In the late 1980s, Langley initiated the Benchmark Models Program 

(BMP), with goals of providing high quality experimental data that could be used to the evaluate 

the accuracy of advanced CFD codes applicable to aeroelastic analysis and to study the efects of 

new aerodynamic concepts on aeroelastic phenomena. Te basic idea was to conduct relatively 

simple experimental studies where it would be possible to isolate the efects of key parameters, such 

as airfoil shape. Although active control technology was not included in the initial program plan, 

such studies were added after the program was initiated. 

Te BMP Program was a collaborative efort among several working groups of the Structural 

Dynamics Division and was supported by the entire Langley infrastructure. Te Confguration 

Aeroelasticity Branch, the Unsteady Aerodynamics Branch, and the Aeroservoelasticity Branch all 

participated in the research activities, which were based on about two tests in the TDT per year 

over the program’s 5-year duration. TDT researchers Robert M. Bennett, Clinton V. Eckstrom, 

Jose A. Rivera, Jr., Bryan E. Dansberry, Moses G. Farmer, Michael H. Durham, David A. Seidel, 

and Walter A. Silva collaborated in early benchmark studies. Researchers David M. Schuster, 

Robert C. Scott, and Sherwood T. Hoadley joined the team as the program evolved. 

Te program used a basic benchmark active controls technology (BACT) model, which was a rigid 

semispan confguration that had an NACA 0012 airfoil section. Te unswept rectangular-planform 

model could be mounted on either rigid or fexible supports. Te relatively simple, fexible support 

system provided for pitch and plunge motion of the model, the two most important motions to 

aeroelastic response. Tis system greatly simplifed the structural aspects of the experiment and 

allowed the focus to be on aerodynamics and active controls. Te model was well instrumented, 

with a number of pressure transducers to determine aerodynamic pressures and accelerometers to 

measure model motion. Te model had a remotely controlled trailing-edge aerodynamic control 

surface that could be positioned either statically or dynamically. Remotely controlled upper and 

lower surface aerodynamic spoilers were also provided. Te trailing-edge control and the spoilers 

were driven by miniature hydraulic actuators similar to those developed during the delta wing 

futter suppression study. 

218 Innovation in Flight 
 

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Te BACT model ofered the opportunity to conduct a number of pioneering active control studies. 

Many of these are very technical and can be fully appreciated only by those well versed in controls 

theory, whereas others are relatively easy to understand. A couple of the latter studies will be 

cited here. Although it had been shown previously by another investigator that statically defected 

spoilers were efective in increasing futter speeds, BACT model tests represented the frst time 

that actively controlled spoilers were efectively used as futter suppressors. Te second example 

was application of artifcial intelligence (neural network) concepts to active futter suppression. 

Artifcial intelligence systems learn based on experiences and, depending on the application, 

may actually improve themselves as they are used or gain experience. Tis efort was part of the 

Adaptive Neural Control of Aeroelastic Response Program, which was a joint efort between NASA 

Langley and McDonnell Douglas Corporation (now part of Te Boeing Company). A number of 

control systems, both adaptive and nonadaptive, were developed using neural network concepts 

implemented on the BACT model and successfully demonstrated in TDT tests. 

Te BACT model provided an opportunity not only to learn more about the characteristics of 

diferent aeroelastic phenomena, but also to evaluate very advanced active control techniques during 

an experiment that is easily managed as compared with many active controls studies conducted 

heretofore. Although the model system might be relatively simple, the phenomena being studied 

were not. 

Piezoelectric Aeroelastic Response Tailoring Investigation 

Before discussing the details of the Piezoelectric Aeroelastic Response Tailoring Investigation 

(PARTI) some introductory comments are in order. Previous active control studies to favorably 

change aeroelastic response of airplanes had focused on the use of traditional aerodynamic control 

surfaces to efect the changes in excitation forces needed to accomplish the desired performance 

improvements. As advances were made in structural and other technologies, it became apparent 

that the use of “structural actuators” might be viable alternatives to “aerodynamic control surface” 

actuators. Piezoelectric materials appeared to ofer much promise. When electric voltages are 

applied to these materials, internal strains develop that cause the material to change shape. By 

controlling the applied voltages to piezoelectric actuators either embedded in or mounted on a 

structure, it is possible to deform the structure in a desirable manner. 

Inspired by graduate student Robert C. Scott’s (later a TDT staf member) thesis in 1990, 

Jennifer Heeg designed and implemented an exploratory wind-tunnel experiment to assess the 

use of piezoelectric actuators in active futter suppression. Following the detailed development of a 

candidate control law, a wind-tunnel experiment of a simple, free to pitch and plunge, aeroelastic 

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wing model was conducted in the Flutter Research and Experiment Device (FRED), which was 

a small open-circuit wind tunnel with a 6- by 6-in. test section. Te experiments, which included 

open-loop and closed-loop futter testing, demonstrated that the use of piezoelectric control could 

increase futter speed of the test wing by about 20 percent. Almost simultaneously, Heeg expanded 

her study to include active control of bufeting response. A modifed version of the model was used 

for additional tests in FRED. Tis study resulted in the frst successful application in the United 

States of active controls to attenuating bufeting response. 

Te favorable results of Heeg’s early work and of studies performed elsewhere led Langley to establish 

a cooperative research program with MIT. Te program’s purposes were to further evaluate the 

ability of distributed strain actuators to control aeroelastic response and to demonstrate selected 

concepts on a research model wing to be tested in the Langley TDT. Te principle used for control 

in the investigation involved the use of piezoelectric actuators. Te piezoelectric actuator concept 

consists of a series of electrical strain-gauge patches (potentially hundreds per wing) wired for a 

low-current, high-voltage electrical charge. Wing response measurements, either static or dynamic, 

are fed back through control laws that output voltages to these actuators, either individually or 

in selected combinations. Tese voltages produce internal actuator strains that cause the wing to 

deform either statically or dynamically in a desired manner. 

Te PARTI project used an aeroelastic semispan model with 72 distributed piezoelectric actuator 

patches on the upper and lower surfaces of the wing. (An actual airplane application may require 

hundreds of actuator patches.) Various groups of actuator patches were oriented to facilitate bending 

and torsional responses of the model. In addition to the piezoelectric actuators, the model had a 

trailing-edge aerodynamic control surface driven by an electric motor located in the wing root. 

Extensive research activities were allocated to the development of instrumentation, control law 

development, and experimental demonstrations of futter suppression. 

During the frst TDT entry in early 1994, the open-loop characteristics of the model were 

determined, including supercritical (below futter) response, basic futter characteristics of 

the model, and time-dependent response functions for each important piezoelectric sensor 

group. Tese data provided the foundation for the Langley-MIT research team to construct 

mathematical models of candidate control laws and validate analysis techniques prior to additional 

wind-tunnel testing. 

Objectives of the second TDT entry in late 1994 included an assessment and demonstration of the 

capability of piezoelectric actuators to suppress futter and to reduce aeroelastic response caused by 

tunnel turbulence. Several control laws, based on diferent design techniques, were implemented 

220 Innovation in Flight 
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to assess input-output control efectiveness for various sensor and actuator groups. For the most 

successful control law, an increase in futter dynamic pressure of 12 percent was demonstrated, and 

the peak value of strain measured by the instrumentation was signifcantly reduced for dynamic 

pressures below futter. 

Te PARTI project successfully completed its primary objective of demonstrating futter 

suppression and aeroelastic response control by using distributed piezoelectric actuators on a largescale aeroelastic wind-tunnel model. Key Langley researchers for PARTI included Anna-Maria R. 

McGowan, Jennifer Heeg, Donald F. Keller, and Renee C. Lake. 

Control of Aeroelastic Response of Vertical Tails 

During the 1970s, the operational doctrine of U.S. military air forces began to focus on 

highly maneuverable fghter tactics. Extensive advancements in aerodynamics, propulsion, and 

structures—coupled with efective digital fight controls that provided “carefree” maneuvering— 

resulted in signifcant operations at high angles of attack. Many recently developed advanced 

U.S. fghter confgurations have used vortex-control techniques for enhanced lift during strenuous 

maneuvers, as well as twin-tail confgurations to provide satisfactory stability and control during 

these conditions. A number of these confgurations, including the F-14, F-15, F-18, and F-22, have 

experienced problematic bufeting loads and oscillatory stresses to the vertical tails at high angles 

of attack (above about 25 degrees) because the tails were immersed in high-intensity turbulence 

and chaotic airfow caused by phenomena, such as stalled wing wakes or vortex “bursting.” Te 

resulting randomly varying structural response of the tails caused by the applied bufet loads 

severely degrades the fatigue life of these components. Tail bufet loads have necessitated structural 

modifcations for some airplanes, or even mandated maneuver limitations for others. In addition 

to structural modifcations, special and costly inspections are required to check for damage 

due to bufet loads. Analysis based on available usage history of two aircraft confgurations 

suggests that the tail surface fatigue life could be doubled if the tail stresses could be reduced by 

only 10 percent. 

In the case of the F/A-18, an aggressive problem-solving exercise by industry, DoD, and NASA over 

a period of years had resulted in a passive approach to the fn bufet issue. Specifcally combined 

modifcations consisting of structural cleats at the bottom of the vertical tails and small fences on 

the wing leading-edge extension (LEX) were incorporated on operational aircraft to meet fatigue 

requirements. Te efects of diferent LEX lengths on tail bufet loads were examined on an F/ 

A-18 model in the Langley 30- by 60-Foot Full-Scale Tunnel by researcher Gautam H. Shah. 

McDonnell Douglas (now Boeing) also examined other passive techniques to increase fatigue 

Innovation in Flight 221 
CONTROL OF AEROELASTIC RESPONSE: TAMING THE THREATS 

life of its aircraft. Because these types of passive techniques do not solve the bufeting problem 

for all fight conditions, an active tail bufet alleviation study was initiated. With active control 

techniques ofering so much promise for solving other aeroelastic problems, it was only natural that 

research would be initiated to reduce the bufeting response of vertical tails. Except for some work 

in France and the aforementioned eforts of Heeg, little research had been conducted previously 

on the active control of bufeting response. 

Langley and its DoD, industry, and international partners have conducted extensive research on 

the fundamental aeroelastic phenomena associated with tail bufet and have conducted several 

studies to assess and demonstrate active control to reduce the loads and stresses encountered. Led 

by Robert W. Moses, a series of wind-tunnel tests have been performed in the TDT since 1995 to 

develop and mature active control concepts. Te initial activity, known as the Actively Controlled 

Response of Bufet Afected Tails (ACROBAT) project, focused on the F/A-18 confguration that 

had experienced signifcant operational tail bufet loads due to vortex bursting at high angles 

of attack. 

A 1/6-scale, sting-mounted model of the F/A-18 served as the ACROBAT study workhorse. 

Objectives of the project were to apply active controls technology using various force producers, 

such as aerodynamic control surfaces and piezoelectric structural actuators, to alleviate bufeting 

for twin vertical tails; and to determine detailed unsteady aerodynamic data at high angles of attack 

with the bufet alleviation controls on and of. A variety of vertical tail surfaces was fabricated for the 

tests, including rigid (nonfexible) as well as fexible surfaces. Extensive instrumentation, including 

strain gauges and accelerometers, was used to obtain steady and unsteady characteristics during 

the tunnel tests. Te investigated angle-of-attack range varied from 20 to 40 degrees. Early results 

of the ACROBAT studies indicated that control systems using either the rudders or piezoelectric 

actuators worked best for suppressing the bufeting loads and for angles of attack up to about 30 

degrees, both approaches were equally efective in bufet alleviation. Exhibiting a strong interest 

in applying the rudder and piezoelectric actuators to reduce tail bufet loads, Daimler Benz 

Aerospace of Germany participated in the tests through a set of international agreements in 

aeroelasticity research. 

Trough an interagency agreement, NASA joined forces with the Air Force Research Laboratory 

(AFRL) to develop bufet scaling techniques by comparing the ACROBAT unsteady pressure data 

with full-scale, low-speed pressure measurements on an F/A-18 aircraft tested in the 80- by 120-

Foot test section of the National Full-Scale Aerodynamics Complex (NFAC) Facility at NASA 

Ames. Te scaling technique was later demonstrated by Moses and Shah through comparisons 

with unsteady pressures measured on a vertical tail of the NASA High Angle of Attack Research 

222 Innovation in Flight 
CONTROL OF AEROELASTIC RESPONSE: TAMING THE THREATS 

NASA’s F/A-18 High Angle of Attack Research Vehicle uses smoke 

injected into vortex fow to illustrate vortex breakdown position 

for angles of attack of 20 degrees (top) and 30 degrees (bottom). 

Vehicle F/A-18 aircraft at NASA Dryden while the airplane was fying at high angle-of-attack 

conditions. In addition to the scaling technique, the spatial correlation of the bufet, a random 

process, was demonstrated by Moses for the ACROBAT pressure data and comparisons with 

limited aircraft data. Tis information subsequently proved vital to modeling unsteady bufet 

pressures on the F-22 confguration for evaluating active control system models or minor changes 

to the tail structures and materials. 

Building upon the successful ACROBAT Program, the collaborative F/A-18 tail bufet suppression 

studies were later expanded to include participation by Australia and Canada (operational users 

of the F/A-18). Te research program was coordinated by AFRL and was conducted under the 

auspices of Te Technical Cooperation Program (TTCP). Te collaborative program involved 

Innovation in Flight 223 
CONTROL OF AEROELASTIC RESPONSE: TAMING THE THREATS 

tests of a full-scale F/A-18 empennage, including assessing the use of commercially available 

patch piezoceramic actuators to provide bufet alleviation. Tis ground test program used the 

International Follow-On Structural Testing Program (IFOSTP) facility located at the Australian 

Defence Sciences & Technology Organisation. Te purpose of this collaborative program was to 

investigate the feasibility of piezoceramic actuators to withstand and control severe bufet loads 

applied to the F/A-18 vertical tails. Open- and closed-loop tests of the concept’s efectiveness were 

completed successfully during ground tests in 1997 and 1998, respectively. Tis highly successful 

cooperative program has served as a pathfnder for future bufet loads alleviation research. 

In 1998, another test entry of the F/A-18 model in the TDT involved a project known as Scaling 

Infuences Derived from Experimentally-Known Impact of Controls (SIDEKIC). In this study, 

Bob Moses and his team cooperated with the Australian Aeronautical and Maritime Research 

Laboratory (AMRL) to correlate data during mutual investigations of the F/A-18 confguration. 

Because the F/A-18 is also fown by Australian military forces, mutual sharing of data and 

technology on tail bufet alleviation was especially valuable to the participants. New vertical tails 

were fabricated for the TDT F/A-18 model, and an efort was made to match the arrangement of 

piezoelectric actuators used during full-scale airplane ground tests at AMRL. One of the model’s 

vertical tails used both an active rudder and active piezoelectric actuators for controlling responses 

over specifc frequency ranges. Tis approach to providing bufet alleviation was referred to as 

a “blended” system because two diferent actuator technologies were combined by Bob Moses. 

Several other control schemes were evaluated during these tests, including one contributed 

by Boeing. 

Te F/A-18 research program’s contributions and other studies of the F-15 confguration resulted 

in extensive studies using fow visualization, fow velocity measurements, pressure transducers, 

and response gauges. Te state of the art for predicting bufet loads and fatigue life has rapidly 

matured and has been updated with tests of additional confgurations. In 1999, Langley and 

AFRL conducted a cooperative TDT investigation of vertical tail bufeting characteristics of an 

early model of the F-22 fghter. Led by Bob Moses, the investigation used a 13.3-percent-scale 

model of the F-22 equipped with various types of instrumentation and sting-mounted in the TDT 

for testing at low Mach numbers (up to 0.12) and high angles of attack. A variety of measurements, 

including fow visualization techniques, was used to identify key features of the bufet-inducing 

fows. Model confguration variables such as wing leading-edge fap defection were also assessed, 

and the general results obtained for the F-22 model were compared with the F/A-18 results for 

correlation and general conclusions. A rudder on the starboard-side vertical tail was actively 

controlled using feedback of bufet-induced accelerations near the tip of that tail. Tis approach 

proved quite efective in reducing bufet-induced responses. 

224 Innovation in Flight 
CONTROL OF AEROELASTIC RESPONSE: TAMING THE THREATS 

F-22 model mounted in Transonic Dynamics Tunnel for tail bufet studies. 

Highly successful demonstrations of the blended control system in the TDT, under the SIDEKIC 

Program presented earlier, led to full-scale actuator development, including systems-level 

considerations of cost and operational environmental conditions for electronic components. To 

validate the latest technologies in piezoceramic actuators and piezo drive amplifers on an F/A-18, 

another international ground test program was formed in 2002 under the auspices of the TTCP. 

A series of ground tests were conducted in the Australian IFOSTP facility, as before; however, this 

test concentrated the piezo actuators near the vertical tail tip to control bufet-induced responses 

there and near the rudder to reduce vibratory response in the bending mode. Completed in 2004, 

this ground test program successfully demonstrated the feasibility of the “blended” control system 

to alleviate bufet loads as designed for an aircraft. 

Te success of international collaboration has peaked interest in the next generation of vertical tail 

active bufet suppression systems and the capability to predict systems performance. Tis interest 

was especially intense in 2001, when an early version of the Lockheed Martin X-35 Joint Strike 

Fighter aircraft experienced high tail bufet loads when attempting to fy at high angles of attack. 

Bob Moses was contacted by Lockheed Martin for consultation and assistance in the development 

of an in-house capability to design for tail bufet. Together, this team implemented an aggressive 

wind-tunnel test and tool development program that benefted from Langley’s experience in 

model instrumentation, data acquisition and analysis, and predictive tool development. Within 

Innovation in Flight 225 
CONTROL OF AEROELASTIC RESPONSE: TAMING THE THREATS 

15 months of the initial consultation, this team had scaled and implemented wind-tunnel pressure 

measurements into design methods not only to predict the bufet loads on existing designs, but 

also to redesign the tails to mitigate bufet-induced fatigue. Plans are underway to implement 

similar capabilities at Boeing to augment its current bufet loads design capabilities. 

Status and Outlook 

Te challenges inherent in active control of aeroelastic responses have been the target of research at 

Langley Research Center for over 35 years. Progress in defning the complex transonic aerodynamic 

fow felds of importance has increased tremendously, as has the ability of CFD methodology 

to predict these phenomena. Experimental demonstrations in the TDT and in fight have been 

impressive and provided confdence in the ability of technology to alleviate aeroelastic problems 

using active control techniques. 

Nonetheless, there has been very little application of active control for fxed-wing aircraft in the civil 

or military sectors. Signifcant widespread application barriers remain, especially issues regarding 

the additional complexity and cost of active controls. As yet, the cost-beneft consideration has not 

been in favor of such systems. More importantly, the critical safety-related margins comfortably 

enjoyed today for aeroelastic issues such as futter are the result of years of experience in worldwide 

operational scenarios. 

Using active controls for control of aeroelastic response within the U.S. commercial transport 

industry has not signifcantly advanced beyond Lockheed’s early application to the L-1011 

confguration in the 1970s. Meanwhile, the European Airbus Industrie Consortium has explored 

numerous areas using active controls for drag reduction, active center-of-gravity control, active-load 

control, variable-camber control, and active sideslip control. Airbus has subsequently applied the 

early principles derived from the Lockheed eforts by designing a wing load alleviation system into 

its A-320 transport from its early design, thereby reducing wing weight and improving passenger 

ride quality in turbulence by actively controlling wing bending moments. Te A-320 entered 

commercial operations in 1988. Military applications of the technology have now progressed to 

in-depth assessments and fight evaluations for control of vertical tail bufet concerns at high 

angles of attack and for limite-cycle futter alleviation for wing/store combinations. Te successful 

application of active controls by McDonnell Douglas to production versions of the F/A-18 prior to 

the F/A-18E/F represents a milestone in the technology. 

226 Innovation in Flight 
The Joined Wing: Diamond in the Sky 

Concept and Benefts 

One of the most attractive aircraft design areas for innovators has been the challenge of optimizing 

trade-ofs among aerodynamic efciency, structural efectiveness, and aircraft weight. Although 

requirements for aerodynamic performance may stimulate the designer to consider wings with 

very high aspect ratios, the attendant structural weight penalties and requirements for strength 

and rigidity for such confgurations limit the geometric approaches that may be used for a feasible 

design. For conventional confgurations, which use cantilevered-wing arrangements, the loads that 

must be safely accommodated by the wing-fuselage structure include critical bending moments 

induced by the aerodynamic and weight loads on the wing panels. Such loads always play a critical 

role in the aerodynamic and structural integration of new aircraft. Since the advent of heavier-thanair fight, the aeronautical community has continually investigated unconventional and innovative 

schemes to optimize these trades. 

One approach used by designers has been to lay out confgurations that use tandem fore-and-aft 

wings that are joined to form a diamond-type shape when viewed from above and from the front 

or rear. Depending on the specifc geometry involved, potential reductions in structural weight or 

improved aerodynamic characteristics may be generated. Early designs included a glider, designed 

by Reinhold Platz in Europe in 1920, and a rudimentary multijoined-wing airplane built by Ben 

Brown of the University of Kansas in 1932. A more recent joined-wing confguration is the “box 

plane” concept designed by Luis R. Miranda of the Lockheed-Georgia Corporation in the early 

1970s. Te box plane concept has been proposed by Lockheed Martin for potential applications 

for commercial transports, freighters and military tankers. 

Also in the 1970s, Julian Wolkovitch of ACA Industries advanced a joined-wing concept wherein 

the root of the rear wing was intentionally designed to be at a higher elevation than the front wing. 

With this arrangement, the fore-and-aft wings form a truss structure that relieves some of the 

loading from the front wing and signifcantly stifens the structure. Tis joined-wing concept is 

obviously a highly integrated approach to aerodynamic and structural design. 

For aircraft applications, the principal beneft of this particular joined-wing confguration is that 

the rear wing acts as a strut brace to support some of the wing bending moments. Tis loading 

feature can be exploited as a reduction in wing weight or as an increase in wing span (aspect 

ratio), or a combination of both. A secondary beneft of the joined-wing confguration is that the 

nonplanar arrangement of lifting surfaces can theoretically result in lower induced drag for a given 

span and weight. 

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Boeing concept for a joined-wing fight demonstrator. 

In addition to these fundamental considerations, the joined-wing confguration ofers other 

potential benefts that are unique to its unconventional geometry. For example, because of the 

wings’ diamond-shaped arrangement when viewed from above, the lifting surfaces can be used 

to support various types of radar antennas to provide a 360-degree azimuth coverage with little 

or no aerodynamic penalty. Equipped with wing conformal electronically scanned array radars, 

a joined-wing research aircraft could ofer a substantial increase in radar capability and improved 

range and endurance. Te multiple lifting surfaces result in a compact confguration, requiring 

less deck space for shipboard military naval applications. In another potential military application, 

the relatively stif outer wing of a joined-wing tanker (with a forward/rear wing joint at about 70 

percent of the semispan) could accommodate refueling booms on fairing pods at the two outerwing joints. Tis capability would enable simultaneous air-to-air refueling of two aircraft, which is 

not currently possible with today’s tanker confgurations. 

An interesting potential application of the joined-wing confguration would be for advanced 

aircraft designed for aerial applications, such as crop treatment and seeding, or for fre fghting. 

In these potentially hazardous missions, structural robustness and crashworthiness can be more 

important than aerodynamic efciency or structural weight. Te rigidity and structural strength 

aforded by the joined-wing geometric arrangement ofers the promise of signifcantly enhanced 

safety and reduction of fatalities. In another civil application, the use of the joined-wing layout 

with its inherent rigidity might signifcantly increase the futter speed encountered by conventional 

high-altitude sensor vehicles, such as those used to monitor earth environmental and resource 

characteristics. Tese vehicles conventionally have been confgured with very high-aspect-ratio 

wings that can result in undesirably low futter speeds. 

Yet another potential application of the joined-wing concept involves the design of supersonic 

aircraft confgurations with relatively low sonic boom levels. Te intensity of sonic booms is a 

strong function of vehicle length, and a joined-wing confguration has a greater “efective length” 

because of the elevated rear wing junction to the vertical fn. Additionally, current concepts for 

228 Innovation in Flight 
THE JOINED WING: DIAMOND IN THE SKY 

engine nacelles that reduce takeof and landing noise have rather long silencers extending aft from 

the wing trailing edge. Tese nacelles provide a natural location for the wing-tail joint and may 

provide some bending or torsional moment relief to the wing. 

Challenges and Barriers 

Te joined-wing concept has faced many challenges and barriers from technical considerations 

in the areas of structures, aerodynamics, and stability and control. NASA, industry, DoD, and 

universities have addressed many of these issues with analytical and experimental studies. 

Te greatest structural beneft of the joined-wing confguration occurs when the front- and rearwing joints are all fxed cantilever connections. Unfortunately, this arrangement results in a 

structure that is more difcult to analyze (referred to as statically indeterminate) and can result in 

counterintuitive characteristics. Another major challenge results from the fact that typical joinedwing confgurations are designed with the root of the rear wing above the front wing, so the rear 

wing is loaded in combined bending and compression. Te rear wing, which acts as a compression 

strut, must be designed with enough stifness not to buckle. Typical low-fdelity structural weightestimation tools used during early conceptual and preliminary design are not capable of determining 

realistic loads, moments, stresses, or weight of a joined-wing structure. 

Te necessity for more sophisticated structural design methods and capability—early in the vehicle 

conceptual development—is a powerful economic barrier for companies that might otherwise 

consider a joined-wing confguration. Because of the lack of detailed design experience with such 

an unconventional structure, the potential advantage of lower structural weight is regarded as a 

signifcant technical risk. Companies have been reluctant to make the investment in design tools 

and training, and they have neither sufcient funding nor schedule margin to allow longer design 

evolution/iteration to occur in the detailed design. Any nontraditional structural arrangement 

will encounter similar barriers when the groups performing detailed structural design within the 

companies are faced with such a radical departure from established methods and procedures. 

In the area of aerodynamics, the most dominant challenge to the joined-wing confguration is the 

minimization or elimination of separated fow at wing and fuselage junctures and aerodynamic 

component interference efects across the fight envelope, including cruise, takeof, and landing. 

With the added component juncture formed by the wing joint, the joined wing provides added 

challenges to the aerodynamicist. If the confguration experiences unacceptable juncturefow characteristics (particularly at high subsonic cruise conditions), overall drag levels may be 

signifcantly higher than those of conventional transports. 

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Te joined-wing confguration may also exhibit unique challenges in the critical area of propulsion 

integration. For some applications, engine nacelles may have to be located on lateral stubs on the 

fuselage near the confguration’s center. Aerodynamic interference efects from the forward wing/ 

fuselage components (particularly for high angles of attack or sideslip) may result in unsatisfactory 

engine inlet fow characteristics or inefcient propulsion performance at cruise. In addition, the 

engine efux may cause interference efects on the aft wing or vertical tail. 

Finally, inadequate design of the rear wing or vertical tail juncture may cause fow separation, 

which can result in a signifcant increase in drag and a large impact on stability and control. In 

addition, the overall consideration of trimmed lift for operational conditions across the envelope 

must be analyzed and the vehicle confgured to ensure satisfactory characteristics. Te relatively 

short moment arm of the aft wing control surfaces of most diamond-wing type joined wing aircraft 

aggravates the classical problem of longitudinal trim or lift trades at low-speed landing conditions. 

For a stable aircraft, the short-coupled rear wing may have to produce excessive download to trim 

the pitching moments experienced during various phases of fight, resulting in a signifcant loss of 

lift. Other approaches to joined-wing confgurations, such as an auxiliary aft-mounted tail surface, 

might be employed to alleviate unacceptable levels of lift loss due to trim. 

Many joined-wing confguration wind-tunnel models have exhibited a nosedown (“pitch down”) 

characteristic at moderate angles of attack below wing stall, thereby limiting the maximum lift of 

the confguration to less than desirable values. Te phenomenon is attributed to stalling of the front 

wing, resulting in loss of lift on the forward wing and a reduction in downwash onto the rear wing, 

which increases the pitch-down contribution of the rear wing. Although this efect is favorable 

as a natural stall-prevention mechanism for the airplane, it can severely limit the magnitude of 

attainable lift. Tus, longitudinal stability of the joined-wing design requires a careful integration 

of individual wing stall characteristics. 

Operational challenges specifc to joined-wing confgurations are relatively unknown because of 

the lack of applications and fight experiences with aircraft other than personal sport vehicles. 

Issues such as icing characteristics, detailed handling quality assessments, and other real world 

issues have not been assessed at the current time. 

Langley Activities 

NASA’s participation in research on joined-wing aircraft has involved Langley Research Center, 

Ames Research Center, and Dryden Flight Research Center. Te following discussion highlights 

critical activities at the participating Centers, with an emphasis on activities that have occurred 

230 Innovation in Flight 
THE JOINED WING: DIAMOND IN THE SKY 

at Langley. More detailed information on activities at Ames and Dryden is provided in references 

listed in the bibliography. 

Exploratory Study of Aerial Applications Aircraft 

In 1979, Julian Wolkovitch approached Joseph L. Johnson, Assistant Head of the Dynamic 

Stability Branch, with a request for a cooperative wind-tunnel test of an advanced joined-wing 

general aviation airplane designed for aerial applications. Te confguration, which the legendary 

Elbert L. (Burt) Rutan had designed, featured a tractor-propeller-driven, joined-wing layout with 

the rear wing joined at the mid-span location of the forward wing, which had winglets. Te pilot 

was located in the 18-percent thick vertical tail of the vehicle. Wolkovitch had crash resistance in 

mind as a primary design objective when he frst pursued the joined wing as a sport glider in 1974, 

and he and Rutan believed that the proposed agricultural plane design would ofer signifcant 

safety improvement over conventional designs. 

Because of its interest in providing data for advanced confgurations, NASA fabricated a scale 

model of the design and conducted a cooperative test in a 12-foot low-speed subsonic tunnel 

at Langley. Lead engineer for Langley during the exploratory tests was E. Richard White. Te 

tests were regarded as exploratory and limited because of the low Reynolds number of the test 

conditions, and all participants had expected premature fow separation on the wings and junctures 

due to lack of simulated fight conditions. Nonetheless, it was felt that any aerodynamic data on 

stability and control characteristics of this remarkable confguration would be of great interest to 

the engineering community. 

Advanced agricultural airplane model tested at Langley. 

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Te results of the test verifed the expected fow separation regions, especially at the wing-joint 

locations at moderate and high angles of attack. Of more concern, however, was the impact of fow 

separation at the rear wing-vertical tail juncture, which resulted in a loss of directional stability 

contributed by the thick, short-span vertical tail. Although the design was not subsequently pursued 

for a commercial product, this early test identifed a number of performance, stability, and control 

issues that have resurfaced as challenges throughout later studies of joined-wing vehicles. 

High Altitude Vehicle Flutter 

Aircraft fying above 100,000 ft must operate near the drag-divergence Mach number while 

generating high lift coefcients. For such fight conditions, thin supercritical airfoils are desirable. 

Cantilever wings employing these thin airfoils tend to be heavy or excessively fexible. For joined 

wings, however, reducing thickness-chord ratio gives only small penalties in structural weight and 

rigidity. Te net efect is that the joined wing can potentially increase the altitude and payload 

capabilities of very high altitude aircraft. A key consideration of this beneft is the joined wing’s 

impact on potentially catastrophic futter. 

In 1984, Langley’s Michael H. Durham and Rodney H. Ricketts of the Aeroelasticity Branch 

teamed for an analytical and experimental study of the joined-wing confguration’s benefts on 

futter characteristics of very high-aspect-ratio (21.6 and 42) vehicles. In the investigation, they 

studied two types of joined-wing models in the Langley TDT at Mach numbers of 0.4 and 0.6. 

Durham and Ricketts investigated semispan wall-mounted models of conventional and joinedwing designs, as well as full-span futter models, on the unique free fying cable-mount system 

used for futter testing in the TDT. Results obtained with the sidewall-mounted models compared 

characteristics of joined wings with conventional cantilevered wings of equal span, weight, and 

projected area. For each Mach number tested, Durham and Ricketts found the dynamic pressure 

for onset of futter for the joined-wing confgurations to be about 1.6 times higher than that of 

cantilever wings, verifying the joined wing’s expected benefts. Testing the cable-mounted full-span 

models provided more excitement and some unexpected results. Te lower aspect-ratio (21.5) fullspan joined-wing model experienced an aerodynamic instability and was destroyed in the ensuing 

out-of-control motions. In addition, the cable-mounted high-aspect-ratio full-span joined-wing 

model exhibited a symmetric futter mode that was remarkably unconventional. In this futter 

mode, the model displayed fore-and-aft motion as well as vertical motion. Observers noted that 

the model appeared to be performing a “butterfy stroke” similar to a swimmer. Durham studied 

the motion and developed an approach for analysis that correlated well with the experimental 

results for both futter speed and mode. He subsequently disseminated the investigation’s results at 

specialists meetings. 

232 Innovation in Flight 
THE JOINED WING: DIAMOND IN THE SKY 

Researcher Mike Durham with futter model of joined-wing high-aspect-ratio confguration. 

Joined-Wing Studies at NASA Ames Research Center 

While Langley was engaged in assessing the benefts of joined-wing vehicles for civil and military 

applications, similar eforts were underway at NASA Ames Research Center, including investigations 

of civil transport applications. Although not directly coordinated with Langley, this work mentions 

these studies for completeness and perspective on the scope of studies at Ames. 

As researchers at Ames began studying the joined-wing concept, they recognized that more 

sophisticated design and analysis tools would be required to properly assess performance trends 

that are dependent on structural weight and trimmed-drag prediction. In 1986, work began on 

a combined structural and aerodynamic analysis code that would be appropriate for conceptual 

design. Stephen C. Smith at NASA Ames and Ilan M. Kroo and John W. Gallman at Stanford 

University collaborated on this work. Tey based the aerodynamic model on a vortex-lattice 

representation of the confguration and included a coupled optimization routine to fnd optimum 

twist distribution and tail incidence to minimize induced drag and achieve pitch trim with fxed 

Innovation in Flight 233 
THE JOINED WING: DIAMOND IN THE SKY 

static stability. Te structural model was based on a fnite beam-element method with a coupled 

optimization to determine the minimum structural weight with maximum-stress and minimumgauge constraints. Tese tools allowed parametric studies of the efects of various confguration 

changes on structural weight and cruise drag. Smith, Kroo, and Gallman published the study 

results in 1987. 

Ames subsequently hired Gallman, and he incorporated these models into a full mission-synthesis 

model that performed a complete vehicle optimization subject to real world constraints, such as 

takeof and landing feld length, engine-out climb requirements, internal fuel volume and cruise 

range with IFR fuel reserves, static stability and trim over allowable center of gravity range, positive 

weight on nose wheel, structural loads and weights in compliance with FAR 25, and many others. 

Improvements to the analysis models included maximum trimmed lift capability, buckling margin, 

and futter prediction. 

In parallel with the conceptual design eforts, Ames supported Julian Wolkovitch’s company, 

ACA Industries, in designing and developing a manned fight demonstrator aircraft to develop 

a representative joined-wing structural arrangement and demonstrate satisfactory fying qualities. 

SBIR phase I and phase II awards funded this efort. A wind-tunnel test was conducted to measure 

the aerodynamic characteristics of a joined-wing research aircraft (JWRA), which was designed to 

use the fuselage and engines of the existing NASA AD-1 research aircraft. Te AD-1 had completed 

a very successful piloted fight program to demonstrate oblique-wing technology. Te JWRA was 

designed to have removable outer-wing panels to represent three diferent confgurations with the 

interwing joint at diferent fractions of the wing span. A 1/6-scale model of all three confgurations of 

the JWRA was tested in the Ames 12-Foot Pressure Tunnel to measure aerodynamic performance, 

stability, and control characteristics. Tese test results indicate that the JWRA had very good 

aerodynamic performance and acceptable stability and control throughout its fight envelope. 

Although the wind-tunnel results showed satisfactory performance, stability, and control, with no 

adverse interference drag using well-designed fairings at the wing-tail joint, the funds available for 

research were exhausted before the fight demonstrator vehicle could be fabricated. 

Ames design study results of commercial civil transports indicated that, for the specifc mission 

application chosen, the joined wing had a few percent higher direct operating cost. However, they 

also showed that several adverse characteristics of the design could probably be mitigated with 

further design. Chief among these was the larger wing size required because of poor trimmed 

maximum lift, a consequence of high tail downloads required to trim. Alternative high-lift systems 

that produce less pitching moment and longer fuselage layouts may have improved the trimmed 

lift enough to make the joined wing competitive with conventional confgurations. At the same 

234 Innovation in Flight 
THE JOINED WING: DIAMOND IN THE SKY 

Model of the Ames Joined-Wing Research Aircraft concept shows two of the three wing arrangements. 

Te 1/6-scale model of the Joined-Wing Research Aircraft in the Ames 12-Foot Pressure Tunnel. 

Innovation in Flight 235 
THE JOINED WING: DIAMOND IN THE SKY 

time, tailored composite tail structures may have increased stifness and buckling margin with less 

weight penalty, again improving the joined-wing performance relative to the conventional airplane 

arrangement. Alternatively, exploiting the wing strut bracing’s structural beneft while retaining 

the efcient trimming capability of a conventional horizontal tail may be an even more efcient 

confguration. Each potential design fx was regarded as beyond the scope of the Ames studies, 

which were concluded in 1993. Such approaches, however, could potentially make the joined wing 

attractive and successful. Te Ames experience shows that the joined wing, more than most other 

vehicle concepts, requires a well-established multidisciplinary design approach throughout the 

vehicle development process, from conceptual and preliminary design through detailed design. 

Participation in Boeing’s EX Program 

Te safety of U.S. Navy carrier battle groups depends strongly on an early warning of incoming 

aircraft and missiles launched by beyond-the-horizon enemies. For over 30 years the responsibility 

for providing early warning has been assigned to the Navy E-2C Hawkeye aircraft, which uses 

a 24-ft rotodome atop the vehicle to enclose its radar antenna. Anticipating the need for a more 

capable replacement surveillance aircraft as the E-2C reaches the end of its lifetime in the feet, the 

Boeing Defense and Space Group’s Military Airplane Division embarked on studies of a radical 

new joined-wing surveillance aircraft design in response to a new Navy program known as the 

Electronics Experimental (EX) Program in 1990. Te EX Program achieved Milestone 0 defnition 

in 1992, but the Navy did not pursue the program because of defense funding reductions. 

Te Boeing EX aircraft concept incorporated advanced active-aperture radar arrays in each joinedwing segment to create an ideal arrangement for the radar arrays and a more aerodynamically 

efective design than the conventional E-2C. Te joined-wing EX concept was only about 80 

percent the size of the larger E-2C, yet it incorporated four 31.5-ft wing-mounted radar apertures, 

compared with the single 22-ft aperture carried by the E-2C. 

In the early 1990s, the Navy E-2C Program Ofce approached NASA Langley researchers for 

discussions of a cooperative study of the EX confguration in the Langley 16-Foot Transonic 

Tunnel. In accordance with NASA’s mission to explore advanced confgurations of interest, Division 

Chief William P. Henderson and Branch Head Bobby L. Berrier agreed to Langley participation 

in the project, and researchers Richard J. Re, Jefery A. Yetter, and Timmy T. Kariya served as 

key Langley engineers on the Boeing-NASA team. In July 1993, the team tested a model of the 

EX design to evaluate longitudinal and lateral aerodynamic characteristics and the efectiveness of 

various control surfaces. Measurements were also made to determine the efects of the wings and 

fuselage on engine inlet fan-face total pressure distortions at angles of attack and sideslip. Te test 

236 Innovation in Flight 
THE JOINED WING: DIAMOND IN THE SKY 

program’s results showed that the initial EX confguration exhibited several regions of separated 

fow for all values of Mach number investigated, including cruise conditions. 

Artist’s concept of the Boeing EX joined-wing aircraft. 

Tree-view sketch of the Boeing EX confguration. 

Innovation in Flight 237 
THE JOINED WING: DIAMOND IN THE SKY 

Guided by the results of this frst tunnel entry, Boeing modifed the confguration’s wings, and a 

second entry in the tunnel occurred during October 1998. E. Ann Bare led Langley’s participation 

and was assisted by Wesley L. Goodman. Early test results indicated that undesirable fow separation 

still existed on the modifed confguration. Langley’s Steven E. Krist and Boeing provided additional 

analysis and guidance by conducting CFD analyses. One of the confguration’s more challenging 

fow separation areas was the juncture of the aft-wing root and the vertical tail. Aerodynamic 

drag caused by massive separation in this area resulted in large performance penalties for the 

confguration. Responding in an extremely timely fashion, Krist quickly analyzed the fow feld at 

the critical junction area using the OVERFLOW code and designed a leading-edge modifcation 

(“bump”) for the vertical tail that minimized the separation phenomenon. Technicians quickly 

fabricated the tail modifcation for the model and provided quick turn around for testing of the 

modifcation. Test results for the revised model showed that the new tail confguration dramatically 

reduced drag. Krist’s valuable contribution to the joint investigation was widely recognized and 

appreciated by all members of the Boeing-NASA team. 

In addition to the pioneering information provided on the aerodynamic characteristics of joinedwing confgurations, and the EX in particular, the test entries in the 16-Foot Transonic Tunnel 

and the interactions of the Langley and Boeing stafs provided the foundation for a follow-up 

NASA RevCon project to be discussed in a later section. 

Other Langley CFD eforts were also directed at the unconventional joined-wing EX confguration 

operating at transonic, separated-fow conditions. Neal T. Frink, Shahyar Pirzadeh, and 

Paresh Parikh calibrated an unstructured Navier-Stokes capability within NASA’s Tetrahedral 

Unstructured Software System (TetrUSS) to demonstrate the system’s ability to predict the shockinduced trailing-edge fow separation observed on the fore and aft wings. Te surface-fow patterns 

obtained with TetrUSS were in good agreement with experimental oil-fow data obtained in the 

tunnel tests. Computed pressures were also in good agreement with the experimental data. Tis 

study represented a signifcant contribution toward a broader goal of validating a next-generation 

CFD methodology for rapid and cost efective Navier-Stokes analysis and design of complex 

aerodynamic confgurations. 

Te NASA RevCon Program 

As previously discussed within the topic of the blended wing body concept, in 1997 Darrel R. 

Tenney, Director of the Airframe Systems Program Ofce, and Joseph R. Chambers, Chief of the 

Aeronautics Systems Analysis Division, formulated and proposed a new research program based 

on the selection of precompetitive advanced confgurations that would be designed, evaluated, 

238 Innovation in Flight 
THE JOINED WING: DIAMOND IN THE SKY 

fabricated, and test fown using remotely piloted vehicle technology at Dryden. Te program, 

known as RevCon, would be based on a 4-year life cycle of support for concepts selected. Initial 

reactions to the proposed program from NASA Headquarters and Dryden were favorable, and 

following intercenter discussions with the additional participation of Ames and Glenn, a formal 

NASA RevCon Program was initiated in 2000 that was to be led by Dryden. Robert E. McKinley 

led the RevCon activities at Langley under the RACRSS element of Airframe Systems. 

In June 2000, NASA’s Ofce of AeroSpace Technology selected nine aeronautical concepts in 

its initial RevCon Program, including a teamed efort by Langley (team lead) with partners 

from Dryden, Boeing (Phantom Works), Naval Air Systems Command (NAVAIR), and AFRL 

for the design, development, fabrication, and fight testing of a joined-wing integrated structures 

demonstrator. Te Air Force involvement in the program came about due to rapidly growing 

interest in surveillance unmanned air vehicles (UAVs). Te project would receive approximately 

Jef Yetter inspects the EX model in the Langley 16-Foot Transonic Tunnel in 1993. 

Innovation in Flight 239 
THE JOINED WING: DIAMOND IN THE SKY 

$300,000 from NASA for phase I research, and the industry-DoD partners were expected to commit 

similar levels of funding. Objectives of the 4-plus-year project were to (1) enable the integration of 

large radar apertures into smaller aircraft for improved detection range and resolution, (2) reduce 

drag and weight for improved aircraft speed and endurance, and (3) reduce system costs. Flight 

experiments would be conducted with a full-scale piloted research aircraft using a modifed U.S. 

Navy S-3 Viking fuselage with new joined wings. 

In an 8-month phase I activity, the team explored demonstration alternatives, conducted riskreduction experiments and analyses, and planned phase II details and costs. Te primary research 

and technology objectives of the Joined-Wing Flight Demonstrator (JWFD) Project fell into three 

broad categories: (1) aerodynamics, fight controls and fight characteristics; (2) multifunctional 

structures, and (3) wing-integrated RF apertures. During phase II, the demonstrator aircraft 

would be fabricated and fight tested. Within the RevCon Program, fight testing would focus 

on aircraft performance, fying qualities, fight-envelope expansion, and validation of structural 

behavior. Following the RevCon phase II fight test activities at Dryden, plans included U.S. 

Navy fight testing at Patuxent River, Maryland, to evaluate carrier suitability and the radar 

aperture performance. 

Langley’s Program Manager for the teamed phase I efort was Jef Yetter, manager of the Advances 

through Cooperative Eforts (ACE) Program of the Aerospace Vehicles Systems Technology Ofce. 

Te research Integrated Product Team (IPT) leaders at Langley were Phillip B. Bogert (structures), 

Steve Krist (aerodynamics), and James W. Johnson (electromagnetics). Te phase I and phase 

Tree-view sketch of the Joined-Wing Flight Demonstrator confguration. 

240 Innovation in Flight 
provide adequate authority. change, together 

minor sweep change, increased total span from 63 ft on the EX to 72 ft on the JWFD. Te JWFD 

planform, like that of the EX, permitted the integration of 31.5-ft conformal apertures into each 

of the four wings. 

THE JOINED WING: DIAMOND IN THE SKY 

II plans identifed the use of several unique Langley facilities, including tentative entries in the 

Langley 16-Foot Transonic Tunnel, the Langley 14- by 22-Foot Low Speed Tunnel, the Langley 

20-Foot Vertical Spin Tunnel, the Langley Electromagnetics Test Facilities, the Langley Structures 

and Materials Laboratory, and the Langley Nondestructive Test Laboratory. 

Te project would make extensive use of existing Navy fight vehicle hardware and new joinedwing hardware. Te 35,000-pound (takeof gross weight) JWFD would be assembled from new 

joined wings adapted to an existing Navy S-3 aircraft fuselage. Te forward and aft wings of 

the JWFD would contain integrated phased array antennas. Te forward fuselage, aft fuselage, 

and vertical tail would be modifed to accept the new wings. Te S-3’s existing wing would be 

terminated outboard of the fuselage sides and new wing stubs would be added to accommodate the 

pylon/engine installations. Te engines would be TF-34 turbofans (existing S-3 engines) provided 

from the Navy inventory. 

Te phase I aerodynamic design of the JWFD expanded upon knowledge gained from BoeingNavy-NASA studies of the earlier Boeing EX confguration. Te JWFD’s forward and aft wings 

were essentially identical to those for the EX, with supercritical airfoil sections and slightly diferent 

sweep and dihedral angles. Te JWFD’s wing span was increased from that of the EX in order 

to aileron area for desired roll control Tis with the 

Model of the Joined-Wing Flight Demonstrator in the Langley 14- by 22-Foot Tunnel. 

Innovation in Flight 241 
THE JOINED WING: DIAMOND IN THE SKY 

Te JWFD was designed to have 13 fight control surfaces consisting of inboard and outboard 

trailing-edge faps on the forward wing, inboard trailing-edge faps on the aft wing, upper and 

lower split trailing-edge faps on the outer-aft wing, trailing-edge faps on the wing tips, and the 

rudder. Leading-edge faps were provided on the forward wing for high lift during takeof and 

landing. Tis robust suite of fight controls made the JWFD an excellent platform for further 

control system development and optimization of handling qualities for joined-wing aircraft. 

Te project started its phase I risk reduction and phase II planning activities on September 1, 2000, 

rapidly advancing the defnition of the JWFD. In aerodynamics activities, an exploratory lowspeed test of the JWFD confguration was immediately formulated, a model prepared, and tests 

conducted in the Langley 14- by 22-Foot Tunnel during February 2001 to determine performance 

of the high-lift system, static longitudinal and lateral-directional stability, control efectiveness, 

inlet fow qualities, and ground efects. Langley’s JWFD test leaders were Richard J. Re and 

Harry L. Morgan. Te confgurations tested, including takeof, approach, landing, and patrol 

confgurations, determined the efects of various control surface defections (individually as well as 

in combinations) on stability and control. Te leading- and trailing-edge faps of the forward wing 

were evaluated for high-lift capability, as were the wing-tip ailerons. On the aft wing, the efects 

of elevator, outboard fap, and speed-brake defections were investigated. Data were also obtained 

for maximum rudder defection. Runs were conducted with, and without, the landing gear and 

gear doors extended, and a limited number of fow visualization runs were conducted using 

tufts mounted on the wing tip and outboard portions of the forward and aft wings. Test results 

showed that the JWFD confguration had adequate stability and control characteristics for use as a 

fight demonstrator. 

One potential aerodynamic issue of the JWFD that concerned the research team was the possible 

existence of signifcant jet efects on the rear wing and vertical tail. In a head-on view, the engine 

nacelles of the JWFD were about evenly placed above the forward wing and below the aft wing, 

mounted close in to the fuselage on stubs. Te possibility therefore existed that the jet efux could 

cause interference efects on the aft wing and tail, particularly at high angles of attack. Te AFRL 

initiated a limited CFD investigation of powered efects using COBALT, a Navier-Stokes fow 

solver for unstructured grids, but none of the cases involved high angles of attack and the results 

were inconclusive relative to the suspected critical conditions. 

Steve Krist’s IPT team conducted CFD analyses with OVERFLOW, a Reynolds Averaged NavierStokes code for overset structured grids. CFD analyses of the joined-wing confguration were 

performed across the operating speed range, fow characteristics for the wing-body, wing vertical 

242 Innovation in Flight 
THE JOINED WING: DIAMOND IN THE SKY 

tail and fore/aft wing junctures were examined, and estimates of air loads were generated. Optimal 

engine inlet orientations were defned for good infow to the fan face, and drag-rise characteristics 

were calculated to verify the aerodynamic efciency of the joined wing design. Flow separation 

at the aft wing-vertical tail juncture of the JWFD was considerably improved over that discussed 

for the earlier EX confguration. Tis improvement resulted from the juncture of the aft-wing 

leading edge with the vertical tail being much further aft on the JWFD than on the EX. Flow 

visualizations at Mach numbers ranging from 0.4 to 0.81 indicated that extensive separation on 

the lower portion of the vertical tail appeared as early as Mach 0.6 on the EX, but not until Mach 

0.78 on the JWFD. 

Computational results indicated that the two areas on the JWFD providing the greatest potential for 

reduction in drag were the forward-wing/aft-wing juncture and the aft-wing/vertical tail juncture. 

Flow separation at the forward wing/aft wing juncture occurred primarily at high angle-of-attack 

subsonic conditions where the compressive efect of the aft-wing leading edge resulted in signifcant 

spanwise fow on the upper surface of the outboard forward wing and the wing tip. Procedures 

were developed for redesigning this juncture using OVERDISC, a computational design tool 

that couples the CDISC inverse design method developed by Richard L. Campbell of Langley 

with the OVERFLOW fow solver. Initial attempts at CFD designs at Mach 0.45 experienced 

great difculty in controlling the local surface shape while meeting geometry constraints in this 

unconventional juncture. 

Problems at the aft wing/vertical tail juncture arose at transonic conditions, resulting in a sharp 

drag rise at Mach 0.81. On the upper surface, a shock developed at the juncture and strengthened 

with increasing Mach number. On the lower surface, the separation at the trailing edge migrated 

forward with increasing Mach number until, at Mach 0.81, the fow on the lower portion of 

vertical tail separated just behind the aft wing leading edge. Procedures for using OVERDISC to 

design a fllet for this juncture—to mitigate the upper surface shock—are well developed, having 

been validated with Steve Krist’s studies on the EX confguration. However, there was insufcient 

time in the JWFD project to fully explore this procedure. 

Te NASA-Boeing team made substantial progress in the structural defnition and design of 

joined wings. A general structural arrangement for composite joined wings with integral radio 

frequency apertures was prepared, side-of-body connections for the engine nacelles were defned, 

and the required structural modifcations to the S-3 airframe were identifed. Te team also 

generated detailed static and dynamic fnite element models, performed loads and stress analysis of 

critical load cases to verify the wing-fuselage attachment concept, and performed initial structural 

element sizing. A conceptual design for an innovative fber optic wing-shape sensing system was 

Innovation in Flight 243 
THE JOINED WING: DIAMOND IN THE SKY 

CFD predictions of pressures, streamlines, and fow over the Joined-Wing Flight 

Demonstrator for a Mach number of 0.7 and an angle of attack of 0 degrees. 

Computational simulation of power-induced fow on the 

RevCon Joined-Wing Flight Demonstrator. 

also developed. Te system would have computed in-fight wing deformations from fber optic 

measured strains, thereby providing information needed for the phased-array application. Te 

system would also have been a key building block for future in-fight health monitoring systems 

for other applications. 

244 Innovation in Flight 
THE JOINED WING: DIAMOND IN THE SKY 

Boeing and NASA continued eforts to defne the analytically redundant fy-by-wire control system 

of the JWFD, and simulations showed that the fight control system was robust. Boeing used the 

simulation to assess sensitivity to actuator sizing and rates. 

In the area of electromagnetics, single array element models were built and tested, while analytical 

tools were developed and validated. A full-scale working model of the probe-fed element was 

built and chamber tested. Conceptual designs were completed for the fight control actuation, 

high lift, hydraulics, electrical, ECS, and fuel systems. Te designs focused on using existing S3 subsystems and components available from the existing inventory. In addition to component 

parts, the Navy identifed a specifc S-3 airplane for use by the JWFD project. Finally, the fighttest team developed a draft test plan that identifed all required prefight qualifcation testing, 

indicated necessary fight-test instrumentation, and outlined an approach for obtaining airplane 

fight qualities, low-speed performance and fight-envelope expansion. 

Brassboard testing of Joined-Wing Flight Demonstrator array 

element at Langley 

Te team submitted the fnal report on the phase I JWFD study results in April 2001. Unfortunately, 

funding priorities within the participating government agencies were directed elsewhere following 

the initiation of the RevCon Program. Te Navy and the Air Force were unable to meet their 

shares of the required funding commitments, and NASA’s portion of the funding was redirected to 

providing a return-to-fight capability for the NASA X-43A (Hyper X) Program following the X43A accident on June 2, 2001. NASA terminated its RevCon Program on September 30, 2001. 

Although the RevCon Program was terminated before phase II could be undertaken, the NASADoD-industry team signifcantly advanced the defnition of a joined-wing aircraft system and 

developed a practical conceptual design for a manned fight demonstrator. Progress was made 

Innovation in Flight 245 
THE JOINED WING: DIAMOND IN THE SKY 

in a variety of risk reduction areas and the team developed a viable project plan, cost estimates, 

work breakdown structure, and defnition of responsibilities between the partners. Because of this 

activity, the technical community now has a much better understanding of what it would take to 

design, build, and fy a joined-wing technology demonstrator of this type. 

Status and Outlook 

Joined wing aircraft application remains centered on surveillance, providing a means for integration 

of large apertures into compact aircraft for reduced cost and increased sensor performance. Current 

funding for concept development is being provided by the Air Force Research Lab (AFRL) as a 

part of its SensorCraft initiative. A series of contracts have been awarded to Boeing that focus 

on the viability of the joined wing concept as a sensor platform. Te contracts include systems 

studies for concept refnement and for defning an advanced technology demonstration (ATD) of 

the concept; a contract for Aero Efciency Improvements (AEI) that addresses the aerodynamic 

design of the joined wing sensor platform and the aero-elastic characterization of the joined wing 

structure; a contract that is part of the Very Afordable Advance Technology Engine (VAATE) 

program that addresses energy management, including secondary power, electrical power generation 

and thermal management; and a contract (a cooperative AFRL/Boeing program) that addresses 

the development of a structurally integrated X-band aperture and a full-scale wing conformal 

UHF aperture. 

246 Innovation in Flight 
The Vortex Flap: Effciency and Versatility 

Concept and Benefts 

Highly swept wings or other surfaces exhibit strong vortical fow over their upper surfaces during 

fight at moderate or high angle-of-attack conditions, such as those associated with takeof, landing, 

or strenuous maneuvers. Te vortical fow’s benefcial infuence on the integrated wing aerodynamic 

behavior results in greater lift for takeof and maneuvers, better control of the aerodynamic center’s 

location, and relatively similar fow felds over a wide range of angle of attack and Mach number. 

Many contemporary aircraft, including the Concorde supersonic transport and highly maneuverable 

fghters such as the F-16 and F/A-18, use vortex fows to enhance aerodynamic behavior through 

the mechanism of “vortex lift” across the range of operational conditions. 

Te F-16 (left) and the F/A-18 (right) use vortex lift for improved maneuverability. 

Unfortunately, the generation of vortex lift by wing leading-edge fow separation also results in a 

very undesirable byproduct: a loss of aerodynamic leading-edge thrust (or leading-edge suction) that 

results in a dramatic increase in drag for a typical highly swept confguration. In contrast, wings 

of conventional aircraft having lower sweep exhibit leading-edge thrust produced by attached fow 

over the wing, thereby reducing aerodynamic drag. Rather than producing thrust, the leadingedge force for highly swept wings at high angles of attack is redirected to a position normal to the 

wing surface where it augments normal force, but no longer has a benefcial impact on drag. 

Te vortex-fap concept involves the use of specially designed wing leading-edge faps that modify 

undesirable leading-edge fow separation behavior. Tis approach provides the aircraft designer 

with options to design highly swept wings with geometric features that recover a portion of the 

lost leading-edge thrust without compromising other aerodynamic characteristics, such as stability 

and control. Using this concept, the designer can reorient part of the vortex-force vector forward 

instead of directly normal to the chord plane. 

Innovation in Flight 247 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

Te vortex-fap concept. 

Te primary mechanism of the vortex fap is depicted in the sketch. Vortical leading-edge fows 

are depicted for a representative highly swept confguration having a conventional leading edge 

(left-wing panel) and a specially designed vortex fap that is defected from underneath the wing 

leading edge about a pivot point on the lower surface (right-wing panel) at a high angle of attack. 

As indicated in the sketch, fow separates over the conventional left leading edge, inducing the 

previously discussed vortex-lift force component normal to the wing surface. On the right wing 

panel, the vortex fap reduces the vortex core’s strength and size because of the leading-edge 

defection (camber efect) and leads to a vortex path that is redirected along the leading edge. 

Te result is a suction force that acts on the defected fap in a forward, drag-reducing direction. 

Furthermore, the vortex also functions as a rotating fuid cylinder to turn the fow around the 

leading edge onto the wing upper surface, thereby promoting a smooth transition to attached fow 

on the wing. 

Both civil and military aircraft can use the vortex-fap concept’s potential benefts. For example, 

a supersonic transport or supersonic business jet that uses a wing with high leading-edge sweep 

for efcient supersonic cruise capability could use the improved L/D ratios provided by the fap 

for enhanced takeof performance, thereby permitting the use of lower engine thrust settings and 

248 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

resulting in lower levels of community noise. Military aircraft could use the vortex fap’s benefcial 

efects for signifcant improvements in maneuvering performance, particularly at transonic 

conditions where improvements in turning performance during high angle-of-attack maneuvers in 

close-in combat are extremely signifcant. 

In addition to the vortex-fap concept’s performance-enhancing potential, innovative applications 

of other vortex-fap confgurations, such as upper-surface faps, wing apex faps, and diferentially 

defected leading-edge vortex faps (for aircraft roll control), ofer the potential for additional 

improvement of performance, stability, and control characteristics. 

Challenges and Barriers 

Before designers can apply this revolutionary concept for vortical fow control to production aircraft, 

numerous issues need to be addressed and resolved. Perhaps the most constraining barrier to the 

general application of the vortex fap is its inherent limitation for use on highly swept wings. Some 

of the other more important challenges and barriers involve aerodynamics, structural design and 

operational deployment issues, impacts on aircraft fying qualities, weight penalties, maintenance 

issues, and full-scale fight demonstrations of technology readiness. 

Aerodynamic issues that have inhibited the application of vortex-fap technology begin with 

a fundamental understanding of the fow physics involved in the concept. Factors such as the 

sensitivity of vortical-fow physics to geometric wing design variables, including the efects of 

wing-sweep angle and leading-edge radius, must be defned and incorporated in robust design 

procedures. Relative stability of the vortical-fow pattern produced by the vortex fap must be 

predictable and consistent across the operational range of candidate aircraft. Tus, the aerodynamic 

maturity of the vortex fap concept must be ensured from the perspectives of fuid physics and 

operational applications at full-scale conditions involving large changes in the values of Mach and 

Reynolds number. 

Te vortex-fap concept’s impact on aircraft stability, control, and handling qualities also demands 

in-depth research to ensure that undesirable behavior is not encountered in terms of changes in 

aircraft trim requirements, stability variations, control efectiveness, and aircraft maneuverability. 

For example, the use of diferentially defected leading-edge vortex faps for roll control would 

not be acceptable if large amounts of adverse yawing moments (yawing moments that result in 

degraded roll response) are encountered. In addition, the potential for degradation of handling 

qualities because of vortex bursting or vortex instability due to aircraft dynamic motion efects 

must be evaluated. 

Innovation in Flight 249 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

Structural design barriers for the vortex fap include providing acceptable levels of complexity 

and weight for fap hinges, actuation devices, and structural loads. In particular, comparisons 

of results of performance or penalty trade studies between defectable vortex faps and other 

approaches, such as the use of fxed conical wing leading-edge geometries that do not use leadingedge devices (e.g., design approaches used by the F-106 and F-15), must be resolved in favor of the 

vortex-fap concept. Other associated challenges for military applications include the impact of 

leading-edge structural discontinuities and details on aircraft signature characteristics, such as 

radar cross section. 

Langley Activities 

Langley Research Center has a rich legacy of expertise in vortex-fow technology. Researchers at 

Langley had conducted brief studies of low-aspect-ratio delta wings in the 1930s; however, the 

prediction of extremely poor low-speed fying characteristics and the absence of propulsion systems 

for high-speed fight resulted in a loss of interest within the Center’s research thrusts. During the 

latter stages of World War II, international research rapidly increased on the benefcial impact of 

wing sweep on aircraft performance at transonic speeds. By the war’s end, renewed eforts of the 

NACA, industry, and military organizations were initiated and focused on the advantages and 

problems of swept-back and delta wings. As expected, major challenges ensued at takeof and 

landing conditions because of the wing fow separation problems encountered as wing sweep was 

increased. Langley’s research on the aerodynamics of swept and delta wings began to accelerate and 

intensify, leading in turn to pioneering research on vortical fows. 

One interesting example of some early research being conducted at Langley on vortical-fow efects 

occurred during 1946 when the characteristics of the German Lippisch DM-1 glider were explored 

in the Langley 30- by 60-Foot (Full-Scale) Tunnel. Tis delta-wing research aircraft, which was 

captured by Allied forces and brought to the United States for analysis, had been designed to 

explore the low-speed handling characteristics of delta confgurations. Langley’s wind-tunnel testing 

indicated highly nonlinear lift variations with angle of attack, and studies of surface fows using 

wool tufts revealed peculiar swirling patterns that were ultimately attributed to the impingement 

of vortical fow felds on the wing’s upper surface. Researchers found that the lift increase exhibited 

by the airplane at high angles of attack could be attributed to vortical fow actions, and that the 

lift augmentation could be intensifed by modifying the relatively large leading-edge radius with a 

sharp-edged leading edge. Tis project was one of the frst full-scale aerodynamic studies of delta 

wings at Langley. 

250 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

Te Lippisch DM-1 glider captured by the Allies (left) and undergoing tests in the Langley 30- by 60-Foot 

(Full-Scale) Tunnel (right). 

Aerodynamic research on swept and delta wings at Langley reached a peak during the 1950s, 

with extensive eforts conducted in many wind tunnels at speeds from low subsonic conditions 

to supersonic speeds. Tese eforts were augmented by analytical studies, fight testing, and vastly 

increased intellectual knowledge of the fow physics associated with vortical fows. Te Center 

attained international recognition for its expertise in this area, and when the Nation turned its 

attention to supersonic civil and military aircraft in the late 1950s, Langley was poised to make 

valuable contributions in the design and application of vortex fows. 

Langley’s participation in the U.S. SST Program of the 1960s and the NASA SCR Program in the 

1970s provided additional opportunities to optimize highly swept confgurations and advance the 

state of the art of vortex-fow technology. 

In the late 1970s, the growing lethality of surface-to-air missile systems and the danger of deepstrike mission requirements led to intense interest in the U.S. Air Force for the development of 

supersonic cruise (“supercruise”) fghter confgurations. Te Air Force awarded several industry 

contracts for studies of supercruise fghter designs. Stimulated by these contracts and the obvious 

application of highly swept confgurations to the mission requirements, industry interacted with 

the Langley staf to share in the expertise and experiences gained by NASA with highly swept wing 

designs during the civil supersonic programs. Langley’s staf had developed a research program 

known as the Supersonic Cruise Integrated Fighter (SCIF) Program under the leadership of Roy V. 

Harris, Jr., to extend its technology to this class of military aircraft. Langley researchers designed 

and tested several in-house supercruiser fghters across the speed ranges in Langley facilities. Te 

objectives of SCIF were to focus in-house Langley aerodynamic and fight dynamic research toward 

feasible confgurations for supercruiser applications and to provide coordinated activities with 

Innovation in Flight 251 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

Model of a Langley-designed supersonic-cruise fghter concept (SCIF-IV) in the Langley Full-Scale Tunnel in 1977. 

industry teams competing for leadership in supercruiser technology. Subsequent to the initiation of 

its SCIF program, Langley joined several industry partners in cooperative, nonproprietary studies 

of supercruiser confgurations. 

One of the earliest meetings to promote a cooperative supersonic wing design occurred in March 

1977 when General Dynamics (now Lockheed Martin) met with Langley researchers to discuss 

a joint design efort involving several advanced supersonic wing candidates to be designed with 

NASA and tested in the supersonic Langley Unitary Plan Wind Tunnel and the transonic Langley 

High-Speed 7- by 10-Foot Tunnel. As part of the efort, General Dynamics assigned two engineers 

in residence at Langley for 4 months to interact in wing design methodology. Tests of new wing 

designs in 1978 indicated a supersonic performance improvement of about 30 percent compared with 

the basic F-16. At subsonic speeds, the modifed confgurations achieved the same performance as 

the F-16. Encouraged by these positive results, General Dynamics had committed to a Supersonic 

Cruise and Maneuver Prototype (SCAMP) concept that used a highly swept “cranked” (doubledelta) wing planform for supersonic cruise efciency. Refnement of this SCAMP concept later led 

to the development of the F-16XL prototypes by General Dynamics. 

252 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

During the development of the fnal SCAMP confguration, several cooperative projects used the 

confguration as a focus. A wide range of topics was studied, including supersonic store carriage 

concepts, low-speed stability and control of highly swept confgurations, and spin characteristics. 

One highlight of the 1978 research eforts was a study to provide transonic maneuvering lift at 

low drag. Te research eforts focused on concepts to alter the drag produced by forming leadingedge vortices. Edward C. Polhamus led Langley’s vortex research program, and his research 

group was within the Transonic Aerodynamics Division led by Percy J. (Bud) Bobbitt. Polhamus’ 

group had gained industry’s respect and close working relationships by making several signifcant 

contributions in cooperative programs as well as in specifc aircraft development programs, such 

as the F-16 and the F/A-18. In a keynote activity, John E. Lamar, James F. Campbell, and their 

associates joined in a cooperative study with General Dynamics. 

During the Langley tests, the NASA-General Dynamics team focused on wing design requirements 

for a 4-g transonic maneuver with a highly swept wing. Lamar conducted wind-tunnel and 

computational analyses to defne the “optimum” camber and shape for such a wing, but his 

experiences with vortex fows suggested that a simpler, more versatile solution might be provided 

by vortex-control concepts. In exploratory testing, the team found that certain combinations of 

defected full-span leading- and trailing-edge faps on a planar (no camber) wing produced almost 

the same drag improvements at transonic speeds as a specially designed and transonically cambered 

wing. Tis early application of vortex-fap principles also produced nearly the same supersonic L/D 

as a supersonic designed wing (also better than the F-16), a subsonic cruise L/D nearly as good 

as the value for the F-16 (and better than the supersonic design), and transonic maneuver L/D 

was midway between that of the F-16 and the fxed supersonic wing. Results obtained with these 

simple faps were very attractive from a practical design and fabrication standpoint and stimulated 

numerous other NASA studies. In-house and NASA-contracted projects included eforts that 

were focused on developing and validating the design methodology for the vortex-fap concept, as 

well as exploratory assessments of other innovative applications of vortex-control concepts using 

defected faps. 

Neal T. Frink of Langley and his associates conducted extensive pioneering wind-tunnel tests 

to evaluate the efects of wing-sweep angle and other geometric characteristics on vortex-fap 

efectiveness. Frink’s study provided a matrix of performance information for delta wings having 

sweep angles from 50 to 74 degrees with constant-chord vortex faps and formed the key basis for 

an approach to the design process. Frink initiated and pursued complementary theoretical studies 

that led the way for predicting overall forces and moments as well as detailed pressures for vortexfap confgurations. His eforts culminated in development of a leading-edge vortex-fap design 

procedure in 1982. 

Innovation in Flight 253 
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Camber study model used to develop optimum camber. 

Meanwhile, other NASA researchers and their industry peers pursued innovative applications of 

vortex-control technology based on lessons learned with the vortex-fap concept. NASA contractor 

Dhanvada M. Rao (initially of Old Dominion University and later ViGYAN Research Associates, 

Inc.) was particularly active in vortex-fap research. Rao demonstrated that reducing inboard length 

improved the fap’s efciency and that shaping the fap along the span improved fap efciency and 

vortex formation. Rao and an independent team led by W. Elliott Schoonover, Jr., of Langley and 

W. E. Ohlson of Boeing showed that increasing the fap size delayed inboard movement of the 

vortex and reduced drag. Additional contributions by Rao included the use of fap segmentation 

to reduce fap area while achieving the same L/D as without segmentation. He also was the frst to 

explore using vortex fap defections on individual wing panels to produce roll control. 

In 1981, Langley researchers Long P. Yip and Daniel G. Murri conducted studies of the efects 

of vortex faps on the low-speed stability and control characteristics of generic arrow-wing 

confgurations in a 12-ft low-speed tunnel at Langley. Although improved lateral stability and 

254 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

L/D were obtained in the tests, an unacceptable nose-up pitching moment was caused by the faps. 

Te researchers investigated geometric modifcation impacts on the vortex-fap confguration, 

including the fap’s spanwise length and the leading-edge geometry. A modifed fap concept, 

which included a defected “tab” on its leading edge, was found to alleviate the pitching-moment 

problem, and the fap confguration was then applied to SCAMP confguration models during 

the aircraft development program. Yip and Murri installed the tabbed vortex fap on a 0.18-scale 

free-fight model of the SCAMP (which had by then transformed into the F-16XL prototype) and 

conducted free-fight tests in the Langley 30- by 60-Foot (Full-Scale) Tunnel in 1982. Results 

indicated that the fap’s performance benefts could be obtained with no degradation in fying 

characteristics or pitch problems. 

Computational fuid dynamics study of vortex fap on a representative 

high-speed civil transport. 

Te vortex-fap concept’s civil applications have centered on supersonic transports and supersonic 

business jets. As part of the NASA SCAR technology program, Paul L. Coe led several wind-tunnel 

studies of vortex fap efects on aerodynamic performance, stability, and control of representative 

supersonic transport designs. Coe also contributed vortex-fap studies during the NASA HighSpeed Research Program, which focused on providing improved L/D for take-of operations of 

supersonic transports. During the program, improved low-speed aerodynamic performance was a 

major research focus, and the research team evaluated vortex-fap confgurations in several Langley 

tunnels, including the 30- by 60-Foot Tunnel and the 14- by 22-Foot Tunnel. Kenneth M. 

Jones, Kevin Kjerstad, and Victor Lessard conducted computational studies of the aerodynamic 

characteristics of attached-fow leading-edge faps and vortex-fap concepts at subsonic takeof 

and landing conditions. Using the USM3D computer code developed at Langley, they obtained 

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results that accurately predicted the primary vortex’s reattachment line in good agreement with 

experimental fow visualization. Forces, moments, and surface pressures compared well with the 

experimental data. 

Flight Research 

F-106B 

By 1983, research on the vortex-fap concept by Langley and its partners had progressed to the point 

that the next major step in technology maturation was required. Subscale models of generic aircraft 

confgurations with vortex-faps had been extensively evaluated in wind-tunnel and analytical 

studies; however, reliable extrapolation of model results to full-scale conditions and evaluations of 

potential efects of the concept on aircraft handling qualities were required. Following a review of 

vortex-fap technology progress, a joint NASA-AFWAL steering panel recommended a feasibility 

study for conducting a full-scale fight experiment using either an F-106, F-16XL, or the Advanced 

Flight Technology Integration (AFTI) F-111 research aircraft. James F. Campbell led a study team 

that examined the options and chose an F-106B airplane because of its wing geometry, fight 

characteristics, and accessibility to NASA researchers. NASA had used a two-place F-106B as a 

research aircraft for a variety of prior programs, including engine testing at NASA’s Lewis (now 

Glenn) Research Center and severe storms and lightning assessments at Langley. At that time, 

the aircraft was based at Langley where engineering staf and fabrication shops could be used for 

aircraft modifcations. With a wing leading-edge sweep of 60 degrees and transonic maneuver 

capability, as well as a second cockpit seat for observation of fow phenomena, the aircraft was 

ideally suited for an initial full-scale aerodynamic vortex fap fight assessment. Te advocacy 

eforts of Joseph W. Stickle, Chief of the Low-Speed Aerodynamics Division at Langley, were also 

instrumental in the selection process. 

In 1985, Langley held a national Vortex Flow Aerodynamics Conference to review the state of the 

art in vortex-fow technology under the joint sponsorship of NASA and AFWAL. At that meeting, 

several papers were presented on study results of vortex-fap applications to specifc confgurations, 

including the F-106. 

Te scope of studies required to implement and fight test the vortex fap on the F-106B included 

aerodynamic design (including wind-tunnel tests and analytical design), structural design and 

development of instrumentation, fabrication of fight hardware in Langley shops, installation 

of hardware and instrumentation by Langley aircraft technicians, development of simulation 

software, piloted simulator evaluations of aircraft handling qualities prior to fight, and fight 

256 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

tests of the modifed aircraft at NASA’s Wallops Flight Facility on Virginia’s Eastern Shore. A 

particularly valuable aspect of the fight program was the use of unique on-surface and of-surface 

fow visualization techniques that the Langley staf developed and implemented. 

Neal Frink led a team on the design of the vortex fap for the F-106B. Using his own design 

process, Frink arrived at the specifc design to be fight tested on the airplane. An immediate 

project challenge was working with an existing old airframe design with specifc load carrying 

capabilities. One critical result of the loads situation was that the vortex fap had to have a 

smaller chord than desired. If loads had permitted, a larger fap would have been used, resulting 

in improved performance. Researchers conducted numerous wind-tunnel tests to verify the fap 

design’s efectiveness and obtain loads information prior to fabrication. A major problem for the 

austere project (Roy V. Harris, Jr., Director of Aeronautics, reprogrammed funding to accomplish 

this multiyear efort) was the unavailability of existing wind-tunnel models for the aged F-106 

confguration. Following a nationwide search, Jim Campbell located a 1/20-scale high-speed test 

model of the F-106B that had been retired to the Smithsonian Air and Space Museum. Langley 

engineering support and brought the model out of mothballs, restoring it to testing condition. 

James B. Hallissy, Jarrett K. Hufman, and Frink led the initial testing and analysis of the model 

in Langley’s 7- by 10-Foot Tunnel. Unfortunately, for angles of attack of interest with the vortex 

faps installed, the F-106B model was load limited in the wing leading-edge area and could only 

be tested up to Mach numbers of 0.5 in the atmospheric 7- by 10-Foot Tunnel. To obtain the 

necessary data, Langley researchers would have to conduct testing in a tunnel with reduced 

pressure and lower loads. Te Langley 8-Foot Transonic Pressure Tunnel, with its capability to 

run at reduced pressures, would have been the obvious choice for this work, but was not available 

as it was heavily committed to Langley laminar-fow tests (discussed in a previous section). Te 

Langley 16-Foot TDT was the only other transonic tunnel at Langley with the capability to test 

at stagnation pressures below atmosphere. Hallissy, Charles H. Fox, Michael H. Durham, and W. 

F. (Bill) Cazier took on a major challenge in this endeavor because the TDT was not set up for 

performance testing. Te researchers confrmed that a signifcant performance increment could be 

achieved transonically, although the optimum fap defections were diferent and the magnitude 

of the increment was somewhat reduced relative to the subsonic conditions. Hallissy further 

extended the data by conducting additional tests in the Ames Research Center 6- by 6-Foot 

Supersonic Tunnel. 

While high-speed tunnel testing assessed transonic performance of the F-106B vortex-fap 

confguration, a team led by Long P. Yip conducted low-speed tests of a full-scale airframe in the 

Langley Full-Scale Tunnel. Because a full-scale F-106B could not be accommodated within the 

Innovation in Flight 257 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

Neal Frink inspects full-scale semispan model of F-106 equipped with his vortex-fap design. 

tunnel’s 30- by 60-ft test section dimensions, Yip and his team acquired a second, nonfightworthy 

F-106B aircraft and proceeded to physically slice the airplane down its centerline to create a 

semispan, full-scale F-106B test article. Referred to as the F-53 (half an F-106!), the semispan 

article was tested for fap loads and stability efects in 1985. Results of the tests indicated an 

apparent vortex-fow instability on the fap’s inner portion near the fuselage intersection. In view 

of these results and additional guidance from CFD computations, the team increased the inner 

fap’s local chord length. 

Te F-106B fap system’s structural design was led by Joseph D. Pride, Garland O. Goodwin 

(Kentron Technologies, Inc.), and a team of in-house engineering personnel. Te system consisted 

of a simplifed ground-adjustable “bolt-on” fap that could be installed at diferent fxed defection 

angles from 20 to 50 degrees. Te fap was designed and constructed in spanwise segments to 

comply with structural loading and defection issues. Te actual fabrication included access straps 

that bridged leading-edge access areas between major segments located ahead of the wing spar. 

Langley’s fabrication shops constructed the vortex-fap components. 

258 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

Free-fight model of the F-106B modifed with a vortex fap (left) and in fight 

in the Langley Full-Scale Tunnel (right). 

Prior to fight test planning, no information on potential efects of a vortex fap on stability, 

control, and fying qualities of the F-106B was available. To assess this issue and to prepare pilots 

for the fight tests, Langley staf conducted a series of static and dynamic stability assessments and a 

piloted simulator study. Long P. Yip led dynamic stability testing in the Langley Full-Scale Tunnel, 

which included dynamic model force tests to obtain aerodynamic data for analysis of dynamic 

stability and for inputs to piloted simulators. Yip also led free-fight tests of the 15-percent scale 

model to assess the impact of vortex faps on stability and control characteristics. One of the major 

concerns prior to these free-fight model tests was whether the leading-edge vortices on the vortex 

faps would lift of the surface abruptly or discontinuously, causing undesirable aircraft responses. 

Assisted by Sue B. Grafton and Jay Brandon, Yip obtained free-fight model results demonstrating 

that vortex faps did not signifcantly afect the damping characteristics of the confguration; and, 

with the exception of an acceptable reduction in longitudinal stability, the faps did not degrade 

fying qualities. 

Jay Brandon led a Langley team in gathering the necessary aerodynamic data for the development 

of a piloted simulator of the modifed F-106B for pilot assessment and training using the Langley 

Diferential Maneuvering Simulator (DMS). Langley research pilot Philip W. Brown was selected 

to be the primary evaluation pilot for the fight test program as he had accumulated signifcant 

fight time in the basic F-106B in previous Langley fight programs. Brown conducted several 

simulator assessments and concluded that the F-106B vortex-fap confguration would be expected 

to have satisfactory fying characteristics. 

Project Manager for the F-106B fight-test program was Ronald H. Smith, who was assisted by 

James B. Hallissy. In addition to his managerial responsibilities, Hallissy was Principal Investigator 

Innovation in Flight 259 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

for determining the fow-feld characteristics and performance increments achieved with faps on 

the airplane. Together with W. Elliott Schoonover, Hallissy contributed extensive eforts to prepare 

the airplane for performance measurements and postfight data analysis. Te tasks were particularly 

challenging because the airplane lacked conventional instrumentation for performance tests (such 

as a calibrated engine) and pressures had to be obtained by upper-surface belts rather than pressure 

ports. Jay Brandon and Tomas D. Johnson (PRC-Kentron, Inc.) accompanied project pilot Phil 

Brown on fow-visualization fight tests. 

A most informative aspect of the F-106B vortex-fap fight test program was the unique vaporscreen fow-visualization technique used to visualize details of the leading-edge vortex structure 

during actual fight tests. Te visualization concept, which John E. Lamar conceived, involved a 

fight adaptation of an existing vapor-screen method for fow visualization commonly used in wind 

tunnels. During aircraft fight maneuvers, high relative humidity and low pressures in the fow 

around an aircraft will sometimes cause moisture to condense, providing a natural visualization 

of aerodynamic fow patterns. Te Langley vapor-screen technique obviated the need for natural 

humidity by seeding the air stream with a heated propylene glycol vapor pumped from a missilebay pallet and expelled through a probe placed under the left wing panel’s leading edge. When 

exposed to cold temperatures, the clear glycol vapor became white, allowing for visualization of 

the fow feld. In the frst fight experiments, conducted in 1985 before the aircraft was modifed, 

the vapor entrained by the vortices was illuminated by a thin light sheet that was projected across 

the wing in a fxed plane by a mercury-arc lamp behind a narrow slit in an apparatus mounted on 

the fuselage’s side. Onboard video cameras were used to record fow patterns of the vortical fow 

within the fxed light sheet on the wing upper surface. Te unmodifed wing’s fow-visualization 

fights began in February 1985 and were conducted on moonless nights to provide contrast and 

optimize the images produced. Joseph D. Pride and Tom Johnson were key members of Lamar’s 

fow visualization team, which obtained detailed fow information from Mach 0.4 to Mach 0.9 

during maneuvers for the basic F-106B. 

Initial results from the visualization experiments showed the complicated fow feld on the wing 

upper surface. Single leading-edge vortices were observed on each F-106B wing panel at angles 

of attack above about 20 degrees as expected, but at lower angles of attack, between 17 and 20 

degrees, multiple leading-edge vortices appeared along the wingspan. Tis unexpected phenomenon 

warranted additional visualization studies (to be discussed later), which were conducted after the 

vortex-fap performance testing was completed. 

In 1987, after nearly 3,000 hours of wind-tunnel model testing and computational studies, the 

Langley research team evaluated the vortex-fap concept in fight on the F-106B. Flight tests of the 

260 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

unmodifed airplane were frst conducted to establish a baseline for performance measurements, 

then the production wing leading edges were removed and the ground-adjustable vortex faps 

installed. Te right wing panel was instrumented to measure surface pressures, and the left 

wing was instrumented with accelerometers and strain gauges to monitor structural loads and 

deformation. Te team made the frst fight with the vortex fap on August 2, 1988, and continued 

testing for 93 research fights over the next 2-plus years. Te fight program’s primary objectives 

were to document detailed aerodynamic fow characteristics and compare them with wind-tunnel 

and computational predictions, and to assess the vortex fap’s impact on aircraft performance 

and handling qualities, including takeofs, landings, and transonic maneuvers. Te research team 

designed the extensive pressure measurements and fow visualization tests to provide a database 

for design and analysis tool calibration for vortex-fap technology as well as generic experimental, 

computational, and fight test technology. Flights were conducted for vortex-fap angles of 30 

and 40 degrees for Mach numbers from 0.3 to 0.9 and for altitudes up to 40,000 ft. Results 

were obtained in the form of incremental performance measurements from the basic F-106B, and 

parameter identifcation techniques were used to extract aircraft stability and control information. 

Tom Johnson and Jay Brandon few as fight test engineers for all the performance fights and in 

the chase airplane for photos and coordination. 

Te NASA F-106B in fight with the vortex-fap modifcation. 

Innovation in Flight 261 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

Te vortex fap’s aerodynamic performance benefts as determined in the F-106B fight tests were 

extremely impressive. Improvements in the aircraft L/D resulted in very signifcant increases in 

sustained turn capability during maneuvers through the highest Mach number fown (0.9). For 

example, the airplane’s achievable sustained g was increased by about 28 percent at a Mach number 

of 0.7. Te quantitative performance results obtained in the fight program provided invaluable 

documentation and demonstration of the vortex-fap’s potential benefts for highly swept military 

fghter aircraft. Te calibration of analytical design methods and fow visualization data with fight 

data revealed complex fow felds that continued to challenge the capabilities of wind tunnels and 

computational fuid dynamics. 

As previously discussed, initial F-106B in-fight fow-visualization results had indicated unexpected 

fow phenomena and multiple vortices. Terefore, the Langley researchers conducted a second 

series of fow visualization experiments beginning in 1990 to provide further information on the 

structure of multiple vortical fows for baseline and vortex-fap aircraft confgurations. John Lamar 

and the engineering support staf conceived a refned fow-visualization system for these followup tests, providing much more research fexibility and integrated data over a larger viewing area 

by using a scanning light sheet source that was mounted in a streamline fairing atop the fuselage 

spine. Jay Brandon led the eforts for implementing the new visualization system on the aircraft. 

Te fow visualization system included two video cameras (one located on the engine intake and 

one near the aircraft centerline aft of the canopy). Using this approach, researchers obtained fow 

information over a broad sector on and over the left wing during fight. In addition to the vapor 

screen information, they obtained on-surface results using oil fows and tufts on the wing upper 

surface. Brandon and Lamar served as co-investigators of the fight data. 

Te team obtained fow visualization results for vortex-fap settings of 30 and 40 degrees over a 

Mach number range of 0.3 to 0.9 in 1990. Once again, the researchers observed unexpected results 

for vortical fows. As had occurred previously for the basic wing, the vortex fap exhibited multiple 

vortices (on the fap surface), although this diference of the fow physics from that expected did 

not seem to result in degradation in predicted performance improvements. 

Te multiple vortices appeared to originate on the vortex fap and then migrate of the fap to run 

nearly streamwise over the wing as another vortex originated on the fap. Tis pattern was repeated 

many times down the wing depending on angle of attack. Oil-fow results confrmed existence of a 

highly complex fow pattern with multiple vortex systems as observed during the vapor-screen tests. 

Examinations of the research team’s fight results showed that the multiple streamwise vortices 

observed above the wing originated at the fap leading edge where individual fap segments were 

joined. Te team also conducted oil-fow studies with the joints sealed with fabric-backed tape to 

262 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

Te scanning vapor screen technique. 

F-106B researchers prepare for a night mission. 

Innovation in Flight 263 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

prevent air leakage and observed essentially the same results. Te oil-fow studies indicated that 

the small geometric perturbations along the leading edge were sufcient to generate a leading-edge 

fow that was very complex and signifcantly diferent in details than that observed previously in 

wind-tunnel model tests and in CFD calculations. 

After observing the unpredicted vortex topologies in fight, Jim Hallissy, Elliot Schoonover, and 

Tom Johnson tested the F-106 wind-tunnel model in the Langley 7- by 10-Foot High-Speed 

Tunnel. All previous wind-tunnel tests had shown a single leading-edge vortex system along the 

fap, as predicted by the design methodology. During storage of the model, some minor damage in 

the form of small dents and nicks had occurred to the faps. Because leading-edge discontinuities 

were believed to be at least partially responsible for the multiple vortices seen in fight, these dents 

were not repaired prior to the tests. During the test the dents, or the subsequent application of tape 

fow trips, provided sufcient perturbations for shedding of vortices and formation of the multiple 

vortex system seen in fight. Te extremely small perturbation size indicated that with normal 

manufacturing tolerances, it might be impossible to avoid the multiple vortex patterns seen in 

fight on a full-scale airplane with leading-edge devices similar to vortex faps. 

In summary, the major purpose for developing the vortex fap was to improve L/D ratio at high 

Surface-oil studies illustrate multiple vortex fows seen on the leading edge. 

264 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

Langley researchers pose with the F-106B Vortex-Flap Research Aircraft in 1988. 

maneuvering lift coefcients. Despite the strikingly diferent fow feld details developed on the 

airplane compared with computational theory and wind-tunnel predictions, the faps’ overall 

efectiveness was very close to predictions, resulting in signifcant improvements in maneuver 

capability, such as sustained-turn characteristics. 

Following the completion of vortex-fap fights, the NASA F-106B airplane was retired on May 17, 

1991, in a formal ceremony at Langley. Later that year, the airplane was transferred to the Virginia 

Air and Space Center in Hampton, where it has been displayed to the public with the vortex-fap 

modifcation. 

F-16XL Plans 

Leadership of the High-Speed Research Program’s integrated, NASA-wide high lift element 

was assigned to NASA Langley with Joseph R. Chambers, Chief of the Flight Applications 

Division, selected to lead the efort. A challenging problem facing a future supersonic transport is 

Innovation in Flight 265 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

unacceptable takeof noise caused by the high levels of thrust required to overcome inherently low 

lift and high drag of highly swept supersonic wings and poor subsonic cruise performance caused 

by the high induced drag of such wing shapes. Accordingly, wind-tunnel and computational 

eforts were undertaken to improve the subsonic L/D aerodynamic characteristics of candidate 

HSR confgurations. Te scope of research at Langley and the Ames Research Center included 

studies of various types of leading-edge designs, including fxed cambered confgurations and 

defectable cambered faps and vortex faps. 

In 1993, Chambers advocated for fight testing of an appropriate airplane to obtain more detailed 

information on the impact of leading-edge devices, such as the vortex fap, for subsonic and highlift conditions. NASA transferred one of its two F-16XL research aircraft from the NASA Dryden 

Flight Research Center to Langley for the proposed program. As previously discussed, Langley 

had conducted F-16XL low-speed and transonic vortex-fap tunnel tests during the early 1980s 

in concert with the aircraft’s development. As the HSR Program interests in low-speed high-lift 

devices intensifed, researcher David E. Hahne led wind-tunnel tests of an F-16XL model with 

several leading-edge fap confgurations to begin the process of selecting candidate faps to be 

fown on the airplane. In addition to aerodynamic studies, the research program was to include 

F-16XL aircraft painted by Langley for fow visualization tests. 

266 Innovation in Flight 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

unconventional thrust management strategies to reduce power at certain takeof conditions to 

further reduce noise. Noise level measurements would be made for the airplane with the fap 

modifcations and throttle strategies. A piloted simulation of the F-16XL was implemented by 

Langley researchers in the Langley DMS in preparation for fight testing. 

Te F-16XL’s upper surfaces were painted black to enhance the fow visualization studies planned 

for the fight tests. Unfortunately, changes in program priorities terminated the F-16XL fight 

efort within HSR before modifcations for vortex-fap fight activities could begin. NASA did, 

however, support a series of basic aerodynamic vortex-fow studies on the F-16XL airplane led by 

John E. Lamar in a project known as the Cranked-Arrow Wing Aerodynamics Project (CAWAP). 

Lamar’s team included Langley’s Cliford J. Obara, Susan J. Rickard, and Bruce D. Fisher, as 

well as Dryden’s David F. Fisher. Te team focused on detailed measurements and analysis of 

the aircraft’s exhibited vortical-fow characteristics, including wing pressures, boundary-layer 

measurements, and fow visualization on the upper wing surface using tufts. Te results were 

correlated with computational results, providing a database for additional analyses and adding to 

Langley’s contributions in vortical-fow technology. 

Status and Outlook 

To date, NASA, industry, and academia have accomplished much in the development of aerodynamic 

theories and exploratory aerodynamic applications of vortex-fap concepts. Enhanced aerodynamic 

performance has been measured for a wide range of slender-wing confgurations, including fullscale fight tests. However, the technology maturation level for potential production applications 

has remained below the level required for low-risk implementation by industry. 

Many barriers and challenges cited in the earlier discussion of this topic will need solving before 

applications can be expected. Te ultimate demonstration of an “adaptive” vortex-fap design 

(defections automatically controlled for maximum efciency by fight computer) on a high-speed 

aircraft with production-type fabrication and tooling will be necessary before the concept can 

applied. Also, the systems-level impacts of the vortex fap (weight, maintenance, failure modes, 

etc.) must be assessed and compared with more conventional approaches currently used such as 

conical wing camber, or conventional leading-edge faps. 

Unfortunately, recent high-performance military confgurations have used lower wing-sweep 

angles than those appropriate for the slender-wing vortex-fap applications. As a result, designers 

have chosen the use of conical camber, conventional leading-edge maneuver faps and hybridwing (wing-body strake and relatively unswept outer wing) design options. Further, the dramatic 

Innovation in Flight 267 
THE VORTEX FLAP: EFFICIENCY AND VERSATILITY 

reduction in new military aircraft programs has left few opportunities for injection of this 

technology. On the other hand, recent interest in uninhabited combat air vehicles that use delta 

and highly swept wing planforms might permit a renewed interest in the concept. Such concepts 

would be of even greater interest if the application of “smart” materials could permit the use of 

continuous outer mold lines, thereby resolving issues regarding the impact of vortex-fap physical 

discontinuities on stealth and radar observables. 

From a civil aircraft perspective, the demise of the NASA HSR Program and a pessimistic 

international outlook for large supersonic transports in the future does not portend of opportunities 

for vortex-fap applications to that class of vehicle. However, growing interest in economically viable 

supersonic business jets could conceivably rekindle interest in vortex-fap technology, especially 

if the concept could help designers attack the known operational barriers of environmental 

noise issues. 

Finally, it is appropriate to note that Langley’s success in developing and demonstrating the 

benefts of vortex-fow control with the leading-edge vortex fap for performance inspired NASA 

and industry to focus on solutions to stability and control problems of contemporary fghter 

confgurations caused by uncontrolled vortex fows at high angles of attack. Examples of followup research included the control of vortical fows shed by pointed slender forebodies, noncircular 

forebody cross sections, and nose strakes. In proof-of-concept experiments, most of these stability 

and control problems were demonstrated to be amenable to improvement by the use of innovative 

mechanical and pneumatic (blowing and suction) techniques for vortex management. 

268 Innovation in Flight 
Innovative Control Effectors: Smart Muscles 

Concept and Benefts 

Te challenge of providing satisfactory controllability and handling qualities for aircraft has been 

a crucial requirement throughout the history of aviation. Attempts to provide adequate levels of 

control have resulted in a wide variety of conventional control efectors, including empennagemounted elevators and rudders; wing-mounted ailerons, elevons, rudders, and spoilers; fuselagemounted canards; wing warping; mechanical engine thrust vectoring in pitch and yaw; and 

diferential engine thrust for multiengine confgurations. Te overriding requirement that aircraft 

must exhibit satisfactory responses to control inputs for all phases of operational envelope, including 

of-design conditions, has driven the development of these various concepts. 

Evolving requirements for fight mission capabilities and unconventional confgurations have forced 

the technology “push” and the applications “pull” for advanced control efectors. For example, 

during the early days of heavier-than-air fight, designers attempted to meet the fundamental 

need to provide aircraft that could be successfully fown by a human pilot through relatively 

mundane maneuvers and very limited fight envelopes. As aircraft mission capabilities rapidly 

expanded to faster speeds and higher altitudes, new challenges—such as compressibility efects, 

structural fexibility, futter, excessive hinge moments, pilot stick forces, pilot-induced oscillations, 

and control reversal—were encountered and researched. Tese eforts produced solutions that 

enabled the improved capabilities ofered by unconventional confgurations. Some unconventional 

confgurations, such as fying wings, required innovative controls (e.g., wing tip-mounted split 

ailerons) that serve as ailerons and rudders. 

Military aircraft, in particular, have been the recipients of extensive research on fight controls 

because of stringent maneuverability requirements and challenging of-design operations. During 

World War II, for example, NACA, the military services, and industry devoted continuous eforts 

to reducing stick forces and enhancing roll performance, thereby ensuring that the razor-thin 

combat advantage in close-in dogfghts would belong to U.S. pilots. Following World War II, the 

advent of supersonic fight with its attendant compressibility efects resulted in the emergence of 

new control concepts: powered control systems, diferentially defectable stabilators for pitch and 

roll control at high speeds, and the use of spoilers for roll control. 

In recent years, the ongoing changes in aircraft mission capabilities have continued to invigorate 

studies of new control efectors. For civil aircraft, commercial transport designers have directed 

their attentions to ensuring adequate controllability during high-subsonic cruise conditions where 

shock-induced separation may cause steady or unsteady aerodynamic phenomena that degrade 

control efectiveness. In addition, designers strive for efcient outer-wing aileron confgurations 

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(or middle-wing spoilers) that “free up” valuable inner-wing trailing-edge locations for high-lift 

fap devices. More efcient faps permit the designer to reduce the wing’s size, thereby reducing 

weight and improving overall mission capability. Finally, propulsive control for multiengine civil 

transport confgurations received recent attention after the heroic fight crew eforts of the 1989 

DC-10 crash at Sioux City, Iowa, following hydraulic power loss caused by an engine structural 

failure. NASA’s Dryden Flight Research Center has conducted extensive research on the propulsive 

control technique. 

For military aircraft, an aircraft’s full use for strenuous maneuvers and other requirements 

demands control efector research on barrier problems. For example, providing satisfactory levels of 

control efectiveness and coordination at high-angle-of-attack fight conditions in the presence of 

extensive fow separation has promoted interest in thrust vectoring, vortex-fow control, and using 

forebody strakes for lateral-directional control. Automatic departure and spin prevention have been 

developed and applied using advanced control system architectures. Another controls challenge 

has arisen from the application of stealth technology for low-observable confgurations. Stealth 

confgurations require special consideration, or elimination, of control surface geometries such as 

gaps, hinges, and other details that can degrade radar or infrared signature characteristics. 

Recent disciplinary advances in structures and materials have led to a new family of “smart” 

materials that respond to stimuli with shape changes that could be integrated into innovative 

control efectors. “Morphing” confgurations, which adjust external shape as a function of 

fight conditions, vehicle health considerations, or other factors, would use such an approach to 

provide control. 

Innovative control efectors can be used with advanced adaptive control system architectures that 

sense the changes in fight environment and automatically schedule the control gains, feedback, 

and mixing to promote more optimal response characteristics as well as improved aerodynamic 

efciency. Te sketch illustrates some of the innovative control efector research topics conducted 

by NASA. 

Vortex-fow control efectors modify and control the powerful vortical fows generated by highly 

swept wings, wing-fuselage strakes (also called leading-edge extensions), and fuselage forebodies to 

provide control at high angle-of-attack conditions. At relatively high angles of attack, such devices 

provide signifcantly larger control efectiveness than conventional wing or tail-mounted controls, 

which are usually inefective for highly separated fow conditions. 

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Innovative control efector concepts studied by NASA-Langley. 

Langley has led international research on the application of passive porosity—the use of perforated 

regions on aircraft surfaces to control aerodynamic pressures and fow characteristics—to modify 

aerodynamic phenomena such as shock locations, separation, and lift for enhanced performance, 

stability, and control. Tis approach permits relatively large variations in aerodynamic behavior 

without constraints, such as hinge moments, normally encountered with conventional aerodynamic 

control surfaces. 

Spanwise blowing concepts use compressed air derived from engine bleed or other sources to 

modify airfow over lifting surfaces. By modifying and creating vortical-type fows as a result of 

steady or pulsed blowing in a spanwise direction, airfow over the upper surface may be signifcantly 

infuenced, to the extent that vortex lift and reattachment of separated fows can be efected. Tus, 

aerodynamic performance as well as stability and control can be enhanced, particularly for high 

angle-of-attack conditions. 

Due to extensive research by NASA, industry, and DoD, various types of mechanical thrust 

vectoring concepts have now been implemented in current military aircraft for enhanced 

maneuverability and control. A concept previously applied to rockets and missiles, known as fuidic 

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thrust vectoring, uses fuidic rather than mechanical means to redirect engine thrust for vectoring, 

and ofers several advantages over mechanical vectoring. Fluidic thrust vectoring concepts ofer 

the advantages of reduced weight and maintenance associated with mechanical vectoring devices, 

as well as eliminating engine nozzle defections and geometric changes that compromise aircraft 

signature characteristics and provide opposing pilots visual cues that can be used to anticipate 

evasive maneuvers during close-in air combat. 

Challenges and Barriers 

Te foregoing innovative control efector concepts have received considerable research attention 

within the aerodynamic community, particularly for applications to highly maneuverable military 

aircraft. Revolutionary capabilities for maneuver enhancement and aircraft controllability are 

apparent; however, these concepts have not yet been applied to current aircraft due to risks 

associated with disciplinary and operational challenges. Te following discussion identifes some 

issues that have arisen during NASA research on the concepts, most of which past Langley eforts 

have addressed and resolved. 

Disciplinary Challenges 

Many control concepts face signifcant challenges in the areas of aerodynamics and structural 

weight, as well as aeroelasticity and futter. For example, the aerodynamic efectiveness of the 

control concepts must be maintained across the fight envelope. For high-performance aircraft, this 

requirement is especially daunting because of compressibility efects, shock-induced separation, 

and unsteady fow phenomena. Fundamental efector characteristics must be established through 

extensive wind-tunnel and fight aerodynamic research eforts. Te rapid maturation of advanced 

CFD methods is now contributing to the assessment and solution of problems involving the efects 

of Mach number and other fight variables on control efectors. 

Tese concepts must be designed to eliminate undesirable aeroelastic characteristics, such as futter 

or aeroelastically induced control reversals, along with maintaining adequate control efectiveness. 

Evaluations of these phenomena are normally conducted in unique wind tunnels, including the 

Langley 16-Foot TDT, or in carefully controlled fight experiments. 

Te magnitude and character of control moments produced by innovative control efectors must 

also provide satisfactory control response characteristics. In particular, the aerodynamic moments 

produced by control actuation must vary in a linear fashion with the pilot’s control inputs for 

satisfactory aircraft response, and unsatisfactory by-products known as “cross-axis” moments (for 

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INNOVATIVE CONTROL EFFECTORS: SMART MUSCLES 

example, yawing moments produced by a roll control) must be minimized. Additional constraints, 

such as excessive control hinge moments, must be avoided and the weight of control mechanisms 

and actuation devices must be acceptable. 

Operational Challenges 

Signifcant challenges to the applications of innovative control efectors also exist relative 

to operational and environmental issues. Paramount to all operational issues is the cost of 

implementation, maintenance, and replacement of control systems. Tese cost considerations 

primarily involve associated control system software requirements and other requirements, such as 

certifcation time and cost. 

Operational challenges to advanced controls include a myriad of issues dominated by maintenance 

requirements, health monitoring, and failure modes. In-depth analysis of each factor is mandatory 

before the ultimate feasibility of advanced concepts can be established. In addition, environmental 

efects (e.g., icing and corrosion) must be assessed and resolved. 

Special constraints are placed on innovative control efectors that use auxiliary air for fow control 

mechanisms. Weight and engine performance issues severely restrict the potential benefts if, for 

example, excessive engine bleed requirements are necessary. 

Arguably, the most important operational challenge to new control efectors is the opinion of 

evaluation pilots relative to the crispness, predictability, and efectiveness of advanced control 

efectors on aircraft response characteristics. If signifcant nonlinearities, cross-axis interactions, 

and degraded efectiveness occur during critical phases of fight, the control system will be rejected 

for application. 

Langley Activities 

Langley Research Center has historically led the research community in advanced fight control 

systems development. In addition to extensive in-house aerodynamic studies coupled with control 

system architecture and failure analysis methodology, the Center has partnered with other NASA 

Centers, industry, and DoD in advancing the state of the art in fight controls. Coupled with 

legendary contributions in developing conventional aileron, elevator/stabilator, and spoiler control 

efectors, Langley researchers have pursued many innovative concepts yet to be applied. Te 

following discussions briefy describe some of these pioneering eforts. 

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Spanwise Blowing 

In the middle 1970s, an intense national interest arose in highly maneuverable military aircraft 

capable of fight at extreme angles of attack with controllable “care-free” characteristics. Associated 

with this activity was a mainstream of attention on vortical fows and the use of vortical fow 

control for enhanced lift and performance. As discussed in Partners in Freedom, Langley Research 

Center contributed directly to vortex technology in activities ranging from fundamental research to 

specifc aircraft applications, including uses on the F-16 and F/A-18 aircraft. Edward C. Polhamus 

led a wide variety of vortex-control investigations conducted within the basic NASA research 

program, with industry and DoD partners, and with universities. 

Within this environment of innovation and opportunity, Polhamus’ group directed its eforts 

toward the potential use of several concepts to enhance the powerful aerodynamic efects of vortical 

fows for high-performance confgurations. One concept was the use of a high-pressure jet blowing 

spanwise over a wing upper surface in a direction parallel to the leading edge to augment vortex 

lift and enhance favorable fow phenomena over the wing. Preliminary experiments indicated 

that spanwise blowing would aid in the formation and control of the leading-edge vortex shed 

by moderately swept wings. Polhamus assigned the lead role for spanwise blowing research in 

his group to James F. Campbell, who was assisted by researchers Gary E. Erickson, Jarrett K. 

Hufman, and Tomas D. Johnson, Jr. 

Campbell and his associates accomplished exploratory spanwise blowing studies in 1974 during 

tests of simple wings with leading-edge sweep angles of 30 and 45 degrees in the Langley High 

Speed 7- by 10-Foot Tunnel. Tese early tests indicated that spanwise blowing signifcantly 

improved the aerodynamic characteristics of both wing models at high angles of attack. Tese 

tests also revealed that spanwise blowing generated large increases in lift at high angles of attack, 

improved the drag polars, and extended linear pitching moments to high lift conditions. Te study 

also unveiled an important aspect of the spanwise blowing mechanism: full vortex suction lift was 

achieved at the inboard span station with a relatively small blowing rate, but higher blowing rates 

would be necessary to attain the full vortex-lift level at increased span distances. 

Campbell and Erickson followed this exploratory study with additional wind-tunnel studies of 

increased sophistication and scope. Tey teamed for a study in 1977 involving tests of a 44-degree 

swept trapezoidal wing model for a range of angle of attack, jet momentum coefcients, and 

leading and trailing-edge fap defection angles. Tey found blowing to be more efective at higher 

Mach numbers (0.5). Te researchers found that spanwise blowing in conjunction with a defected 

trailing-edge fap resulted in lift and drag benefts that exceeded the summation of the efects of 

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Blowing of; vortex breakdown. Blowing on; vortex breakdown delayed. 

Flow visualization of spanwise blowing on a swept trapezoidal wing for an angle of attack 

of 30 degrees. 

each high-lift device acting alone. Of relevance to the current discussion, they found asymmetric 

blowing to be an efective lateral control device at the higher angles of attack. 

While Campbell and Erickson were pursuing their fundamental aerodynamic studies of the impact 

of geometric and pneumatic variables on the efectiveness of spanwise blowing, a group under 

Joseph R. Chambers and Joseph L. Johnson, Jr., at the Langley 30- by 60-Foot (Full Scale) Tunnel 

began research on the efects of spanwise blowing on the dynamic fight behavior of dynamically 

scaled free-fight models. Using the remotely controlled free-fight test technique described in other 

sections of this document, this group assessed the impact of spanwise blowing on longitudinal and 

lateral-directional behavior for generic and specifc aircraft confgurations. 

In 1978, Dale R. Satran and Ernie L. Anglin led free-fight tests of a general research fghter 

confguration (based on a modifed F-5 confguration) to evaluate spanwise blowing efects of two 

diferent wing planforms. One confguration incorporated the wing of the baseline F-5 design 

(34-degree leading-edge sweep) and the second confguration used a 60-degree delta wing. Tree 

blowing ports were located on each side of the fuselage, oriented parallel to each wing panel’s leading 

edge. Emphasis was on determining dynamic lateral-directional characteristics, particularly in the 

stall and departure angle-of-attack range; however, efects of spanwise blowing on longitudinal 

aerodynamics were also determined. Te tunnel tests included measurement of conventional static 

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force and moment data, dynamic (forced-oscillation) aerodynamic data, visualization of airfow 

changes created by spanwise blowing, and free-fight model tests. Te efects of blowing rate, 

chordwise location of the blowing ports, and asymmetric blowing on the conventional aerodynamic 

control characteristics were investigated. 

In the angle-of-attack regions wherein spanwise blowing substantially improved the wing 

upper surface fow feld (i.e., provided reattachment of the fow aft of the leading-edge vortex), 

improvements in both static and dynamic lateral-directional stability and control were observed. 

Rolling moment substantially increased at high angles of attack when asymmetric blowing was 

used for roll control. In fact, the magnitude of rolling moment was as large as that provided by the 

ailerons at low angles of attack. However, the results also showed that unacceptable large adverse 

yawing moments were associated with asymmetric blowing, to the extent that full defection 

of the rudder would be required to trim out the undesirable yawing moments and coordinate 

the roll maneuver. 

National interest in spanwise blowing continued to expand in the late 1980s. Industry and DoD 

eforts began to focus on fight testing of specifc full-scale aircraft to extend the limited aerodynamic 

database available in wind tunnels to full-scale hardware. Tese eforts also provided detailed 

engineering information on blowing requirements, engine bleed and ducting characteristics, and 

other system-level features required to design and determine the concept’s feasibility. In a 1984 

study, McDonnell Douglas modifed an F-4C Phantom II airplane under Air Force sponsorship 

to investigate spanwise blowing. Te goal was to validate wind-tunnel data indicating that the 

F-4C’s existing chordwise BLC system could be replaced with a more maintenance-free spanwise 

blowing system without degrading performance. Te designers piped high-pressure bleed air from 

the F-4C’s J-79 engine compressors forward along the inside of the fuselage and expelled the fow 

through a nozzle in the fuselage near the wing’s leading edge and just above the surface. Te fighttest results showed that the approach speed could be reduced by about 7 kts and maneuverability 

was noticeably improved. Because the confguration’s leading-edge jet did not penetrate to the 

outer wing panel, it was suggested that further improvements would occur if some of the blowing 

were distributed over the outer wing panel of the F-4C. 

Langley’s Jim Campbell and Dryden’s Teodore (Ted) Ayers advocated for a follow-up NASA 

fight test of the F-4C at Dryden, which was supported by the Air Force. At Langley, Jarrett 

K. Hufman, David E. Hahne, and Tomas D. Johnson, Jr., led tests in the Langley 7- by 10-

Foot High-Speed Tunnel and the Langley 30- by 60-Foot (Full-Scale) Tunnel to determine the 

optimum location and orientation of the outer panel blowing ports and the efect of blowing on 

lateral-directional characteristics. Hufman used a 0.10-scale F-4C model for his studies in the 7-

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Langley researcher David E. Hahne poses with F-4 free-fight model, shown in fight at high angles of attack in the 

Langley Full-Scale Tunnel. 

by 10-foot tunnel, and Hahne used a 0.13-scale dynamically scaled free-fight model for fight and 

force tests in the 30- by 60-Foot Tunnel. Limitations in NASA resources prevented the planned 

fight tests at Dryden even though the static and free-fight test results were promising. 

Langley and national interest in spanwise blowing waned following these 1980s studies and 

research on the concept’s use in an asymmetric manner for roll control was terminated. Currently, 

it appears that the use of spanwise blowing for roll control still faces many fundamental issues, 

especially the level of engine bleed air required and the large adverse yawing moments produced by 

spanwise blowing for roll control. 

Fluidic Trust Vectoring 

Maintaining air supremacy for the United States requires stealthy, supermaneuverable aircraft. 

Decades of national research on mechanical engine thrust vectoring techniques initiated in the 

1970s were designed to meet the demand for fghter aircraft with increased agility. Tis research 

and development culminated in the application of thrust vectoring to the Air Force’s F-22 design. 

In the 1990s, additional requirements for low-observable aircraft and for lower exhaust system 

weights were the catalysts for research on the use of fuidic concepts for thrust vectoring. Langley 

has been a leader in the evolving technology for fuidic vectoring due to extensive in-house and 

cooperative research with industry, DoD, and academia. Researcher Karen A. Deere has contributed 

an excellent summary of Langley contributions in this area, and the reader is referred to her 

publication for detailed information (see bibliography). 

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Te concept of fuidic vectoring uses fuid control mechanisms to redirect the engine exhaust with 

no mechanical nozzle parts such as those used for mechanical nozzle vectoring concepts. Typically, 

the fuidic vectoring concepts use secondary air sources to create an of-axis defection of the jet 

thrust. In the early 1990s, the staf of the Langley 16-Foot Transonic Tunnel, under the direction 

of Bobby Berrier, initiated a cooperative fuidic thrust vectoring program with the Air Force called 

Fluidic Injection Nozzle Technology (FLINT). David J. Wing led the NASA efort for the program. 

Te results of the FLINT Program predicted that the potential benefts of fuidic thrust vectoring 

nozzles would be a 28- to 40-percent weight reduction by implementing fuidic throat area control, 

a 43- to 80-percent weight reduction by implementing fuidic throat area and exit area control, a 7-

to 12-percent improvement in engine thrust-to-weight ratio, and a 37- to 53-percent reduction in 

nozzle procurement and life cycle costs. In addition to these considerations, fxed aperture nozzles 

would enhance low-observable characteristics by eliminating moving faps, discontinuities, and 

gaps. Fluidic systems without moving external nozzle parts would also eliminate visual cues of 

vectoring control inputs that might be used by enemy pilots to anticipate an impending maneuver 

during close-in air combat. 

Te shock-vector-control concept for fuidic thrust vectoring. 

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Te throat-shifting concept for fuidic thrust vectoring. 

Te counterfow concept for fuidic thrust vectoring. 

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Langley fuidic thrust vectoring concept studies are divided into three categories according to the 

method used for fuidic thrust vectoring: the shock-vector-control method, the throat-shifting 

method, and the counterfow method. 

In the shock-vector-control method, an asymmetric injection of secondary air into the engine 

nozzle’s supersonic primary fow of the divergent section is used to redirect the thrust angle. When 

the secondary air is injected into the primary fow, an oblique shock is created because the primary 

supersonic fow in the nozzle senses the secondary airfow as an obstruction. Te primary fow 

is then directed through the oblique shock, producing large thrust vector angles. Unfortunately, 

thrust performance losses are typically high for this concept. 

In the throat-shifting method of fuidic vectoring, the engine nozzle’s efective throat is 

asymmetrically shifted by asymmetric injection of secondary fow. In the nonvectoring condition, 

the throat of the nozzle occurs at the nozzle’s geometric minimum area. For thrust vectoring, 

the injection of secondary air creates a new skewed minimum area, which shifts the efective 

minimum area and creates an asymmetric pressure loading on the nozzle surfaces, resulting in a 

thrust defection of the primary exhaust fow. 

Te counterfow method of fuidic thrust vectoring uses the approach of counterfowing the 

primary and secondary airstreams with the application of suction at a slot between the primary 

nozzle and collar. Mixing occurs in the shear layers between the aft-directed primary fow and 

the forward-directed suction fow, contributing to the establishment of asymmetric pressures that 

result in thrust vectoring. Tis concept is extremely promising for thrust vectoring but faces many 

technical challenges, including requirements for the suction supply source, aerodynamic hysteresis 

efects, and impact on airframe integration. 

David J. Wing, Karen A. Deere, Bobby L. Berrier, Jefery D. Flamm, and Stuart K. Johnson 

led fuidic thrust vectoring research conducted at Langley. Tey investigated promising concepts 

with computational and experimental tools, and supporting system studies were conducted when 

appropriate. Langley’s development of a Navier-Stokes CFD code known as PAB3D played a 

key role in the analysis and design of fuidic vectoring methods. Te research eforts have been 

characterized by intense interactions and collaborative studies with industry, DoD, and academia. 

Te cooperative teams have collaborated on the design and testing of hardware, and Langley 

researchers have typically led experimental testing in the Langley Jet Exit Test Facility (JETF), 

a unique facility devoted to simulating propulsion systems at static (wind-of) conditions. Te 

industry partners have generally led the nozzle’s design, but Langley researchers originated and 

developed the most recent and promising dual throat nozzle designs. 

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Te scope of fuidic vectoring concepts studied at Langley within the three primary types previously 

mentioned is extremely broad. Researchers conceptualized and evaluated variants of the types, 

adding to the basic knowledge and advances in the state of the art for thrust vectoring. Teaming 

has been extensive, including studies of the shock-vector-control concept with Rockwell, Rohr, 

Pratt & Whitney, General Electric, and Boeing. Te throat-shifting concept has been explored 

with Pratt & Whitney and Lockheed Martin, and Langley joined Florida State University and the 

University of Minnesota to study the counterfow method. 

Deere’s summary publication provides results and details of the foregoing activities beyond the 

present publication’s intended scope, and it is highly recommended for the interested reader. Briefy, 

results from Langley investigations of fuidic thrust vectoring concepts indicate that the most 

thrust efcient fuidic thrust vectoring concept is the throat-shifting method, but larger thrustvector angles are obtained with the shock-vector-control method. However, the most recent throatshifting nozzle designs developed by NASA and Lockheed researchers are now providing thrust 

vector angles equivalent to the shock-vector-control method with lower engine bleed requirements. 

Te counterfow fuidic vectoring concept ofers promise, but faces several signifcant technical 

issues. Langley’s pioneering contributions and fuidic thrust vectoring technology are widely 

recognized and the Center is actively participating in and consulting on the continuous research 

on this topic. 

Vortical Flow Control 

As discussed in a previous section on the vortex-fap and spanwise-blowing concepts, as well as in 

Partners in Freedom, Langley has played a key role in fundamental research on vortical fow and its 

application to aircraft for enhanced performance, stability, and control. With the advent of long, 

pointed fuselage shapes and wing-body strakes, researchers identifed vortical-fow mechanisms 

that generated large potential control moments, especially at high angles of attack. Beginning in 

the 1970s, Langley embarked on studies to control the powerful vortices shed by fuselage forebody 

shapes and wing-body strakes. Researchers discovered that they could produce large rolling and 

yawing moments for enhanced maneuverability by diferentially defecting these devices. 

Dhanvada M. Rao and Langley’s Daniel G. Murri were among the frst to explore the feasibility of 

defecting the wing-body strakes of confgurations similar to the F-16 and F/A-18 in a diferential 

manner to produce asymmetric vortex fow felds resulting in rolling moments. Teir exploratory 

wind-tunnel results of this concept indicated very large rolling moments could be produced; 

however, research eforts on the concept were terminated because large adverse yawing moments, 

similar to those encountered for asymmetric spanwise blowing, were also produced. 

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Strong vortical fow emanating from the wing-body strake of the F/A-18 is clearly defned by natural 

condensation in air. 

More productive Langley research on using vortical fow for vehicle control resulted from applications 

to high-performance aircraft for improved yaw control at high angles of attack. A primary control 

defciency that limits the maneuverability of fghter aircraft is loss of rudder efectiveness when the 

vertical tails are submerged in the low-energy wake of the stalled wing at high angles of attack. 

Loss of yaw control at such conditions is especially critical for maneuverability because the primary 

source of rolling motions at extreme angles of attack is yaw control rather than conventional roll 

control. Tis phenomenon is a result of inertial distribution of the airplane’s mass and the vehicle’s 

relative responses to roll and yaw control inputs. 

Researchers noted that naturally occurring, large asymmetric yawing moments developed on 

slender bodies at high angles of attack. Tey were therefore inspired to develop concepts that could 

precisely produce and control these potentially revolutionary levels of yaw control power. Initially, 

Langley staf demonstrated the use of jet blowing from a thin slot near the nose tip and proceeding 

along the typical fghter radar radome to be an efective controller for forebodies having geometric 

features known to promote strong vortex asymmetry efects. However, for forebody shapes not 

naturally prone to pronounced vortex asymmetry, a diferent vortex manipulation concept is 

required to generate an efective yaw control. In addition, the classic concerns over providing 

adequate levels of pneumatic blowing inhibited potential applications of the blowing concept. 

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Langley researchers developed a highly successful yaw control concept based on the use of 

deployable, diferentially defectable fuselage forebody strakes in the early 1980s. In cooperative 

research with the Air Force, Murri and Rao led the development of a pioneering wind-tunnel 

database that documented the fundamental fow physics associated with forebody strake controls 

for a variety of aircraft confgurations. Tis early research indicated that diferentially defected 

forebody strakes could provide revolutionary levels of precision control for close-in air combat. 

Continuing evolution and refnement of the studies addressed potential efects of Reynolds number 

and providing a linear controller for the pilot. 

In the middle 1980s, NASA launched its High-Angle-of-Attack Technology Program (HATP), 

which focused on the advancement of the state of the art for predicting and controlling aerodynamic 

phenomena for enhanced maneuverability at high angles of attack (see Partners in Freedom). 

Using the F/A-18 confguration as a baseline for wind-tunnel experiments, CFD predictions, and 

simulator and fight assessments, the HATP included an element to develop and evaluate the 

promising forebody-strake concept that the previous investigations had matured. Accordingly, a 

research project referred to as the Actuated Nose Strake for Enhanced Rolling (ANSER) fight 

experiment was planned. Dan Murri, Gautam H. Shah, and Daniel J. DiCarlo led the activities 

at Langley. Te scope of activities at Langley required to defne, assess, and optimize the strake 

confguration for the F/A-18 included conventional static wind tunnel force and moment tests across 

a range of Reynolds and Mach numbers, fow-visualization tests, free-fight model assessments of 

strake efectiveness, CFD studies, and piloted simulator studies of maneuverability and handling 

qualities on the Langley DMS. In addition to Murri, Shah, and DiCarlo, many other Langley 

researchers contributed to these eforts: Robert T. Biedron, Gary E. Erickson, Frank L. Jordan, Sue 

B. Grafton, and Keith D. Hofer. 

In conjunction with the ground tests of the HATP, NASA modifed an F/A-18 fghter aircraft as 

its High Angle-of-Attack (Alpha) Research Vehicle (HARV) for a three-phased fight research 

program lasting from April 1987 until September 1996. Te aircraft completed 385 research 

fights and demonstrated stabilized fight at angles of attack between 65 and 70 degrees using 

thrust vectoring vanes, a research fight control system, and the ANSER forebody strakes. Te 

hardware’s implementation on the HARV was a remarkable display of intercenter coordination and 

cooperation between Langley and the NASA Dryden Flight Research Center. Langley engineering 

and shop organizations designed and fabricated the ANSER forebody-strake hardware, and Dryden’s 

staf completed the tasks of aircraft installation, verifcation, software control fnal design and 

development, and fight test evaluations. Flight assessment results were outstanding, demonstrating 

the efectiveness of this revolutionary control efector for advanced military aircraft. 

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Supporting tests for the Actuated Nose Strake for Enhanced Rolling experiment included 

free-fight model studies (top) and tests on a full-scale F/A-18 in the Ames 80-by 120-Foot 

Tunnel (above). 

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Computational results of the efect of forebody strake defection on the F/A-18 forebody. 

Close-up view of the forebody strakes on the F/A-18 High 

Angle-of-Attack Research Vehicle research airplane. 

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In-fight pictures of the High Angle-of-Attack Research Vehicle showing the right strake deployed (left) and smoke-fow 

visualization of the vortex path shed by the strake (right) 

With the extremely favorable results of the HARV fight tests in the HATP, Langley initiated a 

cooperative program known as Strake Technology Research Application to Transport Aircraft 

(STRATA) with Boeing in 1997, the objective being to evaluate forebody-strake technology applied 

to transport aircraft confgurations for enhanced directional stability and control. Because the 

sizing requirement for vertical tail geometry of conventional transport aircraft is usually based on 

critical asymmetric fight conditions, such as engine-thrust loss during takeof or high-crosswind 

landings, alternate concepts that can reduce the size requirements for vertical fn and rudder areas 

(and thereby reduced weight) are of interest. 

Unlike fghter aircraft, the typical operational angle-of-attack range for transport aircraft is relatively 

low, with landing approach angles of attack typically around 8 degrees. Tus, substantially less 

shed vortex strength exists on the fuselage at those conditions in contrast to the extreme angles of 

attack used by fghters. Te McDonnell Douglas DC-9 and its subsequent derivatives have used 

fuselage forebody strakes for years to enhance directional stability at angles of attack within the 

transport operational environment. However, the STRATA Program was formulated to provide 

more fundamental information on the detailed aerodynamic efects of fuselage strakes for transport 

aircraft, including diferential defection for yaw control. 

Langley’s Gautam H. Shah led STRATA tests of a generic commercial transport model using a 

low-mounted swept wing and a conventional tail arrangement. Shah’s tests, which were conducted 

in the Langley 12-Foot Low-Speed Tunnel, covered a range of geometric strake variables, including 

span and chord, strake incidence angle, and the efectiveness of deploying a single strake as a 

directional control device. Te angle-of-attack range covered in the investigation was up to 25 

degrees. Unfortunately, study results indicated that the magnitude of yawing moments produced 

by a single strake was extremely low relative to those that can be generated by conventional rudder. 

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Although some applications, such as stability augmentation in yaw, might use low levels of control 

efectiveness, a larger issue surfaced when it was discovered that the yaw control provided by the 

single strake was extremely nonlinear, making any application as a control device more difcult 

and complex than a conventional control efector, such as a rudder. 

Even though the results of the STRATA tests were generally negative regarding using fuselage 

strakes for yaw control with representative transport aircraft in normal fight conditions, additional 

research might provide valuable information if such devices could improve emergency out-ofcontrol recovery capability for extreme attitude conditions at high angles of attack. 

Model confguration tested in Strake Technology Research Application to Transport 

Aircraft project. 

Passive Porosity 

Te passive porosity concept consists of a porous outer surface, a plenum, and a solid inner surface 

as shown in the illustration. Pressure diferences between high-and low-pressure regions on the 

outer surface communicate through the plenum, thereby modifying the pressure loading on the 

outer surface. In addition, a small amount of mass transfer into and out of the plenum occurs that 

changes the efective aerodynamic shape of the outer surface. Using passive porosity began in the 

early 1980s as a means of shock-boundary layer interaction control. In the late 1980s and early 

1990s, however, Langley researchers began a series of exploratory investigations to apply regions 

of porosity for aircraft stability and control enhancement. Richard M. Wood and Steven X. S. 

Bauer of Langley pioneered the initial control efector research that has since developed into a wellproven aerodynamic technology with a wide range of potential applications. 

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Passive porosity concept. 

Potential passive porosity control efector arrangements. 

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INNOVATIVE CONTROL EFFECTORS: SMART MUSCLES 

Wood and Bauer’s early research on the use of porosity to control aerodynamic moments included 

an efort with Michael J. Hemsch and Daniel W. Banks to evaluate the potential of porosity to 

alleviate large, uncommanded yawing moments generated by asymmetric vortex shedding on long 

pointed forebodies at high angles of attack. In the early 1990s, Bauer and Hemsch conducted an 

experimental wind-tunnel test in the Langley High-Speed 7- by 10-Foot Tunnel using porous 

and solid forebody models that demonstrated the ability of porosity to virtually eliminate such 

asymmetries. Wood and Banks immediately followed this test with a study in the 14- by 22-Foot 

Tunnel to couple forebody strakes with passive porosity to enhance the control authority of the 

both technologies. 

In the early 1990s Wood led several teams involving Industry and DoD investigating advanced 

aerodynamic control efectors for military aircraft. Maturation of passive porosity technology was 

a major focus in both eforts. Tese programs resulted in the development of two fully porous wing 

models that underwent extensive testing in the 14- by 22-Foot Subsonic Tunnel and have served as 

the basis for most industry investigations. 

Perhaps the best-known application of Langley passive porosity technology was to the U.S. Navy 

F/A-18E/F aircraft to help solve an unacceptable lateral “wing drop” characteristic that had been 

unexpectedly encountered during the early developmental fight testing of the preproduction 

aircraft. As discussed in Partners in Freedom, the availability of Langley’s database and experience 

with passive porosity proved to be a critical contribution to the resolution of the problem and was 

incorporated in subsequent production aircraft. In this application, porosity was used by Navy 

and NASA engineers to stabilize fow separation phenomenon encountered during transonic 

maneuvers, ensuring symmetric stall behavior. 

Langley researchers have also pursued the application of passive porosity for aircraft control efector 

systems. Applied to diferent areas of an aircraft, the use of porosity can permit the generation of 

a variety of control forces and moments. In applications, the porous cavities and interconnected 

plenums would be controlled and actuated by valves or other pneumatic control devices. Passive 

porosity has no external moving parts, preserves the vehicle outer mold lines, and provides a control 

force that varies linearly with vehicle lift in a predictable manner. 

Langley’s staf has also developed CFD methods to augment experimental studies by assisting 

in the analysis and design of passive porosity concepts. Te CFD breakthrough was by Daryl L. 

Bonhaus in 1999, when he successfully reformulated the passive porosity boundary conditions. 

His eforts greatly improved the accuracy of passive porosity analysis and allowed for the design of 

passive porosity control efectors. Te aerodynamic integration of passive porosity control efectors 

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into revolutionary new confgurations involves a departure from current aircraft design methods. 

Currently, aircraft airfoils are designed to maximize cruise performance, and then trailingedge faps (elevons, ailerons, etc.) are sized to provide sufcient moments to provide adequate 

control of the aircraft. With passive porosity concepts, the airfoils will be designed to generate a 

specifed pressure distribution that can be modifed by the actuation of the porosity device. Tus, 

the design of control efectors benefts greatly from the use of CFD. Modifcation, development, 

and validation of the highly successful Langley TetrUSS by Neal T. Frink, Daryl Bonhaus, 

Steve Bauer, and Craig A. Hunter has provided a powerful design tool for applications of the 

passive porosity technology. 

As might be expected, the numerous potential applications of passive porosity have resulted in 

extensive, ongoing cooperative research between Langley, industry, and DoD. In one such activity, 

Craig Hunter, Sally A. Viken, Richard Wood, and Steve Bauer led a design and analysis study of 

the application of passive porosity control efectors to an advanced multimission tailless fghter 

confguration developed under the Air Force Aero Confguration/Weapons Fighter Technology 

Program. Focusing on the low-speed, high angle-of-attack fight regime, the team used TetrUSS 

to develop a series of longitudinal and lateral-directional controllers. Study results indicated that 

passive porosity efectors could produce large nose-down control at high angle of attack, equaling 

or exceeding the control authority provided by conventional elevons. As discussed in the previous 

section on forebody control concepts, yawing moment is especially critical for low-speed maneuvers, 

and the study identifed several yaw control concepts that generated large yawing moments, with 

low levels of adverse rolling moments. 

Demonstrated success of passive porosity application to the F/A-18E/F prototype wing-drop 

problem, and the rapidly maturing aerodynamic analyses of advanced control efectors, resulted in 

a signifcant level of interest currently existing in future applications of the technology. Cooperative 

studies with industry and DoD are continuing, and all indications point toward extremely efective, 

versatile fow control devices based on passive porosity for aircraft control. Yet to be demonstrated, 

however, is the application and assessment of the concept to full-scale hardware and risk-reduction 

fight testing. 

Active Flexible Wing 

Te rapid emergence of advanced composite technology for wing design and fabrication stimulated 

signifcant national interest in the late 1980s and early 1990s in the potential integration of active 

control and fexible wings for weight savings. By reducing wing stifness requirements and instead 

employing advanced control technologies to avoid aeroelastic problems, the innovative use of 

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aeroelastic characteristics and control systems has promised a potential breakthrough in wing 

design. Designers of conventional civil and military aircraft are now constrained by aeroelastic 

and structural phenomena such as futter and aeroelastic-induced aileron control reversal. With 

revolutionary composite and control design procedures, researchers are exploring the benefts of 

using, rather than avoiding, wing fexibility efects. Langley researchers have been working in this 

research area since the middle-1980s, with participation by Center experts in aeroelasticity, futter, 

active controls, and advanced instrumentation. 

In the 1980s, two researchers at Rockwell International Corporation (now Boeing), Gerald Miller 

and Jan Tulinius, conceived an active fexible wing concept for advanced fghter aircraft. Te 

Rockwell concept exploited wing fexibility and active leading- and trailing-edge control surfaces 

to provide high-performance roll rates without the use of all-movable horizontal tails. Discussed 

in a previous section on control of aeroelastic response, a cooperative program among Langley, the 

U.S. Air Force, and Rockwell was formalized to research and demonstrate this active fexible wing 

Multiple exposure photograph of the active fexible wing model mounted 

in the Langley 16-Foot Transonic Tunnel. 

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(AFW) concept. Active control concepts considered during the research efort included active 

futter suppression and rolling-load maneuver alleviation. Te active futter suppression system’s 

goal was to use multiple surfaces and sensors to prevent two futter modes occurring simultaneously. 

For the rolling-maneuver load alleviation design, the goal was to reduce wing loads at multiple 

points on the wing while executing roll maneuvers representative of fghter aircraft. As the research 

eforts intensifed, Langley researchers successfully completed additional tests in 1989 and 1991 

involving more than 20 researchers. Contributors to the program included Boyd Perry, Stan Cole, 

Carey S. Buttrill, William M. Adams, Jr., Jacob A. Houck, Anthony S. Pototzky, Jennifer Heeg, 

Martin R. Waszak, Vivek Mukhopadhyay, and Sherwood H. Tifany. Key accomplishments of 

this second AFW Program included single- and multiple-mode futter suppression, load alleviation 

and load control during rapid roll maneuvers, and multi-input/multi-output multiple function 

active controls tests above the open-loop futter boundary. A highlight of the efort was a special 

issue of the highly respected AIAA Journal of Aircraft for January-February 1995 that summarized 

the research details, fndings, and conclusions of the project. 

After decades of NASA, DoD, and industry research on actively controlled fexible wings in wind 

tunnels, the next major challenge, piloted full-scale aircraft fight demonstrations, was ready to be 

addressed. To meet the challenge, NASA, the Air Force, Boeing, and Lockheed Martin initiated 

and are now participating in an Active Aeroelastic Wing (AAW) Flight Program at NASA’s 

Dryden Flight Research Center using a modifed Boeing F/A-18 aircraft. Te program goal is 

to demonstrate improved aircraft roll control through aerodynamically induced wing twist on 

a full-scale high performance aircraft at transonic and supersonic speeds. Data will be obtained 

to develop design information for blending fexible wing structures with control law techniques 

to obtain the performance of current day aircraft with much lighter wing structures. Te fight 

data will include aerodynamic, structural, and fight control characteristics that demonstrate and 

measure the AAW concept in a comparatively low cost, efective manner. 

Begun in 1996, the AAW Program completed the wing modifcations required for the research 

program. In preproduction versions of the F/A-18, the wing panels were relatively light and fexible. 

During preproduction fight tests (particularly at high-speed, low altitude conditions), the wings 

were too fexible for the ailerons to provide the required roll rates. Tis unacceptable result occurred 

because the high aerodynamic forces against a defected aileron and resulting wing torsion would 

cause the wing to defect in the opposite direction, causing severe degradation of roll control in the 

intended direction. Te F/A-18 production aircraft were subsequently ftted with stifer wings to 

minimize the undesirable loss of roll control. 

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NASA’s active aeroelastic wing F/A-18A research aircraft maneuvers during a test mission. 

Te wing panels on a Dryden F/A-18 research aircraft were modifed for the AAW research 

program. Several of the existing wing skin panels along the wing’s rear section just ahead of the 

trailing-edge faps and ailerons have been replaced with thinner, more fexible skin panels and 

structure, similar to the preproduction F/A-18 wings. In addition, the research airplane’s leadingedge fap has been divided into separate inboard and outboard segments, and additional actuators 

have been added to operate the outboard leading-edge faps separately from the inboard leadingedge surfaces. By using the outboard leading-edge fap and the aileron to twist the wing, the 

aerodynamic force on the twisted wing will provide the rolling moments desired. As a result, the 

fexible wing will have a positive control beneft rather than a negative one. In addition to the 

wing modifcations, a new research fight control computer has been developed for the AAW test 

aircraft, and extensive research instrumentation, including more than 350 strain gauges, has been 

installed on each wing. 

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Langley’s Jennifer Heeg leads a team of dedicated and skilled professionals currently conducting 

research within the AAW Program on the development and validation of scaling methodology 

for reliable wind-tunnel projections to fight. Te team is applying a Langley method called wind 

tunnel to atmospheric mapping (WAM) for scaling and testing a static aeroelastic wind-tunnel 

model of the AAW aircraft. Te WAM procedure employs scaling laws to defne a wind-tunnel 

model and wind-tunnel test points such that the static aeroelastic fight-test data and wind-tunnel 

data will be correlated throughout the test envelopes. Te specifc scaling is enabled by capabilities 

of the Langley TDT and by relaxation of scaling requirements present in the dynamic problem 

that are not critical to the static aeroelastic problem. 

AAW fight tests began in November 2002 with checkout and parameter identifcation fights. 

New fight control software was then developed based on data obtained during 50 research fights 

over a 5-month period in 2003. Te Langley-Dryden team evaluated the controls’ efectiveness in 

twisting the wing at various speeds and altitudes. A second series of research fights planned to last 

into 2005 is scheduled to evaluate the AAW concept in a real-world environment. Obvious issues 

regarding futter suppression, failure modes, and cost-beneft trades remain to be addressed before 

AAW concepts can be applied to production aircraft. 

Te NASA Smart Vehicle Program 

Langley’s researchers had aggressively pursued advanced control efector studies with industry and 

DoD in the 1990s. In one of the most important cooperative projects, Richard M. Wood served as 

team lead for a NASA-industry-Air Force military team (1990 to 1993) that included members from 

Langley, NASA Ames, McDonnell Douglas, and the DoD. Te focused activity resulted in the 

conception and development of four advanced control efector technologies that were subsequently 

adopted by industry. Te four patented technologies were passive porosity, advanced planforms, 

micro drag bumps, and advanced forebodies. Almost a decade later, an opportunity arose to carry 

some of the concepts to fight tests. 

As discussed in other sections of this document, NASA initiated a program known as RevCon 

in 2000 to accelerate the exploration of high-risk, revolutionary technologies. Te nine projects 

initially selected included a study known as the Smart Vehicle (SV) Program. Te Smart Vehicle 

was envisioned by NASA and its partners to be an unmanned advanced technology demonstrator 

that would demonstrate the application of a set of novel aerodynamic efectors and an advanced 

adaptive vehicle management system to enhance the operational efectiveness of revolutionary air 

vehicles. Specifcally, the demonstrator would use novel aeroefectors as primary control devices 

in the research envelope, demonstrate the efectiveness of an adaptive closed loop vehicle control 

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system that accommodates anomalies in the research envelope, and defne the benefts of integrating 

an adaptive control system and novel actuators. Te fight envelope was to include a design Mach 

number of about 0.8 at an altitude of 25,000 ft. Te project would be conducted by a team led 

by Langley, with team members including Lockheed Martin Tactical Aircraft Systems (LMTAS), 

Physical Sciences, Inc., Tel Aviv University, Naval Air Systems Command, and NASA Dryden 

Flight Research Center. 

Initially, the team considered several advanced control efector concepts, including passive porosity, 

spanwise blowing, seamless control efectors, infatable faps, pulsed jet vortex generators, oscillatory 

blowing, wing decamber “bumps,” drooped leading-edge faps, and reaction control systems. Te 

team judged each of the foregoing efector concepts (and others) on research merit in terms of 

technology readiness level and disciplinary research and development required. Te initial control 

efector concepts chosen were passive porosity, seamless control efectors, spanwise blowing, and 

decamber bumps. Fluidic thrust vectoring was identifed as a desirable yaw control efector but was 

eliminated to reduce program cost. 

Artist’s sketch of the RevCon Smart Vehicle Demonstrator. 

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Under the teaming agreement of the RevCon SV project, Langley would be responsible for project 

lead; risk reduction studies in low- and high-speed wind tunnels including the TDT and 16-Foot 

Transonic Tunnel facilities; design and development assistance of the advanced control laws to be 

used by the vehicle; development of design criteria for the passive porosity and spanwise blowing 

concepts; and vehicle fabrication, assembly, integration, and selected ground testing. Following the 

SV demonstrator’s fabrication and initial checkout at Langley, it would be shipped to Dryden for 

fnal assembly, prefight completion and checkout, and research fight tests. 

Langley’s Manager for the SV Program was Jean-Francois M. Barthelemy, assisted by Scott G. 

Anders and Henry S. Wright. Major Langley contributions to the program were provided by Bobby 

Berrier (lead for aerodynamic data base development), Steven X. S. Bauer (porosity), Tomas M. 

Moul (aerodynamics), Richard F. Catalano (system studies), Stuart Johnson (system studies), John 

V. Foster (wind-tunnel testing), Richard J. Re (wind-tunnel testing), and Richard DeLoach (windtunnel techniques). 

By spring of 2001, the NASA-industry team had conducted a phase I study and developed an 

attractive project within 8 months. At that time, NASA had developed an interest and vision in 

“morphing aircraft” that would employ many of the concepts involved in the SV demonstrator, and 

Elements of the Smart Vehicle. 

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the SV concept was viewed by many as a stepping-stone to future revolutionary aircraft activities. 

However, it was also recognized that many of the technologies required additional research and 

development, and that the anticipated costs of the demonstrator program would be large. During 

the phase I studies, the demonstrator vehicle design had accelerated: conceptual design, initial 

structural and futter analyses, CFD calculations for performance, and 6-degree-of-freedom fight 

simulations had been accomplished; systems-level analyses of various proposed technologies had 

been completed; and two wind-tunnel entries had been accomplished (low-speed confguration 

screening and transonic performance and control efector evaluations). 

Anticipated milestone events included a NASA RevCon go-ahead for phase II activities in the 

fall of 2001, shipping the vehicle to Dryden in the fall of 2004 and conducting the frst fight 

tests during the summer of 2005. Unfortunately, NASA’s funding for RevCon was redirected to 

providing a return-to-fight capability for the NASA X-43A (Hyper X) Program following the X43A accident on June 2, 2001. NASA subsequently terminated its RevCon Program on September 

30, 2001. 

Following the cancellation of the RevCon Program, Langley provided advocacy and funding for a 

follow-up project within its Revolutionary Airframe Concepts Research (RACR) project. Known 

as the Aeronautical Flight Vehicle Technologies Demonstrator (AVTD) project, a similar SV 

vehicle confguration was retained based on a version of the LMTAS Innovative Control Efector 

Vehicle that had been used for several studies on advanced fghters, including an uninhabited 

air combat system. In addition, the new project’s goal was changed to provide a robust, reusable, 

unmanned, modular high-performance fight demonstrator to serve as a test bed for maturation of 

advanced technologies, and the scope of applications was changed to emphasize potential civil as 

well as military applications. 

By 2003, the research within AVTD had proceeded to include systems-level assessments of control 

efectors, vehicle conceptual design and cost estimates, wind-tunnel entries in the Langley 16-Foot 

Transonic Tunnel and the Langley 16-Foot TDT, supporting CFD studies for fow diagnostics and 

analysis, and simulation of fying qualities. Bobby L. Berrier, John Foster, Jerome H. Cawthorn, 

Richard J. Re, Craig A. Hunter, and Steve Bauer had conducted aerodynamic studies, and several 

options for vehicle confgurations (wing planforms and confguration layouts) had been assessed. 

A 7-week test program in the 16-Foot Transonic Tunnel at Mach numbers from 0.3 to 0.9 and 

angles of attack from –5 to 15 degrees signifcantly advanced the state of the art in advanced control 

efectors. Te team conducted parametric studies and data were obtained on the efectiveness 

of passive porosity control efectors, seamless trailing-edge faps, porosity and trailing-edge 

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interactions, deployable bumps, and a rudder. Te staf used CFD also to predict the efectiveness 

of deployable bumps and passive porosity, providing good qualitative trends. 

Unfortunately, NASA cancelled the project in fscal year 2004 because of resource constraints in 

the face of relatively large costs projected for SV fight tests. 

Status and Outlook 

Te remarkable progress made by Langley researchers on advanced innovative control efectors 

continues to generate signifcant interest for applications, particularly within the military 

community. With the advent of highly lethal, signature-sensitive combat environments, designers 

are striving for unconventional approaches to maximize performance and handling qualities 

while maximizing stealth and reducing costs, maintenance, and vehicle weight. New technology 

felds are being pursued to maximize the efectiveness of advanced controls. For example, the 

introduction of controls allocation technology has reduced the concern about unwanted crossaxis moments from each efector. Tis technology was motivated by confgurations that had 

several control efectors and could beneft from blending of the efector inputs to minimize control 

defections, yet provide the desired control moments. Control law software has been developed that 

can provide the commanded control moment by combinations of control positions to optimize 

control strategy. One application is to provide proverse yawing moments with roll control while 

minimizing additional yaw control. At this time, however, the major barrier to implementation 

of many of the concepts is the lack of full-scale aircraft fight experience to resolve numerous 

application issues that cannot be resolved at model scale. 

With the introduction of high-performance Uninhabited Air Combat Vehicles, many technology 

concepts conceived and developed at Langley are now appropriate for future applications. Langley’s 

staf is continuing its quest to provide designers with valuable technology information for use in 

design and trade studies for future air vehicles. Undoubtedly, extensive demonstrations of the 

technologies discussed herein by manned or unmanned vehicles will occur in the near future. 

298 Innovation in Flight 
Personal Air Transportation Concepts: On-Demand Revolution 

in Air Travel 

Concept and Benefts 

By the 1990s, demand for public air transportation in the United States had intensifed to the point 

that widespread frustration over system shortcomings existed. Commercial fight delays due to the 

cascading efects of bad weather, inconvenient and indirect fight schedules, lack of physical comfort 

and overcrowding within airports and airplanes, and excessive “lost time” getting to and from 

remote airports had become more frequent. Tese frustrations stimulated the technical, regulatory, 

and political communities to consider and evaluate proposals for innovative modifcations to the 

current air transportation system. Following the world changing events of September 11, 2001, the 

resulting adjustments to commercial aviation operations to ensure security, and the delays caused 

by security breaches, further aggravated the lost time and personal inconvenience of air travel. 

Assessments of the current system’s shortcomings have focused on the problems created since 

airline deregulation resulted in the centralized “hub and spoke” system now used by most major 

air carriers. Over 75 percent of aviation passenger trafc within the United States is conducted 

through only 30 major airports. Although the hub and spoke system will continue as a vital asset 

for long distance travel, it does not serve rural, regional, and intraurban travel very efectively. For 

travel distances of 100 to 500 miles, the public chooses to use automobiles 20 times more often 

than aircraft. Considering that the average home-to-destination auto speed for these trips is only 

35 mph, and that projected highway congestion over the next 25 years will reduce this speed even 

further, a critical need exists for a revolutionary form of faster travel that can avoid the gridlock of 

either highways or hub and spoke airports. More frequently, analysis of the problem reveals that 

expanded use of over 5,000 public general aviation airports within the existing U.S. infrastructure 

might provide a solution to the anticipated future decline in public mobility. 

Innovative concepts for personal air travel that have been periodically revisited over the past 80 

years include personal-owner general aviation aircraft; personal air travel through distributed, ondemand air taxi operations; and even futuristic, self-operated personal air vehicles (PAV) capable 

of both roadable and airborne operations, as well as short-feld operations from neighborhood 

roads and “at home” storage. Such concepts use the distributed air operational scenarios discussed 

previously and are compatible with an innovative and revolutionary vision of potential future air 

transportation. Te unfulflled perspectives within these visions would permit an unprecedented 

level of mobility for average citizens, resulting in signifcant improvement in productivity and 

quality of life. 

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Within its charter and mission to defne and develop concepts to improve the quality of life for 

the U.S. public, and to conceive and mature technologies required for new systems and vehicles, 

NASA is conducting research designed to advance and accelerate the state of air mobility. 

Te Nation’s underused public airports might provide signifcant public mobility. 

To permit greater mobility and freedom in air travel, near-term NASA goals have been to develop 

and demonstrate technologies enabling the safe and cost-efective operations of today’s small aircraft 

from the vast number of public airports. Additional eforts are underway to provide designers 

with methods of transforming today’s personal-owner aircraft to eliminate extensive current public 

perceptions of unacceptable operational cost, lack of comfort, lack of safety (especially in adverse 

weather conditions), objectionable noise, and unacceptable training time and costs. Vehicleoriented research goals are to develop technology for a small airplane that can fy out of small 

airports, to keep the cost less than $100,000 while being equipped for all weather operation, and 

to be unobjectionably quiet to the surrounding community. NASA is also conducting research on 

pilot-vehicle automation to make fying nearly as simple as driving a car. 

Langley has also conducted research to enable the design of small (two passenger) personal-owner 

aircraft that have door-to-door travel capability, including the ability to travel in a limited roadable 

fashion on side streets, while taking of and landing at very small airfelds. While the desire to 

have a true fying car is widespread and understandable, NASA researchers believe that the dream 

of the fying car will continue to be unfulflled even 25 years from now. Te problems that result 

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when full highway roadability is coupled with fight capability will continue: vehicles that aren’t 

very good cars, aren’t very good aircraft, and are much more expensive than both. 

Challenges and Barriers 

An on-demand aviation system, with convenience, low costs, and proven safety, has been a dream 

of aviation innovators and futurists since the earliest days of fight. Te proposed distributed air 

operational system’s capacity to provide this capability has been frmly blocked in the past by a 

multitude of technical, regulatory, economic, and operational issues. Te following discussion 

of challenges and barriers provides background on that which must be overcome to permit the 

successful implementation of a distributed, on-demand air system. Te issues are addressed for 

two diferent vehicles: a near-term advanced general aviation-type aircraft designed for intercity 

and rural travel from nonradar-equipped small airports, and a futuristic roadable aircraft with 

ultra–short-feld takeof and landing capability designed for intraurban short trips. Both vehicles 

might be fown by either air-taxi pilots or by private owners. NASA and its partners are engaged 

in pioneering eforts to accelerate solutions to existing and anticipated challenges and barriers 

for both types of aircraft. Trough its programs on general aviation technologies, small aircraft 

transportation systems, and personal air vehicles, the Agency is contributing signifcant stimuli 

toward this objective. 

Disciplinary Challenges 

Te development of economically feasible air vehicles with satisfactory performance, fying qualities, 

and safety is a traditional NASA mission. Within the disciplines of aerodynamics, propulsion, 

stability and control, structures, and fight deck technology, NASA supplies advanced concepts 

and data for use by designers to ensure that the mission requirements of new vehicles can be met. 

An advanced general aviation aircraft envisioned for intercity travel from rural airports creates 

technology requirements that are driven by cost, safety, security, environmental compatibility, 

and ease of use. Within the disciplines, these requirements translate into technical simplicity and 

innovative approaches to lower acquisition and operational costs. For example, reliable propulsion 

systems comparable with automotive systems will be mandatory. Structures and materials must 

be low cost, easily replaced, damage tolerant, and provide a high level of crashworthiness. For 

applications envisioned, aerodynamic characteristics of a vehicle are probably within the state of 

the art; however, the pilot-vehicle interface for fight planning, guidance, stability, and control 

will have to be exceptionally good to permit safe operations in marginal weather conditions by 

novice pilots. 

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Te disciplinary requirements for a futuristic intracity aircraft are tremendously more demanding 

than an intercity vehicle. Envisioned as the ultimate personal-owner aircraft with ultra–short-feld 

takeof and landing capability and all-weather operations, the vehicle requires extensive advances 

in disciplinary technologies far beyond levels available today. Sophisticated powered-lift concepts, 

including morphing technologies like circulation control, will be required, as well as high powerto-weight engines, sophisticated control systems with extensive artifcial stabilization, advanced 

navigation and guidance, and lightweight structures. 

Operational Challenges 

Arguably, the challenges and barriers to future personal air transportation are more dominant in 

the area of operations than those within the technical disciplines. For near-term aircraft, operating 

from small, nonradar equipped airports will pose stringent requirements on situational awareness 

and collision avoidance (both airborne and ground operations), guidance displays, and weather 

awareness. Te far-term personal air vehicle faces even more issues. Te complexity of fying an 

airplane in all-weather conditions (compared with driving a car), and the difculty and costs 

involved in gaining a pilots license, create immediate barriers unpalatable to most of the public. 

Te issues of regulatory requirements, certifcation, liability, and operational fexibility will require 

years of study, debate, and resolution before the dream can be realized. 

Economic Challenges 

No single factor afects the public’s interest and willingness to use new technology more than 

cost. Acquisition cost of an excessively sophisticated vehicle (compared with automobiles) will 

immediately undermine advantages of new transportation capability and deter the application of 

advanced technology, no matter how impressive the benefts may be. Solutions regarding additional 

costs associated with pilot training and currency, maintenance, insurance, medical certifcates, and 

other factors will require innovative approaches and perspectives. 

In summary, the challenge of providing increased mobility and productivity to the public via 

advanced personal air transportation involves an extensive and complicated series of issues that 

ignite classical confrontations between technological, regulatory, and economic factors. Many 

argue that these same factors have faced every step of advancement in transportation, from sailing 

ships to locomotives to automobiles, yet when the barriers were ultimately addressed, new forms of 

transportation were adopted, and naysayers were proved wrong. In its role as an advanced research 

and development organization, NASA is addressing these issues. 

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Langley Activities 

Although NASA has not conceived, developed, and demonstrated a vehicle appropriate for the 

futuristic personal air vehicle vision, early contributions include concepts, technology, and data 

in the areas of aerodynamics, fight dynamics, structures and materials, fight deck technology, 

propulsion, and controls, all key to the potential success and airworthiness of the vehicles. Past 

Langley research on relatively inexpensive concepts for individual airborne transportation are 

worthy of note. 

During the 1950s and 1960s Langley conducted research on personal “fying platforms.” 

In the middle 1950s, considerable interest was expressed by the U.S. Army and associated industries 

over development of a general-purpose vertical takeof and landing (VTOL) aircraft that could 

be operated by a single person and serve as a reconnaissance aerial vehicle. As envisioned, the 

vehicle would be able to hover or fy forward at speeds up to about 50 kts. Military versions 

would carry a payload of about 1,000 lb, and it was expected that the proposed vehicle would be 

simpler in construction and easier to operate and maintain than a small helicopter. Potential civil 

applications for the concept were quickly recognized, and studies of “fying platform” vehicles 

began to emerge. 

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With an extensive ongoing research program in rotorcraft and VTOL technology in the 1950s and 

1960s, researchers at Langley conducted several investigations of the performance, stability, and 

control of such concepts. Te necessity of minimizing the rotor diameter and slipstream velocity, 

and for providing protection for surrounding personnel and equipment, prompted the use of ducted 

fans—rather than rotors—which became a focal point of the Langley studies. 

Under the direction of Marion O. McKinney, a team of Langley researchers conducted conventional 

static force and moment wind-tunnel tests as well as free-fight tests of several confgurations 

incorporating either two- or four-duct arrangements. As early as 1954, McKinney’s team started 

a series of free-fying model tests of ducted-fan fying platform confgurations. Robert H. Kirby, 

Lysle P. Parlett and Charles C. Smith, Jr., led the research eforts, and early results revealed two 

serious problems inherent in any fxed-geometry ducted-fan confguration in forward fight. Tese 

problems are an undesirably large forward tilt angle of the platform required for trim at high 

speeds and nose-up pitching moment that increases rapidly with forward speed. Solutions to these 

two problems are imperative for practical operation of ducted-fan vehicles. 

Parlett’s test results indicated that a tandem two-fan arrangement exhibited less severe tilt angle 

and pitching moments than a side-by-side fan arrangement, but the tandem confguration required 

appreciably more power for forward fight. Analysis of these early results indicated that defciencies 

might be alleviated by departing from the concept of ducted fans fxed with respect to the airframe 

and tilting the ducts for the forward fight condition. Subsequent tests by Smith with the tiltingduct arrangement showed that the problems have been minimized, providing pioneering research 

data that contributed to a rising interest in compact tilt-duct aircraft confgurations, such as the Bell 

X-22 research aircraft in the 1960s. During the height of VTOL research at Langley in the 1960s, 

ducted-fan vehicles were studied in detail in the Langley 30- by 60-Foot (Full-Scale) Tunnel and the 

Langley 14- by 22-Foot (V/STOL) Tunnel. Current knowledge of the aerodynamic performance, 

stability, and control characteristics of this class of vehicle was contributed by research studies at 

Langley and at NASA Ames Research Center. 

Langley has led the Agency’s eforts in advancing the personal air transportation system capabilities 

for the past decade. Te program’s conception, planning and success to date can be attributed to the 

personal expertise, dedication, and leadership of Langley’s Bruce J. Holmes, who is internationally 

recognized for his leadership and personal technical research for general aviation. Rising through 

the technical ranks, Holmes progressed from extensive technical contributions as a researcher for 

advanced general aviation aircraft confgurations to a visionary program manager responsible for 

integrating and coordinating NASA, industry, FAA, and academic researchers on national-level 

programs to improve the national air transportation system. Most project activities discussed in 

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this section (especially the near-term objectives and goals) were conceived or strongly infuenced 

by his direction. Another NASA leader in visionary and futuristic perspectives on technology 

and personal air travel is Dennis M. Bushnell, Chief Scientist of Langley Research Center. His 

persistence in achieving the unthinkable, and his challenges to researchers to think beyond the 

envelope, has inspired numerous advances in innovation and revolutionary concepts at Langley. 

Bushnell’s personal interest and managerial support for far-term PAVs of the future has provided 

the opportunities for Langley’s researchers to pursue creativity and pioneering eforts in what is 

recognized as an exceedingly difcult research area. 

Te following discussion provides an overview of some of the most critical Langley research 

programs and contributions to the personal air transportation arena. Tree research activities 

have been especially noteworthy in this topic. Tey are the NASA Advanced General Aviation 

Transport Experiments (AGATE) Program, which provided advanced technology to permit the 

domestic general aviation industry to remain a vibrant component of aviation; the NASA Small 

Aircraft Transportation System (SATS) Program, which is in the process of demonstrating the 

ability of advanced technology to permit routine operations of small aircraft from rural airports; 

and PAV studies, which explore the ability of technology in the near- and far-term years to provide 

revolutionary personal air transportation vehicles. 

Te NASA Advanced General Aviation Transport Experiments Program 

Following the almost total collapse of the U.S. general aviation industry in the 1980s, the Nation 

searched for mechanisms to provide the resurgence required to reestablish this vital segment of the 

air transportation system. Tis decline included signifcant decreases in small aircraft deliveries, 

general aviation feet size, fight hours, public use airports, pilot population, and new student 

pilots. At its peak in 1978, the general aviation industry delivered 14,398 aircraft. In 1994, the 

number of aircraft deliveries had fallen to an all-time low of 444. Te average age of general 

aviation aircraft fying at that time was about 30 years. Flight deck technologies in use dated back 

as late as the 1950s, and piston propulsion technologies had remained unchanged for the past 

40 years. Along with modifcations of product liability issues, the potential impact of advanced 

technology to improve safety, reduce operating and training costs, and stimulate interest in general 

aviation was pursued. 

Building on his long established relationship with the general aviation industry, Langley’s Bruce 

Holmes took the lead in the formulation of cooperative planning with industry to create a new 

future for general aviation. Following Holmes’ highly successful advocacy eforts within NASA 

and industry, in 1994 NASA created an AGATE Consortium under the general aviation element of 

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the Advanced Subsonic Technology Program Ofce to revitalize national general aviation through 

the rapid development and felding of new technologies, with a view toward providing an impetus 

for a new small aircraft transportation system. 

Under the direction of Holmes and his Deputy Michael H. Durham, the AGATE team focused 

on goals that included the development of afordable new technologies, as well as new approaches 

to meeting industry standards and certifcation methods for airframe, cockpit, fight training 

systems, and airspace infrastructure for next generation single pilot, four to six seat, all-weather 

light airplanes. Te AGATE alliance eventually grew to more than 50 members from industry, 

universities, the FAA, and other government agencies. Starting with NASA seed funding of $63 

million in 1994, NASA, the FAA, the Small Business Innovation Research Program (SBIR), 

industry, and universities pooled nearly $200 million in combined resources among 39 cost sharing 

partners. About 30 other partners also joined the efort as noncost sharing, supporting members of 

the AGATE Consortium, totalling nearly 70 members. 

Te cumulative result of the AGATE alliance produced a revolution in the research and technology 

deployment capacity for all sectors of the general aviation industry. AGATE provided a voice 

for industry to provide national clarity and action on key technology development, certifcation, 

and standard-setting activities. During the AGATE Program, which ended in 2001, the general 

aviation industry research and technology capacity advanced from virtually nonexistent to worldclass in avionics, engines, airframes, and fight training. Integrated with these advances was the 

rising advocacy for deployment of small aircraft at the Nation’s distributed public airports for 

unprecedented advances in personal mobility and productivity for the public. Extensively cited as 

a classic example of NASA aeronautics at its best, the AGATE Program is viewed as the catalyst 

responsible for current interest in expanded use of small aircraft transportation systems. 

Te NASA Small Aircraft Transportation System Project 

Following the highly successful AGATE Program, Bruce Holmes and his team of NASA-industryacademia-FAA partners turned attention to the next step in demonstrating potential benefts of a 

small aircraft transportation system for the U.S. public. Holmes began a difcult advocacy efort, 

which entailed a major step up in challenges from the technically focused AGATE Program. 

Te new transportation system-focused program would entail numerous nontechnical factors not 

in the immediate control of NASA, such as local politics, community planning, and regulatory 

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Te NASA SATS Program envisions the on-demand use of small aircraft from distributed public airports. 

responsibilities. Despite outspoken critics and skeptics, Holmes and his team secured NASA 

funding in 2001 to begin a new program, called SATS, which would “put wings on America” and 

minimize the transportation woes and gridlock associated with clogged interstates and hub-andspoke airports. 

SATS highlighted the fact that, away from the congested hub-and-spoke airports, underused 

capacity at over 5,000 public use airports is abundant. Unfortunately, fewer than 10 percent of 

public airports have precision instrument guidance, communications, and radar coverage for safe 

and accessible near-all-weather operations. To move to the new paradigm of small aircraft operating 

as a key component of the proposed transportation system, fight deck and fight path technologies 

and operating procedures would have to be developed to provide the missing components. 

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Many enabling technologies from the AGATE Program and a related program, the General 

Aviation Propulsion (GAP) Program managed by the NASA Glenn Research Center were poised 

to contribute to this futuristic vision. Tese technology advances included: 

• New turbine engines with revolutionary thrust-to-weight and cost metrics 

• Commercial of the shelf (COTS)-based avionics with vast improvements in cost, reliability, 

and capabilities 

• Highway-in-the-sky graphical pilot guidance systems 

• New approaches to crashworthiness 

• Streamlined composite airframe manufacturing techniques 

• Ice protection technology 

• Digital engine controls (for single-lever power control) 

• Graphical weather information in the cockpit 

• Advanced fight training and pilot certifcation processes 

With such technology now available, the SATS vision is to provide the Nation with an alternative 

to existing road and airline choices for travel. Goals include hub-and-spoke-like airport 

accessibility to the smallest of neighborhood airports, without needing radar and control towers, 

and without needing more land for protection zones around small airports. Obviously, this travel 

alternative must be cost-competitive with existing choices and meet public expectations for safety 

and accessibility. 

Early consumers of SATS would have access to air-taxi-like systems with hired pilot operations. 

Te SATS project goal is to develop technologies and operating capabilities to enable afordable, 

on-demand, near all-weather access to even the smallest of markets. Scheduled services may also 

appear in more dense transportation markets as entrepreneurs discover efective ways to meet 

market demands. 

Te congressional budget appropriation for the SATS Program included a mandate to prove that 

the SATS concept works. Tis mandate includes demonstration of four operational capabilities 

enabled by the integration of emerging technologies from the AGATE and GAP Programs. Tese 

four capabilities are: 

• Higher-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 trafc management system 

with complex fows and slower aircraft; and 

• Improved single-pilot ability to function competently in complex airspace 

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Representative cockpit display for Small Aircraft Transportation System applications. 

Initial Langley planning for the SATS efort was led by Holmes and Durham within the General 

Aviation Program Ofce. Key NASA researchers included James R. Burley, David E. Hahne, 

Stuart Cooke, and Allen C. Royal. Later, a team of implementers was assigned to focus the SATS 

eforts, conduct the research, and ensure the success of the project objectives. Jerry N. Hefner was 

assigned as Project Manager for SATS, assisted by Langley researchers Guy Kemmerly, Sally C. 

Johnson, Mitchel E. Tomas, and Stuart A. Cooke, Jr., to conduct the SATS project in a publicprivate partnership with the FAA and the National Consortium for Aviation Mobility. 

In view of the highly successful consortium-based approach used in AGATE, NASA facilitated 

the formation of a public-private alliance to encompass state-based partnerships for the execution 

of the SATS Program. Tese partnerships participate in continued technology development, 

system analysis and assessment, technology integration, and fight demonstrations of SATS 

operating capabilities. 

In May 2002, NASA announced it had selected a partner for a joint venture to develop and 

demonstrate air mobility technologies for transportation using small aircraft and small airports. 

Known as the National Consortium for Aviation Mobility (NCAM), of Hampton, Virginia, 

NCAM leads a public-private consortium of more than 130 members. NCAM SATSLab members 

are: Maryland and Mid-Atlantic SATSLab (University of Maryland Research Foundation), North 

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Carolina and Upper Great Plains SATSLab (Research Triangle Institute), Southeast SATSLab 

(Embry Riddle Aeronautical University), Virginia SATSLab (Virginia Department of Aviation), 

Michigan SATSLab (Munro and Associates), and Indiana SATSLab. 

Te Langley Small Aircraft Transportation System Project Ofce, the FAA, and the NCAM 

SATSLabs became the driving forces behind SATS. Te U.S. Congress approved $69 million for 

the 5-year proof-of-concept period. 

Under Hefner’s leadership, Langley, NCAM, and the FAA immediately worked toward a middle 

2005 proof-of-concept demonstration of new operational capabilities geared toward technologically 

advanced small aircraft and small airports. Te 2005 demonstration location was chosen to be 

Danville Regional Airport, Danville, Virginia. During the 3-day event, organizers planned to ofer 

participants a look at the potential impacts that additional small aircraft trafc could have on the 

Nation’s skies and the business prospects that could be available for air taxis and other services 

interested in capitalizing on a new air transportation system that would complement existing 

major airports. 

Several technical concepts played a key role in the 2005 demonstration. Te now well-known Global 

Positioning System (GPS) is an absolute necessity for SATS, providing critical data on aircraft 

position and track. Langley researchers worked to make GPS-based systems cheaper, smaller, and 

easier to install, particularly for retrofts to older aircraft. A system known as Automatic Dependent 

Surveillance-Broadcast was developed to emit a transmission every few seconds listing information 

such as location, speed, and destination of the aircraft. Tese data can be tracked by nearby pilots, 

air trafc controllers or others, providing airborne trafc awareness to others. A multifunction 

Cockpit Display of Trafc Information (CDTI) system compiles information transmitted by other 

aircraft emitters and give the pilot a visual representation of airborne activity and potential collision 

events. SATS also explored the use of enhanced vision concepts for improved visibility at airports 

without landing light systems. Te highway in the sky display concept (discussed in another 

section of this document regarding synthetic vision) would use GPS and other sensors, such as 

Forward Looking InfraRed (FLIR), to create an animated fight path, displayed on a computer 

screen or even projected onto the inside of the windshield, for maneuver guidance and fight 

path information. Finally, NASA explored the use of single-pilot performance-enhancing systems 

that increase safety while reducing the need for two-person aircrews. In such systems, onboard 

computers monitor aircraft systems, warn of a malfunction, and even diagnose the problem and 

possibly ofer a fx. Another computer-based aid is a concept for a virtual copilot that could handle 

tasks such as calling out altitudes or watching the fight path during the eventful fnal approach 

phase of a fight. If implemented on a laptop computer or even a personal data assistant, some 

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of these concepts could conceivably be plugged into an older aircraft for low-cost retroft. Tese 

technologies were developed and matured by researchers at Langley, industry, and at SATSLabs 

across the country. 

Te SATS 2005: A Transformation of Air Travel event was an impressive success at Danville on 

June 5-7, 2005. Te three-day event attracted more than 3,000 aviation enthusiasts and was 

considered a great success in showcasing new aviation technologies. FAA Administrator Marion 

Blakey and NASA Administrator Michael Grifn presented keynote addresses stressing the value of 

the SATS vision. SATS personnel explained technologies and operating capabilities to a standingroom-only crowd with the help of live video feeds and pre-taped segment shows on a giant screen. 

During the live technical demonstration, six airplanes equipped with advanced cockpit displays 

were able to land safely and efciently in a small airport that normally has no radar or air trafc 

control support. 

Now that the 5-year proof-of-concept SATS project is complete, it is hoped that the SATS concept 

will continue with the development of federal regulations, airspace procedures, and industry 

products to accommodate SATS trafc. 

Personal Air Vehicle Research 

In addition to the relatively near-term objectives of the SATS Program and its focus on productive, 

on-demand use of existing small airports, NASA has taken a fresh look at innovative and 

revolutionary vehicle concepts that address the futuristic vision of PAVs. In accordance with 

NASA’s mission to conduct long-term, high-payof revolutionary research, Langley researchers 

assessed the potential of current-day and emerging technologies to enable the design of technically 

and economically feasible consumer-piloted vehicles. Langley researchers were extremely informed 

in and sensitive to the shortcomings of the many failed previous attempts to exploit the owneroperated light aircraft market and planned a relevant, phased program to develop technologies 

required for the concept. Te scope of current Langley studies began with advanced vehicles that 

incorporated technologies developed within the AGATE and SATS Programs and extended the 

vision into the future with leapfrog vehicle capabilities, including limited roadability, super short 

feld capabilities, and semiautonomous control and navigation. 

Long a dream of frustrated motorists caught up in trafc jams and gridlock, the “fying car” is an 

extremely controversial topic that has been the target of innovators since the early 1920s. Over 70 

individual designs for fying cars have been proposed during past years, with only two achieving 

FAA certifcation and none meeting DoT automotive regulations. In addition to the basic challenges 

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of adequate consumer demand (necessary to lower production costs), the cost of pilot training 

and capability, massive liability issues, the issues of air trafc control, and an extensive number 

of skeptics, the PAV faces signifcant technical challenges. Integrating classical automobile and 

airplane confgurations has so far resulted in unacceptable defciencies and operational capabilities 

from both perspectives. Te resulting vehicle is typically very heavy, slow, oversized, and much 

more expensive than automobiles and aircraft. However, in their eforts to alleviate the current 

and projected limitations of the Nation’s transportation systems, researchers at NASA and industry 

explored new concepts that might be more appropriate for the envisioned missions. 

At Langley, support for PAV studies initially came from seed money provided by NASA Headquarters 

and locally by the previously discussed creativity initiative stimulated by Dennis Bushnell. In 

2003, NASA revamped its aeronautics program and created the NASA Vehicle Systems Program. 

Langley’s Aerospace Vehicle Systems Technology Ofce (AVSTO) was an essential part of the 

Vehicle Systems Program. After extensive workshops with the aerospace community and NASA 

stakeholders were conducted to establish opportunities, goals, and approaches, NASA adopted an 

approach focused on vehicle sectors, including six diferent vehicle thrusts for the future. One such 

thrust was a Personal Air Vehicle Sector, led by Langley’s Mark D. Moore. Moore’s team included 

Andrew S. Hahn (PAV systems analyst), Russell H. Tomas (low-noise concepts), and Kenneth H. 

Goodrich (guidance and control concepts). 

Te overriding perspective of PAV research was that the market for small, single-engine general 

aviation airplanes has reached a plateau for many years and that “disruptive,” revolutionary 

technologies are required to move into an era of aggressive new growth. Te introduction of 

disruptive technologies and regulations into the existing market will change the customers, 

their requirements, and thus the components and vehicles. NASA projected the potential for a 

substantial market for a futuristic PAV that addresses customer preferences with regard to value of 

time, comfort, fexibility, and travel freedom. 

Examples of the benefts of disruptive technology for PAV applications are indicated by comparisons 

with today’s single-engine piston (SEP) airplane. Langley projected 15-year goals that were 

ambitious: the ease of piloting a small aircraft would change from the relative difculty of today’s 

SEP in IFR conditions to more relaxed semiautonomous operations; community and interior cabin 

noise would dramatically decrease to that of the typical automobile; acquisition cost (in 2004 

dollars) would reduce from $300,000 to $100,000; fuel efciency would increase from 13 mpg to 

24 mpg; accidents would be reduced from today’s 6.5 per 100,000 hr to 0.5 per 100,000 hr; and 

feld length requirements would drop from 2,500 ft to about 250 to 500 ft. 

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As part of its PAV sector studies, Langley assessed the benefts of advanced technology for nearterm missions involving rural and regional travel. Typical missions for this class of vehicle include 

a design range of 500 miles with a cruising speed of about 200 mph, a gross weight of about 3,400 

lbs, and with IFR fight capability. With these missions in mind, goals of the research studies were 

to identify concepts to reduce training time and cost, community noise, and purchase price. 

One of the most ambitious, and potentially high-impact, program goals was to identify approaches 

that reduce training time and cost by 90 percent from today’s typical 45-day $10,000 experience 

to only 5 days at a cost of about $1,000. Te technical breakthroughs to obtain this goal are rooted 

in the development, integration, and robustness of fight control systems and architectures that 

are both failsafe and reliable. Technical approaches pursued within the NASA program included 

development of a “naturalistic” fight control deck with control, guidance, sensing, avoidance, and 

an airborne internet. 

Within Mark Moore’s team, Ken Goodrich addressed the challenges of providing feasible approaches 

for automation to make fying small planes easier. Te ultimate research goal was to develop 

vehicle concepts that are inherently “smart” and reduce demands for expertise and capability of the 

human pilot. Goodrich’s eforts were part of a larger Langley project, known as the Autonomous 

Robust Avionics (Aura) project. Led by James R. Burley of the AVSTO, Aura invested in the areas 

of UAVs, PAV, and rotorcraft to enable smart vehicles that reduce the demands on human pilots. 

Goodrich pursued a novel, futuristic approach to autonomous operations known as “H-mode” 

control. While H-mode is short for the technical term haptic, it can also be thought of as “horse 

mode.” Te concept involved is based on the fact that a horse, unlike a car, is more likely to be 

cognizant of obstacles, try to avoid collisions or other threats, and may even know how to fnd 

its way home without inputs from its rider. Likewise, within H-mode, the human pilot and the 

automation system physically “feel” one another’s near-term intent, with intuitive monitoring and 

redirection. Te concept’s development and validation obviously entail detailed studies of sensors, 

system architecture and design, confict detection and resolution, maneuver implementation, 

and failure modes. However, the benefts promised by such an approach would be remarkable, 

yielding a radical reduction in special piloting skills and training, loss of situational awareness, and 

pilot error. 

Another ambitious PAV goal was to identify approaches that reduce community noise generated 

by small aircraft from today’s levels of about 84 dBA at takeof and landing conditions to only 

60 dBA. Technical challenges to obtaining this goal include reducing the community (and cabin) 

noise generated by propulsion systems (propellers, exhausts, etc.) while meeting requirements for 

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vehicle performance, reliability, and cost. Langley studies included the development of integrated 

and shielded ducted propeller systems with active wake control and acoustic suppression. Research 

in this area was led by Russell H. Tomas. 

Progress toward a defnition of the near-term PAV progressed to the point where a notional vehicle, 

known as the TailFan concept, served as a focus for assessing the benefts of advanced technology. 

Te TailFan used an advanced ducted fan for low noise and safety, as well as an automotive engine 

and a dramatically simplifed skin-stifened structure to reduce manufacturing costs. Te TailFan 

resembled current general aviation confgurations in shape; however, it was specifcally designed 

to address the minimum qualifcations of ease, safety, noise, and comfort for PAV applications. 

In addition, it would be economically viable and environmentally friendly, enabling it to compete 

with alternative mobility choices of autos or airlines. 

Notional “TailFan” personal aircraft. 

Te TailFan concept centered about an automotive V-8 engine (nominally the Corvette LS-1 

engine) directly driving a reduced tip-speed ducted fan. Te shorter fan blades generate higher 

frequency noise with the duct shielding absorbing the propulsor noise through embedded acoustical 

liners. Using an automobile engine with extensive mufing involves additional weight compared 

with aircraft engines, as does using a ducted fan compared with using a propeller. However, 

combining the two methods permits a total propulsion system cost reduction of over 60 percent 

while maintaining a reasonable time between overhaul and an extremely quiet integration. 

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Te structure was radically simplifed and designed for automated manufacturing, yielding a 

twelvefold reduction in labor. Use of a highly formed, skin stifened structure reduces total part 

count (labor and inventory costs), while an unusually high degree of symmetry reduces unique 

part count (tooling costs). Te all-aluminum structure uses automotive manufacturing methods 

with an untapered, skin-stifened wing. Te same parts are used for both sides of the wing simply 

by fipping the three spars and using the same four ribs and three skin panels. Rivets or laser 

welds are used in recessed troughs to attach the wing components under a strong polyester flm 

wing covering for smoothness and weather protection. Identical vertical and horizontal tails use 

the same pressing molds for the same skin-stifened construction. An axisymmetric tailcone is 

made with complex curvature, integral frames, and integral stringers pressed into each quarter 

panel. As the external skin is assembled, the internal structure is also assembled. Te fan duct is 

made similarly of four identical sections. Te combination of reduced tooling, assembly labor, and 

propulsion system costs are responsible for the much lower overall cost. 

Tis $100,000 concept solution was based on a 2,000 unit per year production rate to permit 

afordability in the transition market between the current low production general aviation market 

and the high volume production of a future PAV market. Once a substantial market existed, 

and large production volumes are present, many performance compromises could be eliminated 

through investment in a higher tooling-based design and an optimum engine designed specifcally 

for aircraft use. 

Eforts included the demonstration of an LS-1 engine on the 150-hour FAA endurance test. Success 

has shown that it is possible for an automotive engine to perform the aircraft duty cycle. Also, 

NASA worked with the FAA to adapt rules for certifying quality assurance (QA) based products, 

instead of the current FAA certifcation standard of quality control (QC). Te intent of QA-based 

certifcation was not to bypass the FAA’s important role to ensure safety, but to permit certifed 

processes (instead of parts) that enable safer small aircraft products. As long as small aircraft have 

to use specialty, small production volume, QC-based parts, there is little chance of small aircraft 

being afordable to the majority of mobility consumers. 

Future Gridlock Commuter 

While roadable aircraft have been attempted for over 50 years, a more practical dual-mode approach 

might be to require only side-street travel for limited distances in the equivalent of a safe taxi 

mode. Tis capability does not require full compliance with DoT regulations and safety standards. 

Instead, these dual-mode vehicles may meet a minimum set of standards that permit the vehicle 

to achieve a compact taxi mode with very few penalties. By meeting section 500 vehicle standards, 

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these aircraft could travel at 25 mph on side streets, as long as the footprint can be limited to a 

8.5-ft width and meet some additional relatively simple ground travel requirements. Tis mode of 

travel would require the addition of a wheel-drive concept, and although limited roadability does 

not overly penalize the air vehicle, it does involve some additional weight and complexity. 

In Mark Moore’s program, a notional Langley PAV concept known as the Spiral-Duct was conceived 

to combine highly integrated propulsion and aerodynamic lift in a lifting duct arrangement. Te 

inner duct provided lift and thrust, while the outer panels provided control, even at very low 

takeof and landing speeds. Tis vehicle would be capable of takeof and landing in less than 250 

ft. With folded wings, it could travel on the ground at speeds of 25 mph. Able to carry up to two 

passengers, this very compact and quiet vehicle would use an electric propulsion system as efcient 

as current compact cars. 

Notional Spiral Duct Personal Air Vehicle. 

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Te highly integrated propulsion-aerodynamic coupling would enable a 250-ft extreme 

short takeof capability with no external high-lift system moving parts, such as wing faps on 

conventional aircraft, and roll control would be achieved using moving outer wing panels. For the 

ducted propeller arrangement, yaw and pitch control would be enhanced through embedding the 

control surfaces into the propeller fow, and computerized active controls would be used to achieve 

outstanding stability and ease of control. 

In 2004 and 2005 NASA redirected funding within its Vehicle Systems Program and the PAV 

activities at Langley were therefore terminated in 2005. 

National Planning for Next-Generation Air Transportation System 

Inspired to address the shortcomings of the present air system, and the challenges and opportunities 

of the future, the 108th Congress mandated the development of a national plan for the NextGeneration Air Transportation System. Legislation directed that this planning efort include experts 

in commercial aviation, general aviation, aviation labor groups, aviation research and development 

entities, aircraft and air trafc control suppliers, and the space industry. Te parent organization for 

the study was known as the Joint Planning and Development Ofce (JPDO). Within the JPDO 

efort, a Futures Working Group (FWG) of over 150 stakeholders, U.S. Government employees, 

and contractors was formed under the Chairmanship of Langley’s Bruce J. Holmes. 

In May 2004, the FWG presented a set of 11 strategies derived from interviews and scenariobased planning. Due to the wide range of changes in the world situation, economy, and operating 

environment for air transportation envisioned between today and the study target year of 2025, 

the combination of strategies was aimed at transforming air transportation while addressing the 

Nation’s needs in plausible futures that include a tripling (or shrinking) of the demand for air travel, 

fossil fuels becoming less available and more costly, a public that is increasingly concerned with 

the environment, an accelerating pace of production and distribution of goods, radically growing 

importance of international travel and commerce as the world becomes more interdependent, space 

travel becoming a reality, and conventional aircraft sharing the skies with uninhabited air vehicles 

that support safety, security, and national defense. Among the 11 strategies submitted to the JPDO, 

recommendations were made for a national transportation system that streamlines doorstep-todestination travel to provide users with a wide range of options for managing efciencies, costs, 

and uncertainties. In addition, priority was given to design, build, and deploy a network-centric, 

distributed air trafc management system to increase safety, scalability, capacity, efciency, and 

opportunities for free-fight operations. 

Innovation in Flight 317 
PERSONAL AIR TRANSPORTATION CONCEPTS: ON-DEMAND REVOLUTION IN AIR TRAVEL 

Status and Outlook 

Te highly successful demonstration of SATS technology in June 2005 was a critical milestone 

in NASA’s vision of the future for small aircraft in air transportation. If, as hoped, the potential 

of advanced technology to open up the Nation’s underused public airports is appreciated by the 

appropriate industrial, regulatory, and technical communities, there is no doubt that entrepreneurial 

interests will lead to a new generation of air-taxi capabilities. 

Te termination of NASA research on advanced PAV concepts in 2005 virtually eliminated Langley 

interest in this class of vehicle. Skeptics of the vision remain steadfast, and further maturation of 

the technical innovations that would enable such a revolutionary change in public transportation 

will require extensive, dedicated research eforts capped by convincing demonstrations of the 

technology’s benefts. 

318 Innovation in Flight 
The Future of Innovation: Priming the Pump 

Te remarkable changes in culture and resources that have occurred at Langley as it approaches 

its ninetieth year in 2007 have shaped, encouraged, and infuenced the Center’s ability to identify 

and assess revolutionary concepts. In its earlier history as an NACA laboratory, the staf enjoyed a 

technical atmosphere characterized by immaturity in aeronautical science and technology, limited 

expertise and availability of facilities in industry, and took a major role in the shaping of aeronautics, 

the aviation industry, and national defense. Freedom to conduct research on new concepts was 

widespread, a rich environment of technical challenges stimulated the researcher, and the technical 

state of the art in aeronautics accelerated at a breath-taking rate. Te legendary contributions of 

NACA and Langley stand as evidence of the innovation and dedication that pervaded the Center 

in that era. 

With the coming of the Space Age and the evolution of NASA Centers, the role of Langley greatly 

expanded, and its focus broadened to include support activities for NASA’s space program and new 

areas of concern to the Nation, such as atmospheric science. Budgetary issues rose to new levels 

as the Apollo Program and ensuing space exploration activities began to have an impact on the 

ability of researchers to conduct studies on revolutionary concepts that strayed markedly from the 

evolutionary. Aeronautics programs within NASA also became more focused on near-term goals, 

in part to pacify NASA’s stakeholders and Congress, who wanted near-term payof and highly 

focused activities. In more recent years, the aviation industry has put its own unique wind tunnels, 

laboratories, and computational centers into operation, with capabilities as good as, or exceeding, 

NASA’s aging facilities. Foreign technology, facilities, and advanced aircraft are now keeping pace 

with, or surpassing, the aeronautical leadership of the United States. Finally, aeronautics itself has 

become a self-professed/self-fulflling prophecy. Tat is, the world of aeronautics has become–– 

according to Dennis Bushnell—“An asymptotic, barely evolutionary, mature science with only 

capacity, safety, and environmental issues.” Te reality of this perspective has led many to refer to 

aeronautics as a “sunset” technical area without excitement or fresh ideas. 

Management at the NASA aeronautical centers (Langley, Ames, Glenn, and Dryden) recognized 

the constraints being placed on innovation and proceeded to implement new funding sources, 

known as the Center Director’s Discretionary Fund (CDDF), as incubator mechanisms for fresh 

ideas. By providing resource and management support for selected eforts, the Centers protected 

and encouraged the potential for revolutionary studies. Specifc advanced studies were judged and 

funded on a competitive basis with the participation of top management. 

In 2001, Langley management reacted to a scenario wherein the Center’s programs had become 

increasingly tightly controlled and out-of-the-box thinking and opportunities were becoming 

alarming constrained. Center Director Jeremiah F. Creedon and Associate Director for Research 

Innovation in Flight 319 
THE FUTURE OF INNOVATION: PRIMING THE PUMP 

and Technology Competencies Douglas L. Dwoyer inaugurated a new program, known as the 

Creativity and Innovation (C&I) Initiative, to augment the existing CDDF resources and provide 

a competed opportunity for researchers to acquire a maximum amount of $300,000 per year 

for advanced ideas. Te funding provides for research equipment, salaries, and travel, and an 

opportunity to impact the future of aeronautics and space technology. Te program evolved from 

the mutual interests and advocacy of several senior managers, including Dennis M. Bushnell and 

Joseph Heyman. Heyman was the frst manager of the C&I activity, later followed by Bushnell. 

Te C&I Initiative covers all technical elements of Langley’s mission: aeronautics, atmospheric 

science, access to space, planetary and space exploration, and systems studies. Te program 

stimulates and nurtures advanced ideas with minimal management and oversight. Proposals from 

Langley stafers are evaluated by a group of technical peers on the basis of technical content, 

inventive/creative content, and researcher capability. 

Results of the C&I activity have been remarkably positive. Within the area of aeronautics, 

some topics receiving support have been: neural network fight controller, runway topography 

characterization, unconventional aircraft confgurations, breakthrough noise suppression concepts, 

distributed propulsion, and circulation control/channel wing concepts. 

Current Langley Director Roy D. Bridges, Jr., has embraced the spirit of the C&I Initiative, and 

the program has continued to thrive as a visible sign of the value placed on innovative ideas by 

management. Te research community has taken notice and responded in excitement and interest, 

sparking continued growth of the legacy of Langley’s contributions in advanced research. 

In September 2004 Bridges announced a new Langley organizational structure which included a 

new element known as the Incubator Institute. Led by Richard R. Antclif, the institute’s mission 

is to stimulate new business and leading-edge research eforts for the Center. Antclif’s staf 

includes Dennis Bushnell (Chief Scientist), Mark J. Shuart (Associate Director for Transformation 

Projects). Te name of the organization was subsequently changed to Innovation Institute to 

refect its mission as a catalyst for fresh concepts and ideas. Antclif and his staf face a daunting 

challenge in promoting and nurturing innovation during a chaotic atmosphere of change within 

the Agency’s aeronautics program. Sweeping cultural and operational transitions are now occurring 

at Langley resulting in closure of many wind tunnels, severe reductions in funding for aeronautical 

research, and reductions in workforce. In addition, the fundamental method of securing resources 

for research is changing to a business mode of operation featuring competitive proposals and peerreviewed awards for studies. 

320 Innovation in Flight 
THE FUTURE OF INNOVATION: PRIMING THE PUMP 

As Langley strives to align itself with the major thrusts and missions of the Agency, the benefactors 

of its leading-edge expertise and unique capabilities look forward to a continuation of this critical 

national asset and to the future U.S. leadership in aviation and aerospace technology. 

Innovation in Flight 321 

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Conway, Erik M.: High-Speed Dreams: NASA and the Technopolitics of Supersonic Transportation, 

1945–1999. Johns Hopkins University Press, 2005. 

Darden, C. M., Clemans, A., Hayes, W. D., George, A. R., and Pierce, A. D.: Status of Sonic Boom 

Methodology and Understanding. NASA CR-3027, 1988. 

Darden, C. M.: Sonic Boom Minimization With Nose Bluntness Relaxation. NASA TP 1348, 1979. 

Darden, Christine M.: High-Speed Research: Sonic Boom. NASA CP-3172, 1992. 

Darden, Christine M.; Powell, Clemans A.; Hayes, Wallace D.; George, Albert R.; and Pierce, Allan 

D.: Status of Sonic Boom Methodology and Understanding. NASA CP-3027, 1988. 

Doggett, R. V., Jr.; and Townsend, J. L.: Flutter Suppression by Active Control and Its Benefts. 

Proceedings of the SCAR Conference, NASA CP-001, Part 1, 1976, pp. 303-333. 

Driver, C., and Maglieri, D. J.: Some Unique Characteristics of Supersonic Cruise Vehicles and Teir 

Efect on Airport Community Noise. AIAA Paper 80-0859, May 1980. 

Driver, C.: Progress in Supersonic Cruise Technology. AIAA Paper 81-1687, August 1981. 

Driver, Cornelius; Spearman, Leroy M.; and Corlett, William A.: Aerodynamic Characteristics at 

Mach Numbers from 1.61 to 2.86 of a Supersonic Transport Model with a Blended Wing-Body, 

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Innovation in Flight 325 
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Freeman, D. C., Jr.: Low-Subsonic Longitudinal Aerodynamic Characteristics in the Deep-Stall AngleOf-Attack Range of a Supersonic Transport Confguration With a Highly Swept Arrow Wing. NASA 

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Freeman, Delma C., Jr.: Low Subsonic Flight and Force Investigation of a Supersonic Transport Model 

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Grantham, William D., and Deal, Perry L.: A Piloted Fixed-Based Simulator Study of Low-Speed 

Flight Characteristics of an Arrow-Wing Supersonic Transport Design. NASA TN D-4277, 1968. 

Grantham, William D., Nguyen, Luat T., Deal, Perry L., Neubauer, M. J. Jr., Smith, Paul M., and 

Gregory, Frederick D.: Ground-Based and In-Flight Simulator Studies of Low-Speed Handling 

Characteristics of Two Supersonic Cruise Transport Concepts. NASA Technical Paper 1240, 1978. 

Haering, Edward A., Jr.; Ehernberger, L. J.; and Whitmore, Stephen A.: Preliminary Airborne 

Measurements for the SR-71 Sonic Boom Propagation Experiment. NASA TM 104307, 1995. 

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Sonic Boom Workshop. Confguration, Design, Analysis and Testing, NASA/CP-1999-209699, 1999 

Haering, Edward A., Jr.; Murray, James E.; Purifoy, Dana D.; Graham, David H.; Meredith, Keith 

B.; Ashburn, Christopher E.; and Stucky, Mark: Airborne Shaped Sonic Boom Demonstration 

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Hansen, James R.: Engineer in Charge. NASA SP-4305, 1987. 

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Harris, R. V., Jr.: A Numerical Technique for Analysis of Wave Drag at Lifting Conditions. NASA-TND-3586, 1966. 

Harris, R. V., Jr.: An Analysis and Correlation of Aircraft Wave Drag. NASA TM X-947, 1964. 

Heimerl, George J., and Hardrath, Herbert F.: An Assessment of a Titanium Alloy for Supersonic 

Transport Operations. Presented at the Conference on Aircraft Operating Problems, NASA 

Langley Research Center, May 10-12, 1965. (Paper 23 of NASA SP-83). 

Henderson, W. P.: Selected Results from a Low-Speed Investigation of the Aerodynamic Characteristics of 

a Supersonic Transport Confguration Having an Outboard Pivot Variable Sweep Wing. NASA TM 

X-839, 1963. 

Hergenrother, Paul M.: Development of Composites, Adhesives and Sealants for High-Speed Commercial 

Airplanes. SAMPE Journal 36:1 (January/February 2000), pp. 30-41 

Hilton, David A., Huckel, Vera, Steiner, Roy, and Maglieri, Domenic J.: Sonic-Boom Exposures 

During FAA Community-Response Studies Over a 6-Month Period in the Oklahoma City Area. 

NASA TN D-2539, 1964. 

Hilton, David A.; Huckel, Vera; and Maglieri, Domenic J.: Sonic-Boom Measurements During 

Bomber Training in the Chicago Area. NASA TN D-3655, 1966. 

Hofman, S.: Bibliography of Supersonic Cruise Research (SCR) Program from 1977 to Mid-1980. 

NASA-RP-1063, 1980. 

Hofman, S.: Bibliography of Supersonic Cruise Aircraft Research (SCAR) Program from 1972 to Mid1977. NASA RP-1003, 1977. 

Hortwich, M.: Clipped Wings–Te American SST Confict. Te MIT Press, Cambridge, 

Massachusetts, 1982. 

Houbolt, J. C., “Why Twin Fuselage Aircraft?” Astronautics and Aeronautics, April 1982, pp. 26-35. 

Hubbard, Harvey H., Maglieri, Domenic J., Huckel, Vera, and Hilton, David A.: Ground 

Measurements of Sonic-Boom Pressures for the Altitude Range of 10,000 to 75,000 Feet. NASA 

TR R-198, 1964. 

Jackson, E. Bruce, Raney, David L., Glaab, Louis J., and Derry, Stephen L.: Piloted Simulation 

Assessment of a High-Speed Civil Transport Confguration. NASA TP-2002-211441, 2002. 

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Johnson, Joseph L., Jr.: Wind-Tunnel Investigation of Low-Subsonic Flight Characteristics of a Model of 

a Canard Airplane Designed for Supersonic Cruise Flight. NASA TM X-229, 1960. 

Kelly, T. C., Patterson, J. C., Jr., and Whitcomb, R. T.: An Investigation of the Subsonic, Transonic, 

and Supersonic Aerodynamic Characteristics of a Proposed Arrow-Wing Transport Airplane 

Confguration. NASA TM X-800, 1963. 

Leatherwood, J. D., and Sullivan, Brenda M.: Laboratory Studies of Efects of Boom Shaping on 

Subjective Loudness and Acceptability. NASA TP-3269, 1992. 

Mack, R. J., and Darden, C. M.: A Wind-Tunnel Investigation of the Validity of a Sonic Boom 

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Mack, Robert J.: A Supersonic Business-Jet Concept Designed for Low Sonic Boom. NASA TM-2003-

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Clark, Lorenzo R.; and Gerhold, Carl H.: Inlet Noise Reduction By Shielding for the BlendedWing-Body Airplane. AIAA Paper 99-1937, 1999. 

Giles, Gary L.: Equivalent Plate Modeling for Conceptual Design of Aircraft Wing Structures. 

AIAA Paper No. 95-3945, 1995. 

Hilburger, M. W.; Rose, C. A.; and Starnes, J. H. Jr.: Nonlinear Analysis and Scaling Laws for 

Noncircular Composite Structures Subjected to Combined Loads. AIAA 2001-1335, 2001. 

Liebeck, R.: Design of the Blended-Wing-Body Subsonic Transport, AIAA Paper No. 2002-0002, 

2002. 

Liebeck, Robert, H.; Page, Mark, A.; Rawdon, Blaine K.; Scott, Paul W.; and Wright Robert A.: 

Concepts for Advanced Subsonic Transports. NASA CR-4624, 1994. 

Mukhopadhyay, V.; Sobieszczanski-Sobieski, J.; Kosaka, I; Quinn, G.; and Charpentier, C.: 

Analysis Design and Optimization of Non-cylindrical Fuselage for Blended-Wing-Body (BWB) 

Vehicle. AIAA Paper 2002-5664, 2002. 

332 Innovation in Flight 
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Mukhopadhyay, Vivek: Interactive Flutter Analysis and Parametric Study for Conceptual Wing 

Design. AIAA Paper 95-3943, 1995. 

Mukhopadhyay, Vivek: Structural Concepts Study of Non-Circular Fuselage Confgurations. Paper 

No. WAC-67. Presented at the SAE/AIAA World Aviation Congress, October 22-24, 1996. 

Potsdam, Mark A.; Page, Mark A.; and Liebeck, Robert H.: Blended Wing Body Analysis and 

Design. AIAA Paper 97-2317, 1997. 

Roman, D.; Allen, J. B.; and Liebeck, R. H. : Aerodynamic Design Challenges of the BlendedWing-Body Subsonic Transport. AIAA Paper No. 2000-4335, 2000. 

Spellman, Regina L.: Analysis and Test Correlation of Proof of Concept Box for Blended Wing 

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Te Boeing Company, Long Beach, CA.: Blended-Wing-Body Technology Study. NAS1-20275 Final 

Report, prepared for NASA-Langley Research Center, October 30, 1997. 

Tigner, Benjamin; Meyer, Mark J.; Holdent, Michael E.; Rawdon, Blaine K.; Page, Mark A.; 

Watson, William; and Kroo, Ilan: Test Techniques For Small-Scale Research Aircraft, AIAA 

Paper No. 98-2726, 1998. 

Vicroy, Dan D.: NASA’s Research on the Blended-Wing-Body Confguration. Presented at World 

Aviation Congress, October 10, 2000, San Diego, CA. 

Wahls, R. A.: Te National Transonic Facility: A Research Retrospective. AIAA 2001-0754, 2001. 

Watkins, A. Neal, et.al.: Flow Visualization at Cryogenic Conditions Using a Modifed Pressure 

Sensitive Paint Approach. AIAA Paper 2005-0456, 2005. 

Synthetic Vision 

Adams, J. J.: Simulator Study of Pilot-Aircraft-Display System Response Obtained With a TreeDimensional-Box Pictorial Display. NASA NASA-TP-2122 , 1983. 

Avionic Pictorial Tunnel-/Pathway-/Highway-In-Te-Sky Workshops. Russell V. Parrish, Compiler. 

NASA/CP-2003-212164, March, 2003. 

Bailey, Randall E.; Parrish, Russell V.; Kramer, Lynda J.; Harrah, Steve D.; and Arthur, J. J., III 

: Technical Challenges in the Development of a NASA Synthetic Vision System Concept. 

Presented at NATO RTO Enhanced and Synthetic Vision Systems, Ottawa, Canada, September 

9-12, 2002. 

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Glaab, Louis J.; and Hughes, Monica F.;: Terrain Portrayal for Head-Down Displays Flight Test. 

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Glaab, Louis J.; and Takallu, Mohammad A.: Preliminary Efect of Synthetic Vision Systems 

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Presented at the 2002 SAE General Aviation Technology Conference & Exhibition, Wichita, 

Kansas, April 16-18, 2002. 

Harrison, Stella V.; Kramer, Lynda J.; Bailey, Randall E.; Jones, Denise R.; Young, Steven D.; 

Harrah, Steven D.; Arthur, Jarvis J.; and Parrish, Russell V.: Initial SVS Integrated Technology 

Evaluation Flight Test Requirements and Hardware Architecture . NASA/TM-2003-212644, 2003. 

Jones, Denise R.: Runway Incursion Prevention System Simulation Evaluation. Proceedings of the 

21st Digital Avionics Systems Conference, Irvine, CA, Oct. 27 – 31, 2002. 

Jones, Denise R.; Quach, Cuong C.; and Young, Steven D.: Runway Incursion Prevention System 

– Demonstration and Testing at the Dallas/Fort Worth International Airport. Proceedings of 

the 20th Digital Avionics Systems Conference, Daytona Beach, FL, Oct. 14 – 18, 2001. 

Kramer, Lynda J.; Prinzel, Lawrence J., III; Arthur, Jarvis J.; and Bailey, Randall E.: Pathway 

Design Efects on Synthetic Vision Head-Up Displays. Presented at SPIE Defense & Security 

Symposium 2004, Orlando, Florida, April 12-16, 2004. 

Kramer, Lynda J.; Prinzel, Lawrence J., III; Bailey, Randall E.; Arthur, Jarvis J.: Synthetic Vision 

Enhances Situation Awareness and RNP Capabilities for Terrain-Challenged Approaches. AIAA 

Paper 2003-6814, 2003. 

Kramer, Lynda J.; Prinzel, Lawrence J., III; Bailey, Randall E.; Arthur, Jarvis J.; and Parrish, Russell 

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Parrish, Robert V.; Busquets, Anthony M.; Williams, Steven P.; and Nold, Dean E.: Evaluation of 

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Prinzel, Lawrence J., III; Hughes, Monica F.; Arthur, Jarvis J.; Kramer, Lynda J.; Glaab, Louis 

J.; Bailey, Randall E.; Parrish, Russell V.; and Uenking, Michael D.: Synthetic Vision CFIT 

Experiments for GA and Commercial Aircraft: A Picture is Worth a Tousand Lives. Presented 

at the Human Factors and Ergonomics Society 47th Annual Meeting, Denver, Colorado, 

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334 Innovation in Flight 
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Scott, William B.: Clearing the Fog. Aviation Week and Space Technology, August 9, 2004. pp 48-51. 

Synthetic Vision Workshop 2. Lynda J. Kramer, Compiler. NASA/CP-1999-209112, March 1999. 

Uijt De Haag, M., Young, S., and Gray, R.: A Performance Evaluation of Elevation Database 

Integrity Monitors for Synthetic Vision Systems. 8th International Conference on Integrated 

Navigation Systems, Saint Petersburg, Russia, May 28-30, 2001 

Young, S., and Jones, D.: Flight Testing of an Airport Surface Movement Guidance, Navigation, 

and Control System. Proceedings of the Institute of Navigation’s National Technical Meeting, 

January 21-23, 1998. 

Young, S., and Jones, D.: Runway Incursion Prevention: A Technology Solution. Proceedings of 

the Joint Meeting of the Flight Safety Foundation’s 54th Annual International Air Safety 

Seminar, the International Federation of Airworthiness’ 31st International Conference, and the 

International Air Transport Association, Athens, Greece, November 5-8, 2001. 

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Aerospace America, May 1998. 

Laminar Flow Control 

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Flow Control Experiment Conducted in NASA Langley 8-Foot Transonic Pressure Tunnel. NASA 

TP-3549, 1996. 

Braslow, A.L.; Maddalon, D. V.; Bartlett, D. W.; Wagner, R. D.; and Collier, F. S., Jr.: Applied 

Aspects of Laminar-Flow Technology. Viscous Drag Reduction in Boundary Layers, Dennis M. 

Bushnell and Jerry Hefner, eds., AIAA, pp. 47–78, 1990. 

Braslow, Albert L.: A History of Suction-Type Laminar-Flow Control with Emphasis on Flight Research. 

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Braslow, Albert L.; Burrows, Dale L.; Tetervin, Neal; and Visconti, Fioravante: Experimental and 

Teoretical Studies of Area Suction for the Control of the Laminar Boundary Layer on an NACA 

64A010 Airfoil. NACA Rep. 1025, 1951. 

Bushnell, D. M.; and Malik, M. R.: Supersonic Laminar Flow Control. Research in Natural Laminar 

Flow and Laminar-Flow Control, Jerry N. Hefner and Frances E. Sabo, compilers, NASA CP2487, Part 3, pp. 923–946. 1987. 

Bushnell, Dennis M.; and Tuttle, Mary H.: Survey and Bibliography on Attainment of Laminar Flow 

Control in Air Using Pressure Gradient and Suction. NASA RP-1035, 1979. 

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AIAA-93-2987, 1993. 

Harris, Roy V., Jr.; and Hefner, Jerry N.: NASA Laminar-Flow Program—Past, Present, Future. 

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Sabo, compilers, NASA CP-2487, Part 1, pp. 1–23. 1987. 

Hastings, Earl C.: Status Report on a Natural Laminar-Flow Nacelle Flight Experiment. Research 

in Natural Laminar Flow and Laminar-Flow Control, Jerry N. Hefner and Frances E. Sabo, 

compilers, NASA CP-2487, Part 3, pp. 887–890. 1987. 

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1992. 

Joslin, Ronald D.: Overview of Laminar Flow Control. NASA TP-1998-208705, 1998. 

Lynch, Frank K.; and Klinge, Mark D.: Some Practical Aspects of Viscous Drag Reduction Concepts. 

SAE Paper 912129, 1991. 

Maddalon, D. V.; Collier, F. S., Jr.; Montoya, L. C.; and Land, C. K.: Transition Flight Experiments 

on a Swept Wing With Suction. AIAA Paper No. 89-1893, 1989. 

Runyan, L. J.; Bielak, G. W.; Behbehani, R.; Chen, A. W.; and Rozendaal, R. A.: 757 NLF Glove 

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336 Innovation in Flight 
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Tuttle, Mary H.; and Maddalon, Dal V.: Laminar Flow Control (1976-1991)–A Comprehensive, 

Annotated Bibliography. NASA TM 107749, 1993. 

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Prospects. AIAA-89-0989, 1989. 

Wagner, R. D.; Fischer, M. C.; Collier, F. S., Jr.; and Pfenninger, W.: Supersonic Laminar Flow 

Control on Commercial Transports. 17th Congress of the International Council of the 

Aeronautical Sciences, ICAS Proceedings, 1990. 

Wagner, R. D.; Maddalon, D. V.; and Fisher, D. F.: Laminar Flow Control Leading-Edge Systems 

in Simulated Airline Service. Journal of Aircraft, Vol. 27, No. 3, March 1990, pp 239-244. 

Wagner, R. D.; Maddalon, D. V.; Bartlett, D. W.; and Collier, F. S., Jr.: Fifty Years of Laminar Flow 

Flight Testing. SAE Paper 881393, 1988. 

Wagner, R. D.; Maddalon, Dal V.; Collier, F.S.; and Braslow, A. L.: Laminar Flow Flight 

Experiments. Presented at Transonic Symposium: Teory, Application, and Experiment held at 

Langley Research Center. NASA CP 3020, 1988. 

Wie, Y. S.; Collier, F. S., Jr.; Wagner, R. D.; Viken, J. K.; and Pfeninnger, W.: Design of a Hybrid 

Laminar Flow Control Engine Nacelle. AIAA-92-0400, 1992. 

Wilkinson, Stephan: “Go With the Flow”. Air & Space/Smithsonian Magazine, June/July, 1995. 

Zalovcik, John A.; Wetmore, J. W.; and Von Doenhof, Albert E.: Flight Investigation of BoundaryLayer Control by Suction Slots on an NACA 35-215 Low-Drag Airfoil at High Reynolds Numbers. 

NACA WR L-521. 1944 (Formerly NACA ACR 4B29.) 

Upper-Surface Blowing 

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of Development and Validation of Aeronautical Technology. NASA SP-1998-3300, 1998. 

Cochrane, J.A. and Riddle, D.W.: Quiet Short-Haul Research Aircraft-Te First Tree Years of 

Flight Research. AIAA Paper 81-2625, 1981. 

Collection of Papers from the AIAA 2002 Biennial International Powered Lift Conference and 

Exhibit. Williamsburg, Virginia, November 5-7, 2002. 

Deckert, W. H.; and Franklin, J. A.: Powered-Lift Aircraft Technology. NASA SP-501, 1989. 

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Hassell, James L., Jr.: Results of Static Test of a 1⁄4-Scale Model of the Boeing YC-14 Powered-Lift System. 

NASA Conference on Powered-Lift Aerodynamics and Acoustics. May 24-26, 1976. 

Johnson, Joseph L., Jr.; and Phelps, Arthur E., III: Low-Speed Aerodynamics of the Upper-Surface 

Blown Jet Flap. Society of Automotive Engineers Air Transportation Meeting; Dallas, TX. April 

30-May 2, 1974. 

Maglieri, D. J.; and Hubbard H. H.: Preliminary Measurements of the Noise Characteristics of Some 

Jet-Augmented-Flap Confgurations. NASA Memo 12-4-58L, 1959. 

Phelps, A. E., III; Johnson, J. L., Jr.; and Margason, R. J.: Summary of Low-Speed Aerodynamic 

Characteristics of Upper-Surface-Blown Jet-Flap Confgurations. NASA Conference on PoweredLift Aerodynamics and Acoustics. May 24-26, 1976. 

Phelps, Arthur E., III,: Wind-Tunnel Investigation of a Twin-Engine Straight-Wing Upper-Surface 

Blown Jet-Flap Confguration. NASA TN D-7778, 1975. 

Phelps, Arthur E.; Letko, William; and Henderson, Robert L.: Low-Speed Wind-Tunnel Investigation 

of a Semispan STOL Jet Transport Wing-Body with an Upper-Surface Blown Jet Flap. NASA TN 

D-7183, 1973. 

Powered-Lift Aerodynamics and Acoustics. Conference held at Langley Research Center, Hampton, 

VA, NASA CP-406, May 24-26, 1976. 

Riddle, Dennis W.; Stevens, Victor C.; and Eppel, Joseph C.: Quiet Short-Haul Research Aircraft: A 

Summary of Flight Research Since 1981. SAE Technical Paper 872315, Dec. 1987. 

Shivers, James P.; and Smith, Charles C., Jr.: Static Test of a Simulated Upper Surface Blown Jet-Flap 

Confguration Utilizing a Full-Size Turbofan Engine. NASA TN D-7816, 1975. 

Sleeman, William C., Jr.: Low-Speed Wind-Tunnel Investigation of a Four-Engine Upper Surface Blown 

Model Having a Swept Wing and Rectangular and D-Shaped Exhaust Nozzles. NASA TN D8061, 1975. 

Smith, Charles C., Jr.; Phelps, Arthur E., III; and Copeland, W. Latham: Wind-Tunnel Investigation 

of a Large-Scale Semispan Model with an Unswept Wing and Upper-Surface Blown Jet Flap. NASA 

TM D-7526, 1974. 

Staf of the Langley Research Center: Wind-Tunnel investigation of the Aerodynamic Performance, 

Steady and Vibratory Loads, Surface Temperatures and Acoustic Characteristics of a Large-Scale 

Twin-Engine Upper-Surface Blown Jet-Flap Confguration. NASA TM X-72794, 1975. 

338 Innovation in Flight 
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Tomas, J. L.; Hassell, J. L., Jr; and Nguyen, L. T.: Aerodynamic Characteristics in Ground Proximity. 

NASA Conference on Powered-Lift Aerodynamics and Acoustics. May 24-26, 1976. 

Turner, T. R.; Davenport, E. E.; and Riebe, J. M.: Low-Speed Investigation of Blowing From Nacelles 

Mounted Inboard and on the Upper Surface of an Aspect Ratio 7.0 35° Swept Wing With Fuselage 

and Various Tail Arrangements. NASA Memo 5-1-59L, 1959. 

Wimpress, John K.; and Newberry, Conrad F.: Te YC-14 STOL Prototype: Its Design, 

Development, and Flight Test. AIAA Case Study Series, 1998. 

Zuk, John; Callaway, Robert K.; and Wardwell, Douglas A.: Adaptive Air Transportation System-a 

Catalyst for Change. AIAA Paper 2002-5956, 2002. 

Control of Aeroelastic Response 

Abel, I.: Research and Applications in Aeroelasticity and Structural Dynamics at the NASA Langley 

Research Center. NASA TM-112852, 1997. 

Abel, I.; and Sandford, Maynard C.: Status of Two Studies on Active Control of Aeroelastic Response. 

NASA TM X-2909, 1973. 

Abel, I.; Doggett, R. V.; Newsom, J. R.; and Sandford, M.: Dynamic Wind-Tunnel Testing of Active 

Controls by the NASA Langley Research Center. AGARD Ground and Flight Testing for Aircraft 

Guidance and Control; December 1984. 

Abel, I.; Perry, B., III; and Newsom, J. R.: Comparison of Analytical and Wind-Tunnel Results for 

Flutter and Gust Response of a Transport Wing with Active Controls. NASA TP-2010, 1982. 

Bennett. R. M.; Eckstrom, C. V.; Rivera, J. A., Jr.; Dansberry, B. E.; Farmer, M. G.; and Durham, 

M. H.: Te Benchmark Aeroelastic Models Program-Description and Highlights of Initial Results. 

NASA TM-104180, 1991. 

Cazier, F. W., Jr.; and Kehoe, M. W.: Flight Test of a Decoupler Pylon for Wing/Store Flutter 

Suppression. AIAA Paper 86-9730, 1986. 

Chambers, Joseph R.: Concept to Reality: Contributions of the NASA Langley Research Center to U.S. 

Civil Aircraft of the 1990’s. NASA SP-2003-4529, 2003. 

Chambers, Joseph R.: Partners in Freedom: Contributions of the NASA Langley Research Center to U.S. 

Military Aircraft of the 1990’s. NASA SP-2000-4519, 2000. 

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Doggett, R.V., Jr.; Abel, I; and Ruhlin, C. L.: Some Experiences Using Wind-Tunnel Models in Active 

Control Studies. Presented at the Symposium on Advanced Control Technology and Its Potential 

for Future Transport Aircraft. NASA TM X-3409, 1976, pp. 831-892. 

Ethell, Jefrey L.: Fuel Economy in Aviation. NASA SP-462, 1983 

Foughner, J. T. Jr.; and Besinger, C. T.: F-16 Flutter Model Studies of External Wing Stores. NASA 

TM-74078, 1977. 

Galea, S. C.; Ryall T. G.; Henderson, D. A.; Moses, R. W.; White, E. V.; and Zimcik, D. G.: Next 

Generation Active Bufet Suppression System. AIAA Paper 2003-2905, 2003. 

Goodman, Charles; Hood, Mark; Reichenbach, Eric; and Yurkovich, Rudy: An Analysis of the F/A18C/D Limit Cycle Oscillation Solution. AIAA Paper 2003-1424, 2003. 

Heeg, J.: Analytical and Experimental Investigation of Flutter Suppression by Piezoelectric Actuation. 

NASA TP-3241, 1993. 

Heeg, J.: Flutter Suppression via Piezoelectric Actuation. NASA TM 104120, 1991. 

Hood, R. V., Jr.: Te Aircraft Energy Efciency Active Controls Technology Program. AIAA Paper 

77-1076, 1977. 

McGowan, A-M. R.; Heeg, J.; and Lake, R. C.: Results from Wind-Tunnel Testing from the 

Piezoelectric Aeroelastic Response Tailoring Investigation. AIAA Paper 96-1511, April 1996. 

Middleton; D. B.; Bartlett, D. W.; and Hood, R. V., Jr.: Energy Efcient Transport Technology: 

Program Summary and Bibliography. NASA RP-1135, 1985. 

Moses, R. W.: NASA Langley Research Center’s Contributions To International Active Bufeting 

Alleviation Programs. Presented at the NATO-RTO Workshop on Structural Aspects of Flexible 

Aircraft Control, Ottawa, Canada, October 18-21, 1999. 

Moses, R. W.: Vertical Tail Bufeting Alleviation Using Piezoelectric Actuators – Some Results of the 

Actively Controlled Response of Bufet-Afected Tails (ACROBAT) Program. Presented at SPIE’s 4th 

Annual Symposium on Smart Structures and Materials, Industrial and Commercial Applications 

of Smart Structures Technologies, Conference 3044, March 4-6, 1997, San Diego, CA. 

Moses, R. W.; and Huttsell, L.: Fin Bufeting Features of an Early F-22 Model. AIAA Paper 2000-

1695, 2000. 

340 Innovation in Flight 
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Moses, R. W.; and Pendleton, E.: A Comparison of Pressure Measurements Between a Full-Scale and a 

1/6-Scale F/A-18 Twin Tail During Bufet. NASA TM-110282, 1996. 

Mukhopadhyay, V.: Transonic Flutter Suppression Control Law Design, Analysis and Wind-Tunnel 

Results. Paper presented at the International Forum on Aeroelasticity and Structural Dynamics 

1999, Williamsburg, VA, June 22-25, 1999. 

Murrow, H. N.; and Eckstrom, C. V.: Drones for Aerodynamic and Structural Testing (DAST). A 

Status Report. AIAA Journal of Aircraft, Vol. 16, No. 8, August 1979, pp. 521-526. 

Nissim, E: Design of Control Laws for Flutter Suppression Based on the Aerodynamic Energy 

Concept and Comparisons with Other Design Methods. AIAA Paper 89-1212, 1989. 

Perry, B. P., III; Cole, S. R.; and Miller, G. D.: A Summary of the Active Flexible Wing Program. 

NASA TM-107655, 1992. 

Perry, B. P., III; Mukhopadhyay, V.; Hoadley, S. T.; Cole, S. R.; Buttrill, C. S.; and Houck, J. A.: 

Digital-Flutter-Suppression-Investigations for the Active Flexible Wing Wind-Tunnel Model. NASA 

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Perry, Boyd, III; Noll, Tomas E.; and Scott, Robert C.: Contributions of the Transonic Dynamics 

Tunnel to the Testing of Active Control of Aeroelastic Response. AIAA Paper 2000-1769, 2000. 

Phillips, W. H.; and Kraft, C. C., Jr.: Teoretical Study of Some Methods for Increasing the Smoothness 

of Flight Trough Rough Air. NACA TN 416, 1951. 

Pinkerton, J. L.; McGowan, A-M R.; Moses, R. W.; Scott, R. C.; and Heeg, J.: Controlled Aeroelastic 

Response and Airfoil Shaping Using Adaptive Materials and Integrated Systems. Paper Presented at 

the SPIE 1996 Symposium on Smart Structures and Integrated Systems. San Diego, California, 

February 26-29, 1996. 

Redd, L. T.; Gilman, J., Jr.; and Cooley, D. E.: A Wind-Tunnel Investigation of a B-52 Model Flutter 

Suppression System. Journal of Aircraft, Vol. II, No. 11. Nov. 1074, pp. 659-663 

Redd, L. T.; Hanson, P. W.; and Wynne, E. C.: Evaluation of a Wind-Tunnel Gust Response 

Technique Including Correlations With Analytical and Flight Test Results. NASA-TP-1501, 1979. 

Reed, Wilmer H. III , and Abbott, F.T., Jr.: A New “Free-Flight” Mount System for High-Speed Wind 

Tunnel Flutter Models. Proceedings of Symposium on Aeroelastic and Dynamic Modeling 

Technology. RT-TDR-66-4197, Pt.1, U.S. Air Force. March 1964, pp.169-206. 

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Reed, Wilmer H., III; Foughner, Jerome P., Jr.; and Runyan, Harry L., Jr.: Decoupler Pylon: A 

Simple, Efective Wing/Store Flutter Suppressor. Journal of Aircraft, Vol. 17, No. 3, March 1980, 

pp. 206-211. 

Sandford, M. C.; Abel, I.; and Gray, D. L.: Development and Demonstration of a Flutter Suppression 

System Using Active Controls. NASA-TR-R-450, 1975. 

Scott, R. C.; Wieseman, C. D.; Hoadley, S.T.; and Durham, M.H.: Pressure and Loads 

Measurements on the Benchmark Active Controls Technology Model. AIAA Paper 97-0829, 

1997. 

Sheta, E. F.; Moses, R. W.; Huttsell, L. J.; and Harrand, V. J.: Active Control of F/A-18 Vertical 

Tail Bufeting Using Piezoelectric Actuators. AIAA Paper 2003-1887, 2003. 

Stewart, E. C.; and Redd, L. T.: A Comparison of the Results of Dynamic Wind-Tunnel Tests with 

Teoretical Predictions for an Aeromechanical Gust-Alleviation System for Light Airplanes. NASA 

TN D-8521, 1977. 

Trame, L. W.; Williams, L. E.; and Yurkovich, R. N.: Active Aeroelastic Oscillation Control on the 

F/A-18 Aircraft. AIAA Paper 85-1858, 1985. 

Waszak, M. R.: Modeling the Benchmark Active Control Technology Wind-Tunnel Model for 

Application to Flutter Suppression. AIAA Paper No. 96-3437, 1996. 

Woods-Vedeler, J. A.; Pototzky, A. S.; and Hoadley, S. T.: Active Load Control During Rolling 

Maneuvers. NASA TP 3455, 1994. 

Joined Wing 

Frink, N.T., Pirzadeh, S.Z, Parikh, P.C., Pandya, M.J., and Bhat, M.K.: Te NASA Tetrahedral 

Unstructured Software System. Te Aeronautical Journal, Vol. 104, No. 1040, October 2000, pp. 

491-499. 

Gallman, J.W.; and Kroo, I.M.: Structural Optimization for Joined-Wing Synthesis. Journal of 

Aircraft, Vol. 33, no. 1, 1996. pp 214-223. 

Gallman, J.W.; Smith, S.C.; and Kroo, I.M.: Optimization of Joined-Wing Aircraft. Journal of 

Aircraft, Vol. 30 no. 6, 1993. pp 897-905. 

Smith, S.C.; and Stonum, R.K.: Experimental Aerodynamic Characteristics of a Joined-Wing Research 

Aircraft Confguration. NASA TM 101083, 1989. 

342 Innovation in Flight 
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Smith, S.C.; Clif, S.E.; and Kroo, I.M.: Te Design of a Joined-Wing Flight Demonstrator Aircraft. 

AIAA Paper 87-2930, 1987. 

Tirpak, John A.: Wings to Come. Air Force Magazine, September 2001, pp. 33-39. 

Turner, C. D.; and Ricketts, R. H.: Aeroelastic Considerations for Patrol High Altitude Surveillance 

Platforms. AIAA Paper 83-0924, 1983. 

Wolkovitch, J.: Te Joined Wing: An Overview. AIAA Paper 85-0274, 1985. 

Vortex Flap 

Bare, E. A.; Reubush, D. E.; and Haddad, R. C.: Flow Field Over the Wing of a Delta-Wing Fighter 

Model With Vortex Control Devices at Mach 0.6 to 1.2. NASA TM-4296, 1992. 

Bobbitt, P. J.: Modern Fluid Dynamics of Subsonic and Transonic Flight, AIAA Paper 80-0861, 

1980. 

Brandon, J. M.; Brown, P. W; and Wunschel, A. J.: Impact of Vortex Flaps on Low-Speed Handling 

Qualities of a Delta Wing Aircraft. NASA TP-2747, 1987. 

Brandon, Jay M.; Hallissy, James B.; Brown, Philip W.; and Lamar, John E.: In-Flight Flow 

Visualization Results of the F-106B with a Vortex Flap. Paper Presented at the RTO AVT 

Symposium on Advanced Flow Management: Part A – Vortex Flows and High Angle of Attack 

for Military Vehicles, held in Loen, Norway, 7-11 May 2001, and published in RTO-MP-069(I). 

Campbell, James F.; Osborne, Russell F.; and Foughner, Jerome T., Jr.,eds.: Vortex Flow 

Aerodynamics, 1986. 

Erickson, Gary E.: Application of Free Vortex Sheet Teory to Slender Wings with Leading-Edge 

Vortex Flaps. AIAA-83-1813, July 1983. 

Frink, N. T.; Hufman, J. K.; and Johnson, T. D., Jr.: Vortex Flow Reattachment Line and Subsonic 

Aerodynamic Data for Vortex Flaps on 50° to 74° Delta Wings on Common Fuselage. NASA TM84618, 1983. 

Frink, Neal T.: Concept for Designing Vortex Flap Geometries. NASA TP-2233, 1983. 

Hallissy, James B.; Schoonover, W. Elliott, Jr.; Johnson, Tomas D., Jr.; and Brandon, Jay M.: WindTunnel Investigation of the Multiple Vortex System Observed in Flight Tests of the F-106B Vortex 

Flap Confguration. NASA TP-3322, 1993. 

Innovation in Flight 343 
BIBLIOGRAPHY 

Lamar, J. E.; Bruce, R. A.; Pride J. D., Jr., Smith, R. H.; Brown, P.W.; and Johnson, T. D., Jr.: InFlight Flow Visualization of F-106B Leading-Edge Vortex Using the Vapor Screen Technique. 

AIAA- Paper No. 86-9785, April 1986. 

Lamar, John E.: Subsonic Vortex-Flow Design Study for Slender Wings. Journal of Aircraft, Vol. 15, 

No. 9, September 1978, pp. 611-617. 

Lamar, John E.; and Campbell, James F.: Vortex Flaps – Advanced Control Devices for Supercruise 

Fighters. Aerospace America, pp. 95-99, January 1984. 

Lamar, John E.; Brandon, Jay; Stacy, Kathryn; Johnson, Tomas D., Jr.; Severance, Kurt; and 

Childers, Brooks A.: Leading-Edge Vortex-System Details Obtained on F-106B Aircraft Using a 

Rotating Vapor Screen and Surface Techniques. NASA TP-3374, 1993. 

Lamar, John E.; Hallissy, James B.; Frink, Neal T.; Smith, Ronald H.; Johnson, Tomas D., Jr.; Pao, 

Jenn-Louh; and Ghafari, Farhad: Review of Vortex Flow Projects on the F-106B. AIAA Paper 

No. 87-2346, August 1987. 

Lamar, John E.; Obara, Cliford J.; Fisher, Bruce D.; and Fisher, David F.: Flight, Wind-Tunnel, and 

Computational Fluid Dynamics Comparison for Cranked Arrow Wing (F-16XL-1) at Subsonic and 

Transonic Speeds. NASA TP-2001-210629, 2001. 

Lamar, John E.; Schemensky, R. T.; and Reddy, C. S.: Development of a Vortex-Lift Design 

Procedure and Application to a Slender Maneuver-Wing Confguration. Journal of Aircraft, vol. 

18, No. 4, pp. 259-266, April 1981. 

Murman, E. M.; Powell, K. G.; and Miller, D.S.: Comparison of Computations and Experimental 

Data for Leading-Edge Vortices – Efects of Yaw and Vortex Flaps. AIAA Paper No. 86-0439, 

January 1986. 

Papers of the Vortex Flow Aerodynamics Conference, Jointly Sponsored by NASA Langley and 

USAF Wright Aeronautical Laboratories, Hampton, Virginia, October 1985, NASA CP-2417, 

1986. 

Rao, D. M.: Leading Edge Vortex-Flap Experiments on a 74 Deg Delta Wing. NASA CR-159161, 1979. 

Rao, D. M.: Vortical Flow Management for Improved Confguration Aerodynamics – Recent 

Experiences. AGARD CP-342, Paper No. 30, 1983. 

Schoonover, W. E., Jr.; and Ohlson, W. E.: Wind-Tunnel Investigation of Vortex Flaps on a Highly 

Swept Interceptor Confguration, ICAS Paper 82-6.7.3, 1982. 

344 Innovation in Flight 
BIBLIOGRAPHY 

Schoonover, W. Elliott, Jr.; Frink, Neal T.; Hallissy, James B.; and Yip, Long P.: Subsonic/Transonic 

Development of Vortex Flaps for Fighter Aircraft, Langley Symposium on Aerodynamics, Vol. 2. 

Sharon H. Stack, Compiler, NASA CP-2 398, 1986, pp. 163-178. 

Vol.I, NASA CP-2416 

Vol. II, NASA CP-2417 

Vol. III, NASA CP-2418 

Yip, Long P.: Investigations of Vortex Flaps on the F-106B Confguration in the Langley 30 X 60-Foot 

Tunnel. NASA CP-2417, 1986. 

Yip, Long P.: Wind-Tunnel Free-Flight Investigation of a 0.15-Scale Model of the F-106B Airplane with 

Vortex Flaps. NASA TP-2700, 1987. 

Yip, Long P.; and Murri, Daniel G.: Efects of Vortex Flaps on the Low-Speed Aerodynamic 

Characteristics of an Arrow Wing. NASA TP-1914, 1981. 

Innovative Control Efectors 

Anglin, E. L.; and Satran, D. R.: Efects of Spanwise Blowing on Two Fighter Airplane 

Confgurations. AIAA Paper 79-1663, 1979. 

Bauer, Steven X. S.; and Hempsch, Michael J.: Alleviation of Side Force on Tangent-Ogive 

Forebodies Using Passive Porosity. AIAA Paper 92-2711, 1992. 

Buttrill, Carey S.; Bacon, Barton J.; Heeg, Jennifer; Houck, Jacob A., and Wood, David V.: 

Aeroservoelastic Simulation of an Active Flexible Wing Wind Tunnel Model. NASA Technical Paper 

3510, 1996. 

Campbell, J. F.: Augmentation of Vortex Lift by Spanwise Blowing. AIAA Paper 75-993, 1975. 

Campbell, J. F.; and Erickson, G. E.: Efects of Spanwise Blowing on Te Surface Pressure Distribution 

and Vortex-Lift Characteristics of a Trapezoidal Wing-Strake Confguration. NASA-TP-1290 , 

1979. 

Deere, Karen A.: Summary of Fluidic Trust Vectoring Research Conducted at NASA Langley 

Research Center. AIAA Paper 2003-3800, 2003. 

Erickson, G. E.; and Campbell, J. F.: Improvement of Maneuver Aerodynamics by Spanwise Blowing. 

NASA TP-1065, 1977. 

Innovation in Flight 345 
BIBLIOGRAPHY 

Frink, Neal T.; Bauer, Steven X. S.; and Hunter, Craig A.: Simulation of Flows with Passive 

Porosity. ICAS Paper 2002-2.10.2., 2002. 

Heeg, Jennifer; Spain, Charles V., and Rivera, J. A.: Wind Tunnel to Atmospheric Mapping for 

Static Aeroelastic Scaling. AIAA Paper 2004-2044, 2004, pp. 12. 

Hufman, J. K.; Hahne, D. E.; and Johnson, T. D., Jr.: Experimental Investigation of the 

Aerodynamic Efects of Distributed Spanwise Blowing on a Fighter Confguration. AIAA Paper 

84-2195, 1984. 

Hunter, C.A.; Viken, S.A.; Wood, R. M.; and Bauer, S. X. S.: Advanced Aerodynamic Design of 

Passive Porosity Control Efectors. AIAA Paper 2001-0249, 2001. 

Lamar, J. E.; and Campbell, J. F.: Recent Studies at NASA-Langley of Vortical Flows Interacting 

with Neighboring Surfaces. AGARD Conference Proceedings No. 342, July 1983. ISBN 92-

835-0334-1, pages 10-1 to 10-32. 

Mukhopadhyay, Vivek: Flutter Suppression Digital Control Law Design and Testing for the AFW 

Wind-Tunnel Model. AIAA Paper 92-2095, 1992. 

Murri, Daniel G.; and Rao, Dhanvada M.: Exploratory Studies of Actuated Forebody Strakes for 

Yaw Control at High Angles of Attack. AIAA Paper 87-2557, 1987. 

Murri, Daniel G.; Fisher, David F.; and Lanser, Wendy R.: Flight Test Results of Actuated Forebody 

Strake Controls on the F-18 High-Alpha Research Vehicle. NASA CP-1998-207676, Part 2, June, 

1998. 

Murri, Daniel G.; Shah, Gautam H.; DiCarlo, Daniel J.; and Trilling, Todd W.: Actuated Forebody 

Strake Controls for the F-18 High-Alpha Research Vehicle. Journal of Aircraft, Vol. 32, No. 3, 

May-June 1995, pp. 555-562. 

Noll, Tomas E.; Perry, Boyd, III; Tifany, Sherwood H.; Cole, Stanley R.; Buttrill, Carey S.; 

Adams, William M., Jr.; Houck, Jacob A.; Srinathkumar, S.; Mukhopadhyay, Vivek; Pototzky, 

Anthony S.; Heeg, Jennifer; McGraw, Sandra M.; Miller,Gerald; Ryan, Rosemary; Brosnan, 

Michael; Haverty, James; and Klepl, Martin: Aeroservoelastic Wind-Tunnel Investigations Using the 

Active Flexible Wing Model—Status and Recent Accomplishments. NASA TM-101570, 1989. 

Paulson, J. W., Jr.; Quinto, P. F.; and Banks, D. W.: Investigation of Trailing-Edge-Flap, SpanwiseBlowing Concepts on an Advanced Fighter Confguration. NASA-TP-2250 , 1984. 

346 Innovation in Flight 
BIBLIOGRAPHY 

Perry, Boyd, III; Cole, Stanley R.; and Miller, Gerald D.: A Summary of the Active Flexible Wing 

Program. AIAA Paper 92-2080, 1992. 

Perry, Boyd, III; Mukhopadhyay, Vivek; Hoadley, Sherwood Tifany; Cole, Stanley R.; and Buttrill, 

Carey S.: Digital-Flutter-Suppression-System Investigations for the Active Flexible Wing WindTunnel Model. AIAA Paper 90-1074, 1990. 

Rao, D. M.: Vortical Flow Management for Improved Confguration Aerodynamics - Recent 

Experiences. AGARD Conference Proceedings No. 342, July 1983. pp 30-1 to 30-14. 

Satran, D. R.; Gilbert, W. P.; and Anglin, E. L.: Low-Speed Stability and Control Wind-Tunnel 

Investigations of Efects of Spanwise Blowing on Fighter Flight Characteristics at High Angles of 

Attack. NASA-TP-2431, 1985. 

Shah, Gautam H.; and Granda, J. Nijel: Application of Forebody Strakes for Directional Stability 

and Control of Transport Aircraft. AIAA Paper 98-444, 1998. 

Waszak, M. R.; and Srinathkumar, S.: Flutter Suppression for the Active Flexible Wing: Control 

System Design and Experimental Validation. AIAA Paper 92-2097, 1992. 

Wood, R. M. and Bauer, S. X. S.: Advanced Aerodynamic Control Efectors. SAE Paper 1999-01-5619, 

1999. 

Wood, R. M.; Banks, D. W.; and Bauer, S.X.S.; Assessment of Passive Porosity with Free and Fixed 

Separation on a Tangent Ogive Forebody. AIAA 92-4494, 1992. 

Personal Air Transportation Concepts 

Anders, Scott G.; Asbury, Scott C.; Brentner, Kenneth S.; Bushnell, Dennis M.; Glass, Christopher 

E; Hodges, William T.; Morris, Shelby J., Jr.; and Scott, Michael A.: Te Personal Aircraft: Status 

and Issues. NASA TM-109174, 1994. 

Flemisch, Frank O.; Adams, Catherine A.; Conway, Sheila R.; Goodrich, Ken H.; Palmer, Michael 

T.; and Schutte, Paul C.: Te H-Metaphor as a Guideline for Vehicle Automation and Interaction. 

NASA TM-2003-212672, 2003. 

McKinney, M. O.: Stability and Control of the Aerial Jeep. Preprint No. 10S, SAE Annual Meeting, 

1959. 

Moore, Mark D.: Personal Air Vehicles: A Rural/ Regional and Intra-Urban On-Demand 

Transportation System. AIAA Paper 2003-2646, 2003. 

Innovation in Flight 347 
BIBLIOGRAPHY 

Moore, Mark D.; and Hahn, Andrew S.: Highly Afordable Personal Air Vehicles. Contact Magazine. 

July/August 2002. 

Parlett, Lysle P.: Wind-Tunnel Investigation of a Small-Scale Model of an Aerial Vehicle Supported by 

Ducted Fans. NASA TN D-377, 1960. 

348 Innovation in Flight 
INDEX 

A-12 airplane ......................................................................................................................................................................23 

Abbott, Ira H....................................................................................................................................................................132 

Abel, Irving...............................................................................................................................................................196, 213 

ACA Industries................................................................................................................................................................ 227 

Acoustical Society of America ........................................................................................................................................... 36 

Active Aeroelastic Wing (AAW) Flight Program..............................................................................................................292 

Active Controls Technology (ACT) Program...................................................................................................................211 

Active fexible wing (AFW)......................................................................................................................................216, 290 

Active futter suppression............................................................................192, 196, 200, 201, 203, 211, 213, 215, 217, 292 

Active load alleviation........................................................................................193, 203, 205, 209, 211, 213, 215, 226, 294 

Active Oscillation Suppression (AOS) system.................................................................................................................. 202 

Active roll control system .................................................................................................................................................216 

Actively Controlled Response of Bufet Afected Tails (ACROBAT) ............................................................................. 222 

Actuated Nose Strake for Enhanced Rolling (ANSER)....................................................................................................283 

Adams, James J...................................................................................................................................................................99 

Adams, Jr., William M. ....................................................................................................................................................213 

Adaptive Neural Control of Aeroelastic Response Program .............................................................................................219 

Advanced Concepts for Aeronautics Program (ACP) ........................................................................................................ 80 

Advanced General Aviation Transport Experiments (AGATE) Program ................................................ 100, 305, 306, 309 

Advanced Medium STOL Transport (AMST)..........................................................................................................167, 181 

Advanced Supersonic Technology (AST) Program.............................................................................................................39 

Advanced Supersonic Technology Ofce (ASTO)........................................................................................................39, 40 

Aerial applications joined-wing aircraft concept.......................................................................................................228, 231 

Aerion Corporation ............................................................................................................................................................70 

Aeroelastic research wings (ARW)....................................................................................................................................213 

Aeroelastic response of vertical tails..................................................................................................................................221 

Aeronautical Flight Vehicle Technologies Demonstrator (AVTD) ..................................................................................297 

Aeronautical Systems Division (ASD) ............................................................................................................................... 40 

Aeronautical Systems Ofce (ASO)....................................................................................................................................39 

Aeronautics and Space Engineering Board (ASEB) ............................................................................................................69 

Aerospace Vehicle Systems Technology Ofce (AVSTO) .................................................................................................312 

AFFDL B-52 Control Confgured Vehicle (CCV) Program............................................................................................ 209 

Aiken, Jr., William S. .........................................................................................................................................................39 

Air Force Aero Confguration/Weapons Fighter Technology Program ........................................................................... 290 

Air Force Flight Dynamics Laboratory (AFFDL).............................................................................................198, 207, 208 

Innovation in Flight 349 
INDEX 

Air Force Research Laboratory (AFRL)........................................................................................... 222, 223, 224, 239, 242 

Air Force Wright Aeronautical Laboratories (AFWAL)....................................................................................200, 216, 256 

Air taxi operations .................................................................................................................... 299, 301, 306, 308, 310, 318 

Airbus...................................................................................................................................................75, 92, 152, 193, 226 

Aircraft Energy Efciency (ACEE) Program ............................................................................................................134, 211 

Alford, Jr., William J. ................................................................................................................................................ 28, 134 

Allied Signal Aerospace ....................................................................................................................................................152 

American Airlines.....................................................................................................................................................105, 112 

Ames 12-Foot Pressure Tunnel................................................................................................................................ 234, 235 

Ames Research Center............................................................................ 26, 53, 65, 172, 181, 188, 230, 233, 257, 266, 304 

Ames Research Center 6- by 6-Foot Supersonic Tunnel ..................................................................................................257 

American Technology Alliances .........................................................................................................................................70 

An-72 aircraft ...................................................................................................................................................................188 

Andre, Tony......................................................................................................................................................................104 

Anglin, Ernie L.................................................................................................................................................................275 

Antclif, Richard R. ..........................................................................................................................................................320 

Antinello, John S. .............................................................................................................................................................166 

Arthur, III, Jarvis J. .........................................................................................................................102, 104, 110, 112, 114, 

ARW-1 wing.....................................................................................................................................................................213 

ARW-2 wing.....................................................................................................................................................................213 

Asheville Regional Airport ...............................................................................................................................................106 

Australian Aeronautical and Maritime Research Laboratory (AMRL)............................................................................ 224 

Australian Defence Sciences & Technology Organisation .............................................................................................. 224 

Autonomous Robust Avionics (Aura) project ...................................................................................................................313 

Aviation Safety and Security Program (AvSSP) ..................................................................................................................98 

Aviation Safety Program (AvSP).........................................................................................................................................98 

Avidyne.............................................................................................................................................................................100 

AvroTec Corporation ................................................................................................................................................100, 106 

Ayers, Teodore ...............................................................................................................................................................276 

B. F. Goodrich..................................................................................................................................................................106 

B-2 aircraft .........................................................................................................................................................................73 

Baals, Donald D. ....................................................................................................................................................26, 27, 34 

BAE Systems.....................................................................................................................................................................105 

Bailey, Randy......................................................................................................................................107, 110, 111, 112, 114 

Baize, Daniel G. ....................................................................................................................................... 53, 57, 60, 98, 112 

Bales, Tomas T. ..........................................................................................................................................................52, 58 

Banks, Daniel W. .............................................................................................................................................................289 

350 Innovation in Flight 
INDEX 

Bare, E. Ann.....................................................................................................................................................................238 

Baron, Robert S................................................................................................................................................................138 

Bartels, Robert E. ...............................................................................................................................................................91 

Barthelemy, Jean-Francois M. ..........................................................................................................................................296 

Bartlett, Dennis W. .......................................................................................................................................... 139, 140, 211 

Bauer, Steven X. S....................................................................................................................... 57, 287, 289, 290, 296, 297 

Becker, John V. .................................................................................................................................................................133 

Benchmark Models Program (BMP) ................................................................................................................................218 

Bennett, Robert M. ..........................................................................................................................................................218 

Bergeron, Hugh P. ..............................................................................................................................................................99 

Berrier, Bobby L. ............................................................................................................................. 236, 278, 280, 296, 297 

Biedron, Robert T.......................................................................................................................................................91, 283 

Bielat, Ralph P. .................................................................................................................................................................. 34 

Blakey, Marion .................................................................................................................................................................311 

Blended wing body (BWB).................................................................................................................................................71 

Bobbitt, Percy J.......................................................................................................................................52, 65, 66, 135, 253 

Boeing .............................................................. 27, 28, 29, 30, 31, 32, 33, 34, 35, 37, 38, 40, 41, 45, 49, 53, 58, 61, 62, 65, 

71,72, 75, 77, 79, 82, 83, 84, 88, 89, 91, 93, 103, 105, 107, 108, 110, 112, 133, 134, 139, 140, 141, 142, 

143, 145, 146, 147, 149, 153, 155, 156, 167, 168, 181, 182, 183, 184, 186, 187, 193, 196, 207, 208, 209, 210, 

217, 219, 221, 224, 226, 228, 236, 235, 236, 237, 238, 239, 241, 243, 244, 245, 246, 254, 281, 286, 291, 292 

Boeing 367-80 ....................................................................................................................................................................37 

Boeing 747-400 ..................................................................................................................................................................75 

Boeing 757..........................................................................................................108, 109, 111, 139, 140, 142, 143, 145, 153 

Boeing B-52.......................................................................................................................191, 193, 209, 210, 211, 212, 214, 

Boeing Defense and Space Group’s Military Airplane Division ...................................................................................... 236 

Boeing YC-14 ................................................................................................................................................... 168, 169, 181 

Boeing-Wichita.................................................................................................................................................................196 

Bogert, Phillip B.............................................................................................................................................................. 240 

Bohn-Meyer, Marta..................................................................................................................................................140, 156 

Bonhaus, Daryl L. ....................................................................................................................................................289, 290 

Boswinkle, Robert W. ........................................................................................................................................................27 

Bower, Robert E. ................................................................................................................................................................39 

Box plane concept............................................................................................................................................................ 227 

Boxer, Emanuel .......................................................................................................................................................... 27, 152 

Brandon, Jay M. .......................................................................................................................................259, 260, 261, 262 

Braslow, Albert L..............................................................................................................................130, 132, 133, 134, 135 

Bridges, Jr., Roy D............................................................................................................................................................320 

Innovation in Flight 351 
INDEX 

British Aerospace ..............................................................................................................................................................198 

Brooks, Jr., Cuyler W........................................................................................................................................................135 

Brown, Clinton E. ........................................................................................................................................................20, 33 

Brown, Phillip W.............................................................................................................................................. 110, 259, 260 

Bryant, Wayne H..............................................................................................................................................................104 

Bufet.................................................................................................................................................. 83, 128, 191, 192, 220 

Burley, James R. .......................................................................................................................................................309, 313 

Burrows, Dale L. ..............................................................................................................................................................132 

Bush, George W..................................................................................................................................................................70 

Bushnell, Dennis M. ............................................................................................................ 1, 4, 60, 77, 305, 312, 319, 320 

Buttrill, Carey S. ......................................................................................................................................................216, 292 

C-130................................................................................................................................................................ 180, 182, 215 

C-17...................................................................................................................................................................167, 185, 189 

C-45 ................................................................................................................................................................................ 207 

C-5 ........................................................................................................................................... 132, 133, 167, 182, 205, 206 

C-5A active lift distribution control system (ALDCS) .................................................................................................... 205 

C-8 augmentor wing research aircraft ..............................................................................................................................166 

Calloway, Robert L.......................................................................................................................................................53, 57 

Campbell, Bryan ................................................................................................................................................................57 

Campbell, James F............................................................................................................................ 253, 256, 274, 275, 276 

Campbell, John P...............................................................................................................................................167, 172, 174 

Campbell, Richard L.............................................................................................................................. 57, 82, 88, 141, 243 

Capone, Francis J................................................................................................................................................................57 

Carlson, Harry W........................................................................................................................... 19, 26, 27, 32, 33, 34, 37 

Carter, Melissa B. .............................................................................................................................................................. 88 

Catalano, Richard F. ........................................................................................................................................................296 

Cawthorn, Jerome H. .......................................................................................................................................................297 

Cazier, Frank W........................................................................................................................................200, 201, 204, 257 

CDISC code ........................................................................................................................................................ 82, 88, 243 

Center Director’s Discretionary Fund (CDDF)........................................................................................................ 319, 320 

Cessna........................................................................................................................................118, 119, 149, 176, 206, 209 

CFL3D code...................................................................................................................................................................... 88 

Chambers, Joseph R. ....................................................................................................... 60, 79, 80, 84, 238, 265, 266, 275 

Chelton Flight Systems.............................................................................................................................................120, 121 

Chlorofuoromethanes (CFM)........................................................................................................................................... 46 

Chu, Julio .......................................................................................................................................................................... 80 

Clark, Lorenzo R..........................................................................................................................................................90, 91 

352 Innovation in Flight 
INDEX 

Clark-Atlanta University ................................................................................................................................................... 80 

Climatic Impact Assessment Program (CIAP) ...................................................................................................................45 

Coanda efect....................................................................................................................................................................167 

COBALT code ................................................................................................................................................................ 242 

Cobb, Jere B. ......................................................................................................................................................................38 

Cockpit Display of Trafc Information (CDTI) ..............................................................................................................310 

Coe, Jr., Paul L. ....................................................................................................................................................42, 52, 255 

Coen, Peter G...............................................................................................................................................................65, 66 

Cole, Stanley R.........................................................................................................................................................216, 292 

Coleman, Tomas L. ..........................................................................................................................................................25 

Collier, Jr., Fayette S................................................................................................................................. 140, 146, 152, 153 

Computational fuid dynamics (CFD).........................................................................55, 66, 68, 82, 88, 91, 142, 146, 153,

 155, 158, 196, 218, 226, 238, 242, 244, 258, 264, 272, 280, 283, 289, 297, 298 

Comstock, Jr., James R...............................................................................................................................................98, 102 

Concept to Reality...................................................................................................................................vi, 2, 126, 183, 195 

Concorde .............................................................................................................. 7, 10, 12, 14, 28, 48, 60, 62, 64, 101, 247 

Condit, Philip M................................................................................................................................................................38 

Conner, D. William ........................................................................................................................................................ 207 

Control of aeroelastic response .........................................................................................................................................191 

Controlled fight into terrain (CFIT) .........................................................................................................93, 104, 106, 120 

Conway, Erik M. ................................................................................................................................................................15 

Cooke, Stuart .................................................................................................................................................................. 309 

Cortright, Edgar M. .................................................................................................................................................134, 173 

COSAL code .................................................................................................................................................... 142, 146, 155 

Couch, Lana M. ................................................................................................................................................................ 34 

Counterfow method of fuidic thrust vectoring.............................................................................................................. 280 

Craidon, Charlotte B..........................................................................................................................................................32 

Crane, Harold L. ................................................................................................................................................................38 

Creativity and Innovation (C&I) Initiative ......................................................................................................................320 

Creedon, Jeremiah F...................................................................................................................................................84, 319 

Croom, Delwin R. ............................................................................................................................................................ 22 

Croom, Jr., Delwin R. ............................................................................................................................. 104, 105, 112, 114 

Curtiss-Wright................................................................................................................................................................... 28 

Dagenhart, Joel R. ...........................................................................................................................................................135 

Daimler Benz Aerospace.................................................................................................................................................. 222 

Dallas-Fort Worth (DFW) International Airport ....................................................................................................108, 109 

Dansberry, Bryan E..........................................................................................................................................................218 

Innovation in Flight 353 
INDEX 

Danville Regional Airport ....................................................................................................................................... 310, 311 

Darden, Christine M....................................................................................................................................... 42, 43, 52, 54 

DARPA Quiet Supersonic Platform (QSP) Program..........................................................................................................65 

Dassault..............................................................................................................................................................................70 

Davenport, Edwin E.........................................................................................................................................................172 

Davis, Richard E. .............................................................................................................................................................138 

DC-10 ...................................................................................................................................................................... 211, 270 

DC-9 ............................................................................................................................................................................... 286 

Decker, John P................................................................................................................................................................... 34 

Decoupler pylon concept ................................................................................................................................................. 204 

Deep stall........................................................................................................................................................................... 34 

Deere, Karen A.................................................................................................................................................277, 280, 281 

Delft University of Technology ........................................................................................................................................105 

DeLoach, Richard ............................................................................................................................................................296 

Delta Airlines....................................................................................................................................................................112 

Delta wing futter suppression study.................................................................................................................................196 

Detweiler, Kurt N. ............................................................................................................................................................ 84 

DiCarlo, Daniel J. ............................................................................................................................................................283 

Dodbele, Simha S.............................................................................................................................................................149 

Doggett, Jr., Robert V...............................................................................................................................................208, 210 

Dollyhigh, Samuel M. .......................................................................................................................46, 50, 52, 79, 89, 146 

Douglas ............................................................................................................................................................130, 136, 211 

Driver, Cornelius .............................................................................................................................................24, 39, 40, 41 

Drones for Aerodynamic and Structural Testing (DAST)................................................................................................212 

Dryden Flight Research Center........................................................................19, 25, 33, 40, 44, 53, 56, 58, 60, 63, 65, 66

 67, 83, 84, 98, 135, 137, 138, 140, 155, 156, 204, 213, 214, 215, 223, 230, 237, 239, 

240, 266, 267, 270, 276, 283, 292, 294, 295, 297, 319 

Dunham, Dana J............................................................................................................................................................... 80 

Durham, Michael H.........................................................................................................200, 218, 232, 233, 257, 306, 309 

Dwoyer, Douglas L...........................................................................................................................................................320 

E-2C airplane .................................................................................................................................................................. 236 

Eagle Aeronautics ...............................................................................................................................................................65 

Eagle County Regional Airport (Vail, CO)......................................................................................................................110 

Eckhardt, Dave E. ..............................................................................................................................................98, 102, 104 

Eckstrom, Clinton V................................................................................................................................................. 213, 218 

Edwards Air Force Base......................................................................................................................... 24, 36, 56, 184, 204 

Electronics Experimental (EX) Program ......................................................................................................................... 236 

354 Innovation in Flight 
INDEX 

Elliott, James R. ................................................................................................................................................................ 80 

Embry-Riddle Aeronautical University.............................................................................................................................105 

Emissions...................................................................................................................... 4, 13, 40, 44, 45, 51, 61, 63, 72, 127 

Emissions Reduction Research and Technology Program ..................................................................................................45 

Energy Efcient Transport Program.................................................................................................................................139 

Engineer in Charge.............................................................................................................................................................17 

Enhanced vision systems (EVS)...................................................................................................... 94, 95, 96, 112, 114, 121 

Environmental Science Services Administration ............................................................................................................... 36 

Equivalent Laminated Plate Solution (ELAPS) ..................................................................................................................89 

ER-2 airplane......................................................................................................................................................................61 

Erickson, Gary E. .............................................................................................................................................274, 275, 283 

External stores ..................................................................................................................................193, 197, 200, 202, 204 

Externally blown fap (EBF) concept................................................................................................................................175 

F/A-18...............................................................................................................193, 202, 221, 222, 247, 282, 284, 285, 292 

F/A-18E/F wing drop........................................................................................................................................................289 

F-102 ..................................................................................................................................................................................21 

F-104 ..........................................................................................................................................................................36, 214 

F-105 ..................................................................................................................................................................................21 

F-106B..............................................................................................................................................................................256 

F-14 .................................................................................................................................................................... 39, 141, 221 

F-15 .................................................................................................................................................... 39, 155, 221, 224, 250 

F-15B ........................................................................................................................................................................... 66, 67 

F-16XL ................................................................................................................................... 42, 56, 67, 252, 255, 265, 267 

F-16XL Supersonic Laminar Flow Control (SSLFC) Flight Experiment..........................................................................156 

F-22 .................................................................................................................................. 146, 219, 221, 223, 224, 225, 277 

F-4....................................................................................................................................................................197, 276, 277 

F-5E........................................................................................................................................................................66, 67, 68 

F-8....................................................................................................................................................................................213 

FAA Alaskan Region Capstone Program..........................................................................................................................120 

FAA Civil Aerospace Medical Institute ............................................................................................................................106 

Farmer, Moses G. .............................................................................................................................198, 200, 201, 204, 218 

Federal Aviation Administration (FAA) .....................................................................25, 26, 28, 29, 31, 34, 36, 38, 97, 100

 108, 110, 112, 118, 119, 120, 121, 190, 212, 218, 304, 306, 309, 310, 311, 315 

Finelli, George B.................................................................................................................................................................98 

Fischer, Michael C........................................................................................................................................52, 58, 138, 156 

Fisher, David F. ........................................................................................................................................................138, 267 

Flamm, Jefery D............................................................................................................................................................. 280 

Innovation in Flight 355 
INDEX 

Flight Dynamics, Inc........................................................................................................................................................105 

Flight International, Inc. ..................................................................................................................................................106 

Florida State University ....................................................................................................................................................281 

Fluidic Injection Nozzle Technology (FLINT) Program..................................................................................................278 

Fluidic thrust vectoring ........................................................................................................................................... 272, 277 

Flutter Research and Experiment Device (FRED) .......................................................................................................... 220 

Flutter speed .....................................................................................................................................................................192 

Flutter suppression....................................................................................................................................................192, 196 

Flying cars ........................................................................................................................................................................311 

Flying platform vehicles....................................................................................................................................................303 

Forebody strakes.......................................................................................................................................270, 283, 285, 286 

Foss, Willard E...................................................................................................................................................................25 

Foster, John V. ......................................................................................................................................................... 296, 297 

Foughner, Jerome T. ........................................................................................................................................................ 200 

Freeman, Jr., Delma C............................................................................................................................................29, 34, 35 

Fremaux, Charles M...............................................................................................................................................86, 87, 91 

Frink, Neal T.............................................................................................................................. 91, 238, 253, 257, 258, 290 

Fuel costs ..........................................................................................................................14, 48, 62, 68, 126, 129, 134, 159 

Fuhrmann, Henri D. ....................................................................................................................................................79, 80 

Fuller, Dennis E. ............................................................................................................................................................... 34 

Fullerton, C. Gordon......................................................................................................................................................... 60 

Gallman, John W. ....................................................................................................................................................233, 235 

Gates, Tomas S. ..........................................................................................................................................................57, 58 

General aviation airports ..................................................................................................................................................299 

General Aviation Propulsion (GAP) Program.................................................................................................................. 308 

General Aviation Stall/Spin Program ...............................................................................................................................100 

General Dynamics....................................................................................................................... 42, 43, 200, 204, 252, 253 

General Electric..............................................................................................23, 28, 41, 44, 53, 65, 149, 150, 151, 153, 281 

Gerhold, Carl H. ..........................................................................................................................................................90, 91 

Gilbert, William P. .......................................................................................................................................................53, 65 

Giles, Gary L......................................................................................................................................................................89 

Gilman, Jr., Jean...............................................................................................................................................................210 

Glaab, Louis J................................................................................................................................................... 102, 110, 118 

Glenn Research Center...................................................................................................................................... 66, 256, 308 

Global Positioning System (GPS) ..............................................................................94, 95, 96, 98, 103, 111, 112, 120, 310 

Goad, William K................................................................................................................................................................89 

Goldin, Daniel S. .................................................................................................................................................. 20, 62, 83 

356 Innovation in Flight 
INDEX 

Golub, Robert A.................................................................................................................................................................52 

Goodman, Wesley L.........................................................................................................................................................238 

Goodrich, Kenneth H. ............................................................................................................................................. 313, 311 

Goodwin, Garland O. ......................................................................................................................................................258 

Grafton, Sue B....................................................................................................................................................85, 259, 283 

Grantham, William D................................................................................................................................................. 38, 42 

Gratzer, Louis B. ..............................................................................................................................................................139 

Green, Walter S. ...............................................................................................................................................................100 

Grey, David C. .................................................................................................................................................................196 

Gridlock Commuter ......................................................................................................................................................... 315 

Grifn, Michael................................................................................................................................................................311 

Grose, William L................................................................................................................................................................52 

Gulfstream .................................................................................................................. 65, 69,70, 96, 113, 114, 115, 117, 121 

Gust alleviation system.............................................................................................................................................207, 208 

Gust load alleviation..................................................................................................................................193, 207, 211, 213 

Hahn, Andrew S...............................................................................................................................................................312 

Hahne, David E. ................................................................................................................................51, 266, 276, 277, 309 

Hall, Albert W....................................................................................................................................................................38 

Hall, Robert M...................................................................................................................................................................91 

Hallissy, James B. ..............................................................................................................................141, 257, 259, 260, 264 

Hammond, Alexander D.......................................................................................................................... 172, 174, 182, 183 

Hansen, James R. ...............................................................................................................................................................17 

Harrah, Steven.................................................................................................................................... 98, 104, 110, 112, 114 

Harris, Charles D. ............................................................................................................................................................135 

Harris, Jr., Roy V. ................................................................................................................26, 27, 32, 33, 60, 147, 251, 260 

Harvey, William D...........................................................................................................................................................135 

Hassell, Jr., James L.................................................................................................................................. 174, 182, 184, 185 

Hastings, Jr., Earl C. ........................................................................................................................................................149 

Haering, Edward A., Jr...................................................................................................................................................... 66 

Heeg, Jennifer...................................................................................................................216, 219, 220, 221, 222, 292, 294 

Hefner, Jerry N.........................................................................................................................................................309, 310 

Heim, Eugene.....................................................................................................................................................................87 

Heldenfels, Richard R. .......................................................................................................................................................27 

Hemsch, Michael J. ..........................................................................................................................................................289 

Henderson, William P. .................................................................................................................................................... 236 

Hergenrother, Paul M.........................................................................................................................................................58 

Heyman, Joseph ...............................................................................................................................................................320 

Innovation in Flight 357 
INDEX 

High Altitude Pollution Program (HAPP) .........................................................................................................................45 

High Angle of Attack Research Vehicle (HARV)............................................................................................ 223, 283, 286 

High Speed Dreams ...........................................................................................................................................................15 

High Speed Research (HSR) Program...........................................................................................................17, 49, 101, 102 

High-Angle-of-Attack Technology Program (HATP)............................................................................................. 283, 286 

High-speed civil transport (HSCT) ..................................................................................49, 50, 52, 57, 58, 61, 62, 64, 155 

Highway in the sky (HITS)............................................................................................ 94, 97, 99, 100, 101, 120, 308, 316 

H-mode control concept...................................................................................................................................................313 

Hoad, Danny R................................................................................................................................................................181 

Hoadley, Sherwood T. .............................................................................................................................................. 216, 218 

Hofer, Keith D................................................................................................................................................................283 

Holmes, Bruce J........................................................................................................................304, 305, 306, 307, 309, 317 

Hood, Jr., Ray V. .............................................................................................................................................. 139, 194, 211 

Houbolt, John C................................................................................................................................................................ 46 

Houck, Jacob A. .......................................................................................................................................................216, 292 

HSR Program External Visibility System (XVS) element................................................................................... 97, 102, 103 

HSR Reference H confguration.............................................................................................................................53, 54, 57 

HSR Technology-Concept Airplane (TCA)...................................................................................................................... 54 

Hub and spoke airports ............................................................................................................................................299, 307 

Hubbard, Harvey H. .......................................................................................................................... 19, 25, 28, 36, 37, 172 

Huckel, Vera...................................................................................................................................................................... 36 

Hueschen, Richard .............................................................................................................................................98, 104, 110 

Hufman, Jarrett K............................................................................................................................................. 34, 257, 276 

Hughes, Monica F. ...........................................................................................................................................................118 

Hunter, Craig A....................................................................................................................................................... 290, 297 

Hunting 126 jet-fap research aircraft...............................................................................................................................166 

Hybrid laminar fow control (HLFC)..........................................................................................92, 125, 139, 143, 147, 154 

Hypersonics..................................................................................................................................................................19, 49 

Ice............................................................................................................................................. 129, 133, 138, 143, 152, 308 

Incubator Institute............................................................................................................................................................320 

Innovation Institute..........................................................................................................................................................320 

Innovative control efectors ..............................................................................................................................................269 

Intermap Technologies Corporation.................................................................................................................................105 

Internally blown jet-fap systems ......................................................................................................................................166 

International Space Station (ISS)........................................................................................................................................62 

Jackson, Charlie M.............................................................................................................................................................50 

Jacobs, Eastman N. .................................................................................................................................................... 17, 132 

358 Innovation in Flight 
INDEX 

Jeppesen............................................................................................................................................ 105, 106, 108, 112, 114 

Johnson, James W............................................................................................................................................................ 240 

Johnson, Jr., Joseph L. .................................................................................................42, 172, 174, 175, 176, 182, 231, 275 

Johnson, Jr., William C....................................................................................................................................................174 

Johnson, Sally C. ............................................................................................................................................................. 309 

Johnson, Stuart K............................................................................................................................................................ 280 

Johnson, Tomas D. .........................................................................................................................260, 261, 264, 274, 276 

Joined wing aircraft ......................................................................................................................................................... 227 

Joined-Wing Flight Demonstrator (JWFD) Project ........................................................................................................ 240 

Joined-wing research aircraft (JWRA) ............................................................................................................................ 234 

Joint Planning and Development Ofce (JPDO) .............................................................................................................317 

Jones, Denise R. ................................................................................................................................................105, 110, 114 

Jones, Kenneth M.............................................................................................................................................................255 

Jones, Kennie H................................................................................................................................................................153 

Jones, Robert T...................................................................................................................................................................18 

Jordan, Frank L. ...............................................................................................................................................................283 

Joslin, Ronald D. ..............................................................................................................................................................130 

Kagey, III, Leslie O...........................................................................................................................................................112 

Kariya, Timmy T............................................................................................................................................................. 236 

KC-135 ...............................................................................................................................................................................91 

Kegelman, Jerome T. ........................................................................................................................................................153 

Keller, Donald F. ..............................................................................................................................................................221 

Kemmerly, Guy ..........................................................................................................................................................57, 309 

Kennedy, John F. ....................................................................................................................................................23, 25, 28 

Kirby, Robert H............................................................................................................................................................... 304 

Kjerstad, Kevin.................................................................................................................................................................255 

Knight, Jr., Vernie H. ............................................................................................................................................... 152, 154 

Kramer, Lynda J. ...............................................................................................................103, 104, 105, 108, 110, 112, 114 

Krist, Steven E............................................................................................................................................57, 238, 242, 243 

Kroo, Ilan M. .....................................................................................................................................................81, 233, 235 

Krueger fap/shield.....................................................................................................................144, 146, 148, 158, 174, 179 

Kudlinski, Robert A. ........................................................................................................................................ 104, 105, 112 

Kuhn, Richard E. .............................................................................................................................................172, 182, 183 

Kvaternik, Raymond G.................................................................................................................................................... 200 

L-1011-500 .......................................................................................................................................................................212 

Lake, Renee C. .................................................................................................................................................................221 

Lamar, John E. ........................................................................................................................................ 253, 260, 262, 267 

Innovation in Flight 359 
INDEX 

Laminar fow control (LFC).............................................................................................................................................123 

Laminar-Flow Control Project Ofce (LFCPO)................................................................................ 139, 149, 155, 156, 158 

Lancair/PAC USA ............................................................................................................................................................106 

Langford, William M. ................................................................................................................................................. 84, 90 

Langley 12-Foot Low-Speed Tunnel ............................................................................................................................... 286 

Langley 14- by 22-Foot Tunnel.....................................................................................................41, 85, 174, 241, 255, 289 

Langley 16-Foot Transonic Dynamics Tunnel (TDT).....................................................................................................194 

Langley 16-Foot Transonic Tunnel ....................................................... 34, 57, 150, 236, 238, 239, 241, 278, 291, 296,297 

Langley 20-Foot Vertical Spin Tunnel .................................................................................................................86, 87, 241 

Langley 30- by 60-Foot (Full Scale) Tunnel........................................................... 34, 35, 41, 172, 250, 255, 275, 276, 304 

Langley 300 mph 7- by 10-Foot Tunnel...........................................................................................................................173 

Langley 4- by 4-Foot Unitary Plan Wind Tunnel ............................................................................................................ 43 

Langley 7- by 10-Foot High Speed Tunnel.........................................................................................................41, 173, 264 

Langley 8-Foot Transonic Pressure Tunnel ..............................................................................................................134, 153 

Langley Anechoic Noise Research Facility ........................................................................................................................ 90 

Langley Boeing 757-200 Airborne Research Integrated Experiments System (ARIES) research aircraft................108, 109, 

110, 111, 112 

Langley Cessna 206 research aircraft................................................................................................................................119 

Langley Diferential Maneuvering Simulator (DMS)....................................................................................... 259, 267, 283 

Langley Electromagnetics Test Facilities ..........................................................................................................................241 

Langley Jet Exit Test Facility (JETF) .............................................................................................................................. 280 

Langley National Transonic Facility (NTF)...............................................................................................................82, 171 

Langley Nondestructive Test Laboratory..........................................................................................................................241 

Langley Structures and Materials Laboratory...................................................................................................................241 

Langley Visual Motion Simulator (VMS) ......................................................................................................................... 88 

Leading Edge Flight Experiment (LEFT) ........................................................................................................................135 

Leatherwood, J. D. .............................................................................................................................................................55 

Lee, Cynthia C. ................................................................................................................................................................152 

Leonard, Robert C. ..........................................................................................................................................................134 

Lessard, Victor..................................................................................................................................................................255 

Lessard, Wendy...................................................................................................................................................................57 

Lewis Research Center................................................................................................20, 25, 33, 40, 44, 45, 50, 53, 80, 256 

Lewis, Michael S. ...............................................................................................................................................................98 

Liebeck, Robert H. .................................................................................................................................................77, 78, 79 

Lift/drag (L/D) ratio...........................................................................9, 10, 33, 35, 42, 77, 82, 88, 248, 253, 262, 264, 266 

Limit cycle oscillation (LCO)...........................................................................................................................201, 202, 203 

Lippisch DM-1 glider .......................................................................................................................................................250 

360 Innovation in Flight 
INDEX 

Lockheed California..............................................................................................................................................27, 41, 211 

Lockheed Martin.....................................................................................42, 65, 70, 114, 201, 204, 225, 227, 252, 281, 292 

Lockheed Martin Tactical Aircraft Systems .............................................................................................................201, 295 

Lockheed-Georgia ....................................................................................................................................137, 142, 205, 227 

Lockwood, Vernon E......................................................................................................................................................... 34 

Loftin, Jr., Laurence K. (Larry) ....................................................................................................................................27, 33 

Low Visibility Landing And Surface Operations (LVLASO) project ......................................................................... 97, 103 

Mack, Robert J. ........................................................................................................................................................... 42, 54 

Maddalon, Dal V......................................................................................................................................................138, 145 

Maglieri, Domenic J. ................................................................................ 19, 24, 25, 28, 34, 36, 37, 40, 52, 55, 65, 66, 172 

Magruder, William M. .................................................................................................................................................39, 41 

Malik, Mujeeb R. ............................................................................................................................................. 142, 146, 155 

Margason, Richard J.........................................................................................................................................................172 

Marien, Ty V...................................................................................................................................................................... 80 

Mascitti, Vincent R. .......................................................................................................................................................... 40 

Massachusetts Institute of Technology (MIT) ................................................................................................ 106, 208, 220 

Mathouser, Eldon ...............................................................................................................................................................25 

McAninch, Gerry L............................................................................................................................................................52 

McCann, Rob...................................................................................................................................................................104 

McCurdy, David A. ........................................................................................................................................................... 66 

McDonnell Douglas.....................................................41, 45, 51, 52, 58, 77, 79, 82, 83, 155, 167, 183, 193, 202, 219, 276, 

286, 294 

McElroy, Marcus O........................................................................................................................................................... 80 

McGowan, Anna-Maria R................................................................................................................................................221 

McKinley, Robert E. ........................................................................................................................................... 80, 84, 239 

McKinney, Jr., Marion O. ..................................................................................................................................35, 174, 304 

McLean, F. Edward ........................................................................................................................ 15, 20, 26, 27, 33, 37, 40 

McNamara, Robert S. ........................................................................................................................................................23 

Messerschmitt-Bolkow-Blohm GmbH (MBB) .................................................................................................................198 

Meyer, Jr., Robert R. ........................................................................................................................................................140 

Middleton, David B.................................................................................................................................................. 139, 211 

Middleton, Wilbur D. ..................................................................................................................................................32, 33 

Miranda, Luis R. ............................................................................................................................................................. 227 

Modarelli, James J. ............................................................................................................................................................ 20 

Moore, Mark D. ............................................................................................................................................... 312, 313, 315 

Morello, Samuel A....................................................................................................................................................... 38, 82 

Morgan, Harry L............................................................................................................................................................. 242 

Innovation in Flight 361 
INDEX 

Morris, Odell A. ................................................................................................................................................................ 34 

Moses, Robert W. .................................................................................................................................... 222, 223, 224, 225 

Moul, Tomas M....................................................................................................................................................... 80, 296 

Mukhopadhyay, Vivek.......................................................................................................................... 80, 89, 213, 216, 292 

Multiple leading-edge vortices......................................................................................................................................... 260 

Muraca, Ralph J. ......................................................................................................................................................134, 136 

Murri, Daniel G. ............................................................................................................................ 80, 85, 87, 254, 281, 283 

Murrow, Harold N. ..........................................................................................................................................................213 

Nagel, Adelbert L. .....................................................................................................................................40, 133, 134, 139 

NASA AD-1 research aircraft.......................................................................................................................................... 234 

NASA JetStar (Lockheed C-140)......................................................................................................................................135 

NASA/Air Force/Boeing B757 HLFC Flight Experiment................................................................................................142 

NASA/GE HLFC Nacelle Flight Experiment .................................................................................................................. 151 

NASA/General Electric OV-1 NLF Nacelle Flight Experiment .......................................................................................149 

National Advisory Committee for Aeronautics (NACA)......................................................... 15, 17, 19, 20, 68, 83, 97, 130

 131, 132, 141, 194, 208, 218, 250, 269, 319 

National Consortium for Aviation Mobility (NCAM).............................................................................................309, 310 

National Full-Scale Aerodynamics Complex (NFAC) Facility........................................................................................ 222 

National Transportation Safety Board (NTSB)..........................................................................................................93, 118 

Natural laminar fow (NLF)......................................................................................................... 65, 69, 125, 132, 140, 142 

Naval Air Systems Command (NAVAIR) ........................................................................................................................239 

Newport News-Williamsburg International Airport ........................................................................................................119 

Newsom, Jerry R. .............................................................................................................................................................213 

Next-Generation Air Transportation System....................................................................................................................317 

Nguyen, Luat T. .........................................................................................................................................................42, 174 

Nichols, Mark R.............................................................................................................................................. 25, 26, 34, 40 

Nicks, Oran W. ................................................................................................................................................ 173, 174, 182 

Nissim, Elihu....................................................................................................................................................................196 

North American Aviation............................................................................................................................................21, 28, 

Northrop ..................................................................................................................................................................132, 198 

Northrop Grumman Corporation.............................................................................................................................. 65, 114 

Obara, Cliford J. ............................................................................................................................................... 89, 149, 267 

Ofce National d’Etudes et de Recherches Aerospatiale (ONERA)...........................................................................92, 198 

Ofce of Science and Technology................................................................................................................................ 36, 49 

Ohio University........................................................................................................................................ 106, 108, 112, 114 

Old Dominion University ................................................................................................................................................254 

Organization of Petroleum Exporting Countries (OPEC) ............................................................................... 129, 134, 159 

362 Innovation in Flight 
INDEX 

Orient Express ....................................................................................................................................................................49 

OVERDISC code............................................................................................................................................................ 243 

OVERFLOW code.................................................................................................................................................. 238, 242 

Owens, Lewis .....................................................................................................................................................................57 

Ozone .................................................................................................................................................................... 13, 46, 50 

P-51 airplane.....................................................................................................................................................................132 

PAB3D code .................................................................................................................................................................... 280 

Pao, Paul S..........................................................................................................................................................................91 

Parikh, Paresh...................................................................................................................................................................238 

Parlett, Lysle P. ........................................................................................................................................................ 180, 304 

Parrish, Russell V........................................................................................................................ 98, 102, 104, 108, 110, 112 

Partners in Freedom ...................................................................................................vi, 2, 42, 167, 195, 274, 281, 283, 289 

Passive porosity.................................................................................................................................271, 287, 289, 290, 294 

Pendergraft, Jr., Odis C..................................................................................................................................................... 88 

Pennington, Wendy F........................................................................................................................................................ 84 

Perry, III, Boyd..................................................................................................................................179, 194, 213, 216, 292 

Perry, Jr., Raleigh............................................................................................................................................................... 98 

Person, Lee H. ....................................................................................................................................................................38 

Personal air transportation concepts.................................................................................................................................299 

Personal air vehicles (PAV) .......................................................................................................................................299, 301 

Peterson, John P..........................................................................................................................................................24, 135 

PETI-5 material..................................................................................................................................................................58 

Pfenninger, Werner...................................................................................................................................132, 133, 134, 146 

Phelps, III, Arthur E..................................................................................................................................174, 175, 181, 182 

Phillips, Pamela S. ............................................................................................................................................................141 

Phillips, W. Hewitt...................................................................................................................................................207, 208 

Physical Sciences, Inc. ......................................................................................................................................................295 

Piezoelectric Aeroelastic Response Tailoring Investigation (PARTI)................................................................................219 

Pirzadeh, Shahyar.............................................................................................................................................................238 

Pitch up ..............................................................................................................................................................9, 30, 34, 74 

Plentovich, Elizabeth B.....................................................................................................................................................153 

Polhamus, Edward C................................................................................................................................................253, 274 

Poole, Lamont R.................................................................................................................................................................52 

Pototzky, Anthony S.................................................................................................................................................216, 292 

Powered-lift concepts........................................................................................................................................................164 

Pratt and Whitney................................................................................................................................................28, 41, 179 

Pride, Joseph D........................................................................................................................................................ 258, 260 

Innovation in Flight 363 
INDEX 

Pride, Richard A.................................................................................................................................................................27 

Propulsion integration ........................................................................................................................ 9, 31, 52, 73, 170, 230 

Quiet Experimental STOL Transport (QUESTOL)........................................................................................................187 

Quiet Short-Haul Research Aircraft (QSRA) ..........................................................................................................169, 187 

Radiation exposure.......................................................................................................................................................13, 61 

Rannoch Corporation ......................................................................................................................................106, 108, 114 

Rao, Dhanvada M. ...........................................................................................................................................254, 281, 283 

Raytheon ....................................................................................................................................................................65, 106 

Re, Richard J. ..............................................................................................................................34, 82, 236, 242, 296, 297 

Redd, L. Tracey ........................................................................................................................................................208, 210 

Reed, III, Wilmer H....................................................................................................................................................... 204 

Remsberg, Ellis E. ..............................................................................................................................................................52 

Reno-Tahoe International Airport....................................................................................................................................112 

Research Triangle Institute.............................................................................................................................. 106, 108, 308 

Revolutionary Airframe Concepts Research (RACR) project............................................................................................ 84 

Revolutionary Concepts for Aeronautics (RevCon) Program.............................................................84, 238, 239, 245, 294 

Reynolds number..................................................................88, 124, 127, 132, 135, 141, 146, 148, 158, 176, 231, 249, 283 

Reynolds, Osborne ...........................................................................................................................................................124 

Ricketts, Rodney H............................................................................................................................................53, 210, 232 

Riebe, John M. .................................................................................................................................................................172 

Rivera, Jr., Jose A..............................................................................................................................................................218 

Rivers, Robert A. ......................................................................................................................................................... 60, 88 

Roanoke Regional Airport...............................................................................................................................................119 

Robins, A. Warner............................................................................................................................................26, 27, 33, 50 

Rockwell Aero Commander USB tests.............................................................................................................................176 

Rockwell Collins ...................................................................................................................................... 105, 108, 112, 114 

Rockwell International Corporation ........................................................................................................................216, 291 

Rohr Industries, Inc..........................................................................................................................................................152 

Rolling maneuver load alleviation (RMLA) .....................................................................................................................217 

Roll-Out Turn-Of (ROTO) system.................................................................................................................................103 

Rose, Cheryl A................................................................................................................................................................... 80 

Royal Aircraft Establishment....................................................................................................................................132, 166 

Royal, Allen C................................................................................................................................................................. 309 

Runckel, Jack F...................................................................................................................................................................27 

Runway Incursion Prevention System (RIPS) .................................................................................................. 108, 109, 114 

Runyon, Jr., Harry L. ...................................................................................................................................................... 204 

Rutan, Elbert L. ...............................................................................................................................................................231 

364 Innovation in Flight 
INDEX 

S-3 airplane ..................................................................................................................................................................... 240 

Sandford, Maynard C................................................................................................................196, 206, 210, 213, 214, 216 

Satran, Dale R. .................................................................................................................................................................275 

SATSLab ..................................................................................................................................................................309, 310 

Sawyer, Wallace C. .......................................................................................................................................................50, 53 

Scaling Infuences Derived from Experimentally-Known Impact of Controls (SIDEKIC)..................................... 224, 225 

Scanning light sheet .........................................................................................................................................................262 

SCAT-15 ...................................................................................................................................................................... 26, 27 

SCAT-15F...................................................................................................................................................33, 34, 35, 41, 42 

Schade, Robert O. ..............................................................................................................................................................38 

Schoenster, James A.................................................................................................................................................. 149, 179 

Schoonover, Jr., W. Elliott ............................................................................................................................... 254, 260, 264 

Schuster, David M............................................................................................................................................................218 

Scott, Robert C. ...............................................................................................................................................................218 

Seagull Technologies ........................................................................................................................................................106 

Seamless control efectors .................................................................................................................................................295 

Seidel, David A.................................................................................................................................................................218 

Seiner, John M....................................................................................................................................................................52 

Shah, Gautam H. .............................................................................................................................................221, 283, 286 

Shanks, Robert E................................................................................................................................................................38 

Shaped Sonic Boom Demonstration (SSBD) Program .......................................................................................................65 

Shaughnessy, John D..........................................................................................................................................................99 

Shaw, Robert J. ...................................................................................................................................................................50 

Shepherd, Kevin P. .......................................................................................................................................................52, 55 

Shivers, James P. ...............................................................................................................................................................177 

Shock-vector-control method................................................................................................................................... 278, 280 

Shuart, Mark J..................................................................................................................................................................320 

Silva, Walter A......................................................................................................................................................................8 

Single Pilot IFR (SPIFR) project ........................................................................................................................................99 

Sleeman, Jr., William C....................................................................................................................................................174 

Small Aircraft Transportation System (SATS) Program.......................................................................................... 305, 306 

Small, William J. ........................................................................................................................................................78, 146 

Smart Vehicle (SV) Program ............................................................................................................................................294 

Smith, Jr., Charles C................................................................................................................................. 175, 177, 178, 304 

Smith, Ronald H. .............................................................................................................................................................259 

Smith, Stephen C. ................................................................................................................................................... 233, 234 

Smithsonian Air and Space Museum................................................................................................................................257 

Innovation in Flight 365 
INDEX 

Sobieski, Jaroslaw ...............................................................................................................................................................89 

Sonic boom........................................................................................4, 11, 12, 16, 17, 19, 23, 24, 25, 28, 31, 34, 36, 38, 42

 48, 50, 52, 54, 56, 62, 63 

Spanwise blowing .....................................................................................................................................................271, 274 

Spearman, M. Leroy...............................................................................................................................................26, 27, 46 

Spellman, Regina L. .......................................................................................................................................................... 90 

Spiral-Duct vehicle ........................................................................................................................................................... 315 

SR-71........................................................................................................................................................................... 12, 56 

Stack, John P........................................................................................................................................................... 17, 18, 25 

Stanford Research Institute ............................................................................................................................................... 36 

Stanford University.......................................................................................................................................80, 81, 106, 233 

Steiner, Roy ....................................................................................................................................................................... 36 

Stewart, Eric C. ....................................................................................................................................................... 100, 208 

Stickle, Joseph W..............................................................................................................................................................256 

Stone, David G.............................................................................................................................................................39, 40 

Stone, Ralph W...................................................................................................................................................................25 

Strake Technology Research Application to Transport Aircraft (STRATA) ........................................................... 286, 287 

Streett, Craig L......................................................................................................................................................... 153, 155 

Sukhoi ................................................................................................................................................................................69 

Sullivan, Brenda M.......................................................................................................................................................55, 66 

Supercritical airfoil ................................................................................................................... 135, 183, 213, 232, 241, 246 

Superplastic forming and difusion bonding (SPF/DB)................................................................................................45, 48 

Supersonic Aerospace International (SAI) ..........................................................................................................................69 

Supersonic business jets (SBJ)..........................................................................................17, 48, 62, 63, 65, 69, 70, 255, 268 

Supersonic civil aircraft ........................................................................................................................................................7 

Supersonic commercial air transport (SCAT) confgurations............................................................................................ 26 

Supersonic Cruise Aircraft Research (SCAR) Program..............................................................................................40, 255 

Supersonic Cruise and Maneuver Prototype (SCAMP)............................................................................................252, 255 

Supersonic Cruise Integrated Fighter (SCIF) Program............................................................................................. 251, 252 

Supersonic Cruise Research (SCR) Program ................................................................................................................16, 40 

Supersonic Cruise Technology............................................................................................................................................15 

Supersonic laminar fow control (SLFC) ............................................................................................................ 58, 155, 156 

Surcharge......................................................................................................................................................................14, 52 

Swihart, John M.................................................................................................................................................................25 

Synthetic Vision Program.................................................................................................................................................. 60 

Synthetic vision systems (SVS) ...........................................................................................................................................93 

T-2 airplane ......................................................................................................................................................................183 

366 Innovation in Flight 
INDEX 

Tail bufet.................................................................................................................................................................193, 221 

TailFan concept........................................................................................................................................................ 313, 314 

Taxiway Navigation and Situational Awareness (T-NASA) system ..................................................................................103 

Tel Aviv University ...........................................................................................................................................................295 

Teledyne-Ryan BQM-34 Firebee II.............................................................................................................55, 213, 214, 215 

Tenney, Darrel R. ...................................................................................................................................................... 84, 238 

Tetrahedral Unstructured Software System (TetrUSS) ........................................................................................... 238, 290 

Te Technical Cooperation Program (TTCP)......................................................................................................... 223, 225 

Tomas, James L. .......................................................................................................................................................88, 174 

Tomas, Mitchel E. ......................................................................................................................................................... 309 

Tomas, Russell H....................................................................................................................................................312, 313 

Troat-shifting method of fuidic vectoring..................................................................................................................... 280 

Trust vectoring ................................................................................................... 42, 91, 269, 270, 271, 277, 278, 283, 295 

Titanium .......................................................................................................................10, 23, 27, 28, 39, 45, 138, 143, 156 

Toll, Tomas A. ................................................................................................................................................ 25, 27, 39, 40 

Total In-Flight Simulator (TIFS) airplane..................................................................................................42, 103, 106, 107 

Trujillo, Bianca M. ...........................................................................................................................................................140 

T-tail............................................................................................................................................................. 30, 69, 175, 179 

Tu-144 .......................................................................................................................................................... 7, 13, 14, 59, 60 

Tulinius, Jan .....................................................................................................................................................................291 

Tumbling..........................................................................................................................................................74, 86, 87, 88 

Tupolev.............................................................................................................................................................................. 60 

Turner, Tomas R.....................................................................................................................................................172, 182 

U.S. Air Force................................................................................................................25, 36, 103, 143, 166, 193, 251, 291 

U.S. Air Force Load Alleviation and Mode Stabilization (LAMS) Program ....................................................................193 

U.S. Department of Agriculture........................................................................................................................................ 36 

U.S. SST Program ..............................................................................................................................25, 26, 28, 50, 68, 251 

U-2 airplane......................................................................................................................................................................125 

Uninhabited Air Combat Vehicles ...................................................................................................................................298 

United Airlines .................................................................................................................................................................112 

University of Florida.......................................................................................................................................................... 80 

University of Kansas.................................................................................................................................................209, 227 

University of Minnesota ...................................................................................................................................................281 

University of Southern California ..................................................................................................................................... 80 

Unmanned air vehicles (UAVs)...........................................................................................................................56, 239, 313 

Upper surface blowing (USB) concept..............................................................................................................................163 

USM3D code .............................................................................................................................................................88, 255 

Innovation in Flight 367 
INDEX 

Vapor-screen fow-visualization technique............................................................................................................... 260, 262 

Variable Cycle Engine (VCE) Program.............................................................................................................................. 44 

variable-sweep............................................................................................................................... 26, 27, 28, 30, 31, 33, 140 

Variable-Sweep Transition Flight Experiment (VSTFE) ..........................................................................................140, 141 

Vehicle Systems Program.................................................................................................................................... 70, 312, 317 

Vehicle Systems Program (VSP) .................................................................................................................................. 62, 63 

Verstynen, Harry A. ................................................................................................................................................. 110, 112 

Vertical ride control (VRC)..............................................................................................................................................210 

Vicroy, Dan D. ................................................................................................................................................. 85, 86, 87, 91 

ViGYAN Research Associates, Inc. ..................................................................................................................................254 

Viken, Sally A.................................................................................................................................................................. 290 

Virginia Air and Space Center..........................................................................................................................................265 

Visconte, Fioravante .........................................................................................................................................................132 

Vision for Space Exploration ..............................................................................................................................................70 

von Doenhof, Albert E. ...................................................................................................................................................132 

Vortex fap concept...........................................................................................................................................................247 

Vortex Flow Aerodynamics Conference............................................................................................................................256 

vortex lift .................................................................................................................................................. 247, 248, 271, 274 

Vortex-fow control.................................................................................................................................................. 268, 270 

Waggoner, Edgar G. .........................................................................................................................................................141 

Wagner, Richard D....................................................................................................................136, 138, 139, 152, 153, 155 

Wahls, Richard A. ..............................................................................................................................................................57 

Wallops Flight Facility......................................................................................................................................................257 

Watkins, A. Neal ................................................................................................................................................................89 

Watkins, Vernon E. .........................................................................................................................................................153 

Watson, Carolyn B. ........................................................................................................................................................... 34 

Wazak, Martin R..............................................................................................................................................................216 

Wetmore, Joseph W............................................................................................................................................................25 

Whitcomb, Richard T. ................................................................................................................................... 18, 26, 27, 183 

White, E. Richard ............................................................................................................................................................231 

White, III, John J. ..............................................................................................................................................................98 

Whitehead, Jr., Allen H......................................................................................................................................................50 

Whitten, James B. ..............................................................................................................................................................25 

Wie, Y. S...........................................................................................................................................................................153 

Wieseman, Carol D. .........................................................................................................................................................216 

Wilhite, Alan W. ................................................................................................................................................................53 

Willis, Conrad M. ............................................................................................................................................................179 

368 Innovation in Flight 
INDEX 

Wimpress, John K. ..........................................................................................................................................................181 

Wing leading-edge extension (LEX)................................................................................................................................ 220 

Wing, David J.......................................................................................................................................................... 278, 280 

Wing-store futter suppression ..........................................................................................................................................197 

Wlezien, Richard W. .................................................................................................................................................. 65, 153 

Wolkovitch, Julian....................................................................................................................................227, 231, 234, 246 

Woods-Vedeler, Jessica A. .................................................................................................................................................216 

Wright, Howard T............................................................................................................................................................134 

Wright, Jr., Andrew S. ......................................................................................................................................................138 

WS-110A project ................................................................................................................................................................21 

Wyle Laboratories...............................................................................................................................................................65 

X-1......................................................................................................................................................................................18 

X-15 ....................................................................................................................................................................................19 

X-21..................................................................................................................................................................132, 133, 142 

X-22................................................................................................................................................................................. 304 

X-30....................................................................................................................................................................................17 

X-35..................................................................................................................................................................................225 

X-43A (Hyper X) Program...........................................................................................................................................245, 7 

X-48A................................................................................................................................................................................ 84 

XB-70 .....................................................................................................................................................................21, 22, 23 

YC-14 .......................................................................................................................................................................168, 181 

YC-15.................................................................................................................................................................167, 184, 185 

Yetter, Jefery A................................................................................................................................................ 236, 239, 240 

YF-16............................................................................................................................................................................... 200 

YF-17........................................................................................................................................................................ 197, 199 

Yip, Long P. ......................................................................................................................................................254, 255, 257 

YO-3A airplane...................................................................................................................................................................56 

Young, Steven D................................................................................................................................. 98, 104, 105, 112, 114 

Innovation in Flight 369 

NASA HISTORY SERIES 

Tis is a list of the various titles published in the NASA History Series. Many of these works, unfortunately, are no 

longer in print. Copies, however, are available in many Government Documents Sections at major university and 

public libraries through out the United States. Te out of print books are noted. 

Publications that are in print are available for sale from the NASA Information Center, Code CI-4, NASA Headquarters, Washington, DC 20546, or by calling 202-358-0000. To view a complete list of publications available 

through the NASA Information Center, go to http://history.nasa.gov/series95.html. Some NASA History books 

are also available for purchase through the Government Printing Ofce and are noted as such. NASA History 

Monographs are available at no cost with a self-adddressed, stamped envelope. 

NASA Dryden also distributes its titles directly. A listing of these titles and information on ordering them may be 

found at http://www.nasa.gov/centers/dryden/history/Publications/index.html 

Links are included to those publications which we have put on-line. Also included in this list are titles in the New 

Series in NASA History that John Hopkins University Press publishes. 

Many of these publications are available through the Government Printing Ofce (GPO) or the NASA Center for 

AeroSpace Information (CASI) as well. Te ordering information for the GPO can be found at GPO’s web site at 

www.gpo.gov. Te ordering information for CASI can be found here or at the Science and Technical Information 

(STI) web site at www.sti.nasa.gov. 

Please visit www.klabs.org for additional materials on engineering and digital logic technologies for space fight 

applications. Among other topics, this site focuses on Apollo, the Space Shuttle, and Skylab. 

To view online versions, go to http://history.nasa.gov/series95.htmll. 

Reference Works, NASA SP-4000: 

* Grimwood, James M. Project Mercury: A Chronology. NASA SP-4001,1963. 

Out of print. Online version available. 

* Grimwood, James M., and Barton C. Hacker, with Peter J. Vorzimmer. Project Gemini Technology and 

Operations: A Chronology. NASA SP-4002,1969. Out of print. Online version available. 

* Link, Mae Mills. Space Medicine in Project Mercury. NASA SP-4003, 1965. Out of print. 

Online version available. 

* Astronautics and Aeronautics, 1963: Chronology of Science, Technology,and Policy. NASA SP-4004, 1964. 

Out of print. 

* Astronautics and Aeronautics, 1964: Chronology of Science, Technology,and Policy. NASA SP-4005, 1965. 

Out of print. 

* Astronautics and Aeronautics, 1965: Chronology of Science, Technology,and Policy. NASA SP-4006, 1966. 

Out of print. 

* Astronautics and Aeronautics, 1966: Chronology of Science, Technology,and Policy. NASA SP-4007, 1967. 

Out of print. 

Innovation in Flight 371 
 

 

 

 

 

 

NASA HISTORY SERIES 

* Astronautics and Aeronautics, 1967: Chronology of Science, Technology, and Policy. NASA SP-4008, 1968. 

Out of print. 

* Ertel, Ivan D., and Mary Louise Morse. Te Apollo Spacecraft: A Chronology,Volume I, Trough November 7, 

1962. NASA SP-4009, 1969. Out of print. Online version available. 

* Morse, Mary Louise, and Jean Kernahan Bays. Te Apollo Spacecraft: A Chronology, Volume II, November 8, 

1962-September 30, 1964. NASA SP-4009, 1973. Out of print. Online version available. 

* Brooks, Courtney G., and Ivan D. Ertel. Te Apollo Spacecraft: A Chronology, Volume III, October 1, 1964-

January 20, 1966. NASA SP-4009, 1973. Out of print. Online version available. 

* Ertel, Ivan D., and Roland W. Newkirk, with Courtney G. Brooks, Te Apollo Spacecraft: A Chronology, 

Volume IV, January 21, 1966-July 13, 1974. NASA SP-4009, 1978. Out of print. Online version available. 

* Astronautics and Aeronautics, 1968: Chronology of Science, Technology, and Policy. NASA SP-4010, 1969. 

Out of print. 

* Newkirk, Roland W., and Ivan D. Ertel, with Courtney G. Brooks, Skylab: A Chronology. NASA SP-4011, 

1977. To purchase a copy of this book contact the NASA Headquarters Information Center at (202) 358-

0000. Cost: $42.95 NASA HQ Info. Center. Online version available. 

* V an Nimmen, Jane, and Leonard C. Bruno, with Robert L. Rosholt. NASA Historical Data Book, Vol. I: 

NASA Resources, 1958-1968. NASASP-4012, 1976, rep. ed. 1988. To purchase a hardcover copy of this book 

contact the NASA Headquarters Information Center. Cost: $19.00 NASA HQ Info. Center A set of the frst 

three NASA Historical Data Books is available for $55.00 

* Ezell, Linda Neuman. NASA Historical Data Book, Vol II: Programs and Projects, 1958-1968. NASA SP4012, 1988. To purchase a hardcover copy of this book contact the NASA Headquarters Information Center. 

Cost: $19.00 NASA HQ Info. Center A set of the frst three NASA Historical Data Books is available 

for $55.00 

* Ezell, Linda Neuman. NASA Historical Data Book, Vol. III: Programs and Projects, 1969-1978. NASA SP4012, 1988. To purchase a hardcover copy of this book contact the NASA Headquarters Information 

Center. Cost: $19.00 NASA HQ Info. Center A set of the frst three NASA Historical Data Books is available 

for $55.00. Online version available. 

* Gawdiak, Ihor, with Helen Fedor. NASA Historical Data Book, Vol. IV: NASA Resources, 1969-1978. NASA 

SP-4012, 1994. To purchase a hardcover copy of this book contact the HASA Headquarters Information 

Center. Cost: $28.00 NASA HQ Info. Center. Online version available. 

* Rumerman, Judy A. NASA Historical Data Book, Vol. V: NASA LaunchSystems, Space Transportation, Hu 

man Spacefight, and Space Science, 1979-1988. NASA SP-4012, 1999. To purchase a hardcover copy of this 

book contact the Government Printing Ofce. Order GPO stock number: 033-000-01211-0.Cost: $43.00. 

GPO Order Form. Online version available. 

* Rumerman, Judy A. NASA Historical Data Book, Vol. VI: Space Applications, Aeronautics, and other topics, 

1979-1988. NASA SP-4012,1999. To purchase a hardcover copy of this book contact the Government Print 

ing Ofce. Order GPO stock number: 033-000-01222-5. Cost: $46.00. GPO Order Form. 

Online version available. 

* Astronautics and Aeronautics, 1969: Chronology of Science, Technology, and Policy. NASA SP-4014, 1970. 

Out of print. 

* Astronautics and Aeronautics, 1970: Chronology of Science, Technology, and Policy. NASA SP-4015, 1972. 

Out of print. 

372 Innovation in Flight 
 

 

NASA HISTORY SERIES 

* Astronautics and Aeronautics, 1971: Chronology of Science, Technology, and Policy. NASA SP-4016, 1972. 

Out of print. 

* Astronautics and Aeronautics, 1972: Chronology of Science, Technology, and Policy. NASA SP-4017, 1974. To 

purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $9.50 

NASA HQ Info. Center 

* Astronautics and Aeronautics, 1973: Chronology of Science, Technology, and Policy. NASA SP-4018, 1975. To 

purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $9.50 

NASA HQ Info. Center 

* Astronautics and Aeronautics, 1974: Chronology of Science, Technology, and Policy. NASA SP-4019, 1977. To 

purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $9.50 

NASA HQ Info. Center 

* Astronautics and Aeronautics, 1975: Chronology of Science, Technology, and Policy. NASA SP-4020, 1979. To 

purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $9.50 

NASA HQ Info. Center 

* Astronautics and Aeronautics, 1976: Chronology of Science, Technology, and Policy. NASA SP-4021, 1984. To 

purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $10.50 

NASA HQ Info. Center 

* Astronautics and Aeronautics, 1977: Chronology of Science, Technology, and Policy. NASA SP-4022, 1986. To 

purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $10.50 

NASA HQ Info. Center 

* Astronautics and Aeronautics, 1978: Chronology of Science, Technology, and Policy. NASA SP-4023, 1986. To 

purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $11.50 

NASA HQ Info. Center 

* Astronautics and Aeronautics, 1979-1984: Chronology of Science, Technology, and Policy. NASA SP-4024, 1988. 

To purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $11.50 

NASA HQ Info. Center 

* Astronautics and Aeronautics, 1985: Chronology of Science, Technology, and Policy. NASA SP-4025, 1990. To 

purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $12.50 

NASA HQ Info. Center 

* Noordung, Hermann. Te Problem of Space Travel: Te Rocket Motor. Edited by 1Ernst Stuhlinger and J.D. 

Hunley, with Jennifer Garland. NASA SP-4026, 1995. Tis Out of print . Online version available. 

* Gawdiak, Ihor Y., Ramon J. Miro, and Sam Stueland, comps. Astronauticsand Aeronautics, 1986-1990: A 

Chronology. NASA SP-4027, 1997. To purchase a paperback copy of this book contact the Government Print 

ing Ofce. Order GPO Stock Number #033-000-01180-6 $21.00 GPO Order Form 

* Gawdiak, Ihor Y. and Shetland, Charles. Astronautics and Aeronautics, 1990-1995: A Chronology. NASA SP2000-4028, 2000. To purchase a paperback copy of this book contact the Government Printing Ofce. 

Order GPO Stock Number #033-000-01230-6 $43.00 GPO Order Form 

* Orlof, Richard W. Apollo by the Numbers: A Statistical Reference. NASA SP-2000-4029, 2000. To purchase 

a paperback copy of this book contact the Government Printing Ofce. Order GPO Stock Number #033-

000-01236-5 $40.00 GPO Order Form. Online version available. Te online version includes all the extensive 

text and useful tables of the hard copy edition. Te author has also made a number of corrections to the 

data in the hard copy edition. Te online version does not include the original photos. 

Innovation in Flight 373 
 

 

 

NASA HISTORY SERIES 

Management Histories, NASA SP-4100: 

* Rosholt, Robert L. An Administrative History of NASA, 1958-1963. NASASP-4101, 1966. Out of print. 

* Levine, Arnold S. Managing NASA in the Apollo Era. NASA SP-4102,1982. To purchase a copy of this book 

contact the NASA Headquarters Information Center.Cost: $10.00 NASA HQ Info. Center. 

Online version available. 

* Roland, Alex. Model Research: Te National Advisory Committee for Aeronautics,1915-1958. NASA SP4103, 1985. To purchase a hard cover copy of this book contact the NASA Headquarters Information Center. 

Cost:$32.00 NASA HQ Info. Center . Online version available. 

* Fries, Sylvia D. NASA Engineers and the Age of Apollo. NASA SP-4104,1992. Out of print. 

Online version available. 

* Glennan, T. Keith. Te Birth of NASA: Te Diary of T. Keith Glennan. Edited by J.D. Hunley. NASA SP4105, 1993. To purchase a hardcover copy of this book contact the Government Printing Ofce. Order GPO 

Stock Number #033-000-01131-8 $32.00 GPO Order Form 

* Seamans, Robert C. Aiming at Targets: Te Autobiography of Robert C. Seamans. NASA SP-4106, 1996. Tis 

hardcover book is available by calling the Government Printing Ofce at 202-512-1800 and ordering Stock 

Number 033-000-01175-0 $25.00 GPO Order Form. 

* Garber, Stephen J., editor. Looking Backward, Looking Forward: Forty Years of Human Spacefight Sympo 

sium. NASA SP-2002-4107. Tis hardcover book is available by calling the Government Printing Ofce at 

202-512-1800 and ordering Stock Number 033-000-01249-7 $25.00 GPO Order Form. 

Online version available. 

* Mallick, Donald L. with Peter W. Merlin. Te Smell of Kerosene: A Test Pilot’s Odyssey . NASA SP-4108. Tis 

hardcover book is available by calling the Government Printing Ofce at 202-512-1800 and ordering Stock 

Number 033-000-01270-5 $22.00 GPO Order Form. 

* Ilif, Kenneth W. and Curtis L. Peebles. From Runway to Orbit: Refections of a NASA Engineer . NASA SP2004-4109. Tis hardcover book is available by calling the Government Printing Ofce at 202-512-1800 and 

ordering Stock Number 033-000-01267-5 $55.00 GPO Order Form. 

* Chertok, Boris. Rockets and People, Volume 1. (NASA SP-2005-4110). Please order by contacting the NASA 

Center for Aerospace Information at 7121 Standard Drive Hanover, Maryland 21076, (301) 621-0390 or 

Online version available. Please mention the title and NASA Report #NASASP20054110. Te price code is 

A03 ($27.50 within the U.S. plus $2 shipping and handling.) 

* Laufer, Alexander, Post, Todd, and Hofman, Edward. Shared Voyage: Learning and Unlearning from Remark 

able Projects (NASA SP-2005-4111). Please order by contacting the NASA Center for Aerospace Information 

at 7121 Standard Drive Hanover, Maryland 21076, (301) 621-0390 or . Online version available. Please men 

tion the title, and NASA Report #NASASP20054111. Te price code is A03 ($27.50 within the U.S. plus $2 

shipping and handling.) 

Project Histories, NASA SP-4200: 

* Swenson, Loyd S., Jr., James M. Grimwood, and Charles C. Alexander. Tis New Ocean: A History of Project 

Mercury. NASA SP-4201, 1966, reprinted 1999. . Online version available.Tis book is also available by 

calling the Government Printing Ofce at 202-512-1800 and ordering Stock Number 033-000-01210-1. 

$46.00 GPO Order Form 

* Green, Constance McLaughlin, and Milton Lomask. Vanguard: A History. NASA SP-4202, 1970; rep. ed. 

Smithsonian Institution Press, 1971. Out of print. Online version available. 

374 Innovation in Flight 
 

 

 

NASA HISTORY SERIES 

* Hacker, Barton C., and James M. Grimwood. On Shoulders of Titans: A History of Project Gemini. NASA SP4203, 1977, reprinted 2002. Tis book is available by calling the Government Printing Ofce at 202-512-

1800 and ordering Stock Number 033-000-01242-0. $47.00 GPO Order Form . Online version available. 

* Benson, Charles D. and William Barnaby Faherty, Moonport: A History of Apollo Launch Facilities and Opera 

tions. NASA SP-4204, 1978. Te SP edition is Out of print, but the University Press of Florida has 

republished the book in two volumes, Gateway to the Moon and Moon Launch! . Online version available. 

* Brooks, Courtney G., James M. Grimwood, and Loyd S. Swenson, Jr. Chariots for Apollo: A History of Manned 

Lunar Spacecraft. NASA SP- 4205, 1979. Out of print. . Online version available. 

* Bilstein, Roger E. Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles. NASA SP4206, 1980 and 1996. Tis SP version is Out of print, but it has been reprinted by the University Press of 

Florida, please see below. Online version available. 

* Compton, W. David, and Charles D. Benson. Living and Working in Space:A History of Skylab. NASA SP4208, 1983. To purchase a hardcover copy of this book contact the NASA Headquarters Information Center. 

Cost: $20.00 NASA HQ Info. Center. Online version available. 

* Ezell, Edward Clinton, and Linda Neuman Ezell. Te Partnership: A History of the Apollo-Soyuz Test Project. 

NASA SP-4209, 1978. Out of print. Online version available. 

* Hall, R. Cargill. Lunar Impact: A History of Project Ranger. NASA SP-4210, 1977. Out of print. 

Online version available. 

* Newell, Homer E. Beyond the Atmosphere: Early Years of Space Science. NASA SP-4211, 1980. Online version 

available.To purchase a paperback copy of this book contact the NASA Headquarters Information Center. 

Cost: $15.00 NASA HQ Info. Center 

* Ezell, Edward Clinton, and Linda Neuman Ezell. On Mars: Exploration of the Red Planet, 1958-1978. NASA 

SP-4212, 1984. Out of print. Online version available. 

* Pitts, John A. Te Human Factor: Biomedicine in the Manned Space Program to 1980. NASA SP-4213, 1985. 

To purchase a paperback copy of this book contact the NASA Headquarters Information Center. Cost: $19.00 

NASA HQ Info. Center. Tis book is also available online. 

* Compton, W. David. Where No Man Has Gone Before: A History of Apollo Lunar Exploration Missions. NASA 

SP-4214, 1989. . Online version available.To purchase a paperback copy of this book contact the Government 

Printing Ofce. Order GPO Stock Number #033-000-01047-8$25.00 GPO Order Form 

* Naugle, John E. First Among Equals: Te Selection of NASA Space ScienceExperiments NASA SP-4215, 1991. 

Online version available. To purchase a copy of this book contact the NASAHeadquarters Information 

Center. Cost: $8.00 NASA HQ Info. Center 

* Wallace, Lane E. Airborne Trailblazer: Two Decades with NASA Langley’s737 Flying Laboratory. NASA SP4216, 1994. . Online version available. To purchase a paperback copy of this book contact the Government 

Printing Ofce. Order GPO Stock Number #033-000-01140-7$27.00 GPO Order Form 

* Butrica, Andrew J. Beyond the Ionosphere: Fifty Years of Satellite Communications. NASA SP-4217, 1997. To 

purchase a hardcover copy of this book contact the Government Printing Ofce. Order GPO Stock 

Number#033-000-01178-4. $31.00 GPO Order Form. Online version available. 

* Butrica, Andrew J. To See the Unseen: A History of Planetary Radar Astronomy. NASA SP-4218, 1996. To pur 

chase a hardcover copy of this book contact the Government Printing Ofce. Order GPO Stock Number 

#033-000-01163-6$26.00 GPO Order Form 

Innovation in Flight 375 
 

 

 

 

 

 

NASA HISTORY SERIES 

* Mack, Pamela E., ed. From Engineering Science to Big Science: Te NACA and NASA Collier Trophy Research 

Project Winners. NASA SP-4219,1998. To purchase a copy of this book contact the Government Printing 

Ofce. Order GPO Stock Number #033-000-01199-7 $35.00 GPO Order Form. Online version available. 

* Reed, R. Dale. Wingless Flight: Te Lifting Body Story. NASASP-4220, 1998. To purchase a hardcover copy 

of this book contact the Government Printing Ofce. Order GPO Stock Number #033-000-01191-1 $25.00 

GPO Order Form Wingless Flight is now also available in paperback from Te University Press of Kentucky. 

Click here to order. 

* Heppenheimer, T. A. Te Space Shuttle Decision: NASA’s Search for a Reusable Space Vehicle. NASA SP-4221, 

1999. To purchase a copy of this book contact the Government Printing Ofce. Order GPO Stock Number 

#033-000-01215-2 $23.00 GPO Order Form. Online version available. 

* Hunley, J. D., ed. Toward Mach 2: Te Douglas D-558 Program. NASA SP-4222, 1999. Online version 

available. To purchase a copy of this book contact the Government Printing Ofce. Order GPO Stock 

Number #033-000-01208-0 $18.00 GPO Order Form 

* Swanson, Glen E., ed. “Before Tis Decade is Out...” Personal Refections on the Apollo Program. NASA SP4223, 1999. To purchase a copy of this book contact the Government Printing Ofce. Order GPO Stock 

Number #033-000-01216-1$38.00 GPO Order Form. Alternately, this book has also been printed by the 

University Press of Florida and can be ordered here as well. Online version available. 

* Tomayko, James E. Computers Take Flight: A History of NASA’s Pioneering Digital Fly-By-Wire Project NASA 

SP-4224, 2000. To purchase a copy of this book contact the Government Printing Ofce. Order GPO Stock 

Number#033-000-01220-9 $26.00 GPO Order Form. Online version available. 

* Leary, William M. We Freeze to Please: A History of NASA’s Icing Research Tunnel and the Quest for Safety. 

NASA SP-2002-4226, 2002. To purchase a copy of this book contact the Government Printing Ofce. Order 

GPO Stock Number #033-000-01244-6 $28.00. GPO Order Form. 

* Mudgway, Douglas J. Uplink-Downlink: A History of the Deep Space Network, 1957-1997 . NASA SP-2001-

4227. To purchase a copy of this book contact the Government Printing Ofce. Order GPO Stock Number 

#033-000-01241-1 $26.00 GPO Order Form. Online version available. 

* Dawson, Virginia P. and Mark D. Bowles. Taming Liquid Hydrogen: Te Centaur Upper Stage Rocket, 1958-

2002 . NASA SP-2004-4230. To purchase a copy of this book contact the Government Printing Ofce. 

Order GPO Stock Number #033-000-01271-3 $28.00 GPO Order Form. 

Center Histories, NASA SP-4300: 

* Rosenthal, Alfred. Venture into Space: Early Years of Goddard Space Flight Center. NASA SP-4301, 1985. 

Out of print. 

* Hartman, Edwin, P. Adventures in Research: A History of Ames Research Center, 1940-1965. NASA SP-4302, 

1970. Out of print. Online version available. 

* Hallion, Richard P. On the Frontier: Flight Research at Dryden, 1946-1981. NASA SP-4303, 1984. To pur 

chase a hardcover copy of this book contact the NASA Headquarters Information Center. 

Cost: $18.00 NASA HQ Info. Center 

* Muenger, Elizabeth A. Searching the Horizon: A History of Ames Research Center, 1940-1976. NASA SP4304, 1985. To purchase a paperback copy of this book contact the NASA Headquarters Information Center. 

Cost:$13.00 NASA HQ Info. Center. . Online version available. 

* Hansen, James R. Engineer in Charge: A History of the Langley Aeronautical Laboratory,1917-1958. NASA 

376 Innovation in Flight 
 

NASA HISTORY SERIES 

SP-4305, 1987. To purchase a paperback copy of this book contact the NASA Headquarters Information 

Center. Cost: $30.00 NASA HQ Info. Center. Online version available. 

* Dawson, Virginia P. Engines and Innovation: Lewis Laboratory and American Propulsion Technology. NASA 

SP-4306, 1991. To purchase a paperback copy of this book contact the Government Printing Ofce. Order 

GPO Stock Number #033-000-01095-8 $16.00 GPO Order Form. Online version available. 

* Dethlof, Henry C. “Suddenly Tomorrow Came...”: A History of the Johnson Space Center, 1957-1990. NASASP4307, 1993. To purchase a hardcover copy of this book contact the Government Printing Ofce. Order GPO 

Stock Number #033-000-01134-2 $36.00 GPO Order Form. Online version available. 

* Hansen, James R. Spacefight Revolution: NASA Langley Research Center from Sputnik to Apollo. NASA SP4308, 1995. To purchase a paperback copy of this book contact the Government Printing Ofce. Order GPO 

Stock Number#033-000-01149-1 $30.00 GPO Order Form. Online version available. 

* Wallace, Lane E. Flights of Discovery: An Illustrated History of the Dryden Flight Research Center. NASA SP4309, 1996. To purchase a hardcover copy of this book contact the Government Printing Ofce. Order GPO 

Stock Number #033-000-01167-9 $42.00 GPO Order Form. 

* Herring, Mack R. Way Station to Space: A History of the John C. Stennis Space Center. NASA SP-4310, 1997. 

To purchase a hardcover copy of this book contact the Government Printing Ofce. Order GPO Stock 

Number #033-000-01185-7$37.00 GPO Order Form 

* Wallace, Harold D., Jr. Wallops Station and the Creation of an American Space Program. NASA SP-4311, 1997. 

To purchase a copy of this softcover book contact the Government Printing Ofce. Order GPO Stock 

Number #033-000-01186-5$11.00 GPO Order Form 

* W allace, Lane E. Dreams, Hopes, Realities. NASA’s Goddard Space Flight Center: Te First Forty Years. NASA 

SP-4312, 1999. To purchase a copy of this softcover book contact the Government Printing Ofce. Order 

GPO Stock Number #033-000-01206-3 $33.00 GPO Order Form 

* Dunar, Andrew J. and Waring, Stephen P. Power to Explore: A History of Marshall Space Flight Center, 1960-

1990 NASA SP-4313, 1999. To purchase a copy of this hardcover book contact the Government Printing Of 

fce. Order GPO Stock Number #033-000-01221-7 $49.00 GPO Order Form . Online version available. 

* Bugos, Glenn E. Atmosphere of Freedom: Sixty years at the NASA Ames Research Center NASA SP-2000-4314, 

2000.To purchase a copy of this richly illustrated, softcover book contact the Government Printing Ofce. 

Order GPO Stock Number #033-000-01225-0 $39.00 GPO Order Form. Online version available. 

* Schultz, James. Crafting Flight: Aircraft Pioneers and the Contributions of the Men and Women of NASA 

Langley Research Center NASA SP-2003-4316, 2003. To purchase a copy of this softcover book contact the 

Government Printing Ofce. Order GPO Stock Number 033-000-01257-8 $46.00 GPO Order Form. 

General Histories, NASA SP-4400: 

* Corliss, William R. NASA Sounding Rockets, 1958-1968: A Historical Summary. NASA SP-4401, 1971. 

Out of print. Online version available. 

* W ells, Helen T., Susan H. Whiteley, and Carrie Karegeannes. Origins of NASA Names. NASA SP-4402, 

1976. Out of print. Online version available. 

* Anderson, Frank W., Jr. Orders of Magnitude: A History of NACA andNASA, 1915-1980. NASA SP-4403, 

1981. Out of print. 

* Sloop, John L. Liquid Hydrogen as a Propulsion Fuel, 1945-1959. NASASP-4404, 1978. Out of print. Online 

version available. 

Innovation in Flight 377 
 

 

 

NASA HISTORY SERIES 

* Roland, Alex. A Spacefaring People: Perspectives on Early Spacefight. NASA SP-4405, 1985. Out of print. 

* Bilstein, Roger E. Orders of Magnitude: A History of the NACA and NASA, 1915-1990. NASA SP-4406, 1989. 

Out of print. Online version available. 

* Logsdon, John M., ed., with Linda J. Lear, Jannelle Warren Findley, Ray A. Williamson, and Dwayne A. Day. 

Exploring the Unknown: Selected Documents in the History of the U.S. Civil Space Program, Volume I, Organiz 

ing for Exploration. NASA SP-4407, 1995. To purchase a hardcover copy of this book contact the Government 

Printing Ofce. Order GPO Stock Number #033-000-01160-1$43.00 GPO Order Form 

* Logsdon, John M., ed, with Dwayne A. Day, and Roger D. Launius. Exploring the Unknown: Selected Docu 

ments in the History of the U.S. Civil Space Program, Volume II, External Relationships. NASA SP-4407, 1996. 

To purchase a hardcover copy of this book contact the Government Printing Ofce. Order GPO Stock 

Number #033-000-01174-1 $40.00 GPO Order Form 

* Logsdon, John M., ed., with Roger D. Launius, David H. Onkst, and StephenJ. Garber. Exploring the 

Unknown: Selected Documents in the History of the U.S. Civil Space Program, Volume III, Using Space. NASA 

SP-4407,1998. To purchase a hard cover copy of this book contact the Government Printing Ofce. Order 

GPO Stock Number #033-000-01195-4 $41.00 GPO Order Form 

* Logsdon, John M., ed., with Ray A. Williamson, Roger D. Launius, Russell J. Acker, Stephen J. Garber, 

and Jonathan L. Friedman. Exploring the Unknown: Selected Documents in the History of the U.S. Civil Space 

Program,Volume IV, Accessing Space. NASA SP-4407, 1999. To purchase a hard cover copy of this book contact 

the Government Printing Ofce. Order GPO Stock Number #033-000-01219-5 $55.00 GPO Order Form. 

Online version available. 

* Logsdon, John M., ed., with Amy Paige Snyder, Roger D. Launius, Stephen J. Garber, and Regan Anne New 

port. Exploring the Unknown: Selected Documents in the History of the U.S. Civil Space Program,Volume V, 

Exploring the Cosmos. NASA SP-4407, 2001. To purchase a hard cover copy of this book contact the 

Government Printing Ofce. Order GPO Stock Number #033-000-01238-1 $70.00 GPO Order Form. 

Online version available. 

* Logsdon, John M., ed., with Stephen J. Garber, Roger D. Launius, and Ray A. Williamson. Exploring the 

Unknown: Selected Documents in the History of the U.S. Civil Space Program, Volume VI: Space and Earth Science (NASA SP-2004-4407), 2004. Please order by contacting the NASA Center for Aerospace Information at 

7121 Standard Drive Hanover, Maryland 21076, (301) 621-0390 or order online. Please mention the title, 

volume number, and Document ID # 20040095359. Te domestic sales price is $43.00 plus shipping. 

Online version available. 

* Siddiqi, Asif A., Challenge to Apollo: Te Soviet Union and the Space Race, 1945-1974 (NASA SP-2000-4408). 

To purchase a hard cover copy of this book contact the Government Printing Ofce. Order GPO Stock 

Number #033-000-01231-4 $79.00 GPO Order Form Tis book is also available in a two-part series from 

the University Press of Florida. 

* Hansen, James R., ed.. Te Wind and Beyond: Journey into the History of Aerodynamics in America, Volume 1, 

Te Ascent of the Airplane. NASA SP-2003-4409, 2003. To purchase a hard cover copy of this book contact 

the Government Printing Ofce. Order GPO Stock Number #033-000-01268-3 $55.00 GPO Order Form. 

Monographs in Aerospace History (SP-4500 Series): 

Monographs 2 - 32 are available by sending a self-addressed 9x12” envelope for each monograph with appropriate 

postage for 17 ounces (typically $3.95 within the U.S., $5.70 for Canada, and $12.15 for overseas - international 

378 Innovation in Flight 
 

 

 

NASA HISTORY SERIES 

customers are asked to purchase U.S. postage through an outlet such as www.stampsonline.com ) to the NASA 

Headquarters Information Center, Code CI-4, Washington, DC 20546. 

Monographs 25 and 30 are available by sending a self-addressed 8”x11” fat-rate Priority Mail envelope for each 

monograph to the NASA Dryden Flight Research Center History Ofce, Mail Stop 1613, P.O. Box 273, Edwards, 

CA 93523. 

* Launius, Roger D. and Aaron K. Gillette, comps. Toward a History of the Space Shuttle: An Annotated 

Bibliography. Monograph in Aerospace History, No. 1, 1992. Out of print. Tis monograph is available 

online. Online version available. 

* Launius, Roger D., and J.D. Hunley, comps. An Annotated Bibliography of the Apollo Program. Monograph in 

Aerospace History No. 2, 1994. Tis monograph is available online. Online version available. 

* Launius, Roger D. Apollo: A Retrospective Analysis. Monograph in Aerospace History, No. 3, 1994. Tis 

monograph is available online. Online version available. 

* Hansen, James R. Enchanted Rendezvous: John C. Houbolt and the Genesis of the Lunar-Orbit Rendezvous 

Con cept. Monograph in Aerospace History, No. 4, 1995. Tis monograph is available online. 

Online version available. 

* Gorn, Michael H. Hugh L. Dryden’s Career in Aviation and Space. Monograph in Aerospace History, No. 5, 

1996. Online version available. 

* Powers, Sheryll Goecke. Women in Flight Research at NASA Dryden Flight Research Center from 1946 to 1995. 

Monograph in Aerospace History, No. 6, 1997. 

* Portree, David S.F. and Robert C. Trevino. Walking to Olympus: An EVA Chronology. Monograph in 

Aerospace History, No. 7, 1997. Online version available.. 

* Logsdon, John M., moderator. Legislative Origins of the National Aeronautics and Space Act of 1958: 

Proceedings of an Oral History Workshop. Monograph in Aerospace History, No. 8, 1998. 

Online version available. 

* Rumerman, Judy A., comp. U.S. Human Spacefight, A Record of Achievement 1961-1998. Monograph in 

Aerospace History, No. 9, 1998. Online version available. 

* Portree, David S. F. NASA’s Origins and the Dawn of the Space Age. Monograph in Aerospace History, No. 10, 

1998. Online version available. 

* Logsdon, John M. Together in Orbit: Te Origins of International Cooperation in the Space Station. Monograph 

in Aerospace History, No. 11, 1998. . Online version available. 

* Phillips, W. Hewitt. Journey in Aeronautical Research: A Career at NASA Langley Research Center. Monograph 

in Aerospace History, No. 12, 1998. 

* Braslow, Albert L. A History of Suction-Type Laminar-Flow Control with Emphasis on Flight Research 

Monograph in Aerospace History, No. 13, 1999. Online version available. 

* Logsdon, John M., moderator. Managing the Moon Program: Lessons Learned Fom Apollo. Monograph in 

Aerospace History, No. 14, 1999. Online version available. 

* Perminov, V.G. Te Difcult Road to Mars: A Brief History of Mars Exploration in the Soviet Union is 

Monograph in Aerospace History, No. 15, 1999. Online version available. 

* Maisel, Martin, Giulanetti, Demo J., and Dugan, Daniel C. Te History of the XV-15 Tilt Rotor Research 

Aircraft: From Concept to Flight is Monograph in Aerospace History, No. 17, 2000 (NASA SP-2000-4517). 

On line version available. 

Innovation in Flight 379 
 

 

 

 

NASA HISTORY SERIES 

* Jenkins, Dennis R., Hypersonics Before the Shuttle: A Concise History of the X-15 Research Airplane is 

Monograph in Aerospace History, No. 18, 2000 (NASA SP-2000-4518). Online version available. 

* Chambers, Joseph R. Partners in Freedom: Contributions of the Langley Research Center to U.S. Military 

Aircraft of the 1990s is Monograph in Aerospace History, No. 19, 2000 (NASA SP-2000-4519). 

Online version available. 

* Waltman, Gene L. Black Magic and Gremlins: Analog Flight Simulations at NASA’s Flight Research Center is 

Monograph in Aerospace History, No. 20, 2000 (NASA SP-2000-4520). Online version available. 

* Portree, David S.F.. Humans to Mars: Fifty Years of Mission Planning, 1950-2000 is Monograph in Aerospace 

History, No. 21, 2001 (NASA SP-2001-4521). Online version available. 

* Tompson, Milton O. with J.D. Hunley. Flight Research: Problems Encountered and What they Should Teach Us 

is Monograph in Aerospace History, No. 22, 2001 (NASA SP-2001-4522). Online version available. 

* Tucker, Tom. Te Eclipse Project is Monograph in Aerospace History, No. 23, 2001 (NASA SP-2001-4523). 

Online version available. 

* Siddiqi, Asif A. Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000 is 

Monograph in Aerospace History, No. 24, 2002 (NASA SP-2002-4524). Online version available. 

* Merlin, Peter W. Mach 3+: NASA/USAF YF-12 Flight Research, 1969-1979 is Monograph in Aerospace 

History, No. 25, 2001 (NASA SP-2001-4525) . Online version available. 

* Anderson, Seth B. Memoirs of an Aeronautical Engineer: Flight Tests at Ames Research Center: 1940-1970 is 

Monograph in Aerospace History, No. 26, 2002 (NASA SP-2002-4526) 

* Renstrom, Arthur G. Wilbur and Orville Wright: A Bibliography Commemorating the One-Hundredth 

Annversary of the First Powered Flight on December 17, 1903 is Monograph in Aerospace History, No. 27, 2002 

(NASA SP-2002-4527). Online version available. 

* No monograph 28. 

* Chambers, Joseph R. Concept to Reality: Contributions of the NASA Langley Research Center to U.S. Civil 

Aircraft of the 1990s is Monograph in Aerospace History, No. 29, 2003 (SP-2003-4529). 

Online version available. 

* Peebles, Curtis, editor. Te Spoken Word: Recollections of Dryden History, Te Early Years is Monograph in 

Aerospace History, No. 30, 2003 (SP-2003-4530). Online version available. 

* Jenkins, Dennis R., Tony Landis, and Jay Miller. American X-Vehicles: An Inventory- X-1 to X-50 is 

Monograph in Aerospace History, No. 31, 2003 (SP-2003-4531). Online version available. 

* Renstrom, Arthur G. Wilbur and Orville Wright: A Chronology Commemorating the One-Hundredth 

Anniversary of the First Powered Flight on December 17, 1903 is Monograph in Aerospace History, No. 32, 

2002 (NASA SP-2003-4532). Online version available. 

* Bowles, Mark D. and Arrighi, Robert S. NASA’s Nuclear Frontier: Te Plum Brook Research Reactor is 

Monograph in Aerospace History, No. 33, 2003 (SP-2004-4533). Online version available. 

* McCurdy, Howard E. Low Cost Innovation in Spacefight: Te History of the Near Earth Asteroid Rendezvous 

(NEAR) Mission (NASA SP-2005-4536). Online version available. 

* Lambright, W. Henry. NASA and the Environment: Te Case of Ozone Depletion (NASA SP-2005-4538). 

Online version available. 

* Seamans, Robert C. Jr.Project Apollo: Te Tough Decisions (NASA SP-2005-4537). Online version available. 

380 Innovation in Flight 
 

 

 

 

 

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Dryden Historical Studies 

* Tomayko, James E., author, and Christian Gelzer, editor. Te Story of Self-Repairing Flight Control Systems 

is Dryden Historical Study #1. Tis study is available from the Dryden Flight Research Center History Ofce 

by sending a self-addressed 8”x11” fat-rate Priority Mail envelope for each study to the NASA Dryden Flight 

Research Center History Ofce, Mail Stop 1613, P.O. Box 273, Edwards, CA 93523. 

Electronic Media (SP-4600 Series) 

* Remembering Apollo 11: Te 30th Anniversary Data Archive CD-ROM (SP-4601, 1999). Tis CD-ROM is 

available by sending a self-addressed envelope for each CD-ROM set with appropriate postage (typically 

$1.90 within the U.S., $2.30 for Canada, and $5.60 for overseas - international customers are asked to 

purchase U.S. postage through an outlet such as www.stampsonline.com ) to the NASA Headquarters 

Information Center, Mail Code CI-4, 300 E Street SW, Room 1H23, Washington, D.C. 20546-0001 

* Te Mission Transcript Collection: U.S. Human Spacefight Missions from Mercury Redstone 3 to Apollo 17 

(SP-2000-4602, 2001). Now available commerically from CG Publishing. To order send an International 

Money Order for $8.00 to CG Publishing Inc, Box 62034, Burlington, Ontario, L7R 4K2, Canada or 

call 905-637-5737. 

* Shuttle-Mir: the United States and Russia Share History’s Highest Stage (SP-2001-4603, 2002). Tis CD-ROM 

is available from NASA CORE for $5 per copy plus shipping and handling (within the U.S., $6 for up to 

$25 order). To order the CD-ROM, please mail a check, money order or school purchase order to: NASA 

CORE, Lorain County JVS, 15181 Route 58 South, Oberlin, OH 44074, 440-775-1400, toll free 1-866-

776-CORE, FAX 440-775-1460, nasaco@leeca.org, or http://core.nasa.gov on the Web. CORE also

 accepts orders by credit card (VISA or MasterCard). 

* U.S. Centennial of Flight Commission presents Born of Dreams ~ Inspired by Freedom (SP-2004-4604, 2004). 

Tis DVD data disk is available by sending a self-addressed envelope for each DVD with appropriate postage 

(typically $1.90 within the U.S., $2.30 for Canada, and $5.60 for overseas - international customers are asked 

to purchase U.S. postage through an outlet such as www.stampsonline.com ) to the NASA Headquarters 

Information Center, Mail Code CI-4, 300 E Street SW, Room 1H23, Washington, D.C. 20546-0001. 

* Of Ashes and Atoms: A Documentary on the NASA Plum Brook Reactor Facility (NASA SP-2005-4605). Of 

Ashes and Atoms was produced and directed by James Polaczynski and written by him with Robert Arrighi. 

Narrated by Kate Mulgrew (Captain Janeway of the Star Trek Voyager series), this documentary illustrates 

the history behind Plum Brook Reactor Facility, operating from 1962-1973 as one of the frst nuclear test 

reactors built in the United States and the only one built by NASA. While the reactor never reached its full 

potential, the personnel who have worked there made great achievements in terms of scientifc discovery, as 

well as building, operating, and safely deconstructing a nuclear reactor. Plum Brook’s rich history has 

signifcant lessons in terms of management, environmental stewardship, painstaking engineering, and 

scientifc investigation. Tis DVD is available by sending a self-addressed envelope for each CD with 

appropriate postage (typically $1.90 within the U.S., $2.30 for Canada, and $5.60 for overseas - international 

customers are asked to purchase U.S. postage through an outlet such as www.stampsonline.com ) to the 

NASA Headquarters Information Center, 300 E Street SW, Room 1H23, Washington, D.C. 20546-0001, 

202-358-0000. 

* Taming Liquid Hydrogen : Te Centaur Upper Stage Rocket Interactive CD-ROM. (SP-2004-4606, 2004). 

Tis CD-ROM is available by sending a self-addressed envelope for each CD-ROM set with appropriate 

Innovation in Flight 381 
 

 

 

NASA HISTORY SERIES 

postage (typically $1.90 within the U.S., $2.30 for Canada, and $5.60 for overseas - international customers 

are asked to purchase U.S. postage through an outlet such as www.stampsonline.com ) to the NASA 

Headquarters Information Center, Mail Code CI-4, 300 E Street SW, Room 1H23, Washington, D.C. 

20546-0001. 

* Fueling Space Exploration: Te History of NASA’s Rocket Engine Test Facility DVD (NASA SP-2005-4607). 

Tis DVD contains a 25-minute and a condensed 7-minute documentary video on the RETF, which used 

to be a part of the NASA Glenn Research Center. RETF employees performed pioneering research from 

1957 to 1995 on liquid hydrogen propulsion on the Centaur and Saturn rockets, as well as the Space Shuttle. 

Declared a National Historic Landmark in 1984, the RETF ofcially closed in 1995 and was torn down in 

2003 to make way for the Cleveland airport’s expansion. Tis DVD is available by sending a self-addressed 

envelope for each CD with appropriate postage (typically $1.90 within the U.S., $2.30 for Canada, and 

$5.60 for overseas - international customers are asked to purchase U.S. postage through an outlet such as 

www.stampsonline.com ) to the NASA Headquarters Information Center, 300 E Street SW, Room 1H23, 

Washington, D.C. 20546-0001, 202-358-0000. 

Historical Reports (NASA HHR) 

* NASA Ofce of Defense Afairs: Te First Five Years (HHR-32, 1970) by W. Fred Boone. Admiral Boone 

led the Ofce of Defense Afairs from December 1, 1962 through January 1, 1968, a formative early period 

in space history when cooperation between NASA, a civilian agency, and the military was especially 

important. Tis signifcant narrative charts these early eforts in coordination. Special thanks to volunteer 

Chris Gamble for scanning and formatting this book for the Web. . Online version available. 

* Research in NASA History: A Guide to the NASA History Program. NASA HHR-64, revised June 1997. Tis 

monograph-sized publication is available by sending a stamped (for 8 ounces), self-addressed 9x12 inch 

envelope to the NASA History Division, Code IQ, Washington, DC 20546. . Online version available. 

NASA Special Reports (NASA SP-4900) 

* Unmanned Space Project Management: Surveyor and Lunar Orbiter. Washington,D.C.:NASA SP-4901, 1972. 

By Erasmus H. Kloman. NASA commissioned the National Academy of Public Administration to undertake 

this study to look at its innovative management techniques on these complex technological projects. 

Out of print. Online version available. 

Other NASA Special Publications 

(not in the formal NASA History Series) 

* Results of the Second Manned Suborbital Space Flight, July 21, 1961. NASA, 1961. Out of print. 

Online version available. 

* Te Impact of Science on Society. NASA SP-482 by James Burke, Jules Bergman, and Isaac Asimov, 1985. 

Online version available. 

* Space Station Requirements and Transportation Options for Lunar Outpost. NASA, 1990. 

Online version available. 

* Space Station Freedom Accommodation of the Human Exploration Initiative. NASA, 1990. 

Online version available. 

* Why Man Explores. NASA EP-125, 1976. 

382 Innovation in Flight 
NASA HISTORY SERIES 

* Results of the Second Manned Suborbital Space Flight, July 21, 1961. NASA, 1961. Out of print. 

Online version available. 

* Apollo 13 “Houston, we’ve got a problem.” NASA EP-76, 1970. Out of print. 

Online version available. 

* Results of the Second U.S. Manned Orbital Space Flight. NASA SP-6, 1962. Out of print. 

Online version available. 

* Results of the Tird U.S. Manned Orbital Space Flight. NASA SP-12, 1962. Out of print. 

Online version available. 

* MercuryProject Summary including Results of the Fourth Manned Orbital Flight. NASA SP-45, 1963. 

Out of print. Online version available. 

* X-15 Research Results With a Selected Bibliography. NASA SP-60, 1965. Out of print. 

Online version available. 

* Exploring Space with a Camera. NASA SP-168, 1968. Online version available. 

* Aerospace Food Technology. NASA SP-202, 1969. Online version available. 

* What Made Apollo a Success? NASA SP-287, 1971. Online version available. 

* Evolution of the Solar System NASA SP-345, 1976. Online version available. 

* Pioneer Odyssey (NASA SP-349/396, revised edition, 1977) by Richard Fimmel, William Swindell, 

and Eric Burgess. Online version available. 

* Apollo Expeditions to the Moon. NASA SP-350, 1975. Out of print. Online version available. 

* Apollo Over the Moon: A View From Orbit (NASA SP-362, 1978) edited by Harold Masursky, 

G.W. Colton, and Farouk El-Baz. Online version available. 

* Introduction to the Aerodynamics of Flight (NASA SP-367, 1975) by Teodore A. Talay. 

Online version available. 

* Biomedical Results of Apollo (NASA SP-368, 1975) , edited by Richard S. Johnston, Lawrence F. Dietlein, 

M.D., and Charles A. Berry, M.D. Online version available. 

* Skylab: Our First Space Station (NASA SP-400, 1977), edited by Leland F. Belew. Online version available. 

* Skylab, Classroom in Space (NASA SP-401, 1977), edited by Lee Summerlin. Online version available. 

* A New Sun: Solar Results from Skylab (SP-402, 1979) by John A. Eddy and edited by Rein Ise. 

Online version available. 

* Skylab’s Astronomy and Space Sciences (NASA SP-404, 1979), edited by Charles A. Lundquist. 

Online version available. 

* Te Space Shuttle (SP-407, 1976) . Online version available. 

* Te Search For Extraterrestrial Intelligence (NASA SP-419, 1977) , edited by Philip Morrison, 

John Billingham, 

and John Wolfe. Online version available. 

* Atlas of Mercury (SP-423, 1978) by Merton E. Davies, Stephen E. Dwornik, et. al. Online version available. 

* Te Voyage of Mariner 10: Mission to Venus and Mercury (NASA SP-424, 1978)by James A. Dunne and 

Eric Burgess. Online version available. 

* Te Martian Landscape (NASA SP-425, 1978) 

* Te Space Shuttle at Work (NASA SP-432/EP-156 1979) by Howard Allaway. Online version available. 

* Project Orion: A Design Study of a System for Detecting Extrasolar Planets (NASA SP-436, 1980), edited by 

David C. Black. Online version available. 

Innovation in Flight 383 
NASA HISTORY SERIES 

* Wind Tunnels of NASA. NASA SP-440, 1981. Out of print. Online version available. 

* Viking Orbiter Views of Mars (NASA SP-441, 1980) . Online version available. 

* Te High Speed Frontier: Case Histories of Four NACA Programs, 1920-1950. (NASA SP-445, 1980.) . 

Online version available. 

* Te Star Splitters: Te High Energy Astronomy Observatories (SP-466, 1984) by Wallace H. Tucker. 

Online version available. 

* Planetary Geology in the 1980s (SP-467, 1985) by Joseph Veverka. 

* Quest for Performance: Te Evolution of Modern Aircraft. (NASA SP-468,1985.) Out of print. 

Online version available. 

* Te Long Duration Exposure Facility (LDEF): Mission 1 Experiments (SP-473, 1984) ed. by Lenwood G. Clark, 

William H. Kinar, et. al. . Online version available. 

* Voyager 1 and 2, Atlas of Saturnian Satellites (NASA SP-474, (NASA SP-474, 1984) edited by 

Raymond Batson. Online version available. 

* Far Travelers: Te Exploring Machines (NASA SP-480, 1985) by Oran W. Nicks. Online version available. 

* Living Aloft: Human Requirements for Extended Spacefight. (NASA SP-483, 1985. ) 

Out of print. Online version available. 

* Space Shuttle Avionics System (SP-504, 1989) by John F. Hanaway and Robert W. Moorehead. 

Online version available. 

* Life Into Space: Space Life Sciences Research, Volumes I and II, 1965-1998 (SP-534, 1995, 2000). 

Online version available. 

* Flight Research at Ames, 1940-1997 (SP-3300, 1998). Online version available. 

* Te Planetary Quarantine Program (SP-4902, 1974). Online version available. 

* Spaceborne Digital Computer Systems (NASA SP-8070, 1971). Online version available. 

* Magellan: Te Unveiling of Venus (JPL-400-345, 1989) . Online version available. 

* Guide to Magellan Image Interpretation (JPL-93-24) by John Ford, Jefrey Plaut, et. al. 

Online version available. 

* Te Apollo Program Summary Report (Document # JSC-09423, April 1975) . Online version available. 

* Saturn Illustrated Chronology (MHR-5, Marshall Space Flight Center, ffth edition, 1971) prepared by

 David S. Akens. Online version available. 

* Celebrating a Century of Flight (NASA SP-2002-09-511-HQ). Edited by Tony Springer. 

Online version available. 

* Present and Future State of the Art in Guidance Computer Memories (NASA TN D-4224, 1967) 

by Robert C. Ricci. Online version available. 

NASA Educational Publications 

Skylab: A Guidebook (NASA EP-107, 1973), by Leland F. Belew and Ernst Stuhlinger. Special thanks to 

Chris Gamble for formatting this book for the Web. 

Spacelab: An International Short-Stay Orbiting Laboratory (NASA EP-165) by Walter Froehlich. Te full text and 

rich images from this informative book about Europe’s frst major undertaking in human spacefight are now available on-line thanks to volunteer Chris Gamble’s expert help. 

A Meeting with the Universe: Science Discoveries from the Space Program (NASA EP-177,1981). Written by a group 

384 Innovation in Flight 
 

NASA HISTORY SERIES 

of NASA scientists for a popular audience, this attractive photo book is not a formal NASA history, but a “history 

of space exploration--by NASA, by universities, by other government agencies, and by industries--all of whom have 

played major roles.” Warm thanks to Hans-Peter Engel, who scanned and formatted this special book for the Web. 

NASA Publications (NPs) 

Science in Orbit: Te Shuttle & Spacelab Experience: 1981-1986 (NASA NP-119, Marshall Space Flight Center, 

1988). Provided by the European Space Agency, the Spacelab entails both an enclosed laboratory and an exposed 

platform for scientifc experiments in space. Tanks to volunteer Chris Gamble for scanning and formatting this 

informative guide to this unique facility. 

NASA Conference Proceedings 

Life in the Universe : Proceedings of a conference held at NASA Ames Research Center Mofet Field, California, 

June 19-20, 1979 (NASA CP-2156, 1981), edited by John Billingham. Special thanks to Chris Gamble for formatting this volume for the Web. 

Proceedings of the X-15 First Flight 30th Anniversary Celebration of June 8, 1989 Tese proceedings include comments by historians, pilots, and others with keen insights on the truly historic X-15 program that bridged aeronautics with astronautics during NASA’s frst decade. 

NASA Technical Memoranda 

* Destination Moon: A History of the Lunar Orbiter Program . Washington, D.C.: NASA TM-3487,1977. 

Written by Bruce Byers, this technical memorandum is a book-length scholarly work detailing the history of 

the robotic Lunar Orbiter Program, which provided very useful mission planning data for the Apollo 

program. Without the Lunar Orbiters’ mapping of the lunar surface, it would have been extremely difcult,

 if not impossible, for Apollo planners to decide where to land the Apollo spacecraft on the Moon. A special 

thanks to Chris Gamble for formatting this document’s complete text and illustrative diagrams for the Web. 

Out of print. 

Contractor Reports 

* Computers in Spacefight: Te NASA Experience. James E. Tomayko wrote this contractor report in 1988. A 

relatively unique document, this report covers computers in the Gemini, Apollo, Skylab, and Shuttle 

programs, as well as for robotic spacecraft and ground systems. Chris Gamble deserves kudos for his excellent 

work formatting the text of this prime reference document for the Web. Tis document should be available 

in hard copy, with photographs, in late February 1998 from NASA’s Center for Aerospace Information 

(CASI). Contact CASI at 800 Elkridge Landing Road, Linthicum Heights, MD 21090, 301-621-0100 or 

email at help@sti.nasa.gov 

Other Government Publications Related to Aerospace History 

History of Research in Space Biology and Biodynamics at the Air Force Missile Development Center, Holloman Air Force 

Base, New Mexico, 1946-1958. Tis early Air Force report contains information that NASA built upon in developing Project Mercury. It may be of special interest to some historians and bufs because of John Glenn’s fight on 

STS-95 and because of the fortieth anniversary of the Mercury Seven selection in 1999. A very special thanks to 

Innovation in Flight 385 
 

NASA HISTORY SERIES 

Chris Gamble for formatting the complete text of this report for the Web. 

Report of the Apollo 13 Review Board (a.k.a. the Cortright Commission): Tis is the report issued after the Apollo 

13 accident which prevented the mission from landing on the moon and nearly cost the lives of the astronauts involved. Special thanks to Colin Fries and Sivram Prasad of the History Division for scanning and formatting this 

report for the Web. 

Report of the Presidential Commission on the Space Shuttle Challenger Accident (commonly called the Rogers 

Commission Report), June 1986 and Implementations of the Recommendations, June 1987. 

Online version available. 

Transiting from Air to Space: Te North American X-15 Tis case study by Robert S. Houston, Richard P. Hallion, and Ronald G. Boston is a long chapter in Te Hypersonic Revolution: Case Studies in the History of Hypersonic 

Technology (AirForce History and Museums Program: 1998). A key contribution to the literature on the X-15, one 

of NASA’s most successful research aircraft programs, this case study was previously published as a stand-alone 

volume. Special thanks to Hans-Peter Engel, who formatted this work for the Web. 

Space Handbook: Astronautics and its Applications. Tis 1959 publication was a staf report of the Congressional 

Select Committe on Astronauticsand Space Exploration. An interesting historical document, this Handbook includes much information about astronomy and astronautics that we now know to be incorrect. Nevertheless, this 

document provides a snapshot of the beginning of the space era. Special thanks to John Henry, who scanned and 

formatted this document. 

Te First Century of Flight: NACA/NASA Contributions to Aeronautics. Tis is an informative and attractive 

Web exhibit set up in a timeline format. Special thanks to Tony Springer, who supplied the content; Ray Brown, 

who created the hard copy version; and Douglas Ortiz, who created the Web version. 

New Series in NASA History Published by the Johns Hopkins University Press: 

Tese books are available by calling 410-516-6956 or see http://www.press.jhu.edu/books/ 

* Cooper, Henry S. F., Jr. Before Lift-of: Te Making of a Space Shuttle Crew. Baltimore: Johns Hopkins 

University Press, 1987. 

* McCurdy, Howard E. Te Space Station Decision: Incremental Politics andTechnological Choice. Baltimore: 

Johns Hopkins University Press, 1990. 

* Hufbauer, Karl. Exploring the Sun: Solar Science Since Galileo. Baltimore: JohnsHopkins University Press, 

1991. 

* McCurdy, Howard E. Inside NASA: High Technology and Organizational Change in the U.S. Space Program. 

Baltimore: Johns Hopkins UniversityPress,1993. 

* Lambright, W. Henry. Powering Apollo: James E. Webb of NASA. Baltimore: Johns Hopkins University Press, 

1995. 

* Bromberg, Joan Lisa. NASA and the Space Industry. Baltimore: Johns Hopkins University Press, 1999. 

* Beattie, Donald A. Taking Science to the Moon: Lunar Experiments and the Apollo Program . Baltimore: 

Johns Hopkins University Press, 2001. 

386 Innovation in Flight 
 

 

 

NASA HISTORY SERIES 

* McCurdy, Howard E. Faster, Better, Cheaper: Low-Cost Innovation in the U.S. Space Program. Baltimore: 

Johns Hopkins University Press, 2001. 

* Johnson, Stephen B. Te Secret of Apollo: Systems Management in American and European Space Programs. 

Baltimore: Johns Hopkins University Press, 2002. 

* Lambright, W. Henry, editor. Space Policy in the 21st Century . Baltimore: Johns Hopkins University Press, 

2002. 

* Bilstein, Roger E. Testing Aircraft, Exploring Space: An Illustrated History of NACA and NASA. Baltimore: 

Johns Hopkins University Press, 2003. 

* Butrica, Anderw J. Single Stage to Orbit: Politics, Space Technology, and the Quest for Reusable Rocketry. 

Baltimore: Johns Hopkins University Press, 2005. 

* Conway, Erik M. High-Speed Dreams: NASA and the Technopolitics of Supersonic Transportation, 1945-1999. 

Baltimore: Johns Hopkins University Press, 2005. 

New Series in NASA History Published by Texas A&M University Press 

* Schorn, Ronald A. Planetary Astronomy: From Ancient Times to the Tird Millennium. College Station: 

Texas A&M University Press, 1998. To order, see http://www.tamu.edu/upress/BOOKS/1998/schorn.htm 

New Series in NASA History Published by Te University Press of Kentucky 

* Gorn, Michael H. Expanding the Envelope: Flight Research at NACA and NASA. Lexington: Te University 

Press of Kentucky, 2001. To order see http://www.kentuckypress.com/index.cfm. 

* Reed, R. Dale. Wingless Flight: Te Lifting Body Story . Lexington: Te University Press of Kentucky, 2002. To 

order see http://www.kentuckypress.com/index.cfm 

* Ed. by Launius, Roger D. and Dennis R. Jenkins. To Reach the High Frontier: 

A History of U.S. Launch Vehicles . Lexington: Te University Press of Kentucky, 2002. To order see 

http://www.kentuckypress.com/index.cfm. 

New Series in NASA History Published by the University Press of Florida 

* Ed. by Swanson, Glen W. “Before Tis Decade is Out...”: Personal Relections on the Apollo Program. 

Gainesville: Te University Press of Florida, 2002. To order see http://www.upf.com/index.shtml 

* Benson, Charles D. and William B. Faherty. Moon Launch!: A History of the Saturn-Apollo Launch Operations. 

Gainesville: Te University Press of Florida, 2001. To order see http://www.upf.com/index.shtml 

* Benson, Charles D. and William B. Faherty. Gateway to the Moon: Building the Kennedy Space Center Launch 

Complex. Gainesville: Te University Press of Florida, 2001. To order see http://www.upf.com/index.shtml. 

* Bilstein, Roger E. Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles. 

NASA SP-4206, 1980, 1996, and 2003. Gainesville: Te University Press of Florida, 2003. 

To order see http://www.upf.com/index.shtml. 

* Siddiqi, Asif A. Te Soviet Space Race with Apollo. Gainesville: Te University Press of Florida, 2003. 

To order see http://www.upf.com/index.shtml. 

* Siddiqi, Asif A. Sputnik and the Soviet Space Challenge . Gainesville: Te University Press of Florida, 2003. 

To order, see http://www.upf.com/index.shtml. 

New Series in NASA History Published by Harwood Academic Press 

* Ed. by Roger D. Lanius, John M. Logsdon and Robert W. Smith. Reconsidering Sputnik: 

Innovation in Flight 387 
 

NASA HISTORY SERIES 

Forty Years Since the Soviet Satellite. London: Harwood Academic Press, 2000. 

To order, see http://www.taylorandfrancisgroup.com/ 

New Series in NASA History Published by the University of Illinois Press 

* Ed. by Roger D. Launius and Howard McCurdy. Spacefight and the Myth of Presidential Leadership. Urbana, 

IL: University of Illinois Press, 1997. To order, see http://www.press.uillinois.edu/f97/launius.html 

New Series in NASA History Published by Greenwood Press 

* Launius, Roger D. Frontiers of Space Exploration. Westport, CT: Greenwood Press, 1998. To order, 

see http://www.greenwood.com/default.asp 

New Series in NASA History Published by the Smithsonian Institution Press 

* Heppenheimer, T.A. Development of the Shuttle, 1972-1981. Washington, DC: Smithsonian Institution Press, 

2002. To order, see http://www.si.edu/. 

* Dethlof, Henry C. and Ronald A. Schorn. Voyager’s Grand Tour: To the Outer Planets and Beyond. 

Washington, DC: Smithsonian Institution Press, 2003. To order, see http://www.si.edu/. 

* Hallion, Richard P. and Michael H. Gorn. On the Frontier: Experimental Flight at NASA Dryden. 

Washington, DC: Smithsonian Institution Press, 2003. To order, see http://www.si.edu/. 

New Series in NASA History Published by CG Publishing, Inc. 

* Te Mission Transcript Collection: U.S. Human Spacefight Missions From Mercury Redstone 3 to Apollo 17 

(NASA SP-2000-4602). To order send an International Money Order for $8.00 to CG Publishing Inc, Box 

62034, Burlington, Ontario, L7R 4K2, Canada or call 905-637-5737. 

Miscellaneous Publications of NASA History 

* Dawson, Virginia. Ideas Into Hardware: A History of the Rocket Engine Test Facility at the NASA Glenn Research 

Center Cleveland, 2004. Online version available. 

388 Innovation in Flight 
ABOUT THE AUTHOR 

Joseph R. Chambers is an aviation consultant who lives in Yorktown, Virginia. He retired from 

the NASA Langley Research Center in 1998 after a 36-year career as a researcher and manager of 

military and civil aeronautics research activities. He began his career as a specialist in fight dynamics 

as a member of the staf of the Langley 30- by 60-Foot (Full-Scale) Tunnel, where he conducted 

research on a variety of aerospace vehicles including V/STOL confgurations, re-entry vehicles, and 

fghter aircraft confgurations. He later became a manager of research projects in the Full-Scale 

Tunnel, the 20-Foot Vertical Spin Tunnel, fight research at Langley, and piloted simulators. When 

he retired from NASA, he was manager of a group responsible for conducting systems analysis of 

the potential payofs of advanced aircraft concepts and NASA research investments. 

Mr. Chambers is the author of over 60 technical reports and publications, including NASA Special 

Publications: SP-514 Patterns in the Sky on the subject of airfow condensation patterns over 

aircraft; SP-2000-4519 Partners in Freedom on contributions of the Langley Research Center to 

U.S. military aircraft of the 1990s; and SP-2003-4529 Concept to Reality on contributions of the 

Langley Research Center to U.S. civil aircraft of the 1990s. He has made presentations on research 

and development programs to audiences as diverse as the Von Karman Institute in Belgium and the 

annual Experimental Aircraft Association (EAA) AirVenture Convention at Oshkosh, WI. He has 

served as a representative of the United States on international committees in aeronautics and has 

given lectures in Japan, China, Australia, the United Kingdom, Canada, Italy, France, Germany, 

and Sweden. 

Mr. Chambers received several of NASA’s highest awards, including the Exceptional Service Medal 

and the Outstanding Leadership Medal. He also received the Arthur Flemming Award in 1975 as 

one of the 10 Most Outstanding Civil Servants for his management of NASA stall/spin research 

for military and civil aircraft. He has a bachelor of science degree from the Georgia Institute 

of Technology and a master of science degree from the Virginia Polytechnic Institute and State 

University (Virginia Tech). 

Innovation in Flight 389 
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Innovation in Flight: Research of the Langley Research Center on 

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14. ABSTRACT 

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. 

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Aeronautics; Technical innovations; Research aircraft 

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