Category NASA’S CONTRIBUTIONS TO AERONAUTICS

In 1997, in response to a White House Commission on Aviation Safety and Security, NASA created the Aviation Safety Program. SVS fit per­fectly within the goals of this program, and the NASA established a SVS project under AvSp, commencing on October 1, 1999. Daniel G. Baize, who had led the XVS element of the Flight Deck ITD Team during the HSR program, continued in this capacity as Project Manager for SVS under AvSP. He wasn’t the only holdover from HSR: most of the tal­ented researchers from HSR XVS moved directly to similar roles under AvSP and were joined by their Langley LVLASO colleagues. Funding for FL.5 transitioned from HSR to AvSP, effectively making FL.5 the first of many successful AvSP SVS flight tests.

Langley’s SVS research project consisted of eight key technical areas: database rendering, led by Jarvis "Trey” Arthur, III, and Steve Williams; pathway concepts, led by Russell Parrish, Lawrence "Lance” Prinzel, III, Lynda Kramer, and Trey Arthur; runway incursion prevention systems, led by Denise R. Jones and Steven D. Young; controlled flight into terrain (CFIT) avoidance using SVS, led by Trey Arthur; loss of control avoid­ance using SVS, led by Douglas T. Wong and Mohammad A. Takallu; data­base integrity, led by Steven D. Young; SVS sensors development, led by Steven Harrah; and SVS database development, led by Robert A. Kudlinski and Delwin R. Croom, Jr. These individuals were supported by numerous NASA and contractor researchers and technicians, and by a number of ded­icated industry and academia partners.[1173] By any measure, SVS development was moving forward along a broad front at the turn of the 21st century.

The first flight test undertaken under the SVS project occurred at the Dallas-Fort Worth International Airport (DFW) in September and October 2000. It constituted the culmination of Langley’s LVLASO project,
demonstrating the results of 7 years of research into surface display con­cepts for reduced-visibility ground operations. Because funding for the LVLASO experiment had transitioned to the AvSP, SVS Project Manager Dan Baize decided to combine the LVLASO elements of the test with continued SVS development. SVS was by now bridging the ground oper – ation/flight operation regimes into one integrated system, although at DFW, each was tested separately.

Reduced ground visibility has always constituted a risk in aircraft operations. On March 27, 1977, an experienced KLM 747 flight crew holding for takeoff clearance at Los Rodeos Airport, Tenerife, fell victim to a fatal combination of misunderstood communications and reduced ground visibility. Misunderstanding tower communications, the crew­members began their takeoff roll and collided with a Pan American 747 still taxiing on landing rollout on the active runway. This accident claimed 578 lives, including all aboard the KLM aircraft and still con­stitutes the costliest accident in aviation history.[1174] Despite the Tenerife disaster, runway incursions continued to rise, and the potential for fur­ther tragedies large and small was great. Incursions rose from 186 in 1993 to 431 in 2000, a 132-percent increase. In the first 5 months of 2000, the FAA and National Transportation Safety Board (NTSB) logged 158 incur­sions, an average of more than 1 runway incursion incident each day.[1175]

Recognizing the emphasis on runway incursion accident preven­tion, researchers evaluated a Runway Incursion Prevention System (RIPS), the key element in the DFW test. RIPS brought together advanced technologies, including surface communications, navigation, and sur­veillance systems for both air traffic controllers and pilots. RIPS uti­lized both head-down moving map displays for pilot SA and data link communication and an advanced HUD for real-time guidance. While

RIPS research was occurring on the ground, SVS concepts were being evaluated in flight for the first time in a busy terminal environment. This evaluation included a Langley-developed opaque HUD concept. Due to the high capacity of flight operations during normal hours at DFW, all research flights occurred at night. HSR veterans Lou Glaab, Lynda Kramer, Jarvis "Trey” Arthur, Steve Harrah, and Russ Parrish managed the SVS experiments, while LVLASO researchers Denise Jones and Richard Hueschen led the RIPS effort.[1176]

The successor to Langley’s remarkable ATOPS B-737 was a modi­fied Boeing 757, the Aries research airplane. Aries—a name suggested by Langley operations engineer Lucille Crittenden in an employee sug­gestion campaign—stood for Airborne Research Integrated Experiments System. For all its capabilities, Aries had a somewhat checkered his­tory. Like many new research programs, it provided systemic challenges to researchers that they had not encountered with the B-737. Indeed, Langley’s research pilot staff had favored a smaller aircraft than the 757, one that would be less costly and demanding to support. Subsequently, the 757 did prove complex and expensive to maintain, impacting the range of modifications NASA could make to it. For example, Aries lacked the separate mid-fuselage Research Flight Deck that had proven so adapt­able and useful in the ATOPS 737. Instead, its left seat of the cockpit (traditionally the "captain’s seat” in a multipilot aircraft) of was modi­fied to become a Forward Flight Deck research station. This meant that, unlike the 737, which had two safety pilots in the front cockpit while a test crew was using the Research Flight Deck, the 757 was essentially a "one safety pilot at the controls” aircraft, with the right-seat pilot per­forming the safety role and another NASA pilot riding in the center jump seat aft and between both the research and safety pilot. This increased the workload of both the research and safety pilots.[1177]

As configured for the DFW tests, Aries had an evaluation pilot in the left seat, a NASA safety pilot/pilot-in-command in the right seat, a secondary NASA safety pilot in the center jump seat, and the principal investigator in the second jump seat. The safety pilot monitored two com­munication frequencies and an intercom channel connected to the numer­ous engineers and technicians in the cabin. Because the standard B-757 flight deck instrumentation did not support the SVS displays, the SVS
researchers developed a portable SVS primary flight display that would be temporarily mounted over the pilot’s instrument panel. An advanced HUD was installed in the left-seat position as well, for use during final approach, rollout, turnoff, and taxi. The HUD displayed symbology relat­ing runway and taxiway edge and centerline detail, deceleration guid­ance, and guidance to gates and hold-short points on the active runway. As well, the Aries aircraft had multifunction display capability, includ­ing an electronic moving map (EMM) that could be "zoomed” to various scales and that could display the DFW layout, locations of other traffic, and ATC instructions (the latter displayed both in text and visual for­mats). Additionally, a test van outfitted with an Automatic Dependent Surveillance-Broadcast (ADS-B) Mode S radar transponder, an air traffic control Radio Beacon System (ATCRBS) transponder, a Universal Access Transceiver (UAT) data link, and a differential GPS was deployed to test sites and used to simulate an aircraft on the ground that could interact during various scenarios with the Aries test aircraft.[1178]

The DFW tests occurred in October 2000, with the Aries 757 interact­ing with the surrogate "airliner” van, and with the airport equipped on its east side with a prototype FAA ground surveillance system developed under the Agency’s runway incursion reduction program. Researchers were encouraged by the test results, and industry and Government eval­uation pilots agreed that SVS technologies showed remarkable potential, reflecting the thorough planning of the test team and the skill of the flight crew. The results were summarized by Denise R. Jones, Cuong C. Quach, and Steven D. Young as follows:

The measured performance of the traffic reporting technologies tested at DFW do meet many of the current requirements for surveillance on the airport surface. However, this is apparently not sufficient for a robust runway incursion alerting function with RIPS. This assessment is based on the observed rats of false alerts and missed detections. All false alerts and missed detections at DFW were traced to traffic data that was inac­curate, inconsistent, and/or not received in a timely manner….

All of the subject pilots were complimentary of the RIPS tested at DFW. The pilots stated that the system has the potential
to reduce or eliminate runway incursions, although human factors issues must still be resolved. Several suggestions were made regarding the alerting symbology which will be incorpo­rated into future simulation studies. The audible alert was the first display to bring the pilots’ attention to the incursion. The EMM would generally be viewed by the non-flying pilot at the time of an incursion since the flying pilot would remain heads up. The pilots stated that two-stage alerting was not necessary and they would take action on the first alert regardless. This may be related to the fact that this was a single pilot opera­tion and the subject pilot did not have the benefit of co-pilot support. In general, after an incursion alert was received, the subject pilots stated they would not want maneuver guidance during final approach or takeoff roll but would like guidance on whether to stop or continue when taxiing across a runway.

All of the pilots stated that, in general, the onboard alerts were generated in a timely manner, allowing sufficient time to react to the potential conflict. They all felt safer with RIPS onboard.[1179]

Almost exactly a year later, the SVS project deployed to a remote location for a major integrated flight test and demonstration of the Aries B-757, the third year in a row that the team had deployed for an offsite test. This time, the location was the terrain-challenged Eagle County Regional Airport near Vail, CO. Eagle-Vail is situated in a valley with mountains on three sides of the runway. It is also at an elevation of 6,540 feet, giving it a high-density altitude on hot summer days, which is not conducive to air­plane performance. Langley’s Aries B-757 was configured with two HUDs and four head-down concepts developed by NASA and its industry part­ner, Rockwell Collins. Enhanced Vision Systems were evaluated as well for database integrity monitoring and imaging the runway environment. Three differently sized head-down PFDs were examined: a "Size A” system, measuring 5.25 inches wide by 5 inches tall, such as flown on a conven­tional B-757-200 series aircraft; a "Size D” 6.4-inch-wide by 6.4-inch-tall display, such as employed on the B-777 family; and an experimental "Size X,” measuring 9 inches wide by 8 inches tall, such as might be flown on a future advanced aircraft.

Additionally, multiple radar altimeters and differential GPS receiv­ers gathered absolute altitude data to be used in developing database integrity monitoring algorithms.[1180]

Randy Bailey was NASAs Principal Investigator, joined by Russ Parrish, Dan Williams, Lynda Kramer, Trey Arthur, Steve Harrah, Steve Young, Rob Kudlinski, Del Croom, and others. Seven pilots from NASA, the FAA, the airline community, and Boeing evaluated the SVS concepts, with par­ticular attention to the terrain-challenged approaches. While fixed-base simulation had indicated that SVS could markedly increase flight safety in terrain-challenged environments, flight-test data had not yet been acquired under such conditions, aside from the limited experience of the Air Force-Calspan TIFS NC-131H trials at Asheville, NC, in September 1999. Of note was the ability of the B-757 to fly circling approaches under simulated instrument meteorological conditions (IMC) using the highly developed SVS displays. Until this test, commercial jet airplanes had not made circling approaches to Eagle-Vail under IMC.[1181] SVS were proving their merit in the most challenging of arenas, something evident in the comments of one evaluation pilot, who noted afterward:

I often commented to people over the years that I never ever flew a circling approach in the -141 [Lockheed C-141 Starlifter] that I was ever comfortable with, particularly at night. It always demanded a lot of attention. This was the first time I ever had an occasion of circling an approach with the kind of information I would love to have in a circling approach. Keeping me safe, I could see the terrain, taking me where I want to go, getting me all types of information in terms to where I am relative to the end of the runway. I mean it’s the best of all possible worlds in terms of safety.[1182]

Unfortunately, this proved to be the last major flight-test program flown on NASA’s B-757 aircraft. An incident during the Eagle-Vail test­ing had profound effects on its future, illustrating the weakness of not
having an independent Research Flight Deck separated from the Forward Flight Deck, which could be occupied by a team of "full-time” safety pilots. After the B-757 missed its approach at Eagle-Vail following a test run, its auto throttles disconnected, without being noticed by the busy flight crew. The aircraft became dangerously slow in the worst possible circumstances: low to the ground and at a high-density altitude. In the subsequent confusion during recovery, the evaluation pilot, unaware that Aries lacked the kind of Full Authority Digital Electronic Control (FADEC) for its turbofan engines on newer B-757s, inadvertently over­boosted both powerplants, resulting in an in-flight abort. The incident reflected as well the decision to procure the B-757 without FADEC engine controls and insufficient training of evaluation pilots before their sor­ties into the nuances of the non-FADEC airplane. The busy flight deck caused by the FFD design likely also played a role in this incident, as it likely did in previous, less serious events. Safety concerns raised by pilots over this and other issues resulted in the grounding of the B-757 in June 2003. Subsequent examination revealed that it had overloaded floor beams, necessitating costly repairs. Though these repairs were com­pleted during a 12-month period in 2004-2005, NASA retired it from service in 2005, bringing its far-too-brief operational career to an end.[1183]

In 2001, NASA Langley’s SVS project was organized into two areas: commercial and business aircraft and general-aviation. Randy Bailey had come to NASA from Calspan and became a Principal Investigator for CBA tests, and Lou Glaab assumed the same role for GA. Monica Hughes, Doug Wong, Mohammad Takallu, Anthony P. Bartolome, Francis G. McGee, Michael Uenking, and others joined Glaab in the GA program, while most of the other aforementioned researchers continued with CBA. Glaab and Hughes led an effort to convert Langley’s Cessna 206-H Stationaire into a GA SVS research platform. A PFD and NAV display were installed on the right side of the instrument panel, and an instrumentation pal­let in the cabin contained processors to drive the displays and a sophis­ticated data acquisition system.[1184]

SVS was particularly important for general aviation, in which two kinds of accidents predominated: controlled flight into terrain and loss

of horizon reference (followed by loss of aircraft control and ground impact).[1185] To develop a candidate set of GA display concepts, Glaab con­ceived a General-Aviation Work Station (GAWS) fixed-base simulator, similar to the successful Virtual Imaging Simulator for Transport Aircraft Systems simulator. Doug Wong and other team members helped bring the idea to reality, and GAWS allowed the GA researchers and evaluation pilots to design and validate several promising GA SVS display sets. The GA implementation differed from the previous and ongoing CBA work, in that SVS for the GA community would have to be far lower in cost, computational capability, and weight. A HUD was deemed too expensive, so the PFD would assume added importance. An integrated simulation and flight-test experiment using GAWS and the Cessna 206 known as Terrain Portrayal for Head-Down Displays (TP-HDD) was commenced in summer 2002. The flight test spanned August through October at Newport News and Roanoke, two of Virginia’s regional airports.[1186]

Both EBG and photorealistic displays were evaluated, and results indicated that equivalent performance across the pilot spectrum could

be produced with the less computationally demanding EBG concepts. This was a significant finding, especially for the computationally and economically challenged low-end GA fleet.[1187]

The SVS CBA team had planned a comprehensive flight test using the Aries B-757 for summer 2003 at the terrain-challenged Reno-Tahoe International Airport. This flight test was to have included flight and surface runway incursion scenarios and operations using integrated SVS displays, including an SVS HUD and PFD, RIPS symbology, hazard sensors, and database integrity monitoring in a comparative test with conventional instruments. The grounding of Aries ended any hope of completing the Reno-Tahoe test in 2003. Set back yet undeterred, the SVS CBA researchers looked for alternate solutions. Steve Young and his Database Integrity Monitoring Experiment (DIME) team quickly found room on NASA Ames’s DC-8 Airborne Science Platform in July and August for database integrity monitoring and Light Detection and Ranging (LIDAR) elevation data collection.[1188] At the same time, manag­ers looked for alternate airframes and negotiated an agreement with Gulfstream Aerospace to use a G-V business jet with Gulfstream’s Enhanced Vision System. From July to September 2004 at Wallops and Reno-Tahoe International Airport, the G-V with SVS CBA researchers and partners from Rockwell Collins, Gulfstream, Northrop Grumman, Rannoch Corporation, Jeppesen, and Ohio University evaluated advanced runway incursion technologies from NASA-Lockheed Martin and Rannoch Corporation and SVS display concepts from Langley and Rockwell Collins. Randy Bailey again was project lead. Lynda Kramer and Trey Arthur were Principal Investigators for the SVS display devel­opment, and Denise Jones led the runway incursion effort. Steve Young and Del Croom managed the DIME investigations, and Steve Harrah continued to lead sensor development.[1189]

The Reno flight test was a success. SVS technologies had been shown to provide a significant improvement to safe operations in reduced vis­ibility for both flight and ground operations. SVS CBA researchers and managers, moreover, had shown a tenacity of purpose in completing project objectives despite daunting challenges. The last SVS flight test was approaching, and significant results awaited.

In August and September 2005, Lou Glaab and Monica Hughes led their team of SVS GA researchers on a successful campaign to argue for the concept of equivalent safety for VMC operations and SVS in IMC. Russ Parrish, at the time retired from NASA, returned to lend his considerable talents to this final SVS experiment. Using the Langley Cessna 206 from the TP-HDD experiment of 2002, Glaab and Hughes employed 19 evaluation pilots from across the flight-experience spec­trum to evaluate three advanced SVS PFD and NAV display concepts and a baseline standard GA concept to determine if measured flight techni­cal error (FTE) from the low-experience pilots could match that of the highly experienced pilots. Additionally, the question of whether SVS dis­plays could provide VMC-like performance in IMC was explored. With pathway-based guidance on SVS terrain displays, it was found that the FTE of low-time pilots could match that of highly experienced pilots. Furthermore, for the more experienced pilots, it was observed that with advanced SVS displays, difficult IMC tasks could be done to VMC perfor­mance and workload standards. The experiment was carefully designed to allow the multivariate discriminant analysis method to precisely quan­tify the results. Truly, SVS potential for providing equivalent safety for IMC flight to that of VMC flight had been established. The lofty goals of the SVS project established 6 years previously had been achieved.[1190]

After the Reno SVS CBA flight test and spanning the termination of the SVS project in 2005, Randy Bailey, Lynda Kramer, Lance Prinzel and others investigated the integration of SVS and EVS capabilities in a comprehensive simulation test using Langley’s fixed-base Integrated Intelligent Flight Deck Technologies simulator, a modified Boeing 757 flight deck. Twenty-four airline pilots evaluated a HUD and auxiliary head-down display with integrated SVS and EVS presentations, where forward-looking infrared video was used as the enhanced vision signal.

The fusion here involved blending a synthetic database with the FLIR signal at eight discrete steps selectable by the pilot. Both FLIR and SV signals were imagery generated by the simulation computers. The results showed an increase in SA for all of the subject pilots. Surprisingly, obstacle runway incursion detection did not show significant improve­ment in either the SV, EV, or fused displays.[1191]

The SVS project formally came to an end September 30, 2005. Despite many challenges, the dedicated researchers, research pilots, and technicians had produced an enviable body of work. Numerous techni­cal papers would soon document the results, techniques employed, and lessons learned. From SPIFR’s humble beginnings, NASA Langley had designed an SVS display and sensor system that could reliably trans­form night, instrument conditions to essentially day VMC for commer­
cial airliners to single-engine, piston-powered GA aircraft. Truly, this was what NASA aeronautics was all about. And now, as the former SVS team transitioned to IIFDT, the researchers at JSC were once again about to take flight.

To support NASA’s ongoing goal of improving aviation safety, the Education and Training Element of the Aircraft Icing Project contin­ues to develop education and training aids for pilots and operators on the hazards of atmospheric icing. A complete list of current train­ing aids is maintained on the GRC Web site. Education materials are tailored to several specific audiences, including pilots, operators, and engineers. Due to the popularity of the education products, NASA can no longer afford to print copies and send them out. Instead, interested parties can download material from the Web site[1269] or check out the lat­est catalog from Sporty’s Pilot Shop, an internationally known source of professional materials and equipment for aviators.[1270]

Icing Branch Facilities

NASA’s groundbreaking work to understand the aircraft icing phenom­enon would have been impossible if not for a pair of assets available at GRC. The more historic of the two is the Icing Research Tunnel (IRT),

which began service in 1944 and, despite the availability of other wind tun­nels with similar capabilities, remains one of a kind. The other asset is the DHC-6 Twin Otter aircraft, which calls the main hangar at GRC its home.

For ground-based research it’s the IRT, the world’s largest refriger­ated wind tunnel. It has been used to contribute to flight safety under icing conditions since 1944. The IRT has played a substantial role in developing, testing, and certifying methods to prevent ice buildup on gas-turbine-powered aircraft. Work continues today in the investigation of low-power electromechanical deicing and anti-icing fluids for use on the ground, deicing and anti-icing research on Short Take Off and Vertical Landing (STOVL) rotor systems and certification of ice protec­tion systems for military and commercial aircraft. The IRT is a closed – loop, refrigerated wind tunnel with a 6- by 9-foot test section. It can generate airspeeds from 25 to more than 400 miles per hour. Models placed in the tunnel can be subjected to droplet sprays of varying sizes to produce the natural icing conditions.[1271]

For its aerial research, the Icing Branch utilizes the capabilities of NASA 607, a DHC-6 Twin Otter aircraft. The aircraft has undergone many modifications to provide both the branch and NASA a "flying laboratory” for issues relating to the study of aircraft icing. Some of the capabilities of this research aircraft have led to development of icing protection sys­tems, full-scale iced aircraft aerodynamic studies, software code valida­tion for ground-based research, development of remote weather sensing technologies, natural icing physics studies, and more.[1272]

The U. S. Navy funded the F/A-18E/F Super Hornet program in 1992 to design its next-generation fighter as a replacement for the canceled A-12 aircraft and the earlier legacy F/A-18 versions. Although some­what similar in configuration to existing F/A-18C aircraft, the new design was a larger aircraft with critical differences in wing design and other features that impact high-angle-of-attack behavior. Two of the first configuration design issues centered on the shape of the wing leading-edge extension and the ability to obtain crisp nose-down control for recovery at extreme angles of attack. Representatives of Langley’s high-angle-of-attack specialty areas were participants in a 15-member NASA-industry-DOD team who conducted wind tunnel studies and anal­yses that provided the basis for the final design of the F/A-18E/F LEX.[1324]

Aerodynamic stability and control characteristics for the Super Hornet for high-angle-of-attack conditions were conducted in the Full – Scale Tunnel to develop a database for piloted simulator evaluations using the Langley and Boeing simulators. Once again, the Spin Tunnel was used for identifying spin modes, spin recovery characteristics, an acceptable emergency spin recovery parachute, and measurement of rotational aerodynamic characteristics using the rotary-balance tech­nique. Langley used an extremely large (over 1,000 pounds) drop model for departure susceptibility and poststall testing at the NASA Wallops Flight Facility to provide risk reduction for the subsequent full-scale flight-test program.[1325]

One of NASA’s more critical contributions to the Super Hornet pro­gram began in March 1996, when a preproduction F/A-18E experienced an unacceptable uncommanded abrupt roll-off that randomly occurred at high angles of attack (below maximum lift) at transonic speeds and involved rapid bank angle changes of up to 60 degrees in the heart of the maneuvering envelope. Engineering analyses indicated that the wing drop was caused by a sudden asymmetric loss of lift on the wing, but the fundamental cause of the problem was not well understood. Following the formation of a DOD Blue Ribbon Panel, a research pro­gram was recommended to be undertaken to develop design methods to avoid such problems on future fighter aircraft. This recommenda­
tion was accepted, and a joint NASA and Navy Abrupt Wing Stall (AWS) program was initiated to conduct the research.[1326]

Meanwhile, extensive efforts by industry and the Navy were under­way to resolve the wing-drop problem through wind tunnel tests and "cut and try” airframe modifications during flight tests. Over 25 potential wing modifications were assessed, and computational fluid dynamics studies were undertaken without a feasible fix identified. Subsequently, the automatically programmed wing leading-edge flaps were examined as a solution. Typical of current advanced fighters, the F/A-18E/F uses flaps with deflection programs scheduled as functions of angle of attack and Mach number. A revised deflection schedule was adopted in 1997 as a major improvement, but the aircraft still exhibited less serious wing drops at many test conditions. As the Navy test and evaluation staff con­tinued to explore further solutions to wing drop, exploratory flight tests with the outer-wing fold fairing removed indicated that the wing drop had been eliminated. However, unacceptable performance and buffet characteristics resulted from removing the fairing.

Langley personnel suggested that passive porosity be examined as a more acceptable treatment of the wing fold area based on NASA’s exten­sive fundamental research. Subsequently evaluated by the Navy flight – test team, the porous fold doors became a feature of the production F/A-18E/F and permitted continued production of the aircraft.

With the F/A-18E/F wing-drop problem resolved, NASA and the Naval Air Systems Command began their efforts in the AWS research program that used a coordinated approach involving static and dynamic tests at Langley in several wind tunnels, piloted simulator studies, and compu­tational fluid dynamics studies conducted by the Navy and NASA. The scope of research focused on the causes and resolution of the unexpected wing drop that had been experienced for the preproduction F/A-18E/F and the wealth of aerodynamic wind tunnel and flight data that had been collected, but the program was intentionally designed to include assessments of other aircraft for validation of conclusions. The stud­ies included the F/A-18C and the F-16 (both of which do not exhibit wing drop) and the AV-8B and the preproduction version of the F/A-18E (which do exhibit wing drop at the extremes of the flight envelope).

After 3 years of intense research on the complex topic of transonic shock-induced asymmetric stall at high angles of attack, the AWS program produced an unprecedented amount of design information, engineering tools, and recommendations regarding developmental approaches to avoid wing drop for future fighters. Particularly signifi­cant output from the program included the development and validation of a single-degree-of-freedom free-to-roll wind tunnel testing technique for detection of wing-drop tendencies, an assessment of advanced CFD codes for prediction of steady and unsteady shock-induced separation at high angles of attack for transonic flight, and a definition of simulator model requirements for assessment and prediction of wing drop. NASA and Lockheed Martin have already applied the free-to-roll concept in the development of the wing geometry for the F-35 fighter.[1327]

Robert A. Rivers

The aeronautics community has always had a strong international flavor. This case study traces how NASA researches in the late 1990s used a Russian supersonic airliner, the Tupolev Tu-144LL — built as a visible symbol of technological prowess at the height of the Cold War—to derive supersonic cruise and aerodynamic data. Despite numerous technical, organizational, and political challenges, the joint research team obtained valuable information and engendered much goodwill.

N A COOL, CLEAR, AND GUSTY SEPTEMBER MORNING in 1998, two NASA research pilots flew a one-of-a-kind, highly modi­fied Russian Tupolev Tu-144LL Mach 2 Supersonic Transport (SST) side by side with a Tupolev test pilot, navigator, and flight engi­neer from a formerly secret Soviet-era test facility, the Zhukovsky Air Development Center 45 miles southeast of Moscow, on the first of 3 flights to be flown by Americans.[1458] These flights in Phase II of the joint United States-Russian Tu-144 flight experiments sponsored by NASA’s High-Speed Research (HSR) program were the culmination of 5 years of preparation and cooperation by engineers, technicians, and pilots in the largest joint aeronautics program ever accomplished by the two countries. The two American pilots became the first and only non­Russian pilots to fly the former symbol of Soviet aeronautics prowess, the Soviet counterpart of the Anglo-French Concorde SST.

They completed a comprehensive handling qualities evaluation of the Tu-144 while 6 other experiments gathered data from hundreds of onboard sensors that had been painstakingly mounted to the airframe
in the preceding 3 years by NASA, Tupolev, and Boeing engineers and technicians. Only four more flights in the program awaited the Tu-144LL, the last of its kind, before it was retired. With the removal from service of the Concorde several years later, the world lost its only supersonic passenger aircraft and witnessed the end of an amazing era.

This is the story of a remarkable flight experiment involving the United States and Russia, NASA and Tupolev, and the men and women who worked together to accomplish a series of unique flight tests from late 1996 to early 1999 while overcoming numerous technical, program­matic, and political obstacles. What they accomplished in the late 1990s cannot be accomplished today. There are no more Supersonic Transports to be used as test platforms, no more national programs to explore com­mercial supersonic flight. NASA and Tupolev established a benchmark for international cooperation and trust while producing data of incal­culable value with a class of vehicles that no longer exists in a regime that cannot be reached by today’s transport airplanes.[1459]

FAA Federal Air Regulation (FAR) 23.867 governs protection of aircraft against lightning and static electricity, reflecting the influence of decades of NASA lightning research, particularly the NF-106B program. FAR 23.867 directs that an airplane "must be protected against catastrophic effects from lightning,” by bonding metal components to the airframe or, in the case of both metal and nonmetal components, designing them so that if they are struck, the effects on the aircraft will not be catastrophic. Additionally, for nonmetallic components, FAR 23.867 directs that air­craft must have "acceptable means of diverting the resulting electrical current so as not to endanger the airplane.”[166]

Among the more effective means of limiting lightning damage to aircraft is using a material that resists or minimizes the powerful pulse of an electromagnetic strike. Late in the 20th century, the aerospace industry realized the excellent potential of composite materials for that purpose. Aside from older bonded-wood-and-resin aircraft of the inter­war era, the modern all-composite aircraft may be said to date from the 1960s, with the private-venture Windecker Eagle, anticipating later air­craft as diverse as the Cirrus SR-20 lightplane, the Glasair III LP (the first composite homebuilt aircraft to meet the requirements of FAR 23), and the Boeing 787. The 787 is composed of 50-percent carbon lami­nate, including the fuselage and wings; a carbon sandwich material in the engine nacelles, control surfaces, and wingtips; and other compos­ites in the wings and vertical fin. Much smaller portions are made of aluminum and titanium. In contrast, indicative of the rising prevalence of composites, the 777 involved just 12-percent composites.

An even newer composite testbed design is the Advanced Composite Cargo Aircraft (ACCA). The modified twin-engine Dornier 328Jet’s rear fuse­lage and vertical stabilizer are composed of advanced composite materials produced by out-of-autoclave curing. First flown in June 2009, the ACCA is the product of a 10-year project by the Air Force Research Laboratory.[167]

NASA research on lightning protection for conventional aircraft structures translated into use for composite airframes as well. Because experience proved that lightning could strike almost any spot on an airplane’s surface—not merely (as previously believed) extremities such as wings and propeller tips—researchers found a lesson for designers using new materials. They concluded, "That finding is of great impor­tance to designers employing composite materials, which are less con­ductive, hence more vulnerable to lightning damage than the aluminum allows they replace.”[168] The advantages of fiberglass and other compos­ites have been readily recognized: besides resistance to lightning strikes, composites offer exceptional strength for light weight and are resistant to corrosion. Therefore, it was inevitable that aircraft designers would increasingly rely upon the new materials.[169]

But the composite revolution was not just the province of established manufacturers. As composites grew in popularity, they increasingly were employed by manufacturers of kit planes. The homebuilt aircraft market, a feature of American aeronautics since the time of the Wrights, expanded greatly over the 1980s and afterward. NASA’s heavy investment in light­ning research carried over to the kit-plane market, and Langley released a Small Business Innovation Research (SBIR) contract to Stoddard- Hamilton Aircraft, Inc., and Lightning Technologies, Inc., for develop­ment of a low-cost lightning protection system for kit-built composite aircraft. As a result, Stoddard-Hamilton’s composite-structure Glasair III LP became the first homebuilt aircraft to meet the standards of FAR 23.[170]

One of the benefits of composite/fiberglass airframe materials is inherent resistance to structural damage. Typically, composites are produced by laying spaced bands of high-strength fibers in an angu­lar pattern of perhaps 45 degrees from one another. Selectively wind­ing the material in alternating directions produces a "basket weave” effect that enhances strength. The fibers often are set in a thermo­plastic resin four or more layers thick, which, when cured, produces extremely high strength and low weight. Furthermore, the weave pat­tern affords excellent resistance to peeling and delamination, even when struck by lightning. Among the earliest aviation uses of composites were engine cowlings, but eventually, structural components and then entire composite airframes were envisioned. Composites can provide addi­tional electromagnetic resistance by winding conductive filaments in a spiral pattern over the structure before curing the resin. The filaments help dissipate high-voltage energy across a large area and rapidly divert the impulses before they can inflict significant harm.[171]

It is helpful to compare the effects of lightning on aluminum aircraft to better understand the advantage of fiberglass structures. Aluminum readily conducts electromagnetic energy through the airframe, requir­ing designers to channel the energy away from vulnerable areas, espe­cially fuel systems and avionics. The aircraft’s outer skin usually offers the path of least resistance, so the energy can be "vented” overboard. Fiberglass is a proven insulator against electromagnetic charges. Though composites conduct electricity, they do so less readily than do alumi­num and other metals. Consequently, though it may seem counterintu­itive, composites’ resistance to EMP strokes can be enhanced by adding small metallic mesh to the external surfaces, focusing unwanted currents away from the interior. The most common mesh materials are alumi­num and copper impressed into the carbon fiber. Repairs of lightning – damaged composites must take into account the mesh in the affected area and the basic material and attendant structure. Composites miti­gate the effect of a lightning strike not only by resisting the immediate area of impact, but also by spreading the effects over a wider area. Thus, by reducing the energy for a given surface area (expressed in amps per square inch), a potentially damaging strike can be rendered harmless.

Because technology is still emerging for detection and diagno­sis of lightning damage, NASA is exploring methods of in-flight and postflight analysis. Obviously, the most critical is in-flight, with aircraft sensors measuring the intensity and location of a lightning strike’s cur­rent, employing laboratory simulations to establish baseline data for a specific material. Thus, the voltage/current test measurements can be compared with statistical data to estimate the extent of damage likely upon the composite. Aircrews thereby can evaluate the safety of flight risks after a specific strike and determine whether to continue or to land.

NASA’s research interests in addressing composite aircraft are threefold:

• Deploying onboard sensors to measure lightning-strike strength, location, and current flow.

• Obtaining conductive paint or other coatings to facili­tate current flow, mitigating airframe structural dam­age, and eliminating requirements for additional internal shielding of electronics and avionics.

• Compiling physics-based models of complex compos­ites that can be adapted to simulate lightning strikes to quantify electrical, mechanical, and thermal parameters to provide real-time damage information.

As testing continues, NASA will provide modeling data to manufac­turers of composite aircraft as a design tool. Similar benefits can accrue to developers of wind turbines, which increasingly are likely to use com­posite blades. Other nonaerospace applications can include the electric power industry, which experiences high-voltage situations.[172]

In yet another example of NASA developing a database system with and for the FAA, the Performance Data Analysis and Reporting System (PDARS) began operation in 1999 with the goal of collecting, analyz­ing, and reporting of performance-related data about the National Airspace System. The difference between PDARS and the Aviation Safety Reporting System is that input for the ASRS comes voluntarily from people who see something they feel is unsafe and report it, while input for PDARS comes automatically—in real time—from electronic sources such as ATC radar tracks and filed flight plans. PDARS was created as an element of NASA’s Aviation Safety Monitoring and Modeling project.[239]

From these data, PDARS calculates a variety of performance mea­sures related to air traffic patterns, including traffic counts, travel times between airports and other navigation points, distances flown, gen­eral traffic flow parameters, and the separation distance from trailing

aircraft. Nearly 1,000 reports to appropriate FAA facilities are automat­ically generated and distributed each morning, while the system also allows for sharing data and reports among facilities, as well as facilitat­ing larger research projects. With the information provided by PDARS, FAA managers can quickly determine the health, quality, and safety of day-to-day ATC operations and make immediate corrections.[240]

The system also has provided input for several NASA and FAA stud­ies, including measurement of the benefits of the Dallas/Fort Worth Metroplex airspace, an analysis of the Los Angeles Arrival Enhancement Procedure, an analysis of the Phoenix Dryheat departure procedure, measurement of navigation accuracy of aircraft using area navigation en route, a study on the detection and analysis of in-close approach changes, an evaluation of the benefits of domestic reduced vertical separation minimum implementation, and a baseline study for the airspace flow program. As of 2008, PDARS was in use at 20 Air Route Traffic Control Centers, 19 Terminal Radar Approach Control facil­ities, three FAA service area offices, the FAA’s Air Traffic Control System Command Center in Herndon, VA, and at FAA Headquarters in Washington, DC.[241]

Steven A. Ruffin

The invention of flight exposed human limitations. Altitude effects endan­gered early aviators. As the capabilities of aircraft grew, so did the challenges for aeromedical and human factors researchers. Open cock­pits gave way to pressurized cabins. Wicker seats perched on the lead­ing edge of frail wood-and-fabric wings were replaced by robust metal seats and eventually sophisticated rocket-boosted ejection seats. The casual cloth work clothes and hats presaged increasingly complex suits.

S MERCURY ASTRONAUT ALAN B. SHEPARD, JR., lay flat on his back, sealed in a metal capsule perched high atop a Redstone rocket on the morning of May 5, 1961, many thoughts proba­bly crossed his mind: the pride he felt of becoming America’s first man in space, or perhaps, the possibility that the powerful rocket beneath him would blow him sky high. . . in a bad way, or maybe even a greater fear he would "screw the pooch” by doing something to embarrass him­self—or far worse—jeopardize the U. S. space program.

After lying there nearly 4 hours and suffering through several launch delays, however, Shepard was by his own admission not thinking about any of these things. Rather, he was consumed with an issue much more down to earth: his bladder was full, and he desperately needed to relieve himself. Because exiting the capsule was out of the question at this point, he literally had no place to go. The designers of his modified Goodrich

U. S. Navy Mark IV pressure suit had provided for nearly every contin­gency imaginable, but not this; after all, the flight was only scheduled to last a few minutes.

Finally, Shepard was forced to make his need known to the control­lers below. As he candidly described later, "You heard me, I’ve got to pee. I’ve been in here forever.”[286] Despite the unequivocal reply of "No!” to

his request, Shepard’s bladder gave him no alternative but to persist. Historic flight or not, he had to go—and now.

When the powers below finally accepted that they had no choice, they gave the suffering astronaut a reluctant thumbs up: so, "pee,” he did. . . all over his sensor-laden body and inside his gleaming silver spacesuit. And then, while the world watched—unaware of this behind- the-scenes drama—Shepard rode his spaceship into history. . . drenched in his own urine.

This inauspicious moment should have been something of an epiph­any for the human factors scientists who worked for the newly formed

National Aeronautics and Space Administration (NASA). It graphi­cally pointed out the obvious: human requirements—even the most basic ones—are not optional; they are real, and accommodations must always be made to meet them. But NASA’s piloted space program had advanced so far technologically in such a short time that this was only one of many lessons that the Agency’s planners had learned the hard way. There would be many more in the years to come.

As described in the Tom Wolfe book and movie of the same name, The Right Stuff, the first astronauts were considered by many of their contemporary non-astronaut pilots—including the ace who first broke the sound barrier, U. S. Air Force test pilot Chuck Yeager—as little more than "spam in a can.”[287] In fact, Yeager’s commander in charge of all the test pilots at Edwards Air Force Base had made it known that he didn’t particularly want his top pilots volunteering for the astronaut program; he considered it a "waste of talent.”[288] After all, these new astronauts— more like lab animals than pilots—had little real function in the early flights, other than to survive, and sealed as they were in their tiny metal capsules with no realistic means of escape, the cynical "spam in a can” metaphor was not entirely inappropriate.

But all pilots appreciated the dangers faced by this new breed of American hero: based on the space program’s much-publicized recent history of one spectacular experimental launch failure after another, it seemed like a morbidly fair bet to most observers that the brave astro­nauts, sitting helplessly astride 30 tons of unstable and highly explo­sive rocket fuel, had a realistic chance of becoming something akin to America’s most famous canned meat dish. It was indeed a dangerous job, even for the 7 overqualified test-pilots-turned-astronauts who had been so carefully chosen from more than 500 actively serving military test pilots.[289] Clearly, piloted space flight had to become considerably more human-friendly if it were to become the way of the future.

NASA had existed less than 3 years before Shepard’s flight. On July 19, 1958, President Dwight D. Eisenhower signed into law the National Aeronautics and Space Act of 1958, and chief among the provisions was the establishment of NASA. Expanding on this act’s stated purpose of conducting research into the "problems of flight within and outside the earth’s atmosphere” was an objective to develop vehicles capable of carrying—among other things—"living organisms” through space.[290]

Because this official directive clearly implied the intention of send­ing humans into space, NASA was from its inception charged with formulating a piloted space program. Consequently, within 3 years after it was created, the budding space agency managed to successfully launch its first human, Alan Shepard, into space. The astronaut com­pleted NASA Mercury mission MR-3 to become America’s first man in space. Encapsulated in his Freedom 7 spacecraft, he lifted off from Cape Canaveral, FL, and flew to an altitude of just over 116 miles before splashing down into the Atlantic Ocean 302 miles downrange.[291] It was only a 15-minute suborbital flight and, as related above, not without problems, but it accomplished its objective: America officially had a piloted space program.

This was no small accomplishment. Numerous major technological barriers had to be surmounted during this short time before even this most basic of piloted space flights was possible. Among these obstacles, none was more challenging than the problems associated with main­taining and supporting human life in the ultrahostile environment of space. Thus, from the beginning of the Nation’s space program and con­tinuing to the present, human factors research has been vital to NASA’s comprehensive research program.

By the 1980s, increasing airspace congestion had made the risk of cata­strophic midair collision greater than ever before. Consequently, the 100th Congress passed Public Law 100-223, the Airport and Airway Safety and Capacity Expansion Improvement Act of 1987. This required, among other provisions, that passenger-carrying aircraft be equipped with a Traffic Collision Avoidance System (TCAS), independent of air traffic control, that would alert pilots of other aircraft flying in their surrounding airspace.[395]

In response to this mandate, NASA, the FAA, the Air Transport Association, the Air Line Pilots Association, and various aviation technology industries teamed up to develop and evaluate such a system, TCAS I, which later evolved to the current TCAS II. From 1988 to 1992, NASA Ames Research Center played a pivotal role in this major collabor­ative effort by evaluating the human performance factors that came into play with the use of TCAS. By employing ground-based simulators oper­ated by actual airline flightcrews, NASA showed that this system was prac­ticable, at least from a human factors standpoint.[396] The crews were found to be able to accurately use the system. This research also led to improved displays and aircrew training procedures, as well as the validation of a set of pilot collision-evading performance parameters.[397] One example of the new technologies developed for incorporation into the TCAS system is the Advanced Air Traffic Management Display. This innovative system provides pilots with a three-dimensional air traffic virtual-visualization display that increases their situational awareness while decreasing their workload.[398] This visualization system has been incorporated into TCAS system displays and has become the industry standard for new designs.[399]

High-speed studies of dynamic stability were very active at Wallops. The scope and contributions of the Wallops rocket-boosted model research programs for aircraft configurations, missiles, and airframe components covered an astounding number of technical areas, including aerodynamic performance, flutter, stability and control, heat transfer, automatic controls, boundary-layer control, inlet performance, ramjets, and separation behav­ior of aircraft components and stores. As an example of test productivity, in just 3 years beginning in 1947, over 386 models were launched at Wallops to evaluate a single topic: roll control effectiveness at transonic conditions. These tests included generic configurations and models with wings repre­sentative of the historic Douglas D-558-2 Skyrocket, Douglas X-3 Stiletto, and Bell X-2 research aircraft.[471] Fundamental studies of dynamic stability and control were also conducted with generic research models to study basic phenomena such as longitudinal trim changes, dynamic longitudi­nal stability, control-hinge moments, and aerodynamic damping in roll.[472] Studies with models of the D-558-2 also detected unexpected coupling of longitudinal and lateral oscillations, a problem that would subsequently prove to be common for configurations with long fuselages and relatively small wings.[473] Similar coupled motions caused great concern in the X-3 and F-100 aircraft development programs and spurred on numerous stud­ies of the phenomenon known as inertial coupling.

More than 20 specific aircraft configurations were evaluated during the Wallops studies, including early models of such well-known aircraft as the Douglas F4D Skyray, the McDonnell F3H Demon, the Convair B-58 Hustler, the North American F-100 Super Sabre, the Chance Vought F8U Crusader, the Convair F-102 Delta Dagger, the Grumman F11F Tiger, and the McDonnell F-4 Phantom II.

High-speed dynamic stability testing techniques at the Ames SFFT included studies of the static and dynamic stability of blunt-nose reen­try shapes, including analyses of boundary-layer separation.[474] This work included studies of the supersonic dynamic stability characteristics of the Mercury capsule. Noting the experimental observation of nonlinear varia­tions of pitching moment with angle of attack typically exhibited by blunt bodies, Ames researchers contributed a mathematical method for includ­ing such nonlinearities in theoretical analyses and predictions of capsule dynamic stability at supersonic speeds. During the X-15 program, Ames conducted free-flight testing in the SFFT to define stability, control, and flow-field characteristics of the configuration at high supersonic speeds.[475]

Beginning in the early 1960s, a flurry of new military aircraft develop­ment programs resulted in an unprecedented workload for the drop – model personnel. Support was requested by the military services for the General Dynamics F-111, Grumman F-14, McDonnell-Douglas F-15, Rockwell B-1A, and McDonnell-Douglas F/A-18 development programs. In addition, drop-model tests were conducted in support of the Grumman

X-29 and the X-31—sponsored by the Defense Advanced Research Projects Agency (DARPA)—research aircraft programs, which were scheduled for high-angle-of-attack full-scale flight tests at the Dryden flight facility. The specific objectives and test programs conducted with the drop models were considerably different for each configura­tion. Overviews of the results of the military programs are given in this volume, in another case study by this author.