Category NASA’S CONTRIBUTIONS TO AERONAUTICS

By James Banke

The aerospace environment is a realm of extremes: low to high pres­sures, densities, and temperatures. Researchers have had the goal of improving flight efficiency and safety. Aircraft icing has been a prob­lem since the earliest days of flight and, historically, researchers have artfully blended theory, ground-and-flight research, and the use of new tools such as computer simulation and software modeling codes to ensure that travelers fly in aircraft well designed to confront this hazard.

NE FEBRUARY EVENING in the late 1930s, a young copilot strode across a cold ramp of the Nashville airport under a frigid moon­lit sky, climbing into a chilled American Airlines DC-2. The young airman was Ernest Gann, later to gain fame as a popular nov­elist and aviation commentator, whose best-remembered book, The High and the Mighty, became an iconic aviation film. His captain was Walter Hughen, already recognized by his peers as one of the greats, and the two men worked swiftly to ready the sleek twin-engine trans­port for flight. Behind them, eight passengers settled in, looked after by a flight attendant. They were bound for New York, along AM-23, an air route running from Nashville to New York City. Preparations com­plete, they taxied out and took off on what should have been a routine 4-hour flight in favorable weather. Instead, almost from the moment the airliner’s wheels tucked into the plane’s nacelles, the flight began to deteriorate. By the time they reached Knoxville, they were bucking an unanticipated 50-mile-per-hour headwind, the Moon had vanished, and the plane was swathed in cloud, its crew flying by instruments only. And there was something else: ice. The DC-2 was picking up a heavy load of ice from the moisture-laden air, coating its wings and engine cowlings, even its propellers, with a wetly glistening and potentially deadly sheen.[1197]

Suddenly there was "an erratic banging upon the fuselage,” as the propellers began flinging ice "chunks the size of baseballs” against the fuselage. In the cockpit, Hughen and Gann desperately fought to keep their airplane in the air. Its leading edge rubber deicing boots, which shattered ice by expanding and contracting, so that the airflow could sweep it away, were throbbing ineffectively: the ice had built up so thick and fast that it shrouded them despite their pulsations. Carburetor inlet icing was building up on each engine, causing it to falter, and only delib­erately induced back-firing kept the inlets clear and the engines run­ning. Deicing fluid spread on the propellers and cockpit glass had little effect, as did a hot air hose rigged to blow on the outside of the wind­shield. Worst of all, the heavy icing increased the DC-2’s weight and drag, slowing it down to near its stall point. At one point, the plane began "a sudden, terrible shudder,” perilously on the verge of a fatal stall, before Hughen slammed the throttles full-forward and pushed the nose down, restoring some margin of flying speed.[1198]

After a half hour of desperate flying that "had the smell of eternity” about it, the battered DC-2 and its drained crew entered clear skies. The weather around them was still foreboding, and so, after trying to return to Nashville, finding it was closed, and then flying about for hours searching for an acceptable alternate, they turned for Cincinnati, Hughen and Gann anxiously watching their fuel consumption. Ice— some as thick as 4 inches—still swathed the airplane, so much so that Gann thought, "Where are the engineers again? The wings should somehow be heated.” The rudder was frozen in place, and the elevators and ailerons (controlling pitch and roll) moveable only because of Hughen and Gann’s constant control inputs to ensure they remained free. At dawn they reached Cincinnati, where the plane, bur­dened by its heavy load of ice, landed heavily. "We hit hard,” Gann recalled,"and stayed earth-bound. There is no life left in our wings for bouncing.” Mechanics took "two hours of hard labor to knock the ice from our wings, engine cowlings, and empennage.” Later that day, Hughen and Gann completed the flight to New York, 5 hours late. In the remarks section of his log, explaining the delayed arrival, Gann simply penned "Ice.”[1199]

Gann, ever after, regarded the flight as marking his seasoning as an airman, "forced to look disaster directly in the face and stare it down.”[1200] Many others were less fortunate. In January 1939, Cavalier, an Imperial Airways S.23 flying boat, ditched heavily in the North Atlantic, breaking up and killing 3 of its 13 passengers and crew; survivors spent 10 cold hours in heaving rafts before being rescued. Carburetor icing while flying through snow and hail had suffocated two of its four engines, leaving the flying boat’s remaining two faltering at low power.[1201] In October 1941, a Northwest Airlines DC-3 crashed near Moorhead, MN, after the heavy weight of icing prevented its crew from avoiding terrain; this time 14 of 15 on the plane died.[1202]

Even when nothing went wrong, flying in ice was unsettling. Trans World Airlines Captain Robert "Bob” Buck, who became aviation’s most experienced, authoritative, and influential airman in bad weather fly­ing, recalled in 2002 that

A typical experience in ice meant sitting in a cold cockpit, windows covered over in a fan-shaped plume from the lower aft corner toward the middle front, frost or snow covering the inside of the windshield frames, pieces as large as eight inches growing forward from the wind­shield’s edges outside, hunks of ice banging against the fuselage and the airplane shaking as the tail swung left and right, right and left, and the action was transferred to the rudder pedals your feet were on so you felt them saw back and forth beneath you The side winds were frosted, but you could wipe them clear enough for a look out at the engines. The nose cowlings collected ice on their lead­ing edge, and I’ve seen it so bad that the ice built forward until the back of the propeller was shaving it! But still the airplane flew. The indicated airspeed would slow, and
you’d push up the throttles for more power to overcome the loss but it didn’t always take, and the airspeed some­times went down to alarming numbers approaching stall.[1203]

Icing, as the late aviation historian William M. Leary aptly noted, has been a "perennial challenge to aviation safety.”[1204] It’s a chilling fact that despite a century of flight experience and decades of research on the ground and in the air, today’s aircraft still encounter icing conditions that lead to fatal crashes. It isn’t that there are no preventative measures in place. Weather forecasting, real-time monitoring of conditions via sat­ellite, and ice prediction software are available in any properly equipped cockpit to warn pilots of icing trouble ahead. Depending on the size and type of aircraft, there are several proven anti-icing and de-icing systems that can help prevent ice from building up to unsafe levels. Perhaps most importantly, pilot training includes information on recognizing icing con­ditions and what to do if an aircraft starts to ice up in flight. Unfortunately the vast majority of icing-related incidents echo a theme in which the pilot made a mistake while flying in known icing conditions. And that shows that in spite of all the research and technology, it’s still up to the pilot to take advantage of the experience base developed by NASA and others over the years.

In the very earliest days of aviation, icing was not an immediate con­cern. That all changed by the end of the First World War, by which time airplanes were operating at altitudes above 10,000 feet and in a variety of meteorological conditions. Worldwide, the all-weather flying needs of both airlines and military air service, coupled with the introduction of blind-flying instrumentation and radio navigation techniques that enabled flight in obscured weather conditions, stimulated study of icing, which began to take a toll on airmen and aircraft as they increasingly operated in conditions of rain, snow, and freezing clouds and sleet.[1205]

The NACAs interest in icing dated to the early 1920s, when America’s aviation community first looked to the Agency for help. By the early 1930s, both in America and abroad, researchers were examining the pro­cess of ice formation on aircraft and means of furnishing some sort of surface coatings that would prevent its adherence, particularly to wings, acquiring data both in actual flight test and by wind tunnel studies. Ice on wings changed their shape, drastically altering their lift-to-drag ratios and the pressure distribution over the wing. An airplane that was per­fectly controllable with a clean wing might prove very different indeed with just a simple change to the profile of its airfoil.[1206] Various mechan­ical and chemical solutions were tried. The most popular mechanical approach involved fitting the leading edges of wings, horizontal tails, and, in some cases, vertical fins with pneumatically operated rubber "de-icing” boots that could flex and crack a thin coating of ice. As Gann and Buck noted, they worked at best sporadically. Other approaches involved squirting de-icing fluid over leading edges, particularly over propeller blades, and using hot-air hoses to de-ice cockpit windshields.

Lewis A. "Lew” Rodert—the best known of ice researchers—was a driven and hard-charging NACA engineer who ardently pursued using heat as a means of preventing icing of wings, propellers, carburetors, and windshields.[1207] Under Rodert’s direction, researchers extensively instrumented a Lockheed Model 12 light twin-engine transport for icing research and, later, a larger and more capable Curtiss C-46 transport. Rodert and test pilot Larry Clausing, both Minnesotans, moved the NACAs ice research program from Ames Aeronautical Laboratory (today the NASA Ames Research Center) to a test site outside Minneapolis. There, researchers took advantage of the often-formidable weather con­ditions to assemble a large database on icing and icing conditions, and

on the behavior of various modifications to their test aircraft. These tests complemented more prosaic investigations looking at specific icing problems, particularly that of carburetor icing.[1208]

The war’s end brought Rodert a richly deserved Collier Trophy, American aviation’s most prestigious award, for his thermal de-icing research, particularly the development and validation of the concept of air-heated wings.[1209] By 1950, a solid database of NACA research existed on icing and its effects upon propeller-driven airplanes.[1210] This led many to conclude that the "heroic era” of icing research was in the past, a judg­ment that would prove to be wrong. In fact, the problems of icing merely changed focus, and NACA engineers quickly assessed icing implications for the civil and military aircraft of the new gas turbine and transonic era.[1211] New high-performance interceptor fighters, expected to acceler­ate quickly and climb to high altitudes, had icing problems of their own, typified by inlet icing that forced performance limitations and required imaginative solutions.[1212] When first introduced into service, Bristol’s otherwise-impressive Britannia turboprop long-range transport had persistent problems caused by slush ice forming in the induction system of its Proteus turboprop engines. By the time the NACA evolved into the

National Aeronautics and Space Administration in 1958, the fundamen­tal facts concerning the types of ice an aircraft might encounter and the major anti-icing techniques available were well understood and widely in use. In retrospect, as impressive as the NACA’s postwar work in icing was, it is arguable that the most important result of NACA work was the establishment of ice measurement criteria, standards for ice-prevention systems, and probabilistic studies of where icing might be encountered (and how severe it might be) across the United States. NACA Technical Notes 1855 (1949) and 2738 (1952) were the references of record in estab­lishing Federal Aviation Administration (FAA) standards covering aircraft icing certification requirements.[1213]

Early NACA research on stalling and spinning in the 1920s quickly con­cluded that the primary factors that governed the physics of stall behav­ior, spin entry, and recovery from spins were very complicated and would require extensive commitments to new experimental facilities for stud­ies of aerodynamics and flight motions. Over the following 85 years, efforts by the NACA and NASA introduced a broad spectrum of spe­cialized tools and analysis techniques for high-angle-of-attack condi­tions, including vertical spin tunnels, pressurized wind tunnels to define the impact of Reynolds number on separated flow phenomena, special free-flight model test techniques, full-scale aircraft flight experiments, theoretical studies of aircraft motions, piloted simulator studies, and unique static and dynamic wind tunnel aerodynamic testing capability.[1275]

By the 1930s, considerable progress had been made at the NACA Langley Memorial Aeronautical Laboratory on obtaining wind tunnel aerodynamic data on the effectiveness of lateral control concepts at the stall and understanding control effects on motions.[1276] A basic understand­ing began to emerge on the effects of design variables for biplanes of the era, such as horizontal and vertical tail configurations, wing stagger,
and center-of-gravity location on spinning. Flight-testing of stall char­acteristics became a routine element of handling quality studies. In the race to conquer stall/spin problems, however, simplistic and regretta­ble conclusions were frequently drawn.[1277]

The sudden onset of World War II and its urgency for aeronauti­cal research and development overwhelmed the laboratory’s plodding research environment and culture with high-priority requests from the military services for immediate wind tunnel and flight assessments, as well as problem-solving activities for emerging military aircraft. At that time, the military perspective was that operational usage of high-angle – of-attack capability was necessary in air combat, particularly in classic "dogfight” engagements wherein tighter turns and strenuous maneu­vers meant the difference between victory and defeat. Tactical effective­ness and safety, however, demanded acceptable stalling and spinning behavior, and early NACA assessments for new designs prior to indus­try and military flight-testing and production were required for every new maneuverable aircraft.[1278] Spin demonstrations of prototype aircraft by the manufacturer were mandatory, and satisfactory stall character­istics and recoveries from developed spins required extensive testing by the NACA in its conventional wind tunnels and vertical spin tunnel.

The exhausting demands of round-the-clock, 7-day workweeks left very little time for fundamental research, but researchers at Langley’s Spin Tunnel, Free-Flight Tunnel, Stability Tunnel, and 7- by 10-Foot Tunnels initiated a series of studies that resulted in advancements in high-angle-of-attack design procedures and analysis techniques.[1279]

The advent of vertical flight required mastery of aerodynamics, pro­pulsion, and flight control technology. In the evolution of flight charac­terized by progressive development of the autogiro, helicopter, and various convertiplanes, the NACA and NASA have played a predom­inant role. NASA developed the theoretical underpinning for vertical flight, evaluated requisite technologies and research vehicles, and expanded the knowledge base supporting V/STOL flight technology.

NE OF THE MAJOR ACCOMPLISHMENTS in the history of avi­ation has been the development of practical Vertical Take-Off and Landing (VTOL) aircraft, exemplified by the emergence of the helicopter in the 1930s and early 1940s, and the vectored-thrust

jet airplane of the 1960s. Here indeed was a major challenge that con­fronted flight researchers, aeronautical engineers, military tacticians, and civilian planners for over 50 years, particularly those of the National Aeronautics and Space Administration (NASA) and its predecessor, the National Advisory Committee for Aeronautics (NACA). While perhaps not regarded by aviation aficionados as being as glamorous as the exper­imental craft that streaked to new speeds and altitudes, early vertical flight testbeds were likewise revolutionary at the other end of the perfor­mance spectrum, in vertical ascents and descents, low-speed controlla­bility, and hover, areas challenging accepted knowledge and practice in aerodynamics, propulsion, and flight controls and controllability.[1330]

The accomplishment of vertical flight was as challenging as inventing the airplane itself. Only four decades after Kitty Hawk were vertical take­off, hovering, and landing aircraft beginning to enter service. These were, of course, the first helicopters: successors to the interim rotary wing auto­giro that relied on a single or multiple rotors to give them Vertical/Short

Take-Off and Landing (V/STOL) performance. Before the end of the Second World War, the helicopter had flown in combat, proved its value as a life­saving craft, and shown its adaptability for both land – and sea-based operation.[1331] The faded promises of many machines litter the path to the modern V/STOL vehicle. The dedicated research accompanying this work nevertheless led to a class of flight craft that have expanded the use of civil and military aeronautics, saving the lives of nearly a half million people over the last seven decades. The oil rigger in the Gulf going on leave, the yachtsman waiting for rescue, and the infantryman calling in gunships to fend off attack can all thank the flight researchers, particularly those of the NACA and NASA, who made the VTOL aircraft possible.[1332]

Helicopters matured significantly during the Korean war, setting the stage for their pervasive employment in the war in Southeast Asia a decade later.[1333] Helicopters revolutionized warfare and became the iconic image of the Vietnam war. On the domestic front, outstanding helicop­ter research was being carried on at NASA Langley. Of particular note were the contributions of researchers and test pilots such as Jack Reeder, John P. Campbell, Richard E. Kuhn, Marion O. McKinney, and Robert

H. Kirby. In the late 1950s, military advisers realized how much of the Nation’s defense structure depended on a few large airbases and a few large aircraft carriers. Military interests were driven by the objective of achieving operations into and out of unprepared remotely dispersed sites independent of conventional airfields. Meanwhile, commercial air transportation organizations were pursuing ways to cut the amount of real estate required to accommodate new aircraft and long airstrips.[1334]

Since NASAs inception in 1958, its researchers at various Centers have advanced the knowledge base of V/STOL technology via many special­ized test aircraft and flying techniques. Some key discoveries include the realization that V/STOL aircraft must be designed with good Short Take­Off and Landing (STOL) performance capability to be cost-effective, and that, 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 at airports close to populated areas.

But NASA interest in fixed wing STOL and VTOL convertiplanes predates formation of the Agency, going back to the unsuccessful com­bined rotor and wing design by Emile and Henry Berliner tested at College Park Airport, MD, in the early 1920s. In the late 1930s and early 1940s, NACA researcher Charles Zimmerman undertook pioneer­ing research on such craft, his interest leading to the Vought V-173, popularly known as the "Flying Flapjack,” because of its peculiar near­circular wing shape. It led to an abortive Navy fighter concept, the Vought XF5U-1, which was built but never flown. The V-173, however, contrib­uted notably to the emerging understanding of V/STOL aircraft chal­lenges and performance. Aside from this sporadic interest, the Agency’s research staff did not place great emphasis upon such studies until the postwar era. Then, beginning in the early 1950s, a veritable explosion of interest followed, with a number of design studies and flight-test

programs undertaken at Langley and Ames laboratories (later the NASA Langley and Ames Research Centers). This interest corresponded to ris­ing interest in the military in the possibility of vertical flight vehicles for a variety of missions.

For example, the U. S. Navy sponsored two unsuccessful experimen­tal "Pogo” tail-sitting turboprop-powered VTOL fighters: the Lockheed XFV-1 and the Convair XFY-1. Only the XFY-1 subsequently operated in true VTOL mode, and flight trials indicated that neither represented a
reasonable approach to practical VTOL flight. The Air Force developed a pure-jet equivalent: the VTOL delta-winged Ryan X-13. Though widely demonstrated (even outside the Pentagon), it was equally impracticable.[1335] The U. S. Army’s Transportation and Research Engineering Command sponsored ducted-fan flying jeep and other saucerlike circular flying platforms by Avro and Hiller, with an equivalent lack of success. Overall, the Army’s far-seeing V/STOL testbed program, launched in 1956 and undertaken in cooperation with the U. S. Navy’s Office of Naval Research, advanced a number of so-called "VZ”-designated research aircraft explor­ing a range of technical approaches to V/STOL flight.[1336] NATO planners envisioned V/STOL close-air support, interdiction, and nuclear attack aircraft. This interest eventually helped spawn the British Aerospace Harrier strike fighter of the late 1960s and other designs that, though they entered flight-testing, did not prove suitable for operational service.[1337]

The United States Pilot Evaluation Team (USPET)[1477] arrived in Moscow on Sunday, September 6, 1998, and was met by Professor Alexander Pukhov and a delegation of Tupolev officials. (Ill fortune had struck the team when NASA Langley research pilot Robert Rivers severely broke his right leg and ankle 2 weeks before departure. Because visas for work in Russia required 60 days’ lead time and because no other pilot could be prepared in time, Rivers remained on the team, though it required a great deal of perseverance to obtain NASA approval. Tupolev pre­sented relatively few obstacles, by contrast, to Rivers’s participation.) Pukhov was the Tupolev Manager for the Tu-144 experiment and a for­mer engineer on the original design team for the airplane. At Pukhov’s insistence, USPET was billeted in Zhukovsky at the former KGB san­itarium. Sanitaria in the Soviet Union were rest and vacation spas for the various professional groups, and the KGB sanitarium was similar to a large hotel. The sanitarium was minutes from the Zhukovsky Air

Development Center and saved hours of daily commute time that oth­erwise might have been wasted had the team been housed in Moscow.

The next day began a very intense training period lasting 2 weeks but was punctuated September 15 by the first flight by American pilots, a subsonic sojourn. The training was complicated by the language differ­ences but was facilitated by highly competent Russian State Department translators. Nevertheless, humorous if not frustrating problems arose when nontechnical translators attempted to translate engineering and piloting jargon with no clear analogs in either language. The training consisted of one-on-one sitdown sessions with various Tu-144 systems experts using manuals and charts written in Russian. There were no English language flight or systems manuals for the Tu-144, and USPET’s attempt over the summer to procure a translated Tu-144 flight manual was unsuccessful. Training included aircraft systems, life support, and flight operations. Because flights would achieve altitudes of 60,000 feet and because numerous hull penetrations had occurred to accommodate the instrumentation system, all members of the flightcrew wore partial pressure suits. Because of the experimental nature of the flights, a man­ual bailout capability had been incorporated in the Tu-144. This involved dropping through a hatch just forward of the mammoth engine inlets. The hope was that the crewmember would pass between the two banks of engines without being drawn into the inboard inlets. Thankfully, this theory was never put to the test.

Much time was spent with the Tupolev flightcrew for the experi­ment, and great trust and friendship ensued. Tupolev chief test pilot Sergei Borisov was the pilot-in-command for all of the flights. Victor Pedos was the navigator, in actuality a third pilot, and Anatoli Kriulin was the flight engineer. Tupolev’s chief flight control engineer, Vladimir Sysoev, spent hours each day with USPET working on the test plan for each pro­posed flight. Sysoev and Borisov represented Tupolev in the negotiations to perform the maneuvers requested by the various researchers.[1478] An effective give-and-take evolved as the mutual trust grew. From Tupolev’s perspective, the Tu-144 was a unique asset, into which the fledgling free- market company had invested millions of dollars. It provided badly needed funds at a time when the Russian economy was struggling, and

the payments from NASA via Boeing and IBP were released only at the completion of each flight. The Tupolev crewmembers could not afford to risk the airplane. At the same time, they were anxious to be as coop­erative as possible. Careful and inventive planning resulted in nearly all of the desired test points being flown.

James Banke

Since 1926 and the passage of the Air Commerce Act, the Federal Government has had a vital commitment to aviation safety. Even before this, however, the NACA championed regulation of aeronau­tics, the establishment of licensing procedures for pilots and aircraft, and the definition of technical criteria to enhance the safety of air operations. NASA has worked closely with the FAA and other aviation organizations to ensure the safety of America’s air transport network.

HEN THE FIRST AIRPLANE LIFTED OFF from the sands of Kitty Hawk during 1903, there was no concern of a midair collision with another airplane. The Wright brothers had the North Carolina skies all to themselves. But as more and more aircraft found their way off the ground and then began to share the increasing num­ber of new airfields, the need to coordinate movements among pilots quickly grew. As flight technology matured to allow cross-country trips, methods to improve safe navigation between airports evolved as well. Initially, bonfires lit the airways. Then came light towers, two-way radio, omnidirectional beacons, radar, and—ultimately—Global Positioning System (GPS) navigation signals from space.[181]

Today, the skies are crowded, and the potential for catastrophic loss of life is ever present, as more than 87,000 flights take place each day over the United States. Despite repeated reports of computer crashes or bad weather slowing an overburdened national airspace system, air- related fatalities remain historically low, thanks in large part to the technical advances developed by the National Aeronautics and Space Administration (NASA), but especially to the daily efforts of some 15,000 air traffic controllers keeping a close eye on all of those airplanes.[182]

All of those controllers work for, or are under contract to, the Federal Aviation Administration (FAA), which is the Federal agency respon­sible for keeping U. S. skyways safe by setting and enforcing regula­tions. Before the FAA (formed in 1958), it was the Civil Aeronautics Administration (formed in 1941), and even earlier than that, it was the Department of Commerce’s Aeronautics Bureau (formed in 1926). That that administrative job today is not part of NASA’s duties is the result of decisions made by the White House, Congress, and NASA’s prede­cessor organization, the National Advisory Committee for Aeronautics (NACA), during 1920.[183]

At the time (specifically 1919), the International Commission for Air Navigation had been created to develop the world’s first set of rules for governing air traffic. But the United States did not sign on to the con­vention. Instead, U. S. officials turned to the NACA and other organiza­tions to determine how best to organize the Government for handling

all aspects of this new transportation system. The NACA in 1920 already was the focal point of aviation research in the Nation, and many thought it only natural, and best, that the Committee be the Government’s all­inclusive home for aviation matters. A similar organizational model existed in Europe but didn’t appear to some with the NACA to be an ideal solution. This sentiment was most clearly expressed by John F. Hayford, a charter member of the NACA and a Northwestern University engineer, who said during a meeting, "The NACA is adapted to function well as an advisory committee but not to function satisfac­torily as an administrative body.”[184]

So, in a way, NASA’s earliest contribution to making safer skyways was to shed itself of the responsibility for overseeing improvements to and regulating the operation of the national airspace. With the FAA secure in that management role, NASA has been free to continue to play to its strengths as a research organization. It has provided techni­cal innovation to enhance safety in the cockpits; increase efficiencies along the air routes; introduce reliable automation, navigation, and com­munication systems for the many air traffic control (ATC) facilities that dot the Nation; and manage complex safety reporting systems that have required creation of new data-crunching capabilities.

This case study will present a survey in a more-or-less chronolog­ical order of NASA’s efforts to assist the FAA in making safer skyways. An overview of key NASA programs, as seen through the eyes of the FAA until 1996, will be presented first. NASA’s contributions to air traffic safety after the 1997 establishment of national goals for reducing fatal air acci­dents will be highlighted next. The case study will continue with a sur­vey of NASA’s current programs and facilities related to airspace safety and conclude with an introduction of the NextGen Air Transportation System, which is to be in place by 2025.

When NASA’s Aviation Safety Program was begun in 1997, the agency joined with a large group of aviation-related organizations from Government, industry, and academia in forming a Commercial Aviation Safety Team (CAST) to help reduce the U. S. com­mercial aviation fatal accident rate by 80 percent in 10 years. During those 10 years, the group analyzed data from some 500 accidents and thou­sands of safety incidents and helped develop 47 safety enhancements.[249] In 2008, the group could boast that the rate had been reduced by 83 percent, and for that, CAST was awarded avi­ation’s most prestigious honor, the Robert J. Collier Trophy.

The interface between humans and technology was no less important for those early pioneers, who, for the first time in history, were start­ing to reach for the sky. Human factors research in aeronautics did not, however, begin with the Wright brothers’ first powered flight in 1903; it began more than a century earlier.

Much of this early work dealt with the effects of high altitude on humans. At greater heights above the Earth, barometric pressure decreases. This allows the air to expand and become thinner. The net effect is diminished breathable oxygen at higher altitudes. In humans operating high above sea level without supplemental oxygen, this trans­lates to a medical condition known as hypoxia. The untoward effects on humans of hypoxia, or altitude sickness, had been known for centu­ries—long before man ever took to the skies. It was a well-known entity to ancient explorers traversing high mountains, thus the still commonly used term mountain sickness.[298]

The world’s first aeronauts—the early balloonists—soon noticed this phenomenon when ascending to higher altitudes; eventually, some of the early flying scientists began to study it. As early as 1784, American physician John Jeffries ascended to more than 9,000 feet over London with French balloonist Jean Pierre Blanchard.[299] During this flight, they recorded changes in temperature and barometric pressure and became perhaps the first to record an "aeromedical” problem, in the form of ear pain associated with altitude changes.[300] Another early flying doctor, British physician John Shelton, also wrote of the detrimental effects of high-altitude flight on humans.[301]

During the 1870s—with mankind’s first powered, winged human flight still decades in the future—French physiologist Paul Bert conducted important research on the manner in which high – altitude flight affects living organisms. Using the world’s first pressure chamber, he studied the effects of varying barometric pressure and oxygen levels on dogs and later humans—himself included. He conducted 670 experiments at simulated altitudes of up to 36,000 feet. His findings clarified the effects of high-altitude conditions on humans and established the requirement for supplemental oxygen at higher altitudes.[302] Later studies by other researchers followed, so that by the time piloted flight in powered aircraft became a reality at Kitty Hawk, NC, on December 17, 1903, the scientific community already had a substantial amount of knowledge concerning the physiology of high-altitude flight. Even so, there was much more to be learned, and additional research in this important area would continue in the decades to come.

From the foregoing, it is clear that NASA’s human factors research has over the past decades specifically focused on aviation safety. This work, however, has also maintained an equally strong focus on improving the human-machine interface of aviation professionals, both in the air and on the ground. NASA has accomplished this through its many highly devel­oped programs that have emphasized human-centered considerations in the design and engineering of increasingly complex flight systems.

These human factors considerations in systems design and integration have directly translated to increased human performance and efficiency and, indirectly, to greater flight safety. The scope of these contributions is [421] [422]

best illustrated by briefly discussing a representative sampling of NASA programs that have benefitted aviation in various ways, including the Man – Machine Integration Design and Analysis System (MIDAS), Controller – Pilot Data Link Communications (CPDLC), NASA’s High-Speed Research (HSR) program, the Advanced Air Transportation Technologies (AATT) program, and the Agency’s Vision Science and Technology effort.

The selection of blunt capsule designs for the Mercury, Gemini, and Apollo programs resulted in numerous investigations of the dynamic stability and recovery of such shapes. Nonlinear, unstable varia­tions of aerodynamic forces and moments with angle of attack and sideslip were known to exist for these configurations, and extensive conventional force tests, dynamic free-flight model tests, and analyti­cal studies were conducted to define the nature of potential problems that might be encountered during atmospheric reentry. At Ames, the supersonic and hypersonic free-flight aerodynamic facilities have been used to observe dynamic stability characteristics, extract aero­dynamic data from flight tests, provide stabilizing concepts, and develop mathematical models for flight simulation at hypersonic and supersonic speeds.

Meanwhile, at Langley, researchers in the Spin Tunnel were con­ducting dynamic stability investigations of the Mercury, Gemini, and Apollo capsules in vertically descending subsonic flight.[492]

Results of these studies dramatically illustrated potential dynamic stability issues during the spacecraft recovery procedure. For example, the Gemini capsule model was very unstable; it would at various times oscillate, tumble, or spin about a vertical axis with its symmetrical axis tilted as much as 90 degrees from the vertical. However, the deployment of a drogue parachute during any spinning or tumbling motions quickly terminated these unstable motions at subsonic speeds. Extensive tests of various drogue-parachute configurations resulted in definitions of acceptable parachute bridle-line lengths and attachment points. Spin Tunnel results for the Apollo command module configuration were even more dramatic. The Apollo capsule with blunt end forward was dynam­ically unstable and displayed violent gyrations, including large oscilla­tions, tumbling, and spinning motions. With the apex end forward, the capsule was dynamically stable and would trim at an angle of attack of about 40 degrees and glide in large circles. Once again, the use of a drogue parachute stabilized the capsule, and the researchers also found that retention of the launch escape system, with either a drogue para­chute or canard surfaces attached to it, would prevent an unacceptable apex-forward trim condition during launch abort.

Following the Apollo program, NASA conducted a considerable effort on unpiloted space probes and planetary exploration. In the Langley Spin Tunnel, several planetary-entry capsule configurations were tested to evaluate their dynamic stability during descent, with a priority in simulating descent in the Martian atmosphere.[493] Studies also included assessments of the Pioneer Venus probe in the 1970s. These tests pro­vided considerable design information on the dynamic stability of a vari­ety of potential planetary exploration capsule shapes. Additional studies

of the stability characteristics of blunt, large-angle capsules were con­ducted in the late 1990s in the Spin Tunnel.

As the new millennium began, NASA’s interests in piloted and unpi­loted planetary exploration resulted in additional studies of dynamic sta­bility in the Spin Tunnel. Currently, the tunnel and its dynamic model testing techniques are supporting NASA’s Constellation program for

lunar exploration. Included in the dynamic stability testing are the Orion launch abort vehicle, the crew module, and alternate launch abort systems.[494]

One of the more impressive advances in aerospace capability in the last few years has been the acceptance and accelerated development of remotely piloted unmanned aerial vehicles (UAVs) by the military. The progress in innovative hardware and software products to support this focus has truly been impressive and warrants a consideration that properly scaled free – flight models have reached the appropriate limits of development. In com­parison to today’s capabilities, the past equipment used by the NACA and NASA seems primitive. It is difficult to anticipate hardware breakthroughs in free-flight model technologies beyond those currently employed, but NASA’s most valuable contributions have come from the applications of the models to specific aerospace issues—especially those that require years of difficult research and participation in model-to-flight correlation studies.

Changes in the world situation are now having an impact on aero­nautics, with a trickle-down effect on technical areas such as free-flight

testing. The end of the Cold War and industrial mergers have resulted in a dramatic reduction in new aircraft designs, especially for uncon­ventional configurations that would benefit from free-flight testing. Reductions in research budgets for industry and NASA have further aggravated the situation.

These factors have led to a slowdown in requirements for the ongoing NASA capabilities in free-flight testing at a time when rollover changes in the NASA workforce is resulting in the retirements of specialists in this and other technologies without adequate transfer of knowledge and mentoring to the new research staffs. In addition, planned closures of key NASA facilities will challenge new generations of researchers to reinvent the free-flight capabilities discussed herein. For example, the planned demolition of the Langley Full-Scale Tunnel in 2009 will terminate that historic 78-year-old facility’s role in providing free-flight testing capa­bility, and although exploratory free-flight tests have been conducted in the much smaller test section of the Langley 14- by 22-Foot Tunnel, it remains to be seen if the technique will continue as a testing capa­bility. Based on the foregoing observations, NASA will be challenged to provide the facilities and expertise required to continue to provide the Nation with contributions from free-flight models.