Civil Aeronautics: 100 Years of Discovery and Innovation at Langley Research Center

CIVIL AERONAUTICS:

100 Years of Discovery and Innovation at Langley Research Center

It’s been more than a century since the Wright brothers invented the first successful airplane, and, like many of history’s most celebrated events, their flights at Kitty Hawk have become shrouded in mythology. Orville and Wilbur Wright were humble sons of a Midwestern clergyman, the myth goes, tinkering bicycle mechanics who became fascinated with flight long before anyone else took it seriously.

The truth is actually more interesting. The Wrights were among thousands of people trying to solve the problems of powered heavier-thanair flight around the turn of the 20th century. At the time, some of the Western world’s most prestigious institutions were placing bets on the contestants – including the U.S. military, which granted inventor and Smithsonian Institution Secretary Samuel P. Langley $50,000 for flight research. The Wrights beat all of these competitors for one simple reason: They had better data.

The Wrights were brilliant, meticulous engineers. Their earliest flight experiments failed, in part, because they were relying on a lift coefficient – a ratio of air pressure on a wing to the speed of air moving over it – calculated by an 18th-century Englishman. They decided to start from scratch and do their own calculations, building their own wind tunnel and equipping it with instruments that would measure forces operating on model wings. Beginning in the fall of 1901, they tested more than 200 wing designs in their tunnel and came up with new configurations for their flying machines.

The U.S. government didn’t take much interest in the Wrights’ achievement at first, but World War I made flight research seem much more urgent. Beginning in 1915, Congress created the National Advisory Committee for Aeronautics (NACA) and set aside 1,650 acres of land in Hampton, Virginia, for an aeronautical research laboratory and airfield. Construction of the first building of what would become known as the Langley Memorial Aeronautical Laboratory, named for the late aeronautics pioneer, was begun in 1917.

From the start, Langley’s aeronautical research program focused largely on aerodynamics, and on doing research the Wright way: that is, using the wind tunnel as a primary instrument of study, and validating wind tunnel data in flight tests at adjacent Langley Field. By 1934, the Langley Laboratory had constructed seven wind tunnels, including the massive 30-by-60- foot Full-Scale Tunnel, then the world’s largest. In less than two decades, Langley was home to the greatest aeronautical research capability in the world.

The Boeing ecoDemonstrator 757 flight-test airplane makes a final approach to King County Boeing Field in Seattle, Washington, during the Active Flow Control Enhanced Vertical Tail Flight Experiment. Thirty-one sweeping jet actuators were installed on the aircraft’s vertical tail to see whether the size of the vertical tail could be reduced if such a system were used, which would mean greater fuel efficiency.

Boeing Photo By John D. Parker

The world’s first pressurized tunnel, Langley’s Variable Density Tunnel (VDT), became a particularly valuable tool, capable of creating aerodynamic data that could be scaled up to 20 times the size of tunnel models. This allowed the NACA to obtain data for airfoils (lift-inducing aircraft parts such as wings and fins) that simulated full-scale flight conditions. An entire portfolio of airfoils, known as the NACA airfoils, was generated from VDT studies led by Eastman Jacobs, Langley’s brilliant aerodynamicist, and earned the committee a reputation as one of the world’s preeminent aeronautical research institutions.

One of Langley’s greatest early contributions to aeronautics came from work done in Langley’s 20-foot Propeller Research Tunnel. After World War I, most American planes used air-cooled radial engines, with cylinders arranged around a central crankshaft. In this configuration, exposed cylinders created considerable drag. The drawbacks associated with heavier liquid-cooled engines, however, were even more significant, especially for the Navy, whose planes had to withstand abrupt landings on aircraft carrier decks. The Navy asked the NACA to look into the possibility of using a circular covering, or cowling, to reduce the drag created by radial engines, while still allowing adequate cooling.

The Propeller Research Tunnel, with its 20-foot radius, enabled testing on a full-sized airplane, and Langley technician Fred Weick, after hundreds of tests over a period of three years, produced a cowling that significantly reduced drag and, in directing rapid airflow around the engine’s hottest components, actually improved cooling. When Weick fitted his cowling around the engine of a Curtiss Hawk AT- 5A biplane, the result was astonishing: The Hawk’s top speed jumped from 118 to 137 miles per hour, a 16 percent increase.

Among the first civil aviation beneficiaries of Langley research was the Lockheed Vega Air Express, a civil airliner and the first production aircraft fitted with the NACA cowling.

NASA Photo

The NACA cowling was a crowning achievement for Langley technicians. It reduced drag by as much as 60 percent and saved the aircraft industry millions of dollars. In 1929, the cowling earned Weick Langley’s first Robert J. Collier trophy, an honor bestowed annually by the National Aeronautics Association for the most significant contributions to aeronautics research.

Safe, Efficient Civil Transport

By 1932, virtually every radial-engine aircraft was equipped with a variant of the NACA cowling. It was one of many innovations in aeronautics that led a growing number of Americans to consider aircraft as a reasonable alternative to other forms of transit. In the wind tunnels and over Langley Field, technicians directed studies of – and suggested improvements in – new models manufactured by companies such as Boeing, Douglas, Martin, and Curtiss.

In the 1930s and early 1940s, Jacobs and colleagues perfected what became known as the “laminar flow airfoil” for propeller-driven planes, wings designed to allow smooth flow over the wing surface, without the trailing-edge turbulence that slowed aircraft at high speeds. The design of World War II’s second-fastest propeller-driven aircraft, the North American P-51 Mustang, became the first aircraft to use Jacobs’ laminarflow airfoil.

The NACA’s aeronautics research was transformed by the approach of World War II. In 1940, the committee established two new laboratories. Ames, near San Francisco, was viewed as a West Coast counterpart to Langley, and Lewis (now Glenn), in Cleveland, focused on engine research. The war introduced an era in which the NACA laboratories focused not on advancing aeronautical knowledge overall, but on solving specific problems – a research posture intensified by the Cold War that followed. Langley and other research centers began studying rocketry and high-speed flight, and then the Soviet Union’s 1957 launch of the Sputnik satellite led to the transformation of the NACA into the National Aeronautics and Space Administration (NASA). Langley, Ames and Lewis became Research Centers, an acknowledgement that their investigations would extend beyond atmospheric flight.

Langley researchers contributed several important – and life-saving – findings to the aeronautics industry in the latter half of the 20th century. One of the first came after two fatal crashes of the nation’s first large turboprop airliner, the Lockheed L-188 Electra, in 1959 and 1960. Tests in one of Langley’s new generation of transonic wind tunnels – the Transonic Dynamics Tunnel (TDT) – established that the Electra’s wings could be stressed to the breaking point by a phenomenon known as “propeller whirl flutter,” an oscillation caused by the outboard engines when the aircraft reached transonic speed. In response, the company redesigned the Electra’s wing. For many aircraft manufacturers, flutter evaluations in the TDT became a requisite step in the development of new aircraft.

Langley also played a pivotal role in the transition from manual flight controls, such as the yoke and rudder pedals used to steer, and throttle linked directly to the engine, to an electronic “flyby-wire” (FBW) system. In FBW, digital signals move actuators that provide the ordered response – a movement of ailerons or acceleration of an engine, for example.

In 1954, flight tests of the first fly-by-wire aircraft, a modified F9F Panther jet, were initiated at Langley. Later, working closely with NASA’s Dryden Flight Research Center (now Armstrong Flight Research Center) in Edwards, California, the first digital fly-by-wire fixed-wing aircraft without a mechanical backup, a modified F-8 Crusader, made its first flight on May 25, 1972. Digital fly-by-wire is currently used in a variety of aircraft ranging from F/A-18 fighters to the Boeing 777.

Electronic displays and onboard computers were among many technological components evaluated aboard Langley’s “Flying Laboratory,” a Boeing 737 that entered service in 1974. Over 20 years of service life, the Flying Laboratory provided real-world demonstrations of new technologies, including some of the first airborne evaluations of the Global Positioning System (GPS) satellite network.

In a Langley-directed study, an F-106 aircraft flies through thunderstorm clouds to measure the effects of lightning on electronic controls.

NASA Photo

One of the most important Langley contributions to be achieved through 737 flight tests was the development of an airborne system to detect wind shear – a sudden microburst or downdraft, associated with thunderstorms, that could prove powerful enough to slam a plane into the ground during takeoff or landing. More than 540 airline passengers were killed from 1964 through 1994 in wind shear accidents. Langley researchers teamed up with partners from the Federal Aviation Administration (FAA) and industry to characterize wind shear threat to particular aircraft. The team developed remote-sensing technology that provided accurate wind shear detection, and easily readable cockpit displays that enabled rapid pilot response to a wind shear threat. Five separate wind shear detection technologies were tested aboard the Flying Laboratory. With an FAA standard now in place for airborne wind shear sensors, the accidents that once killed so many rarely happen.

Another thunderstorm-related aircraft hazard, lightning, was evaluated during Langley’s Storm Hazards Research Program, conducted from 1979- 1986. Langley test pilots, in an F-106 interceptor modified – “lightning hardened” – to fly directly into thunderstorms, flew into nearly 1,500 storms over the course of the program, absorbing a total of 714 lightning strikes. During one flight over North Carolina, the plane set a record for the most strikes in one flight: 72. Today’s existing lightning-protection standards, for both aircraft structures and instrumentation, were born from this study.

Other important Langley contributions during the 20th century included:

• Studies of water buildup on airport runways that resulted in today’s grooved surfaces hydroplaning prevention, and the development of an International Runway Friction Index used to assess runway safety in winter.

• Wind tunnel tests that led to a better understanding of how the loudest airframe components – the flaps, slats, and landing gear – generate noise, and the development of noise prediction tools that helped manufacturers design quieter aircraft.

• Evaluations, both in flight tests and in the 20-foot Spin Tunnel, of a spin-resistant wing that led to much safer small private planes.

• Evaluation and testing of non-invasive imaging technology to scan older aircraft for structural fatigue.

• With industry partners, further development of flyby-wire concepts into the “glass cockpit,” featuring digital displays rather than traditional dials and gauges. Langley pioneered the glass cockpit in ground simulators and aboard demonstration flights of the 737 Flying Laboratory; based on that work, and an enthusiastic response from industry, Boeing began to develop the first glass cockpits for airliners. By the end of the 1990s, flat-panel displays were increasingly favored among aircraft manufacturers, and the glass cockpit has become standard aboard commercial airliners and business jets.

NASA Langley Research Center’s 737 “Flying Laboratory” flighttested sensors to give advance warning of wind shear, a hazard that had claimed more than 540 lives over 30 years before the technologies were introduced.

NASA Photo

Next-Generation Systems

It was 1980 when the fresh college graduate George Finelli, today’s head of Langley’s Aeronautics Research Directorate, came to work for the center. At the time, the challenges being worked out around the glass cockpit had more to do with computing than with displays.

“It was interesting,” said Finelli. “From the ’80s into the ’90s, computing technology was expanding. 757s and 767s were the newest airplanes when I started working at Langley, and they had a lot of computers, but they were all segregated – they were designed not to interfere with each other, because at the time everything coming in was new, and the FAA was still learning what it meant to integrate digital systems into the operation of the airplane.”

It may be an understatement to say it’s a different story today. “By the time the 777 came along in the mid-’90s,” Finelli said, “the paradigm had shifted. There was a central flight management computer, with triply redundant software. The work here at Langley has had a lot to do with the community being able to move to that kind of computing paradigm – and technology has changed a lot more since then.”

In the fourth decade of his career, Finelli said he’s now witnessing another paradigm shift.

“I really believe aviation is on a precipice of change,” he said.

It isn’t just the onboard systems that are becoming more integrated; aircrew systems are increasingly connected to a larger network that extends upward to navigation satellites, downward to air traffic control systems, and across the sky to other aircraft. At the same time, networking technologies are enabling the number of unmanned aerial vehicles (UAVs, or “drones”) in U.S. skies to grow exponentially. In March 2017, the FAA announced that more than 770,000 drone registrations had been filed in the previous 15 months.

According to Finelli, this technological surge has changed the way NASA thinks about U.S. airspace. In the old days of the NACA, he said, Langley’s research was focused on airplanes; the unofficial catchphrase was, “Higher, Faster, Farther.” Today, researchers are investigating ways to expand the availability and efficiency of commercial flight. The unofficial catchphrase is now “Anybody, Anywhere, Anytime.”

“I think the technologies are flowing together,” Finelli said. “Things like autonomy, new ways to power small vehicles, and the new kinds of materials we can build things out of are enabling us to start talking about anybody, anywhere, anytime.”

Efficiency and safety are the key concerns for an air transport system that relies on interconnected networks while its passenger and cargo loads continue to increase. Langley researchers have been at the forefront of developing technologies to assure safe and efficient operations of aircraft, both independently and as components of a national airspace that’s in a state of continuous transformation.

One of the technologies in development at Langley, for example, is synthetic vision: software and systems that can help visualize external environments that are obscured, either by weather or by the flight deck configuration. Using geospatial data collected by the space shuttle program, researchers in Langley’s Crew Systems and Aviation Operations Branch have developed three-dimensional images of the Earth’s terrain. “We ended up getting it down to a meter – for every square meter, we had an elevation point,” said Kyle Ellis, a research engineer in the Branch.

Langley’s “Greased Lightning” demonstrator in vertical flight. The experimental, battery-powered drone, originally designed to prove concepts that could scale up to a diesel-electric single-passenger vertical takeoff and landing (VTOL) aircraft, is being used as a testbed to assess unmanned aircraft systems technology.

NASA Photo

“And with that database we could actually draw up synthetic terrain, like a computer does for Microsoft Flight Simulator.”

In its purest form, a synthetic vision system would take the place of a windshield and present an aircrew with an image of the outside world. Because it’s a static technology, however – “It won’t see deer on the runway, or another airplane out there, unless you give it some other information,” Ellis said – it’s usually used in combination with sensory systems, such as radar or infrared, to provide enhanced vision of the dynamic exterior world. “Langley has done a lot of research in combined vision displays,” said Ellis. “Right now FedEx’s whole fleet is equipped with enhanced flight vision systems. They’re able to go out and to fly into runways that other conventional aircraft can’t, because they can see the runway environment.” Aside from the obvious safety benefit, enhanced vision saves FedEx and other carriers time – and money – that would otherwise be spent dealing with delays.

In February 2017, a research team involving investigators from Langley and Ames, along with Boeing, Honeywell, and United Airlines, successfully tested a new cockpit-based air traffic management tool, known as Flight Deck Interval Management (FIM). The prototype hardware/software system is designed to provide pilots with precise, up-to-the-second spacing information on approach into a busy airport, allowing more planes to land safely in a given period of time. When rolled out commercially, FIM promises to save fuel, reduce emissions, and get more passengers to their destinations on schedule.

A Langley/industry team recently developed a tool that builds on the capabilities of FIM to help flight crews determine the most efficient flight paths to their destinations. The Traffic Aware Planner (TAP) analyzes the current airspace and prompts flight crews to request a route change. The Langley team shared NASA’s 2016 Software of the Year Award.

TAP is still in the developmental stages, but it’s one in a new suite of tools that Ellis said will “open up a whole new era for these airline industries to say, ‘We really are weather immune now. We don’t have to divert this airplane and essentially pay for all these passengers to be delayed.’ These systems will have a huge economic impact and a big safety impact.”

Langley’s work with high aspect ratio airfoils has been crucial to the development of the X-57, an allelectric research aircraft designed for high-efficiency flight.

NASA Image

The Aircraft of the Future

According to the FAA, U.S. airlines, which serve more than 750 million passengers every year, will serve a billion annually by 2029. Worldwide, NASA estimates about 3.6 billion passengers fly on commercial airliners – a number expected to double by the mid- 2030s.

Such enormous growth will require a generation of aircraft that achieve reductions in fuel use, emissions, and noise that go far beyond what can be achieved with today’s technologies. Langley researchers play a significant role in NASA’s Advanced Air Transport Technology (AATT) Project, aimed at ambitious “stretch” goals to be achieved over the next two decades: a 60 percent reduction in fuel/energy consumption (over the best 2005 aircraft); an 80 percent reduction in nitrogen oxide (NOx) emissions; and a cumulative 52-decibel noise reduction below the current FAA stage 4 noise standard.

Langley’s work in evaluating AATT concept aircraft is in many ways an echo of its early days in pioneering the NACA airfoils of the 1930s and 1940s: Models of planes conceptualized by industrial and academic teams are evaluated at Langley using what Finelli refers to as the “threelegged stool” of aeronautics research: computational modeling, wind tunnel testing, and flight testing. In particular, Finelli said, Langley has been a key contributor to the design and evaluation of two airframe features that could result in dramatic reductions in drag – and corresponding improvements in efficiency:

The high aspect ratio wing. Basically long skinny wings, like those of albatrosses, convey the major advantage of creating less drag – but corresponding disadvantages in strength, maneuverability, and the aeroelastic “flutter” that Langley technicians first investigated in the Transonic Dynamics Tunnel in the 1960s. Langley researchers are working with industry partners to strengthen high aspect ratio wings to an extent that allows them to be of practical use, and the TDT remains an important tool for examining flutter.

Langley’s work in high aspect ratio airfoils has been crucial in the design of the all-electric research plane known as the X-57 and nicknamed “Maxwell.” Maxwell features a long, thin wing embedded with 14 electric motors: 12 on the leading edge, to increase lift during takeoffs and landings, and two larger ones at the wing tips to propel the plane at cruising altitude.

Laminar flow control. Considered a kind of Holy Grail for aerodynamicists, laminar flow control, as Jacobs demonstrated decades ago, can be passively achieved by reconfiguring an airfoil. Langley researchers originated the concept of active laminar flow – directing airflow over a boundary layer to “catch” and redirect potential turbulence. In 2015, an active flowcontrol system – 31 small jet actuators, mounted on the tail and rudder of the Boeing 757 ecoDemonstrator – was evaluated in a series of flight tests, confirming wind tunnel tests suggesting aircraft manufacturers could, in future aircraft designs, shrink the size of tail structures, and reduce drag, using this technology.

The ecoDemonstrator also flight-tested a technology developed by Langley for NASA’s Environmentally Responsible Aviation (ERA) program: nonstick wing coatings to reduce the number of dead insects that pile up on leading edges, a major contributor to accumulated drag. So far, the best bug-proof coating developed by Langley has reduced the buildup of dead bugs by about 40 percent. NASA forecasts that debugging aircraft wings and improving laminar flow could improve fuel efficiency by 1 percent. That sounds trivial, until it’s converted to dollars; at today’s fuel prices, that’s more than $300 million in annual savings.

Impressive as these new technologies are, none by itself gets us to flight by anybody, anywhere, anytime. In the current hub-and-spoke paradigm, maximum efficiency is achieved by cramming as many passengers as possible onto huge planes that land on huge runways at huge airports. But the paradigm is changing, as visionaries plot out a future that maximizes the use of “thin-haul” routes, where there aren’t enough passengers to justify the use of a massive airliner.

Langley Research Center has developed a concept aircraft, the GL-10 Greased Lightning, that won’t need a runway at all. Designed to be a diesel-electric tilt-wing craft at full scale, it’s now a half-scale unmanned aerial vehicle (UAV) technology demonstrator powered by an electric battery. It can fly vertically and horizontally – in other words, it’s an unmanned craft that can take off and land from your back yard, without blowing off your roof shingles. The GL-10 was designed with a view toward the thinnest of hauls – packages or one passenger – for the era NASA’s visionaries see on the horizon: On-demand flight by anybody, anywhere, anytime.

Of course, while many unmanned vehicles fly today, none is pilotless – all UAVs are required to maintain a link with a pilot on the ground. The technology required to make something like the GL-10 into a truly autonomous craft, capable of transporting passengers on its own, is still in its early stages.

“My worst-case scenario,” said Ellis, “is wondering: If my grandma had to fly to my house for Thanksgiving dinner in a vehicle like that, are the systems on board to make sure she’s, one, going to get here safely, and two, not going to harm anybody on the way? What safety mechanisms need to be in place to make sure she can do that?”

Nobody has the complete answer to that question yet, but Langley researchers are building toward it – designing and testing, for example, detect-and-avoid algorithms that will help program an autonomous craft’s ability to sense and evade danger.

“If you look at the last hundred years,” said Finelli, “you’ll see Langley’s been at the forefront of envisioning the future of flight. And we think we’re well positioned to influence the next hundred years. We want to push the boundaries, bring in new technologies, and really transform air transportation for the general public.”