On August 9, 1896, a wealthy German engineer named Otto Lilienthal hiked up a hill in Rhinow, thirty miles from his home in Berlin. At the top, he crawled under an odd-looking apparatus, braced himself against a specially designed frame, and stood up wearing a set of wooden-framed fabric wings that measured thirty feet across. He paused at the crest of the incline, made certain of the direction of the wind, took a deep breath, and then began to run down.
To a casual observer, Lilienthal would have made a ridiculous sight: another hare-brained amateur convinced that man could achieve flight by pretending to be a bird. Surely, he would end his run with a face full of dirt, perhaps a broken bone or two.
But Otto Lilienthal was no amateur. He was, rather, the most sophisticated aerodynamicist of his day. For thirty years, he had taken tens of thousands of measurements of variously shaped surfaces moving at different angles through the air using a “whirling arm,” a long pole that extended horizontally from a fixed vertical pole and spun at a preset velocity, a device originally developed to test the flight of cannonballs. In 1889, Lilienthal had produced the most advanced study ever written on the mechanics of flight, Der Vogelflug als Grundlage der Fliegekunst—“Bird-flight as the Basis of Aviation.” As Wilbur Wright would later assert, “Of all the men who attacked the flying problem in the nineteenth century, Otto Lilienthal was easily the most important. His greatness appeared in every phase.”
In 1891, Lilienthal was finally ready to test his calculations. He fashioned a set of fixed glider wings to the specifications he had developed from his research, strapped them to his shoulders, waited for wind conditions to be right, ran downhill . . . and soared. For the next five years, Otto Lilienthal made more than two thousand flights using eighteen different gliders; fifteen were monofoil and three bifoil. He maneuvered in the air by shifting his weight, usually by kicking his feet and thus altering his center of gravity. He became so adept that at times he could almost float, to allow photographers to gain proper focus. Because dry plate negatives had been perfected in the 1880s, the resulting images were of excellent resolution and soon made their way across the ocean. Lilienthal became a world-renowned figure but he had little use for popular acclaim. Instead, he continued to publish scholarly papers and articles and in 1895 patented his invention.
But gliding was only an interim step; creating aerodynamic airfoils was only one aspect of what was commonly referred to as “the flying problem.” To achieve the ultimate—self-propelled, controlled, heavier-than-air flight—issues of thrust, force, stability, and weight ratios needed to be addressed. And certainly no sophisticated flying machine would be maneuvered by an aviator kicking his feet. Still, efficient airfoils would expedite resolution of those other issues, so Lilienthal continued to glide, kick, and measure. As sophisticated as anyone living on the vagaries of air currents, Lilienthal was aware that luck had played a role in his continued success. And luck, he knew as well, had a habit of running out.
On August 9, 1896, Otto Lilienthal’s did. During his second flight of the day, he stalled in a thermal about fifty feet off the ground, then fell, breaking his spine. The next day, Otto Lilienthal was dead. In his last hours, he uttered one of aviation’s most famous epitaphs: “Sacrifices must be made.”
Word of his accident spread across the globe, including to Dayton, Ohio, and the headquarters of the Wright Cycle Company, Wilbur and Orville Wright, proprietors. Wilbur had been following Lilienthal’s exploits with fascination, and word of his death, as later Wilbur put it, “aroused a passive interest which had existed since my childhood.” Lilienthal’s passing left a void in the struggle for manned flight and on that day Wilbur decided to fill it.
Wilbur was fortunate in his timing. In 1896, after centuries of stumbles, streams of research and data were about to coalesce to provide final focus for what was to be one of history’s most stunning achievements.
The heavens have been the home of the gods in virtually every recorded religion and not a single civilization from earliest antiquity fails to depict men and often women in flight. Sometimes these ancient aeronauts are in chariots, sometimes in other odd conveyances, and sometimes, like angels in Christianity even today, they fly by wings sprouting from their bodies. Achieving flight, therefore, might well be considered the oldest and most profound of all human aspirations.
Not surprisingly then, the science of flight has attracted the greatest minds in history—Aristotle, Archimedes, Leonardo, and Newton, to name just a few—but achieving the goal stumped all of them. Learning how to maintain a person or a craft in the air demanded more than a daunting scientific vision and meticulous mechanics; unlike many ground-based scientific enterprises, flight was almost impossible to test experimentally. Not that no one tried. In Roman times, slaves plunged to their deaths when ordered by men of science to leap from great heights with feathered wings strapped across their backs. Others throughout the centuries would fall to injury or death in a variety of quixotic contraptions.
To make the problem even more intractable, air, the medium of flight, is invisible, while for early theoreticians of flight, science was based almost entirely on sensory observation. Unlike modern scientists, they did not have the tools to deal with phenomena they could not see, hear, or touch. For inquiries into the mechanics of DNA replication or the detection of dark matter in the universe, for example, sophisticated instruments and powerful computers are routinely employed to test hypotheses. The ability to test with precision allows theory to precede observation. Einstein’s theory of relativity, first advanced in 1905, was not proven until a solar eclipse in 1919 provided the opportunity for astronomers to actually observe through a telescope light bending around a distant star.
Lacking such precision, a scientist can only extrapolate from observations in the natural world. Heavier-than-air flight was possible, of course—one need only watch a bird to appreciate that. So why couldn’t man fly as well? Yet as late as 1868, after more than two thousand years of study, the annual report of the Aeronautical Society of Great Britain lamented, “With respect to the abstruse question of mechanical flight, it may be stated that we are still ignorant of the rudimentary principles which should form the basis and rules for construction.”1
Achieving human flight, then, turned out to be a giant puzzle, solved over centuries, piece by tortuous piece.
Since air wasn’t even yet understood to be an actual substance, the first steps involved fluids. In 350 b.c., Aristotle hypothesized that an object moving through liquid will encounter resistance, and a century later Archimedes developed the first theory of fluid motion. From there, it would take more than seventeen centuries until Leonardo took up the problem and fluid dynamics began to be thought of as a rigorous discipline.
Leonardo’s great contribution was based in his observation that when the banks of a river narrowed to constrict its flow, the water in the narrower area speeded up so that the movement of the river remained “continuous.” Leonardo could not quantify this function but his observation was eventually generalized into a mathematical relationship between speed and distance and eventually between speed and pressure—the faster a fluid moves over a surface, the less pressure it produces. But as Leonardo was also fascinated with bird flight, he made some effort to apply the principle to gases. That ultimately would result in a device where air moved farther and faster over the top surface of an airfoil than under the bottom, thus creating uneven pressure, which resulted in “lift.” He also understood that as an object moved through a medium, it would encounter resistance, friction between the object and the medium, which would slow its progress, later to be quantified as “drag.”
It took another century for the next tentative step forward, this in 1600 by Galileo. The great Pisan astronomer was the first to quantify certain relationships in fluid dynamics and thus began to create a mechanical science from what had previously been only speculation. His most significant insight was that resistance will increase with the density of the medium, which would eventually lead to the understanding that as an airplane cruised at higher altitudes, fuel efficiencies would increase.
But with all the advances by science’s titans, which later would include Isaac Newton and Leonhard Euler, the applications continued to be solely in fluid dynamics—the resulting equations were then simply assumed to apply equally to gas as to liquid. In fact, using his equations, Newton hypothesized that powered flight was impossible because the weight of a motor needed to generate sufficient power would always exceed the amount of lift that could be supplied by airfoils that did not weigh more than the motor could support. For those who believed flight was possible, the assumption remained that humans must emulate birds—that is, develop a mechanism to allow for wings that flapped. Devices that attempted to mimic bird flight in this manner were dubbed “ornithopters.” A sketch of such an apparatus was found in one of Leonardo’s notebooks.
Aerodynamics as a separate science was born in 1799 when an English polymath named George Cayley produced a remarkable silver medallion. Cayley had observed that seagulls soared for great distances without flapping their wings and therefore hypothesized aircraft wings as fixed rather than movable. On the front side of his medallion, Cayley etched a monoplane glider with a cambered (curved) wing, a cruciform tail for stability, a single-seat gondola, and pedals, which he called “propellers,” to power the device in flight. On the obverse side of his medallion, Cayley placed a diagram of the four forces that figure in flight: lift, drag, gravity, and thrust. Although actual powered flight was a century away, Cayley’s construct was the breakthrough that set the process in motion. In 1853, four years before his death, a fixed-wing glider of Cayley’s design was the first to carry a human passenger.
Cayley’s hypotheses did not immediately take root. Not until the 1860s did his work finally spark a rush of interest. The Aeronautical Society of Great Britain was formed in 1866; another was begun in France three years later. Discussions of materials, airfoils, and resistance began to drift across borders and disciplines. Theorizing grew in sophistication and began to take in angle of incidence, the angle at which an airfoil moves through the oncoming air, now called “angle of attack”; and center of pressure, the point on a surface where the pressure is assumed to be concentrated, just as center of gravity is the point at which the entire mass of a body is assumed to be concentrated.
As the body of aerodynamic knowledge expanded, serious experimentation grew along with it. By the time Lilienthal strapped on his first set of wings, movement toward human flight seemed to be nearing the inexorable. But if the process was to move forward with any efficiency, experimenters would need some means to separate what seemed to work from what seemed not to—data and results would have to be shared. The man who most appreciated that need was someone who, while not producing a single design that resulted in flight, was arguably the most important person to participate in its gestation.
Octave Chanute was born in Paris on February 18, 1832. His father was a professor of history at the Royal College of France but in 1838 crossed the Atlantic to become vice president of Jefferson College in Louisiana. The elder Chanut—Octave later added the e to prevent mispronunciation—moved in 1844 to New York City, where Octave attended secondary school, and, as he put it, “became thoroughly Americanized.”2
Upon graduation, he decided to study engineering. As there were only four dedicated colleges of engineering in the United States, most aspirants learned on the job, as Chanute chose to do. In 1849, he asked for a job on the Hudson River Railroad at Sing Sing and, when told nothing was available, signed on without pay as a chainman. Two months later, he was put on the payroll at $1.12 per day and four years after that, completely self-taught, was named division engineer at Albany. But with immigrants pouring into Illinois to buy government lands at $1.25 per acre, Chanute instead went west. He gained high repute on a number of railroad assignments and eventually submitted a design for the Chicago stockyards that was chosen over dozens of others. With the successful completion of that project, Chanute was asked to attempt a traverse of the “unbridgeable” Missouri River. Chanute’s Hannibal Bridge at Kansas City not only successfully spanned the waterway but elevated the city into a center of commerce, and its designer to national acclaim.
For the next two decades, Chanute continued to push forward transportation engineering. He also perfected a means of pressure-treating wood with creosote that remained state-of-the-art for more than a century. When he retired in 1889, he did so as the foremost civil engineer in the United States and a very wealthy man. For all his personal achievements, however, Chanute never wavered in his commitment to a cooperative approach to problem solving. He attained leadership positions in a number of professional organizations and became active in civic groups in the cities in which he lived. As a result, which might be considered surprising for one so successful, Chanute had no real enemies and was well liked by virtually everyone who came in contact with him.
By 1890, he relocated to Chicago, but he wouldn’t pass his remaining days sitting back with his feet up, and gazing out over Lake Michigan. His retirement had been prompted not by a desire to stop working but rather by the intention to pursue a passion that had been percolating for fifteen years. Chanute intended to bring the same skills and approach that had served him so well in his own career to the quest to achieve human flight.
It was not his intent initially to design aircraft but rather to serve as a catalyst, a focal point for the growing streams of theory and data then being generated about “the flying problem.” The engineering methodology, he was convinced, the rigorous, thoughtful, step-by-step approach that created a bridge from the idea of a bridge, could be equally applied to heavier-than-air flight. Ideas therefore must be evaluated by peers and, if they showed promise, tested and incorporated in a body of knowledge available to all. Innovation should be rewarded, certainly, and inventions patented, but the process would be best served openly and collegially. Achieving flight for the advancement of humanity must always retain predominance over achieving the goal merely for profit.