One Hundred Years After the...

Wright Brothers' Conquest
of the Air

A Celebration of Human Achievement

    Barely 3-1/2 years after Wilbur Wright penned those words to Octave Chanute, the Wright Brothers' 1903 "Flyer" lifted from the sands at Kitty Hawk North Carolina to make the world's first powered flight. With Orville at the controls, the plane flew 120 feet (37 meters) in 12 seconds. The Brothers made three more flights that day. The longest, by Wilbur, was 852 feet (260 meters) in 59 seconds.
       When the Wright Brothers arrived at Kitty Hawk in 1903 for their historic attempt, they were almost certain of success. They had all but conquered the air the previous year with over 1,000 successful gliding flights in their 1902 glider, "all under perfect control of the operator," wrote Wilbur. But only one year prior to their 1902 success, after disappointing glider experiments in 1900 and 1901, the Brothers had nearly given up in defeat. They had based their wing designs on the work of predecessors, pioneers who were widely respected within the scientific community, only to discover that all of it was hopelessly in error. On returning from Kitty Hawk after unsuccessful gliding experiments in 1901, Wilbur's despair was evident when he declared: "Not within a thousand years will man ever fly." But in one last effort, the Wrights turned to wind tunnel tests and finally uncovered the secrets of heavier-than-air flight. An elated Orville wrote to a friend: "Isn't it astonishing that all of these secrets have been preserved for so many years just so we could discover them!" The 1902 glider would prove out their new discoveries, and the 1903 machine, essentially a larger powered version of their 1902 glider, would take to the air in triumph.
       Today, Orville and Wilbur Wright are widely acknowledged for their enormous technical achievement in developing the world's first successful airplane. The Wright Brothers not only developed the first accurate theories on the design of wings and propellers, they also designed and built their own engine, and they invented the three-axis control system, which is still used on airplanes today.
       The personal dimension of the Wright Brothers' conquest is equally as impressive as their technical achievement. Neither Orville nor Wilbur had graduated from High School. They had no formal training in the scientific theories and methodologies considered essential to designing a successful flying machine, so their chance of success was remote. As a result, they received no financial support. Their experiments had to be supported entirely with their own money. In contrast, Samuel Pierpont Langley, Director of the Smithsonian Institute at the time, received a $50,000 grant from the U.S. Government to build a flying machine, which ultimately failed to fly. So it was entirely unreasonable for the Wright Brothers to believe they could succeed where highly trained engineers and scientists with large financial resources had failed. Not only did they conquer the air, they also conquered a world of skeptics and their own personal self-doubts. They accomplished what they should not have been able to accomplish.
         On the 100-year anniversary of the Wright Brothers' conquest of the air, I offer this personal tribute to their achievement, and acknowledge the same spirit of adventure and achievement that lies within each of us.  

Robert Q. Riley  

The Grand Adventure

       Since the beginning of history, humans have dreamed of the ability to soar on wings with the freedom of birds. But folklore is replete with admonishments against dreaming too large. Icarus of Greek mythology fashioned wings of wax and feathers, then flew too close to the sun. The wax melted and the feathers came loose, and Icarus plunged to his death in the sea. He had dared to go beyond his place in life and was properly smitten for his audacity.
      The Wrights were aware of the very real hazards of venturing into the unknown domain of the air. Speaking at a meeting of the Western Society of Engineers in Chicago in 1901, Wilbur alluded to the risk with a statement that seems to apply equally to life itself: "If you are looking for perfect safety, you will do well to sit on a fence and watch the birds; but if you really wish to learn, you must mount a machine and become acquainted with its tricks by actual trial."
      The Wright Brothers were unwilling to sit on a fence and watch the birds. They had chosen a grand adventure over the safety of the fence.

Genesis of a New World
       The Wright Brothers interest in flying began when, as young boys, their father brought home a toy Penaud helicopter. The toy sparked a fascination with flight that would ultimately change the world. Their pursuit of flying did not begin in earnest, however, until 1899 when Wilbur Wright wrote to the Smithsonian Institute requesting "…all that is already known" about flying. Based on what they learned from prior work, the Wright Brothers concluded that the correct way to design wings was already known, and only a system of controlling a machine in the air was still missing. Previous experimenters had been so focused on simply getting off the ground that they had largely ignored the problem of how to control a machine once it was in the air. This shortfall led to Otto Lilienthal's fate, a German glider pilot who plunged out of control to his death in 1896. A gust had upset the glider, and simply shifting his body weight, as was the practice with early gliders, was not enough to bring the machine back to level flight. A system of control, the Wrights believed, would be their contribution to mankind's quest for the air.
       The Wright Brothers invented a method of twisting the wings so one wing angled upward and the opposite wing angled downward. This, they reasoned, would enable them to level out the wings after being rolled to one side by a gust of wind. They built a small kite to test the system and found they could perfectly control the kite by pulling wires that were rigged to actuate the "wing warping" mechanism. Their next step was to test it on a full-size glider capable of carrying a pilot.

First Steps - 1900 Glider Experiments
      In 1900, the Wrights built the first in a series of full-size gliders to test their wing warping theories. They used Otto Lilienthal's tables of lift to determine the curvature of the wings. Previous experimenters had discovered that an airplane wing must be curved on top in order to produce lift. And Lilienthal's tables of lift were considered the most accurate guide in defining precisely what shape a wing should have and the amount of lift it would produce. The Brothers followed Lilienthal's tables almost to the letter, making only a slight change so they could get more lift at lower speeds.
       They planned to test the glider as a kite, and then to spend many hours gliding on the winds at Kitty Hawk while tethered to a post. This, they reasoned, would give them the gliding time necessary to learn the tricks of the air. In a letter to Octave Chanute, Wilbur offered his thoughts about the importance of skill to human flight: It is possible to fly without motors, but not without knowledge and skill. This I conceive to be fortunate, for man, by reason of his greater intellect, can more reasonably hope to equal birds in knowledge, than to equal nature in the perfection of her machinery.
      Unfortunately, the Wright Brothers would not gain the skill they had envisioned. The glider performed well as a kite, and their wing warping system worked. But the glider's lifting power fell far short of predictions made by Lilienthal's tables. The glider could lift a pilot only in very strong winds, which made it difficult to control and dangerous to fly. So the Wright Brothers returned to Dayton determined to build an improved glider and go back to Kitty Hawk the following year.

Failed Improvements - 1901 Glider Experiments
      Suspecting the change they made to Lilienthal's wing curvature may have contributed to the shortfall of lift in 1900, the Brothers precisely followed his curvature on the 1901 machine. For greater lift, they increased the size of the wings. The Wright Brothers returned to Kitty Hawk in 1901 with their new machine expecting to gain the flying experience they had missed the year before. Instead of performing better, however, the new glider performed worse than the 1900 glider. Lift was only slightly improved, and the machine was almost impossible to control in the air.
       To help with pitch instability, the Brothers made changes that forced the wings into a curvature more like the one they used in 1900. This restored the machine's "fore-to-aft balance," but roll control remained difficult and unpredictable. For no apparent reason, warping the wings to lift a low wing would sometimes work perfectly, and at other times it would cause the low wing to actually drop farther, which resulted in the glider spiraling into the ground. Unknowingly, the Wrights were experiencing the world's first airplane "spins," and did not know what to make of it. Notice the absence of a vertical stabilizer (rudder) on both the 1900 and 1901 gliders. Without a vertical stabilizer, even a modern aircraft can spin out of control during a turn.
      After several weeks, the Wrights closed up their campsite and headed back to Dayton in discouragement. They now realized that previous work on aerodynamics was totally wrong, and all of it had to be discarded. Anyone hoping for success would have to start from scratch. And with limited funds and a bicycle business that was already suffering from their long absences while flying at Kitty Hawk, the Brothers doubted it would be them.

Wind Tunnel Discoveries - A Roadmap to Success
      After returning to Dayton, Wilbur made several discouraging statements about the prospects of human flight, including a declaration that all previous experimenters had been wrong in their theories on flight. Wilbur's criticism of previous work prompted an invitation to come to Chicago and present his findings to a group of scientists and engineers, which Wilbur reluctantly accepted. After accepting the invitation, however, the Brothers began to consider the scientific validations that would be necessary if they were to be taken seriously by a professional audience, especially since neither Orville nor Wilbur had much of a formal education. So mainly to avoid embarrassment, the Wright Brothers set out on a series of wind tunnel tests designed to document their theories. These tests, however, did more than just provide documentation. They uncovered the secrets of flight!
       Wind tunnel testing began in the fall of 1901 and was concluded early in 1902. In the end, the Brothers had accumulated more information on the design and behavior of wings than anyone else in history. They now knew how to correctly design wings, how to predict an airplane's lifting power, how to calculate the air drag of various shapes, and how to determine the size of the engine needed to make an airplane fly under its own power. The Wright Brothers had all the information necessary to design a successful flying machine.

Success at Last - The 1902 Glider
      When the Wright Brothers returned to Kitty Hawk in 1902 they brought parts and drawings for a completely redesigned glider based on their wind tunnel discoveries. They now understood the effect of "aspect ratio" on a wing's lifting power. Aspect ratio is the relationship between a wing's cord (front-to-rear dimension) and its span (tip-to-tip dimension). Long slender wings have more lift than short stubby ones.
      The vertical stabilizer is another new feature of the 1902 machine. Its purpose is to prevent the "adverse yaw" caused by warping the wings. Every aircraft naturally yaws to the outside of a turn because of the difference in drag between the two wings during a banking turn. This difference in drag rotates the aircraft around its vertical axis toward the wing having greater drag (the high wing). It's call "adverse yaw" because to turn properly the aircraft should yaw into the turn, not to the outside of it. So the correct yaw has to be provided by pivoting the vertical stabilizer into the turn, somewhat like the rudder on a boat.
      Initially, the 1902 glider was equipped with two side-by-side vertical stabilizers that were mounted in a fixed position. But the Brothers still experienced a control problem, which they referred to as "sidling off into the ground." They finally hit on the idea of making the vertical stabilizer movable (like those on modern aircraft). So the Brothers switched to a single rudder and connected it by wires to the wing warping mechanism so it would turn in unison with the wings. This final modification resulted in fully coordinated turns, and produced the world's first fully controllable flying machine. The Wright Brothers had invented the three-axis control system, which is used by every aircraft flying today.
      The Brothers made more than 1,000 gliding flights from the sandy hills near Kitty Hawk, "all under perfect control of the operator," wrote Wilbur.  Orville wrote to his sister Kathrine on leaving Kitty Hawk in 1902: "We now hold all the records! Largest machine, longest distance glide, longest time in the air, smallest angle of descent, and in the highest wind."

Triumph - The 1903 Flyer
        
      When the Wright Brothers arrived at Kitty Hawk in 1903 with parts for their powered "Flyer", they were almost certain of success.    The new machine was based on their highly successful 1902 glider, and power requirements had been determined by equations derived from their wind tunnel tests.   So the Brothers were confident they would succeed.
         The 1903 Flyer was a large 605-pound (274kg) machine with a wingspan of 40.3 feet (12.28 meters).  Except for the 7,000-pound (3175 kg) steam-powered monster built by Hiram Maxim (inventor of the machine gun) in England in 1894, it was the largest machine anyone had ever attempted to fly.   But the task of designing a powered flying machine turned out to be far more challenging than the Brothers had envisioned at the end of their 1902 gliding experiments. 
         The Wright Brothers believed that once the problem of control was solved, all that remained would be to add an engine and propellers, and take to the air.   Gasoline engines were already being manufactured, and propellers were widely used on powered water craft.  So, the Wrights believed, they would simply order an appropriate engine, and build propellers according to the principles used to design boat propellers.   Both of these presumptions would soon evaporate.
         The Brothers wrote to several engine manufacturers with a request for an engine weighing no more than 180 pounds and capable of producing at least 8 horsepower.   No one was interested in providing such an engine, so the Wright Brothers had to design and build their own.  The four-cylinder Wright engine, built in their Dayton bicycle shop by chief mechanic, Charles Taylor, weighed slightly less than 200 pounds and developed 12 horsepower, or about twice the power of today's lawn mower engines.
         The next task was to design the propellers, and for this they turned to technical literature on boat propellers.  Since air screws (propellers) and water screws both operate in a fluid environment, they reasoned that theories on water screws would point the way to a design for efficient air screws.  To the Brothers dismay, however, they discovered that boat propellers were designed entirely by trial and error, and no one knew how or why they worked.   No theory existed on how to design propellers, so the Brothers had to develop their own.  
         The Wrights approached the challenge by first assuming that propeller blades were, in effect, like the wings of an aircraft. Therefore, the theories they had developed for the behavior of wings could also be applied to the blades of a propeller.  But it wasn't quite that simple.  Wrote Orville: "With the machine moving forward, the air flying backward, the propeller turning sideways, and nothing standing still, it seemed impossible to find a starting point from which to trace the various simultaneous reactions. Contemplation of it was confusing. After long arguments, we found ourselves in the ludicrous position of having been converted to the other's side, with no more agreement than when the discussion began."  
         In the end, their discussions forced the truth out into the open, leaving the Brothers with the world's first valid theory on the design of air screws.    Propellers based on the Wright theory resulted in the first efficient propellers ever made - only about 5 percent less efficient than modern propellers.  Without these highly efficient propellers, the 1903 Flyer would have remained hopelessly earthbound.
         Triumph on the sands at Kitty Hawk in December 1903 came after three years of technical inquiry and methodical experimentation.   In just three short years, these two untrained inventors had gained more knowledge on the principles of flight than had been accumulated in all of human history.   A pursuit that began with the idea of contributing only a control system for flying machines ended up producing the first accurate theories on the entire range of aerodynamic interactions necessary for flight.   A shortfall in any one of these areas would have proven fatal to their attempts.
         Each taking their turn, the Brothers made four flights on the morning of December 17, 1903.   The longest was by Wilbur for a distance of 852 feet (260 meters) in 59 seconds.   This world-changing event was announced in a simple telegram sent from Kitty Hawk by Orville to his father on December 17, 1903.

         Sometime in the 1940s, Wright biographer, Fred C. Kelly, asked Orville: "What was the most exciting part of inventing the flying machine? Was it when the machine took to the air for that first flight?" Orville thought for a moment and then replied: "The most exciting part of inventing the flying machine was lying awake in bed at night dreaming of how exciting it would be to fly."  
           Barely 66 years after the Wright Brothers' first steps into air, Neil Armstrong and Buz Aldrin stepped onto the surface of the moon to complete another chapter in the grand adventure.  Today, only 100 years after the Flyer, spacefight is becoming routine and unmanned vehicles are probing deep into the universe, preparing the way for manned fights to distant worlds.