The brothers' breakthrough invention was their creation of a three-axis control system, which enabled the pilot to steer the aircraft effectively and to maintain its equilibrium. Their system of aircraft controls made fixed-wing powered flight possible and remains standard on airplanes of all kinds. Their first U.S. patent, written in March 1903, before their first flight at Kitty Hawk, did not claim invention of a flying machine, but rather a system of aerodynamic control that manipulated a flying machine's surfaces.
From the beginning of their aeronautical work, Wilbur and Orville focused on developing a reliable method of pilot control as the key to solving "the flying problem". This approach differed significantly from other experimenters of the time who put more emphasis on developing powerful engines. Using a small home-built wind tunnel, the Wrights also collected more accurate data than any before, enabling them to design more efficient wings and propellers.
The brothers gained the mechanical skills essential to their success by working for years in their Dayton, Ohio-based shop with printing presses, bicycles, motors, and other machinery. Their work with bicycles, in particular, influenced their belief that an unstable vehicle such as a flying machine could be controlled and balanced with practice.
This was a trend, as many other aviation pioneers were also dedicated cyclists and involved in the bicycle business in various ways. From 1900 until their first powered flights in late 1903, the brothers conducted extensive glider tests that also developed their skills as pilots. Their shop mechanic Charles Taylor became an important part of the team, building their first airplane engine in close collaboration with the brothers.
The Wright brothers' status as inventors of the airplane has been subject to numerous counter-claims. Much controversy persists over the many competing claims of early aviators. Edward Roach, historian for the Dayton Aviation Heritage National Historical Park, argues that the Wrights were excellent self-taught engineers who could run a small company well, but did not have the business skills or temperament necessary to dominate the rapidly growing aviation industry at the time.
Childhood
Wilbur and Orville Wright were two of seven children born to Milton Wright, a clergyman, and Susan Catherine Koerner. Milton Wright's mother, Catherine Reeder, was descended from the progenitor of the Vanderbilt family – one of America's richest families – and the Huguenot Gano family of New Rochelle, New York.
Wilbur was born near Millville, Indiana, in 1867; Orville in Dayton, Ohio, in 1871. The brothers never married. The other Wright siblings were Reuchlin, Lorin, Katharine, and twins Otis and Ida (died in infancy).
None of the Wright children had middle names. Instead, their father tried hard to give them distinctive first names. Wilbur was named for Willbur Fisk and Orville for Orville Dewey, both clergymen that Milton Wright admired. They were "Will" and "Orv" to their friends and in Dayton, and their neighbors knew them simply as "the bishop's kids", or "the bishop's boys".
Because of their father's position as a bishop in the Church of the United Brethren in Christ, he traveled often and the Wrights frequently moved – twelve times before finally returning permanently to Dayton in 1884. In elementary school, Orville was given to mischief and was once expelled. In 1878, when the family lived in Cedar Rapids, Iowa, their father brought home a toy helicopter for his two younger sons.
The device was based on an invention of French aeronautical pioneer Alphonse Pénaud. Made of paper, bamboo and cork with a rubber band to twirl its rotor, it was about 1 ft (30 cm) long. Wilbur and Orville played with it until it broke, and then built their own. In later years, they pointed to their experience with the toy as the spark of their interest in flying.
Early career and research
Both brothers attended high school, but did not receive diplomas. The family's abrupt move in 1884 from Richmond, Indiana, to Dayton, Ohio, where the family had lived during the 1870s, prevented Wilbur from receiving his diploma after finishing four years of high school. The diploma was awarded posthumously to Wilbur on April 16, 1994, which would have been his 127th birthday.
In late 1885 or early 1886, while playing an ice-skating game with friends Wilbur was struck in the face with a hockey stick by Oliver Crook Haugh, who later became a serial killer. Wilbur lost his front teeth. He had been vigorous and athletic until then, and although his injuries did not appear especially severe, he became withdrawn.
He had planned to attend Yale. Instead, he spent the next few years largely housebound. During this time he cared for his mother, who was terminally ill with tuberculosis, read extensively in his father's library and ably assisted his father during times of controversy within the Brethren Church, but also expressed unease over his own lack of ambition.
Orville dropped out of high school after his junior year to start a printing business in 1889, having designed and built his own printing press with Wilbur's help. Wilbur joined the print shop, and in March the brothers launched a weekly newspaper, the West Side News. Subsequent issues listed Orville as publisher and Wilbur as editor on the masthead.
In April 1890 they converted the paper to a daily, The Evening Item, but it lasted only four months. They then focused on commercial printing. One of their clients was Orville's friend and classmate, Paul Laurence Dunbar, who rose to international acclaim as a ground-breaking African-American poet and writer. For a brief period the Wrights printed the Dayton Tattler, a weekly newspaper that Dunbar edited.
Capitalizing on the national bicycle craze (spurred by the invention of the safety bicycle and its substantial advantages over the penny-farthing design), in December 1892 the brothers opened a repair and sales shop (the Wright Cycle Exchange, later the Wright Cycle Company) and in 1896 began manufacturing their own brand.
They used this endeavor to fund their growing interest in flight. In the early or mid-1890s they saw newspaper or magazine articles and probably photographs of the dramatic glides by Otto Lilienthal in Germany.
1896 brought three important aeronautical events. In May, Smithsonian Institution Secretary Samuel Langley successfully flew an unmanned steam-powered fixed-wing model aircraft. In mid-year, Chicago engineer and aviation authority Octave Chanute brought together several men who tested various types of gliders over the sand dunes along the shore of Lake Michigan.
In August, Lilienthal was killed in the plunge of his glider. These events lodged in the minds of the brothers, especially Lilienthal's death. The Wright brothers later cited his death as the point when their serious interest in flight research began.
Wilbur said, "Lilienthal was without question the greatest of the precursors, and the world owes to him a great debt." In May 1899 Wilbur wrote a letter to the Smithsonian Institution requesting information and publications about aeronautics. Drawing on the work of Sir George Cayley, Chanute, Lilienthal, Leonardo da Vinci, and Langley, they began their mechanical aeronautical experimentation that year.
The Wright brothers always presented a unified image to the public, sharing equally in the credit for their invention. Biographers note that Wilbur took the initiative in 1899 and 1900, writing of "my" machine and "my" plans before Orville became deeply involved when the first person singular became the plural "we" and "our".
Author James Tobin asserts, "it is impossible to imagine Orville, bright as he was, supplying the driving force that started their work and kept it going from the back room of a store in Ohio to conferences with capitalists, presidents, and kings. Will did that. He was the leader, from the beginning to the end."
Ideas about control
Despite Lilienthal's fate, the brothers favored his strategy: to practice gliding in order to master the art of control before attempting motor-driven flight. The death of British aeronaut Percy Pilcher in another hang gliding crash in October 1899 only reinforced their opinion that a reliable method of pilot control was the key to successful – and safe – flight.
At the outset of their experiments they regarded control as the unsolved third part of "the flying problem". The other two parts – wings and engines – they believed were already sufficiently promising.
The Wright brothers' plan thus differed sharply from more experienced practitioners of the day, notably Ader, Maxim, and Langley, who all built powerful engines, attached them to airframes equipped with untested control devices, and expected to take to the air with no previous flying experience. Although agreeing with Lilienthal's idea of practice, the Wrights saw that his method of balance and control by shifting his body weight was inadequate. They were determined to find something better.
On the basis of observation, Wilbur concluded that birds changed the angle of the ends of their wings to make their bodies roll right or left. The brothers decided this would also be a good way for a flying machine to turn – to "bank" or "lean" into the turn just like a bird – and just like a person riding a bicycle, an experience with which they were thoroughly familiar.
What is equally important, they hoped this method would enable recovery when the wind tilted the machine to one side (lateral balance). They puzzled over how to achieve the same effect with man-made wings and eventually discovered wing-warping when Wilbur idly twisted a long inner-tube box at the bicycle shop.
Other aeronautical investigators regarded flight as if it were not so different from surface locomotion, except the surface would be elevated. They thought in terms of a ship's rudder for steering, while the flying machine remained essentially level in the air, as did a train or an automobile or a ship at the surface.
The idea of deliberately leaning, or rolling, to one side either seemed undesirable or did not enter their thinking. Some of these other investigators, including Langley and Chanute, sought the elusive ideal of "inherent stability", believing the pilot of a flying machine would not be able to react quickly enough to wind disturbances to use mechanical controls effectively.
The Wright brothers, in contrast, wanted the pilot to have absolute control. For that reason, their early designs made no concessions toward built-in stability (such as dihedral wings). They deliberately designed their 1903 first powered flyer with anhedral (drooping) wings, which are inherently unstable, but less susceptible to upset by gusty cross winds.
Flights
Toward flight
On July 27, 1899, the brothers put wing warping to the test by building and flying a biplane kite with a 5-foot (1.5 m) wingspan, and a curved wing with a 1-foot (0.30 m) chord. When the wings were warped, or twisted, the trailing edge that was warped down produced more lift than the opposite wing, causing a rolling motion.
The warping was controlled by four lines between kite and crossed sticks held by the kite flyer. In return, the kite was under lateral control.
In 1900 the brothers went to Kitty Hawk, North Carolina, to begin their manned gliding experiments. In his reply to Wilbur's first letter, Octave Chanute had suggested the mid-Atlantic coast for its regular breezes and soft sandy landing surface. Wilbur also requested and examined U.S. Weather Bureau data, and decided on Kitty Hawk after receiving information from the government meteorologist stationed there.
Kitty Hawk, although remote, was closer to Dayton than other places Chanute had suggested, including California and Florida. The spot also gave them privacy from reporters, who had turned the 1896 Chanute experiments at Lake Michigan into something of a circus. Chanute visited them in camp each season from 1901 to 1903 and saw gliding experiments, but not the powered flights.
Gliders
The Wrights based the design of their kite and full-size gliders on work done in the 1890s by other aviation pioneers. They adopted the basic design of the Chanute-Herring biplane hang glider ("double-decker" as the Wrights called it), which flew well in the 1896 experiments near Chicago, and used aeronautical data on lift that Otto Lilienthal had published. The Wrights designed the wings with camber, a curvature of the top surface.
The brothers did not discover this principle, but took advantage of it. The better lift of a cambered surface compared to a flat one was first discussed scientifically by Sir George Cayley. Lilienthal, whose work the Wrights carefully studied, used cambered wings in his gliders, proving in flight the advantage over flat surfaces.
The wooden uprights between the wings of the Wright glider were braced by wires in their own version of Chanute's modified Pratt truss, a bridge-building design he used for his biplane glider (initially built as a triplane). The Wrights mounted the horizontal elevator in front of the wings rather than behind, apparently believing this feature would help to avoid, or protect them from, a nosedive and crash like the one that killed Lilienthal. Wilbur incorrectly believed a tail was not necessary, and their first two gliders did not have one.
According to some Wright biographers, Wilbur probably did all the gliding until 1902, perhaps to exercise his authority as older brother and to protect Orville from harm as he did not want to have to explain to their father, Bishop Wright, if Orville got injured.
1900
The brothers flew the glider for only a few days in early autumn 1900 at Kitty Hawk. In the first tests, probably on October 3, Wilbur was aboard while the glider flew as a kite not far above the ground with men below holding tether ropes. Most of the kite tests were unpiloted, with sandbags or chains and even a local boy as ballast.
They tested wing-warping using control ropes from the ground. The glider was also tested unmanned while suspended from a small homemade tower. Wilbur, but not Orville, made about a dozen free glides on only a single day, October 20. For those tests the brothers trekked four miles (6 km) south to the Kill Devil Hills, a group of sand dunes up to 100 feet (30 m) high (where they made camp in each of the next three years).
Although the glider's lift was less than expected, the brothers were encouraged because the craft's front elevator worked well and they had no accidents. However, the small number of free glides meant they were not able to give wing-warping a true test.
The pilot lay flat on the lower wing, as planned, to reduce aerodynamic drag. As a glide ended, the pilot was supposed to lower himself to a vertical position through an opening in the wing and land on his feet with his arms wrapped over the framework. Within a few glides, however, they discovered the pilot could remain prone on the wing, headfirst, without undue danger when landing. They made all their flights in that position for the next five years.
1901
Before returning to Kitty Hawk in the summer of 1901, Wilbur published two articles, "The Angle of Incidence" in The Aeronautical Journal, and "The Horizontal Position During Gliding Flight" in Illustrierte Aeronautische Mitteilungen. The brothers brought all of the material they thought was needed to be self-sufficient at Kitty Hawk.
Besides living in tents once again, they built a combination workshop and hangar. Measuring 25 feet (7.6 m) long by 16 feet (4.9 m) wide, the ends opened upward for easy glider access.
Hoping to improve lift, they built the 1901 glider with a much larger wing area and made dozens of flights in July and August for distances of 50 to 400 ft (15 to 122 m). The glider stalled a few times, but the parachute effect of the forward elevator allowed Wilbur to make a safe flat landing, instead of a nose-dive.
These incidents wedded the Wrights even more strongly to the canard design, which they did not give up until 1910. The glider, however, delivered two major disappointments. It produced only about one-third the lift calculated and sometimes pointed opposite the intended direction of a turn – a problem later known as adverse yaw – when Wilbur used the wing-warping control. On the trip home a deeply dejected Wilbur remarked to Orville that man would not fly in a thousand years.
The poor lift of the gliders led the Wrights to question the accuracy of Lilienthal's data, as well as the "Smeaton coefficient" of air pressure, a value which had been in use for over 100 years and was part of the accepted equation for lift.
The Wrights used the following lift equation to calculate the amount of lift that a wing would produce: where:
- is the lift, in pounds;
- is the coefficient of air pressure (the Smeaton coefficient);
- is the total area of lifting surface, in square feet;
- is the air velocity over the wing (headwind plus ground speed), in miles per hour; and
- is the coefficient of lift (varies with wing shape).
Over the years a wide variety of values had been measured for the Smeaton coefficient ; Chanute identified up to 50 of them.
Wilbur knew that Langley, for example, had used a lower number than the traditional one. Intent on confirming the correct Smeaton value, Wilbur performed his own calculations using measurements collected during kite and free flights of the 1901 glider. His results correctly showed that the coefficient was very close to 0.0033 (similar to the number Langley used), not the traditional 0.0054, which would significantly exaggerate predicted lift.
The brothers decided to find out if Lilienthal's data for lift coefficients were correct. They devised an experimental apparatus which consisted of a freely rotating bicycle wheel mounted horizontally in front of the handlebars of a bicycle. The brothers took turns pedaling the bicycle vigorously, creating air flow over the horizontal wheel.
Attached vertically to the wheel were an airfoil and a flat plate mounted 90° away. As air passed by the airfoil, the lift it generated, if unopposed, would cause the wheel to rotate.
The flat plate was oriented so its drag would push the wheel in the opposite direction of the airfoil. The airfoil and flat plate were made in specific sizes such that, according to Lilienthal's measurements, the lift generated by the airfoil would exactly counterbalance the drag generated by the flat plate and the wheel would not turn.
However, when the brothers tested the device, the wheel did turn. The experiment confirmed their suspicion that either the standard Smeaton coefficient or Lilienthal's coefficients of lift and drag – or all of them – were in error.
They then built a 6-foot (1.8 m) wind tunnel in their shop, and between October and December 1901 conducted systematic tests on dozens of miniature wings. The "balances" they devised and mounted inside the tunnel to hold the wings looked crude, made of bicycle spokes and scrap metal, but were "as critical to the ultimate success of the Wright brothers as were the gliders." The devices allowed the brothers to balance lift against drag and accurately calculate the performance of each wing.
They could also see which wings worked well as they looked through the viewing window in the top of the tunnel. The tests yielded a trove of valuable data never before known and showed that the poor lift of the 1900 and 1901 gliders was entirely due to an incorrect Smeaton value, and that Lilienthal's published data were fairly accurate for the tests he had done.
Before the detailed wind tunnel tests, Wilbur traveled to Chicago at Chanute's invitation to give a lecture to the Western Society of Engineers on September 18, 1901. He presented a thorough report about the 1900–1901 glider experiments and complemented his talk with a lantern slide show of photographs. Wilbur's speech was the first public account of the brothers' experiments.
A report was published in the Journal of the society, which was then separately published as an offprint titled Some Aeronautical Experiments in a 300 copy printing.
1902
Lilienthal had made "whirling arm" tests on only a few wing shapes, and the Wrights mistakenly assumed the data would apply to their wings, which had a different shape. The Wrights took a huge step forward and made basic wind tunnel tests on 200 scale-model wings of many shapes and airfoil curves, followed by detailed tests on 38 of them.
An important discovery was the benefit of longer narrower wings: in aeronautical terms, wings with a larger aspect ratio (wingspan divided by chord – the wing's front-to-back dimension). Such shapes offered much better lift-to-drag ratio than the stubbier wings the brothers had tried so far. With this knowledge, and a more accurate Smeaton number, the Wrights designed their 1902 glider.
The wind tunnel tests, made from October to December 1901, were described by biographer Fred Howard as "the most crucial and fruitful aeronautical experiments ever conducted in so short a time with so few materials and at so little expense". In their September 1908 Century Magazine article, the Wrights explained, "The calculations on which all flying machines had been based were unreliable, and ... every experiment was simply groping in the dark ... We cast it all aside and decided to rely entirely upon our own investigations."
The 1902 glider wing had a flatter airfoil, with the camber reduced to a ratio of 1-in-24, in contrast to the previous thicker wing. The larger aspect ratio was achieved by increasing the wingspan and shortening the chord. The glider also had a new structural feature: A fixed, rear vertical rudder, which the brothers hoped would eliminate turning problems.
However, the 1902 glider encountered trouble in crosswinds and steep banked turns, when it sometimes spiraled into the ground – a phenomenon the brothers called "well digging". According to Combs, "They knew that when the earlier 1901 glider banked, it would begin to slide sideways through the air, and if the side motion was left uncorrected, or took place too quickly, the glider would go into an uncontrolled pivoting motion.
Now, with vertical fins added to correct this, the glider again went into a pivoting motion, but in the opposite direction, with the nose swinging downward."
Orville apparently visualized that the fixed rudder resisted the effect of corrective wing-warping when attempting to level off from a turn. He wrote in his diary that on the night of October 2, "I studied out a new vertical rudder". The brothers then decided to make the rear rudder movable to solve the problem. They hinged the rudder and connected it to the pilot's warping "cradle", so a single movement by the pilot simultaneously controlled wing-warping and rudder deflection.
The apparatus made the trailing edge of the rudder turn away from whichever end of the wings had more drag (and lift) due to warping. The opposing pressure produced by turning the rudder enabled corrective wing-warping to reliably restore level flight after a turn or a wind disturbance. Furthermore, when the glider banked into a turn, rudder pressure overcame the effect of differential drag and pointed the nose of the aircraft in the direction of the turn, eliminating adverse yaw.
