Wright Brothers – Invention Of The Airplane

A few days after the first successful powered, sustained, controlled flight of the Wright Flyer at Kitty Hawk in 1903, it was disassembled and returned to Dayton, Ohio. Orville and Wilbur were pleased with its performance but knew that there was much work yet to be done to produce a practical flying machine. One of their important tasks would be to improve the stability of the machine.

1904 Machine, Wright Flyer II

The dimensions of the 1904 machine were similar to the 1903 machine but a large number of design changes were made. These included a new engine, changing the structure to move the center of gravity towards the rear, decreasing the camber of the wings, changing the shape of the vertical rudder and using new and larger propellers.

Due to the difficulty of taking off in the low winds in Dayton, they started using a derrick with weights that could be dropped to catapult the machine.

The performance of the machine was an improvement over the 1903 Flyer, but it was still not the performance the Wrights were seeking. It had a tendency to stall in tight turns. This problem was not solved until 1905.

1905 Machine, Wright Flyer III

Changes made to the 1905 machine included enlarging the rudder surfaces, moving the vertical tail further to the rear, using newly designed propellers (bent end), decreasing the camber back to the camber used on the 1903 Flyer and eliminating the wing droop. They also took the important step of unlinking the warp and rudder controls and providing for the separate, or combined, operation in any desired degree.

On October 5th Wilbur took-off from Huffman Prairie and flew for more than 24 miles in just over 39 minutes while completing more than 29 circles of the field at an average speed of 38-mph.

The Wrights were satisfied that they had produced a practical airplane. Others, including the U.S. War Department and foreign governments, were not convinced. Fearing loss of their secrets, they decided not to fly again until they had buyer. The result was that they did not fly in 1906 or 1907.

It was not until February 8, 1908, that the Signal Corps of the U.S. War Department concluded a contract with the Wrights for an airplane. Almost simultaneously, they signed a contract with a Frenchman to form a syndicate for the rights to manufacture, sell or license the use of the Wright airplane in France.

1907 Type Machines

Wilbur and Orville revamped their 1905 machine, to permit the pilot to sit upright instead of lying prone, and to carry at least one passenger. The control system was redesigned to accommodate the new seating position.

The 1907 type machines were built and flown between 1907 and 1909. They were sometimes referred to as Wright Model A although the Wrights never used that designation. The various types were of similar configuration but varied in dimension.

In May 1908 the Wrights took a machine to Kitty Hawk to prepare for the demonstrations they would make in France and at Ft. Myer.

Wright airplanes of the 1907 type include: the machine shipped to Europe in 1907 and flown by Wilbur in France from 1908 to March 1909; the airplane that Orville flew in the first Army tests at Fort Myer and wrecked on September 17, 1908; the airplane assembled at Pau and shipped to Rome for flights by Wilbur in April 1909; one of two machines assembled in Berlin in 1909 and flown by Orville in March and April; the machine used by Wilbur in his flights of September-October 1909 during the Hudson-Fulton Celebration in New York City and the machine flown by Orville at Montgomery Alabama in 1910.

1909, Signal Corps Machine

This airplane was Signal Corps No. 1 and sometimes referred to as the Military Flyer. Some of the differences between this modified machine and the standard 1907-type machine used the previous year were that the wing area was reduced and the propellers were closer together. The reduction in the area of the wing resulted in the need for a higher take-off speed and longer start, necessitating adding 30 feet to the starting rail.

This machine gained fame as the world’s oldest military airplane.

In August 1909, Orville made many demonstration flights during the next two months at Templehof and Potsdam with a standard Model A.

Model B, 1910-1911

The Model B was produced in 1910 and 1911. The first machine was completed on June 29, 1910. It is their first production machine and was flown by Orville for the first time over Huffman Prairie in July of 1909. Some 80-100 were believed to have been built.

The most fundamental change from the Model A was the transfer of the elevator from the front to the rear structure that held the rudder. Two fixed flaps of cloth were added to what remained of the forward structure to provide stability in turns. For the first time also, wheels were added to the undercarriage. It is the Wrights first machine to use a rear stabilizer that is now considered a traditional tail.

Signal Corps Airplanes No. 3 and No. 4, built in 1911, were Wright B Flyers and they were used for training pilots and in aerial experiments.

In 1912 the Navy fit a Model B Flyer, referred to as the B1 Flyer, with pontoons for testing as a seaplane in San Diego Bay, California.

Model R, 1910

The Model R was designed as a high-speed racer for setting speed and altitude records and was equipped with a wheeled undercarriage. It was called the “Roadster” and more popularly, the “Baby Wright.” A smaller version, the “Baby Grand, ” powered by an 8-cylinder, 60-hp engine was flown by Orville at the Belmont Park Meet in 1910. It could reach speeds up to 80-mph.

Model, EX 1911

The EX was a smaller version of the Model B. It was built mainly for flying at exhibitions. It could climb fast and reach nearly 60-mph.

A modified EX, the Vin Fiz flown by Galbraith Perry Rodgers, made the first transcontinental flight in 1911.

On May 13, 1918 Orville made his last flight as a pilot, flying a 1911 Wright airplane

Model C, 1912

The Model C was the successor to the Model B. It became the new standard production airplane for the Wright Company. The model B and the Model C airplanes were the only airplanes built by the Wright Company in quantity. The first Model C airplanes were delivered to the Army in 1912.

It employed a more powerful engine to meet Army specifications and a new control system. The specifications required the machine to climb at a rate of 200-feet per second, have a fuel supply sufficient for a four hour flight and carry a weight of 450 pounds including the pilot and passenger.

The Army originally purchased six Wright Model Cs and five of these airplanes crashed killing six men. The machine was unstable and used a twin-lever control system that was confusing to operate for inexperienced pilots.

The Model C replaced the prominent triangular blinkers of the Model B with vertical vanes attached to the forward end of the skids.

Models K and L subsequently replaced the Model C.

Unfortunately, by 1910 the Wright airplanes were beginning to fall behind the competition. The Model C was such a machine.

Between 1910 and 1915 the Wrights produced 10 different distinct aircraft designs.

What follows is a short description of some more of these designs.

Model CH, 1913

This was the first Wright seaplane. It was essentially a Model C with pontoons added. Experiments were conducted on the Miami River near Dayton, Ohio in the spring and early summer of 1913.

Model D, 1912

The Model D was designed as a light fast scout biplane for the Army. It was similar to the Model R. Its speed was about 70-mph. It had a problem in landing on rough ground, which was an Army requirement. A high landing speed caused Model D to nose over in a ploughed field.

Model E, 1913

This model used a single 7-foot pusher propeller and was designed for exhibition use. It could be dismantled and reassembled quickly. It also had two wheels instead of the usual four that had been used on all Wright airplanes built during the period of 1910-1913.

Model F, 1913

The Model F was built for the U.S. Army. It was the first Wright machine built with a fuselage. It was also the first to use the tractor propellers instead of the pusher type.

Model G, 1913-1914

This was the first deep-water flying boat. Grover Loening under supervision of Orville designed it. It was given the name, “Aeroboat.”

The hull was made of ash and spruce, covered with a special alloy treated to prevent salt-water corrosion.

Model H, 1914

The Model H looked in appearance like the Model F except that the fuselage was continuous. The fuselage was made of wood, veneered with canvas inside and out.

Model HS, 1915

This was a smaller version of Model H. It was the last Wright machine to have an double vertical rudder and the last to user pusher-type propellers.

Models I and J

These were not Wright machines. The Burgess-Wright Company built them. Glen Curtiss was involved with this company.

Orville Wright considered these machines to be infringements of the Wright patents.

Model K, 1915

The Model K was a seaplane built for the U.S. Navy. It was the first tractor plane produced by the Wright Company and the last to use the Wright “bent end” propellers that were first used in 1905.

It was also the first Wright machine to utilize modern-type ailerons on both the upper and lower wings instead of using wingwarping. Wingwarping had been used on all Wright machine and gliders since 1899.

Model L, 1916

This airplane was offered for sale after Orville had sold the Wright Company.

It was a single-place light-scout biplane designed for high-speed reconnaissance. It bore no resemblance to the early Wright biplanes.

Reference: “The Papers of Wilbur and Orville Wright,” by Marvin W. McFarland, Editor.

While engaged in the bicycle manufacturing and repair business in 1897 and 1898 in their shop at 22 South Williams St., the Wrights focused their attention on the problems of mechanical and human flight.

Otto Lilienthal, German engineer and aeronautical pioneer, died in Germany on August 10, 1896 following injuries suffered in a crash the previous day of his latest single-surface glider with an adjustable horizontal tail. This event triggered the Wrights interest in solving the problem of flight and the question of whether they could go on from where he had left off. They decided to begin by conducting “a systemic study of the subject in preparation for practical work.”

Wilbur was familiar with the flying activities of Lilienthal from reading an article on Lilienthal entitled “The Flying Man” in McClure’s Magazine that they had access to in their father’s library. He also had access to books on the work of Cayley, Penaud and Marey.

Wilbur visited the Dayton Public Library to obtain more information but they had nothing on the subject of human flight. He decided to write to the Smithsonian Institution on May 30, 1899.

Here is a copy of that letter including some of my comments:

Dear Sirs;

I have been interested in the problem of mechanical and human flight ever since as a boy I constructed a number of bats of various sizes after the style of Cayley’s and Penaud’s machines. My observations since have only convinced me more firmly that human flight is possible and practicable.

Comment: Bishop Milton Wright, on return from a short trip on church business, brought home a toy Penaud-type helicopter using twisted rubber bands for motive power, arousing the boy’s first interest in flight. They discovered their first mystery about flight when they tried to build larger versions of the toy and found they wouldn’t fly. They didn’t know then that as the linear measurement of a model is doubled it needs about eight times the power to fly.

Sir George Cayley engraved an image of a flying machine on a silver disk in 1799. That imprint was the first to resemble the configuration of a modern airplane. Through the next decade he built both model and full-size gliders.

It is only a question of knowledge and skill just as in all acrobatic feats. Birds are the most perfectly trained gymnasts in the world and are specially well fitted for their work, and it may be that man will never equal them, but no one who has watched a bird chasing an insect or another bird can doubt that feats are performed which require three or four times the effort required in ordinary flight. I believe that simple flight at least is possible to man and that the experiments and investigations of a large number of independent workers will result in the accumulation of information and knowledge and skill which will finally lead to accomplished flight.

The works on the subject to which I have had access are Marey’s and Jamieson’s books published by Appleton’s and various magazine and cyclopaedic articles.

Comment: The Jamieson’s books published by Appleton are somewhat of a mystery because they have never been found. It is known that an Andrew Jamieson was an author of a textbook on Applied Mechanics.

I am about to begin a systematic study of the subject in preparation for practical work which I expect to devote what time I can spare from regular business. I wish to obtain such papers as Smithsonian Institution has published on this subject, and if possible a list of other works in print in the English language. I am an enthusiast, but not a crank in the sense that I have some pet theories as to the proper construction of a flying machine.

Comment: There had been so many failed attempts to fly that many believed that flying was impossible. Wilbur apparently wanted to make it clear he was not some crackpot.

I wish to avail myself of all that is already known and then if possible add my mite to help on the future worker who will attain success. I don not know the terms on which you send out your publications but if you will inform me of the cost I will remit the price.

Yours truly,

Wilbur Wright

On June 2nd, only three days later, Richard Rathbun, assistant secretary of the Smithsonian sent the Wrights a list of works and four Smithsonian pamphlets on the subject of aerial navigation, which further stimulates the Wrights’ interest in gliding as a sport.

On June 14, Wilbur acknowledges Rathbun’s letter and orders a copy of Samuel P. Langley’s “Experiments in Aerodynamics.”

The Wrights decide that control is the primary problem to solve. During July and August they construct and Wilbur tests and flies a biplane kite with a five-foot wingspan that incorporates their idea of wing warping to effect control in the roll dimension. The successful kite experiment encourages them to proceed with the building of a man-carrying machine embodying this principle.

The kite hung on a wall of a room over their bike shop until destroyed about 1905 to make room for an upstairs office.

On November 27 Wilbur wrote to the U.S. Weather Bureau for information on a suitable place to conduct their flying experiments.

By the 1800s investigators were beginning to close in on the ability to fly a heavier than air machine. Sir George Cayley provided the revolutionary breakthrough that incorporated all the elements of the modern airplane.

Following his lead, investigators in the nineteenth century followed three different paradigms. Choosing the right one was critical to ultimate success.

The first was to experiment with small-scale models. The second was to build and try to fly full size machines. The third was to investigate with full-scale manned gliders. The Wright brothers chose the latter and were the first to be successful.

Prior to Cayley the dominant paradigm was to mimic birds by building machines with flapping wings. Unfortunately, for all the bird watching they did, they didn’t understand how birds fly. They thought that birds swim across the sky, propelled by a downward and backward stroke.

In reality, the wings move forward on the downstroke. A bird’s forward thrust comes from the outer primary feathers of the wing tips, which serve as propellers. As the downstroke begins, the tips of the primaries are bent and twisted upward at their trailing edges. In this position they bite into the air as an airplane’s propeller does. The biting action impels the feathers forward, pulling with them the wing and the bird’s body.

Many experimenters were injured or died trying to fly like a bird.

In 1804, Cayley, at the age of 21, designed and hand-launched a small glider that had all the elements of a modern airplane. The glider contained the three essential features of a modern airplane. It contained a fixed wing, a body or fuselage, and a tail with both horizontal and vertical surfaces.

In his simple glider he had recognized the three essential ingredients of flight. His wing was curved because it produced more lift than a flat surface. His tail recognized the need for stabilization and control in flight. He also recognized the glider needed a power source although he didn’t have one at the time.

The first experimenters that followed experimented with small-scale models. One was Alphonse Penaud, a French marine engineer. In the 1860s and 1870s he built and experimented with a series of small flying models powered by twisted rubber bands. Wilbur and Orville played with such a model while children.

Penaud experimented with different configurations to improve the inherent stability of his models. The idea of using a pilot would came later, after a straight-line flight with a passenger could be demonstrated. His emphasis on automatic stability was a significant limitation of his approach. His best flights were only 13-14 seconds long because of lack of a good power source.

The most famous of the experimenters that followed the small-scale model approach was Samuel Langley, the secretary of the Smithsonian Institution and the unofficial chief scientist of the United States.

On May 6, 1896, he successfully flew a steam-powered 30-pound model airplane with 13-foot tandem wings. He launched the model with a spring-powered catapult from the roof of a houseboat in the Potomac River with Alexander Graham Bell in attendance. In November, he launched another model that flew almost a mile.

Langley had proved that powered flight was possible. His downfall was that his paradigm assumed that he could scale up his successful small model to a full-scale airplane. He would find that this assumption was in serious error.

He launched the full-size version of his airplane, the Great Aerodrome, with a passenger on October 7, 1903 and December 8, 1903. The machine crashed on takeoff both times.

His highly publicized failure was so ridiculed that when the Wrights flew just nine days later at Kitty Hawk, few people believed them, including the U.S. government who in today’s dollars spent the equivalent of $1.5 million on Langley’s Aerodrome.

Another paradigm of aeronautical experimentation was to build full size airplanes and try to fly them with a person on board. Pioneers of this approach included William Henson, John Stringfellow, Hiram Maxim and Clement Ader.

Engineers William Henson and John Stringfellow, inspired by Cayley’s ideas designed what they called an “Aerial Steam Carriage” that they planned to build. The publication of an article in a 1843 Mechanics Magazine received much notoriety.

It was a graceful monoplane about the size of a DC-10. The engines could produce thousands of horsepower with its two six-bladed rear propellers driven by a 25-hp steam engine designed by Stringfellow.

The plane was never built. They did build a smaller version model that never flew.

Their work did serve one important purpose. The many fanciful pictures of their proposed machine published in newspapers and magazines ingrained in people what an airplane should look like.

The first American to think seriously about powered flight was Hiram Maxim. He migrated to England where he invented the machine gun and became rich and famous.

He built a huge airplane that weighed some 4-tons including the crew and the hundreds of pounds of water required by two 180-hp steam engines. The machine was about 2,300-feet long and had a wingspan of 104 feet with 18-foot propellers. He called it the “Leviathan.”

On July 31, 1894, with Maxim at the controls along with two other people, the machine surged down a track for about 200-feet and briefly lifted off the steel rails a few inches, crashed through the guide rails, and came to a stop 600-feet from where it started.

The machine had serious problems. It was aerodynamically unsound, structurally weak and uncontrollable. He never built another airplane, but he wrote many articles for popular magazines that did serve to stimulate interest in aeronautical research.

The third paradigm is to investigate the problems of flight using full-scale manned gliders. The approach was initiated by Cayley, embellished by Otto Lilienthal and Octave Chanute and the breakthrough to successful manned flight achieved by the Wright brothers. The brothers admired Lilienthal’s work and they communicated regularly with Chanute.

There were others who had earlier tried using gliders but Lilienthal was the first to persist. He built his first hang glider in 1891 and flew from a cone-shaped hill he built near Berlin. He built a succession of gliders, each incorporating what he had learned on the last one.

He was learning how to fly. No one before him had stayed in the air long enough to learn how to fly. He earned the nickname “The Flying Man.”

He wrote a book and a number of articles explaining his techniques and aerodynamic principles. As his flights continued, he began to make gliders that were easier to control and to think about adding a small engine.

Unfortunately, he had a serious problem with control that would end his life. He was controlling his glider by the ineffective movement of his body.

During a practice flight on August 9, 1896, he was hit by a strong gust of wind that caused his glider to nose up and stall. His body movement was not effective in correcting the movement and the glider went into a terminal spin and crashed, breaking his back. He died the next day.

Veteran engineer Octave Chanute with the help of a young engineer named Augustus Herring, made a number of glider flights in 1896 at the Indiana Dunes on the shores of Lake Michigan. In the process he developed the first modern aeronautical structure.

It was a biplane made with a single rigid box structure with bracing consisting of crossed diagonal wires and upright struts. It was similar to the Pratt truss used in the structure of bridges. Chanute, a bridge engineer, was familiar with the design.

Chanute, like his predecessors, believed in building an airplane with automatic stability. With that goal in mind he added a flexible cross-shaped vertical and horizontal tail (cruciform configuration), which would supposedly permit the glider to adjust to rough winds. The problem of effective control, however, still remained to be solved.

In September 1896, the glider flew one flight of 359 feet that lasted 14 seconds. This exceeded any of Lilienthal’s flights.

The Wright brothers studied what the others had accomplished and decided that the conventional wisdom they had about designing a machine that was inherently stable was wrong. They were ultimately successful because they chose to ignore the conventional wisdom and design a machine that was controllable by a pilot.

They were influenced by their experience with bicycles. They knew that a bicycle was an inherently unstable machine but could be mastered with practice.

Using a paradigm of building full-scale gliders that were controllable by a pilot, and then adding power, they were able solve the problems of flight and flew on December 17, 1903.

As Orville later wrote, that flight was “the first in history of the world in which a machine carrying a man had raised itself by its own power into the air in full flight, had sailed forward without reduction of speed, and had finally landed at a point as high as that from which it started.”

Reference: The Bird Is On the Wing by James R. Hansen

In an extraordinary letter to Octave Chanute on May 13, 1900, Wilbur Wright reveals for the first time in writing his vision, aeronautical principles and plans to develop a machine that man can fly.

He chooses Chanute for his disclosure because of Chanute’s worldwide reputation as an expert on the history of aviation. In 1894, Chanute had published, “Progress in Flying Machines,” a compendium of practically all significant aeronautical works up to that time. Wilbur became aware of the book after his inquiry for information to the Smithsonian Institution the year before.

Wilbur is just beginning to emerge from the depression that has haunted him from the time he was injured in a hockey accident in high school. He knows that he has the ability to do something significant in his life. Solving the riddle of flight may be just that thing. Now he needs someone important involved in flight to give him confidence to proceed with his vision.

The carefully worded letter does the trick and triggers the beginning of a ten-year close relationship between the two, involving some 400 letters of correspondence until Chanute’s death in 1910.

Chanute was 45 years older than Wilbur. Wilbur was looking for feedback and confirmation from the senior engineer.

Here is the letter. I have taken the liberty to comment on its contents at various intervals.

The letter was written on stationery of the Wright Cycle Company, 1127 West Third Street.

“Mr. Octave Chanute, Esq, Chicago, Ill.”

“For some years I have been afflicted with the belief that flight is possible for man. My disease has increased in severity and I feel that it will soon cost me an increased amount of money if not my life. I have been trying to arrange my affairs in such a way that I can devote my entire time for a few months to experiment in the field.”

Comment: Here we see Wilbur’s passion, desire, and commitment to a task with great odds against success and risk to his life.

“My general ideas of the subject are similar to those held by most practical experimenters, to wit: that what is chiefly needed is skill rather than machinery. The flight of the buzzard and similar sailers is a convincing demonstration of the value of skill and the partial needlessness of motors. 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.”

Comment: Wilbur, unlike most if not all other experimenters at the time, points out the importance of a skilled pilot. From his experience with bicycles, he knew that a bicycle rider can control an inherently unstable bicycle once he learns how to do it through practice.

“Assuming then that Lilienthal was correct in his ideas of the principles on which man should proceed, I conceive that his failure was due chiefly to the inadequacy of his method, and of his apparatus. As to his method, the fact that in five years’ time he spent only about five hours, altogether, in actual flight is sufficient to show that his method was inadequate. Even the simplest intellectual or acrobatic feats could never be learned with so short practice, and even Methuselah could never have become an expert stenographer with one hour per year for practice. I also conceive Lilienthal’s apparatus to be inadequate not only from the fact that he failed, but my observations of the flight of birds convince me that birds use more positive and energetic methods of regaining equilibrium than that of shifting the center of gravity.”

Comment: Wilbur had much respect for the German aeronautical pioneer Otto Lilienthal who died in a crash when his glider lost lateral balance in 1896. However, Wilbur points out that Lilienthal was on the wrong track for two reasons. First, Lilienthal failed because his approach was not providing him enough flying time to learn the skills needed to fly. Secondly, his technique was wrong. He tried to maintain equilibrium of his glider by changing the center of gravity through shifting the weight of his body. Sadly, his good intentions, but faulty approach, resulted in his death.

In the next paragraphs Wilbur explains his approach.

“With this general statement of my principles and belief I will proceed to describe the plan and apparatus it is my intention to test. In explaining these, my object is to learn to what extent similar plans have been tested and found to be failures, and also to obtain such suggestions as your great knowledge and experience might enable you to give me. I make no secret of my plans for the reason that I believe no financial profit will accrue to the inventor of the first flying machine, and that only those who are willing to give as well as to receive suggestions can hope to link their names with the honor of its discovery. The problem is too great for one man alone and unaided to solve in secret.”

Comment: Here he lays out his plan to follow the Scientific Method, i.e. gather data, and proceed from hypothesis based on principles and test for practicality. He recognizes that the task is not easy. He will soon change his mind about sharing information with others when he finds that others have little to offer and want to copy his ideas.

“My plan is this. I shall in a suitable locality erect a light tower about one hundred and fifty feet high. A rope passing over a pulley at the top will serve as a sort of kite string. It will be so counterbalanced that when the rope is drawn out one hundred and fifty feet it will sustain a pull equal to the weight of the operator and apparatus or nearly so. The wind will blow the machine out from the base of the tower and the weight will be sustained partly by the upward pull of the rope and partly by the lift of the wind. The counterbalance will be so arranged that the pull decreases as the line becomes shorter and ceases when its length has been decreased to one hundred feet. The aim will be to eventually practice in a wind capable of sustaining the operator at a height equal to the top of the tower. The pull of the rope will take the place of a motor in counteracting drift (drag). I see, of course, that the pull of the rope will introduce complications which are not met in free flight, but if the plan will only enable me to remain in the air for practice by the hour instead of by the second, I hope to acquire skill sufficient to overcome both the difficulties and those inherent to flight.

Knowledge and skill in handling the machine are absolute essentials to flight and it is impossible to obtain them without extensive practice. The method employed by Mr. Pilcher of towing with horses in many respects is better than that I propose to employ, but offers no guarantee that the experimenter will escape accident long enough to acquire skill sufficient to prevent accident. In my plan I rely on the rope and counterbalance to at least break the force of a fall.”

Comment: The Wrights do not use the tower idea during the first visit to Kitty Hawk. At first they flew the glider like a kite. Then Wilbur found he could safely ride the glider in the prone position down the slope of a sand dune. Chanute in his response to this letter had advised Wilbur not to use the tower, rather glide off the dunes.

Percy Pilcher was an assistant lecturer in naval architecture and marine engineering at the University of Glasgow. He was inspired by the gliding experiments of Lilienthal and even visited Lilienthal in Germany. Pilcher constructed a number of gliders and had plans to apply a motor to one of them. While giving a glider demonstration to a group of Englishman on his estate, he crashed and died in 1899.

“My observation of a flight of buzzards leads me to believe that they regain their lateral balance, when partly overturned by a gust of wind by a torsion of the tips of the wings. If the rear edge of the right wing tip is twisted upward and left downward the bird becomes an animated windmill and instantly begins to turn, a line from its head to its tail being the axis. It thus regains its level even if thrown on its beam ends, so to speak, as I have frequently seen them. I think the bird also in general retains its lateral equilibrium partly by presenting its two wings at different angles to the wind, and partly by drawing in one wing, thus reducing its area. I incline to the belief that the first is the more important and usual method.”

Comment: Wilbur describes his discovery of how birds maintain equilibrium. He applies this concept to the building of a five foot, bi-wing kite in 1899. It works! He’s now ready to apply the concept to a glider that he can fly.

” In the apparatus that I intend to employ I make use of the torsion principle. In appearance it is very similar to the double-deck machine with which the experiments of yourself and Mr. Herring were conducted in 1896-7.”

Comment: He tells Chanute he plans to use Chanute’s idea of a bi-wing, Pratt truss design.

“The point on which it differs in principle is that the cross-stays which prevent the upper plane from moving forward and backward are removed, and each end of the upper plane is independently moved forward or backward with respect to the lower plane by a suitable lever or other arrangement. By this plan the whole upper plane may be moved forward or backward, to attain longitudinal equilibrium, by moving both hands forward or backward together. Lateral equilibrium is gained by moving one end more than the other or by moving them in opposite direction. If you will make a square cardboard tube two inches in diameter and eight or ten long and choose two sides for your planes you will at once see the torsional effect of moving one end of the upper plane forward and the other backward, and how this effect is attained without lateral stiffness.”

Comment: Here Wilbur reveals the concept of “wingwarping.” He believes that effective control is the key to successful flight. Wingwarping provides lateral control of an airplane. Lack of such control is what killed Lilienthal and Pilcher.

Wilbur explains the concept by using as the example the now famous bicycle tube box. Wilbur was talking to a customer one day when he absentmindedly twisted the ends of the narrow box in opposite directions. He immediately conceptualized a pair of biplane wings, vertically rigid yet twisted into opposing angles at the tips.

Chanute never does understand the concept of wingwarping. He was focused on developing a way to build automatic stability into his gliders.

“I plan to attach the tail rigidly to the rear upright stays which connect the planes, the effect of which will be that the upper plane is thrown forward the end of the tail is elevated, so that the tail assists gravity in restoring longitudinal balance. My experiments hitherto with this apparatus have been confined to machines spreading about fifteen square feet of surface, and have been sufficiently encouraging to induce me to lay plans for a trial with a full-sized machine.”

Comment: Wilbur’s kite in 1899 was rigged so that he could warp the wings.

The Wrights used a horizontal tail. The vertical tail was first used on the 1902 glider.

“My business requires that my experimental work be confined to the months between September and January and I would be particularly thankful for advice as to a suitable locality where I could depend on winds of about fifteen miles per hour without rain of too inclement weather. I am certain that such localities are rare.”

Comment: Wilbur explains he doesn’t want his experiments to interfere with the bicycle business.

Chanute suggests locations in San Diego, Pine Island, Florida and the Atlantic Coasts of South Carolina and Georgia.

Wilbur also wrote to the U.S. Weather Bureau, which resulted in the selection of Kitty Hawk.

“I have your Progress in Flying Machines and your articles in the Annuals of ’95, ’96 and ’97, as also your recent articles in the Independent. If you can give me information as to where an account of Pilcher’s experiments can be obtained I would greatly appreciate your kindness.”

“Yours truly,

Wilbur Wright”

Comment: Chanute had little to offer on Pilcher.

Wilbur does receive the response he was looking for from his letter when Chanute responded that he was “pleased to correspond with you further and to have a more detailed account of your proposal.”