"Celebrate The Success Of The Wright Brothers"  
 


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The Secret of Flight

Since ancient times mankind has looked up to view birds flying and dreamed of flying.

The Wright brothers were no different. They often rode their bicycles to a popular picnic area south of Dayton called the "Pinnacles" to observe the many birds that flew there. Early on they decided that practical flight was possible by man using soaring large birds as their model.

The Pinnacles consisted of a gorge with a river flowing through it and unique large boulders created during the ice age on its slopes. The updraft created by the terrain attracted soaring birds. The Wright brothers regularly observed birds there from 1897 to 1899.

The Wrights developed their wing warping theory in the summer of 1899 after observing the buzzards at Pinnacle Hill twisting the tips of their wings as they soared into the wind.

The Wrights made the right decision by focusing on large birds. It turns out that small birds don’t change the shape of their wings when flying, rather they change the speed of their flapping wings. For example, to start a left turn, the right wing is flapped more vigorously.

To turn right the speed of flapping is changed to the other wing.

To fly straight, both wings are flapped at the same speed.

Incidentally, the technique is the same for creatures from fruit flies and moths to hummingbirds and cockatoos.

These findings were found through research with high-speed video of seven species at the universities of Delaware and North Carolina.

 

Is It About the Money?

Fred C. Kelly, the Wright brothers’ first biographer asked Orville in 1939 if it was the profit motive that motivated he and his brother to invent the airplane.

He reflected for a moment before responding, "I hardly think so. I doubt if Alexander Graham Bell expected to make much out of the telephone. It seems unlikely that Edison started out with the idea of making money. Certainly Steinmetz had little interest in financial reward. All he asked of life was the opportunity to spend as much time as possible in the laboratory working at problems that interested him."

Kelly asked, "And the Wright brothers?"

Orville chuckled. "If we had been interested in invention with the idea of profit, we most assuredly would have tried something in which the chances for success were brighter. You see, we did not expect in the beginning to go beyond gliding."

"Even later we didn’t suppose the aeroplane could ever be practical outside the realm of sport. It was the sport of the thing that appealed to Will and me."

"The question was not of money from flying but how we could get money enough to keep on entertaining ourselves with it."

"It was something to spend money on, just as a man spends on golf, if that interests them, with no idea of making it pay."

Kelly: "You didn’t foresee commercial planes or transcontinental and trans-Atlantic flights?"

Orville: "No; and in our wildest dreams, even after we had flown, we never imagined it would ever be possible to fly or make landings at night."

Kelly: "Still, it seems strange that you didn’t have more of a profit motive, inasmuch as you had been in business as a means of making a living and obliged to make the business pay. Didn’t you go into the printing business as a youngster to make money?"

Orville: Shaking his head with a smile replied. "I got interested in printing after my curiosity had been aroused by some woodcuts I saw in the Century magazine, and I tried to make some tools for carving wood blocks. The first tool was made from the spring of an old pocket-knife."

"Gradually I became more and more interested in printing. But, making it pay its way came as an afterthought."

Their father, Bishop Milton Wright used to say, "All the money anyone needs is just enough to prevent one from being a burden on others." Following their father’s advice, the brothers tried to earn their own spending money and never became interested in a hobby because it might be profitable.

When the Wrights were conducting their wind tunnel experiments, they became concerned that their experiments were taking too much time and money for their modest means. They were worried that they would not get their money back and permitting their hobby to become too much of a luxury.

Wilbur was inclined to drop their researches. Orville thought they should continue a little longer. If Wilbur had quit, Orville would have too.

While they were still debating the issue, a letter arrived from their friend and mentor Octave Chanute. Chanute, suspecting their resolve to continue was weakening, urged them to continue with their experiments.

He reminded them that they already had valuable knowledge of aeronautics far beyond that possessed by anyone else in the world. To go on was almost a duty. And so the Wrights shelved their concerns and continued their research.

One thing they did do to save money was to experiment as much as possible on paper rather than making mechanical models. Before they built anything they were reasonably certain it was scientifically correct. They spent much time on grueling mathematical work before flight was possible.

Their insistence on doing everything possible on paper was successful in keeping costs down. Kelly claims that up to the day when they actually flew, the Wrights’ total outlay of money was a trifle less than $2,000. Some more recent estimates are that they spent event less, closer to $1,200.

Even after the Wrights had flown, they still did not know if they had done anything from which they could gain a fortune. They accepted the money that fell unexpectedly into their laps, but Orville said to Kelly, "I am not sure it’s quite decent to live on income from interest-bearing paper."

Kelly said that he once said to Orville that even though what you accomplished was without the idea of making money, the fact remains that the Wright brothers will always be favorite examples of how American lads, with no special advantages, can forge ahead and become famous.

In response Orville protested, "But that isn’t true because we did have special advantages.

Kelly: "What special advantages?"

"Simply that we were lucky enough to grow up in a home environment where there was always much encouragement to children to pursue intellectual interests. We were taught to cultivate the encyclopedia habit, to look up facts about whatever aroused our curiosity. In a different kind of environment I imagine our curiosity might have been nipped long before it could have borne fruit."

Reference: Harpers Magazine, "How the Wright Brothers Began," Fred C. Kelly, October 1939.

 

Tom Crouch Talks Wright Brothers

The following is a talk that Tom Crouch gave on August 19, 2007. Crouch is senior curator of aeronautics at the National Air and Space Museum of the Smithsonian Institution and author of "The Bishop Boys" and other books. The talk took place during the morning in the Pavilion auditorium at the Wright Brothers National Memorial, Kill Devil Hills.

Crouch: Today, August 19, 2007 is a special day. It is Orville Wright’s birthday. It is also since 1938, National Aviation Day as well. And to really top it off, it is Katharine Wright’s birthday. Orville Wright and his sister, who is three years younger than Orville, were born on the same day. If Orville were alive today he would be 136 years old.

Orville was half of the team who invented the airplane. Wilbur was four years older than Orville. They lived in Dayton, Ohio where I was born. Their father was a bishop in a church and had an extraordinary impact on their lives.

When I wrote a biography of the Wright brothers, I called it, "The Bishop Boys," to honor their father. Their mother was extraordinary as well. The Bishop couldn’t pound a nail straight; he wasn’t a very mechanical guy. Their mother was interested in mathematics and science and grew up in her father’s carriage shop and developed suburb mechanical skills.

Both parents contributed enormously to the invention of the airplane. They had great parenting skills and techniques. They were the kind of parents that did everything they could to encourage the curiosity of their children. They tried to answer the questions that the kids had and encouraged them to conduct their own experiments to get answers to their questions and it gave them enormous self confidence in their own capacity to do things.

One of the most extraordinary things about the Wright brothers psychologically, without which they never would have invented the airplane, was this extraordinary intellectual self-confidence that they had. These were two guys who had not gone to college and yet they were absolutely sure that when they conducted a piece of work they could trust the answer. So, they had that going for them.

Wilbur and Orville were close to one another. They had often said that growing up they had shared lots of things together such as their toys and ideas. They had played together and conducted experiments together and all that. Again, that is something else they had going for them.

I think that if they hadn’t been as close as they were, the two of them, they might not have been able to do what they did as single individuals. When it comes to the Wright brothers the whole was a whole lot greater than the sum of the parts. Together they were a pretty extraordinary team.

But they had distances too. Wilbur, for example, cared very little about personal appearance and that sort of thing.

Orville on the other hand was very much interested in all of that. He was the snappiest dresser in the family. To such an extent that when Wilbur went off in November 1901 to give the biggest speech of their lives, one of the most important speeches in the entire history of aeronautics, he went wearing his brother’s suit because Kate, their sister, recognized that Orville’s suit was in better shape and a lot better looking than Wilbur’s best outfit. So Wilbur gave his speech in Orville’s suit, shirt and tie.

Why did they go to Kitty Hawk? Why didn’t they do what they were going to do in Dayton? The answer is that Dayton is not a very windy place.

When the Wright brothers first became interested in flight, the first thing they did was to really take a look at the literature of flight that existed at that time. These guys were not college graduates, but at the same time, they were engineers of absolute genius. And they started out exactly the right way by reading what other people had written about flight.

As they drew some conclusions out of that reading, it was Wilbur who said, "look you can reduce this problem to three basic systems. If you are going to invent an airplane you have to have wings that are going to generate lift, you got to have a propulsion system that will move the wings through the air and you got to have a way to control the wings once you’re in the air. Lift, aerodynamics, propulsion and control – that’s it."

As they looked around they recognized that people had learned something about wing design, for example. Not as much as the Wright brothers had originally thought they had, but at least enough to give them a starting point. And from the looks of what other experimenters had done with wings. They saw that they could actually calculate the amount of lift that a given wing design would generate in a wind of a particular speed.

When they ran the numbers they discovered that you were either going to have to build a pretty huge machine or you were going to have to fly in a pretty substantial steady headwind. They couldn’t find that kind of headwind in Dayton.

So they wrote to the U.S. Weather Bureau which kindly sent them weather statements with average winds at all the weather stations from coast to coast in the United States. It turned out that the windiest places actually were, as you might expect, cities on lakes. Places like Chicago and Buffalo, New York and places like that.

The Wright brothers didn’t want to conduct their experiments in urban areas. They really wanted to do this sort of on their own away from prying eyes and newspaper reporters and that kind of thing. So they went down the list. The first really rural isolated place on the list was Kitty Hawk, NC.

Where we are sitting now at the memorial is not Kitty Hawk, rather it is Kill Devil Hill. Kitty Hawk is located some four miles north of here. That is where the weather station was also located. And so when the Wright brothers found out about this windy little place on the isolated outer banks of NC, they wrote a guy named Joe Dosher who was running the weather station at that point and the only employee of the weather service at that time.

Dosher sent a short note back to the Wrights, but he recognized there were probably people in the village who were better than him to explain what this place was like to the Wright brothers than him. He turned Wilbur’s letter over to Bill Tate. Tate’s wife was the postmaster of Kitty Hawk. Bill had been the postmaster of Kitty Hawk, but his wife was doing it at the time.

Bill Tate wrote the brothers a very long and wonderful letter back talking about the fact that yes, if you guys want winds to fly into, we have dunes that you could conduct your experiments from and there are not a lot of trees that you can run into. The letter was just enough to let the Wright brothers know that in fact this was going to be a pretty good place to come.

But I think the clincher was that at the end of the letter Tate said something like "if you come down here, I can promise you one thing, you will find friendly people who will do what they can to extend a hand and help you with your experiments."

I’m pretty sure that is what sold the Wright brothers on Kitty Hawk.

Wilbur set out for Kitty Hawk by himself. They had mostly prefabricated the glider in Dayton. So he set out on what was the greatest adventure of his life.

These guys were middleclass small businessmen from Dayton, Ohio. They had gone to the Chicago World’s Fair, but they really weren’t great travelers. So this really was an adventure for Wilbur Wright.

He set out from Dayton on a Big Four train for Cincinnati. In Cincinnati he changed to a B &O train which came all the way down the Ohio River, cut down across West Virginia, down through Virginia, passed Charlottesville, Gordonsville, and all the way down to Hampton Roads.

At Hampton Roads he had to get all his stuff on a steamer that would take him across Hampton Roads. He could catch the Southern Railroad train on the other side of Hampton Roads that would take him on down to Elizabeth City, where he had to buy some of the additional things he needed for the glider.

When he got to Elizabeth City, that was the end of the line. He had no idea how to get out here to Kitty Hawk. He had to go down to the docks and ask around for a guide who was willing to take him and his equipment across Albermarle Sound. He sailed on a leaky old sailboat into Kitty Hawk Bay spent the night on the boat anchored just off shore. The next morning he came ashore with all of his stuff.

Orville came down a little bit later that year. Wilbur told him it was a good place and I’m working on the glider. So Orville comes down.

They flew three gliders at Kitty Hawk --- 1900, 1901, and 1902. The 1900 season was a little disappointing. They discovered that the glider they had designed so carefully didn’t generate as much lift as they had calculated it was going to.

They didn’t give up. They went back to Dayton. They decided there is some kind of a puzzle here; we will just build a bigger glider.

They came back to Kitty Hawk the next year, 1901, with a bigger glider and that was the first time they could really make genuine flights.

It was also the first time they got really scared. Now for the first time they were actually in the air and they discovered that although they had a pretty good notion of control, they could now recognize that they didn’t really have a good handle on control.

And once more this airplane was still not generating as much lift as their calculations had predicted. This meant that other people hadn’t known as much about wings as the Wright brothers had hoped they had.

So, they went back to Dayton and conducted some wind tunnel tests and came back with the 1902 glider in 1902. All the 1902 glider flights were made right outside here where the memorial now stands. There were actually four Kill Devil hills around here at the time, some of which were actually just small humps.

The 1902 flights were the first time that they had the feeling that they were home free. Now they had a machine that pretty much performed as predicted and was controllable, fairly so anyway. So they were ready to go ahead with the design of a powered flying machine, which they did.

And of course on December 17, 1903 at the base of the big Kill Devil Hill, their machine flew. They only made four flights that morning. Orville, whose birthday is today, made the first one

They took turns – Orville - Wilbur – Orville - Wilbur.

Orville’s first flight wasn’t all that much to write home to mother about – only about 120 feet, 12 seconds. But each flight was better than the one before it. By the fourth flight Wilbur was really beginning to get the hang of the thing. He flew almost 900 feet down the beach in the direction of Kitty Hawk. He was in the air almost a minute -- 59 seconds.

Again, there were control issues, but he recognized that they were getting a handle on those.

He made a hard landing at the end of that fourth flight and they had to bring the airplane back down to the hanger. They reckoned that it was going to take a couple of days to perform the repairs on it. It was cold that day and they went into the shed to warm their hands up, and to make a long story short, a wind came up, tumbled the airplane, and when that episode was over, the world’s first airplane was sort of broken sticks, snapped wire, and torn fabric. They decided to take the pieces back to Dayton.

That’s why the world’s first airplane in our museum in Washington D.C. only made four flights, those four between 10:35 and noon on Dec 17, 1903.

That’s a little something about the guy whose work we are celebrating today and his brother. And I always include their sister too.

There have always been sort of epochal stories about the extent to which Katharine, who was a schoolteacher in Dayton and the only college graduate in that generation of the family, gave money to her brothers or helped them with higher mathematics. None of that is true. They did all of that on their own.

All the money that they spent coming down here, camping out, building the airplanes, testing them, all of that came out of the bicycle shop. Everything they needed to know to build that airplane – the mathematical base that they needed, the reading they had to do -- that was all them. Kate had nothing to do with any of that.

On the other hand, I argue that if it hadn’t been for her, they might not have done what they did at all. Kate gave them a home. Neither of them ever married. They lived in their father’s home and Katharine Wright made that a home for them. After teaching at a high school all day in Dayton, she would supervise the cooks and the people that cleaned the house, and that kind of thing, and made it a home for all of them, for the Bishop as well as Wilbur and Orville.

And she was also the glue that sort of kept the family together. If you doubt that all you have to do is read Orville and Katharine Wright’s letters back and forth to one and the other. They’re wonderful letters. A friend of mine, a guy with whom I have been coming down here for 25 years, and I are editing a final volume of the Wright letters written between 1907 and the time of Wilbur’s death in 1912. We are bringing the project to an end that the original editor of the papers of Wilbur and Orville Wright always wanted to do.

But when you read those letters and again the unpublished ones too. It just comes home to you what wonderful writers and warm human beings made up this family, the extent to which they cared about one another, supported one another, and just really did their best to support one another.

So those are the two people, Orville and Kate, whose birthday we are celebrating today and its National Aviation Day too as I said. So actually we are celebrating the whole thing.

 

Orville Tells How Flying Machine Was Born

The dedication of Wright Field in 1927 presented a 5,000-acre site to the government on behalf of the citizens of Dayton. Some 600 citizens and business donated to the fund.

Orville Wright was present for the ceremony and contributed an article he wrote for the publication, "Aviation Progress," that described the early trials of inventing the airplane. "Aviation Progress" dated October 8, 1927, was a special edition covering the dedication. It was published by the National Cash Register Co. (NCR).

Here is Orville’s story:

Our interest in aeronautics dates back as far as 1899, at which time my brother, Wilbur, and I started work on the development of a heavier-than-air machine which would be sufficiently mobile to permit practical flying.

Some of our experiments were carried out in Dayton and others in Kitty Hawk, NC.

The first actual heavier-than-air machine was a glider, flown in the year 1900, at Kitty Hawk. The span of this plane was 18-feet with a chord of 5-feet.

Most of the experiments with this glider were made as a kite, operating the levers by chords from the ground.

In 1903, we developed a power machine having a span of 41-feet and a chord of 6 ½-feet. Inasmuch as we had previously been unable to secure a satisfactory motor for this plane, we developed and made one which met the requirements and which developed from 10 to 12 horsepower. The motor was a horizontal type.

The weight of the machine with operator was 750 pounds. This machine made the first flight in the history of the world at Kitty Hawk on December 17, 1903.

The flights of 1902 glider had demonstrated the efficiency of our system of maintaining equilibrium, and also the accuracy of the laboratory work upon which the design of the glider was based.

We then felt we were prepared to calculate in advance the performance with a degree of accuracy that had never been possible with data and tables possessed by our predecessors. Before leaving camp in 1902, we were already at work on the general design of a new machine which we proposed to propel with a motor.

When the motor was completed and tested, we found that it would develop 16- horsepower for a few seconds, but that the power rapidly dropped till, at the end of a minute, it was 12-horsepower. Ignorant of what a motor of this size ought to develop, we were greatly pleased with the performance.

More experience showed us that we did get one-half of the power we should have had.

We left Dayton, September 23rd, and arrived at our camp at Kill Devil Hill on Friday, the 25th.

On November 28, while giving the motor a run indoors, we thought we again saw something wrong with one of the propeller shafts. On stopping the motor we discovered that one of the tubular shafts had cracked. Immediate preparation was made for returning to Dayton to build another set of shafts.

Wilbur remained in camp while I went to get new shafts. I did not get back to camp again till Friday the 11th of December.

Saturday afternoon the machine was again ready for trial, but the wind was so light a start could not be made from level ground with the run of 60-feet permitted by our monorail track. Nor was there enough time before dark to take the machine to one of the hills where, by placing the track on a steep incline, sufficient speed could be secured in calm air.

Monday, December 14, was a beautiful day, but there was not enough wind to enable a start to be made from the level ground around camp. We therefore decided to attempt a flight from the side of Kill Devil Hill.

We arranged with the members of the Kill Devil Hill life-saving station, which was located a little over a mile from our camp, to inform them when we were ready to make the first trial of the machine.

During the night of December 16, 1903, a strong wind blew from the north. When we arose on the morning of the 17th, the puddles of water, which had been standing about the camp since the recent rains, were covered with ice. The wind had a velocity of 10 to 12 meters per second (22 to 27-miles per hour). We thought it would die down before long and so remained indoors the early part of the morning.

But when ten o’clock arrived, and the wind was as brisk as ever, we decided that we had better get the machine out and attempt a flight.

We hung out the signal for the men of the life-saving station. We thought by facing the machine into a strong wind there ought to be no trouble in launching it from the level ground about the camp.

We realized the difficulties of flying in so high a wind, but estimated that the added dangers in flight would be partly compensated for by the slower speed in landing.

After running the motor a few minutes to heat it up, I released the wire that held the machine to the track, and the machine started forward into the wind. Wilbur ran at the side of the machine, holding the wing to balance it on the track. Unlike the start on the 14th, made in calm, the machine facing 27-mile an hour wind started very slowly. Wilbur was able to stay with it until it lifted from the track after a 40-foot run.

One of the life-saving men snapped the camera for us, taking a picture just as the machine reached the end of the track and had risen to a height of about 2-feet.

The course of the flight up and down was exceedingly erratic, partly due to the irregularity of the air, and partly to lack of experience in handling the machine.

The control of the front rudder was difficult on account of its being balanced too near the center. This gave it a tendency to turn itself when started, so that it turned too far on one side and then too far on the other. As a result, the machine would rise suddenly 10-feet and then as suddenly dart for the ground.

A sudden dart a little over 100-feet from the end of the track, or a little over 120-feet from the point at which it rose into the air, ended the flight.

As the velocity of the wind was over 35-feet per second and the speed of the machine over the ground against this wind 10-feet per second, the speed of the machine relative to the air was over 45-feet per second (30.7 mph), and the length of the flight was equivalent of a flight of 450-feet made in calm air.

This flight only lasted 12-seconds had but it was nevertheless the first time in history of the world in which a machine carrying a man raised itself by its own power into the air in full flight, had sailed forward without reduction of speed, and had finally landed as high as that from which it started.

At twenty minutes after eleven Wilbur started on the second flight. The course of this flight was much like that of the first flight, very much up and down. The speed over the ground was somewhat faster than of the first flight, due to the lesser wind. The duration of the flight was less than a second longer than the first, but the distance was about 75-feet greater.

Twenty minutes later the third flight started. This one was steadier than the first one an hour before. I was proceeding along pretty well when a sudden gust from the right lifted the machine up 12 to 15 feet and turned it up sidewise in an alarming manner. It began a lively sliding off to the left. I warped the wing to try to recover lateral balance, and at the same time pointed the machine down to reach the ground as quickly as possible.

The lateral control was more effective than I had imagined, and before I reached the ground the right wing was lower than the left and struck first.

The time of the flight was 15-seconds and the distance over the ground was a little over 200-feet.

Wilbur started the fourth and last flight at just twelve o’clock. The first few hundred feet were up and down as before, but by the time 300-feet had been covered, the machine was under much better control. The course for the next four or five hundred feet had but little undulation. However, when at about 800-feet the machine began pitching again, and on one of its starts downward struck the ground.

The distance over the ground was measured and found to be 852-feet. The time of the flight was 59-seconds.

The frame supporting the front rudder was badly broken, but the main part of the machine was not injured at all.

 

Wright 1903 Flyer Performance

There are three people that can speak with authority about the flying qualities of the Wright 1903 Flyer. They are Orville Wright, Wilbur Wright and Ken Kochersberger.

Who is Ken Kochersberger? Ken is a professor at the Rochester Institute of Technology, Rochester, NY. But more important to this article is that Ken is the only other person that has successfully flown the Wright 1903 Flyer.

Ken flew a reproduction Flyer on Nov. 20, 2003 at the Wright Memorial in Kill Devil Hills. It was launched in a northerly direction into a 12-mph wind and flew 97 feet. This is the first time in 100 years that a Wright 1903 Flyer has been successfully flown and landed without damage, using an authentic engine.

Ken flew another flight of 115 feet and landed sustaining minor damage to the Flyer consisting of four broken ribs.

Two other flights were attempted. One resulted in a crash. The final flight was attempted on Dec. 17, 2003 during the Wright brothers centennial celebration at Kill Devil Hills. Unfortunately the weather was not suitable to sustain a successful flight.

This reproduction Flyer was researched and built by Ken Hyde’s Wright Experience, Warrenton, Va. They produced an exact reproduction of the original machine, including the engine, using artifacts and photographs. This plane is more faithful than the "original" Flyer hanging in the Air and Space Museum in Washington, D.C.

The Wright brothers never flew their 1903 Flyer again after their fourth successful flight in 1903. The machine was caught by a gust of wind while resting on the ground and sent tumbling over the sand, which resulted in severe damage. The Wrights dissembled and packed the parts of the airplane in crates and sent them back to Dayton.

There, it sat in storage enduring flood damage in 1913. It was taken out of storage and restored in 1916 and again in 1925. On both occasions the restoration was for display and not for flying. This resulted in some subtle but significant variations of the original structure.

Here are some observations from a pilot’s perspective on flying the Wright Experience Flyer.

The Flyer is not very comfortable to fly. Elbows must be placed to avoid the fuel mixture control and the fuel line, creating an awkward position. One must lie on the wing in an arched shape for forward visibility, not a comfortable position for long periods of time. To gain some relief, the pilot can shift around in the wingwarping cradle during the engine start prior to launch.

During takeoff it is necessary to keep the wings levels because they are only two feet off the ground. The famous picture of the first flight shows Wilbur running along side the Flyer. He had been holding the wings steady until takeoff.

The canard (front elevator) is kept neutral to reduce drag while running down the launching rail until ready for rotation. A positive canard deflection of at least 10 degrees is required to initiate flight.

The Flyer benefited by the wings being close to the ground by increased lift, "ground effect," and a reduction of "induced drag." The anhedral (curved down) shape of the wings also produced additional lift.

There was no speed indicator on the Flyer, so the pilot must estimate the speed for rotation by experience. Once takeoff speed is reached, the Flyer requires significant positive canard to rotate because of a nose-down moment caused by the thrust line.

Rotation is limited to 3.5 degrees by the physical clearance between the tail and the rail. At this rotation the target speed is 26-mph.

Complicating the process is that the flyer trims with more canard at higher speeds and less with lower speeds. This requires the pilot to continuously adjust trim reference as airspeed changes. If there is a crosswind on takeoff, the warp corrections held on the rail must be lessened immediately at rotation.

Wingwarping was found to be responsive. The hip cradle required about 14 pounds of force. This is about twice that required on the 1902 glider. A good grip is required on the canard actuator crossbar while moving the hips to prevent the body from moving instead of the cradle.

The Flyer is unstable in sideslip during takeoff because of the anhedral of the wing. The flight on Dec. 3, 2003 experienced a crosswind and upon rotation the right warp and the anhedral effect caused a right roll with the right wingtip grazing the ground. The plane recovered and continued to fly and landed with the left wing low after traveling 115-feet.

Once the Flyer is airborne, large pitch corrections are required frequently to maintain stability. The wood structure of the Flyer is flexible which makes all control inputs less responsive resulting in control lags. The machine is substantially unstable in pitch and never flies strictly at trim but operates over the full range of the canard travel.

Ken reports that the Flyer flies more like a powered kite than an aircraft, with a soft feel to the handling in part caused by the lag between the canard input and the pitch response.

The Wright Experience pilots found that they could handle the Flyer although it takes much practice to acquire the flying skills needed. They all found a new respect for the skills and talent of Orville and Wilbur.

References: Flying Qualities of the Wright Flyer: From Simulation to Flight Test, Kochersberger, K., Ken Hyde, et. al., 42nd AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, 5-8 Jan. 2004.

www.wrightexperience.com/

 

Birdflight

Since ancient times mankind has looked up to view birds in flight, envied their freedom of travel, and dreamed of flying.

The Wright brothers were no different. They liked to ride their bicycles to a popular picnic area south of Dayton called the "Pinnacles." There they would observe the soaring birds and their observations were crucial in convincing them that gaining lateral control of a flying machine would require actually changing the shape of the wing.

At first they didn’t learn anything of use to them by their observations. Later, after they had thought out certain principles, they observed the birds to see if they used the same principles.

Orville wrote many years later, "learning the secret of flight from a bird was a good deal like learning the secret of magic from a magician. After you once knew the trick and know what to look for, you see things that you did not notice when you did not know exactly what to look for."

They would have found out even more about birds and flying if they had known about a prehistoric fossil that contained a feathered flying dinosaur, the Microraptor. It was discovered in China just two years ago.

Researchers found that the only way the animal could have remained airborne was if it had split wings like those of a biplane. With this configuration, the tree-dwelling animal could jump from a high branch and glide half the length of a football field without flapping. The theory is that flying dinosaurs evolved from tree dwellers that parachuted to the ground, which then gave rise to gliders and eventually to flappers who could perform powered flight.

Over 500 years ago Leonardo da Vinci conceptualized a man-powered flying machine that would achieve both lift and thrust with flapping wings and named it the "ornithopter." Leonardo never flew his machine. Even to this day experimenters have tried this approach with limited success.

Orville wrote in the spring of 1899, "our interest in the subject (flight) was again aroused through the reading of a book on ornithology. We could not understand that there was anything about a bird that would enable it to fly that could not be built on a larger scale and used by man. At this time our thought pertained more to gliding flight and soaring. If the bird’s wings would sustain it in the air without the use of any muscular effort, we did not see why man could not be sustained by the same means."

The surest way to discovery is choosing the right path to get there. The most frequent path taken by the early pioneers who wanted to discover the secret of flight wrongly attempted a design that imitated a flapping-wing bird. This was the approach of Icarus and da Vinci.

Those who studied the straight-outstretched, motionless wings of birds like the condor, hawk and vulture which that swoop and glide for hours were closest to the right solution.

This was the approach of Otto Lilienthal in Germany who heavily influenced the Wrights. Lilienthal learned what a bird does with its wing. He found that a bird alters dihedral to change stability, varies curvature to change lift and determined the superiority of a curved wing.

He didn’t find all the answers but did more than anyone else up until the Wright brothers. The Wrights would discuss what Lilienthal was doing and were impressed by his scientific approach to flying when others were using unscientific trial and error. Some of Lilienthal’s coefficients and equations had to be superseded later, but they were remarkable at he time. Lilienthal developed and established a foundation for the science of aerodynamics.

The idea of gliding appealed to Orville and Wilbur as a sport.

A tragic event occurred that would change the destiny of the Wrights. Lilienthal was killed in a gliding accident in 1896. Orville was in bed recovering from typhoid fever (an illness that would later claim Wilbur’s life) when Wilbur read the news to him. Their ensuing discussion about what caused Lilienthal’s death and the problem of flight led them to a commitment to prove the possibility of flight. As soon as Orville recovered, they embarked on what their neighbors liked to call their "crazy doings."

Lilienthal had died because he attempted to maintain lateral balance of his glider in flight by swinging his body, an ineffective method. Wilbur and Orville reasoned that a mechanism could be designed so that a pilot with practice could maintain directional control of flight.

The Wrights had observed that gliding and soaring birds regained their lateral balance by torsion of the tips of their wings. Orville explained how that could work for a glider. "The basic idea was the adjustment of the wings to the right and left sides to different angles so as to secure different lifts on the opposite wings."

They knew that turning an airplane had to do with changing wing surfaces, though not the way that the hawks did it. That's a significant distinction. The Wrights drew inspiration form biology, but they didn't exactly copy it. The problem was how to implement the concept mechanically.

Louis Pasteur once said: "Fortune favors the prepared mind."

Wilbur was talking to a customer one day in the bicycle shop while at the same time toying with a cardboard box for a bicycle tire. He suddenly realized he had found the answer. He noticed that although the vertical end sides of the box remained rigid, the top and bottom sides could be twisted to form a new set of angles at opposite ends.

Wilbur tested his "wingwarping" idea in July 1899 using a 5-foot box kite with a fixed horizontal tail plane. Orville wrote, "According to Wilbur’s account of the tests, the model worked very successfully. It responded promptly to the warping of the surfaces, always lifting the wing that had the larger angle."

The evolution of the airplane followed in many similar aspects nature’s evolution of the earliest animals that could fly.

Orville never lost his interest in birds. In September 1905, two years after the first powered flight at Kitty Hawk, he was flying over Huffman Prairie in Dayton when he reported hitting a bird. It seems he was doing circles, chasing birds and whacked one. According to his diary. It landed dead on the upper wing.

 

Wright Airplane Configurations

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. 

 

Wilbur Writes to Smithsonian, 1899

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.

 

The Wright Paradigm

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 

 

Wilbur Discloses His Ideas and Plans

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."

 

Flying Qualities of the Reproduction Flyer

A reproduction of the 1903 Wright Flyer built by the Wright Experience (WE) made two successful flights at the Wrights Brothers National Memorial Park in December 1903. The flight on Nov. 20 marked the first time in 100 years that an authentic Wright Flyer successfully flew. The flight flew 97 feet into a 12-mph wind out of the north.

A second flight was successfully flown for 115 feet on Dec. 3rd. This flight had to cope with crosswind and upon landing with the left wing low, broke several ribs.

Several replicas of the 1903 Flyer have also flown. Replicas, however, differ in some respect such as materials, engine, and structure from the original Wright Flyer. Even the Flyer that hangs from the ceiling of the Air and Space Museum differs in some subtle respects from its original configuration.

Some of the teams that built replicas claimed that an authentic Flyer could not fly and it was dangerous to try.

The remains of the damaged original Flyer were badly damaged at Kitty Hawk in 1903 and stayed in crates in Dayton for 13 years. They were further abused when the crates were submerged in the great Dayton flood of 1913.

In 1916 Orville reconstructed the Flyer for the first time in thirteen years for display at a dedication of two new buildings at MIT in Cambridge, Mass. Damaged parts and material were replaced at that time. The reconstruction was guided by Orville’s memory because no detailed engineering drawings were ever made. Precise accuracy was not required because the plane was being reconstructed for display and not for flight.

The Flyer underwent another reconstruction in 1925 in preparation for being sent to the Science Museum of London.

The Wright Experience (WE) conducted a detailed investigation into the construction of the original Flyer using photographs and existing artifacts. They found that there were subtle but significant changes between what they discovered and the Smithsonian drawings of the Flyer made in 1985. Those drawings were considered the most accurate at the time and were used in building many of the replicas.

The reproduction Flyer built by the WE reflects changes such as the shape of the canard and the placement of bracing wires.

The WE installed a digital onboard flight data recorder on their Flyer that allowed the acquisition of 15 channels of in-flight data during the evaluation flights. They also conducted 20-hours of simulated flight tests in the wind tunnel at Langley in Hampton, Va.

What follows next is an overall summary of what the WE learned about the behavior of the Flyer.

First of all they confirmed that the Flyer is flyable; however it takes considerable knowledge and experience to do it well. The Wrights said that stability depends on the skill of the pilot because the machine was not designed to have inherent stability. The WE team gained a tremendous respect for the competence of the Wrights as operators of their flying machines, "something that 100 years of flying has not improved upon.

Some of the WE technical findings are provided next.

The lower wing is nominally 2 feet above the ground during the takeoff roll. The resulting ground effect produces a substantial contribution to lift and a reduction in induced drag.

The wings, having an anhedral shape (10-inch droop), also provide a contribution to lift as well as facilitating level flight.

Controlled flight is possible at a few feet of altitude, so the ground effect plays a significant role throughout the flight profile.

The Flyer can only rotate 3.5 degrees on takeoff before the tail will strike the rail. At this point the target rotation speed is 26-mph.

The tail assembly is hinged so that a higher degree rotation does not necessarily result in damage to the plane.

As noted before, the Flyer is substantially unstable. The Wrights wanted it that way because they wanted to exercise control over the airplane in flight. The center-of-gravity of the machine is located 2-feet aft of the 6.5-foot leading edge of the wing. The camber of the wing is 5%. The location of the center of gravity is too far to the rear and is responsible for much of the instability that caused undulation during flight.

Because of the machine’s instability, it never flies strictly at trim. It will operate over the full range of canard travel and corresponding variations in the angle of attack.

To maintain control, the Flyer must be operated within a narrow range of warp deflections and sideslip angles. Yaw is affected by the propwash over the vertical tail.

There is large roll power available and that helps reduce the need for full deflection and thereby also reduces adverse yaw.

The flight on Dec. 3rd demonstrated the roll instability of the aircraft and its behavior in side slipping conditions. About one-second after takeoff, a left crosswind caused the airplane to roll right. The pilot, Kevin Kochersberger, compensated for the crosswind by holding a slight right warp during roll.

The right wingtip hit the sand. The airplane recovered and continued to fly, although the ground strike caused a strong left roll. The left wing then struck the sand resulting in terminating the 115-foot flight.

A crosswind complicates the takeoff because warp corrections held on the rail must be lessened immediately at rotation as the angle of attack increases.

Kevin found that a positive canard deflection of least 10 degrees is necessary to initiate flight. Once takeoff speed is reached, the Flyer requires significant positive canard to rotate.

While flying, the unstable machine requires the pilot to continually make adjustments to maintain pitch. Kevin reports that the Flyer has a soft feel to its handling in part caused by the lag between the canard movement and the pitch response.

In addition to the natural instability of the airplane, it is very flexible structurally which makes all control responses a little less crisp than what a pilot would prefer.

With the canard being repeatedly operated almost to its limits, there is a sense by the pilot that the airplane is being over controlled.

The pilots from the WE found that the arched shape of their body they had to assume for forward visibility was not comfortable for long periods of time. They also found that the placement of their elbows was awkward because of the location of the fuel mixture control and the fuel line.

A good grip on the canard actuator was needed to work the hip cradle that required 14 pounds of force (same force as the Wrights found). Otherwise, the pilot’s body moves but the cradle doesn’t.

Stanley Allyn, chief executive officer of the NCR, was with Orville Wright at Wright Field shortly before Orville’s death. They were observing a new airplane in flight test.

Allyn asked Orville how he would like to fly that one. He looked startled for a moment and then answered that he couldn’t begin to.

Orville continued, "Wilbur and I lay on our stomachs, our hips in a cradle which connected to the wing tips by cables. When we shifted our hips to left or right, the wings were warped and the plane banked accordingly. We had no instruments, and had to judge how hard to push by the pressure exerted on our bodies by the plane in flight. You might say the flier just felt his way along."

And so it was in 2003 also.

Reference: "Flying Qualities of the Wright 1903 Flyer: From Simulation to Flight Test," by Kevin Kochersberger, Ken Hyde and others, AIAA-2004-0105, 42nd AIAA Aerospace Sciences Meeting, Reno, NV, Jan. 5-8, 2004

Wrights Confused Over Calculation of Lift

A frustrated Wilbur exclaimed to Orville in August 1901, "Not in a thousand years will man ever fly."

At the time they were on a train returning to Dayton after failing for the second year in a row to achieve the lift for their glider that their calculations predicted. Wilbur recorded in his diary, "Found lift of machine much less than Lilienthal’s tables would indicate, reaching only about 1/3 as much."

After further thought, Wilbur was cheered by the conclusion that the data they were using might be in error. In a speech on September 18 to the Western Society of Engineers, Wilbur suggested that "the Lilienthal tables might themselves be somewhat in error." He also questioned the accuracy of the Smeaton coefficient.

Both the Lilienthal data and the Smeaton coefficient are used in the formula for calculating lift.

Otto Lilienthal was a famous German glider experimenter who had published a table containing coefficients of lift in 1895. The coefficient of lift is a multiplying factor that takes into consideration the various angles a wing assumes with regard to the flow of air know as the "angle of attack." The value of the lift coefficient also varies with the shape of the wing.

The Smeaton Coefficient was used in the calculation of lift at the time of the Wright Brothers. It is a constant number used as a "coefficient of air pressure." It serves as a multiplying factor used to calculate the numerical value of lift in air, as compared to other mediums, such as water or oil.

John Smeaton, an engineer, determined the value of this coefficient was 0.005 in 1759, from his study of windmills. Engineers used this value for 150 years, although others questioned its value and thought it was too high, including the famous early aviation pioneer George Cayley in 1809.

Both Lilienthal, in Birdflight, and Octave Chanute, in Progress in Flying Machines, cited the 0.005 value in their books. This heavily influenced the Wrights in using the same value.

The Wrights would soon find that the 0.005 value was too high. The error was a major cause of their calculation of a lift value that was too high.

Note: The Smeaton coefficient is no longer used in modern aerodynamic problems. Problems are formulated differently. My son, who is a graduate aeronautical engineer, had never heard of Smeaton when I first asked him about it.

Smeaton wasn’t the only source of their discrepancy between actual lift and their calculated values. They incorrectly interpreted the Lilienthal tables by not understanding that the table only applied to the one wing shape that Lilienthal used in his study. The wings that the Wrights used in 1900 and 1901 had different aspect ratios as well as differences in the location of the maximum camber of the wing.

The aspect ratio is a measure of the relationship between the length of the wing to the cord (width). The aspect ratio affects the value of the lift coefficient. Lower values of aspect ratio give lower values of the lift coefficient and visa versa within limits.

The aspect ratio for the Wright 1900 glider was 3.5 and the 1901 glider was 3.3. These values were considerably lower than the aspect ratio of 6.8 for the Lilienthal test wing. In other words, the Lilienthal wing was longer and narrower compared to the Wrights’ wing. The lift coefficient from Lilienthal’s tables used by the Wrights should have been reduced by 19% to account for their use of a lower aspect ratio.

Their other problem of interpreting the Lilienthal table had to do with the location of the point of maximum camber (high point on the curved wing).

The Wrights located their maximum camber close to the leading edge of the wing. The Lilienthal test wing was a circular shaped wing with the maximum point located at the middle of the cord. Here again the value coefficient of lift read from the table should have been reduced to account for the difference in location of the maximum camber.

The cumulative impact of the above errors on the calculation of lift amounted to the 1/3 reduction in lift that Wilbur noted for the Kitty Hawk 1900 and 1901 glider flights.

The Wrights decided to take a different approach to the problem of calculating lift. Rather than further examining the existing data provided by others, they decided to compile their own. They built an instrumented wind tunnel and developed their own aerodynamic data by systematically testing some 200 airfoils of widely different shapes and configurations, going well beyond the Lilienthal table.

Shapes included squares, rectangles, and ellipses in configurations such as biplanes and triplanes. They included camber ratios ranging from 1/6 to 1/20 and maximum camber locations ranging from near the leading edge to the ½-chord position.

They found that the correct value of the Smeaton coefficient should be 0.003 and developed their own table of lift coefficients (and drag coefficients).

Their airfoil #12 was found to be the most aerodynamically efficient. Its camber was 1/20 and the aspect ratio was 6. This foil was used as a guide in designing their successful 1902 glider and ultimately the successful 1903 Flyer.

The 1902 glider had an AR of 6.7, about twice that of their previous gliders, and used camber ratios much shallower than Lilienthal test wing.

With his new knowledge and understanding, he wrote to Chanute in October 1901, "It would appear that Lilienthal is very much nearer the truth than we have heretofore been disposed to think."

It turned out to be fortunate that the Wrights had problems with the determination of lift. It led them into doing research that propelled their knowledge far beyond anyone before them and established the Wright Brothers as the leading aeronautical engineers of their day.

Reference: A History of Aerodynamics by John D. Anderson

Wrights’ First Flight Distorted by Press

The age of flight dawned on the morning of December 17, 1903 at Kitty Hawk, NC when the Wright Brothers’ engine-driven heavier-than-air Flyer lifted into the air and traveled 120 feet in 12 seconds. It was an extraordinary moment. The way that the press handled the event was far less than extraordinary.

That afternoon, after eating a leisurely lunch, the brothers set out about 2 o’clock to walk the four miles to the weather station office in Kitty Hawk. They sent a telegram of their success to their 74-year-old father in Dayton, Ohio. Three months earlier, while seeing his sons off in Dayton, Bishop Wright had given them a dollar to cover the cost of sending a telegram as soon as they made a successful flight. Now was the time.

There was no Western Union in Kitty Hawk, but Jim Dosher at the weather station had agreed to communicate with the weather bureau office in Norfolk who in turn would contact Western Union.

Dosher, however, was unable to deliver the news because of a break in the telegraph line. He telephoned Alpheus Drinkwater at another location on the Outer Banks who transmitted the coded message of the Wright Brothers’ successful flight to Norfolk. Drinkwater later said he was bit annoyed that he had to relay a few unimportant telegrams to the mainland.

(Note: The accuracy of the last paragraph involving the role of Drinkwater is in some dispute among historians. On the occasion of the dedication of the Wright Memorial in 1932, Orville Wright was asked who sent the first message - Drinkwater or Dozier? Orville stated: "The first message was sent by W. J. Dozier." - News and Observer, Nov. 20, 1932 )

Orville wrote the message that was sent as follows:

"Success four flights Thursday morning all against twenty one mile wind started from level with engine power alone average speed through air thirty one miles longest 57 seconds inform press home Christmas. Orvevelle Wright"

An error in transmission cut two seconds off the longest flight time of 59 seconds and Orville’s name was misspelled. The wind speed of 21 mph is confusing. What Orville meant to say is that the wind was at least 21 mph during each of the four flights. The first successful flight was against a 27-mph wind.

The Norfolk operator sent a return message asking if he could share the news with a reporter at the "Norfolk Virginian-Pilot." The Wrights gave an emphatic no! They wanted the first news of the event to be from Dayton.

The Norfolk operator, Jim Gray, ignored the negative answer and provided the information to a friend, H. P. Moore, at the paper. Having little information other than that provided in the telegram, the "Virginian-Pilot" fabricated a fanciful and inaccurate story that was published the next morning with the headline:

"Flying Machine Soars 3 Miles in Teeth of High Wind Over Sand Hills and Waves at Kitty Hawk on Carolina Coast."

They also offered the story to the Associated Press (AP) and when they declined the story, offered the story to twenty-one newspapers.

Meanwhile Orville’s telegram arrived at 5:25 that evening. The Wrights’ father, Milton Wright, instructed daughter Katharine to walk over to her brother Lorin’s house and ask him to take the telegram to the local newspaper office for publication.

Lorin went downtown to the offices of the "Dayton Journal" and spoke to Frank Tunison, local representative of the Associated Press. Tunison was unimpressed with the telegram saying, "If it had been 57 minutes then it might have been a news item."

Two other Dayton papers did publish an account the next day in the afternoon editions. The account in "The Dayton Daily News" gave a reasonably accurate account except that it made a big mistake in indicating that the Wrights were imitators of the world famous Alberto Santos-Dumont. The headline read "DAYTON BOYS EMULATE GREAT SANTOS-DUMONT."

Santos-Dumont was a Brazilian who pursued aviation in France. In 1901, he had dazzled the French public by rigging an engine to a hot-air balloon and flew around the Eiffel Tower. The Dayton news-editor didn’t recognize the vast difference between balloons and airplanes.

The account in "The Dayton Evening Herald" under the heading of "Dayton Boys Fly Airship," was a 350-word rehash of the fabricated story that had earlier appeared in the "Norfolk Virginian-Pilot." The AP, the day after the first flight, had sent out an abbreviated version of the Norfolk piece.

The story was full of errors. "The machine flew for three miles --- and then gracefully descended to earth at a spot selected by the man in the navigator’s car ---." "Preparatory to flight the machine was placed on a platform on a high sand hill ---." "When the end of the incline was reached the machine gradually arose until it obtained an altitude of sixty feet ---." "There are two six-blade propellers, one arranged just below the frame so as to exert an upward force when in motion and the other extends horizontally to the rear from the center of the car, furnishing the forward impetus." Orville had run around shouting, "Eureka!"

The Wrights, mystified how a short low-keyed message in a telegram could have gone so wrong, prepared a correct story on January 5th of their successful flights and gave it to the AP with a request that it be printed. It appeared in a majority of the AP newspapers the next day.

Exactly one month after the historic flight, the New York Herald still had it wrong and published an article showing a picture with two "six-bladed" propellers and an engine beneath the airplane to provide lift.

Wilbur and Orville gave no details about their airplane. It was their invention, developed at their own expense, and they did not yet intend to provide any pictures or detailed descriptions of their Flyer.

A Beautiful Body

The Wrights' flying machine had to be structurally strong, but light enough to fly. The task was made more difficult because in order to implement their wing warping system of flight control, the wings, in addition to being structurally sound, had to be flexible.

Just nine days before the Wrights' successful first powered flight, the issue of structural integrity was dramatically highlighted when Langley's highly touted aerodrome broke-up during launching. Post mortem analysis revealed inadequate structural analysis and design.

The Wrights, on the other hand, conducted careful stress analysis using engineering handbooks available at the time to estimate structural loadings on the wing spars and struts and to size and select materials.

The Wrights were concerned about safety from the very beginning, as was their father. In order to calm his fears, Wilbur wrote to their father in 1900 that "I am constructing my machine to sustain about five times my weight and am testing every piece."

The Railroad Truss

The Wrights adopted a trussed biplane design as their basic approach. The concept was adopted from their friend Octave Chanute, a retired railroad bridge builder, who had adapted a "Pratt truss" design used on railroad bridges to a biplane glider he built in 1896. 

Using the Pratt truss concept, the Wrights' designed a bi-wing structure in which the upper and lower wings were trussed one above the other with struts and cross wires to form light, sturdy wing modules. Most builders of airplanes adopted this configuration for the next two decades.

Each wing was composed of eight such cross-braced modules. The trailing edge of the outer two modules on each end was not cross-braced to allow flexibility for wing warping. In this manner they had ingeniously solved the problem of how to twist the wings tips and still retain structural integrity.

The ribs of the wings were constructed of thin strips of ash that were bent to the desired camber. Blocks of wood were glued between the two strips and glued into position. The result was a strong, lightweight rib.

Bending the wings and the wingtips to the proper curvature was farmed-out to a local firm that made parts for the carriage industry. The Wrights didn't have the necessary equipment for steaming the ash wood and then bending it to the proper camber. The wing tips were made from off-the-shelf carriage bows.

The ribs were attached to spars of kiln dried spruce. The spruce for the spars was procured from a local lumberyard. It was ordered cut into pieces of approximate length and shape. The Wrights then shaped the pieces using draw knives and spoke shaves.

All the wood pieces were painted with several coats of varnish to protect them from the high moisture environment of Kitty Hawk.

The fabric, made of Pride of the West Muslin procured from Rike-Kumler Co., a local department store located in downtown Dayton in the same block as one of their bike shops. The muslin was cut into strips and then machine-sewed with bias so that it would fit on the ribs on a 45 degree diagonal. It was then stretched over both the top and bottom sides of the spars and ribs, with each rib fitted into a sewed-in pocket. The design provided for strength as well as maintaining wing camber under stress in flight.

The wooden structure was assembled using waxed linen cord instead of nuts, bolts or screws. This design created a flexible joint that could withstand hard landings without breaking.

Orville commented that "these I believe, were the first double-surfaced airplanes ever designed or built."

Seventy-inch spruce struts supported the upper and lower wings. The Wrights realized that a vertical column of this length would require a substantial cross-section to withstand the compression load without bending and possibly breaking. This had the potential of adding considerable unneeded weight and drag.

The Wrights solved the problem by adding a horizontal wire passing through the center of the highly loaded struts in order to prevent them from bending. By this means the cross-section of the struts could be reduced and still retain structural integrity. The proof that it worked is that none of the struts failed in wings gusts of over 27 mph during their first flights on December 17, 1903.

Back To The Future

As airplanes got faster and heavier, wing warping was replaced by the use of ailerons because of structural problems. The uses of ailerons, however, do have a down side. They increase drag and weight and therefore reduce fuel efficiency and overall performance.

Because of this performance degradation, NASA, the Air Force and Boeing are working on a $41 million project to modify an F/A-18A Hornet fighter jet with a twistable wing. The purpose of the project, Active Aeroelastic Wing, is to demonstrate that subtly twisting a wing a few degrees (up to five) can control its roll with less need for big control surfaces on the wings and horizontal tail. They hope to demonstrate that the lighter-weight flexible wings will improve the maneuverability of high-performance aircraft.

The project leaders envision that the benefits of this wing warping could apply to both military and commercial airplanes.

A traditional rollout ceremony was held on March 27, 2002 at NASA's Dryden Flight Research center. The official Centennial of Flight logo in commemoration of the Wright Brothers first powered flight in 1903 was prominently displayed on the aircraft.

The ideas of Orville and Wilbur are still fresh after 100 years. 

The Power To Fly

Flight is impossible unless there is enough thrust to maintain the flying speed of an airplane. A key factor in determining whether the 1903 Wright Flyer could sustain flight is to know the thrust required to overcome aerodynamic resistance known as drag. Once drag is known, the horsepower required of the engine can be determined.

What follows is an analysis similar to what the Wrights did to answer the question of how much power was required.

Drag is generated by two different surfaces on an airplane as it moves through the air. One is caused by the lifting effect on the wings and the other by the wind resistance caused by the frontal surface area of the airplane. The first is referred to as induced drag and the latter as frictional drag.

 

Drag

The formula the Wrights used to determine drag is very similar to the formula they used to determine lift. The only difference is that the coefficient of drag (CD) replaces the coefficient of lift (CL) in the formula. The basic formula is as follows:

D = k x S x V² x CD where
D = Drag (pounds)
k = pressure coefficient of air
S = wing area (square feet)
V = relative velocity of air over the wing (mph)
CD = coefficient of drag

For the 1903 Wright Flyer:

k = 0.0033 (Wrights derived from their wind tunnel experiments)
S = 512 (wing area of 1903 Flyer)
V = 30.8 (The wind ranged from 20 mph to gusts of 27 mph at Kitty Hawk on December 17, 1903. I used an average wind of 24 mph on Dec. 17, 1903 plus ground speed of 6.8 mph. Wilbur, running at the right wing tip, had no trouble keeping up with the Flyer as it moved down the starting rail to takeoff.)

The value of the coefficient of drag (CD) in the equation is a little more complicated to determine because the Wrights did not directly measure CD in their wind tunnel tests conducted November 22 through December 7, 1901. Instead, they measured the drag/lift ratio (CD/CL) from which the value of CD can be derived.

The Wrights measured the coefficient of lift (CL) as 0.515 and the drag/lift ratio (CD/CL) as 0.105 in their wind tunnel tests using airfoil #12 and an angle of attack of 5 degrees. 

The geometry of airfoil #12 closely resembles the geometry of the wings on the 1903 Flyer. The angle of attack of 5 degrees approximates the angle of attack of the Flyer.

The coefficient of drag is calculated in the following manner:
CD = CL x CD/CL = 0.515 x 0.105 = 0.054

Substituting the appropriate values in the equation for drag:
D = (0.0033) x (512) x (30.8)² x (0.054) = 86.6 pounds

Total Drag

The drag of 86.6 pounds is for the drag attributed to the wings. To determine the total drag of the Flyer, the drag attributed to the wings (D) must be added to the drag generated by the frontal surface area of the airplane (Df). 

The Wrights purposely assumed the horizontal position on the wing while piloting their machine to reduce drag. They estimated that the remaining frontal surface area of the Flyer was 20 square feet. Substituting this value in the drag equation:

Df = (0.0033) x (20) x (30.8)² x (0.054) = 3.4 pounds

The total drag (Dt) is therefore:

Dt = D + Df = 86.6 + 3.4 = 90 pounds

On November 23, 1903 from Kitty Hawk, Orville wrote Charles Taylor, their employee who built the engine following the design of the Wrights:

"After a few minutes to get adjustments, and to burn out the surplus oil, the engine speeded the propellers up to 351 rev. per min. with a thrust of 132 pounds. Stock went up like a sky rocket, and is now at the highest figure in its history. We have made some allowance at nearly every point in our calculations, so that with the increase of weight we expect to be a little over 90 pounds, but of course that is coming down to our closest figures."

Power

Power is force times speed. The power required to overcome drag can now be found by multiplying total drag by velocity:

P = Dt x V = 90 x 30.8 = 2772 pound-miles/hour
Converting this number to horsepower, the power is 7.3

The engine for the 1903 Wright Flyer produced about 12 horsepower. It would reach 16 hp when started, but drop off to 12 hp after a few seconds. While the horsepower of the engine (12) appears to be sufficient to overcome the drag (7.3), there will be additional loss of horsepower attributed to the chain drives that transmit the power from the engine to the propellers. Also, there will be loss of power attributed to the propellers. The propellers had an efficiency of 66%.

The Wrights knew it was going to be a close call. On November 15, Orville wrote home to his father and sister:

"Mr. Chanute says that no one before has ever tried to build a machine on such close margins as we have done to our calculations." (Octave Chanute was a friend and an aviation historian and experimenter.) 

The question as to whether they had sufficient power was answered on that fateful day in December. They made four flights on the 17th, the longest flight going 852 feet.

The following year back in Dayton, they were not so fortunate even though they had more horsepower. The 1904 Flyer had trouble getting off the ground. Dayton didn't have the wind of Kitty Hawk and the air pressure was less because of the higher elevation. 

The 1904 Flyer was little changed from the Kitty Hawk Flyer although they did improve the engine so that it produced 15-16 hp. Wilbur wrote to Chanute on August 8, 1904:

"We have found great difficulty in getting sufficient initial velocity to get real starts. While the new machine lifts at a speed of about 23 miles, it is only after the speed reaches 27 or 28 miles that the resistance falls below the thrust."

They solved the problem by employing a catapult launch system to give the Flyer a boost on takeoff.

The initial Wright engines were crude, but they did the job. They didn't need a lot of horsepower because the Wrights had designed an efficient aerodynamic flying machine. 

In contrast, Dr. Samuel Langley, Director of the Smithsonian Institution, employed a sophisticated engine that generated a whopping 50 hp, but his Aerodrome was poorly designed. It crashed on takeoff nine days before the Wright's successful first flight.

Propeller Design Demonstrates the Genius of the Wright Brothers

The immediate impression of the Wright brothers is that they were just two bicycle mechanics from Dayton, Ohio who invented the first successful airplane. Maybe they were just lucky and stumbled on the solution through trial and error because this was a feat that had eluded the best minds for thousands of years.

After all, the brothers didn't have a scientific degree or any formal education beyond high school. But don't let that fool you. The reality is that they were brilliant scientists that outperformed the scientific elite of the day in the use of the modern scientific process.

The Airplane Propeller 

An example of their prowess is their approach to the solution of an intractable engineering problem associated with their invention of a deceptively simple item, the airplane propeller.

In 1902, after their third trip to Kitty Hawk, they were confident that their glider would fly under pilot control. The next task was to develop a mode of propulsion.

They proceeded to design and build a small gasoline engine weighing 180 pounds that produced 12-horsepower. Now, they needed a propeller to go with it.

That seemed easy enough. Propellers have been used for years on ships. The respected scientist Samuel Langley, the Secretary of the Smithsonian had written in Experiments in Aerodynamics, "there is considerable analogy between the best form of aerial and of marine propellers." 

The Wrights initially thought they could convert the design information on ship propellers to flight technology. "We had thought we could adopt the theory from marine engineers, and then by using our tables of air pressures, instead of the tables of water pressures used in their calculations, that we could estimate in advance the performance of the propellers we could use." 

A trip to the Dayton Public Library quickly disillusioned them of the notion that this was going to be an easy task. Their research found there was no empirical information on how to do this and they didn't have the time to use the trial-and-error approach used by marine engineers (the Wrights called it "cut and try"). They decided to develop new theory and design the propellers from scratch.

Their usual approach to solving complex problems was to first think about the problem and mentally develop a testable theory. Often, the brothers brainstormed ideas by vigorously debating ideas. Often these debates turned into shouting matches that were annoying to their sister, Katharine. Sometimes they would convince each other of the other's argument and change sides to argue the opposite point of view.

Propellers as Rotating Wings

Out of this process came the insight that propellers acted like rotating wings traveling in a spiral course through the air. The rotating propeller blades act as airfoils that produce a pressure differential. Less pressure is created on the front of the spinning cambered blade than there is on the back, thus the rotating blade produces thrust that moves the airplane forward.

Now that they had the concept, the problem became how to calculate the thrust of a rotating blade. The blade must produce sufficient thrust to propel the airplane off the ground and sustain it in the air. Flight would not be possible if sufficient thrust couldn't be generated to overcome drag.

The problem was difficult. Orville describes it best in a December 13 issue of Flying Magazine, "It is hard to find even a point from which to make a start; for nothing about a propeller, or the medium in which it acts, stands still for a moment. The thrust depends upon the speed and the angle at which the blade strikes the air; the angle at which the blade strikes the air depends upon the speed at which the propeller is turning, the speed the machine is traveling forward, and the speed at which the air is slipping backward; the slip of the air backward depends upon the thrust exerted by the propeller, and the amount of air acted upon. When any of these changes, it changes all the rest, as they are all interdependent upon one another."

The Wrights did have one advantage. They had data from their wind tunnel experiments in which they had tested some 200 airfoils (wing shapes). They selected airfoil number 9 as their baseline because it showed the best efficiency under a variety of conditions.

The brothers developed a series of quadratic equations from which they designed the propeller. All this work was accomplished before the advent of computers. Based on their calculations, they used hatchets and drawknives to carefully carve a piece of wood into an eight-foot propeller with a helicoidal twist based on airfoil number 9.

After three months of effort, they tested their propeller in their bicycle shop using a two-horsepower motor with excellent results. The thrust achieved was found to be within 1% of what they had calculated --- a truly amazing result.

Orville gleefully wrote to George Spratt, "Isn't it astonishing that all these secrets have been preserved for so many years just so that we could discover them."

Success

In June, they designed and made two propellers to be used on their machine, the Flyer. They determined that they could achieve greater thrust with two propellers rotating slowly, than they could with one propeller rotating faster.

Orville wrote, "all the propellers built heretofore are all wrong." 

Each propeller was 8.5 feet in diameter and made of three 1 1/8 inch thick laminations of spruce with the wing tip covered with light duck canvas glued on to prevent the wood from splitting. The entire propeller was then coated with aluminum paint.

The propellers were connected to the engine through a chain, gear and sprocket system, similar to a bicycle design. The propellers rotated 8 revolutions for every 23 revolutions of the engine. The two propellers were designed to provide a combined thrust of 90 pounds at airspeed of 24 mph and turning at 330 rpm. 

The linkage was designed to rotate the propellers in opposite directions so as to counteract the torque effect of each rotating blade. This was achieved by crossing one set of chains in a figure eight and encasing the chains in medal tubes to keep them from flapping. The chains were procured from the Diamond Chain Company of Indianapolis.

The propellers were mounted at the rear of the wings as "pushers" to eliminate the effect of turbulent airflow upon the wings. 

The finished product produced a maximum efficiency of 66% (Some recent tests achieved 70%). That means that 66% of the horsepower of the small motor was converted by the propellers into thrust. This was far superior to any other inventors who were attempting to fly with engines of much greater horsepower and still couldn't sustain flight.

On December 17, 1903, the little engine with the efficient propellers pulled Orville off the launching rail and into the air producing the first heavier than air flight in the history of mankind.

Their remarkable achievement demonstrates the genius of the Wright Brothers and places them within the ranks of the greatest inventors in history.

Final Notes

An exact reproduction of the 1903 Flyer is scheduled to fly at Kitty Hawk on December 17, 2003 to celebrate the centennial anniversary of the first flight. The Wright Experience of Warrenton, Va., headed by Ken Hyde, is researching and building the Flyer.

Larry Parks, a volunteer working for Wright Experience, is carving the propellers using mainly antique tools. A member of the Wright family has provided an original 1904 propeller to aid in the project.

The Wrights continued to improve their propellers after 1903. One of the more interesting improvements was the so-called "bent end" propeller introduced in 1905. The purpose of the design was to prevent twisting under pressure.

Ken Hyde had one of their remanufactured 1911 bent end propellers that was used on Wright Model B airplane tested at the Langley Full Scale Wind Tunnel. It achieved an efficiency of 77% operating at a flying speed of 40 mph.

Hyde commented, "The performance of our remanufactured Wright propeller was amazing, when you consider that today's wood propellers are only 85% efficient." 

 

It's All About Control

The greatest contribution the Wright Brothers made to man-flight was figuring out how to control an airplane in flight.

Their experience with bicycles taught them the importance of control. A bicycle is an inherently unstable machine. One must learn how to actively control a bicycle in order to ride it.

The airplane is also an unstable machine. Early experimenters tried to control an airplane by swinging their bodies from side to side, or by trying to build into the machine a means of automatically adjusting for fluctuations. Neither worked satisfactorily. 

Basics of Control 

The Wrights took a different approach to the problem of control. They designed a way to achieve active control in flight by controlling the movements of an airplane in the three basic movements of pitch, yaw and roll. In this way a person could learn to pilot an airplane in the same way a bicycle rider could learn to ride a bicycle.

Pitch movement occurs when the nose moves up and down around a horizontal axis.
Yaw movement occurs when an airplane veers side to side around a vertical axis.
Roll movement occurs when the wings dip to one side or the other around a horizontal axis.

Early experimenters were aware of the need for control of yaw and pitch. Balloonists thought of using a rudder for steering and an elevator for controlling altitude. The English engineer, George Cayley, in the early 1800s designed a tail that combined a vertical rudder with a horizontal elevator in a configuration called a cruciform design.

This design would allow a pilot to make adjustments in altitude and when changing direction. Lateral stability (roll) would be built into the machine by some means unspecified. A slow flat turn would be used to change direction.

The Wrights saw that there was a significant limitation with this approach. The problem of control was three dimensional, not two-dimensional. The neglected roll dimension was the critical oversight.

The Wrights, again using the bicycle model, saw the solution to mastering lateral control and for turning, was for the pilot to roll the airplane by twisting the wings in a process that they called wing warping. When one of the trailing edges of the wing are twisted up, the trailing edges on the opposite side twisted down. Wilbur got the idea of twisting the wings from observing how birds fly. 

In 1899, Wilbur tested the idea in Dayton by building a five-foot, bi-wing kite. He attached cords to each corner in such a way that he could twist the wings in flight. It worked so well in controlling the kite's balance that he and Orville decided to build and test a flyable glider.

Year 1900

The following year, 1900, the Wrights journeyed to Kitty Hawk for the first time with a glider that was essentially a kite with 17-foot wings that was three times larger than the previous years kite.

The glider had no tail and the wing tips were untrussed to permit twisting. The most prominent feature was an elevator set in front (canard configuration), a feature that was a trademark of all Wright airplanes for many years.

The setting of the elevator in front was a conscious decision to assure effective pitch control. They wanted to make sure that they wouldn't duplicate the uncontrollable dive that had killed the famous glider experimenter, Otto Lilienthal in 1896.

Most people at Kitty Hawk thought they were highly eccentric flying a glider dressed as the middleclass did.

They measured wind speed, lift with a spring scale attached to the line, and the angle of attack.

They were disappointed that the cambered wings didn't create the lift they expected, but they were pleased that the elevator and the wing warping worked effectively in controlling pitch and lateral balance. They tried tossing the glider forwards and backwards off the dunes in order to improve performance.

They were pleased that Wilbur was able to glide 300 to 400 feet for a total of 2 minutes flying time. This was as good as Chanute and Lilienthal had done.

Perhaps more important Orville became committed to the project and Wilbur began using the pronoun "we" in his correspondence.


Year 1901

They returned for the second time to Kitty Hawk.  They were delayed by storms and harassed by mosquitoes. They built a primitive building which made life better than living in a tent as they had done the previous year. Spratt and Huffaker joined them at the request of Chanute.

They came with a much larger glider. The area of the wings was almost doubled and the camber was increased.

It wasn't long before they found they were having control problems. On one glide, the glider climbed steeply and then lost all headway. It took Wilbur's skillful piloting to keep from nose diving into the ground. They thought they had solved the control problem, but now the glider had a tendency to nose-dive or climb suddenly and go into a stall. On occasion it would even start to go backward, a frightening development.

They reduced the camber of the wings and that seemed to solve the problem. With new confidence Wilbur tried to make some turns, but then a new problem materialized.

Sometimes when making a turn, the lower wing slowed and approached a stall. The higher wing, because it was still producing lift, would whip around causing the glider to go into a spin. On one flight the condition caused Wilbur to crash, hurling him off the wing into the elevator blackening his eye and bruising his nose.

Although the wing was much larger than the one that they used the previous year, the lift was much less. They reconfigured the wing to reduce the camber of the wings from 1:12 to 1:19. But that didn't improve performance significantly.

Discouraged, the Wrights returned home. Not only did they not solve the problem of inadequate lift; they hadn't solved the control problem. 

Year 1902 

The Wrights returned in 1902 with a similar configured machine as the previous year but with a number of important design changes. As a result of their wind tunnel tests the wings were now longer, narrower and had less camber. The objective of these tests was to determine the wing shape that would generate the most lift for the least drag.

In the course of 2 months the Wrights had redefined aeronautics for the next century. 

The control system was also redesigned to operate differently. The wing warping that had previously been operated by the feet was now operated by the pilot's hip movements while lying in a cradle on the wing.

A tail was added for the first time as a means to prevent the spins that had occurred the previous year. The tail consisted of two rigidly mounted vertical fins.

They soon found out that the spin problem had not gone away. The message was forcefully communicated to Orville when he crashed into a sand dune, demolishing the glider but somehow emerging unharmed.

At first they thought it was just pilot error. But every so often when attempting to turn, the low wing would drop even lower and the glider would slide into a spinning fall. They gave it the name of "well digging."

Now they focused on the design of the tail. They removed one of the two fins, but that made no difference. Finally, Orville solved the problem.

The rigid tail aggravated the control difficulty by causing the lowered wing to lose still more speed at the same time that the raised wing continued to rise and move forward. Orville correctly reasoned that if the tail was made movable, the pilot could adjust it to minimize wind resistance and thereby restore the glider to normal flight.

Wilbur liked the idea and added an improvement that linked the tail to the wind warping mechanism so that the tail moved in synchronization with the wing warping. It worked. Taking turns, the brothers set new gliding records while making hundreds of glides over a two-week period. They had built the world's first practical glider. The performance of the glider exceeded their expectations. They were making extended glides of over 600 feet. The glider was pure elegance.

Their idea for the control of both roll and yaw motions was the basis for their patent submitted in 1902 and granted in 1906.

Year 1903

The Wrights returned to Kitty Hawk in 1903 with high expectations and a powered machine which incorporated what they had learned from their experiments. Their engine was crude but light and had 12 horsepower. They had calculated that that was sufficient to get airborne.

Wilbur won the coin toss to be the first to make the attempt to fly on Dec. 13th. The machine, nicknamed the Flyer by their father, was placed on the slope of Kill Devil Hill because of light wind. 

It leaped off the starting rail and shot up 15 feet in the air. There it stalled and plowed into the sand 105 feet and three and one-half seconds from the point of takeoff. The left wing, the front elevator and one of the skids were slightly damaged.

The poor result was not surprising in view of the fact that Wilbur had not practiced with the machine as a glider before attempting the first powered flight. However, Wilbur's control problem on his initial flight was a symptom of the Flyer's worst problem. It had a very unstable pitching characteristic and its lateral characteristics were also poor.

The good news was that operation of the elevator prevented a dangerous nosedive into the ground and the engine was powerful enough to get the Flyer off the ground.

Three days later they were ready to try again. They could have tried on the 16th but they had promised their father not to fly on Sunday.  They were ready the next day.

They alternated with each other, flying four times, the longest being 852 feet in 59 seconds. They had trouble maintaining pitch control resulting in undulating flight paths, but the important thing is they had done it. Man had flown for the first time. It was an extraordinary achievement and they had accomplished it in only five years of effort.

Several reasons are given for the pitch control problem.

  1. The elevator was balanced so near its center. Once it started to turn, it continued the movement of its own accord. The result was that it tended to keep going from one extreme to the other.
  2. The design of the wings. The wings were thin and highly cambered. The design had excellent lift to drag characteristics, but poor pitch stability. Less camber would have improved the wing's stability.
  3. The elevator was placed to close to the body of the airplane. 

Fortunately these problems were somewhat ameliorated by the slow flying speed of the 1903 flights and the Wrights' superior flying skills.

The Wrights were well aware that the success of the Flyer I was an intermediate success. It was an experimental plane built and flown to test basic principles of aerodynamics and control. There was still much to be done before they could say they had achieved a practical airplane.

Wind tunnel tests were conducted at Langley of the full-scale reproduction of the 1903 Wright Flyer built by the Wright Experience (Ken Hyde) of Warrenton, Va. These tests provide a definitive database establishing the aerodynamic characteristics of the design. The test results confirm that the aircraft was highly unstable in pitch, with marginal lateral/directional stability. Also, the Flyer behaves in a highly non-linear manner due to premature stall of the canard and vertical rudders.

Year 1904

The Wrights returned to Dayton to build and test an improved version of the Flyer at Huffman Prairie, a cow pasture outside Dayton. Flyer II was heavier, structurally stronger and had a more efficient engine. The spars were made of white pine instead of spruce that  was used in the 1903 machine. The camber of the wings was reduced to 1/25 from 1/20 and the elevator control was relocated for easier handling.

They soon became comfortable with their ability to balance Flyer II in straight flight and were now ready to learn how to turn. They succeeded in making the first turn on September 26. Then, when Orville was turning on October 15, he had trouble stopping the turn and crashed the machine, causing serious damage.

The Wrights diagnosed the problem as the anhedral shape of  the wings. An anhedral shape is one in which the wing tips are lower than the body of the airplane. The 1903 Flyer also had been rigged for the anhedral with the wings tips arched about eleven inches below the centerline.

So had the 1900, 1901 gliders, and later during the 1902 flying season, the 1902 glider used the anhedral. The Wrights chose the anhedral so as to dampen the effect of crosswinds and to improve the effectiveness of wing warping.

They could have chosen the dihedral configuration. Some birds, such as buzzards, employ the dihedral angle. Its works well to maintain stability in calm air, but the wing's "V" shape becomes unstable with strong crosswinds. 

The Wrights found that the anhedral exhibits serious negative effects while turning. They discovered that when executing a turn, a crosswind increases pressure on top of the lower wing. The increased pressure forces the wing to continue to drop, creating a spin.

Removing the anhedral of Flyer III resulted in much better performance, but every once in awhile a mysterious tendency to go into a spiral returned. They were still working on the problem as the year ended.

Year 1905

The Wrights correctly concluded that the tendency to spin while turning was a control problem associated with the tail. Starting with the 1902 glider, they had interconnected the movements of the tail to wing warping so that they would move simultaneously. This worked well in 1902 and 1903, but control of the new machines was more complicated than could be handled by using hardwired proportional interconnection.

They disconnected the tie between the two to allow for independent control of the tail by the pilot. This solved the spin problem.

Other changes were made to improve pitch stability. The area of the canard was enlarged and additional weight was added to the front-end. The latter change was for the purpose improving stability by moving the "center of gravity" of the machine forward.

Other changes were:

The wood used for the spars was changed back to spruce.

The camber of the wings were returned to 1/20 after having been changed to 1/25 and 1/30 in 1904.

They added a pair of semicircular vanes they called "blinkers," placed between the twin elevator surfaces to prevent sideslips they experienced in 1904.

They added tabs, they called "little jokers," to the trailing edges of the propellers to prevent deformation.

They added oiling and feeding devices to the engine to allow longer run time.

The entire machine was slightly longer and taller than before.

Then another problem developed. One day Orville was circling a honey-locust tree at Huffman Prairie. He was turning, when suddenly the machine turned up on one wing and slide sideways toward the tree. The left wing struck the tree twelve feet above the ground. Luckily, the machine continued through the branches, slicing off some of them, and managed to land safety.

Wilbur diagnosed this problem and its' solution. Centrifugal force was culprit. Tilting the nose of the machine down a bit to restore flying speed would counteract this force. It worked. They had solved their last serious problem.

The Flyer III could now be flown with ease. On October 5, Bishop Milton Wright wrote in his diary, "In the afternoon, I saw Wilbur fly 24 miles in 38 minutes and 4 seconds." Their father had watched Wilbur circle Huffman Prairie about 30 times, stopped only by running low on gas. 

Orville and Wilbur had developed the world's first practical airplane. It would be many years before anyone could duplicate the Wrights' remarkable achievement. 

Wright Brothers Get a Lift

A hundred years ago (1901) the Wright Brothers were disappointed with the performance of their glider at Kitty Hawk. This glider had bigger wings containing more than double the area than the one they had flown a year before. They were expecting much better results. Instead they found a significant lack in lifting power.

Wilbur and Orville suspected that the aeronautical data that they had used in their calculations for lift were erroneous. The famous glider pioneer, Otto Lilienthal, considered as the most important aeronautical experimenter of the nineteenth century, had developed the data. The brothers decided to find out for themselves the validity of the data by building a wind tunnel and generating their own data.

Why Airplanes Fly

Gliders and airplanes need to produce an upward force called lift that overcomes weight created by gravity in order to fly.

Lift is created by the flow of air over a wing. In general there are two concepts of physics involved. One is Bernoulli's Theorem developed by Daniel Bernoulli, an eighteenth century scientist. He discovered that as the velocity of a fluid (such as air) increases, its pressure decreases. 

In the case of an airplane, the wing is shaped to force the air flowing over the upper surface of the wing to flow faster than the air flowing over the lower surface. The faster air on the top surface creates a pressure differential resulting in an upward force on the wing.

Another contribution to lift comes from the effect of Newton's third law. Isaac Newton has been regarded for over 300 years as the founding exemplar of modern physical science. Newton's Third Law states that for every action there is an equal and opposite reaction. 

As air passes over a wing, it is bent down. The bending of the air creates a downward force whose opposite equal force creates lift.

Determinants of Lift

There are a number of variables associated with creating and measuring lift. These include the size of the wing, the velocity of the air flowing over the wing, the density of the surrounding air, the shape of the wing and the angle of attack. 

Area: All other things being equal, the larger the area of the wing, the more lift that will be created.

Wing Velocity: The higher the velocity the greater the lift. When an airplane is taking off, it normally heads into the wind because that increases the relative wind speed over the wings and helps the airplane reach flying speed.

Air Density: Air density refers to the amount of air contained in a given volume. Air density varies with the air's temperature and pressure. 

Decrease temperature and density increases. Increase pressure and density increases. Air is denser at sea level than it is at higher elevations.

The denser the air, the greater the lift. The air pressure at Kitty Hawk, being at sea level, is denser than the air at Dayton, Ohio. The temperature at Kitty Hawk on the day of the first flight was a cold 34 degrees. The Kitty Hawk Flyer may not have gotten off the ground in Dayton's less dense air.

Coefficient of Lift: The coefficient is a multiplying factor that takes into consideration the various angles a wing assumes with regard to the flow of air. The value of the coefficient varies with the size of the wing and the "angle of attack." 

The angle of attack is the angle of the wing with relation to the wind flow. Raising and lowering the nose of an airplane while flying varies the angle of attack. Within limits, a greater angle of attack results in greater lift.

Raising the nose to an extreme angle of attack can result in loss of efficient airflow over the wing and result in loss of lift. This is called a stall and is a potentially dangerous condition. 

Lilienthal is one of a number of early experimenters that were killed when their gliders went into a stall condition. While gliding in 1896 at an elevation of 50 feet, a gust of wind caught his glider causing it to nose up sharply. He was not able to correct the problem by shifting his weight and crashed. That accident was fatal for Lilienthal who received a broken spin.

Lilienthal in the Pocket Book of Aeronautics published a table containing coefficients of lift in 1895. They later appeared in The Aeronautical Annual and other sources available to the Wrights.

Smeaton's Coefficient: Also involved in the calculation of lift at the time of the Wright Brothers was a constant number known as the "coefficient of air pressure." It is a multiplying factor used to calculate the numerical value of lift in air, as compared to other mediums, such as water or oil. 

John Smeaton, a mideighteenth century engineer, had determined the value of this coefficient was 0.005 in 1759, from his study of windmills. Engineers used the value of 0.005 for 150 years. The Wrights would subsequently find that this number was the major cause of their lift problem with their early gliders.

Modern aeronautical engineers no longer use Smeaton's coefficient. Many have never even heard of it.

Camber: A barn door can fly, but not very well. A wing with a cambered shape is more efficient; that is, one that has a degree of curvature of the upper surface.

The Wrights tested over 200 airfoils to find the optimum shape in a 6-foot pioneering wing tunnel they designed and built. Airfoil number 12 was found to be the most efficient and was the model for the wing used on their successful first flight in 1903.

The Wind Tunnel

The Wright Brothers did not invent the wind tunnel, but they were the first to use it for scientific aeronautical research directly related to the design and construction of an airplane. There were ten wind tunnels in the world at the time and the Wrights was the third in the U.S.

Their wind tunnel was not elegant; at a glance it looked like a coffin. But it was in fact an elegant scientific instrument that would set the standard for conducting aeronautical research up to the present time.

The tunnel was a simple wooden box six feet long and sixteen inches square. It had a glass window in the top for viewing the measuring instrument they had designed. A one horsepower engine they used in their shop drove a fan that generated a wind of thirty miles per hour. It turned out that the wind generated in the wind tunnel was almost the same as the wind the Wright Flyer faced at Kitty Hawk on the first successful flight (27-mph).

They fitted a honeycomb grid on the fan end of the tunnel, which produced a perfectly straight current of wind required for accurate measurements. This gave them their biggest problem and took them a month to solve. 

Their engineering expertise was demonstrated in the instrument that they devised to measure lift. It consisted of an ingenious mechanical balance device in which the test wing foil was compared to flat plates placed perpendicular to the wind flow. The coefficient of lift could be read directly from the instrument.

The completed wind tunnel was capable of testing a wide range of shapes and curvatures to an accuracy of 2-3%. Lilienthal, in contrast, tested and published data on only one specific curvature.

Found a Significant Error

The wind tunnel tests conducted by the Wrights proved that Smeaton's coefficient of air pressure was in error. The Wrights' discovered that the correct average value for this coefficient was 0.0033 rather than Smeaton's 0.005 they had used in designing the 1900 and 1901 gliders. This error was the primary cause of their poor performance. Using the Smeaton value of 0.005 had caused them to overestimate the force of lift in their design by 40%.

They also found an error in Lillenthal's lift coefficients, but it was a minor error within the angles of attack they would be flying. There was close coincidental correlation between the Wrights' and Lilienthal's coefficients between five and eight degrees of attack.

The Wrights had for the first time in history established a scientific basis for designing an airplane that would perform in accordance with prior calculations. Previous experimenters had relied on guesswork using trial and error. The Wrights relied on facts and figures. They now knew how to design a wing in which they could have confidence that it would fly.

On December 7, 1901, their sister Katharine wrote to their father:

"…The boys have finished their tables of the action of the wind on various surfaces, or rather they have finished their experiments. As soon as the results are put in tables, they will begin work for next season's bicycles …"

New Design

In 1902, the year that "animal crackers" were introduced to America's children, they returned to Kitty Hawk with a new glider. Its design incorporated all their wind tunnel data. The wingspan was now 32 feet, ten feet longer than the 1901 glider with a longer and narrower shape with a camber of 1 to 20.

The wing area of 305 square feet was only slightly bigger than the 290 square feet of their previous year's glider, yet it generated much greater lift.

Their experiments enabled them to select a new wing shape with an efficient lift-to-drag ratio. Drag refers to the resistance that the wing generates as it flows through the air. The most efficient wings are those that generate the least drag for the most lift.

Their data demonstrated that longer, narrower wings in general produce more lift than the same area contained in short, wide ones.

Their data also showed that a parabolic wing camber with the high point toward the front was more efficient than the perfect arcs that Lilienthal and others had used.

The camber they used on the 1902 glider was a relatively flat 1 in 24 to 1 in 30 depending upon how the wing was rigged. This specific wing configuration was never actually tested in their wind tunnel. They apparently extrapolated this configuration from their other data.

All of the above were new and original conclusions resulting from their wind tunnel experiments. The Wrights' were now far ahead of anyone else in the aeronautical field.

World Record Flights

They flew their new glider somewhere between 700 and 1,000 times during their five weeks of experimenting at Kitty Hawk. On October 23, Wilbur sailed 622 1/2 feet in 26 seconds setting new American records.

"We now hold all the records! The largest machine we handled in any kind of weather, made the longest glide, the longest time in the air, the smallest angle of descent and the highest!!!"

They were now convinced that the data they had found from their wind tunnel tests would enable them to calculate in advance the performance of their first powered airplane. They had mastered two of the three conditions of flight. They had designed wings capable of sustaining flight and developed a three-axis control system that allowed maintaining balance and executing turns. The next step was to develop an engine and propeller. 

Calculation of lift for the 1903 Kitty Hawk Flyer

The formula used to calculate lift is as follows:

L = kxV²xSxCL where 

L = Lift (pounds)
k = Smeaton's coefficient
V = Relative Velocity of air over wing (mph)
S = Wing area (square feet)
CL = Coefficient of lift

k = 0.0033 (from Wrights' wind tunnel experiments)

V = 33.8 (wind of 27 mph on December 17, 1903 plus ground speed of Flyer of 6.8 mph)

S = 512 (wing area of 1903 Flyer)

CL = 0.515 (from Wrights' table of lift coefficients assuming airfoil #12 and an angle of attack of 5 degrees)

Substituting the approximate values for the 1903 Wright Flyer on the first flight:

L = (0.0033) x (33.8)² x (512) x (0.515) = 994 pounds

The weight of the Flyer, including engine was 605 pounds. Orville weighed approximately 145 pounds. Therefore, the total weight of machine plus pilot is 750 pounds

Since lift (994 pounds) is greater than the weight of the machine (750 pounds), the lift was sufficient to support flight.

 

Inventing Flight on a Shoestring

The Wright Brothers would never have won the race to fly a power-driven airplane if success had depended on money. While their American and European competition depended on large amounts of money contributed by government or other benefactors, the Wright Brothers relied solely on their own modest financial resources.

Frugal Brothers

During the five years of experiments from 1899 to 1903 the Wright Brothers, without any outside financial support, spent a grand total of under $1200.00. Their expenses included the construction of a large kite, three gliders, and one power-driven airplane. The money also covered the expenses of four extended trips to Kitty Hawk.

Their record of expenses includes such things as $5.50 for books on aviation in June 1899, train tickets to North Carolina for $22.50, $25 to build the 1900 glider and a $15 fee to the U.S. Patent Office in 1903.

Langley Fails

In contrast, their biggest competitor, Samuel Pierpont Langley, Director of the Smithsonian Institution, was awarded a $50,000 contract by the U.S. War Department, supplemented by a $20,000 grant from the Smithsonian, to build a power-driven airplane. Langley's airplane failed dismally. It twice crashed into the Potomac River after being catapulted from a houseboat. The last failed attempt occurred only nine days before the first successful flight by the Wright Brothers. One reporter said Langley's Aerodrome had the flying characteristics of a "handful of mortar." The failure was bitterly disappointing to Langley who had devoted 17 years of his life to the development of an airplane. It had taken the Wrights only three and a half years of work to the first flight.

Wright Cycle Company

The Wrights financed their flight ambitions from the modest profits of their small business. The introduction of the safety bicycle (two wheels of the same size) had launched an industry that was experiencing phenomenal growth. In 1892, the brothers saw the opportunity to start a bicycle shop, the Wright Cycle Company, to supplement their printing business. It wasn't long before the prospering cycle shop was their primary business selling brand name bicycles, parts, accessories and repairs.

Starting in 1896, they decided to manufacture their own brand of bicycles. The top of the line was the Van Cleve. This model initially sold for $60 to $65. By 1901 it was selling for $39.50. They also sold a lower-priced model, the St. Clair. It initially sold for $42.50. In addition, they sold bike tires for $3 and inner tubes for $1.25. These prices seem low by today's standards, but in 1900 the average annual wage of a worker was only $440. 

They hand-built their cycles to customer order to insure the highest quality. They contained a unique oil-retaining hub and coaster brake of their own design. Every bike was brush painted with five coats of paint.

The Wrights' income was around $2,000 to $3,000 a year, most of which resulted from their bicycle business.

The Wright Brothers learned to be frugal from their boyhood years. Their family, while not poor, wasn't flush in money either. Their father was a church Bishop and their mother stayed home to raise five children. The boys were required to earn their spending money. They collected scrap iron, organized their own circus, made their own toys, built and sold kites and built their own printing press.

Inventing on a Shoestring

Being frugal was an asset in solving the problem of flight. They had to use their brains to find a solution since they couldn't afford the "trial and error" approach. They had a low threshold for guesswork. Instead, they were avid practitioners of the scientific approach that they used to cut to the heart of problems. They developed their own theories and meticulous calculations and applied them to design, build and test their ideas using low cost kites and gliders. 

They developed the 3-axis control system of flight, made small airfoils out of hacksaw blades and tested them in a wing tunnel they designed and built in order to determine the proper shape of a wing to provide optimum lift. 

They designed the airplane, weighing 605 pounds, of lightweight materials enabling them use a small gasoline engine. With the help of their only employee, Charlie Taylor, they designed and built a 170-pound engine with accessories that produced 12 horsepower.

They developed original theory of airplane propeller design and hand made them to deliver optimum thrust effectively and efficiently.

Langley's engine could develop 52 horsepower but his Aerodrome was unstable, uncontrollable and underpowered.

Price Inflation 

In preparation for the 100th anniversary of the first flight on December 17, 2003, a reproduction of the Wright Flyer is currently being built to fly at Kitty Hawk on the anniversary. It is estimated that the cost of the reproduction will exceed $2-million.

As I am writing this article, there are new airframe components for a Wright Brothers' airplane for sale on Ebay. First bid is for $25,000.

The Wright Brothers accomplishment was probably the greatest bargain in the history of mankind. 

 
 

 

 
 

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