Wright Brothers – Invention Of The Airplane

Articles relating to the Wright Brothers’ invention of the airplane.

A Beautiful Body

by Dr. Richard Stimson

in Inventing The Airplane

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 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 1/2-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.

The Power to Fly

by Dr. Richard Stimson

in Inventing The Airplane

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.

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

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.”