The Wright Paradigm

by Dr. Richard Stimson

in Inventing The Airplane

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

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