Smeaton's Coefficient:
The Little Number with a Big Difference
“If I have seen further it is by standing on the shoulders of Giants--Isaac Newton
"There is not a discovery in science, however revolutionary, however sparkling with insight, that does not arise out of what went before."--Isaac Asimov
In 1896, with Alexander Graham Bell looking on, Samuel Pierpont Langley's steam powered, model "aerodrome" successfully flew 3/4 of a mile. Launched again, it flew once more, nearly as far as the first time.
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| Quantico, Virginia, 1896. The successful flight of Professor Samuel Langley's unmanned model-- six years before the Wrights' claimed manned flight of 1903 |
" I was myself a witness of the memorable experiments made by Professor Langley on the 6th of May, 1896, with his large-sized model which had a spread of wing of about 14 feet. No one who witnessed the extraordinary spectacle of a steam-engine flying with wings in the air , like a great soaring bird, could doubt for one moment the practicability of mechanical flight. I was fortunate in securing a photograph of this machine in full flight in the air, so that an automatic record of the achievement exists...." Dr. Alexander Graham Bell
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But with the exception of Otto Lilienthal, the Wright brothers gave little or no credit to the aviation pioneers, such as Samuel Pierpont Langley, whose genius, innovation, research, hard work, and sometimes lives brought aviation to the point where man could take off into the skies. They gave virtually no credit to their contemporaries who helped them.The Wrights dismissed most of them as failures.
The Wrights took the credit for themselves. They claimed that it was with their own research that they built the first heavier than air, manned, powered plane capable of flying. They went so far as to say that they had invented the airplane. Their assertions were trumpeted in the courts, in the press, and in their documents.
Whether the Wrights were really even first to fly may be debated for some time longer. It's not at all likely they were. There is much more evidence in the form of valid witnesses, for example, that aviators, such as Gustave Whitehead, preceded them. See previous posts. When the Wrights really flew is another point that should also be on the debate table. The only so called "proof" we have is their word and only theirs, that they took off from "level ground" in 1903 "with engine power alone." All other evidence, including witnesses so far, points to the fact that they needed the assistance of the hill to take off. The alleged photograph that appeared in 1908 is highly questionable. Compounding the evidence is the fact that the next year at Huffman Prairie near Dayton, Ohio, the Wrights increased the horsepower of their new flyer's engine over that of the Flyer I, but couldn't reliably get off the level ground there. Without the hills near Kitty Hawk, their take offs in Dayton needed the assistance of a catapult and in addition to that, a headwind. As late as 1908, they were still relying on their catapult, whereas Glenn Curtiss and Alberto Santos Dumont were already taking off from level ground with wheels and the power of their engines.
The story the Wrights told about their trips to Kitty Hawk is retold in many books and accounts. A quick read of the legend can be found at the Smithsonian site titled, "The Wright Brothers, The Invention of the Aerial Age." But the Smithsonian assertions about the Wrights' inventions, research, and discoveries are more than questionable.
Some serious digging will show that two of the aviation pioneers whose research benefited the Wrights were Octave Chanute and Professor Samuel Langley, contrary to what the Wrights said and their historians, such as Fred Howard in "Wilbur and Orville," have repeated.
In 1901, as the story goes, Orville and Wilbur returned to Kitty Hawk with a new, larger glider from the one the year before. They also had visitors that season, Dr. George Spratt and Edward C. Huffaker, who came at the suggestion of Chanute. Note that the Smithsonian website doesn't mention their presence that year, but it's very important to the history. Please see future posts.
The tests with the new glider were so disappointing that the Wrights considered dropping their aeronautical experiments altogether. One problem was that Wilbur found they didn't get near the lift he had predicted from his mathematical calculations, using Lilienthal's tables and Smeaton's coefficient. Smeaton's coefficient was an important number that had been first calculated by an English engineer named John Smeaton, who built windmills way back in the 1700's. Smeaton's number was .005
But Smeaton's wind mill blades were flat, not curved or cambered. His famous coefficient was for flat surfaces like his windmill blades. Moreover, Lillienthal's method of calculating for lift was for his own particular wing and didn't rely on Smeaton's coefficient as the Wrights thought. Please see John David Anderson.*
The Wrights mistakenly decided that Lillienthal's tables of lift and drag were wrong. But they also questioned Smeaton's coefficient.
So the Wrights went home to Dayton after their 1901 glides and decided to do their own experiments. If they couldn't trust the figures of the experts like Lilienthal, they said, they would find the right numbers on their own. They built a relatively crude wind tunnel at their shop powered by a gas engine.. In it they tested a large number of small wing shapes (air foils) to see what lift and drag they could predict.The Wright brothers attributed much of their success to their two months of wind tunnel tests Oct.- Dec.of 1901.
Wright historians state that the Wrights' discovered that Smeaton's coefficient was wrong for cambered (curved) wing shapes. Unfortunately, evidence doesn't support that claim. It wasn't the Wrights.
First of all, in Chanute's book Progress in Flying Machines, 1894, he states on page 172 that they would probably have to modify Smeaton's coefficient from .005 for curved surfaces. The Wrights had acquired this book, because it was recommended by the Smithsonian per Wilbur's request for information in 1899.
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| Professor Samuel Pierpont Langley, Secretary of the Smithsonian |
But even if the Wrights didn't carefully read Chanute's book, another pioneer had worked on the problem and already solved it. Professor Samuel Pierpont Langley, Secretary of the Smithsonian, was a proficient scientist who had done many years of research on the problem of flight. He had successfully built and launched his amazing heavier than air, steam powered model that flew 3/4 mile as early as 1896--three years before the Wrights began their studies in aeronautics. Langley had proven with his research and his successes that heavier than air flight was possible. Professor Langley's new number for Smeaton's coefficient had been established as .0033.
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Steady as she goes. Professor Langley's amazing steam powered model
takes to the air. Note the curve on the wings.
But here we have the following statement from the Smithsonian website The Wright Brothers, under "Correcting Smeaton": "A key term in the lift and drag equations was Smeaton’s coefficient, which accounted for the density of air. A value for the coefficient of 0.005 had been widely used since the 18th century. Using measurements obtained from their glider tests at Kitty Hawk and the lift equation, the Wright brothers calculated a new average value of 0.0033. Modern aerodynamicists have confirmed this figure to be accurate within a few percent." (emphasis mine) |
"...Professor Langley and also the Weather Bureau officials found that the correct coefficient of pressure was only about 0.0032, instead of Smeaton’s 0.005...”.
And, according to Anderson, page 221*, the Wrights used Langley's number. To give this assertion more credence, if the correct number calculated by aeronautical engineers today isn't quite .0033, Langley was slightly off. That the Wrights would come upon the identical slightly off number using measurements from their gliders or their crude wind tunnels is practically absurd. In my opinion, the odds against it would have to be huge.
Continuing research will uncover that the Wrights and their historians have claimed for themselves
more of the significant areas of Professor Langley's research, such as the effect on flying of the "aspect ratio" of the wings and the travel of the center of pressure. Please see future posts. It's time that aviation history is corrected and Langley's greatness be recognized again.
Orville and Wilbur Wright were bicycle manufacturers, with no high school diplomas, and still "wet behind the ears." They had just begun their aviation studies in 1899. Chanute's and Langley's research had been going on for over a decade. Orville would later state that he and Wilbur had garnered no assistance from the research of Professor Langley. They would also say that Octave Chanute had only provided moral support. See Fred Howard's "Wilbur and Orville."
The wrong isn't that the Wrights built on the research of others. That is as it should be. The wrong is that they didn't give the others credit and even worse, that they claimed the others' discoveries as their own.
To be continued....
*Anderson John D., Jr., A History of aerodynamics and its impact on flying machines, Cambridge University Press, 1997. Page numbers provided are from this edition.
John David Anderson, Jr., is Professor of Aerospace engineering at the University of Maryland and special assistant for aerodynamics at the National Air and Space Museum at the Smithsonian. Professor Anderson's book provides new insights to Professor Langley's research through his access to Langley's laboratory notebooks, on file in the Ramsey Room, the rare book room of the museum. However, in my opinion, he relies too heavily on the publications of Peter Jakab, Tom Crouch, and others for his historical conclusions. These are mostly a rehash of the Wright brothers' claims, many of which have never been truly verified.
