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Alaxander The Great

Essay by 24  •  November 13, 2010  •  2,777 Words (12 Pages)  •  810 Views

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This is the story of how two honest, straightforward, hard-working Americans who have accomplished something fantastic and magical; creating a craft of stick and fabric that flew in the air like the chariots of the gods, opening the skies to all humankind. Their success came so suddenly and from such an unexpected quarter that their colleagues could not believe the Wrights had done what they claimed. After all, if well-known scientists and engineers all over the world had been puzzled in their efforts to invent the airplane, how could two common men from rustic America have succeeded?

Around the turn of the century, dozens of people were working to invent the airplane. The period of active experimentation began in 1891 when German engineer Otto Lilienthal began experimenting with hang gliders. Through an extensive study of birds and bird flight, he realized that the lift function and the thrust function of bird wings were separate and distinct, and could be imitated by different systems on a fixed-wing craft. Lilienthal began his work on heavier-than-air craft not by developing a complete airplane, but instead by focusing his efforts on a fixed-wing glider.

Lilienthal brought a much-needed respectability to the enterprise of inventing an airplane. Up to that point, efforts to invent airplanes were considered to be the province of crackpots and wild-eyed dreamers. But when a hard-headed German engineer entered the game, other respectable people were soon to follow.

In addition to the respectability he brought to the field, Lilienthal made two more important contributions to the nascent field of airplane invention: the style of perfecting a glider before attempting powered flight, and a table of the lift provided by curved wings. Lilienthal was killed in a gliding accident August 10, 1896.

Following in Lilienthal's footsteps, efforts to invent an airplane became commonplace in the 1890's. The majority of the efforts were in Europe, including Captain F. Ferber, Henri Robart, Solirene, Levavasseur, Clement Ader, Percy Pilcher, and Sir Hiram Maxim. In the U.S., prominent attempts were made by Octave Chanute and Samuel Pierpont Langley.

During the years 1894 to 1905, it only occasional crafts that flew farther than 100 meters (about the length of a football field), this level of performance was exceptional. Unfortunately, inventors at the time were unable to capitalize on their success. Often times a new generation craft did not perform as well as its predecessor.

The Wrights began their efforts to invent the airplane by carefully studying what others had done before. They read everything they could get their hands on, including Octave Chanute's Progress in Flying Machines, the 1895, 1896, and 1897 volumes of the Aeronautical Annual, and popular articles in newspapers and magazines. It seems obvious to begin with a logical study of past efforts, especially trying to understand the failures and limitations of previous work. Still, many never bothered to put in the effort; by ignoring the lessons of the past, they frequently suffered greatly. The Wrights took the time to do their homework. The brothers exhibited an unusual ability to judge the worth of ideas they read, discarding as useless some widely-held superstitions in the field, identifying the hard facts, and carefully integrating bits and fragments of knowledge scattered through the literature.

The Wrights followed the example set by Lilienthal of beginning with the glider. Only after they solved the problems of gliding flight did they feel it worthwhile to tackle the more difficult challenge of building a powered airplane. This decision was doubtless influenced by Lilienthal's arguments, but Lilienthal and others also advocated the same approach. The Wrights also chose to pattern their aircraft after the Chanute-Herring biplane, a sturdy and relatively successful biplane glider. Lilienthal's data on the lift of wing surfaces were used in their design of the 1900 and 1901 gliders.

By careful study, the Wrights identified the best features of past aircraft and employed aeronautical theory about the lift of wings to design their first craft. Although it did not perform as expected, it was among the best gliders that had ever been built.

Once you have a design that is at least partially successful, a simple strategy is to refine the design to make it better. This method is generally referred to as hill-climbing. Hill climbing is only possible when a designer can identify the specific strengths and weaknesses of an invention. Knowing that, it is a simple matter to preserve the strengths and improve upon the weaknesses, making the overall design better and better.

Most hopeful inventors employed the Design and Test strategy for invention. A new design was identified. The craft was constructed and then taken out to the field for testing. The results of the testing were used in making a new design, completing the loop. The loop consisted of design, development, and testing.

This strategy was not effective. Unfortunately, there was a good reason why the approach did not work: A field test does not reveal the specific strengths and weaknesses of a craft. When tested in the field, an inventor learns a few simple things about a craft. The inventor can easily measure how far the craft flew and how long it remained airborne. The inventor may get some feel for other aspects of the craft's performance, such as how sensitive it is to disturbances in the air, how responsive it might be to the pilot's control, and things like that. You consider for a moment how an inventor might refine the airplane or design a new model using this information from a field test.

First, consider the value of objective numbers like time and distance in flight. For example, a glider may remain in the air for only a short time because it does not have sufficient lift, or because it has too much drag. The inventor has no way of knowing which problem to work on. A powered plane may not have enough thrust, may not have enough lift, or may have too much drag. This formed quite a challenge for the brothers.

Subjective measures, like the 'feel' of the craft in flight, are even worse, because they are caused by pilot error and the test conditions. A craft tested on a calm day may seem to have sufficient control, but the revised version tested on a windy day will seem balky and troublesome. When the pilot makes a mistake, he may blame the craft, not his own actions.

Under the circumstances, inventors do not get useful information out of field trials that help them improve their design. Often times we find early models fly better than their successors, as inventors root out the good in their design, and leave more of the bad.

The Wrights found the trap door out of this unhappy method.



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