CHAPTER II

THE AEROPLANE

EXPERIMENTS WITH PLANES—LILLIENTHAL’S GLIDER—LANGLEY’S AERODROME—SUCCESS OF THE WRIGHTS—FIRST AEROPLANE FLIGHTS

The evolution of the heavier-than-air flying-machine, like that of the lighter-than-air, covers a long period of time, and was fraught with many difficulties and dangers. For ages many scientific men played with the idea, but owing to the lack of motive power light enough to be mounted on a glider yet supplying sufficient strength to drive a set of planes through the air at 45 miles an hour, very little progress was made until the perfection of the steam-engine and the development of the gasoline motor. Indeed, such things as lateral and longitudinal balance of planes, as well as steering by rudder, could only be worked out to a successful conclusion by man-carrying gliders moving at a sufficient velocity to keep them off the ground. Since no mechanical device driven by man could supply this want, the science lacked practical development until the last quarter of a century.

Perhaps the acrobatic tight-rope walker Allard, in 1660, was the first to make long glides during an exhibition of his profession. But nothing of material advantage to the science was accomplished.

In 1809 Sir George Cayley, an Englishman, planned an aeroplane with oblique planes, resting on a wheeled chassis, fitted with propellers, motors, and steering devices. The machine was never built.

In 1843 another Englishman, Samuel Henderson, designed and patented an “aerial steam carriage,” which was to be an aeroplane of immense size to be used for passenger carrying. Like the former it was never built.

M. Strongfellow, another Englishman, designed a triplane, which he fitted with a tail and two propellers. A triplane differs from a biplane only in that a third plane is superimposed over the second plane at the same distance as the second plane was above the first or monoplane. This model was shown at the exhibition of the Aeronautical Society of Great Britain in 1868. As in the case of previous inventors, nothing in this model indicated that he had any comprehension of the principles of stability or knowledge of the lifting capacity of surfaces, or the power required for dynamic flight.

In 1872 a French inventor, named Alphonse Penaud, constructed a small monoplane. It was only a toy—two flimsy wings actuated by a twisting rubber—but it had fore-and-aft stability. These model aeroplanes, however, aided the science materially by demonstrating the necessity for stability before planes could be steered through space. Subsequently, in 1875, Penaud took out a patent on a monoplane fitted with two propellers and having controlling devices. But this was not built, principally because it would have required a light motor, and the lightest available at that time weighed over 60 pounds per horse-power. To-day most aeromotors weigh less than two pounds per horse-power.

Louis Pierre Mouillard, a Frenchman, who had observed that large birds in flight, while seeming at rest, could go forward against the wind without a stroke of the wings, constructed a number of gliders built on the principle of bird wings, and experimented with gliding. He published a work called “L’Empire de l’Air,” which inspired many late experiments with gliders.

The net results of all these designs and experiments of these inventors demonstrated that thin, rigid surfaces of a certain shape, structure, and design could support weights when driven through the air at a sufficient velocity. Further than that they contributed practically nothing to the science of aviation.

As a matter of fact, it was toward the close of the nineteenth century before means were found to make an aeroplane rise from the ground, maintain its equilibrium. These latter-day pioneers of aviation were divided into two schools. The first sought to achieve soaring flights by means of large kitelike apparatus, which enabled them to fly in the air against winds, their machines being lifted up and supported by the inertia of the air as kites are. The second sought to develop power flight, that is, to send their kitelike machines through the air at high speed, being tracted or propelled by revolving screws actuated by motor power.

The most prominent experimenters of the first glider school were Otto Lillienthal, a German, P. L. Pitcher, an Englishman, Octave Chanute, and J. J. Montgomery.

Lillienthal was the first man to accomplish successful flights by means of artificial wing surfaces. In 1894, after much experimenting, he constructed rigid wings which he held to his shoulders. He used to run down hills with them until the velocity he was moving at would catch the air and lift him completely off the ground. By observation of birds he saw that their wings were arched, which suggested reason for failures of previous experiments in this line; so afterward his planes were arched also. He was the first man to be lifted off the ground by plane surfaces, and to demonstrate that arched surfaces were necessary to sustained flight of heavier-than-air craft.

To the rigid wings Lillienthal fastened a rigid tail and this constituted his glider. There were no control levers and the only way he could steer was by shifting the balance, by use of his legs, in one direction or another. By means of an artificial hill he had constructed he could coast downward for some distance without striking the ground. He was unfortunately killed in one of these experiments in 1896.

Chanute’s experiments in gliding were similar to Lillienthal’s, but they were conducted on the sand-dunes along Lake Michigan, near Chicago. His apparatus was more strongly constructed, of trussed biplane type—a construction suggested to him by his experience in bridge building, and one which persists to-day as the basis of strength in our present military biplanes. In design it was similar to a box kite, and it was the kind which the Wrights adopted for their experiments.

The leaders of the second school were: Clement Ader (1890-97), Sir Hiram Stevens Maxim (1890-94), and Samuel Pierpont Langley (1895-1903).

Clement Ader, the famous French scientist, under the auspices of the French Government, conducted experiments from 1890 to 1897. In 1890 he filled his Arion, a boat-shaped machine with two propellers, with a steam-engine, but the apparatus never flew. He finished his next machine in 1897 after six years of hard work. It was large enough to carry a man, but, like its predecessor, it never left the ground, and the French Government refused to support his experiments further.

While Ader was making his experiments in France, Sir Hiram S. Maxim was at work constructing a large multiplane for the English Government, which he fitted with two steam-engines of 175 horse-power. But like Ader’s experiments it toppled over at the first trial and was badly damaged, and the British Government refused further backing.

The experience of Samuel Pierpont Langley in America is not unlike the experience of Ader in France and Maxim in England. He was employed by the Board of Ordnance and Fortification of the United States army to construct the “Aerodrome” of his own invention. Congress appropriated $50,000 for the purpose. Langley’s machine was a tandem monoplane, 48 feet from tip to tip, and 52 feet from bowsprit to the end of its tail. It was fitted with a 50 horse-power engine and weighed 830 pounds. The trials of this aerodrome, two attempts to launch it, were made on October 7 and December 8, 1903. On both occasions the aerodrome became entangled in the defective launching apparatus, and was thrown headlong into the Potomac River—on which the launching trials were made. Following the last failure, when the aerodrome was wrecked, the press ridiculed the whole enterprise, and Congress refused to appropriate money for further experiments. The Langley aerodrome, fitted with a Curtiss motor and Curtiss controls, flew in 1913-14.

As with experiments of the first school they did not attain practical results. The machines were usually wrecked at the first trial without giving any clew to the nature or whereabouts of the trouble. Although Langley’s machines were reconstructed and flown later this should not detract in any way from the fame of the Wright brothers, Orville and Wilbur, who really were the first to construct an aeroplane which was driven by a gasoline motor, lifting a man off the ground, and pursuing a steered and sustained flight through the air.

The experiments of Lillienthal and his death in his glider were the direct incentives to the Wright brothers to conduct their investigations with gliders. The Lillienthal way of balancing the planes by swinging his legs they judged to be a poor means of controlling the direction of the flight. So they set out to discover another method of controlling the stability of the planes. Their experiments began in the fall of 1900 at Kitty Hawk, North Carolina, as Mr. Henry Woodhouse, the aeronautical authority, has pointed out. They took all the theories of flight and tried them one by one, only to find, after two years of hard, discouraging work, that they were based more or less on guesswork. Thereupon they cast aside old theories and patiently put the apparatus through innumerable gliding tests, ever changing, adding, modifying—setting down the results; after each glide comparing, changing again and again, until they finally constructed a glider which was easy to balance both laterally and longitudinally. But in order to control fore-and-aft balance they had to eliminate Lillienthal’s method of swinging his legs and substitute a horizontal elevator. This elevator was raised and lowered by a lever operated by the pilot stretched out on the centre of the lower wing of the glider. This device kept the glider level with respect to the ground. In fact, this elevator was absolutely necessary to prevent the planes from diving up or down, for if the pilot found the glider pitching too much forward, tending to dive, he would tilt the elevator upward by means of the lever, thus pulling the nose of the glider back into its proper position. At first the Wrights built the elevator in front of the planes so that they could see and study its effect. They soon discovered that the control of the glider was much better with the elevator. This elevator has been incorporated as a standard fin on the tail of the fuselage of every aeroplane and is one of the chief factors in steering up or down.

Having completely mastered this most important step, the Wrights next took up the problem of lateral control. The natural tendency of the glider was to flop about like a kite with too light a tail. In order to correct this lateral instability the Wrights determined to make the air itself, rather than gravity, supply this balance, instead of Lillienthal’s method of swinging his legs from side to side by observing closely the way in which a pigeon secures its lateral balance by varying the angle of attack with its two wings, whereby one wing would lift more forcibly than the other, thereby turning the bird in any direction around any given axis of flight. In order to accomplish this variation the Wrights made the ends of the glider loose while the rest remained rigid. Then by a system of wires operated from a lever they could warp these wing ends of the glider, one to present a greater angle of attack to the air and the other a smaller angle, just as the pigeon did. In other words, by pulling down the rear edge of the tip of one wing and by pulling up the extreme edge of the other the angles of the wings were varied with respect to the way in which they cut through the air on very much the same principles as the tail elevator on the fuselage. Also, if a flat surface moves through the air horizontal to the ground, if you tipped the rear edge upward the air would strike it on that edge and have a tendency to force it down, thus forcing the forward edge upward. To pull it in the other direction would cause the opposite effect. The Wrights were first to incorporate this in a glider or aeroplane. They patented it, and although a hinge, called an aileron, was later attached to the end of the wings of an aeroplane to produce the same effect and at the same time to allow more rigid construction of the ends of the wings, nevertheless this idea was distinctly a Wright discovery and innovation.

[Illustration:

_Courtesy of Flying Magazine._

The Wright flyer after the epoch-making flight at Kitty Hawk, N. C., December, 1903.

This was the first successful motor-driven heavier-than-air craft to lift a man off the ground and carry him over a steered course. It had one 16 h.-p. motor with a chain-drive to two propellers. The elevators were in front of the machine. The plane resembles a glider or a box kite and the wings could be warped for steering.]

But that was not all the Wright brothers did to make man-flight over a sustained and steered course in a heavier-than-air machine possible. Directional control or power to steer the glider in a straight line or to vary it had not yet been acquired, so the Wrights installed a vertical rudder which they also operated by lever, just as the rudder on a power-boat is controlled, and the effect on directional steering was the same. Indeed, passage through the medium of the air is in many ways similar to passage through water. Thus the moment the glider swerved from right to left the rudder was pulled in the opposite direction and the planes came back to the steered course.

But this was not invented at once nor installed until after the Wrights discovered that whenever the glider was in flight the effect of warping the wings to control the rolling had a serious unexpected secondary effect, namely, a tendency for the high wing, which they desired to bring down, to advance faster through the air than the low wing, and solely by its higher velocity to develop a higher lifting capacity and thus to neutralize the benefit of the warp. After much experimenting they hit upon the rudder idea and that corrected the difficulty.

Thus the Wrights gained complete mastery of the glider; they could steer it up and down, turn it from right to left, and bring it back safely to the earth. This is the basis of the Wright patents to-day.

The next thing to be done was to install upon an aeroplane a power plant sufficient to drive it through the air fast enough to make the air lift it off the ground and sustain it in the “liquid blue” until the pilot saw fit to glide to the earth again. This was by no means a simple matter, for from 1900, when the Wrights began their glider experiments, to 1903, when they made their first flight, the gasoline motor was in its impotent infancy. They set about building a small light motor, however, to install in their planes.

In the meantime they experimented further with wing surfaces. Langley and Chanute had proved flat wings inefficient and curved wings necessary for lifting capacity. Of course, those early experimenters did not know how much those curvatures affected the climbing angle of a glider, so the Wrights set out to find out by using the wind-tunnel method and testing scale models in the same, with a blast of air generated by an engine-driven fan. This tunnel was cylindrical in form, sixteen inches in diameter. The smaller models of wings were hung in the centre, the air-blast turned on, and the balance arm, which projected into the tunnel and on which the wings were mounted, measured the air forces and the efficiency of the varied wing shapes from the standpoint of rounded wing tips and curvature.

Data acquired in experimenting with their six-inch model biplane in this determined them to build their aeroplane on that scale, even though it was discovered that two wings together were less efficient than one wing by itself. The rigidity of two wings added a safety factor, so they adopted the biplane or two-plane surface rather than the monoplane or one-plane surface.

In these experiments the Wrights also discovered that all surfaces shaped like a fish offered less resistance to the air than blunter obtuse surfaces, so they adopted the stream-line method in construction of struts or supports to the two wings, so that now all surfaces that cut the air in the forward progress of the planes are rounded off so that the air slips off with the least resistance. This was an important discovery, for later when the enclosed fuselage or body in which the aviator sits was constructed it had much to do in determining its shape and design.

Propellers had already been experimented with as a means of propulsion through the air. Because of the low horse-power at which they were driven very little scientific data as to propeller efficiency had been compiled. Because the first motor constructed by the Wrights had only 16 horse-power at maximum speed, which soon fell off to 12 horse-power, the two propellers mounted on their first machine developed a high propeller efficiency. To-day propeller efficiency has reached approximately 70 per cent of efficiency, and much study has been devoted to the propeller.

Because no gasoline motor was in existence light enough to mount on their glider the Wrights built their own in their shops in Dayton. It was a four-cylinder water-cooled upright motor, and it could develop 12 horse-power. The engine was mounted on the rear of the planes of the glider and by a chain drive propelled the two blades mounted in the rear of the two planes, thus making a pusher type of aeroplane. The estimate of the total weight of the machine and the operator was between 750 and 800 pounds.

With this machine, on December 17, 1903, Wilbur Wright made the world’s first sustained steered flight of 852 feet in 59 seconds in a heavier-than-air machine. To them really belongs the honor of having invented the aeroplane and of having demonstrated the feasibility of navigating the air in a heavier-than-air machine. It is true that the Frenchman M. Bleriot was the man who covered the fuselage, put the engine in front of the aviator, and constructed a monoplane similar in shape to a bird. Nevertheless, it is the Wrights who built the aeroplane which met all the fundamental requirements of flight through the air.

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