ORVILLE WRIGHT IN THE 80-MILE-AN-HOUR “BABY WRIGHT” RACER.

How It Flies
or,
THE CONQUEST OF THE AIR
The Story of Man’s Endeavors to Fly and of the
Inventions by which He Has Succeeded
By
RICHARD FERRIS, B.S., C.E.
Illustrated by Over One Hundred and Fifty Half-tones and Line
Drawings, Showing the Stages of Development from the
Earliest Balloon to the Latest Monoplane and Biplane
New York
THOMAS NELSON AND SONS
381-385 Fourth Avenue

Copyright, 1910, by
THOMAS NELSON & SONS

THE TROW PRESS, NEW YORK

PREFACE

In these pages, by means of simple language and suitable pictures, the author has told the story of the Ships of the Air. He has explained the laws of their flight; sketched their development to the present day; shown how to build the flying machine and the balloon, and how to operate them; recounted what man has done, and what he hopes to do with their aid. In a word, all the essential facts that enter into the Conquest of the Air have been gathered into orderly form, and are here presented to the public.

We who live to-day have witnessed man’s great achievement; we have seen his dream of ages come true. Man has learned to fly!

The air which surrounds us, so intangible and so commonplace that it seldom arrests our attention, is in reality a vast, unexplored ocean, fraught with future possibilities. Even now, the pioneers of a countless fleet are hovering above us in the sky, while steadily, surely these wonderful possibilities are unfolded.

The Publishers take pleasure in acknowledging their indebtedness to the Scientific American for their courtesy in permitting the use of many of the illustrations appearing in this book.

New York, October 20, 1910.

CONTENTS

HOW IT FLIES

Chapter I.
INTRODUCTORY.

The sudden awakening—Early successes—Influence of the gasoline engine on aeroplanes—On dirigible balloons—Interested inquiry—Some general terms defined.

In the year 1908 the world awakened suddenly to the realization that at last the centuries of man’s endeavor to fly mechanically had come to successful fruition.

There had been a little warning. In the late autumn of 1906, Santos-Dumont made a flight of 720 feet in a power-driven machine. There was an exclamation of wonder, a burst of applause—then a relapse into unconcern.

In August, 1907, Louis Bleriot sped free of the ground for 470 feet; and in November, Santos-Dumont made two flying leaps of barely 500 feet. That was the year’s record, and it excited little comment. It is true that the Wright brothers had been making long flights, but they were in secret. There was no public knowledge of them.

In 1908 came the revelation. In March, Delagrange flew in a Voisin biplane 453 feet, carrying Farman with him as a passenger. Two weeks later he flew alone nearly 2½ miles. In May he flew nearly 8 miles. In June his best flight was 10½ miles. Bleriot came on the scene again in July with a monoplane, in which he flew 3¾ miles. In September, Delagrange flew 15 miles—in less than 30 minutes. In the same month the Wrights began their wonderful public flights. Wilbur, in France, made records of 41, 46, 62, and 77 miles, while Orville flew from 40 to 50 miles at Fort Myer, Va. Wilbur Wright’s longest flight kept him in the air 2 hours and 20 minutes.

The goal had been reached—men had achieved the apparently impossible. The whole world was roused to enthusiasm.

Since then, progress has been phenomenally rapid, urged on by the striving of the inventors, the competition of the aircraft builders, and the contests for records among the pilots.

By far the largest factor in the triumph of the aeroplane is the improved gasoline engine, designed originally for automobiles. Without this wonderful type of motor, delivering a maximum of power with a minimum of weight, from concentrated fuel, the flying machine would still be resting on the earth.

The Renard and Krebs airship La France, at Chalais-Meudon.

Nor has the influence of the gasoline motor been much less upon that other great class of aircraft, the dirigible balloon. After 1885, when Renard and Krebs’ airship La France made its two historic voyages from Chalais-Meudon to Paris, returning safely to its shed, under the propulsion of an electric motor, the problem of the great airship lay dormant, waiting for the discovery of adequate motive power. If the development of the dirigible balloon seems less spectacular than that of the aeroplane, it is because the latter had to be created; the dirigible, already in existence, had only to be revivified.

Confronted with these new and strange shapes in the sky, some making stately journeys of hundreds of miles, others whirring hither and thither with the speed of the whirlwind, wonder quickly gives way to the all-absorbing question: How do they fly? To answer fully and satisfactorily, it seems wise, for many readers, to recall in the succeeding chapters some principles doubtless long since forgotten.

As with every great advance in civilization, this expansion of the science of aeronautics has had its effect upon the language of the day. Terms formerly in use have become restricted in application, and other terms have been coined to convey ideas so entirely new as to find no suitable word existent in our language. It seems requisite, therefore, first to acquaint the reader with clear definitions of the more common terms that are used throughout this book.

Aeronautics is the word employed to designate the entire subject of aerial navigation. An aeronaut is a person who sails, or commands, any form of aircraft, as distinguished from a passenger.

Aviation is limited to the subject of flying by machines which are not floated in the air by gas. An aviator is an operator of such machine.

A free balloon, with parachute.

Both aviators and aeronauts are often called pilots.

A balloon is essentially an envelope or bag filled with some gaseous substance which is lighter, bulk for bulk, than the air at the surface of the earth, and which serves to float the apparatus in the air. In its usual form it is spherical, with a car or basket suspended below it. It is a captive balloon if it is attached to the ground by a cable, so that it may not rise above a certain level, nor float away in the wind. It is a free balloon if not so attached or anchored, but is allowed to drift where the wind may carry it, rising and falling at the will of the pilot.

A dirigible balloon.

A dirigible balloon, sometimes termed simply a dirigible, usually has its gas envelope elongated in form. It is fitted with motive power to propel it, and steering mechanism to guide it. It is distinctively the airship.

Aeroplanes are those forms of flying machines which depend for their support in the air upon the spread of surfaces which are variously called wings, sails, or planes. They are commonly driven by propellers actuated by motors. When not driven by power they are called gliders.

A biplane glider.

Aeroplanes exist in several types: the monoplane, with one spread of surface; the biplane, with two spreads, one above the other; the triplane, with three spreads, or decks; the multiplane, with more than three.

The tetrahedral plane is a structure of many small cells set one upon another.

Ornithopter is the name given to a flying machine which is operated by flapping wings.

A parachute descending.

Helicopter is used to designate machines which are lifted vertically and sustained in the air by propellers revolving in a horizontal plane, as distinguished from the propellers of the aeroplane, which revolve in vertical planes.

A parachute is an umbrella-like contrivance by which an aeronaut may descend gently from a balloon in mid-air, buoyed up by the compression of the air under the umbrella.

For the definition of other and more technical terms the reader is referred to the carefully prepared Glossary toward the end of the book.

Chapter II.
THE AIR.

Intangibility of air—Its substance—Weight—Extent—Density—Expansion by heat—Alcohol fire—Turbulence of the air—Inertia—Elasticity—Viscosity—Velocity of winds—Aircurrents—Cloud levels—Aerological stations—High altitudes—Practical suggestions—The ideal highway.

The air about us seems the nearest approach to nothingness that we know of. A pail is commonly said to be empty—to have nothing in it—when it is filled only with air. This is because our senses do not give us any information about air. We cannot see it, hear it, touch it.

When air is in motion (wind) we hear the noises it makes as it passes among other objects more substantial; and we feel it as it blows by us, or when we move rapidly through it.

We get some idea that it exists as a substance when we see dead leaves caught up in it and whirled about; and, more impressively, when in the violence of the hurricane it seizes upon a body of great size and weight, like the roof of a house, and whisks it away as though it were a feather, at a speed exceeding that of the fastest railroad train.

In a milder form, this invisible and intangible air does some of our work for us in at least two ways that are conspicuous: it moves ships upon the ocean, and it turns a multitude of windmills, supplying the cheapest power known.

That this atmosphere is really a fluid ocean, having a definite substance, and in some respects resembling the liquid ocean upon which our ships sail, and that we are only crawling around on the bottom of it, as it were, is a conception we do not readily grasp. Yet this conception must be the foundation of every effort to sail, to fly, in this aerial ocean, if such efforts are to be crowned with success.

As a material substance the air has certain physical properties, and it is the part of wisdom for the man who would fly to acquaint himself with these properties. If they are helpful to his flight, he wants to use them; if they hinder, he must contrive to overcome them.

In general, it may be said that the air, being in a gaseous form, partakes of the properties of all gases—and these may be studied in any text-book on physics, Here we are concerned only with those qualities which affect conditions under which we strive to fly.

Of first importance is the fact that air has weight. That is, in common with all other substances, it is attracted by the mass of the earth exerted through the force we call gravity. At the level of the sea, this attraction causes the air to press upon the earth with a weight of nearly fifteen pounds (accurately, 14.7 lbs.) to the square inch, when the temperature is at 32° F. That pressure is the weight of a column of air one inch square at the base, extending upward to the outer limit of the atmosphere—estimated to be about 38 miles (some say 100 miles) above sea-level. The practical fact is that normal human life cannot exist above the level of 15,000 feet, or a little less than three miles; and navigation of the air will doubtless be carried on at a much lower altitude, for reasons which will appear as we continue.

The actual weight of a definite quantity of dry air—for instance, a cubic foot—is found by weighing a vessel first when full of air, and again after the air has been exhausted from it with an air-pump. In this way it has been determined that a cubic foot of dry air, at the level of the sea, and at a temperature of 32° F., weighs 565 grains—about 0.0807 lb. At a height above the level of the sea, a cubic foot of air will weigh less than the figure quoted, for its density decreases as we go upward, the pressure being less owing to the diminished attraction of the earth at the greater distance. For instance, at the height of a mile above sea-level a cubic foot of air will weigh about 433 grains, or 0.0619 lb. At the height of five miles it will weigh about 216 grains, or 0.0309 lb. At thirty-eight miles it will have no weight at all, its density being so rare as just to balance the earth’s attraction. It has been calculated that the whole body of air above the earth, if it were all of the uniform density of that at sea-level, would extend only to the height of 26,166 feet. Perhaps a clearer comprehension of the weight and pressure of the ocean of air upon the earth may be gained by recalling that the pressure of the 38 miles of atmosphere is just equal to balancing a column of water 33 feet high. The pressure of the air, therefore, is equivalent to the pressure of a flood of water 33 feet deep.

Comparative Elevations of Earth and Air.

But air is seldom dry. It is almost always mingled with the vapor of water, and this vapor weighs only 352 grains per cubic foot at sea-level. Consequently the mixture—damp air—is lighter than dry air, in proportion to the moisture it contains.

Apparatus to show effects of heat on air currents. a, alcohol lamp; b, ice. The arrows show direction of currents.

Another fact very important to the aeronaut is that the air is in constant motion. Owing to its ready expansion by heat, a body of air occupying one cubic foot when at a temperature of 32° F. will occupy more space at a higher temperature, and less space at a lower temperature. Hence, heated air will flow upward until it reaches a point where the natural density of the atmosphere is the same as its expanded density due to the heating. Here another complication comes into play, for ascending air is cooled at the rate of one degree for every 183 feet it rises; and as it cools it grows denser, and the speed of its ascension is thus gradually checked. After passing an altitude of 1,000 feet the decrease in temperature is one degree for each 320 feet of ascent. In general, it may be stated that air is expanded one-tenth of its volume for each 50° F. that its temperature is raised.

This highly unstable condition under ordinary changes of temperature causes continual movements in the air, as different portions of it are constantly seeking that position in the atmosphere where their density at that moment balances the earth’s attraction.

Sir Hiram Maxim relates an incident which aptly illustrates the effect of change of temperature upon the air. He says: “On one occasion, many years ago, I was present when a bonded warehouse in New York containing 10,000 barrels of alcohol was burned.... I walked completely around the fire, and found things just as I expected. The wind was blowing a perfect hurricane through every street in the direction of the fire, although it was a dead calm everywhere else; the flames mounted straight in the air to an enormous height, and took with them a large amount of burning wood. When I was fully 500 feet from the fire, a piece of partly burned one-inch board, about 8 inches wide and 4 feet long, fell through the air and landed near me. This board had evidently been taken up to a great height by the tremendous uprush of air caused by the burning alcohol.”

That which happened on a small scale, with a violent change of temperature, in the case of the alcohol fire, is taking place on a larger scale, with milder changes in temperature, all over the world. The heating by the sun in one locality causes an expansion of air at that place, and cooler, denser air rushes in to fill the partial vacuum. In this way winds are produced.

So the air in which we are to fly is in a state of constant motion, which may be likened to the rush and swirl of water in the rapids of a mountain torrent. The tremendous difference is that the perils of the water are in plain sight of the navigator, and may be guarded against, while those of the air are wholly invisible, and must be met as they occur, without a moment’s warning.

The solid arrows show the directions of a cyclonic wind on the earth’s surface. At the centre the currents go directly upward. In the upper air above the cyclone the currents have the directions of the dotted arrows.

Next in importance, to the aerial navigator, is the air’s resistance. This is due in part to its density at the elevation at which he is flying, and in part to the direction and intensity of its motion, or the wind. While this resistance is far less than that of water to the passage of a ship, it is of serious moment to the aeronaut, who must force his fragile machine through it at great speed, and be on the alert every instant to combat the possibility of a fall as he passes into a rarer and less buoyant stratum.

Diagram showing disturbance of wind currents by inequalities of the ground, and the smoother currents of the upper air. Note the increase of density at A and B, caused by compression against the upper strata.

Three properties of the air enter into the sum total of its resistance—inertia, elasticity, and viscosity. Inertia is its tendency to remain in the condition in which it may be: at rest, if it is still; in motion, if it is moving. Some force must be applied to disturb this inertia, and in consequence when the inertia is overcome a certain amount of force is used up in the operation. Elasticity is that property by virtue of which air tends to reoccupy its normal amount of space after disturbance. An illustration of this tendency is the springing back of the handle of a bicycle pump if the valve at the bottom is not open, and the air in the pump is simply compressed, not forced into the tire. Viscosity may be described as “stickiness”—the tendency of the particles of air to cling together, to resist separation. To illustrate: molasses, particularly in cold weather, has greater viscosity than water; varnish has greater viscosity than turpentine. Air exhibits some viscosity, though vastly less than that of cold molasses. However, though relatively slight, this viscosity has a part in the resistance which opposes the rapid flight of the airship and aeroplane; and the higher the speed, the greater the retarding effect of viscosity.

The inertia of the air, while in some degree it blocks the progress of his machine, is a benefit to the aeronaut, for it is inertia which gives the blades of his propeller “hold” upon the air. The elasticity of the air, compressed under the curved surfaces of the aeroplane, is believed to be helpful in maintaining the lift. The effect of viscosity may be greatly reduced by using surfaces finished with polished varnish—just as greasing a knife will permit it to be passed with less friction through thick molasses.

In the case of winds, the inertia of the moving mass becomes what is commonly termed “wind pressure” against any object not moving with it at an equal speed. The following table gives the measurements of wind pressure, as recorded at the station on the Eiffel Tower, for differing velocities of wind:

In applying this table, the velocity to be considered is the net velocity of the movements of the airship and of the wind. If the ship is moving 20 miles an hour against a head wind blowing 20 miles an hour, the net velocity of the wind will be 40 miles an hour, and the pressure 4.8 lbs. a square foot of surface presented. Therefore the airship will be standing still, so far as objects on the ground are concerned. If the ship is sailing 20 miles an hour with the wind, which is blowing 20 miles an hour, the pressure per square foot will be only 1.2 lbs.; while as regards objects on the ground, the ship will be travelling 40 miles an hour.

Apparatus for the study of the action of air in motion; a blower at the farther end of the great tube sends a “wind” of any desired velocity through it. Planes and propellers of various forms are thus tested.

Systematic study of the movements of the air currents has not been widespread, and has not progressed much beyond the gathering of statistics which may serve as useful data in testing existing theories or formulating new ones.

It is already recognized that there are certain “tides” in the atmosphere, recurring twice daily in six-hour periods, as in the case of the ocean tides, and perhaps from the same causes. Other currents are produced by the earth’s rotation. Then there are the five-day oscillations noted by Eliot in India, and daily movements, more or less regular, due to the sun’s heat by day and the lack of it by night. The complexity of these motions makes scientific research extremely difficult.

Something definite has been accomplished in the determination of wind velocities, though this varies largely with the locality. In the United States the average speed of the winds is 9½ miles per hour; in Europe, 10⅓ miles; in Southern Asia, 6½ miles; in the West Indies, 6⅕ miles; in England, 12 miles; over the North Atlantic Ocean, 29 miles per hour. Each of these average velocities varies with the time of year and time of day, and with the distance from the sea. The wind moves faster over water and flat, bare land than over hilly or forest-covered areas. Velocities increase as we go upward in the air, being at 1,600 feet twice what they are at 100 feet. Observations of the movements of cloud forms at the Blue Hill Observatory, near Boston, give the following results:

In winter the speed of cirrus clouds may reach 96 miles per hour.

There are forty-nine stations scattered over Germany where statistics concerning winds are gathered expressly for the use of aeronauts. At many of these stations records have been kept for twenty years. Dr. Richard Assman, director of the aerological observatory at Lindenburg, has prepared a comprehensive treatise of the statistics in possession of these stations, under the title of Die Winde in Deutschland. It shows for each station, and for each season of the year, how often the wind blows from each point of the compass; the average frequency of the several degrees of wind; when and where aerial voyages may safely be made; the probable drift of dirigibles, etc. It is interesting to note that Friedrichshafen, where Count Zeppelin’s great airship sheds are located, is not a favorable place for such vessels, having a yearly record of twenty-four stormy days, as compared with but two stormy days at Celle, four at Berlin, four at Cassel, and low records at several other points.

In practical aviation, a controlling factor is the density of the air. We have seen that at an altitude of five miles the density is about three-eighths the density at sea-level. This means that the supporting power of the air at a five-mile elevation is so small that the area of the planes must be increased to more than 2½ times the area suited to flying near the ground, or that the speed must be largely increased. Therefore the adjustments necessary for rising at the lower level and journeying in the higher level are too large and complex to make flying at high altitudes practicable—leaving out of consideration the bitter cold of the upper regions.

Mr. A. Lawrence Rotch, director of the Blue Hill Observatory, in his valuable book, The Conquest of the Air, gives this practical summary of a long series of studious observations: “At night, however, because there are no ascending currents, the wind is much steadier than in the daytime, making night the most favorable time for aerial navigation of all kinds.... A suitable height in the daytime, unless a strong westerly wind is sought, lies above the cumulus clouds, at the height of about a mile; but at night it is not necessary to rise so high; and in summer a region of relatively little wind is found at a height of about three-fourths of a mile, where it is also warmer and drier than in the daytime or at the ground.”

Notwithstanding all difficulties, the fact remains that, once they are overcome, the air is the ideal highway for travel and transportation. On the sea, a ship may sail to right or left on one plane only. In the air, we may steer not only to right or left, but above and below, and obliquely in innumerable planes. We shall not need to traverse long distances in a wrong direction to find a bridge by which we may cross a river, nor zigzag for toilsome miles up the steep slopes of a mountain-side to the pass where we may cross the divide. The course of the airship is the proverbial bee-line—the most economical in time as well as in distance.

Chapter III.
LAWS OF FLIGHT.

The bird—Nature’s models—Man’s methods—Gravity—The balloon—The airship—Resistance of the air—Winds—The kite—Laws of motion and force—Application to kite-flying—Aeroplanes.

If we were asked to explain the word “flying” to some foreigner who did not know what it meant, we should probably give as an illustration the bird. This would be because the bird is so closely associated in our thoughts with flying that we can hardly think of the one without the other.

It is natural, therefore, that since men first had the desire to fly they should study the form and motions of the birds in the air, and try to copy them. Our ancestors built immense flopping wings, into the frames of which they fastened themselves, and with great muscular exertion of arms and legs strove to attain the results that the bird gets by apparently similar motions.

However, this mental coupling of the bird with the laws of flight has been unfortunate for the achievement of flight by man. And this is true even to the present day, with its hundreds of successful flying machines that are not in the least like a bird. This wrongly coupled idea is so strong that scientific publications print pages of research by eminent contributors into the flight of birds, with the attempt to deduce lessons therefrom for the instruction of the builders and navigators of flying machines.

These arguments are based on the belief that Nature never makes a mistake; that she made the bird to fly, and therefore the bird must be the most perfect model for the successful flying machine. But the truth is, the bird was not made primarily to fly, any more than man was made to walk. Flying is an incident in the life of a bird, just as walking is an incident in the life of a man. Flying is simply a bird’s way of getting about from place to place, on business or on pleasure, as the case may be.

Santos-Dumont, in his fascinating book, My Air-Ships, points out the folly of blindly following Nature by showing that logically such a procedure would compel us to build our locomotives on the plan of gigantic horses, with huge iron legs which would go galloping about the country in a ridiculously terrible fashion; and to construct our steamships on the plan of giant whales, with monstrous flapping fins and wildly lashing tails.

Sir Hiram Maxim says something akin to this in his work, Artificial and Natural Flight: “It appears to me that there is nothing in Nature which is more efficient, or gets a better grip on the water, than a well-made screw propeller; and no doubt there would have been fish with screw propellers, providing Dame Nature could have made an animal in two pieces. It is very evident that no living creature could be made in two pieces, and two pieces are necessary if one part is stationary and the other revolves; however, the tails and fins very often approximate to the action of propeller blades; they turn first to the right and then to the left, producing a sculling effect which is practically the same. This argument might also be used against locomotives. In all Nature we do not find an animal travelling on wheels, but it is quite possible that a locomotive might be made that would walk on legs at the rate of two or three miles an hour. But locomotives with wheels are able to travel at least three times as fast as the fleetest animal with legs, and to continue doing so for many hours at a time, even when attached to a very heavy load. In order to build a flying machine with flapping wings, to exactly imitate birds, a very complicated system of levers, cams, cranks, etc., would have to be employed, and these of themselves would weigh more than the wings would be able to lift.”

As with the man-contrived locomotive, so the perfected airship will be evolved from man’s understanding of the obstacles to his navigation of the air, and his overcoming of them by his inventive genius. This will not be in Nature’s way, but in man’s own way, and with cleverly designed machinery such as he has used to accomplish other seeming impossibilities. With the clearing up of wrong conceptions, the path will be open to more rapid and more enduring progress.

When we consider the problem of flying, the first obstacle we encounter is the attraction which the earth has for us and for all other objects on its surface. This we call weight, and we are accustomed to measure it in pounds.

Let us take, for example, a man whose body is attracted by the earth with a force, or weight, of 150 pounds. To enable him to rise into the air, means must be contrived not only to counteract his weight, but to lift him—a force a little greater than 150 pounds must be exerted. We may attach to him a bag filled with some gas (as hydrogen) for which the earth has less attraction than it has for air, and which the air will push out of the way and upward until a place above the earth is reached where the attraction of air and gas is equal. A bag of this gas large enough to be pushed upward with a force equal to the weight of the man, plus the weight of the bag, and a little more for lifting power, will carry the man up. This is the principle of the ordinary balloon.

Rising in the air is not flying. It is a necessary step, but real flying is to travel from place to place through the air. To accomplish this, some mechanism, or machinery, is needed to propel the man after he has been lifted into the air. Such machinery will have weight, and the bag of gas must be enlarged to counterbalance it. When this is done, the man and the bag of gas may move through the air, and with suitable rudders he may direct his course. This combination of the lifting bag of gas and the propelling machinery constitutes the dirigible balloon, or airship.

Degen’s apparatus to lift the man and his flying mechanism with the aid of a gas-balloon. See [Chapter IV].

The airship is affected equally with the balloon by prevailing winds. A breeze blowing 10 miles an hour will carry a balloon at nearly that speed in the direction in which it is blowing. Suppose the aeronaut wishes to sail in the opposite direction? If the machinery will propel his airship only 10 miles an hour in a calm, it will virtually stand still in the 10-mile breeze. If the machinery will propel his airship 20 miles an hour in a calm, the ship will travel 10 miles an hour—as related to places on the earth’s surface—against the wind. But so far as the air is concerned, his speed through it is 20 miles an hour, and each increase of speed meets increased resistance from the air, and requires a greater expenditure of power to overcome. To reduce this resistance to the least possible amount, the globular form of the early balloon has been variously modified. Most modern airships have a “cigar-shaped” gas bag, so called because the ends look like the tip of a cigar. As far as is known, this is the balloon that offers less resistance to the air than any other.

Another mechanical means of getting up into the air was suggested by the flying of kites, a pastime dating back at least 2,000 years, perhaps longer. Ordinarily, a kite will not fly in a calm, but with even a little breeze it will mount into the air by the upward thrust of the rushing breeze against its inclined surface, being prevented from blowing away (drifting) by the pull of the kite-string. The same effect will be produced in a dead calm if the operator, holding the string, runs at a speed equal to that of the breeze—with this important difference: not only will the kite rise in the air, but it will travel in the direction in which the operator is running, a part of the energy of the runner’s pull upon the string producing a forward motion, provided he holds the string taut. If we suppose the pull on the string to be replaced by an engine and revolving propeller in the kite, exerting the same force, we have exactly the principle of the aeroplane.

As it is of the greatest importance to possess a clear understanding of the natural processes we propose to use, let us refer to any text-book on physics, and review briefly some of the natural laws relating to motion and force which apply to the problem of flight:

(a) Force is that power which changes or tends to change the position of a body, whether it is in motion or at rest.

(b) A given force will produce the same effect, whether the body on which it acts is acted upon by that force alone, or by other forces at the same time.

(c) A force may be represented graphically by a straight line—the point at which the force is applied being the beginning of the line; the direction of the force being expressed by the direction of the line; and the magnitude of the force being expressed by the length of the line.

(d) Two or more forces acting upon a body are called component forces, and the single force which would produce the same effect is called the resultant.

(e) When two component forces act in different directions the resultant may be found by applying the principle of the parallelogram of forces—the lines (c) representing the components being made adjacent sides of a parallelogram, and the diagonal drawn from the included angle representing the resultant in direction and magnitude.

(f) Conversely, a resultant motion may be resolved into its components by constructing a parallelogram upon it as the diagonal, either one of the components being known.

The Deutsch de la Muerthe dirigible balloon Ville-de-Paris; an example of the “cigar-shaped” gas envelope.

Taking up again the illustration of the kite flying in a calm, let us construct a few diagrams to show graphically the forces at work upon the kite. Let the heavy line AB represent the centre line of the kite from top to bottom, and C the point where the string is attached, at which point we may suppose all the forces concentrate their action upon the plane of the kite. Obviously, as the flyer of the kite is running in a horizontal direction, the line indicating the pull of the string is to be drawn horizontal. Let it be expressed by CD. The action of the air pressure being at right angles to the plane of the kite, we draw the line CE representing that force. But as this is a pressing force at the point C, we may express it as a pulling force on the other side of the kite by the line CF, equal to CE and in the opposite direction. Another force acting on the kite is its weight—the attraction of gravity acting directly downward, shown by CG. We have given, therefore, the three forces, CD, CF, and CG. We now wish to find the value of the pull on the kite-string, CD, in two other forces, one of which shall be a lifting force, acting directly upward, and the other a propelling force, acting in the direction in which we desire the kite to travel—supposing it to represent an aeroplane for the moment.

We first construct a parallelogram on CF and CG, and draw the diagonal CH, which represents the resultant of those two forces. We have then the two forces CD and CH acting on the point C. To avoid obscuring the diagram with too many lines, we draw a second figure, showing just these two forces acting on the point C. Upon these we construct a new parallelogram, and draw the diagonal CI, expressing their resultant. Again drawing a new diagram, showing this single force CI acting upon the point C, we resolve that force into two components—one, CJ, vertically upward, representing the lift; the other, CK, horizontal, representing the travelling power. If the lines expressing these forces in the diagrams had been accurately drawn to scale, the measurement of the two components last found would give definite results in pounds; but the weight of a kite is too small to be thus diagrammed, and only the principle was to be illustrated, to be used later in the discussion of the aeroplane.

Nor is the problem as simple as the illustration of the kite suggests, for the air is compressible, and is moreover set in motion in the form of a current by a body passing through it at anything like the ordinary speed of an aeroplane. This has caused the curving of the planes (from front to rear) of the flying machine, in contrast with the flat plane of the kite. The reasoning is along this line: Suppose the main plane of an aeroplane six feet in depth (from front to rear) to be passing rapidly through the air, inclined upward at a slight angle. By the time two feet of this depth has passed a certain point, the air at that point will have received a downward impulse or compression which will tend to make it flow in the direction of the angle of the plane. The second and third divisions in the depth, each of two feet, will therefore be moving with a partial vacuum beneath, the air having been drawn away by the first segment. At the same time, the pressure of the air from above remains the same, and the result is that only the front edge of the plane is supported, while two-thirds of its depth is pushed down. This condition not only reduces the supporting surface to that of a plane two feet in depth, but, what is much worse, releases a tipping force which tends to throw the plane over backward.

In order that the second section of the plane may bear upon the air beneath it with a pressure equal to that of the first, it must be inclined downward at double the angle (with the horizon) of the first section; this will in turn give to the air beneath it a new direction. The third section of the plane must then be set at a still deeper angle to give it support. Connecting these several directions with a smoothly flowing line without angles, we get the curved line of section to which the main planes of aeroplanes are bent.

With these principles in mind, it is in order to apply them to the understanding of how an aeroplane flies. Wilbur Wright, when asked what kept his machine up in the air—why it did not fall to the ground—replied: “It stays up because it doesn’t have time to fall.” Just what he meant by this may be illustrated by referring to the common sport of “skipping stones” upon the surface of still water. A flat stone is selected, and it is thrown at a high speed so that the flat surface touches the water. It continues “skipping,” again and again, until its speed is so reduced that the water where it touches last has time to get out of the way, and the weight of the stone carries it to the bottom. On the same principle, a person skating swiftly across very thin ice will pass safely over if he goes so fast that the ice hasn’t time to break and give way beneath his weight. This explains why an aeroplane must move swiftly to stay up in the air, which has much less density than either water or ice. The minimum speed at which an aeroplane can remain in the air depends largely upon its weight. The heavier it is, the faster it must go—just as a large man must move faster over thin ice than a small boy. At some aviation contests, prizes have been awarded for the slowest speed made by an aeroplane. So far, the slowest on record is that of 21.29 miles an hour, made by Captain Dickson at the Lanark meet, Scotland, in August, 1910. As the usual rate of speed is about 46 miles an hour, that is slow for an aeroplane; and as Dickson’s machine is much heavier than some others—the Curtiss machine, for instance—it is remarkably slow for that type of aeroplane.

Just what is to be gained by offering a prize for slowest speed is difficult to conjecture. It is like offering a prize to a crowd of boys for the one who can skate slowest over thin ice. The minimum speed is the most dangerous with the aeroplane as with the skater. Other things being equal, the highest speed is the safest for an aeroplane. Even when his engine stops in mid-air, the aviator is compelled to keep up speed sufficient to prevent a fall by gliding swiftly downward until the very moment of landing.

The air surface necessary to float a plane is spread out in one area in the monoplane, and divided into two areas, one above the other and 6 to 9 feet apart, in the biplane; if closer than this, the disturbance of the air by the passage of one plane affects the supporting power of the other. It has been suggested that better results in the line of carrying power would be secured by so placing the upper plane that its front edge is a little back of the rear edge of the lower plane, in order that it may enter air that is wholly free from any currents produced by the rushing of the lower plane.

As yet, there is a difference of opinion among the principal aeroplane builders as to where the propeller should be placed. All of the monoplanes have it in front of the main plane. Most of the biplanes have it behind the main plane; some have it between the two planes. If it is in front, it works in undisturbed air, but throws its wake upon the plane. If it is in the rear, the air is full of currents caused by the passage of the planes, but the planes have smooth air to glide into. As both types of machine are eminently successful, the question may not be so important as it seems to the disputants.

The exact form of curve for the planes has not been decided upon. Experience has proven that of two aeroplanes having the same surface and run at the same speed, one may be able to lift twice as much as the other because of the better curvature of its planes. The action of the air when surfaces are driven through it is not fully understood. Indeed, the form of plane shown in the accompanying figure is called the aeroplane paradox. If driven in either direction it leaves the air with a downward trend, and therefore exerts a proportional lifting power. If half of the plane is taken away, the other half is pressed downward. All of the lifting effect is in the curving of the top side. It seems desirable, therefore, that such essential factors should be thoroughly worked out, understood, and applied.

Section of the “paradox” aeroplane.

Chapter IV.
FLYING MACHINES.

Mythological—Leonardo da Vinci—Veranzio—John Wilkins—Besnier—Marquis de Bacqueville—Paucton—Desforges—Meerwein—Stentzel—Henson—Von Drieberg—Wenham—Horatio Phillips—Sir Hiram Maxim—Lilienthal—Langley—Ader—Pilcher—Octave Chanute—Herring—Hargrave—The Wright brothers—Archdeacon—Santos-Dumont—Voisin—Bleriot.

The term Flying Machines is applied to all forms of aircraft which are heavier than air, and which lift and sustain themselves in the air by mechanical means. In this respect they are distinguished from balloons, which are lifted and sustained in the air by the lighter-than-air gas which they contain.

From the earliest times the desire to fly in the air has been one of the strong ambitions of the human race. Even the prehistoric mythology of the ancient Greeks reflected the idea in the story of Icarus, who flew so near to the sun that the heat melted the wax which fastened his wings to his body, and he fell into the sea.

Perhaps the first historical record in the line of mechanical flight worthy of attention exists in the remarkable sketches and plans for a flying mechanism left by Leonardo da Vinci at his death in 1519. He had followed the model of the flying bird as closely as possible, although when the wings were outspread they had an outline more like those of the bat. While extremely ingenious in the arrangement of the levers, the power necessary to move them fast enough to lift the weight of a man was far beyond the muscular strength of any human being.

It was a century later, in 1617, that Veranzio, a Venetian, proved his faith in his inventive ability by leaping from a tower in Venice with a crude, parachute-like contrivance. He alighted without injury.

In 1684, an Englishman, John Wilkins, then bishop of Chester, built a machine for flying in which he installed a steam-engine. No record exists of its performance.

In 1678, a French locksmith by the name of Besnier devised what seems now a very crude apparatus for making descending flights, or glides, from elevated points. It was, however, at that date considered important enough to be described in the Journal of the Savants. It was a wholly unscientific combination of the “dog-paddle” motion in swimming, with wing areas which collapsed on the upward motion and spread out on the downward thrust. If it was ever put to a test it must have failed completely.

In 1742, the Marquis de Bacqueville constructed an apparatus which some consider to have been based on Besnier’s idea—which seems rather doubtful. He fastened the surfaces of his aeroplane directly to his arms and legs, and succeeded in making a long glide from the window of his mansion across the garden of the Tuileries, alighting upon a washerwoman’s bench in the Seine without injury.

Paucton, the mathematician, is credited with the suggestion of a flying machine with two screw propellers, which he called “pterophores”—a horizontal one to raise the machine into the air, and an upright one to propel it. These were to be driven by hand. With such hopelessly inadequate power it is not surprising that nothing came of it, yet the plan was a foreshadowing of the machine which has in these days achieved success.

The Abbé Desforges gained a place in the annals of aeronautics by inventing a flying machine of which only the name “Orthoptere” remains.

Meerwein’s Flying Machine. A, shows the position of the man in the wings, their comparative size, and the operating levers; B, position when in flight.

About 1780, Karl Friedrich Meerwein, an architect, and the Inspector of Public Buildings for Baden, Germany, made many scientific calculations and experiments on the size of wing surface needed to support a man in the air. He used the wild duck as a standard, and figured that a surface of 126 square feet would sustain a man in the air. This agrees with the later calculations of such experimenters as Lilienthal and Langley. Other of Meerwein’s conclusions are decidedly ludicrous. He held that the build of a man favors a horizontal position in flying, as his nostrils open in a direction which would be away from the wind, and so respiration would not be interfered with! Some of his reasoning is unaccountably astray; as, for instance, his argument that because the man hangs in the wings the weight of the latter need not be considered. It is almost needless to say that his practical trials were a total failure.

Plan of Degen’s apparatus.

The next prominent step forward toward mechanical flight was made by the Australian watchmaker Degen, who balanced his wing surfaces with a small gas balloon. His first efforts to fly not being successful, he abandoned his invention and took to ballooning.

Stentzel, an engineer of Hamburg, came next with a machine in the form of a gigantic butterfly. From tip to tip of its wings it measured 20 feet, and their depth fore and aft was 5½ feet. The ribs of the wings were of steel and the web of silk, and they were slightly concave on the lower side. The rudder-tail was of two intersecting planes, one vertical and the other horizontal. It was operated by a carbonic-acid motor, and made 84 flaps of the wings per minute. The rush of air it produced was so great that any one standing near it would be almost swept off his feet. It did not reach a stage beyond the model, for it was able to lift only 75 lbs.

Stentzel’s machine.

In 1843, the English inventor Henson built what is admitted to be the first aeroplane driven by motive power. It was 100 feet in breadth (spread) and 30 feet long, and covered with silk. The front edge was turned slightly upward. It had a rudder shaped like the tail of a bird. It was driven by two propellers run by a 20-horse-power engine. Henson succeeded only in flying on a down grade, doubtless because of the upward bend of the front of his plane. Later investigations have proven that the upper surface of the aeroplane must be convex to gain the lifting effect. This is one of the paradoxes of flying planes which no one has been able to explain.

In 1845, Von Drieberg, in Germany, revived the sixteenth-century ideas of flying, with the quite original argument that since the legs of man were better developed muscularly than his arms, flying should be done with the legs. He built a machine on this plan, but no successful flights are recorded.

In 1868, an experimenter by the name of Wenham added to the increasing sum of aeronautical knowledge by discovering that the lifting power of a large supporting surface may be as well secured by a number of small surfaces placed one above another. Following up these experiments, he built a flying machine with a series of six supporting planes made of linen fabric. As he depended upon muscular effort to work his propellers, he did not succeed in flying, but he gained information which has been valuable to later inventors.

Von Drieberg’s machine; view from above.

Wenham’s arrangement of many narrow surfaces in six tiers, or decks. a, a, rigid framework; b, b, levers working flapping wings; e, e, braces. The operator is lying prone.

The history of flying machines cannot be written without deferential mention of Horatio Phillips of England. The machine that he made in 1862 resembled a large Venetian blind, 9 feet high and over 21 feet long. It was mounted on a carriage which travelled on a circular track 600 feet long, and it was driven by a small steam engine turning a propeller. It lifted unusually heavy loads, although not large enough to carry a man. It seems to open the way for experiments with an entirely new arrangement of sustaining surfaces—one that has never since been investigated. Phillips’s records cover a series of most valuable experiments. Perhaps his most important work was in the determination of the most advantageous form for the surfaces of aeroplanes, and his researches into the correct proportion of motive power to the area of such surfaces. Much of his results have not yet been put to practical use by designers of flying machines.

Phillips’s Flying Machine—built of narrow slats like a Venetian blind.

The year 1888 was marked by the construction by Sir Hiram Maxim of his great aeroplane which weighed three and one-half tons, and is said to have cost over $100,000. The area of the planes was 3,875 square feet, and it was propelled by a steam engine in which the fuel used was vaporized naphtha in a burner having 7,500 jets, under a boiler of small copper water tubes. With a steam pressure of 320 lbs. per square inch, the two compound engines each developed 180 horse-power, and each turned a two-bladed propeller 17½ feet in diameter. The machine was used only in making tests, being prevented from rising in the air by a restraining track. The thrust developed on trial was 2,164 lbs., and the lifting power was shown to have been in excess of 10,000 lbs. The restraining track was torn to pieces, and the machine injured by the fragments. The dynamometer record proved that a dead weight of 4½ tons, in addition to the weight of the machine and the crew of 4 men, could have been lifted. The stability, speed, and steering control were not tested. Sir Hiram Maxim made unnumbered experiments with models, gaining information which has been invaluable in the development of the aeroplane.

View of a part of Maxim’s aeroplane, showing one of the immense propellers. At the top is a part of the upper plane.

The experiments of Otto Lilienthal in gliding with a winged structure were being conducted at this period. He held that success in flying must be founded upon proficiency in the art of balancing the apparatus in the air. He made innumerable glides from heights which he continually increased until he was travelling distances of nearly one-fourth of a mile from an elevation of 100 feet. He had reached the point where he was ready to install motive power to drive his glider when he met with a fatal accident. Besides the inspiration of his daring personal experiments in the air, he left a most valuable series of records and calculations, which have been of the greatest aid to other inventors in the line of artificial flight.

Lilienthal in his biplane glider.

In 1896, Professor Langley, director of the Smithsonian Institution at Washington, made a test of a model flying machine which was the result of years of experimenting. It had a span of 15 feet, and a length of 8½ feet without the extended rudder. There were 4 sails or planes, 2 on each side, 30 inches in width (fore-and-aft measurement). Two propellers revolving in opposite directions were driven by a steam engine. The diameter of the propellers was 3 feet, and the steam pressure 150 lbs. per square inch. The weight of the machine was 28 lbs. It is said to have made a distance of 1 mile in 1 minute 45 seconds. As Professor Langley’s experiments were conducted in strict secrecy, no authoritative figures are in existence. Later a larger machine was built, which was intended to carry a man. It had a spread of 46 feet, and was 35 feet in length. It was four years in building, and cost about $50,000. In the first attempt to launch it, from the roof of a house-boat, it plunged into the Potomac River. The explanation given was that the launching apparatus was defective. This was remedied, and a second trial made, but the same result followed. It was never tried again. This machine was really a double, or tandem, monoplane. The framework was built of steel tubing almost as thin as writing paper. Every rib and pulley was hollowed out to reduce the weight. The total weight of the engine and machine was 800 lbs., and the supporting surface of the wings was 1,040 square feet. The aeroplanes now in use average from 2 to 4 lbs. weight to the square foot of sustaining surface.

About the same time the French electrician Ader, after years of experimenting, with the financial aid of the French Government, made some secret trials of his machine, which had taken five years to build. It had two bat-like wings spreading 54 feet, and was propelled by two screws driven by a 4-cylinder steam engine which has been described as a marvel of lightness. The inventor claimed that he was able to rise to a height of 60 feet, and that he made flights of several hundred yards. The official tests, however, were unsatisfactory, and nothing further was done by either the inventor or the government to continue the experiments. The report was that in every trial the machines had been wrecked.

The experiments of Lilienthal had excited an interest in his ideas which his untimely death did not abate. Among others, a young English marine engineer, Percy S. Pilcher, took up the problem of gliding flight, and by the device of using the power exerted by running boys (with a five-fold multiplying gear) he secured speed enough to float his glider horizontally in the air for some distance. He then built an engine which he purposed to install as motive power, but before this was done he was killed by a fall from his machine while in the air.

Plan of Chanute’s movable-wing glider.

Before the death of Lilienthal his efforts had attracted the attention of Octave Chanute, a distinguished civil engineer of Chicago, who, believing that the real problem of the glider was the maintenance of equilibrium in the air, instituted a series of experiments along that line. Lilienthal had preserved his equilibrium by moving his body about as he hung suspended under the wings of his machine. Chanute proposed to accomplish the same end by moving the wings automatically. His attempts were partially successful. He constructed several types of gliders, one of these with two decks exactly in the form of the present biplane. Others had three or more decks. Upward of seven hundred glides were made with Chanute’s machines by himself and assistants, without a single accident. It is of interest to note that a month before the fatal accident to Lilienthal, Chanute had condemned that form of glider as unsafe.

Chanute’s two-deck glider.

In 1897, A. M. Herring, who had been one of the foremost assistants of Octave Chanute, built a double-deck (biplane) machine and equipped it with a gasoline motor between the planes. The engine failed to produce sufficient power, and an engine operated by compressed air was tried, but without the desired success.

In 1898, Lawrence Hargrave of Sydney, New South Wales, came into prominence as the inventor of the cellular or box kite. Following the researches of Chanute, he made a series of experiments upon the path of air currents under variously curved surfaces, and constructed some kites which, under certain conditions, would advance against a wind believed to be absolutely horizontal. From these results Hargrave was led to assert that “soaring sails” might be used to furnish propulsion, not only for flying machines, but also for ships on the ocean sailing against the wind. The principles involved remain in obscurity.

During the years 1900 to 1903, the brothers Wright, of Dayton, Ohio, had been experimenting with gliders among the sand dunes of Kitty Hawk, North Carolina, a small hamlet on the Atlantic Coast. They had gone there because the Government meteorological department had informed them that at Kitty Hawk the winds blew more steadily than at any other locality in the United States. Toward the end of the summer of 1903, they decided that the time was ripe for the installation of motive power, and on December 17, 1903, they made their first four flights under power, the longest being 853 feet in 59 seconds—against a wind blowing nearly 20 miles an hour, and from a starting point on level ground.

Wilbur Wright gliding at Kitty Hawk, N. C., in 1903.

During 1904 over one hundred flights were made, and changes in construction necessary to sail in circles were devised. In 1905, the Wrights kept on secretly with their practice and development of their machine, first one and then the other making the flights until both were equally proficient. In the latter part of September and early part of October, 1905, occurred a series of flights which the Wrights allowed to become known to the public. At a meeting of the Aeronautical Society of Great Britain, held in London on December 15, 1905, a letter from Orville Wright to one of the members was read. It was dated November 17, 1905, and an excerpt from it is as follows:

“During the month of September we gradually improved in our practice, and on the 26th made a flight of a little over 11 miles. On the 30th we increased this to 12⅕th miles; on October 3, to 15⅓ miles; on October 4, to 20¾ miles, and on October 5, to 24¼ miles. All these flights were made at about 38 miles an hour, the flight of October 5 occupying 30 minutes 3 seconds. Landings were caused by the exhaustion of the supply of fuel in the flights of September 26 and 30, and October 8, and in those of October 3 and 4 by the heating of the bearings in the transmission, of which the oil cups had been omitted. But before the flight on October 5, oil cups had been fitted to all the bearings, and the small gasoline can had been replaced with one that carried enough fuel for an hour’s flight. Unfortunately, we neglected to refill the reservoir just before starting, and as a result the flight was limited to 38 minutes....

A Wright machine in flight.

“The machine passed through all of these flights without the slightest damage. In each of these flights we returned frequently to the starting point, passing high over the heads of the spectators.”

These statements were received with incredulity in many parts of Europe, the more so as the Wrights refused to permit an examination of their machine, fearing that the details of construction might become known before their patents were secured.

The Archdeacon machine on the Seine.

During the summer of 1905, Captain Ferber and Ernest Archdeacon of Paris had made experiments with gliders. One of the Archdeacon machines was towed by an automobile, having a bag of sand to occupy the place of the pilot. It rose satisfactorily in the air, but the tail became disarranged, and it fell and was damaged. It was rebuilt and tried upon the waters of the Seine, being towed by a fast motor-boat at a speed of 25 miles an hour. The machine rose about 50 feet into the air and sailed for about 500 feet.

Archdeacon gathered a company of young men about him who speedily became imbued with his enthusiasm. Among them were Gabriel Voisin, Louis Bleriot, and Leon Delagrange. The two former, working together, built and flew several gliders, and when Santos-Dumont made his historic flight of 720 feet with his multiple-cell machine on November 13, 1906 (the first flight made in Europe), they were spurred to new endeavors.

Within a few months Voisin had finished his first biplane, and Delagrange made his initial flight with it—a mere hop of 30 feet—on March 16, 1907.

Bleriot, however, had his own ideas, and on August 6, 1907, he flew for 470 feet in a monoplane machine of the tandem type. He succeeded in steering his machine in a curved course, a feat which had not previously been accomplished in Europe.

In October of the same year, Henri Farman, then a well-known automobile driver, flew the second Voisin biplane in a half circle of 253 feet—a notable achievement at that date.

But Santos-Dumont had been pushing forward several different types of machines, and in November he flew first a biplane 500 feet, and a few days later a monoplane 400 feet.

At this point in our story the past seems to give place to the present. The period of early development was over, and the year 1908 saw the first of those remarkable exploits which are recorded in the chapter near the end of this work entitled, “Chronicle of Aviation Achievements.”

It is interesting to note that the machines then brought out are those of to-day. Practically, it may be said that there has been no material change from the original types. More powerful engines have been put in them, and the frames strengthened in proportion, but the Voisin, the Bleriot, and the Wright types remain as they were at first. Other and later forms are largely modifications and combinations of their peculiar features.

Chapter V.
FLYING MACHINES: THE BIPLANE.

Successful types of aeroplanes—Distinguishing features—The Wright biplane—Construction—New type—Five-passenger machine—The Voisin biplane—New racing type—The Curtiss biplane—The Cody biplane—The Sommer biplane—The Baldwin biplane—New stabilizing plane—The Baddeck No. 2—Self-sustaining radiator—The Herring biplane—Stabilizing fins.

In the many contests for prizes and records, two types of flying machines have won distinctive places for themselves—the biplane and the monoplane. The appearance of other forms has been sporadic, and they have speedily disappeared without accomplishing anything which had not been better done by the two classes named.

This fact, however, should not be construed as proving the futility of all other forms, nor that the ideal flying machine must be of one of these two prominent types. It is to be remembered that record-making and record-breaking is the most serious business in which any machines have so far been engaged; and this, surely, is not the field of usefulness to humanity which the ships of the air may be expected ultimately to occupy. It may yet be proved that, successful as these machines have been in what they have attempted, they are but transition forms leading up to the perfect airship of the future.

The Wright biplane in flight.

The distinguishing feature of the biplane is not alone that it has two main planes, but that they are placed one above the other. The double (or tandem) monoplane also has two main planes, but they are on the same level, one in the rear of the other.

A review of the notable biplanes of the day must begin with the Wright machine, which was not only the first with which flights were made, but also the inspiration and perhaps the pattern of the whole succeeding fleet.

THE WRIGHT BIPLANE.

The Wright biplane is a structure composed of two main surfaces, each 40 feet long and 6 feet 6 inches wide, set one above the other, parallel, and 6 feet apart. The planes are held rigidly at this distance by struts of wood, and the whole structure is trussed with diagonal wire ties. It is claimed by the Wrights that these dimensions have been proven by their experiments to give the maximum lift with the minimum weight.

Diagram showing the construction of the Wright biplane. The lever R is connected by the bar A with the rudder gearing C, and is pivoted at the bottom on a rolling shaft B, through which the warping wires W¹, W² are operated. The semicircular planes F aid in stabilizing the elevator system.

The combination of planes is mounted on two rigid skids, or runners (similar to the runners of a sleigh), which are extended forward and upward to form a support for a pair of smaller planes in parallel, used as the elevator (for directing the course of the aeroplane upward or downward). It has been claimed by the Wrights that a rigid skid under-structure takes up the shock of landing, and checks the momentum at that moment, better than any other device. But it necessitated a separate starting apparatus, and while the starting impulse thus received enabled the Wrights to use an engine of less power (to keep the machine going when once started), and therefore of less dead weight, it proved a handicap to their machines in contests where they were met by competing machines which started directly with their own power. A later model of the Wright biplane is provided with a wheeled running gear, and an engine of sufficient power to raise it in the air after a short run on the wheels.

Two propellers are used, run by one motor. They are built of wood, are of the two-bladed type, and are of comparatively large diameter—8 feet. They revolve in opposite directions at a speed of 450 revolutions per minute, being geared down by chain drive from the engine speed of 1,500 revolutions per minute.

The large elevator planes in front have been a distinctive feature of the Wright machine. They have a combined area of 80 square feet, adding that much more lifting surface to the planes in ascending, for then the under side of their surfaces is exposed to the wind. If the same surfaces were in the rear of the main planes their top sides would have to be turned to the wind when ascending, and a depressing instead of a lifting effect would result.

To the rear of the main planes is a rudder composed of two parallel vertical surfaces for steering to right or left.

The feature essential to the Wright biplane, upon which the letters patent were granted, is the flexible construction of the tips of the main planes, in virtue of which they may be warped up or down to restore disturbed equilibrium, or when a turn is to be made. This warping of the planes changes the angle of incidence for the part of the plane which is bent. (The angle of incidence is that which the plane makes with the line in which it is moving. The bending downward of the rear edge would enlarge the angle of incidence, in that way increasing the compression of the air beneath, and lifting that end of the plane.) The wing-warping controls are actuated by the lever at the right hand of the pilot, which also turns the rudder at the rear—that which steers the machine to right or to left. The lever at the left hand of the pilot moves the elevating planes at the front of the machine.

Sketch showing relative positions of planes and of the operator in the Wright machine: A, A, the main planes; B, B, the elevator planes. The motor is placed beside the operator.

The motor has 4 cylinders, and develops 25 to 30 horse-power, giving the machine a speed of 39 miles per hour.

A newer model of the Wright machine is built without the large elevating planes in front, a single elevating plane being placed just back of the rear rudder. This arrangement cuts out the former lifting effect described above, and substitutes the depressing effect due to exposing the top of a surface to the wind.

Courtesy of N. Y. Times.

The new model Wright biplane—without forward elevator.

The smallest of the Wright machines, popularly called the “Baby Wright,” is built upon this plan, and has proven to be the fastest of all the Wright series.

THE VOISIN BIPLANE.

While the Wrights were busily engaged in developing their biplane in America, a group of enthusiasts in France were experimenting with gliders of various types, towing them with high speed automobiles along the roads, or with swift motor-boats upon the Seine. As an outcome of these experiments, in which they bore an active part, the Voisin brothers began building the biplanes which have made them famous.

As compared with the Wright machine, the Voisin aeroplane is of much heavier construction. It weighs 1,100 pounds. The main planes have a lateral spread of 37 feet 9 inches, and a breadth of 7 feet, giving a combined area of 540 square feet, the same as that of the Wright machine. The lower main plane is divided at the centre to allow the introduction of a trussed girder framework which carries the motor and propeller, the pilot’s seat, the controlling mechanism, and the running gear below; and it is extended forward to support the elevator. This is much lower than in the Wright machine, being nearly on the level of the lower plane. It is a single surface, divided at the centre, half being placed on each side of the girder. It has a combined area of 42 square feet, about half of that of the Wright elevator, and it is only 4 feet from the front edge of the main planes, instead of 10 feet as in the Wright machine. A framework nearly square in section, and about 25 feet long, extends to the rear, and supports a cellular, or box-like, tail, which forms a case in which is the rudder surface for steering to right or to left.

Diagram showing details of construction of the Voisin biplane. C, C, the curtains forming the stabilizing cells.

A distinctive feature of the Voisin biplane is the use of four vertical planes, or curtains, between the two main planes, forming two nearly square “cells” at the ends of the planes.

At the rear of the main planes, in the centre, is the single propeller. It is made of steel, two-bladed, and is 8 feet 6 inches in diameter. It is coupled directly to the shaft of the motor, making with it 1,200 revolutions per minute. The motor is of the V type, developing 50 horse-power, and giving a speed of 37 miles per hour.

Diagram showing the simplicity of control of the Voisin machine, all operations being performed by the wheel and its sliding axis.

The controls are all actuated by a rod sliding back and forth horizontally in front of the pilot’s seat, having a wheel at the end. The elevator is fastened to the rod by a crank lever, and is tilted up or down as the rod is pushed forward or pulled back. Turning the wheel from side to side moves the rudder in the rear. There are no devices for controlling the equilibrium. This is supposed to be maintained automatically by the fixed vertical curtains.

Voisin biplanes at the starting line at Rheims in August, 1909. They were flown by Louis Paulhan, who won third prize for distance, and Henri Rougier, who won fourth prize for altitude. In the elimination races to determine the contestants for the Bennett Cup, Paulhan won second place with the Voisin machine, being defeated only by Tissandier with a Wright machine. Other noted aviators who fly the Voisin machine are M. Bunau-Varilla and the Baroness de la Roche.

The machine is mounted on two wheels forward, and two smaller wheels under the tail.

This description applies to the standard Voisin biplane, which has been in much favor with many of the best known aviators. Recently the Voisins have brought out a new type in which the propeller has been placed in front of the planes, exerting a pulling force upon the machine, instead of pushing it as in the earlier type. The elevating plane has been removed to the rear, and combined with the rudder.

A racing type also has been produced, in which the vertical curtains have been removed and a parallel pair of long, narrow ailerons introduced between the main planes on both sides of the centre. This machine, it is claimed, has made better than 60 miles per hour.

The first Voisin biplane was built for Delagrange, and was flown by him with success.

THE FARMAN BIPLANE.

The second biplane built by the Voisins went into the hands of Henri Farman, who made many flights with it. Not being quite satisfied with the machine, and having an inventive mind, he was soon building a biplane after his own designs, and the Farman biplane is now one of the foremost in favor among both professional and amateur aviators.

It is decidedly smaller in area of surface than the Wright and Voisin machines, having but 430 square feet in the two supporting planes. It has a spread of 33 feet, and the planes are 7 feet wide, and set 6 feet apart. In the Farman machine the vertical curtains of the Voisin have been dispensed with. The forward elevator is there, but raised nearly to the level of the upper plane, and placed 9 feet from the front edge of the main planes. To control the equilibrium, the two back corners of each plane are cut and hinged so that they hang vertically when not in flight. When in motion these flaps or ailerons stream out freely in the wind, assuming such position as the speed of the passing air gives them. They are pulled down by the pilot at one end or the other, as may be necessary to restore equilibrium, acting in very much the same manner as the warping tips of the Wright machine. A pair of tail planes are set in parallel on a framework about 20 feet in the rear of the main planes, and a double rudder surface behind them. Another model has hinged ailerons on these tail planes, and a single rudder surface set upright between them. These tail ailerons are moved in conjunction with those of the main planes.

The Farman biplane, showing the position of the hinged ailerons when at rest. At full speed these surfaces stream out in the wind in line with the planes to which they are attached.

Diagram of the Farman biplane. A later type has the hinged ailerons also on the tail planes.

The motor has 4 cylinders, and turns a propeller made of wood, 8 feet 6 inches in diameter, at a speed of 1,300 revolutions per minute—nearly three times as fast as the speed of the Wright propellers, which are about the same size. The propeller is placed just under the rear edge of the upper main plane, the lower one being cut away to make room for the revolving blades. The motor develops 45 to 50 horse-power, and drives the machine at a speed of 41 miles per hour.

The “racing Farman” is slightly different, having the hinged ailerons only on one of the main planes. The reason for this is obvious. Every depression of the ailerons acts as a drag on the air flowing under the planes, increasing the lift at the expense of the speed.

Sketch of Farman machine, showing position of operator. A, A, main planes; B, elevator; C, motor; P, tail planes.

The whole structure is mounted upon skids with wheels attached by a flexible connection. In case of a severe jar, the wheels are pushed up against the springs until the skids come into play.

The elevator and the wing naps are controlled by a lever at the right hand of the pilot. This lever moves on a universal joint, the side-to-side movement working the flaps, and the forward-and-back motion the elevator. Steering to right or left is done with a bar operated by the feet.

Henri Farman carrying a passenger across country.

Farman has himself made many records with his machine, and so have others. With a slightly larger and heavier machine than the one described, Farman carried two passengers a distance of 35 miles in one hour.

THE CURTISS BIPLANE.

This American rival of the Wright biplane is the lightest machine of this type so far constructed. The main planes are but 29 feet in spread, and 4 feet 6 inches in width, and are set not quite 5 feet apart. The combined area of the two planes is 250 square feet. The main planes are placed midway of the length of the fore-and-aft structure, which is nearly 30 feet. At the forward end is placed the elevator, and at the rear end is the tail—one small plane surface—and the vertical rudder surface in two parts, one above and the other below the tail plane. Equilibrium is controlled by changing the slant of two small balancing planes which are placed midway between the main planes at the outer ends, and in line with the front edges. These balancing planes are moved by a lever standing upright behind the pilot, having two arms at its upper end which turn forward so as to embrace his shoulders. The lever is moved to right or to left by the swaying of the pilot’s body.

Glenn H. Curtiss in his machine ready to start. The fork of the balancing lever is plainly seen at his shoulders. Behind him is the radiator, with the engine still further back.

The motor is raised to a position where the shaft of the propeller is midway between the levels of the main planes, and within the line of the rear edges, so that they have to be cut away to allow the passing of the blades. The motor is of the V type, with 8 cylinders. It is 30 horse-power and makes 1,200 revolutions per minute. The propeller is of steel, two-bladed, 6 feet in diameter, and revolves at the same speed as the shaft on which it is mounted. The high position of the engine permits a low running gear. There are two wheels under the rear edges of the main planes, and another is placed half-way between the main planes and the forward rudder, or elevator. A brake, operated by the pilot’s foot, acts upon this forward wheel to check the speed at the moment of landing.

Another type of Curtiss machine has the ailerons set in the rear of the main planes, instead of between them.

The Curtiss is the fastest of the biplanes, being excelled in speed only by some of the monoplanes. It has a record of 51 miles per hour.

THE CODY BIPLANE.

The Cody biplane has the distinction of being the first successful British aeroplane. It was designed and flown by Captain S. F. Cody, at one time an American, but for some years an officer in the British army.

It is the largest and heaviest of all the biplanes, weighing about 1,800 lbs., more than three times the weight of the Curtiss machine. Its main planes are 52 feet in lateral spread, and 7 feet 6 inches in width, and are set 9 feet apart. The combined area of these sustaining surfaces is 770 square feet. The upper plane is arched, so that the ends of the main planes are slightly closer together than at the centre.

The elevator is in two parts placed end to end, about 12 feet in front of the main planes. They have a combined area of 150 square feet. Between them and above them is a small rudder for steering to right or left in conjunction with the large rudder at the rear of the machine. The latter has an area of 40 square feet.

There are two small balancing planes, set one at each end of the main planes, their centres on the rear corner struts, so that they project beyond the tips of the planes and behind their rear lines.

The Cody biplane in flight. Captain Cody has both hands raised above his head, showing the automatic stability of his machine.

The biplane is controlled by a lever rod having a wheel at the end. Turning the wheel moves the rudders; pushing or pulling the wheel works the elevator; moving the wheel from side to side moves the balancing planes.

There are two propellers, set one on each side of the engine, and well forward between the main planes. They are of wood, of the two-bladed type, 7 feet in diameter. They are geared down to make 600 revolutions per minute. The motor has 8 cylinders and develops 80 horse-power at 1,200 revolutions per minute.

The machine is mounted on a wheeled running gear, two wheels under the front edge of the main planes and one a short distance forward in the centre. There is also a small wheel at each extreme end of the lower main plane.

The Cody biplane has frequently carried a passenger, besides the pilot, and is credited with a speed of 38 miles per hour.

The first aeroplane flights ever made in England were by Captain Cody on this biplane, January 2, 1909.

THE SOMMER BIPLANE.

The Sommer biplane is closely similar to the Farman machine, but has the hinged ailerons only on the upper plane. Another difference is that the tail has but one surface, and the rudder is hung beneath it. Its dimensions are:—Spread of main planes, 34 feet; depth (fore-and-aft), 6 feet 8 inches; they are set 6 feet apart. The area of the main planes is 456 square feet; area of tail, 67 square feet; area of rudder, 9 square feet. It is driven by a 50-horsepower Gnome motor, turning an 8-foot, two-bladed propeller.

M. Sommer has flown with three passengers, a total weight of 536 lbs., besides the weight of the machine.

THE BALDWIN BIPLANE.

The Baldwin biplane, designed by Captain Thomas S. Baldwin, the distinguished balloonist, resembles the Farman type in some features, and the Curtiss in others. It has the Curtiss type of ailerons, set between the wings, but extending beyond them laterally. The elevator is a single surface placed in front of the machine, and the tail is of the biplane type with the rudder between. The spread of the main planes is 31 feet 3 inches, and their depth 4 feet 6 inches. A balancing plane of 9 square feet is set upright (like a fin) above the upper main plane, on a swivel. This is worked by a fork fitting on the shoulders of the pilot, and is designed to restore equilibrium by its swinging into head-resistance on one side or the other as may be necessary.

The Baldwin biplane, showing balancing plane above upper main plane.

The motive power is a 4-cylinder Curtiss motor, which turns a propeller 7 feet 6 inches in diameter, set just within the rear line of the main planes, which are cut away to clear the propeller blades.

THE BADDECK BIPLANE.

The newest biplane of the Aerial Experiment Association follows in general contour its successful precursor, the “Silver Dart,” with which J. A. D. McCurdy made many records. The “Baddeck No. 2” is of the biplane type, and both the planes are arched toward each other. They have a spread of 40 feet, and are 7 feet in depth at the centre, rounding to 5 feet at the ends, where the wing tips, 5 feet by 5 feet, are hinged. The elevator is also of the biplane type, two surfaces each 12 feet long and 28 inches wide, set 30 inches apart. This is mounted 15 feet in front of the main planes. The tail is mounted 11 feet in the rear of the main planes, and is the same size and of the same form as the elevator.

The controls are operated by the same devices as in the Curtiss machine. The propeller is 7 feet 8 inches in diameter, and is turned by a six-cylinder automobile engine of 40 horse-power running at 1,400 revolutions per minute. The propeller is geared down to run at 850 revolutions per minute. The motor is placed low down on the lower plane, but the propeller shaft is raised to a position as nearly as possible that of the centre of resistance of the machine. The speed attained is 40 miles per hour.

The McCurdy biplane, “Baddeck No. 2.”

A unique feature of the mechanism is the radiator, which is built of 30 flattened tubes 7 feet 6 inches long, and 3 inches wide, and very thin. They are curved from front to rear like the main planes, and give sufficient lift to sustain their own weight and that of the water carried for cooling the cylinders. The running gear is of three wheels placed as in the Curtiss machine. The “Baddeck No. 2” has made many satisfactory flights with one passenger besides the pilot.

THE HERRING BIPLANE.

At the Boston Aircraft Exhibition in February, 1910, the Herring biplane attracted much attention, not only because of its superiority of mechanical finish, but also on account of its six triangular stabilizing fins set upright on the upper plane. Subsequent trials proved that this machine was quite out of the ordinary in action. It rose into the air after a run of but 85 feet, and at a speed of only 22 miles per hour, and made a 40-degree turn at a tipping angle of 20 degrees. As measured by the inventor, the machine rose in the air with the pilot (weighing 190 lbs.), with a thrust of 140 lbs., and required only a thrust of from 80 to 85 lbs. to keep it flying.

The spread of the planes is 28 feet, and they are 4 feet in depth, with a total supporting surface of 220 feet. A 25 horse-power Curtiss motor turns a 4-bladed propeller of 6 feet diameter and 5-foot pitch (designed by Mr. Herring) at the rate of 1,200 revolutions per minute.

The L. A. W. (League of American Wheelmen) biplane at the Boston Aircraft Exhibition, February, 1910. Note the peculiar curve of the divided planes. The motor is of the rotating type, of 50 horse-power.

The elevator consists of a pair of parallel surfaces set upon hollow poles 12 feet in front of the main planes. The tail is a single surface.

The stabilizing fins act in this manner: when the machine tips to one side, it has a tendency to slide down an incline of air toward the ground. The fins offer resistance to this sliding, retarding the upper plane, while the lower plane slides on and swings as a pendulum into equilibrium again.

THE BREGUET BIPLANE.

The Breguet biplane is conspicuous in having a biplane tail of so large an area as to merit for the machine the title “tandem biplane.” The main planes have a spread of 41 feet 8 inches, and an area of 500 square feet. The tail spreads 24 feet, and its area is about 280 square feet. The propeller is three-bladed, 8 feet in diameter, and revolves at a speed of 1,200 revolutions per minute. It is placed in front of the main plane, after the fashion of the monoplanes. The motive power is an 8-cylinder R-E-P engine, developing 55 horse-power.

Courtesy of N. Y. Sun.

The Seddon tandem biplane, constructed by Lieutenant Seddon of the British Navy. The area of its planes is 2,000 square feet. Compare its size with that of the monoplane in the background. It is intended to carry ten persons.