The Problem of Air Flight

New Zealand Graphic, Volume XL, Issue 5, 1 February 1908, Page 5

The Problem of Air Flight

A cablegram from London the other day announced that a kite invented by Professor Bell iiad lifted a man to a height of one hundred feet in the air. On this page are several pictures illustrating the mechanism of the Professor’s kite, which is widely different from all the other machines by which it is hoped to conquer the air. It is interesting to trace the evolution of the airship up to the present time and note the multiplicity of ideas that have been at work on this fascinating problem. By two decades, writes Waldemar Kaempffert

in the ‘’Cosmopolitan .Magazine.” of almost disheartening failure attended with the sacrifice of human life the inventor of Hying-machines has been taught that he mav hope to navigate the air by four possible methods. He may raise himself bv means of a gas which will float in air. and urge himself forward by means of propellers, he lay mechanically imitate a bird by designing a machine with dapping wings; he may employ the lifting power of a swiftly revolving screw, and literally hurl himself from the earth: or he mav rely on an aeroplane, and sail the air like an eagle on tile wing. 1 Ims far the floating gas and the aeroplane have embodied the only noteworthy solutions of the problem. Because it offers the readiest and most obvious means of overcoming gravitation, the balloon-like air-ship lias been more highly developed than any other type of aerial craft. By a curious anomaly, it is the most successful and th least 1.1tional vessel which has thus far been devised for the navigation of the air. Reduced to its essential elements, the airship is-merely an elongated bubble of o-as sent forward by the aid of an enginedriven propeller and steered by a itiddei much like that of a ship. (liven a sufficient volume of gas and an envelope strong enough to contain it. theie is. theoreticall v. no limit to the weight that mav be lifted. It is in the provision of a motor able to propel the floating structure against a strong opposing wind that the dilbeultv lies. Assuming that a velocity of thirty miles an hour can be attained in absolutely calm air. it follows that in a thirtv-mile breeze the airship will stand still, even though the propellers arc churning the air with their maximum ellieieney. S| of propul sion rather than dirigibility and lifting

power, is the chief object of research at present, and speed can hardly be attained with the resistance ottered by so enormous a surface as that of a gas-bag. The first motor-driven dirigible air-ship of the balloon type that ever succeeded in returning to its starting-point was the historic La Erance, built by two French army officers, Captains Renard and Krebs, twenty-three yrars ago. On the seven occasions when it was publicly tested, the vessel succeeded in returning to its shed five times—achievements which have not been surpassed by similar

craft in our own day. Its speed was only fourteen miles an hour. Pioneers though they were. Renard and Krebs equipped their craft WTtli (‘very appurtenance that has since been considered an indispensable part of an air-ship’s outfit. The balloon was kept distended by an inner bag filled with air: a frame 128 feet long, fashioned into a car. stiffened the entire structure; the rudder was mounted in a position which later experience proves to have been selected with excellent judgment; the lines of the gasbag were so admirably drawn, (‘ither bv accident or design, that they may be considered a felicitous anticipation of modern practice; and the propeller was mounted at the front end of the car as it is in the most modern types. Later airships, although bigger and faster, have not considerably improved on the famous La France. To Santos-Dumont credit is due for having popularised the airship. It remained for him to apply the light gasolene motor of the automobile to the dirigible balloon. He has sailed in more than a dozen dirigible balloons varying in length from fifty to 1(H) feet, all patterned after Tai France, and most of them successful vehicles of th.ir kind. His aerial triumphs are familiar to <*v< ryone. Most notable among them is his winning of the Deutsch prize by sailing three and a-half miles and return in Lalf-an-hour. By far the most ambitious and daring of dirigible-balloon designers is Count von Zeppelin, a German military officer who astonished the world seven years ago by constructing a ship 420 f.*ct long — in other words, a craft as big as many an ocean-steamer. Its immensity was in itself a great element of success, for

the larger the volume of gas the larger and inon l powerful tin* motor tiiat can Im* carried. From his colossal cylind. r of gas Von Zeppelin supeiided two cars, and placed a motor in each. If one motor gave way he had the other to fall back upon. Like a ship’s hold, the envelope was divided into vompartincuts, ,*ach of which could be tilled and emptied separately. the purpose being io prevent a total loss of gas if the outer covering were uiptured. A still aluminum frame of braced rings maintained the rigidity of the envelope and took the place of the internal air-bag of the French air-ships. Promising as this first attempt of \ on Zeppelin’s was. it only partially realised its inventor’s hopes. Von Zeppelin’s latest air-ship, which is about ten feet shorter than the first, is planned on the same lines, but is equipped with more powerful motors. By far the speediest dirigible balloon ever constructed, it has sailed over Lake Constance in Switzerland at the rate of thirty-three and ahalf miles an hour on on,* of its brief Hights. Its radius of action is truly remarkable. With both motors running at full speed it should travel sixty hours and cover eighteen hundred miles at thirtv miles an hour and carry between seven and eight tons in addition to its own w. ight. all with the usual proviso th.it its career be not checked by too blustering a wind. With one motor it should travel 120 hours al twenty-live miles an hour and covin' three thousand miles. Such long journeys are as yet mei.lv theoretical, indeed, almost visionary. w hen it is considered that t here are very few days in the year when the w.nd is not blowing al tin* rate of twenty miles an hour in the upper r. gions of tlu* atmosphere. Nevertheless. \on Zeppelin dreams of transatlantic vessels built according to his id.as. and ot war-ships

leisurelv dropping shells into an enemy’s ca inp. That some military use of the dirigible balloon is seriously contemplated by France and Germany at least, is indi catod by the elaborately . quipped aero nautic divisions of their respective armies. France has actually adopted a programme for tin* construction ot a large licet of airships, the first five of which are to Io in commission by March. 1008. These military machines are all

to be modelled after La Patrie, which the French Government has puicliascd from its designers, the Lebaudx broth is. In speed. La Patrie is nearlx equal to Von Zeppelin’s colossus; in dii igibilitx the ship is one of the most perfect ever con st i net. d. So admirably has it been plann cd that in good weather it can Im* steered perfectly in every direction and driven at a speed of thirty miles an hour. With a crew of thro* men. La Patrie carries 1870 pounds ot ballast; with a crew of seven men. 1120 pounds of ballast. Germany has adopted a typ? of aerostat devised bx Major von Parseval for the express purpose of attaining ease of transportation in time of war. The only rigid part of his balloon is a twenty-foot car hung from a collapsible bag 158 feet long. A single two horse waggon can icadily carry th.* deflated airship. In speed. Von Paseval’s war-ship is a match lor La Patrie. Very slowly the aeronaut is abandoning tlu* gas-bag and turning to the more promising machines which are heavier than the air. Because the gas-lifted air-ship has v. ry nearly reached the end of itdevelopment, it is likely that the machine of the* future will he projected on the principle of Cue soaring bird. An aeroplane may be defined as a sulfate pro] died horizontally in such a manner that the resulting pressure of air from beneath prevents its falling. A balloon can remain stationary over a given spot in a calm, but an aeroplane must be k. pt in motion if it is to remain in the air. Such a plane literally runs <ui tin* air like a skater gliding over thin ice. The most familiar example of an aeroplane is the kite of our boyhood days. W e all remember how w. • kept it alolt even in a light br.czc by running with it against the wind. Substitute the pull of a propeller for the cord, and the

aeroplane living machine is ereat.d. It this weie all. the problem of art I licial llight would Im x e been *olx cd long ago. There remains the sii premely difficult art of bal iming the plain* so that it will skate on an even keel. Even birds find it hard to maintain this stability. In tae constant el fort to steadx himself a hawk sways

fyom side to side as he soars, like an acfobat on a tight rope. Occasionally a bird will catch the wind on top of his wing, with the result that he will capsize and fall some distance before he can recover himself. If the living aeroplanes of nature find the feat of balancing so difficult, is it any wonder that men have been killed in endeavouring Ito discover their secret? If you have ever sailed a canoe you will readily understand what this task of balancing an aeroplane really means. As the pressure of the wind on your sail hee's your canoe over, you must climb out on the outrigger far enough for your weight to counterbalance the wind pressure so that you will not be •upset. The physicist scientifically explains your achievement by stating that you ‘have suceeded in keeping the centre of air pressure and the centre of gravity on the same straight line. In a canoe the feat is comparatively easy; in an aeroplane it demands constant and flashlike shifting of the body, because the sudden slight variations of the wind must be immediately opposed. It happened that, the first modern experimenter with the aeroplane met a tragic death after he hud succeeded in making over 2000 short flights in a gliding machine of his own invention, simply because he was not quick enough in so throwing his weight that the centres of air pressure and gravity coincided. He vvas an engineer named Otto ■Lilienthal. Birds were to him the possessors of a secret which he felt that scientific study could reveal. Accordingly he spent most of his days on the roofs of the Prussian vi'lage of Rhinow with a whole colony of storks. He studied them as if they were animated flying machines. After some practical tests lie invented a bat-like apparatus composed of a pair of fixed arch wings and a tail-like rudder. Clutching the horizontal bar to which the wings were fastened, he would run down a hill against the wind and launch himself by leaping a few feet into the air. In this manner he could soar lor two or three hundred feet, upheld-merely by the pressure of the air beneath the outstretched wings. In order to maintain his equilibrium he was compelled to shift his .weight almost constantly eo that the centre of gravity coincided with the centre of air pressure. Since they rarely remain coincident for more than a second. because the centre of air pressure is constantly changing, Lilienthal had to exercise considerable agility to keep his centre of gravity pursuing the centre of air pressure, which accounts for the apparently crazy antics he used to perform in flight. Pilcher, an Englishman, elightly improved on Lilienthal’s apparatus, and after several hundred flights came to a similar violent end. Crude as LilienthaPs machine undoubtedly was, it startled the world when its first flights were made. It taught the scientific investigator of the prob'em much that he had never even suspected anil laid the foundation for later American researches. Whjle Lilienthal was conducting his venturesome inquiry, Sir Hiram Maxim the inventor of the machine gun that bears his name, courageously set about the construction of the biggest aeroplane flying machine ever laid down, and that, moreover, at a time when practically nothing was known of the science of aerodynamics. Maxim is probably the most brilliant mechanic of our day. for which reason it is not to be wondered at that his contrivance was a marvel of planes and screws. After some investigations he formulated a plan of machine. which, although decidedly defective in the light of subsequently acquired knowledge, was the very embodiment of Yankee inventive genius. His aerial ship consisted of a huge central plane with a surface of some fourteen hundred square feet, and of fixed sije wings and steering-planes fore and aft. all taken together having a total area of four thousand square feet. ' r he total width of this enormous syste.-n was 104 feet, and its length 125 feet. • It had a lifting capacity of eight thousand pounds. Twelve years ago there wks no light propelling-machinery to be bought. Maxim consequently invented’ a new steam-boiler and a steam engine, both Of which to this day remain marvels.

The engine was of 363 horse-power, operated by steam at 275 pounds pressure. It drove two propellers each nearly 18 feet in diameter. In order that it might attain sufficient speed to rise in the air the entire machine was mounted on wheels -running on a railway track of eightfoot gage. Wisely hesitating to trust himself in the air before learning more of the mysteries of free flight, Maxim prevented his machine from unduly rising by wooden guard rails. At a speed of thirty-six miles an hour the aeroplane would leave the railway track and run on the guard rails above. The soaring tendency of the contrivance eventually became so great that Maxim found himself in the position of a Frankenstein, unable to control the thing he had created. This is what happened during his last experiment: After rushing along for one thousand feet, the latter half of which was covered in the air, the lifting strain became so great that the rear axles were doubled up and about one hundred feet of the wooden guard rails were torn away. When steam was shut off the aeroplane dropped to the ground, all but a wreck. Its short sensational flight proved that its stability was imperfect. Sir Hiram spent about £25,000 in these dramatic tests, and never repeated them. He was the first to succeed in lifting a motor-driven aeroplane off the ground, carrying with it an engine, a boiler, fuel, water, and a crew of three men. Although his experiment was, on the whole, a failure, it was one of those great useful failures that teach much. If he did nothing else he gave us at least the mechanism of modern aerial locomotion. His novel conception of light driving-machinery is now embodied in every steam motor-car. It is not likely that, with his defective means of balancing his aeroplane, he would ever have succeeded in actually flying Ifr eely through the air. In a way Lilienthal and Maxim unconsciously worked hand in hand. The one made a painstaking study of the effect of gliding-planes; the other instituted the most elaborate researches of his day on the action of the screw propeller. Octave Chanute continued the work of the ill-fated Lilienthal. Realising the inherent danger of a glider in which the operator must adapt himself to the changing centre of air pressure with the suddenness of lightning, he devised an apparatus in which the centre of air pressure was automatically controlled so that there was no longer the perilous necessity of indulging in aerial gymnastics. In his machine the tips of the planes, when struck by a gust of wind, would fold slightly backward, thus considerably curtailing the tendency of the centre of air pressure to shift. The Wright brothers, the Americans, of whom we have lately heard so much, have adopted this principle. Chanute built six motorless, man-carrying glideYs with three of which- several thousand short flights were successfully undertaken. The best results were obtained with an apparatus * consisting of two Superposed planes, a Construction which has likewise been copied by the Wright brothers. For the first lucid and systematic enunciation of the principles of exact 'aerodynamical science we are largely indebted to the late Samuel Pierpont Langley, perhaps the most distinguished of American astronomical physicists. Langley-approached the problem scientifically, and after years of unflagging labour learned enough that was really new and valuable to write his “Experiments in Aerodynamics,” which stands to-day a monument to his rare genius and which bears to aerial engineering the relation that Darwin’s “Origin of Species” bears to biology. Lilientbal studied birds in flight; Langley adopted the more scientific method of constructing small artificial soarers and observing their curious gyrations. Unlike Maxim, he began, not by the immediate Construction of a flying machine, but by endeavouring to ascertain the principles on which one should be built. After many years of patient preliminary investigation he discovered a very para doxical law which proclaims that under certain conditions the power required to drive a plane surface horizontally through the air diminishes as the sjiecd increases. Consider that law carefully, and its oddity will strike you. If you wish to run fast, you expend more muscular energy; if you wish to cover a great distance in a given time in a locomotive or in a steamship, you burn more coal and drive your engines harder

than if your pace is more leisurely. In the air all this is changed. The faster you skate over the air the less power you need. That is Langley’s law. It reveals the undreamed-of power lying dormant in the air. In embodying his discoveries in au aerial vehicle, Langley found it necessary to devise an engine of unprecedented lightness, much after the manner of Maxim. He was concerned at first with the construction of a small model and not with a man-carrying contrivance, for which reason he was constrained to work quite independently. Eventually he succeeded in building a little, steam-engine and boiler weighing together less than seven pounds and yielding over a horse-power. This machinery was placed in a small hull with two propellers amidships, the whole suspended from a steel rod carrying two pairs of fixed wings each slightly curved. A rudder adapted for both vertical and horizontal steering completed the equipment. From tip to tip the wings or planes measured about thirteen feet. The entile weight of the model was thirty pounds. After tedious experimenting, Langley saw that the model, in order to fly, must start in the face of the wind, like every soaring bird. Consequently he found it advisable to carry it on top of a houseboat which could easily be turned in any direction on the water. Before an aeroplane can fly it must be in motion. How this preliminary motion was to be obtained was a serious question. The aeroplane was as sensitive as a feather to every puff of wind. Langley tried every conceivable way of starting his model, and at last hit on the idea of launching it from ways, somewhat as a ship is launched into the water. The model rested on a car which fell down at the extremity of its motion and thus released the model for its free flight. On May 6, 1896, he saw his creation really fly like a living thing. It rose gracefully like a bird of prey, and after a minute and a half, for which time only it had been provided with fuel and water, it slowly descended. In that minute and a half it covered little more than half a mile, which means that it travelled at the rate of nearly thirty miles an hour. Immediately after its descent it was taken from th • water and flown again with equal success. On November 28, 1896, another model of similar construction traversed three-quarters of a mile with the same ease and safety and would have flown indefinitely had it been sufficiently supplied with fuel and water. This apparatus is still preserved in the Smithsonian Institute at Washington. With this striking demonstration of the possibility of artificial flight, Langley was quite content. Still, he was induced to undertake the building of a man-earrying machine on the lines of his quarter-size model, for which purpose the United States Government appropriated about fifty thousand dollars. The flying weight, of this aeroplane with that of the operator is 830 pounds; its-sustaining surface is 1040 square feet; its engine of fifty-two horse-power weighs less than five pounds to the horse-power, and is far lighter than any engine of its size which has ever been built. With some natural confidence in the launching device which had worked so perfectly in the many flights made with the model, Langley concluded that an enlarged duplicate would prove equally successful. It failed him utterly. The aerodrome was dashed into the water. Although the machine never had a chance to fly it is popularly regarded as an expensive failure. The truth is that it was never properly launched. It is no more a failure than a ship that has never left her cradle. Lack of funds prevented Langley from carrying his work to a successful conclusion. It is not unlikely that Mr. Manly, his assistant, will renew the attempt to fly with this large machine-driven glider. It remained for Orville ami Wilbur Wright of Dayton, Ohio, to show that a man-carrying aeroplane can fly freely through the air. So secretly have their trials been conducted that very little, indeed, is known of their invention. The novelty of their apparatus is to be found in a trustworthy system of maintaining stability, without which an aeroplane can never be safe. In the first place they transferred the rudder from the rear to the front, where it proves most effective in properly balancing the craft —a very slight improvement apparently, and yet one that menus much. Further-

more, they have adopted Chanute'S method of twisting and shifting the wings, so as to maintain the side-to-side balance of the machine by keeping the centre of air pressure and the centre of gravity in the same straight line from front to rear. How this has been accomplished is part of their secret. Whatever the mechanism may be, it undoubtedly reduces the mental and physical agility which is ordinarily required in pursuing the constantly changing centre of air pressure. Beginning in 1901, the Wrights glided year after year at Kill Devil Hills, North Carolina, and at Dayton, Ohio. In the end they developed the most startlingly perfect flying-machine that human hands lias ever fashioned. On December 17, 1903, their machine travelled 852 feet in fifty-nine seconds—the first time that a man-carrying motordriven aeroplane soared through the air. In 1904, they flew three miles at the rate of thirty-four miles an hour. In 1905, they covered over twenty-four miles at a speed of more than thirtyeight miles an hour, which is the best time that has ever been made in the air by any type of vessel. They declare that a speed of sixty miles can be reached, and that even in the present state of the art a practicable and durable flyer can be built that will carry a man and supplies for a journey of over five hundred miles at a speed of fifty miles an hour. The Wrights have soared in straight lines and in circles, with and against the wind, and have conclusively demonstrated that the problem of aerial navigation is not beyond solution. In three years they liave made more than 160 flights of varying lengths. The fame of these achievements has naturally spurred on other inventors, particularly in France. Even SantosDumont lias been induced to abandon his air-ships and to try tile motordriven aeroplane. Without any preliminary experimenting whatever, he plunged directly into I lie air with a full-sized machine, and after repeated mishaps, has succeeded in flying about 800 ft in a straight line. He is the only emulator of th? Wrights who lias accomplished anything of note. His latest conception is incorporated in a design which is a combined aeroplane and dirigible bullion. In this new ship the planes will act primarily as parachutes to insure steadiness in flight, and especially in descending to the earth. Beyond that they serve no useful purpose. His hybrid craft remains an air-ship pure and simple. Although it has not been tested as yet on a large scale, it will probably sail through the air quite as readily as did his aerostats. While the Wrights have more or less followed in tne footsteps of Chanute, Alexander Graham Bell, the inventor of the telephone, has struck out in a decid-’ odly original e.xy, that seems full of pro-'-mise. Recognising the fact that machines such as Maxim, Langley, and the Wrights have designed must be driven at high speed in order to keep aloft, theiroperators thereby incurring no small risk, he has endeavoured to devise a method of soaring with safety. Professor Bell has approached the problem by designing kites which are actually capable of lifting men. So large arc these structures that they cannot be held by hand, but must be anchored to the ground by stout cleats. He started with the idea that., although a small bird can support only a small weight, a. flock of small birds can sustain a very heavy load properly distributed among them. By combining a number of small structures each light enough to fly, instead of simply reproducing the small structure on a large scale, he has pieced together a cellular kite in which the ratio of weight to supporting surface is the same as that of the individual units of which it is composed. He lias discovered that a tetrahedral cell (a pyramidal structure with four plane triangular surfaces) is remarkably strong for its weight, and that a combination of tetrahedral cells forms a wonderfully rigid kite. Each cell seems like a bird with wings uplifted and half parted; the entire kite resembles n. whole Hock of birds with connected wings. Of the many kites which he has made in this way, the largest is one. which ho calls the Frost King, composed oi no less than l.'>u<t cells, weighing 2SSIb This kite has not only flown well in ft 10-mile breeze, but has supported a cordage ladder, several dangling ropes 40ft long, about 800 ft of manila hemp used as a flying line. and. lastly, a man of generous proportions. Tctrahedi I kites of this kind seem

to balance themselves automatically. Each little cell has its own centre of gravity ami its own centre of air pressure, which, as we have seen, must bear a certain relation to each other. The centre of air pressure of each cell can change but very slightly, because of the small size of the cell, and the centre of air pressure of the whole kite can be displaced to no greater extent than the centres of air pressure of the individual cells themselves. That is why the equilibrium of a tetrahedral kite, however large, is never seriously in danger. As yet Professor Bell has not incorporated his tetrahedral theory ip a motor-driven aeroplane. For the last two years he has been planning a large machine. At present his attention is devoted to the driving-machinery of such a craft. For many months he has been testing propellers which are mounted on a boat in such a manner that they revolve, not in water, but in the air, the object being to ascertain what form of propeller and what speeds are most efficient. By the aid of his air-screws he is able to drive his boat at the rate of about six miles an hour. W hat the future of aerial navigation may be no one, not even 11. G. Wells, can foretell. Whether or not we shall ever soar in aeroplanes as we speed along in motor-ears, it is at least certain that the llying-machine inventor is no longer classed with the mathematical fanatic who spends a lifetime in fruitless attempts to square the circle, or tlie> mechanical monomaniac whose one idea is the discovery of perpetual motion. If a llying-machine is ever invented that can be taken out at any time like a steam-launch, it will probably find its first application in war.. It is not utterly impossible that the battle of the future will be a battle of rapidly wheeling fleets of aeroplanes, and that the victory will lie with the stanchest motors and the most stable supporting surfaces.