Gliding

“ In gliding experiments it has long been known that the rate of vertical descent is very much retarded, and the duration of the flight greatly prolonged, if a strong wind blows up the face of the hill parallel to its surface. Our machine, when gliding in still air, has a rate of vertical descent of nearly six feet per second, while in a wind blowing 26 miles per hour up a steep hill we made glides in which the rate of descent was less than two feet per second. ”

“ Why Kitty Hawk?
Wilbur and Orville now proposed to build a full-size, man-carrying glider on which to test their method of control. Highly enthusiastic with the idea of gliding as a sport, they started thinking of a place for testing it. To get practice in operating the glider, they would first fly it as a kite before making gliding flights. For kite flying, steady winds and flat, open country were needed; for the gliding, a sandy area for soft landings and sandhill slopes free of 14 trees and shrubs for low-level flights. ”

“ In our gliding experiments we had had a number of experiences in which we had landed upon one wing, but the crushing of the wing had absorbed the shock, so that we were not uneasy about the motor in case of a landing of that kind. ”

“ Sometimes, indeed, the wings do bend just a little—for, after all, they have a joint—but the straight-set attitude is more germane to them, and soon they assume it again, shooting forward so briskly, yet softly, that one seems to hear a soft little musical click.
And thus this dream and joy of glorious motion, this elemental spirit of a bird, floats and flickers along, cradled in air, looking like a shadow upon it, sweeping and gliding, rising and falling, in circles of consummate ease. ”

“ Other methods of gliding have to be invented for special passages, or for the production of extraordinary effects. One of the most surprising effects is to combine the sforzando with a strongly marked glide, the sforzando being given on the second note of the slur, and the glide being of the most pronounced type. I have heard our great violinist, John Dunn, occasionally give vent to his feelings in a slightly exaggerated glide and sforzando combination of this description, and for waking up a sleepy or apathetic audience, I can strongly recommend it. ”

“ During six days of the practice season of that year, they made 375 gliding flights of various distances, most of them comparatively short, but each one of value in familiarizing the glider with the conditions to be met. It is not material whether gliding or manipulation of the control levers is taken up first, as both should be mastered as far as possible before attempting to fly a regular machine. ”

“ For it must be distinctly understood that there is constant danger in such preliminary experiments. When this hazard has been eliminated by further evolution, gliding will become a most popular sport.'
Later experiments proved that the biplane type of glider gave better results than the rather cumbrous model consisting of five tiers of planes. Longer and more numerous glides, to the number of seven to eight hundred, were obtained, the rate of descent being about one in six. ”

“ What most delayed the science and art of flight, which made no progress during the whole of the eighteenth century, was an imperfect understanding of the flight of birds. The right way to achieve flight, as events were to prove, was by the study and practice of gliding. But birds were believed to support, as well as to raise, themselves in the air chiefly by what in the jargon of science is called orthogonal flight, that is, by direct downward flapping of the wings. ”

“ They nearly all, however, use some slightly gliding force at the same time; a single stroke of the wing, with forward intent, seeming enough to enable them to glide on for half a minute or more without stirring a plume. ”

“ Some of the best gliding flights made by Herring, Chanute's co-worker, were in a rudderless glider. After having mastered the rudiments of the art, the student may go as far as the dictates of his ambition impel him in the direction of improvements in his glider, by adding a rudder, elevator, and warping control. ”

“ Now the center of air pressure in gliding may not be at the same point as its sustaining weight when held by the hand, and furthermore, as the arm-pits, by which the body of the experimenter are held while gliding, are not at the same point, but to the rear of the hands, the moment the glider is launched too great a weight is brought to the rear margin of the planes, hence its forward end lifts up. ”

“ The lone steersman of the descending boat observes the nocturnal hunter, gliding on extended pinions across the river, sailing over one hill and then another, or suddenly sweeping downwards, and again rising in the air like a moving shadow, now distinctly seen, and again mingling with the sombre shades of the surrounding woods, fading into obscurity. ”

“ It was while gliding through these latter waters that one serene and moonlight night, when all the waves rolled by like scrolls of silver; and, by their soft, suffusing seethings, made what seemed a silvery silence, not a solitude; on such a silent night a silvery jet was seen far in advance of the white bubbles at the bow. ”

“ Drag—A resistant force exerted in a direction opposite to the direction of motion and parallel to the relative gas or air Stream.
Dynamic lift—The lift given an airplane by the aerodynamic force produced from an adequately designed airfoil.
Glider—A fixed-wing aircraft having no power plant and constructed so as to glide and soar.
Gliding—The art, science, and activity of moving through the air in a glider.
Heavier-than-air aircraft—Any aircraft weighing more than the air it displaces. ”

“ The flexion of the wing is most obvious when the bird is exerting itself, and may be detected in birds which skim or glide when they are rising, or when they are vigorously flapping their wings to secure the impetus necessary to the gliding movement. ”

“ There is great popular interest in the problem of soaring, or flying as birds do, without any apparent effort, and also in gliding flights, or descending from a high altitude without the help of a motor. ”

“ In still air a bird, or whatever attempts to fly, must flap its wings energetically until it acquires initial velocity, when the flapping may be discontinued; or it must throw itself from a height, in which case the initial velocity is acquired by the weight of the body acting upon the inclined planes formed by the motionless wings. The flapping and gliding action of the wings constitute the difference between ordinary flight and that known as skimming or sailing flight. ”

“ Gliding angles vary in different machines. If the angle is one in twelve, this would mean that if the glide wave commenced at a height of 1 mile, and continued in a straight line, the pilot would come to earth 12 miles distant. ”

“ Gliding with a Chanute three-decker. A start with two assistants.
While it is necessary to make glides against the wind, it is not wise to attempt flights when the wind blows harder than 10 miles an hour. While the flight may be successful, the landing may be disastrous.
The accomplished glider operator is in line for the aeroplane, and it is safe to say that he will not 255 be long without one. The skilful and practised operator of a glider makes the very best aeroplane pilot. ”

“ In space they follow the forward flight, in a softly curved line; the downward stroke being as effective as the bird chooses, the recovery scarcely encounters resistance in the softly gliding ascent. Thus, in Fig. 5, (I can only explain this to readers a little versed in the elements of mechanics,) if B is the locus of the center of gravity of the bird, moving in slow flight in the direction of the arrow, w is the locus of the leading feather of its wing, and a and b, roughly, the successive positions of the wing in the down-stroke and recovery. ”

“ We cannot see that they are able to glide or soar on less than 8o. We watched them many times gliding down the west slope of the large hill, and whenever they maintained their altitude above the ground slope of hill they always seemed to lose speed, and were compelled to begin flapping. ”

“ All these grew out of kite experiments; and all gliders followed the kite construction, or the principles involved in them, so that, really, there is but one intervening step between the kite and the flying machine, as we know it, the latter being merely kites with power attached, as substitutes for the cords.
ONE OF THE USES OF GLIDER EXPERIMENTS.— There is one direction in which gliders are valuable to the boy and to the novice who are interested in aviation. He may spend a lifetime in gliding and not advance in the art. ”

“ Gliding O’er all Gliding o’er all, through all, Through Nature, Time, and Space, As a ship on the waters advancing, The voyage of the soul—not life alone, Death, many deaths I’ll sing. ”

“ They found that in order to support a man on it the glider required an angle nearer twenty degrees than three, and even with the wind at thirty miles an hour they could not get down to the planned angle of three degrees. 'Later, when the wind was too light to support the machine with a man on it, they tested it as a kite, working the rudders by cords. Although they obtained satisfactory results in this way they realised fully that actual gliding experience was necessary before the tests could be considered practical. ”

“ Gliding angle. (Aëronautics) The angle, esp. the least angle, at which a gliding machine or aëroplane will glide to earth by virtue of gravity without applied power.
Gliding machine. (Aëronautics) A construction consisting essentially of one or more aëroplanes for gliding in an inclined path from a height to the ground. ”

“ The position of the body on the arm rests can best be learned by a few experiments. No two gliders are quite alike in this respect, and no rule can be given. As to the requisite speed, it must be between 15 and 20 miles an hour; and as this speed is impossible to a man running, it is gained by gliding against the wind, and thus adding the speed of the wind to the speed of the runner. The Wrights selected the sand dunes of the North Carolina coast for their glider experiments because of the steady winds that blow in from the ocean, across the land. ”

“ Cut the paper to the dimensions given in Fig. 3 and make sure that it is flat, by pressing between the leaves of a book. Then project it horizontally into the air. It does not attain [Pg 7] gliding motion. It performs a series of evolutions, too quickly for the eye to perceive; but what happens is this. After launching, the front edge turns up and the sheet glides back. Now the back edge turns up and the glider dives forward. Again the front edge turns up, the glider slides back, the back edge turns up, it glides forward, and so on until the glider reaches the ground. ”

“ A machine must be in a gliding position before the engine is switched off.
The art of the accomplished pilot, granted there is no reason for him to reach earth quickly, is to glide at as fine an angle as is possible, consistent of course with51 maintaining the speed of the machine through the air, and so preserving his command over its controls. ”

“ Student should be instructed to rise fifteen or twenty feet from the ground in straightaway flights, and use rudder slightly in order to become accustomed to its use and its effect on the machine in the air. As soon as the student has accomplished the above he may be permitted to rise to the approximate height of one hundred feet if the field is large enough and to glide down under reduced power. When he has done this successfully many times, let him repeat the above gliding with motor cut out completely. ”

“ A beautifully-timed, fine glide, the machine stealing down gracefully, and touching the aerodrome light as a feather, at a precise spot the airman has decided on even when he was several thousand feet high, is a delightful spectacle for the onlooker, and a keen pleasure also—from the point of view of his manipulative skill—to the aviator himself. But a pupil, at any rate in his first attempts, must not concern himself too much with any idea of a fine or graceful glide. ”

“ AN INITIAL IMPULSE OR MOVEMENT NECESSARY.— Let A, Fig. 9, represent the section of a bird's wing. All birds, whether of the soaring or the flapping kind, must have an initial forward movement in order to attain flight. This impulse is acquired either by running along the ground, or by a leap, or in dropping from a perch. Soaring birds cannot, by any possibility, begin flight, unless there is such a movement to change from a position of rest to one of motion. ”

“ Of all animal movements, flight is indisputably the finest. It may be regarded as the poetry of motion. The fact that a creature as heavy, bulk for bulk, as many solid substances, can by the unaided movements of its wings urge itself through the air with a speed little short of a cannon-ball, fills the mind with wonder. Flight (if I may be allowed the expression) is a more unstable movement than that of walking and swimming; the instability increasing as the medium to be traversed becomes less dense. ”

“ It is, I suppose, the small apparent mechanism of the flight that gives this impression, the absence, or the ease, of effort. Sliding, as it were, from the face of the precipice, and often from the most towering heights of it, the thin cleaver-like wings are at once, or after a few quick, flickering vibrations, spread to their full extent, and on them the bird floats, sweeps, circles, now sinking towards the sea, now cresting the summit of the cliff, [1] but keeping, for the most part, within the middle space between the two. ”

“ They began coasting down the air from the tops of sand dunes, and after the first few glides were able to slide three hundred feet through the air against a wind blowing twenty-seven miles an hour. The reason their glider flights were made against the wind was because the wind passing swiftly under the planes had the same effect as if the machine was moving forward at a good clip, for the faster the machine moves, or the faster the air passes under it, the easier it remains aloft. ”