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AERONAUTICS

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Originally appearing in Volume V01, Page 261 of the 1911 Encyclopedia Britannica.
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AERONAUTICS , the See also:

art of " navigating " the "See also:air." It is divisible into two See also:main branches—aerostation, dealing properly with See also:machines which like balloons are lighter than the air, and aviation, dealing with the problem of artificial See also:flight by means of flying machines which, like birds, are heavier than the air, and also with attempts to See also:fly made by human beings by the aid of artificial wings fitted to their limbs. Historically, aviation is the older of the two, and in the legendsor myths of men or animals which are supposed to have travelled through the air, such as See also:Pegasus, See also:Medea's dragons and See also:Daedalus, as well as in See also:Egyptian bas-reliefs, wings appear as the means by which aerial locomotion is effected. In later times there are many stories of men who have attempted to fly in the same way. See also:John See also:Wilkins (1614-1672), one of the founders of the Royal Society and See also:bishop of See also:Chester, who in 1640 discussed the possibility of reaching the See also:moon by volitation, says in his Mathematical Magick (1648) that it was related that " a certain See also:English See also:monk called Elmerus, about the See also:Confessor's See also:time," flew from a See also:town in See also:Spain for a distance of more than a See also:furlong; and that other persons had flown from St See also:Mark's, See also:Venice, and at See also:Nuremberg. Giovanni Battista See also:Dante, of See also:Perugia, is said to have flown several times across See also:Lake See also:Trasimene. At the beginning of the 16th See also:century an See also:Italian alchemist who was collated to the abbacy of Tungland, in See also:Galloway, See also:Scotland, by See also:James IV., undertook to fly from the walls of See also:Stirling See also:Castle through the air to See also:France. He actually attempted the feat, but soon came to the ground and See also:broke his thigh-See also:bone in the fall—an See also:accident which he explained by asserting that the wings he employed contained some fowls' feathers, which had an " See also:affinity " for the dung-See also:hill, whereas if they had been composed solely of eagles' feathers they would have been attracted to the air. This See also:anecdote furnished See also:Dunbar, the Scottish poet, with the subject of one of his See also:rude satires. Leonardo da See also:Vinci about the same time approached the problem in a more scientific spirit, and his notebooks contain several sketches of wings to be fitted to the arms and legs. In the following century a lecture on flying delivered in 1617 by Fleyder, See also:rector of the See also:grammar school at See also:Tubingen, and published eleven years later, incited a poor monk to See also:attempt to put the theory into practice, but his machinery broke down and he was killed. In See also:Francis See also:Bacon's Natural See also:History there are two passages which refer to flying, though they scarcely See also:bear out the assertion made by some writers that he first published the true principles of aeronautics. The first is styled Experiment Solitary, touching Flying in the Air: —" Certainly many birds of See also:good wing (as kites and the like)would bear up a good See also:weight as they fly; and spreading feathers thin and See also:close, and in See also:great breadth, will likewise bear up a great weight, being even laid, without tilting up on the sides.

The farther See also:

extension of this experiment might be thought upon." The second passage is more diffuse, but less intelligible; it is styled Experiment Solitary, touching the Flying of unequal Bodies in the Air:—" Let there be a See also:body of unequal weight (as of See also:wool and See also:lead or bone and lead) ; if you throw it from you with the See also:light end forward, it will turn, and the weightier end will recover to be forwards, unless the body be over See also:long. The cause is, for that the more dense body hath a more violent pressure of the parts from the first impulsion, which is the cause (though heretofore not found out, as hath been often said) of all violent motions; and when the hinder See also:part moveth swifter (for that it less endureth pressure of parts) than the forward part can make way for it, it must needs be that the body turn over; for (turned) it can more easily draw forward the lighter part." The fact here alluded to is the resistance that bodies experience in moving through the air, which, depending on the quantity of See also:surface merely, must exert a proportionally greater effect on rare substances. The passage itself, however, after making every See also:allowance for the See also:period in which it was written, must be deemed confused, obscure and unphilosophical. In his See also:posthumous See also:work, De Motu Animalium, published at See also:Rome in 168o-1681,G.A.See also:Borelli gave calculations of the enormous strength of the See also:pectoral muscles in birds; and his proposition cciv. (vol. i. pp. 322-326), entitled Est impossibile ut homines propriis viribus artificiose volare possint, points out the impossibility of See also:man being able by his See also:muscular strength to give See also:motion to wings of sufficient extent to keep him suspended in the air. But during his lifetime two Frenchmen, Allard in 166o and Besnier about 1678, are said to have succeeded in making See also:short flights. An See also:account of some of the See also:modern attempts to construct flying machines will be found in the See also:article FLIGHT AND FLYING; here we append a brief See also:consideration of the See also:mechanical aspects of the problem. The very first essential for success is safety, which will probably only be attained with automatic stability. The underlying principle is that the centre of gravity shall at all times be on the same See also:vertical See also:line as the centre of pressure. The latter varies with the See also:angle of incidence. For square planes it moves approximately as expressed by joessel's See also:formula, C+(0.2+o• See also:sin a) L, in which C is the distance frcm the front edge, L the length fore and aft, and a the angle of incidence.

The See also:

movement is different on See also:concave surfaces. The See also:term aeroplane is understood to apply to See also:flat sustaining surfaces, but experiment indicates that arched surfaces are more efficient. S. P. See also:Langley proposed the word aerodrome, which seems the prefer-able term for apparatus with wing-like surfaces. This is the type to which results point as the proper one for further experiments. With this it seems probable that, with well-designed apparatus, 40 to 50 lb can be sustained per indicated h.p., or about twice that quantity per resistance or " thrust " h.p., and that some 3o or 40%/, of the weight can be devoted to the machinery, thus requiring See also:motors, with their propellers, shafting, supplies, &c., weighing less than 20 lb per h.p. It is evident that the apparatus must be designed to be as light as possible, and also to reduce to a minimum all resistances to propulsion. This being kept in view, the strength and consequent See also:section required for each member may be calculated by the methods employed in proportioning See also:bridges, with the difference that the support (from air pressure) will be considered as uniformly distributed, and the load as concentrated at one or more points. Smaller factors of safety may also have to be used. Knowing the sections required and unit weights of the materials to be employed, the weight of each part can be computed. If a See also:model has been made to absolutely exact See also:scale, the weight of the full-sized apparatus may approximately be ascertained by the formula W' = W tV s in which W is the weight of the model, S its surface, and W' and S' the weight and surface of the intended apparatus.

Thus if the model has been made one-See also:

quarter See also:size in its homologous dimensions, the supporting surfaces will be sixteen times, and the See also:total weight sixty-four times those of the model. The weight and the surface being determined, the three most important things to know are the angle of incidence, the " lift," and the required See also:speed. The fundamental formula for rectangular air pressure is well known: P=KV2S, in which P is the rectangular normal pressure, in pounds or kilograms, K a coefficient (0.0049 for See also:British, and o•11 for metric See also:measures), V the velocity in See also:miles per See also:hour or in metres per second, and S the surface in square feet or in square metres.

End of Article: AERONAUTICS

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