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Aviation History
1910
1910 - 0178.PDF
THE WRIGHT BIPLANE. EVERYONE who has followed the history of the develop ment of the Wright biplane is familiar with the fact that it was evolved from a glider of almost identical design although different in actual dimensions. In having very fully described the construction and operation of a Wright glider in FLIGHT, Vol. I, page 568, therefore, we have already covered a great deal of the ground that would otherwise afford subject matter for the present article; in fact, the accompanying remarks and illustrations must largely be regarded as supplementary to the previous description. We publish on the opposite page a plan and elevation of the machine, and there appear herewith three sketches of details that we have not hitherto fully illustrated. One shows the bracing of the rudder, another shows the attachment of the vertical struts to the main spars, and the third illustrates how the radius- rods between the chain-brackets are coupled up to cases containing ball-bearings that ride upon the crank-shaft. The general construction of the machine is much the same as the glider that we have already described. Each main deck is built up of two transverse spars placed four feet apart and joined at intervals of about twelve inches by specially shaped rib members that project behind the rear spar and form the flexible trailing edge that is such an important feature of these machines. Two points of especial interest about the arrangement of the ribs are that those near the extremities of the spar are curtailed and are also less in camber than those in the centre, and that the two main spars themselves lie at the same level above the ground, so that it is entirely due to the trailing portion of the decks that the chord has any angle of incidence at all. The flattening and curtailing of the ribs in the vicinity of the extremities of the decks reduces the intensity of the aerodynamic disturbances, and tends thereby to avoid loss of efficiency by reducing the lateral spewing of the air from beneath the decks. The horizontal position of a chord drawn between the two main spars is of particular interest because it emphasises the practical application of the principle of the dipping front edge. The machine in horizontal flight proceeds through the air with the chord between the two main spars in a horizontal position, consequently the leading edge dips down instead of being tangential to the line of flight. Lanchester's theory of the dipping front edge—the discovery of which, by the way, is due to Phillips, who describes this peculiarity of a bird's wing in his patent No. 13,768 of 1884—is that an aeroplane in horizontal flight is virtually always falling through the air and is, therefore, always meeting an up-current. This up-current, when compounded with the horizontal motion of the machine, gives to the relative wind an actual obliquely upward trend, and it is to this slope that the leading edge of the aeroplane should be tangential in order that it may receive the air without shock. Having received the air in this way the cambered surface of the aeroplane proceeds to change the upward motion of the air into downward motion, and this is done gradually by the gentle camber of the decks. By the time that the molecules of air have reached the rear spar their direction of motion has been entirely reversed, and this has taken place, it will be seen, without reference to the trailing portions of the decks or to the question of the amount of the angle of incidence represented by the chord between the leading and trailing edges of the complete deck. By its action of continuously changing the direction of flow of a stream of air, the aeroplane experiences the upward lift that supports it in flight, and according as the engine power is more or less than the exact amount required for horizontal flight so does the machine ascend or glide obliquely to the earth. The thrust of the two propellers (which are driven in opposite directions by chains, one of the chains being crossed), forces the machine through the air, and causes the aerodynamic condition that has been described above. In order to maintain the machine in equilibrium, the pilot is provided with three controls that are operated by two levers, one of which he holds in his right hand while the other he holds in his left hand. The lever held by the pilot's right hand controls a miniature biplane that is mounted on a horizontal transverse axis situated about twelve feet in front of the main decks. This elevator, as it is termed, is carried on a light outrigger framework that also extends beneath the body of the machine and forms the ski or runners wherewith the machine alights upon the ground. The purpose of the elevator is to assist in maintaining longitudinal equilibrium, and its two decks are so constructed that they can be flexed into a camber that is either concave or convex to the earth as required. When Sketch showing the bracing of the rudder on the Wright biplane. the pilot moves the lever so as to make the camber of the elevator concave to the earth, its aeroplane action, which is the same as that of the main planes already described, is such as to tilt up the front end of the machine. Conversely, if the machine is already tilted up too far, a reversal of the camber serves to restore the horizontal position. 174
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