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Aviation History
1953
1953 - 1634.PDF
788 THE WRIGHT FLYER . . . machine towards the end of 1902. Having failed to find a car manufacturer able to supply a suitable engine—as related in another article in this issue—they designed and built their own, a horizontal four-cylinder water-cooled unit. Construction of the airframe began in June 1903 and was completed by September. As on die Wrights' gliders, "the superposed horizontal surfaces formed by stretching cloth upon frames of wood and wire con stitute the 'wings' or supporting parts of the apparatus. They are connected to each other through hinge-joints by upright standards and lateral stay-wires which, together with the lateral spars of the wing framing, form truss systems, giving the whole machine great transverse rigidity and strength." To accommodate the wing warping, however, "the hinge-joints admit of both flexing and twisting movements." Spruce and ash are widely used in the construction of the biplane. (We write in the present tense deliberately, for the machine still exists.) On the mainplanes, spruce is used for the ribs and tips, and ash for the main spar, leading edge, and the short central trailing edge which supports the upper rudder struts. The main soars are in three leneths. each of 1 11 /16in x ljin cross- section (and slotted to depths of 5/16in to take the top and bottom capping of each rib) with a simple metal band slipped over the joints. From a consideration of these joints and the reduction in section due to the rib slots, the wing droop found on the machine comes as no surprise. The radius of this "anhedral arc" was measured as 244ft. The leading edge takes the place of the normal front spar and is constructed of ljin x l|in ash, rounded on the front face. The inter-plane struts, made of spruce, are of 1 15/16in x fin section at the centre, tapering to lfin x fin at the ends, and have rounded corners. Their extremities carry Jin wire eyes which engage with clips on the main spar and the leading edge. The trailing edge of the wing is of piano wire pocketed into the fold of fabric ("Pride of the West" muslin) and attached to the ribs by tape. An interesting fact is that the semi-span, measured from the central strut, is 19ft 11 15/16in to port and 20ft 4 l/16in to starboard. It is not known whether this was intentional or an indication of the manufacturing tolerances of 1903! The brothers Wright had produced sound reasoning to justify their choice of elevator configuration for their earlier gliders: "contrary to the usual custom, we place the horizontal rudder in front of the main surfaces or wings, at a negative angle, and use no horizontal tail at all. By this arrangement, we obtain a forward surface which is almost free from pressure under ordinary conditions of flight, but which, even if no* moved at all, becomes an efficient lifting surface whenever the speed of the machine is accidentally reduced very much below the normal, and thus largely counteracts that backward travel of the centre of pressure on the main surfaces or wings, which has frequently been productive of serious injuries by causing the machine to turn downward and strike the ground head-on." The same configuration, though with twin surfaces, and without the negative angle of attack, was retained for the Flyer. Construc tion of the elevators was of spruce, again with "Pride of the West" muslin as a covering for the flying surfaces. Movement of the elevator is achieved by a control frame comprising a |in-diameter steel tube with three control ribs and a spruce pulley wheel rigidly attached, and pivoting about two U-clips screwed to the vertical elevator bearers. The ribs of this frame are connected by pin- jointed struts at their leading and trailing edges to the actual elevator surfaces, which pivot on clips attached to the vertical bearers. A further three pin-jointed struts at the tips and centre connect the two elevator spars. Wires and chandelier chains passing over the spruce pulley con • nect the control frame directly with the pulley at the end of the pilot's horizontal control bar (which has a vertical hand-lever at the opposite end). Thus rotational movement of the bar caused Ignition of the Wright engine. The secondary shaft shown carries cams which operate the low-tension make-and-break mechanisms inside the cylinder heads. Contact between the points is first made as the cams press the spring levers against the spring-loaded stop; the quick break which initiates a spark between the points is caused by the spring levers slipping off the end of the cams. The copper strip con necting the plugs is shown dotted. The lower end of one of the vertical struts, show ing its attachment to the leading edge. FLIGHT, 11 December 1953 by movement of the lever is transferred to the elevator. The rudder installation consists of two covered surfaces forming opposite sides of a rectangular box framework, which is pivoted top and bottom on its central axis at the extremities of two horizontal Vee spruce frames. The in board ends of these frames are hooked on to the trailing edge of the upper wing and the main fuselage frame. Spruce and ash are again used for the members of this frame, which runs for ward beneath the wings to end at the upswept elevator supports. Transverse skids are fitted across the frame, and spruce struts connect the upper plane with the bottom of the elevator supports, and the lower plane with the elevator supports at a position just above the control frame. Between the latter pair of struts, just ahead of the wing leading edge, the pilot's elevator control bar is mounted. Linkages in the piano-wire control runs consist of short sections of chain passing over pulleys. As mentioned, wing warping was used in place of ailerons, and was combined with the movement of the rudder. To move the rudder and wing controls, the pilot twisted his body sideways, so moving the wooden cradle in which he lay. (The pilot's position is prone, to the left of the engine and on the central portion of the lower mainplane: the prone position was chosen simply to reduce air resistance.) From the upper wing surface, wires pass from the top of the outboard rear strut (and from the top of the second rear strut) diagonally to the bottom of the third strut, along the lower wing to the corresponding strut on the opposite side, and diagonally up to the outboard (and second) strut at the other end of the wing. These wires are linked to the pilot's cradle and another wire leads from the lower end of the outboard strut to the top of the third strut, and along and diagonally down again in symmetrical manner. The central portion of the lower wing-surface control-wire passes between two bell-cranks, to which are attached also the rudder- control wires; these pass to the bottom inter-rudder strut, crossing over shortly before attachment. The Wright engine weighed 170 lb* and developed 12 b.h.p. at 1,020 r.p.m. (16 b.h.p. at 1,200 r.p.m. was obtained for the first few seconds after starting). It had automatic inlet valves, direct fuel injection, and magneto ignition. From the engine, the drive to the shafts of the two pusher airscrews was by chains (the port one crossed to provide counter-rotation), which passed through mild-steel guide tubes. A low-tension generator was incorporated. The airscrews were of spruce, carved from the solid, and had fabric-covered tips. Their design and construction followed much painstaking research work by the Wrights on model airscrews in addition to their previous work on aerofoils. Shortly after the biplane had been completed, the tubular airscrew shafts then fitted fractured during engine-testing and were replaced by solid shafts. The outer tube in which each shaft runs is braced in position between the upper and lower planes in a simple system of metal bearer-tubes and by two bracing wires. Airscrew thrust efficiency was stated to be 66 per cent. Instrumentation was simple yet ingenious, consisting of an anemometer, stopwatch and rev counter (not tachometer), mounted on the forward central strut. Flight duration and anemometer revs were automatically recorded, enabling the air speed to be calculated. The absence of a fixed vertical fin, a fixed horizontal tail and of wing dihedral made the 1903 Wright Flyer an aircraft with no automatic or "built-in" stability; the pilot had to control the machine manually and continuously during flight, and this was in accord with the brothers' original design intentions. From 1928 until 1948 the actual Wright Flyer formed a part of the National Aeronautical Collection at the Science Museum, South Kensington, London. Prior to its return to the U.S.A. in 1948, an exact replica of the biplane was constructed by the appren tices of the de Havilland Technical School, for the Museum. Much help in the preparation of this description of the Flyer has come both from the de Havilland Company (Mr. H. D. Wright and Mr. W. Honeywood of the Technical School) and from the staff of the Science Museum, whose drawings of the original machine have contributed much to the detail and accuracy of our own specially prepared three-view GA. on the previous page. To those who have found this brief description of interest, we would suggest a visit to South Kensington, to view there the excellent Wright biplane replica. Only by seeing the shape and form of this machine "in the flesh" can its interesting design and ingenious control system be fully appreciated. But more impor tant than its technical interest is, of course, its place in history. For this is the machine that made history, just fifty years ago at Kitty Hawk. 'Some authorities have quoted other weights for this engine, e.g., 180 and 240 lb; but we believe 170 lb (including magneto and flywheel) to be a reliable figure.
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