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Aviation History
1947
1947 - 0480.PDF
2OO PLIGHT X£. ApRIL 3RTJ. *947 THE BRABAZON I this region on the rear spar, a reinforcing boom is additionally fitted to the top boom of the spar, this extending ioft 6in on each side of the centre line. At the outboard ends of the inner wing are diaphragm chordal ribs, the space between them housing fuel tanks; to complete the tank cell, the web structure of the front spar at this point is also a diaphragm. Attachment of the outer wing panels is quite conventional in the fork-end-and-lug / pin- joint fashion, but the outer wing panels are of very different construction from that used for the inner wing. At the 15 per cent chord ordinate is a diaphragm-type spar, called the '' front tank spar'' comprising a plate web with channel-section booms: this forms the lront spar of the outer wing. At the 27 per cent ordinate (that is to say, lining up with the inner wing front spar) is the front spar con- tinuum which, in point of fact, is merely a pair of booms with no web structure ; this is to give tank clearance, and distribute stress between the outer and inner wings. At the 55.2 per cent ordinate is the tank rear spar made up with conventional booms and a plate web, t^is extend- ing only to the outboard end of the tank emplacement; its construction is similar to that of the front tank spar. At the 68.807 per cent ordinate is the rear spar proper, of normal plate web and L-section boom construction, which picks up with the rear spar of the inner wing and extends tovthe*full span." Inner wingstructure, showing details of front spar,chordal ribs, stabilizing - members, stringers and reinforc-ing booms. ' Flight " copyright thttch. Fuel tanks are in twelve main units in each outer wing panel, and they are spaced by dividing ribs formed with two diaphragms enclosing a central cavity in which are vertical channel-section stabilizers ; the contour members of these ribs are of spine-flanged channel-section. As pre- viously noted, two extra tanks are fitted in the outboard ends of the inner wing. Just as the quality of skinning and the close tolerance of the skin panel thickness applies to the fuselage, so it also applies to the skin plating of the wings. For similar reasons of stress / weight factors, skin thickness is graded spanwise and chordwise, the heaviest gauge being em- ployed around the centre-section, each panel outboard be- ing reduced in gauge. Of the- three panels at each chordal section, that attached to the front spar is the heaviest. Considering the skinning in some degree of detail, the centre-section is plated with sheet o.i85in thick, successive Tailplane (port half) being built. As well as showing the tailplane basicstructure, this view gives an idea of the Brabazon's scale. outboard skins being respectively 0.176m, o.i66in, o.i44in, and 0.125m thick. At the outer end of the wing the final three panels are 0.125m thick attached to the front spar; 0.095m attached to the rear spar, with a centre panel o.n6in thick. The preceding skin thicknesses apply to the upper surface of the wing, but broadly speaking the same gradations apply to the lower surfaces with the exception that the panels are, in most cases, a gauge below their counterpart on the top surface ; however, compensating this is the use of extensive reinforcing skins around the under- carriage bays. As illustrated in an article on the power installation of the Brabazon ('' Duplex Air- screws," Flight, December 26th, 1946) the four twin- Centaur us VXX power plants are housed in the leading edge of the inner wing. Outboard of the outermost engine cells in the leading edge of the inner wing are twin surface- combustion heaters, each of 400,000 b.t.u. capacity, which feed outward into ducts incorporated in the leading edge of the outer wing for thermal anti-icing. Hot air delivered from the heaters is fed through elbows and introduced into a sealed chamber in the leading-edge nose whence it enters a 0.128m cavity between the inner and outer leading-edge skins on the nose line. The inner skin is dimpled and at each dimple a rivet attaches the skins ; the hot air niters between the skins and escapes ward at top and bottom into the inter-spar space of wing, to t)e exhausted to atmosphere between the ailerons" and flaps. The leading-edge skins are carried on open ribs and, as a structure, the leading edge is divided spanwise by a diaphragm, forward of which is the thermal duct. The tailplane leading edge is of precisely similar construction. Ailerons have a reflex curved top contour and are pure flap-type surfaces without balance of any form. They are fabricated as two-spar structures, the front spar having a plate web with rolled channel-section booms, whilst the rear spar is simply a channel-section member. Chordal ribs are diaphragm type spanned by beaded L-section stringers. Each aileron is swung on eight hinges which, in common with all the hinges used for control surfaces, are self-aligning barrel-type needle-roller bearings. Flaps are plain type full trailing-edge section surfaces hinged on the forward edge of the lower surface, those on the inner and outer wing being separately actuated.
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