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Aviation History
1947
1947 - 0518.PDF
3io FLIGHT APRIL roTH, 1947 AIRSPEED AMBASSADOR span but from thence to the outboard ends are taper-machined. Stringers are all full-span members, those to the top surface being top-hat extrusions, whilst Z-extru-sions arc used for the lower surface. Pitching centre-to- centre of the top stringers is 4.6m, and that of the lowermembers 3.14m, all being parallel throughout their span. Generally, inter-spar ribs are diaphragm-type units, butin way of each nacelle are five ribs with their diaphragms cut away for auxiliary fuel tanks. The tanks—which,when used, will be of bag type—are housed in a tunnel through the ribs. Leading edge structure between thefuselage and nacelles is of unit type with access doors hinged forward in the lower surface : the skin is i6g carriedon pressed sheet ribs and stiffened with Lintercostals. Wing Joint Details As mentioned, the joint between the centre-section andouter wing panels is actually made through the skins; there is no connection between the spars as normallyknown, but, instead, there are serrated fittings for trans- mitting lift and torsion loads. Bending loads developed astensiles and compressions in stringers and skin surfaces are transferred through upper and lower joint plates at theoutboard ends ol the centre-section and inboard ends of the outer wings, the joint plates being edge-bolted togetherspanwise as shown in the detail sketch. Skin panels are continuous up to the joint, and the Z-section stringers arecarried up over the "ramp" of the joint plates and through-riveted to the skin. The joint plates on the centre-section have milled slots for the attachment bolts (-fein dia. bottom, and fin dia. top) which are of HT steel andscrew into vertical spools housed in the complementing joint plates on the outer wing panels. A steel dome nutwith a knife-edge rim screws on to the spool spigot and bites into the dural joint platr +0 effect a fuel seal, since the outer wing joint plates are inside the integral fuel tanks. The serrated racks uniting the spars are arranged thus: at the joint, extruded T-section vertical members are fitted at the junction of spar and end-rib, the flanges of the T picking up to the rib web with the leg of the T riveted to the spar web. The rack fittings are through-bolted to the rib web and T flanges. Outer wing spars are of plate web type with L-section extruded booms, the leg lengths, or depths, of the booms being progressive^ machined away spanwise although the sectional thickness remains constant. The spar webs form the fore and aft walls of the integral tanks and, as thermal de-icing is provided for the leading edge, an insulating cavity is left between the front spar web and the spanwise hot-air-sealing diaphragm, this cavity being ventilated by forced draught. Obviously a heat-insulating diaphragm * is necessary to prevent fuel boiling, and the forced-draught ventilation will preclude transmission of warmth and carry f' away any seepage fumes if they occur. One is inclined at first to question this feature of integral. fuel tanks in view of the seeming elaboration necessary, although the only complication is one of careful design to • avoid leak paths which need to be sealed. The fact that to use even bag-type tanks in this very thin wing would have reduced the effective capacity to 300 gallons per side instead of 500 gallons is as telling an answer as one could wish, quite irrespective of the saving of weight. Sealing is very simple, the use of rubber pads being confined to the corners; however, a special Bostick solution is swilled round the inside and then tipped out, so leaving a sealing membrane. Chordal ribs in the tanks have plate webs with internal cut-outs, and aci as anti-surge baffles ~ whilst permitting in- ternal access. Rib webs ride on the free flanges of the stringers, the fuel flowing between rib chambers through the cut-outs and inter-stringer spaces. Outboard of the tanks the inter-spar ribs are very light warren-girder braced mem- bers. Stringers are Z-extrusions top and bottom, and are '' fanned '' at roughly £ deg increments relative to the front spar, the pitch being slightly closer for the top stringers (Left). The wheels retract forward upinto nacelles, the jack extending for this operation, and the diagonal brac-ing strut running forward in rails at the head. The undercarriage is gravity-lowered and drag locked—this also applying to the nosewheel. (Centre). Detail of split flapoperation. The rail-section push/ pull rod is actuated by a hy-draulic jack and, as it moves outboard, the toggle links lowerthe flap. (Above). Detail of theunique fabric attachment used on control surfaces.
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