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Aviation History
1955
1955 - 0695.PDF
m FLIGHT, 20 May 1955 The wing pick-up structure consists of a series of joints, theprincipal of which lie at the ends of the truncated reinforced frames, Nos. 31 and 35. These pick up the upper booms of theforward and rear torsion-box spars, the skin in these areas being heavily reinforced. Lying principally within the fuselage, butaft of the torsion-box, the mainwheel bays are enclosed by a box structure which forms the pressure bulkhead system at this point.Between the two bays lies the central trunk for the control and electrical cables and ducts running longitudinally under the cabinfloor. The control cable trunk continues forward through the main torsion-box junction. The shape of the windows was determined by the fact that itwas considered that most passengers looked downwards from the aircraft. In order to save weight, therefore, it was decided tomake the top of each window an arched structure, resulting in the overall triangular shape. A saving of 40 kg (88 lb) over rectangu-lar windows was effected despite the thickness of the double transparencies, which are 22 mm and 24 mm (0.87in and 0.95in).The tests carried out entailed the mounting of a single window in a small pressure chamber. In a straightforward test to destruc-tion the window broke at a safety factor of 15. Next, the window was tested after a cross had been cut in it with a diamond. It thenfailed at a factor of 10. A third window was then tried over 10,000 pressurization cycles in conjunction with a temperaturefluctuation of plus 50 deg C to minus 70 deg C. Once more, the safety factor was 15. A complete fuselage section including awindow and an escape hatch was subjected to 40,000 pressuriza- tion cycles and at trie end of this time no optical distortion orchange of crystalline structure could, it is stated, be discerned in the window. The window frames are drop-hammered parts. Wings > The wing-span is 112ft 6in with an effective surface of 1,579 sq ft.The chord along the aircraft centre line is 20ft 9in and, at the tip, 6ft 4.1in. The aerofoil section is N.A.C.A. 651212 and thesweep-back at 25 per cent chord, 20 deg. Dihedral is 3 deg and the angle of attack at the centre line, 2 deg. There is a washoutof minus 2 deg 11 min at the wing-tip. Effective area of the ailerons is 84.38 sq ft and the effectivechord 27.45in. Extending rearwards and downwards to 35 deg, the flaps have an area of 265.8 sq ft. The droop-snoot leading-edge has a maximum droop-angle of 15 deg. The wing ribs in each semi-span are numbered from 2 to 52,reading inwards from the tip. The principal load-carrying struc- ture, containing the integral fuel tankage, is a three-spar torsion-box to which are attached the seven drooping nose sections, two aileron sections each side and a total of eight flap sections. Arearward extension structure carries a dummy spar and flap and aileron hinges made up of Warren girder ribs covered withsections of skin reinforced by spot-welded and glued stringers. The main torsion-box is built up from die upper and lowerskins. The inboard wing skin is made up of two taper-rolled sections (5 mm to 2 mm: 0.2in to 0.08in) and die outer portionof a single constant-thickness section (2 mm: 0.08in). Span-wise stringers are flush-riveted to the skin on a fixture, after whichthe crescent-shaped quarter ribs are added. In this part of the wing the ribs are built up of four crescent-shaped sections rivetedto skin and to the diree spar webs. After the lower skin is built up with ribs and centre spar web,the upper skin (with the spar booms but without ribs) is offered up and the remaining rib sections inserted and riveted. The boxis then sealed for fuel tankage space. There are a number of access panels in the webs of the main spars to allow inspectionof the tanks and installation of pumps and pipes. The main undercarriage leg is mounted on a heavy triangulated structurebehind the rear spar, through which structure die loads are trans- ferred to the torsion-box by die specially machined booms of aheavily reinforced rib, No. 44. The flap sections are built up separately, the stringers beingspot-welded and glued with Araldite to the skin and joined into a continuous flap at each edge by the common mounting brackets. Looking aft along the fuselage from just ahead of the main wing- fuselage junction. The floor is reinforced above the mainwheel bay. 693 The starboard main gear seen slightly from the rear. The Hispano leg is supported from the wing torsion box by a massive triangulated structure. Immediately behind it is the false spar which carries flap and aileron hinges. The wheels, disc brakes (equipped with Maxaret) and dimpled tyres are by Dunlop. They are extended outwards and downwards on rails by screwjacks driven by shafts running span-wise along the false extreme rear spar. An automatic, mechanically actuated shroud coversthe flap slot as the flaps are retracted. It consists of long panels mounted on piano hinges with a spring linkage which a lug on dieflaps strikes or releases as flaps go up or down. The ailerons are shrouded and mass-balanced and actuated by a Servodynemounted between two closely spaced ribs which also support their central hinges. The air brakes are slats which extend above andbelow the wing; dieir lower (larger) section is operated by two piston-jacks and entrains the upper section dirough a mechanicallinkage. - Two boundary-layer fences are attached to the wing upper surface, running aft from a point just behind the forwardspar to a point just aft of the aileron hinge line, between the ailerons and flaps. The leading-edge flaps have a smooth outer skin and a cor-rugated inner skin, between which de-icing air flows, and are hinged at 15 per cent of the wing thickness. They are actuatedin the same way as the flaps. Tail Surfaces The vertical tail rises 14.4ft above the fuselage and has anarea, less dorsal fin, of 166.8 sq ft. Rudder area is 59.2 sq ft and the aerofoil section is N.A.C.A. 65011. The fin is built up to Coravelle wing assembly. The wing extension aft of the torsion box is nearing completion, with flap panels and part of the ailerons already mounted behind the dummy spar. In the background the fuselage of the second prototype takes shape. (Below) The tailplane torsion box in place on the fin-base, which is integrally built with the fuselage.
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