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Aviation History
1956
1956 - 0776.PDF
776 FLIGHT WESTLAND WYVERN . . .,, :•..,. -:^ :^Y offset to port, is a Rotol gearbox mounting two Integral hydraulicpumps, a Hymatic compressor, a Pesco vacuum pump and two 3,000-watt, 24-volt generators. The second generator is locatedin a small port-side bay in the original front fuselage fuel-tank volume, the firewall haying been appropriately re-shaped, and adivided air-intake duct incorporated for cooling. In the centre the firewall is formed as a truncated cone shroudto the jet pipe, flanking which, on the rearward face, are mounted a pair of 12-lb Graviner extinguisher bottles serving spray ringsaround the reduction gear, combustion chambers and the region immediately forward of the firewall. A third bottle mounted onthe pilot's bulkhead is connected to spray rings around the jet- pipe bifurcation and in each of the wheel wells. The lower flanksof the firewall are formed into lobes, behind which are carried Delaney Gallay oil coolers. Oil temperature is sensed by aTeddington temperature-control unit, at the direction of which the outlet flaps are moved by Western Manufacturing electricactuators. Provision is made for a B.T.H. twin-breech cartridge- starter. The pilot's bulkhead is staggered and the front portion formsthe rear wall of the cell for the Marston Flexelite bag-type saddle tank which sits on the engine-mounting structure. Forward ofthe rudder pedals the bulkhead is pierced by a large oval cut-out for the jet-pipe bifurcation, and incorporates a heavy horizontalmember bridging the upper rearward engine-mounting pick-up points, and a pair of equally massive vertical struts between theupper and lower pick-ups. From the top pick-ups, large box-form "longerons" run back to frame members of smaller section whichstand between the cockpit rails and the top boom of the main centre-section spar. The Martin Baker Mk 2B ejector seat issupported on a box beam spanning the major frames just men- tioned, the cockpit floor being carried on spanwise members oftop-hat section. The under-floor space is given over to the jet- pipe bifurcation, the folk uunks and twin tailpipes being Alfoil-lagged units of Lucas manufacture, while cooling air (ducted from the engine oil-cooler intakes) passes through fishtail vents underthe floor structure itself. Air bled from the engine compressor casing can be used todemist the windscreen or, by means of a heat exchanger, can supply a pilot's ventilated suit. The windscreen itself, previouslycurved, is now flat and of laminated Triplex, and the canopy is a re-shaped one-piece Perspex unit, reinforced with Fibreglasslaminations and a metal rear section. A Dunlop hydraulically operated windscreen wiper is fitted. That part of the fire-wall which is formed as a shroud to thejet-pipe is flange-bolted to an expansion bellows at the joint of the "short pants" bifurcation, the bellows accommodating anydifferential deflections between the power unit and the airframe. The extension pipes are individually attached to the fork branchesby clamping rings, and the forward part of the assembly can be treated as a cantilever off the firewall. Axial expansion is accom-modated by spigots on the sides of the tailpipes, registering in yokes on the sides of the fuselage which carry the vertical loads.Side forces are accommodated by pivoted radius struts between the branches of the fork trunk, each strut being joined to a centralslide unit, fore-and-aft movement of which accommodates lateral spread of the forks while at the same time providing lateralstiffness. Between the tailpipes is housed a fuel collector tank above which, and aft of the cockpit, is accommodated the rearfuel tank; each of these is a Marston Flexelite bag-type unit. At this point it is appropriate to refer to the fuel system as awhole. In addition to the fuselage bag-type tanks, part of the A Wyvern S.4 being prepared for catapulting. WYVERN: LEADING DATA Dimensions: overall length, 42ft Ojin; height (wings spread), 15ft; height (wings folded), 18ft 1.8in; gross wing area, 355sqft; aspect ratio, 5.45; overall span (wings spread), 44ft; overall span (wings folded), 20ft. Weights: empty weight, 15,6O8lb; gross weight, 21,2O0lb; overload weight, 24,500 Ib; wing loading, S9.7 Ib/sq ft; power loading, 5.77 Ib/sq ft. Performance (without external stores): max. speed at sea level, 333 kt; max. speed at 10,000ft, 331 kt; cont. cruising speed at 20,000ft, 303 kt; initial rate of climb at sea level, 2,350ft/min; service ceiling, 28,000ft; diving speed, 478 kt E.A.S.; range, 785 nautical miles. Armament: four 20 mm wing-mounted guns and (as alternative loads) 16 rocket projectiles, a torpedo or three 1,000 Ib bombs leading edges of the outer wing panels are formed as integral tanksand these, pressurized from the exhaust side of the vacuum pump, are piped to the rear fuselage tank which has a direct line to thecollector tank. In the latter is a float valve serving the front saddle tank so that, when the rear tank is empty and the level inthe collector has dropped sufficiently, fuel from the saddle tank is automatically transferred. In this way fuel consump-tion has a minimum effect on the trim of the aircraft. Following instances of fuel starvation on catapult take-off, a recuperator unitto remedy this was incorporated in the fuel system. Simmonds Pacitor gauges are fitted in all the tanks, and fuel feed is effectedby Pulsometer pumps in the integral wing tanks and a Self- Priming pump in the collector tank. The main fuel cock is aSaunders unit, Mauley and Regulus pressure-regulating valves are used, and the non-return valves are by S.P.E. and Flight Refuel-ling, Ltd. At the wing-fold joint, Exactor couplings are employed for the fuel and pressure lines. As a structure, the fuselage is a monocoque in two sections,united at a transport joint about 4ft behind the centre-section trailing edge. The interior of the rear part of the front fuselageand the front part of the rear fuselage accommodates equipment, chiefly radio and electrical items forward of the transport jointand camera units aft. Access is provided through a door 14in wide by 16in high in the port side to the rear of the transportjoint. Although in the prototype Wyvern the fin was built virtuallyintegral with the fuselage, production machines have separately constructed fin units with detachable tips. External profile jigs areemployed in order to obtain accurate surface contours, a method which is followed in the construction of almost all the aerofoil andcontrol surfaces. In the case of the fin, a single spar with extruded beams and a plate web is used, and the port and starboard surfacesare joined at the leading edge centre-line with an internal butt- strap. The chordal ribs are integrally swaged diaphragms whichare riveted to the free flanges of angle contour members, spot- welded to the skin. This system has the merit that the designedcontour is faithfully reproduced with an external surface unmarred by riveting. At the foot of the fin-post, or spar, is a 75-ton-steel casting inwhich is pivoted the Dowty levered-suspension tailwheel strut and to which are anchored both the strut supporting the tailplanespar and the A-type strut of the arrester hcok. The latter carries a fairing continuing the profile and section of the fuselagetail. The hook is operated hydraulically, the circuit providing for pressure relief and hook damping. Hook and tail-wheel loadsare distributed into the fuselage structure by means of two box "longerons" which run forward to a pierced diaphragm at theforward end of the tailwheel well, thence continuing forward with wedge-fonn run-out members to the stringers. The rudder structure is essentially similar to that of the fin, butforward of the spar the nose is formed as the beak of a Westland- Irving balance, along the leading edge of which are screwed mass-balance weights. The trailing-edge tab is purely a trimming surface and is operated by a Metrovick linear actuator in the baseof the fin. The main control transmission is by push-pull tubes articulated on swinging links, and the static friction of the wholesystem is very small. As for the fin and rudder, so for the tailplane and elevators,insofar as essential structural form is concerned. The tailplane spar is supplemented by a sub-spar bridging the root ribs, andattachment is made to the fuselage with pin-jointed fork/lug forged fittings. The elevators are of the Westland-Irving nose-balanced type, with horn balances at the tips. The tab of the port elevator is a spring servo surface, while that to starboard is atrim tab mechanically actuated by cable transmission from the cockpit hand-wheel. To reduce elevator stick-forces, the leading-edge skins of the elevators are drilled with a series of pressure- equalizing bleed holes. It is in the wing centre-section, perhaps, that the inherentstrength of the Wyvern structure is most apparent. The booms of the main spar, for example, are about 4^in wide over theflanges, and the design incorporates a relatively large number of forged fittings. The centre section is a three-spar structure, thefront spar being furnished with machined steel booms over the central half of the span, multi-bolted to machined and extruded
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