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Aviation History
1962
1962 - 0734.PDF
732 FLIGHT International, 10 May 1962 VICKERS VC10 . . . on each wing trailing edge. All sections are operated by two electrically-controlled hydraulic motors, one supplied by each of the hydraulic systems, and driving the flap torque shaft through a differential gearbox and reduction gear. At each flap unit, irrevers ible screwjacks are driven through bevel gearing from the torque shaft to extend the flap trolleys, which run on tracks on support members extending from the wing ribs. Four flap positions can be selected: up, take-off (20°), approach (35°) and landing (45°). For normal flap-operating speeds both motors are required, but one motor can operate the flaps at half-rate should the other system fail. Four slat sections in each wing extend over 90 per cent of the semi-span; they are omitted from the innermost portion so that any stall will start at the wing root. Somewhat similarly to the flaps, the slats are operated hydraulically by two motors through a torque shaft, bevel gearing and eight screwjacks. The slat selector lever is normally linked with the flap selector so that normally flaps and slats act together; if necessary, the slat selector can be isolated from the flap selector by withdrawing a spring plunger. The slats have only two positions—up and take-off. In the case of both slats and flaps, symmetry is ensured by synchros fitted on certain of the operating screws, which sense deflections set up in the torque shaft. Any out-of-balance voltage is used to operate isolating valves on the hydraulic motors. Fuselage While the structure generally follows established Vickers-Armstrongs practice, a breakway from tradition occurs in the much more extensive use of large machined skin panels along the sides of the fuselage. They incorporate emergency exit and window cut-outs, and provide an excellent means for minimizing concentrations of stress around the openings. These large panels are routed from solid billet by Cramic Aircraft Components Ltd on their 40ft-bed routers. All fuselage skin is stiffened by riveted continuous top-hat or Z-section stringers, and loads are transferred from the skin to the main channel-section hoop frames, which are also continuous, by secondary shear-cleats attached directly to the main frames and skin, and notched to accommodate the stringers. The latter are cleated to the frames, which are spaced at about 20in. At the centre section, four steel fuselage frames are attached rigidly to the four shear webs of the wing torsion box. The centre- section torsion box is installed in a large fuselage cut-out, in the aft part of which are the main-undercarriage bays. To maintain structural continuity a substantial central keel has been introduced, separating the two undercarriage compartments and attached at its forward end to the centre section. The keel is a deep built-up box section with stiffened 16 s.w.g. light-alloy sheet side members, and a box-section bottom member of 0.25in light-alloy plate attached to light-alloy beams and substantially stiffened on its underside. This bottom member extends forward under the centre- section torsion box. A pressure floor, built over the centre-section torsion box, extends between stiffened pressure bulkheads in the lower parts of the frames at each end of the centre-section cut-out. The nosewheel bay is unprcssurized, and has integrally machined and stiffened roof and sidewalls to contain the pressure loads. At the rear of the fuselage, two machined frames support the powerplant cross-beams, and three slanting machined frames provide attachment points for the fin and tailplane, both of the latter being conventionally built-up on three-web torsion boxes. Aft of the slant frames is the rear pressure bulkhead. Projecting from each side of the fuselage are two forged channel-section "half-spectacle" beams of S.99 steel, connected within the fuselage by the engine-mounting beams which have H-section booms and light-alloy shear plates. The spectacle beams form the front and rear members of the engine-bearer torsion box, which is skinned with stainless-steel sheet. Generally, the fuselage floor panels are built-up light-alloy structures. Over the centre-section cut-out, where good thermal and acoustic insulation is required, the floor is of light-alloy/balsa sandwich. Undercarriage The undercarriage is of Vickers-Armstrongs' own design and construction, and comprises two inwards-retracting main bogie units, each with four wheels fitted with hydraulically operated disc brakes, and a forwards-retracting twin-wheel nose gear. The shock-absorber strut of each main unit is suspended on a hinge tube which spans between a machined-steel undercarriage beam and the wing torsion box. The retraction jack is fitted between levers on the hinge tube and the support structure at the root of the wing. Up and down locks engage mechanically under spring pressure, but are unlocked hydraulically. Hydraulically-operated doors arc sequenced to unlock and open before the down-lock or up-lock is broken, and to close after the undercarriage is locked up or down. Retraction is controlled by a lever-operated selector switch; an alternative hydraulic selector is also provided. Hydraulically operated steering jacks provide for steering anc turn the nosewheels through ±70°. A spin brake in the nosewheei bay contacts the nosewheel tyres during retraction to stop rotation. In emergency, all units can be lowered under gravity by levers which mechanically "break" the up-locks. If necessary, the mam units can be lowered to the down-locked position by hand winding. Dunlop wheels, tyres and brakes are fitted, the latter being con trolled by Maxaret anti-skid units. Powerplants Compared with the Rolls-Royce Conway turbofans ("by-pass jet" engines) currently in service, the Conway RCo.42 Mk 5404 has double the by-pass (cold/hot) ratio, or 0.65 instead of 0.3. Intake noise is very satisfactory, and, despite their great power, these engines can be operated without suppressors without exceed ing the noise level of present jet liners. The current RCo. 12 Conway engines achieved an overhaul life of 2,400hr within two years of entering airline service; since the RCo.42 has the same high- pressure section—compressor, combustion chamber and turbine- it promises to give equally good service. Thrust reversers are fitted on the two outboard engines. Engine auxiliaries include a hydraulic pump, English Electric (Sundstrand) constant-speed drive (with its own oil system) and alternator, cabin-air compressor, and pneumatic engine starter. For ground-cooling of the alternator and c.s.d. oil cooler, a jet pump drawing air from the engine h-p compressor is brought into use automatically by switches on the main undercarriage. Services from and to each power unit are taken over the top of the engine, all electric cables, fuel and hydraulic lines passing over the inboard engines running in fireproof ducts. Stainless-steel fire walls isolate the fire zones of adjacent engines from each other and from the fuselage. A two-shot fire extinguishing system is provided for each engine, supplied by pairs of methyl-bromide bottles housed in a fireproof box on the outer side of each outer nacelle. Either bottle can serve either inboard or outboard spray rings. Engine- fire detection is by Graviner Firewire. Access to the powerplant is provided through large hinged and removable panels, the entire bottom cowling being hinged for engine removal. Attachment points for the engine mounting links are on the forward and rear beams of the powerplant torsion box. For removing or installing the engine, an electrically driven winch unit can be positively located on top of the nacelle torsion box. The winch can also independently handle the engine exhaust systems. Powerplant of the Super VC10 is the RCo.43 Mk 550, in which thrust is raised to an average figure of 22,5001b by slightly increasing h-p. shaft speed (from 9,966 to 10,172 r.p.m. at take-off). In the Super VC10 thrust reversers will be fitted on all engines. Flying Controls The flying-control systems are particularly weil illustrative of the underlying philosophy of safety which character izes the entire design of the VC10. After a thorough investigation of many alternatives, the decision was taken to adopt fully powered controls, without manual reversion. The elevators, ailerons and rudder are each split into independent sections driven by separate Boulton Paul electro-hydraulic power control units (p.c.u.s). There are two portions of elevator on each side of the centreline, two sections to each aileron and three parts to the rudder. In the worst possible case, with any one section of each surface running away to maximum deflection, the remaining portions can still maintain control of the aircraft. Since redundancy is thus obtained by division of the control surfaces there is no duplication of p.c.u.s, and the latter are designed to have maximum simplicity and reliability. All p.c.u.s are basically identical, and incorporate experience gained with the Valiant, Vulcan and other aircraft. Should any p.c.u. become inoperative, aerodynamic load will return the surface to the neutral position where it will be retained by a mechanical lock released by the loss of servo hydraulic pressure. In addition to these electrically controlled surfaces, control in pitch and roll can also be exercised by a variable-incidence tailplane Text continued on page 738 after fold-out drawings of VC10
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