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Aviation History
1958
1958 - 0622.PDF
638 ' British and foreign tanks, bombs and rockets which can be accommodated under the wing of the standard Hunter F.6. The list is not completely exhaustive. 230 imp gal 100 imp gal 100 gal NAPALM Mk12 RAILS 12x3in RP WITH LIGHT HEADS 4 x 3 in RP WITH6Olb HEADS C2® C3 3X5inHVAR OERLIKON ,BOFORS,ORHISPANO ROCKETS & LAUNCHERS 50Olb BOMB 4OO kg BOMB 200 kg BOMB 37x 2 in R.P. OROTHER HONEYCOMB (&! PACKS w 6x3in R.R 251 b PRACTICE HUNTER F.6 . . . Wing structure follows fairly closely the principles employed inthe fuselage, plate and extrusions being combined into both trans- verse and longitudinal stiffening, covered with large skin panels ofrelatively heavy gauge rolled to a curvature. Rib stations are lettered and numbered, those ahead of the main spar reading(from the root rib A) 1,2,3, G, H, J, K, L, M, N, P, Ql, Q2, and R. The main frame of the wing is formed by die front and rear spars,the undercarriage girder (lying diagonally between the two) and the strong ribs A, G, M, and R, which have plate webs and extrudedbooms. Rib A is the root rib lying against the stub wing; rib G is cranked aft of the main spar to fie normal to the undercarriagegirder; rib M carries a butt strap for chordwise wing-skin joints; and rib R closes the main spar, carries a butt strap, and mounts theaileron Hydiobooster and the spar extensions holding the end rib and detachable wing-tip and, to port, the pitot boom. Inter-mediate ribs are simpler flanged plates with lightening holes. Both main and rear spars are simple plate channel-sections,though extruded booms replace flanges in die main spar inboard of rib J. This structure is progressively strengthened, having steelbooms inboard of rib E and terminates in the splayed fork and lugs widi which it picks up die steel fittings on fuselage frame25. The securing pins are tapered steel, with split bushes, fastened by a nut and cup washer. Drag loads from die wing are taken bythe top skin and resisted at the rear wing pins on fuselage frame 32. The rear spar joins the undercarriage girder near die pin joint. An undercarriage pivot bracket is built into the space betweenmain spar, undercarriage girder and rib G, the leg and part of the wheel retracting into the space between spar and girder. The deck-ing over die bay is supported by top-hat-section stiffeners inter- spersed with steel and alloy extrusions. A goodly quantity ofhydraulic, electric and fuel system leads are concentrated in die bay within easy reach from die ground. Main wing loads aretransferred from the rib-and-spar complex outboard of rib G, to the structure ahead of the spar, heavy steel gusset plates servingto take bending loads across the crank in rib G itself. Aft of the rear spar, die decking over the flaps is held bytapered top-hat ribs mounted on forged brackets and covered by plate reinforcing near their roots. This light decking is skinnedboth above and below. Brackets for flap hinges and operating and synchronizing jacks are of plate and forgings. Similarly, theaileron shroud is supported on forgings, with hinge and actuating brackets of composite construction. The ailerons themselves aremade up of plate ribs and stringers based on a channel-section spar, with lead mass-balances in the nose sections. The port aileronalso carries die trim tab on a piano hinge, with it* electric actuator in the aileron itself. The flap structure is based on a tubular spar to which arethrough-bolted forgings forming either roots for the tapering top- hat section ribs, or hinge and operating brackets, or both. Trail- FLIGHT, 9 May 1958 ing edges are stabilized by doubler strips and a perforated sheet isriveted over the ribs. The flap surface itself is a single skin. Some slot effect is provided for in the geometry of the hinge brackets. To form the main wing-skin, very large panels of 10 s.w.g. alloyare flush-riveted to ribs and stringers, diree of diem covering each wing surface out to rib R. They are rolled to contour and butt-jointed along die leading edge, die inner surface of the joint being formed by a butt strap. Outboard of rib R, 14 gauge is used; anddie decking over die flaps is skinned widi 18 gauge sheet. The pylons, bodi inboard and outboard, are based on a cast sole-plate contacting tank or bomb and supported from extruded flanges, bolted to the wing skin and internal structure, by extrudedchannel-section stringers. The pylon is covered widi a sheet skin. Suspension of bomb or tank is by a Vickers bomb-slip which canbe lowered to pick up the store by a built-in screw-jack operated from above the wing. A jettison mechanism and die fuel by-passvalve are located within the pylon. Rocket rails of die standard Service Mk 12 type are mounted on posts quickly secured at rein-forced cutouts in both upper and lower wing skins. Two posts hold each rail and diree of die four pairs of posts in eachwing are located between ribs M and R. Bolts retaining die pylons are screwed into blind nuts held in brackets specially positionednext to the relevant ribs. In the case of the outer pylon, rib Q is duplicated ahead of the spar as Ql and Q2 in order to accom-modate these brackets. The saw-toodi leading-edge extension which is now becomingincreasingly familiar on several marks of Hunter is a simple retro- spective modification. It is in fact a single sheet wrapped roundshort plate ribs and riveted directly onto die wing skin between ribs R and J. The trailing edge of this skin is slightly tapered, butkept thick enough to accommodate rivet heads. • _-Z\^-.^J'[rS: .':'- SYSTEMS - '"•'•• •••••.- -.- ,-, Powered Controls. The powered control system of die Hunterhas gone through a number of variations and modifications, each providing some distinct improvement in handling, and resultingfinally in a control system which leaves litde to be desired. The main changes have brought die horizontal tail control from aboosted elevator and electrically trimmed tailplane, dirough fully powered elevator, to fully powered elevator combined with afollow-up tailplane. As reported by C. M. Lambert in his flight evaluation of the Hunter two-seater (Flight, May 17, 1957), it nowremains fully effective and light even in the most difficult condi- tions at transonic speeds. The rudder is purely "manual," widi an electric trim-tab tocounteract any unusual asymmetric conditions. This tab may also be connected to an autostabilizer made by Newmark. Thesurface is hardly used at high speeds. Full power and plain spring feel are applied to the ailerons, with manual reversion and auto-matic doubling of mechanical advantage as a stand-by. For this eventuality, also, an electric trim tab is provided on the portaileron to relieve out-of-trim forces. With power engaged, lateral trim can be adjusted by offsetting the centre position of the spring-feel unit which is located on die control column itself. Aileron feel is substantially linsar, with a maximum force of 8 lb at fulldeflection; and the springs are preloaded to provide positive centring and a slight break-out force. The trim tabs are poweredby Rotax actuators. The hydraulic control-surface jacks are Fairey Hydroboosters(one each for ailerons and elevator); and each is anchored to the airframe by a pawl engaging in a slot in the piston rod. Thepilot's input rods actuate die valve and the body of the jack moves the surface. The pawl is held in engagement by the main hydraulicsupply pressure; and when this drops below 400 lb/sq in it auto- matically disengages under spring force. The pilot then movtsthe surface by the direct mechanical link through rods, jack valve and body. When power is selected for ailerons or elevator it is possible forthe pawls to fail to engage the slots and simply to clamp the piston rod. Warning dolFs-eyes in the cockpit are arranged to showproper engagement by changing from white to black only when the pawls have gone fully home. If the latter simply clamp, thepilot has the positive indication of a white doll's-eye and in this case the controls will revert to manual when the selector switchis released. The misalignment can be remedied by applying a hefty push to the stick to slide the piston past the pawl until theslot is engaged. When such a situation arises during re-engage- ment in flight, the necessary stick-rocking can be accomplishedwithout producing untoward aircraft responses. , The doubling of mechanical advantage when the ailerons aremanually actuated is achieved by varying die length of a tele- scopic lever in the control-rod circuit. Spring pressure keeps thelever short, thereby providing greater mechanical effectiveness for manual flying, while hydraulic system pressure is applied tolengthen it when power is in use. When loss of hydraulic power automatically allows the lever to shorten a°ain, only half aileron-travel is available to die pilot; but this does not additionally hamper
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