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Aviation History
1945
1945 - 0761.PDF
APRIL igTH, 1945 FLIGHT 4*5 which is a double-walled bea-m, and the upper half tubular,which picks up to the head of the tail-wheel leg. This leg contains the oleo-pneumatic shock absorber and self-centringcams, and is anchored to a cross beam pivoted in ball bearings • at each side of tne tail structure. The tailplane is a straightforward structure of two shallowchannel-section spars stiffened by extruded strip laminations at the edges, the main (rear) spar being continuous throughoutits span, whilst the nose spar is in two parts joined on the centre line Attachment lugs for securing the tailplane to thefuselage tail structure are built-up parts on each of the spars, and the normal tailplane structure is stiffened locally byriveted-up boxes at the pick-up points. Pressed sheet frames and nose ribs are riveted chordwise to the spars, and thestressed-skin plating is riveted to both, being stiffened span- wise with Fig. 2 section stringers. Ball-bearing Hinges Each elevator i* pivoted on two ball-bearing hinges, theoutboard pair of which are earned op forged brackets bolted to the plain tailplane spar. The inboard hinges are carriedon stirrup brackets bolted on the fuselage tail structure, these brackets also serving as supporting" members for the miniaturegear box through which trimming control is transmitted via universally jointed torque shafts to the trim tabs set in theinnermost portion of each elevator trailing edge. Elevators have channel-section spars to which are attached pressed sheet ribs, and forward of the spar at rib stations are Mfcnose formers, also of pressed steel, to which the single-piece * nose skin is riveted. The inboard ends of the elevator sparsterminate in, fork-end forgings which are pinned to the short length of torque tube spanning the fuselage; a drop arm from this torque tube is linked to the control rod from the cockpit. Mass balancing is incorporated inside the aerodynamic hornbalances at the elevator tips. Very simple construction is employed in the fin, which hasa main (rear) spar abutting the rudder and a front raking spar to which the leading-edge ribs and skin are riveted. Inter-sparribs are of pressed steel, and both spars are of channel section. Attachment to the tailplane is by four built-up lugs, two oneach spar, secured with expanding-bush bolts. The rudder is the only fabric-covered surface on the Firefly,and even then is not wholly so covered. The spar, or rudder post, is a plain channel to which are riveted built-up Warren-girder ribs attached at the rear to an ovalrBection trailing edge TAIL WHEEL STRUT WITH INTERNAL OLEO-PNEUMATIC SHOCK ABSORBER r ail wheel retraction mechanism, showing the compound breaker strut, up and down lock latches, cross-beam car- riage for leg, and wheel fairing door-operating linkage. FULLY CASTERS G TAIL WHEi L "* tube, but the nose portion of the rudder is of similar metalconstruction to that of the elevators; in addition, the top tip incorporating the small horn balance is also metal covered.The rudder is swung on three ball-bearing hinges, the topmost carried on a forged bracket mounted on the fin rear spar, andthe lower pair mounted directly off the fuselage tail structure. Between these lower hinges is carried the screw jack. It might with advantage be noted here that the staticfriction in the control linkages is the lightest that we have yet experienced. All control surfaces are hinged on ball bearings:all linkages are rod, carried in three-point ball-bearing lair- leads; and all pivot points in the linkage run in ball bearings.Thus the static friction resistance is virtually negligible. This, coupled with the careful counterpoising of mass and aero- A wide wheel track gives good stability on a carrier's deck The struts hanging down are for locking the wings when spread. dynamic balancing of the various control surfaces, makes thepilot's job in the Firefly a good deal less wearisome than is sometimes the case. The centre section is built up on the two lront and realspars, each of which is similarly constructed of plate webs with extruded flat strip booms joined to the' web with L-sectionjointing beads. At various stations where local stiffening is required (e.g., in the way of front catapult spools) extra flatstrips of heavy gauge are riveted over the L-section jointing beads, and vertical and raking stiffeners are also riveted tothe spar webs for increased rigidity. Front and rear spars are connected by pressed sheet ribs, which areheld literally by similar "distance pieces," but this construction is modified over the under-carriage retraction space, which is sealed by a built-up sheet "roof" between the various"gables and hips" in which the undercarriage structure nests when retracted. Undercarriage Retraction At first sight the undercarriage structureappears to be rather complicated, primarily because the head of each main leg is pivotedimmediately behind the front spar, so that the retraction motion has to be partially rear-ward as well as inward for the wheel to cleat the spar. This necessitated lateral and fore-and-aft breaking-strut bracing with universal pivot- ing, and as a result the geometry of motionappears involved. Actually it is fairly straight- forward ; the main oleo-leg is cross-pivoted to thefore end of a hefty tube running chordwise between the spars and supported in largeforgings. The head of the rear breaker strut is similarly cross-pivoted to the rear of the chordwisetube. A lever arm off the tube is connected to the end of the operating-jack piston rod. Actuation ot the jack thuscauses the tube to rotate, so swinging the undercarriage let? and the rear breaker strut transversely up or down as the casemay be. Rearward motion, however, is induced by a radius rod pivoted diagonally at its head and universally to thebreaking hinge portion of the rear bracing strut. The radius rod, by reason of its pivoted axes, causes the rear bracing strutto break and fold outwards, so inducing the main leg to swiug partially rearward during its sideways and upwards motion.The lateral breaker-strut is universally pivoted at its head and embodies at the breaking hinge the mechanical latching forlocking the leg in the down position. Up-locking is by a
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