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Aviation History
1957
1957 - 0440.PDF
442FLIGl Fig. 5 (left, above). Finishing work on firewall and engine mounting of aircraft No. 37. Fig. 6 (right). The part of the fuselage assembly line at which rear door, metal skin, glazing, engine bay and tail unit are added. BUILDING THE E.P.9 Fig. 7. Cutting mainplane rib blanks on a Wadkin radial-arm router. The metal is "stacked" on the Hydulignum routing tem- plates, so that several are cut at once. Fig. 8. Sheet-metal de- tails and drill jigs: in the foreground are leading- edge ribs in their metal- bushed Hydulignum jigs. In the background, from the left, are a main-rib rear section and the drill jig and parts for (extreme right) a completed main leading-edge rib. Fig. 9. Drilling the main spar. A Dexion frame- work carries angle-iron jig framework upon which the parts are held by modified Speedtool clamps, here seen keep- ing the extruded spar flange in place. The drill plate is of bushed Hydu- lignum stiffened by an angle-iron spine. Fig. 10. Jig-drilling a rear spar-tube for the rib rivet holes. On the other side of the bench a lead- ing-edge tube can be seen in its jig. ing a lanolin compound is used to prevent internal corrosion.From the paint shop the fuselage framework goes on to the fuselage assembly line—which is really the beginning of the finalassembly line. It is supported in flying position by a tail trestle made from Dexion angle-sections and by jacks at the under-carriage fittings. Most of the work consists in offering up pre- fabricated details, but there is some fitting to be done. The firewall—complete with engine control cross shafts—is put in place to form the front boundary for the skin panels. These, having no compound curvatures, are made in the flat oflight-alloy sheet, to which drawn stiffeners are Pop-riveted. The cabin roof, apart from the cockpit roof-lights, is of metal—andhas been made more robust than the rest to withstand rough usage from the mechanical hopper-filler. The cabin floor is a robust structure, since there are no mainstructural tubes across it between the front and rear portal" frames. Under-flopr box members are attached to the Flexoplyfloor itself, which is a sandwich of end-grain balsa and plywood with metal facing. At cut-outs and other points of stress con-centration in the floor there are spruce inserts. The cabin floor fits in as a unit, but the cockpit floor is in port and starboard sec-tions—made up as complete assemblies with the flying controls— and is mounted after the fore-and-aft central girder of the cockpithas been fitted. This latter is a box beam with flanged lightening holes and it serves as the support for the flap lever. The instrument panel and the engine control assembly are otherunits which are added complete. The engine bearers, of simple classical welded form, are bolted to the front of the firewall andthe ignition harness, and at this stage details are added (Fig. 5). Meanwhile the rear of the fuselage has also been receivingattention. The tail boom, from just behind the hopper hatch to the tailplane, is fabric covered. To give it a good shape, spruceformers and stringers are first attached to the tubular framework. There is no sewing after the fitting of the "bag" by adhesive.The fuselage goes to the paint shop for doping and an external coat of chromate protection on the metal-skinned areas. Next, the tailplane, fin, elevator and rudder are added (Fig. 6).The fuselage then moves down the line, gathering control runs, the rear clamshell door, undercarriage, tailwheel and so on-—until it is complete and ready for the wings. The engine is added at a latish stage, since customers have the choice of modelswith plain or chrome-plated cylinder barrels. Each airframe, nevertheless, receives its cowling panels, which are, of course,attached to the bearers; and the engine accessories, inter-cylinder baffles, air filter box, etc., are prepared in readiness for quickattachment to the engine. The Wings. The parallel-chord wings are of extremely simpledesign for rapid, economic manufacture. As the whole of the trailing edge is hinged, in the form ofslotted flaps and ailerons, the rear of the main structure is of shroud form. There is a single spar at about 30 per cent chord,with light tubular members at the leading edge and the shroud to hold the closely-spaced ribs together. The L.72 light-alloy ribs are divided into front and rearparts. The main ribs are press-flanged from routed blanks and are stiffened by riveted channels. The intermediate ribs, andthose of the tank bay, are made up from pressed channel flanges. Edgar Percival Aircraft cut the blanks on a Wadkin router(Fig. 7). The cutting jigs are of Hydulignum, with mild-steel guide-templates. Skin rivet holes are drilled from the cuttingtemplates. The parts are sent out with their Hydulignum press tools for flanging on a rubber platen press, and when they comeback they are put into simple Hydulignum assembly jigs (Fig. 8) for drilling and preparation for riveting. It will be seen in the
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