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Aviation History
1975
1975 - 0079.PDF
RIGHT International, 9 January 1975 43 back to the door and the window frame), floor and cabin top are added. The engine, exhaust, bearers and noseleg and wheel are assembled as a module and bolted to the fuselage, together with the main undercarriage, after it is removed from its last jig, making a unit which can be moved on its wheels. The wings are built nose-down in vertical jigs. The nose ribs and skin are riveted together, all holes in ribs and skins being pre-drilled full-size. The matching of such pre-drilled holes is quite an achievement and calls for a high standard of accuracy, but if it can be reliably main tained it gives a substantial reduction in assembly time. The spar channels and angles are riveted to the nose- ribs; inter-spar ribs and skins are added, again pre-drilled, and the section is closed by the rear spar, aileron and flap shrouds. Both the first Cherokee and the Cessna 150 appeared in 1959-60. The Cherokee was a new design, but the 150 was evolved from previous Cessna two-seaters. It was a redesigned version of the tailwheel 140A of 1949, which itself was a metal-winged development of the 1946 fabric- winged 140. An example of the evolutionary development of the Cessna range is apparent in a step which could have involved major redesign—the change from the strutted to the cantilever wing on the 177 and Cardinal. In fact only local redesign was necessary, more bending material being added to the impaired spars and a massive machined carry-through spar being incorporated in the cabin roof. Externally, the only obvious change to the aircraft is the deletion of the struts. The Piper plant at Vero Beach, Florida, where the Cherokee series and Senecas are built, is quite different from the Cessna facility. One gains the impression that an ideal component route diagram was drawn out and the buildings designed around it, allowing a factor of two* or three on floor area for expanding production. The plant is relatively new, being built from scratch to accommodate a production rate of 15 Cherokees per day. While Cessna aircraft evolved gently through several decades, Piper brought in the entirely new Cherokee/ Seneca range to replace its low-cost, tube-and-fabric Colt, Tri-Pacer and Caribbean aircraft and to compete with the all-metal Cessnas. A long wing was chosen, maybe to con tinue the successful Comanche image, but although lessons in production technique must have been drawn from Comanche experience the structures have little else in common. Thus the Vero plant was designed to function as a separate entity and its success is apparent in the number of Cherokees flying throughout the world. That this plant is fairly young is apparent in many ways. There have been few enough variations in the product since its inception to leave the production route clean and tidy. Many components are bought out, and despite the introduction of the Cherokee 6 and Seneca there is still ample floor space for further developments. The initial production planning appears unchanged and entirely logical, and the number of common components used in the various models is quite remarkable. Compared with Cessna production, the earlier development stage of the Cherokee is apparent in the assembly sequence. Piper builds in airframes with few of the non-structural details pre-assembled. Cessna are bringing much more complete modules to the final assembly. The scuttle is a particularly good example. Cessna assembles many of the control items, rudder pedals, brakes and ancillary engine and instrument items to the scuttles before they are offered to the airframe jigs, when access is easier and expensive "messing-about time" is reduced. Together with the suppression of unnecessary hardware items and the Previous page: stages in Cessna ISO fuselage assembly are, top, rear fuselage jigging; centre (eft, a completed rear fuselage; centre right, the scuttle subassembly with many control details already fitted. Below this is shown the fuselage final assembly jig and bottom right, a complete fuselage shell. Bottom left is a stack of machined carry- through spar members for Cessna 177s and Cardinals Piper fuselage subassemblies: top, a powerplant module; centre, rear fuselage cones; bottom, a cabin module in its jig. The materials rack can be seen to the left reduction of the number of production operations, such reduction of assembly time is the key to the low-cost aircraft. Manhours in the USA represent hard and predictable figures. It cannot be said that shopfloor employees work particularly quickly; rather they work steadily, beginning on time, taking only the agreed time for breaks, and having considerable pride not just in the quality of their work, but in the factory output rates to which their particu lar effort is geared. The standard of living which they enjoy is sufficient evidence to them of the value of their work. While a visitor touring the plants has no trouble getting explanation of the production processes from operatives, he will find that they will not turn away from their work for longer than their particular job can be allowed to fall behind the predetermined flow of parts to the final assembly. Manhour figures, being such powerful contributors to the cost and saleability of the products, are engraved on
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