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Aviation History
1957
1957 - 1613.PDF
FLIGHT, 1 November 1957 701 AIRLINERS OF THE WORLD CONVAIR 88O Convair, Division of General Dynamics Corp., San Diego, California LAST of the major American transport manufacturers toannounce plans for a gas-turbine airliner, the ConvairJ division of the General Dynamics Corporation have with this machine elected to aim at the important medium-rangemarket (250 to 3,000 n.m. are quoted) with a four-jet aircraft weighing some 90 short tons and cruising at the very competitivespeed of 615 m.p.h. When it was first revealed, in the early summer of last year, the project was designated Skylark 600; laterit became Model 22, and it bore the name Golden Arrow. All these appellations have been superseded. : Virtually all responsibility for the development of the 880 is'being borne by the Company's San Diego division, where by the spring of next year one million square feet will be devotedentirely to this aircraft. Design was virtually completed early this year—after very extensive detail alteration—and actualmanufacture began with the machining of outer-wing spar booms in June. During October two special spar mills were installed,capable of handling the 80 and 90ft main spar booms, and Con- vair already have invested over $lm in CV-880 machine tools.The powerplant of the Convair jet is the General Electric CJ-805, the commercial version of the military J79; the 880 is the onlyaircraft to be designed around this engine. AIRFRAME The configuration of the CV-880 follows veryclosely the classical layout of the larger Boeing and Douglas machines. The low-mounted wing has a sweep angle of 35 degat 30 per cent chord, and on it are mounted the powerplants in widely spaced individual nacelles. The finely streamlined fuselageis of an oval section and the bogie main undercarriage units fold into boxes under the cabin floor. In the flying controls the aircraftdiffers from almost all other transports in that the ailerons are mounted much nearer to the roots of the wing than to the tips,and the horizontal tail incorporates an all-moving tailplane driven by a hydraulic motor and screw-jack. Fail-safe principles have been employed throughout the struc-ture. Although the wing is based on the same box-beam, plate- stringer structure as that of the Convair-Liner, it has threeprincipal spars and distributes the load through a multiplicity of relatively small elements. At the root is an additional auxiliaryspar which takes some of the chief undercarriage loads. Out- board of the outer engine pylons the centre wing spar is dis-continued, fail-safe integrity being maintained by the fact that the trailing edge is unbroken by any movable surfaces. Owing to its excellent fatigue-resistance 2024-T3 light alloy is widely employed in the airframe. It is used for the completeunderside of the wing, including skin (roll-tapered from 0.08 to 0.25in), spar booms and extruded stringers. The upper skin ismade of 7075-T6, with 7178-T6 used for most of the underlying members. The main undercarriage legs are hinged to the rear ofthe box beam and to a transverse member joined to the wing box and fuselage; the leg is designed to tear out without opening theintegral tankage (which is described in the paragraph on the fuel system). The leading edge contains two skins, between which is passedhot air for de-icing. Sandwich construction is widely used in the rear part of the wing and the movable surfaces in order to achievegood resistance to jet blast and noise. Each mainplane carries three sections of flap. Although double-slotted, the flaps run outon steel tracks in Fowler fashion, under the drive of spanwise tubes. Each flap section is of relatively short span. Fuselage Like the DC-8 this has a cross-section formed fromtwo arcs joined by flank-sections of very large radius; maximum height and width are respectively 149in and._138in. Most of theframes and stringers are Z-sections formed in 0.050in 7075-T6 alloy. A curious feature is the absence of stringers from a levelbelow the windows up to between 40 and 15in of the upper centre-line. Skin is everywhere at least 0.063in, and maximumhoop-stress is as low as 8,460 lb/sq in. Convair have' followed Boeing's precept in having one smallwindow between each pair of frames on each side, so that in most layouts there are two windows to each seat unit. Each windowmeasures 12|on high by about 9in wide, and comprises three panes of stretched Plexiglas 55; any one pane can bear full pressure andthe innermost is floated in rubber. Each window is carried in a single-piece aluminium-alloy forged frame supported solely by theheavy skin (up to O.lin.). Tear-stopping details are incorporated in all frame/skin joints. At every frame is provided a transversetie-beam across the fuselage on which is laid the metal-sandwich floor. A particularly ingenious feature is the final design of maindoor. Wider at the top than at the bottom, and of wedge section to dove-tail into its jamb, it is raised vertically on slotted tracksbefore being freed for normal outward opening. A complete fuselage is to be tank tested. Already an outstand-ing fatigue life has been demonstrated during extensive testing of details, particularly after stress-concentration by saw-cuts orjavelin-type guillotines. Empennage Design is fairly conventional. The fin has three
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