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Aviation History
1940
1940 - 0074.PDF
28 JANUARY II, 1940. LARGEST TWIN-ENGINED CIVIL TRANSPORT Curiiss-Wright, with 7>^~PassenSer Pressure Cabin, Nears Completion This view of work in progress indicatesthe smooth contour, wide-angle wind- screens and the upward opening cabindoor. NOW nearing completion at the St. Louis works < ithe Curtiss-Wnght Corporation, the prototype 36-passenger civil transport designed with a pressure cabin will probably be test-flown this month. Formerly referred to as the " Curtiss-Wright CVV20," the company now seems to have dropped this designation in favour < i " 36 - passenger Substratosphere Transport."' The fuselage is complete except for interior furnishing; wing;;, flaps and ailerons are attached, and the double- row Wright engines have been mounted. The decision of the company, made some time ago, to build a transport of size intermediate between the sizes exemplified by the 21-passenger Douglas DC3 and the pro- totype DC4 to carry about 52 has been shown to be a sound one. The airlines have been so reluctant to order the 66,500 lb. DC4 that a contracted version of 50,000 lb. is going to be produced. Apparently, the estimates of traffic growth on the airlines in America were too optimistic, and caused a too sudden increase in aeroplane size. Neu> Features Incorporating many new features in its design, this Curtiss-Wright will be the largest civil transport operating on two engines. Only since the development ol the latest big engines has it become possible to design a 38,000 lb. 36-passenger aeroplane round two engines, a point in design which undoubtedly contributes towards piloting simplicity by reduction of the ever-increasing number of controls. The prototype is to have two Wright double-row Cyclone 14 engines which are rated at 1,600 h.p. for take-off, and the maximum speed so equipped is estimated at 243 m.p.h. But the latest Wright engine, the 18-cylinder Duplex Cyclone, about which information has not yet been released, may also be installed, and with its great power of something like 2,000 h.p. will add about another 30 m.p.h. to the top speed, as well as allowing the loaded weight to be increased to 43,000 lb. The fuselage design is developed for pressure-cabin and freight-space considerations. The cross section is denned by the intersecting arcs of two eccentric circles, suitably faired at the re-entrant angle. At the intersection of the two circles the floor is attached, and provides the neces- sary tension member to resist the resultants of the tensile stresses produced in the rings of the fuselage by the in- ternal pressure in the cabin. This design also has another advantage, in that it gives a cargo space large enough 1o be dignified by the name " hold," under the floor. Another compartment of 137 cu. ft. capacity is provided in the fuselage under the wing to take equipment such as bat- teries and tanks for hydraulic oil, de-icer fluid and water. Fuselage Design The fuselage near the wing is noticeably deep so that the hold is near the centre of gravity and big variations of trim are not caused by loading and unloading, which can be done through two large doors underneath the fuselage The liberal depth of fuselage at the wing also allows the aerodynamic layout to be mid-wing (or perhaps " low mid- wing"), while still keeping the wing spar low enough to prevent interference with passenger accommodation in the fuselage. The fuselage shape certainly appears to be both graceful and clean and it is said that the model tested by the Cali- fornian Institute of Technology gave the lowest drag coeffi- cient for fuselages tested in their tunnel. The actual fuselage should have good skin-friction properties as flush riveting and flush cross-stream skin joints have been used. The makers also say that a relatively thick skin has been used to eliminate wrinkling. (As wrinkling occurs at a stress much below ultimate failing stress, it is sometimes necessary to use a plating ot thickness greater than would be called for by ultimate failure requirements if excessive wrinkling under ordinary flying conditions is to be avoided.) Low drag has also been sought by completely enclosing the undercarriage and the retractable tailwheel with flush
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