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Aviation History
1943
1943 - 0497.PDF
FEBRUARY 25-ra, 1943 FLIGHT 199 ciency were supplied by the aerodynamics engineers ; and structural and other groups, of the aircraft company pro- vided various important new ideas. Combination of all the advanced features produced a craft of 8,000 h.p., provided by four eighteen-cylinder Wright Cyclone engines having a piston displacement of 3.35° CUt m an<l a power/weight ratio of 1.1 1b./h.p. According to statements made, the Constellation has a range of approximately 4,000 miles, can carry 55 seated passengers and a crew of nine in an air-conditioned, pres- surised cabin over the 3,000 miles from Southern California to New York in less than 9 hours, and from the Pacific Coast to Honolulu in 12 hours. It is claimed to have approximately 100 miles per hour higher cruising speed at about half-power than present standard air transports or cargo planes, and the maximum speed is now expressed as "exceeding that of any four-engined bomber or the Japanese Zero." One Mile per Gallon It is said that the Constellation,will cruise continuously on a fuel consumption oi 1 U.S. gal. per air mile. The high power for take-off with heavy load, the low engine weight and low fuel consumption are factors contributing to the long range. On three engines, flight can be main- tained at 25,000ft., and on only two at 16,500ft. Other highly important factors that make possible the speed, range, economy and a ceiling of 35,000ft. are the aerodynamic design of fuselage, wings and engine nacelles; exterior spot-welding on 75 per cent, of the fuselage and 10 per cent, of the wings; retractable manoeuvring flaps which telescope into the wings; and a tail having three vertical fins. The fuselage was built to a design chosen as the best of eleven shapes developed and tested. It has a perfectly circular cross section throughout, which is best for a pres- surised cabin, but to provide optimum floor width (especi- ally in the nose and tail) for comfortable accommodation of the largest number of passengers, the fuselage is cam- bered from the longitudinal axis fore and aft. This gives the forward end a shape somewhat resembling an aerofoil section which only moderately affects the lift distribution over the wing. An incidental advantage of the cambering is that a relatively short strut can be used for the nose wheel of the tricycle undercarriage, with a resultant saving of a considerable amount of weight. Objectives attained by design of the triple-fin tail are: Moderate height of the craft on the ground; increased effectiveness of the elevator; and maximum control and safety of the plane in case of engine failure. Height of the Constellation on the ground is only 18ft. 8in., as against the 20ft. gin. height of the 307-B, and 27ft. ioin. of the DC-4. This relatively low height is more readily accom- modated under doorways and roof beams of hangars. The tendency of air to spill off the ends of a horizontal tail surface is prevented by the outboard vertical fins, so that the air is controlled and made to do the work required of it when the elevator is deflected. In the event of engine stoppage during take-off or flight, this tail arrangement gives the pilot optimum control of the machine in relation to the effort he exerts. Wing* design was developed from tests of the Lockheed Lightning P-38 wing, which the company believes to be the best compromise between a low-drag wing and a high-lift wing, and which has particularly good stall characteristics. Several wing types were tested in the wind tunnel, in- cluding laminar-flow sections wb.ich create little eddy- making at the trailing edge. These were found to have good gray characteristics but to be sensitive to auy wing roughness that might be caused by ice formation, de-icers or walking on the wing skin, and therefore were not con- sidered well suited for a passenger transport aircraft. Moreover, the value of a wing section cannot be judged from its own characteristics alone, but must be ascertained in conjunction with the effect of operation of wing flaps, as high-lift devices to give low landing speed are a basic requirement in the design of the craft, rfnd their effect on wing-section characteristics is of major importance. The wing form chosen after tests and consideration of all the factors involved is an N.A.C.A. (National Advisory Committee for Aeronautics) section having no aerodynamic, twist, and is, in effect, an enlargement of the wing of the Lightning. " A novel feature of the wings is incorporation ot manoeuvring flaps which telescope into the wings and, together with the time-proved Lockheed Fowler flaps for The Constellation approaches to land. Double main wheels and dual wheel brakes are a feature. The fuselage shape isreminiscent of certain early wing sections with reflexed trailing edge, designed to give small travel of the centre of pressure.
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