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Aviation History
1955
1955 - 1003.PDF
22 July 1955 115 The P2V-7 for the U.S. Navy has Westinghouse J34 booster turbojets and a dorsal turret; neither feature is found on the otherwise similar machines being made for Canada. A recent air-to-air view of the U.S. Navy T2V-1 trainer (below) show- ing the arrester hook. "Super- circulation," by means of flap- blowing, is to be fitted to all T2Vs. Lady of the Skies," the Constellation. The power and maximumweight of the present aircraft are now about twice the design values for the first machine. All production now is of the SuperConstellation, the total output of between ten and eleven air- craft per month being divided between civil transports, militarytransports and "radar Constellations" which are being found very valuable by both the Air Force and Navy.The major design effort is at present concentrated upon the Model 1649, which has already been ordered in some numbersby T.W.A. and Air France. This machine was evolved as a result of a comprehensive analysis of the whole long-range trans-port picture, during which complete redesign of the present 1049 series was examined. It was found that most of what Lockheedwere seeking could be obtained by developing a revised wing and tail, and that the resulting aircraft could be got intoproduction for about half the development cost of a wholly new machine. The 1649 will be powered by the EA-3 version of theWright Turbo-Compound engine, and Lockheed calculate that its economics will beat those of the DC-7C on all the longestprojected airline stages. Although a considerable amount of valuable experience isbeing gained with four military Super Constellations powered by the 5,500 h.p. Pratt and Whitney T34 turboprop, civil ait-craft powered with this engine are not now projected. One such machine, designated L.I449, would have flown within ten knots ofthe "never exceed" speed on the level. The new wing of the Model 1649 has raised the critical Mach number, making thebasic airframe more attractive for eventual conversion to turbo- prop power. In passing, it may be noted that the T34-poweredaircraft have regularly been flying at speeds of the order of 450 m.p.h. As might be expected, the great 156ft span of the L.1649 wing confers an outstanding high-altitude performance and it seemslogical that machines of this type should be developed for use as radar pickets, capable of doing a better job than the presentWV-2 and RC-121D. While at Burbank, we saw early stages in the manufacture of 1649 wings in which the integral-machinedskin concept has been carried one stage forward. Both upper and lower surfaces from root to tip between the spars are now beingmachined from single slabs of light alloy, with a corresponding reduction in numbers of parts, cost and weight. We alsoexamined the L.I649A mock-up, from which the outstanding impression remains of great span, unusually acute dihedral andgenerous clearance between the inner airscrews and the fuselage. There remains to be considered the Lockheed Electra, one ofthe most important, and most discussed, aircraft in the whole transport picture. As is now well known, the existence of thedesign was made public early in June, when an American Airlines order for 35 Electras was also announced. Northwest Airlines,and other operators, are reported to be in the process of working out contracts.Broadly speaking, the Model 88, as the Electra series is known to its designers, is a replacement for the Convairs and—-on manyroutes—for four-engined Douglases. It is, in fact, what Hall L. Hibberd (Lockheed vice-president, engineering) had in mind manymonths ago when he spoke of "a shiny new Viscount," although the two machines are so dissimilar in characteristics, timing and pricethat the Lockheed should not have much effect on Viscount sales. The chief fly in the ointment in the development of theElectra is its powerplant group, and it may be as well to examine diis first. Most published information on the aircraft has shownthe engine as the Allison 501, or a later version of the same family. This is a single-shaft turboprop, basically similar to the militaryT56 (about 3,750 design e.h.p.) but with certain features incor- porated to make it more suitable for airline use. One of the chief disadvantages of the T56 from a civil view-point is that, owing to its high pressure-ratio (design figure, 9:1) the compressor characteristics are not suitable for running atless than about 90 per cent of maximum r.p.m. Actual figures are at present about 13,820 max. and 12,000 min. r.p.m., andwork is in hand to reduce the latter to less than 10,000. Having heard a Convair YC-131C test-bed (T56) idling on the ground wecan state that the high tip-speed results in noise which would not be welcomed by civil operators. Engine-handling, also, is notyet anywhere near as good as that of the free-turbine Proteus or single-shaft Eland.Knowing these things, Lockheed have refrained from making any definite statement upon their power units (for publication, atleast). Allison are known to be doing a wholly new, split-com- pressor engine, Napier will have an excellent engine in the4,000 h.p. Eland and Rolls-Royce are expected to produce an unbeatable engine in the RB.109. All of these could fit theElectra without too much trouble. At present, the Allison 500 series is shown in all the publicitymaterial, and we have had a sketch prepared showing how it will fit into the Electra nacelle. Unlike that of most Allison turbo-props the reduction gear will lie below the engine axis, so that the main flow of air will come in above the spinner, and pass outcleanly above the wing. On the C-130 (in which a basically similar engine is fitted the other way up) the nacelles are under-slung, and a deflector on each jet nozzle and titanium skin on the flaps in line with the effluxes has been necessitated. The Electrawill have very large, double-slotted flaps continuous beneath the engines. Aerodynamically-boosted controls are specified.Specified airscrews are paddle-blade reversing units (four blades) with a diameter of no more than 13ft 6in. As the clearancebetween the inner tips and the fuselage will, nevertheless, be but two feet, it seems that the Lockheed designers are finding them-selves somewhat cramped in a span-wise direction. It was also consideration of airscrew/ground clearance which caused Lock-heed to discard the well-engineered C-130 underslung engine installation.The Electra wing will have a span of 95ft and an area of 1,200 sq ft (gross). As the maximum weight is at present fixed at 98,500lb, the wing loading can be calculated as 82.2 lb/sq ft—a high figure for a machine not intended for operation on stages above
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