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Aviation History
1954
1954 - 1209.PDF
FLIGHT, 30 April 1954 539 The YT56 is at present giving about 3,500 s.h.p., and looks hardly bigger than a cowled six-in-line engine of 350 h.p. The cowling is not vertical, but is tilted to remain at right angles to the dihedral-line of the wing. The aircraft, "Old 1961," is flying with three types of engine. T56 TEST-BED The Allison Engine for the C-130 Fitted to a Super Constellation IT is well known that Lockheed are developing the basic Model 1049 Super Constellation into the Super Con stellation 1249 and 1249B with turboprop power. These aircraft will have a slightly reduced wing span of 117ft, large tip tanks and a wing loading of 92 lb/sq ft or more. The power unit will be the Pratt and Whitney T34 which, as we said in our Power Units Number on April 9th, "can be considered the only fully developed engine in its class in the world"; it is a 5,700 h.p. turboprop, of single-shaft layout and driving a single three-blade airscrew, with immense blades of over 24in chord. Production of the civil 1249 will probably be preceded by the R7V-2 transport for the U.S. Navy, for which orders have already been placed. All these turboprop Super-Connies will cruise at something better than 400 m.p.h., if Lockheed estimates prove correct. The aircraft illustrated on this page is not a Model 1249, but is the renowned "Old 1961," the first Constellation ever built (back in 1942) and since modified to incorporate every successive Constellation modification. When it was "stretched" to the 113ft length of a Super Constellation it became known as the 1961-S, and has since been termed "The Beast" owing to the fact that it sprouted all the tip-tankage and array of radomes to be found on high-flying barrier- radar WV-2s of the U.S. Navy (these have now been removed). At present, its power units consist of one 3,250 h.p. Wright This simple sketch gives an indication of the layout of the 756 as it will be installed in the C-130. The duct at the bottom is probably for an oil cooler. Turbo Compound 972 TC (port outer), two 2,500 h.p. Pratt and Whitney R-2800 Double Wasps (both inners) and—the engine shown here—one Allison T56 turboprop in the star board outer position. It may be remarked that Super Con stellations now being built have four Turbo Compounds. The T56 is not seen as a standard power unit for the Constellation, but is scheduled for service with the Lockheed C-130, the new assault transport of the U.S.A.F. This machine is a 400 m.p.h. high-wing design with a large door under the upswept rear fuselage. The undercarriage retracts, Me323-fashion, into the belly. Fully pressurized, the C-130 will have four T56s and should be "quite an airplane"; the prototype should fly next month and production is under way at the company's factory at Marietta, Georgia, where B-47s are also built. Of the T56, little definite has been published beyond the fact that it is a turboprop developed from earlier Allison designs and that it has a design power of 3,750 s.h.p. The following can, however, be deduced with fair accuracy. It will be a single-shaft engine, with a compression ratio of about 7:1 and a specific fuel consumption of about 0.6 lb/hr/ehp at take off, falling to less than 0.5 at the best high-altitude cruise point. It is, in particular, certain to be very small and compact in relation to its power. One of the first flight-cleared YT56 engines has now been installed in Super Constellation "1961-S" approximating, as nearly as possible, to the installation of the production engine in the C-130. The C-130 control system has been employed, and this is probably an electronic arrangement by Aero- products. As the photographs show, the installation is quite remarkable for its neatness and small frontal area; the engine is rendered accessible by the large side doors, hinged at the top, with the general layout as shown in our sketch. Acces sories are disposed on the rear sides of the engine while the airscrew is driven through the large separate reduction gear, as was the case in the installation of the earlier Allison T38 turboprop in the Convair Turbo-Liner. The airscrew is a Curtiss Turbolectric unit, with three forged and extruded hollow-steel blades, each some 18in in chord. Full thermal anti-icing is provided both on the air screw and engine. One point of particular interest is the fact that—in common with many other American aircraft—the starter motor is a small compressed-air turbine geared down to the main engine. Once one turboprop has been started it is probable that its compressor can be tapped to provide air for the starters of the other three engines (in the C-130A, that is). At present, a Continental-Turbomeca Palouste MA-1 air compressor set is used as a ground trolley to supply air for starting. Part of its delivery pipe can be seen in one photo graph, attached to the underside of the wing. D
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