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Aviation History
1952
1952 - 3414.PDF
FLIGHT, 28 November 1952 The 80-seater HD-45 project, with outboard turbojets and wing-mounted fuel tanks. M. Hurel, designer of the "HD" series of aircraft. HUREL DUBOIS TRANSPORTS Progress with the HD-31 and 32: The HD-45 Jet Project CONSIDERABLE attention has been given in French aviation circles to the projects put forward for the Government's contest for medium-range transport air craft, sponsored by the Secretariat General del'Aviation Civile et Commerciale, and for which well over 500,000,000 francs have been allocated. The main nationalized concerns and three private companies—Breguet, Dassault and Hurel Dubois— have submitted very unusual and advanced designs with various combinations of turboprops, and axial-flow, "double- flow" and auxiliary turbojets. These are intended to meet the requirements of the Mediterranean and European services of Air France, and of such independent lines as Union Aero- maritime de Transport, Compagnie des Transports Aeriens Intercontinentaux and Societe Aigle Azur, operating in the French Union. One of the designs which aroused most interest was die HD-45, proposed by Avions Hurel Dubois S.A., and incorporating their now well-known combination of high-aspect-ratio wing and lift struts. Initially considered were two layouts, HD-40 and 41, incorporating swept wings and having twin axial-flow turbojets and four "double-flow" units respectively, but these were superseded by the 70/80-seater HD-45, with two 9.260 lb thrust axials mounted in die lift struts. The HD-45 design found favour with the authorities, though it is understood that an order for a proto type will not be given until flight tests have been carried out with the piston-engined HD-31 now under construction. The prototype HD-31 under construction at the Hurel Dubois works at Meudon-Villacouhlay earlier this year. In the foreground is the HD-fO. It may be recalled that after the war M. Hurel, the designer of the HD-45, undertook lengthy research into the advantages of the high-aspect-ratio wing which, he claimed, would reduce induced drag. 6y the use of lift-struts increased aspect ratio could be obtained without the penalty of greater airframe weight. Thus, machines built on this principle, he argued, could have a per formance comparable with conventional types having a much smaller payload. His ideas were first put to the test on the little single-seater HD-10, with a span of 39ft 4in, and an aspect ratio of 32.5. This was built at the P. Levasseur factory and its trials were so successful that the French Government ordered two prototypes of a 36-passenger/freighter, the HD-31, powered by two Wright R-1300-C7-BA1 engines of 800 h.p. and having a wing of 20.2 aspect ratio. Having taken over a derelict and dilapidated hangar at Meudon-Villacoublay, Hurel Dubois converted it, in a space of months, into a light and airy factory where work was immediately put in hand on the HD-31. The machine now has its undercarriage fitted, the outer wing sections are complete, and a first flight appears possible before the year's end. A higher powered prototype—the HD-32—with 1,200 h.p. Pratt and Whitney R-1830-92 Twin Wasps is also the subject of a Government order. It is learned that the second HD-31, now taking shape at Meudon-Villacoublay, is also to have Twin Wasps and will therefore be up to HD-32 standard. Forty-two passengers, or 11,025 lb °f payload, will be carried by the HD-32 over stages of 620 miles, using Class "C" airfields, and it is claimed that operating costs will be about 30 per cent lower than for comparable aircraft. The engine installation is almost identical with—in fact, interchangeable with—that of the Consolidated Catalina. Latest figures for the HD-32 are 5— Span, 147.6ft; length, 72.5ft; height, 22.6ft; wing area, 1,076.4 sq ft; passenger cabin length, 32.8ft; gross weight (passengers), 36,382 lb, (freight), 38,257 lb; maximum speed at sea level, 186 m.p.h.; economical cruising at sea level, 155 m.p.h.; economical cruising at 9,800ft, 167 m.p.h.; minimum speed, 66 m.p.h.; take-off speed, 81 m.p.h.; distance to clear 50ft, 656 yd (with one engine inoperative, 1,230 yd); landing distance over 50ft, 410 yd; service ceiling, 16,400ft; maximum range with 8,820 lb freight, 1,240 miles, with 6,615 lb fuel and oil. Later versions of the HD-32 have been investigated, with four Armstrong Siddeley ASM3 turboprops or two Double Mambas. Advanced project work is now going forward with the HD-45 twin-jet design capable of transporting 80 passengers at 452 m.p.h. for more than 1,550 miles. Many changes from the riD-31 are apparent in the drawings of the new type. The fuselage is more streamlined, the twin fins have been replaced by a single unit, and the undercarriage has been made retractable. Wing area has been increased, and the aspect ratio reduced to 18.4. Span is the same as for the HD-32 (147.6ft), but the length has been increased to 98.4ft and the height to 26.2ft. The fuselage, cylindrical in shape, has a diameter of 10.9ft. The power units will probably be either late-mark Avons such as the RA.i6s to be fitted on the Comet 3, or a development of the SNECMA Atar 101. They will be underslung at the outer ends of the horizontal portion of the lift struts. The four-wheel main undercarriage units will have a track of 15.7ft and retract inwards
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