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Aviation History
1961
1961 - 1743.PDF
In a supersonic airliner not only the powerplants need variable geometry. These photographs reveal the proposed forward fuselage of the Douglas SST, showing how the upper section ahead of the flight deck folds down to provide forward visibility for take-off and landing 849 FLIGHT 30 Novel 1961 AFTER THE DC-8 Further Details of the Douglas 2229 DOUGLAS were the originators of the idea of speed-plateauxin air transport. After helping to establish plateaux atabout 180, 300 and 550 m.p.h., the company have set their sights on 2,000 m.p.h. No major US aircraft company has publiclydisagreed with the belief that the cruising Mach number of the next generation of airliners should be not less than three, and DouglasAircraft have subscribed to this belief for some two years. Although the company could not themselves finance the designand manufacture of such an aircraft, they have conducted extensive research into a transatlantic M3 design with the company numberof Model 2229. It is not unknown for a company to publish illus- trations of "supersonic airliners" which have never been the subjectof serious research, either in order to impress the gullible public or to mislead competitors. But the Douglas 2229 is a serious project,and it is possible on this page to comment upon details revealed in As might be expected, the intakes are two-dimensional, and in theexhibited models the propelling nozzles were likewise. In the present state of the art the development of an infinitely variable two-dimen-sional intake and exhaust system is merely very difficult, whereas an infinitely variable circular arrangement of reasonable weight andsimplicity is practically impossible. So great is the root chord of the wing that, together with thedelta foreplanes, it covers the whole usable fuselage and must P3se problems in passenger embarkation and emergency escape.The cross-section is conventional, although Douglas have investiga- ted twin pressurized tubes side-by-side. The flight deck in a 2,000m.p.h. aeroplane poses many problems which can be solved in various ways. Douglas have located it well back from the nose inorder to achieve satisfactory width and depth. This also places the side windows almost parallel to the line of flight, resulting in relativelymild kinetic heating. The front windows are faired off in flight, as illustrated above. Douglas would certainly like to build such an aeroplane; but sowould all the other West Coast giants, and there is probably going to be room for only one such design. This means that the US in-dustry will have to suffer all the pains of realignments and consor- tiums which have increasingly become the lot of the Europeanmanufacturer. Time will show whether the renowned DC family has already come to an end. This model of the Douglas 2229 por- trays the cruise configuration, with the wing - tips turned downwards model form at the recent meeting in Los Angeles of the ExperimentalTest Pilots' Association. Gross weight of the 2229 would be some 400,0001b; the fuselagewould be 200ft long, and with the wing-tips fully spread the span would be about 100ft. As might be expected, the Eggers' momen-tum theory of compression lift is utilized. In the B-70 bomber it is possible to dispense with a fuselage above the wing, and thusemploy the ideal wing/half-body combination. This cannot be done in a transport, where the pressurized passenger cabin mustextend as far fore and aft as possible, but the 2229 has every other feature aimed at raising the cruising lift/drag ratio. At full speedthe outermost 20ft of each wing is folded downwards in order to increase the favourable pressure-distribution beneath the wingcreated by the leading-edge shock and the supersonic compression alongside the widening propulsion box. Details of the latter are shown in the two lower photographs.The four engines are turbojets, each with a mass-flow of some 4501b/sec and possibly mild augmentation in the tailpipe. They aremounted at the rear of an inlet-duct box extending forwards to the leading edge of the wing on each side of the aircraft, the distancefrom the knife-edges A to the propelling nozzles H being some 80ft. In order to achieve maximum efficiency under all flight conditions, a supersonic airliner must have a complicated propulsion system, with infinitely variable intake, duct and exhaust profiles. These photographs llustrate the broad configuration suggested by Douglas: A, shock "edges; 8, intake doors (shown closed for ditching); C, three-section, 'ariable-profile duct wall; D, retracted main bogie; E, duct splitter; F, engine intakes; G, engines; H, rectangular variable nozzle
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