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Aviation History
1963
1963 - 0936.PDF
North American Aviation variable-geometry SST model PARIS REPORT . . . worded into the contract still to be signed (leading article and p. 900). An immediate response to the announcement of the order was President Kennedy's statement that the United States Government would go ahead and support a supersonic airliner programme if it would be economically feasible to offer fares attractive to a worthwhile section of the travelling public. The President also said that, following recent submissions by a number of manufacturers, another open design competition would shortly be arranged. Opinion in the United States seems to be unanimous on one point: that for stage lengths greater than 2,500 miles the most efficient supersonic airliner must be constructed of steel and/or titanium regardless of initial design cruising Mach number. On the question of wing variable geometry opinion is more open. Apart from pro viding a solution to the landing-speed problem, variable geometry is also attractive for improving subsonic cruising efficiency over shorter stages; for conforming to air traffic control procedures; and for avoiding sonic-boom disturbance. Although one or two American companies have considerable design and preliminary- test experience with variable geometry for military aircraft projects, alternative schemes with fairly conventional low-speed lift devices are being examined as an insurance against failure to solve some of the expensive and complicated problems that may arise. Two models typical of such alternative lines of thought appear on the North American stand. One aircraft has a sharply swept back wing with a high-aspect-ratio movable surface that lies along the top of the leading edge in cruising flight. Trim-changes appear to be compensated by a conventional but closely coupled tailplane. The four engines are mounted separately under the wing. Because the windows end at the leading edge the entire payload appears to be accommodated ahead of the wing: the rear fuselage could contain fuel in a long-range version or more passengers in short-range versions. The other North American model is based on a develop ment of the B-70 configuration, admittedly with variable geometry to the extent that the tips fold down in flight as on the B-70. Obviously, powerplant development will largely determine the choice of final configuration. It is frequently being proclaimed in Paris by American airframe and engine people that the economic success of an SST will depend ultimately on the powerplant, which must be optimized for efficiency at all stages of flight—much more so than is the case with the Olympus in the Concord. For instance it is suggested that the ideal powerplant would have a fairly large- ratio bypass for maximum thrust and minimum take-off noise. This would also give best efficiency during initial climb up to a certain altitude, where reheat in both flows would take the aircraft up to a greater altitude to minimize boom intensity on the ground during transonic acceleration. Cruising would then be performed with a small amount of bypass burning; and eventually, perhaps, with some means of transforming the engine into a ramjet during high-Marh cruise. Such an ambitious engine programme would be extremely costly in time and money and would largely control the pace of the whole programme. Undoubtedly amongst the most technically interesting projects for short and medium ranges are the Focke-Wulf FW260 Flamingo and FW300 VTOL airliners. Both projects employ a similar layout of the principal components, with four or six lift engines, two cruise engines with tilting nozzles, and the main landing gear all put in a nacelle midway along each wing. The 99,2001b gross-weight FW260 is designed to carry 98 tourist-class passengers for 920 n.m., cruising at 496kt with vertical take-offs and landings from airfields up to 2,000ft altitude and at standard temperature, whereas the -4,0001b FW300 is designed to carry 58 passengers for 200 n.m., cruising at 456kt. Although engineers in the United Kingdom and America have I North American Aviation canard SST model derived from the B-70 Artist's impression ofSIAT 311A studied airline possibilities of jet lift, this is the first time that any company has released actual details of projects. The manufacturer of the engines used in the studies is not disclosed, except that both Bristol Siddeley and Rolls-Royce are involved, but the FW260 has four propulsion units of 9,1501b thrust each and 12 lift units of 8,0001b thrust each, while the FW300 has four propulsion units of 4,5001b thrust each and eight lift units of 4,8501b thrust each. Control in all axes is effected entirely by differential thrust and tilting of the lift-jet nozzles. Focke-Wulf recognize that these aircraft would be too noisy for city-centre operations, but they feel thai the economics of the aircraft show sufficient promise to make the designs interesting. The Focke-Wulf VTOL scheme is one of three different basic approaches to the problem being examined in Germany with civil applications in mind. Eventually, one or two of the schemes may be chosen for West German Government financial assistance. The other schemes are the Bolkow/Derschmidt rotor (described in the helicopter section of this report) and the tilting-propeller scheme by Weser Flugzeugbau. One of these latter projects, the WFG-P23, carries 12 passengers and weighs 14,0001b. The Lycoming T55s rotate at the wing-tips, but in another tilt-propeller pure-research project, the WFG-P16, powered by two Bristol Siddeley Gnome 1200s, the engines are mounted in the fuselage. Whilst West Germany weighs up the prospects of getting into the larger medium- and short-range civil market in several years' time, competition between manufacturers of conventional turbofan aircraft is becoming very intense. Hawker Siddeley and Boeing are being left alone to fight over whatever remains of the market Model of Bblkow-SIAT 6S 210
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