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Aviation History
1969
1969 - 0414.PDF
Flight International • CONCORDE Three-view general arrangement of the production Concorde. The most obvious external differences between this aircraft and the prototypes include the front visor which now has provision for forward vision; the longer aft fuselage; the modified outer wing shape; and the different entry door locations CONCORDE AERODYNAMICS AND GEOMETRY The best shape for optimum cruise performance at Mach 2 is a straight-edged slender delta twice as long as its span, with slenderness (or fineness ratio) increasing with speed. Modifi cations have to be made to this shape to obtain from it the optimum qualities at low speeds, particularly on the approach and landing. One of the bonuses of the delta wing is the vortex sheet which attaches itself at low speeds and high angles of attack. It increases lift, it is claimed, by about 30 per cent and by as much as 60 per cent in the ground cushion on landing. By rounding the wing tips and extending the root fillets (thus producing the "gothic" plan-form) this vortex sheet can be made to stay attached up to and beyond the stall. One of the reasons why a foreplane is not fitted to trim out the supersonic shift of the aerodynamic centre is because at slow speeds and high angles of attack it would disturb the valuable leading-edge vortex sheet and lead to directional instability (supersonic trimming, as we shall see, is performed by the longitudinal transfer of fuel). So we end up with a shape which is the optimum for both low and high speed worlds—a shape which has no slats or flaps or any moving parts except the elevons (three per side). It also makes an ideal fuel tank, and a perfect mounting for the very long engines and their associated intakes and nozzles—each power- plant being as big as a bus. Judged on the ultimate aerodynamic criterion, lift/drag or L/D ratio, the Concorde produces a figure of between 7 and 8 in supersonic flight, and between 12 and 13 in subsonic flight—or not much less than the L/D of current subsonic jet transports. This very good efficiency in the subsonic regime means that the Concorde's fuel consumption, or air miles per gallon of fuel, will be about the same subsonic as at high supersonic speed. This gives scope for hope that economics will not be too impaired when operators have to schedule flights, as they will over boom-sensitive areas, at subsonic speed. There are, of course, the inevitable disadvantages, otherwise all aircraft would have this shape of wing. Control is the major one, particularly on the approach and landing. High angles of attack are nee.ded to get landing lift and hence landing speed to levels that are acceptable to pilots; and the very low moment of inertia in roll, and high pitch and yaw inertias, make the crosswind-landing case more critical. The angle of attack on the glidescope will be 10° compared with 1 ° on a subsonic jet. and automatic throttles will play an
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