Concorde Wing Design
The wing is the most important lift-producing element of an aircraft. Wing designs vary, depending on the aircraft type and purpose. It is well known that the airframe configuration requirements for efficient supersonic flight are not compatible with the airframe configuration requirements for efficient slow speed flight, take-off and climb, or descent and landing. For low speed flight, and conventional take-off and landing, the optimum wing planform is generally considered to be a long span, narrow chord wing having little, if any, sweep angle. For transonic and supersonic flight however, highly swept wings are considered preferrable because aerodynamic drag may be greatly reduced thereby, and other advantages are also obtained.
One of the main drawbacks of the SST design is that it must be optimized for high-speed flight in order to reach supersonic speeds. It has been discovered that the best shape for optimum cruise at Mach 2 is a slender straight edged delta twice as long as its span. SST designs are based on modifications of the delta wing (a point-forward triangle). The reason for this choice is that the modified delta wing (and other highly swept forms) has been shown theoretically to have lower supersonic drag due to lift, than a wing planform with relatively low sweep, and also lower wave drag due to thickness. In consequence, the delta wing can be thicker, thus reducing structural weight and providing more volume for fuel and equipment.
The delta wing family also has recognized disadvantages; and because it has been the sole candidate for SSTs, these disadvantages are widely assumed to be unavoidable for all SSTs. Two of these disadvantages are the delta wing's high drag due to lift at subsonic speed, and low maximum lift, even at an uncomfortably high angle of attack. These traits lead to the need for high power and high speed during takeoff and landing, resulting in high noise levels and requiring long runways. The main obstacle to widespread acceptance of the supersonic transport is its relatively poor range and fuel efficiency, resulting in uncompetitive economics. The basic cause of this uncompetitive performance is the low lift to drag ratio (L/D) of presently used and proposed SSTs, at both supersonic and subsonic speeds.
The "ogival" wing form used on the Concorde is an attempt to modify the optimum delta for greater efficiency at low speeds, particularly at take-off and landing. Despite this, the Concorde shows very high fuel consumption and low lift at low altitude and speed, and requires a very long take-off roll. Similarly, the very "slippery" shape requires a very long landing roll due to high landing speeds and low drag. The prototype Concorde even used a parachute to aid the brakes in landing, and such devices are common in military aircraft.
The wing is a continuous camber structure with multispar torsion box, manufactured mainly from RR.58 (AU2GN) aluminium alloy. Integrally machined components used for highly loaded members and skin panels. In center wing, spars are continuous across fuselage, the spars and associated frames being built as single assemblies extending between the engine nacelles.
For achievement of improved supersonic cruise efficiency, a preferred supersonic aircraft configuration employs highly swept (subsonic) leading edge wings. However, this design creates particular problems relative to high lift conditions typical of climb-out and approach where high angles of attack are required. More particularly, these highly swept wings develop two leading edge vortices which, while increasing lift, also result in an increase in drag, resulting in a poor lift to drag (L/D) ratio. Higher (L/D) ratio is obtained when there is fully attached flow over the wings. In the Concorde supersonic transport, the wing has a highly swept leading edge, but no leading edge devices are used. During takeoff and climb, the configuration operates at a high angle of attack, and the two strong vortices that are generated off of the leading edges create sufficient lift for takeoff and climb. However, because of the high drag, the engines were operated at a relatively high power setting, thus creating noise well above the maximum level permitted in the vicinity of most all airports. Consequently, there are very few airports at which the Concorde could operate.
In order to gain lift for takeoff, the wing must be raised to a higher angle of attack (angle of the wing relative to the airflow over the wing) than it has on the runway. This is known to pilots as "rotation", when the nose is raised to increase lift for takeoff. In order to rotate the aircraft in the normal aircraft design, the elevators are angled trailing-edge-upward to exert a downward force at the rear of the fuselage. This raises the nose, but at the cost of a downward force on the aircraft just when the aircraft most needs all the lift it can muster.
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