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Canard (aeronautics)

By Wikipedia,
the free encyclopedia,

http://en.wikipedia.org/wiki/Canard_(aeronautics)

<-img src="http://upload.wikimedia.org/wikipedia/commons/thumb/6/60/SaabViggen_Canards.jpg/180px-SaabViggen_Canards.jpg"/>
Canards (blue) on the Saab Viggen

In aeronautics, canard (French for duck) is an airframe configuration of fixed-wing aircraft in which the tailplane is ahead of the main wing, rather than behind them as in conventional aircraft empennage.

The earliest airplanes, such as the Wright Flyer and the Santos-Dumont 14-bis, due to their tail-first configuration were seen by observers to resemble a flying duck — hence the name.

Classes of canards

The canard wing exists in two classes: the control-canard and the lifting-canard.

<-img src="http://upload.wikimedia.org/wikipedia/en/thumb/2/22/Mirage_III_MG_1490_canard.jpg/180px-Mirage_III_MG_1490_canard.jpg"/>
Control-canard (yellow) on a Mirage IIIS
<-img src="http://upload.wikimedia.org/wikipedia/commons/thumb/c/c7/Rutan.long-EZ.g-wily.arp.jpg/180px-Rutan.long-EZ.g-wily.arp.jpg"/>
Rutan Long-EZ, with lifting-canard ahead of the cockpit.
<-img src="http://upload.wikimedia.org/wikipedia/commons/thumb/1/11/Typhoon_f2_zj910_canard_arp.jpg/180px-Typhoon_f2_zj910_canard_arp.jpg"/>
A deflected control-canard on an RAF Typhoon F2

Control-canard

In the control-canard, most of the weight of the aircraft is carried by the main wing and the canard wing is used primarily for longitudinal control during maneuvering. A control-canard mostly operates at zero angle of attack. Combat aircraft that have the canard configuration typically have a control-canard. In combat aircraft, the canard is usually driven by a computerized flight control system.

One benefit obtainable from a control-canard is avoidance of pitch-up. An all-moving canard capable of a significant nose-down deflection will protect against pitch-up. As a result, the aspect ratio and wing-sweep of the main wing can be optimized without having to guard against pitchup.

Lifting-canard

In the lifting-canard, the weight of the aircraft is always shared between the main wing and the canard wing. A lifting-canard generates an upload, in contrast to a conventional aft-tail which mostly generates a download that must be counteracted by extra lift on the main wing. The lifting-canard configuration is therefore more efficient than a conventional aft-tail from the perspective of induced drag. The lift generated by the canard wing is significant, so in order to minimise induced drag on the canard, it is usually of higher aspect ratio and greater airfoil camber than a control-canard.

With a lifting-canard, the main wing must be located further aft of the center of gravity range than with a conventional aft tail, and this increases the pitching moment caused by trailing-edge flaps. Aircraft with lifting canards cannot readily be designed with sophisticated trailing-edge flaps.

Examples of canard aircraft

Aircraft that have employed this configuration include:

Gallery

See also

External links




Text from Wikipedia is available under the Creative Commons Attribution/Share-Alike License; additional terms may apply.


Published - July 2009














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