Canards (blue) on the Saab Viggen

In aeronautics, canard (French for duck) is an airframe configuration of fixed-wing aircraft in which the horizontal stabilizer is ahead of the main wing, rather than behind them as in conventional aircraft empennage.^[1][2][3]

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.^[4]

[edit] Canard classes

Canard designs fall into two main classes: the lifting-canard and the control-canard.^[5]

Other classes include the close-coupled type and active vibration damping.

Canard (yellow) on a Mirage IIIS

Rutan Long-EZ, with lifting-canard ahead of the cockpit.

A deflected control-canard on an RAF Typhoon F2

[edit] Lifting-canard

The first airplane to fly, the Wright Flyer, was a lifting-canard. In this configuration, the weight of the aircraft is shared between the main wing and the canard wing. A lifting-canard generates an upload, in contrast to a conventional aft-tail which typically 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. ^[5]

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.^[5]

[edit] Control-canard

In the later 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 of canard configuration typically have a control-canard. In combat aircraft, the canard is usually driven by a computerized flight control system.^[5]

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.^[5]

Control canards have poor stealth characteristics, because they present large moving surfaces forward of the wing.^[6] The Eurofighter Typhoon uses software control of its canards in order to reduce its radar cross section.

[edit] Close-coupled canard

In the close-coupled canard, the foreplane is located just above and forward of the main wing. At high angles of attack the canard surface directs airflow downwards over the wing, reducing turbulence which results in reduced drag and increased lift.^[7]

The canard foreplane may be fixed as on the IAI Kfir, or have landing flaps as on the Saab Viggen, or it may be moveable and also act as a control-canard during normal flight as on the Dassault Rafale.

A moustache is a small, high aspect ratio foreplane of close-coupled configuration. The surface is typically retractable at high speed and is deployed only for low-speed flight. First seen on the Dassault Milan, and later on the Tupolev TU-144.

[edit] Active vibration damping

A large aircraft flying fast at low altitude can experience significant aerodynamic buffeting, leading to crew fatigue and reduced airframe life. Aircraft such as the B-1 Lancer incorporate small canard surfaces as part of an active vibration damping system that reduces these adverse effects.

[edit] Examples of canard aircraft

Some aircraft that have employed this configuration are listed below. A few types are listed twice, for example where the foreplane acts as a control-canard during normal flight and as a close-coupled type at high angles of attack.

[edit] Lifting-canard types

[edit] Control-canard types

[edit] Close-coupled canard types

[edit] Active vibration damping types

[edit] Gallery

The first powered airplane, the Wright Flyer, used dual, vertically-stacked canards	Eurofighter Typhoon of the Royal Air Force displaying at the Farnborough Airshow, 2006	Dassault Rafale, in service with the French Navy (Marine Nationale) and the French Air Force (Armée de l'Air)	Canards visible on a JAS 39 Gripen at the Farnborough Airshow
Grumman X-29, an experimental aircraft for forward swept wing research	The Rockwell-MBB X-31 Enhanced Fighter Maneuverability Demonstrator Aircraft	Canards (just behind the flight deck) on the XB-70 Valkyrie experimental bomber aircraft	Closeup of a Piaggio P180 Avanti's canards
The Beechcraft Starship Executive Transport	A Pterodactyl Ascender II+2 showing its canard control surface	Saab 37 Viggen of the Swedish Air Force	Miles Libellula (1941)

[edit] References

• Daniel P. Raymer (1989). Aircraft Design: A Conceptual Approach. American Institute of Aeronautics and Astronautics, Inc., Washington, DC. ISBN 0-930403-51-7. 
• R Wilkinson (2001). Aircraft Structures and Systems (2nd edition ed.). MechAero Publishing. 

[edit] Notes

[edit] See also

• Leading edge extension
• Stabilator
• Strake#Aircraft
• Tailplane
• Tandem wing

[edit] External links

Wikimedia Commons has media related to: Canard Aircraft

• Desktop Aero - A Summary of Canard Advantages and Disadvantages