page_title: Canard (aeronautics)
section_title: Stability
hierarchical_section_title: Canard (aeronautics) / Basic design principles / Stability
caption_attribution_description: English: Sukhoi Su-33 77 RED at Kubinka Air Base
context_page_description: A canard is an aeronautical arrangement wherein a small forewing or foreplane is placed forward of the main wing of a fixed-wing aircraft. The term "canard" may be used to describe the aircraft itself, the wing configuration, or the foreplane.
  The term "canard" arose from the appearance of the Santos-Dumont 14-bis of 1906, which was said to be reminiscent of a duck with its neck stretched out in flight.
  Despite the use of a canard surface on the first powered aeroplane, the Wright Flyer of 1903, canard designs were not built in quantity until the appearance of the Saab Viggen jet fighter in 1967. The aerodynamics of the canard configuration are complex and require careful analysis.
  Rather than use the conventional tailplane configuration found on most aircraft, an aircraft designer may adopt the canard configuration to reduce the main wing loading, to better control the main wing airflow, or to increase the aircraft's maneuverability, especially at high angles of attack or during a stall. Canard foreplanes, whether used in a canard or three-surface configuration, have important consequences on the aircraft's longitudinal equilibrium, static and dynamic stability characteristics.
context_section_description: A canard foreplane may be used as a horizontal stabiliser, whether stability is achieved statically or artificially (fly-by-wire).
  Being placed ahead of the center of gravity, a canard foreplane acts directly to reduce longitudinal static stability (stability in pitch). The first airplane to achieve controlled, powered flight, the Wright Flyer, was conceived as a control-canard but in effect was also an unstable lifting canard. At that time the Wright brothers did not understand the basics of pitch stability of the canard configuration, and were in any event more concerned with controllability.
  Nevertheless, a canard stabiliser may be added to an otherwise unstable design to obtain overall static pitch stability. To achieve this stability, the change in canard lift coefficient with angle of attack (lift coefficient slope) should be less than that for the main plane. A number of factors affect this characteristic.
  For most airfoils, lift slope decreases at high lift coefficients. Therefore, the most common way in which pitch stability can be achieved is to increase the lift coefficient (so the wing loading) of the canard. This tends to increase the lift-induced drag of the foreplane, which may be given a high aspect ratio in order to limit drag. Such a canard airfoil has a greater airfoil camber than the wing.
  Another possibility is to decrease the aspect ratio of the canard, with again more lift-induced drag and possibly a higher stall angle than the wing.
  A design approach used by Burt Rutan is a high aspect ratio canard with higher lift coefficient (the wing loading of the canard is between 1.6 and 2 times the wing one) and a canard airfoil whose lift coefficient slope is non-linear (nearly flat) between 14° and 24°.
  Another stabilisation parameter is the power effect. In case of canard pusher propeller: "the power-induced flow clean up of the wing trailing edge"  increases the wing lift coefficient slope (see above). Conversely, a propeller located ahead of the canard (increasing the lift slope of the canard) has a strong destabilising effect.
caption: Su-33s with canard
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