Canard (aeronautics)

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In aeronautics, canard (French for duck) is an airframe configuration of fixed-wing aircraft in which the tailplane is ahead of the main lifting surfaces, rather than behind them as in conventional aircraft, or when there is an additional small set of wings in front of the main lifting surface. The earliest models, such as the Wright Flyer, the world's first airplane, and the Santos-Dumont 14-bis, were seen by observers to resemble a flying duck — hence the name.^{[citation needed]}

The term "canard" has also come to mean any horizontal airfoil mounted in front of the main wing, whether moving or not.^{[citation needed]}

Contents 1 Canard aircraft characteristics 1.1 Advantages 1.2 Disadvantages 2 Examples of canard aircraft 3 Gallery 4 References 5 See also

[edit] Canard aircraft characteristics

Canard foreplanes act in a similar way to conventional tailplane and elevators, but due to swap in position about the centre of gravity control surface actions have the opposite effect.^{[citation needed]}

[edit] Advantages

• A canard arrangement produces more lift than a conventional set-up when total lift produced is considered. During manoeuvres the canard control surfaces mirror those of the main wing, adding to the lift to climb and decreasing the lift to descend. This means that the aircraft can move tighter and faster than with a conventional set-up.^{[citation needed]}

• Because the canard generates upward lift, unlike with a tail plane which produces downward or negative lift, there is a reduction in the lift required from the main wing to overcome the weight of the aircraft. This results in a reduction in lift-induced drag. Hence, the overall drag and lift requirements of the aircraft are reduced.^{[citation needed]}

• The canard is sometimes designed to stall prior to the main wing. This means that once the canard stalls, the nose tends to pitch down, thus reducing the angle of attack of the main wing and reducing the likelihood of that stalling. However, that is not to say that the main wing cannot stall: a vertical gust that causes a sufficiently high angle of attack on the main wing will cause both the canard and the main wing to stall.^{[citation needed]}

• In a propeller aircraft, a canard normally uses a pusher configuration. This reduces fuselage drag, because the fuselage is not operating in the increased flow induced by the propeller.^{[citation needed]}

[edit] Disadvantages

• The wing root operates in the downwash from the canard surface, which reduces its efficiency, although the effect of the downwash does not cause as large of a problem as the tailplane would experience in a conventional set-up.^{[citation needed]}

• The wing tips operate in the upwash from the canard surface, which increases the angle of attack on the tips and promotes premature separation of the air flowing over the wing tip. This premature separation at one tip or the other would promote wing-drop at the approach to the stall, leading to a spin. This must be avoided by precautions in the design of the wing, and may require extra weight in the wing structure outboard of the wing root.^{[citation needed]}

• Because the canard must be designed to stall before the main wing, the main wing never stalls and so never achieves its maximum lift coefficient. This may require a larger wing to provide extra wing area in order for the airplane to achieve the desired takeoff and landing distance performance.^{[citation needed]}

• It is often difficult to apply flaps to the wing in a canard design. Deploying flaps causes a large nose-down pitching moment, but in a conventional aeroplane this effect is considerably reduced by the increased downwash on the tailplane which produces a restoring nose-up pitching moment. With a canard design, there is no tailplane to alleviate this effect. The Beechcraft Starship attempted to overcome this problem with a swing-wing canard surface which swept forwards to counteract the effect of deploying flaps, but usually, many canard designs have no flaps at all.^{[citation needed]}

• In order to achieve longitudinal stability, most canard designs feature a small canard surface operating at a high lift coefficient (C_L), while the main wing, although much larger, operates at a much smaller C_L and never achieves its full lift potential. Because the maximum lift potential of the wing is typically unavailable, and flaps are absent or difficult to use, takeoff and landing distances and speeds are often higher than for similar conventional aircraft.^{[citation needed]}

• In the case of a pusher propeller, the propeller operates in the wake of the canard, fuselage, wing and landing gear. Also, the propeller diameter is often smaller than optimum, because of ground clearance considerations at rotation. A smaller propeller operating in a large wake will result in reduced propulsive efficiency.^{[citation needed]}

Although some of the advantages and disadvantages above apply to all situation a few of the disadvantages can be, and have been used in the design of high performance military aircraft were aerodynamic instability can allow for a large improvement in the maneuverability of the aircraft.^{[citation needed]}

Though in the civil aviation industry the disadvantages are seen to far outweigh the advantages and few canard design civil aircraft have been successful though with exception of a range of light aircraft produced by Burt Rutan.^{[citation needed]}

[edit] Examples of canard aircraft

Aircraft that have successfully employed this configuration include:

[edit] Gallery

Eurofighter Typhoon of the Royal Air Force displaying at the Farnborough Air Show, 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 Air Show	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	Mikoyan-Gurevich MiG-8, 1945
The Beechcraft Starship Executive Transport	A Pterodactyl Ascender II+2 showing its canard control surface

[edit] References

• Aircraft Structures and Systems (Second Edition): R Wilkinson: MechAero Publishing(2001)

[edit] See also

• Tandem wing
• Stabilator
• Tailplane