Canard
In aeronautics, canard (French for duck) is a type 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 Santos-Dumont 14-bis, were seen by observers to resemble a flying duck — hence the name.
The term canard has also come to mean any horizontal airfoil mounted in front of the main wing.
Other meanings
In English, canard also means 'a deliberately false story' (see Antisemitic canard for a common genre of canard). In contemporary French usage, it is a slang for newspaper as in Le Canard Enchaîné. In the field of computing, it has also acquired the meaning of "confused and mistaken belief". In Russian, the term утка (duck) is used for canard.
Canard aircraft characteristics
Advantages
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Canard designs can sometimes have a more useful range of centre of gravity.
The fuselage in a canard design is supported in two places, as the plane has two wings. Because of the added support the fuselage does not have to be as strong, which means it can be lighter. However this saving in weight is minimal when compared to the extra weight needed to strengthen and enlarge the wing.
Canard designs include elevators, stabilators, or elevons, the last of which enhances roll rate.
Because the canard reduces the lift of the main wing, it reduces the lift-induced drag of the wing, lowering the overall drag of the aircraft.
If the plane stalls the tailplane stalls before the main wing. This causes the nose to pitch down, which helps the plane to recover from a stall.
Disadvantages
The wing operates in the downwash from the canard surface, which reduces its efficiency although the effects of the downwash does not cause as large of a problem as the tailplane would experience in a conventional set-up.
Because the main wing operates in the downwash of the horizontal stabilizer the wing root does not achieve its maximum lift. This means that the wing tip creates more lift than the wing root, as a result the wing has to be significantly strengthened. Strengthening the wing adds weight to the aircraft. Another adverse effect of the wing not creating its maximum lift is that more wing area is 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 many canard designs have no flaps at all.
In order to achieve longitudinal stability, most canard designs feature a small canard surface operating at a high lift coefficient (CL), while the main wing, although much larger, operates at a much smaller CL 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.
Examples of canard aircraft
Aircraft that have successfully employed this configuration include:
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Naval canards
Submarines also use canards to control "flight" through water without noisy variation in ballast. Large surface vessels use retractable canards to stabilize in rough seas or extreme manoeuvers.