Canard

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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. 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 the tail surface itself, when mounted in that configuration.

In English, canard also means hoax (but, in contemporary French usage, it means newspaper as in Le Canard Enchaîné). In the field of computing, it has also acquired the meaning of "confused and mistaken belief".

1 Canard aircraft characteristics
- 1.1 Advantages
- 1.2 Disadvantages
2 Examples of canard aircraft

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Canard aircraft characteristics

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Advantages

Image:XB-70 takeoff.jpg

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The canard surface normally produces positive (upwards) lift which adds to the overall lift, whereas a conventional tailplane normally produces a downforce, partially cancelling the lift from the main wings.

Careful design of a canard aircraft can make it effectively "stall-proof" - the canard surface stalls first which tends to pitch the nose down and prevent the main wing from stalling.

Canard designs can sometimes have a more useful range of centre of gravity.

Canard designs include elevators, stabilators, or elevons, the latter of which enhances roll rate.

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Disadvantages

The wing operates in the downwash from the canard surface, which reduces its efficiency.

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 (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 the difficulty of using flaps, takeoff and landing distances and speeds are often higher than for similar conventional airplanes.

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