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Canard

A 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 layout has advantages and disadvantages:

Advantages

The canard surface normally produces positive (upwards) lift whereas a conventional tailplane normally produces a downforce.

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.

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 Beech 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.


A canard is another term for a hoax.



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