In a canard aircraft, what is the suggested position of the canard, with respect to the wing positioning? Considering the effect of down wash of the canard on the wing, what is the suggested position for a canard? Mid canard? High canard? Low canard?
There are two general configurations for canard wings, the long coupled and the short coupled canards. From Torenbeek:
Long coupled canard. This configuration is designed for minimal drag in cruise. The canard wing is placed far forward of the main wing in order to reduce interference drag. Vertical position is higher than the main wing to reduce adverse effects at high angle of attack.
Short coupled canard. The canard wing is again higher than the main wing: the interference is deliberately used to increase maximum lift (at the cost of high drag), achieved:
- at large angles of attack;
- on surfaces of low aspect ratio with highly swept back leading edges.
Quoting from Torenbeek:
In short, the canard layout appears to be suitable for transonic or supersonic and highly maneuverable aircraft, in the latter case if sufficient thrust reserve is available