As Canard serves two purposes; it improves aircraft control, also contributes to lift, replacing the horizontal stabilizer and - theoretically - reducing overall drag.
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4$\begingroup$ What do you mean by sonic? $\endgroup$– JimCommented Jul 3, 2022 at 13:11
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$\begingroup$ Canard is only more efficient on aerodynamically unstable designs. We have a detailed explanation why somewhere around the site. $\endgroup$– Jan HudecCommented Jul 3, 2022 at 19:09
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2 Answers
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The forward canard does not replace the horizontal stabilizer, it actually forces a larger one for the same directional stability$^1$. It is also less efficient than the main wing at producing lift, essentially re-creating a biplane$^2$.
Studying the progression of the Wright designs (and others) sheds light on why canards fell out of favor and more conventional tractor designs with pitch control aft became the norm after 1910.
The early canard designs were particularly dangerous when both wings stalled, leading to an unrecoverable nose up descent. Interestingly, when early planes only could get a few feet off the ground, this type of stall was favorable because it tended to produce less damage than crashing nose first.
$^1$ canards can be used with delta wings, which are very stable in pitch
$^2$ positive lift from a canard could produce some fuel savings at cruise if the rear horizontal stabilizer/stabilator is set at 0 degrees and the wing is set at optimal AoA. Essentially, the elevator is taken off the back, where it usually produces downforce, and is put on the front, where it can produce up force. The benefit must be balanced with extra weight and complexity.
answered Jul 4, 2022 at 11:38
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They can be used on any aircraft designed for canards.
Retrofitting “all” supersonic aircraft with canards would be impractical for many reasons.
answered Jul 3, 2022 at 15:21