A Summary of Canard Advantages and Disadvantages
- Possibility for very good stalling characteristics without elevator
- Sometimes a desirable layout from the packaging standpoint: Main wing
carry-through behind cabin, pusher engine installation simplified.
- Synergistic use of winglets for directional stability.
- In certain cases a simplified control linkage is possible.
- When wing flaps are not desired (for simplicity as in ultralights, or
competition rules as with standard class sailplanes for example) the CLmax
of a canard may exceed that of an aft-tail airplane.
- For unstable aircraft, canard designs may have a CLmax and/or drag
- Control authority is larger for unstable canard aircraft at high CL
than for unstable aft-tail designs.
- Fuel center of gravity lies farther behind aircraft c.g. than in conventional
designs. This means that a large c.g. range is produced or that the fuel
must be held elsewhere (e.g. strakes near the wing root.)
- CLmax problems with flaps or margin on the entire wing: Flaps produce
a larger pitching moment about the c.g. on a canard aircraft. This results
in the need for both large canard aerodynamic incidence change and high
maximum canard lift coefficient. Note that since the value of a S is usually
larger for canard designs, Cm0 has a greater impact on L than it does on
- Induced drag / CLmax incompatibility: Canard designs can achieve equal
or better CLmax values than conventional designs, and similar values of
span efficiency. However, the configurations with high CLmax values have
terrible values of e and those with respectable e 's have low maximum
- Directional stability: The distance from the aircraft c.g. to the
most aft part of the airplane is usually smaller on canard aircraft. This
poses a problem for locating a vertical stabilizer and may result in very
large vertical surfaces. (Note, however, that winglets may be used to advantage
in this case.)
- Wing twist distribution is strange and CL dependent: The wing additional
load distribution is distorted by the canard wake.
- Power effects on canard - deep stall: Accidents have been associated
with tractor canard configurations for which the propeller slipstream has
prevented canard stall before wing stall. The result is a possible deep-stall
- Finally, and perhaps most importantly, canard sizing is much more critical
than aft tail sizing. By choosing a canard which is somewhat too big or
too small the aircraft performance can be severely affected. It is easy
to make a very bad canard design.