A canard is an aeronautical arrangement
wherein a small forewing or foreplane is
placed forward of the main wing of a
fixed-wing aircraft. The term "canard"
may be used to describe the aircraft
itself, the wing configuration or the
foreplane.
Despite the use of a canard surface on
the first powered aeroplane, the Wright
Flyer of 1903, canard designs were not
built in quantity until the appearance
of the Saab Viggen jet fighter in 1967.
The aerodynamics of the canard
configuration are complex and require
careful analysis.
Rather than use the conventional
tailplane configuration found on most
aircraft, an aircraft designer may adopt
the canard configuration to reduce the
main wing loading, to better control the
main wing airflow, or to increase the
aircraft’s maneuverability, especially
at high angles of attack or during a
stall. Canard foreplanes, whether used
in a canard or three-surface
configuration, have important
consequences on the aircraft’s
longitudinal equilibrium, static and
dynamic stability characteristics.
Etymology 
The term “canard” arose from the
appearance of the Santos-Dumont 14-bis
of 1906, which was said to be
reminiscent of a duck with its neck
stretched out in flight.
History 
= Pioneer years =
The Wright Brothers began experimenting
with the foreplane configuration around
1900. Their first kite included a front
surface for pitch control and they
adopted this configuration for their
first Flyer. They were suspicious of the
aft tail because Otto Lilienthal had
been killed in a glider with one. The
Wrights realised that a foreplane would
tend to destabilise an aeroplane but
expected it to be a better control
surface, in addition to being visible to
the pilot in flight. They believed it
impossible to provide both control and
stability in a single design, and opted
for control.
Many pioneers initially followed the
Wrights' lead. For example, the
Santos-Dumont 14-bis aeroplane of 1906
had no "tail", but a box kite-like set
of control surfaces in the front,
pivoting on a universal joint on the
fuselage's extreme nose, making it
capable of incorporating both yaw and
pitch control. The Fabre Hydravion of
1910 was the first floatplane to fly and
had a foreplane.
But canard behaviour was not properly
understood and other European
pioneers—among them, Louis Blériot—were
establishing the tailplane as the safer
and more "conventional" design. Some,
including the Wrights, experimented with
both fore and aft planes on the same
aircraft, now known as the three surface
configuration.
After 1911, few canard types would be
produced for many decades. In 1914 W.E.
Evans commented that "the Canard type
model has practically received its
death-blow so far as scientific models
are concerned."
= 1914 to 1945 =
Experiments continued sporadically for
several decades.
In 1917 de Bruyère constructed his C1
biplane fighter, having a canard
foreplane and rear-mounted pusher
propellor. The C.1 was a failure.
First flown in 1927, the experimental
Focke-Wulf F 19 "Ente" was more
successful. Two examples were built and
one of them continued flying until 1931.
Immediately before and during World War
II several experimental canard fighters
were flown, including the Ambrosini
SS.4, Curtiss-Wright XP-55 Ascender and
Kyūshū J7W1 Shinden. These were attempts
at using the canard configuration to
give advantages in areas such as
performance, armament disposition or
pilot view, but no production aircraft
were completed. The Shinden was ordered
into production "off the drawing board"
but hostilities ceased before any other
than prototypes had flown.
Just after the end of World War II in
Europe in 1945, what may have been the
first canard designed and flown in the
Soviet Union appeared as a test
aircraft, the lightweight
Mikoyan-Gurevich MiG-8 Utka. It was
reportedly a favorite among MiG OKB test
pilots for its docile, slow-speed
handling characteristics and flew for
some years, being used as a testbed
during development of the swept wing of
the MiG-15 jet fighter.
= The canard revival =
With the arrival of the jet age and
supersonic flight, American designers
and especially North American began to
experiment with supersonic canard delta
designs, with some such as the North
American XB-70 Valkyrie and the Soviet
equivalent Sukhoi T-4 flying in
prototype form. But the stability and
control problems encountered prevented
widespread adoption.
In 1963 the Swedish company Saab
patented a delta-winged design which
overcame the earlier problems, in what
has become known as the close-coupled
canard. It was built as the Saab 37
Viggen and in 1967 became the first
modern canard aircraft to enter
production. The success of this aircraft
spurred many designers, and canard
surfaces sprouted on a number of types
derived from the popular Dassault Mirage
delta-winged jet fighter. These included
variants of the French Dassault Mirage
III, Israeli IAI Kfir and South African
Atlas Cheetah. The close-coupled canard
delta remains a popular configuration
for combat aircraft.
The Viggen also inspired the American
Burt Rutan to create a two-seater
homebuilt canard delta design,
accordingly named VariViggen and flown
in 1972. Rutan then abandoned the delta
wing as unsuited to such light aircraft.
His next two canard designs, the VariEze
and Long-EZ had longer-span swept wings.
These designs were not only successful
and built in large numbers but were
radically different from anything seen
before. Rutan's ideas soon spread to
other designers. From the 1980s they
found favour in the executive market
with the appearance of types such as the
OMAC Laser 300, Avtek 400 and Beech
Starship.
= Computer control =
Static canard designs can have complex
interactions in airflow between the
canard and the main wing, leading to
issues with stability and behaviour in
the stall. This limits their
applicability. The development of
fly-by-wire and artificial stability
towards the end of the century opened
the way for computerized controls to
begin turning these complex effects from
stability concerns into maneuverability
advantages.
This approach produced a new generation
of military canard designs. The Saab JAS
39 Gripen multirole fighter flew in 1988
and was adopted by a number of national
air forces. Others followed. Types which
would follow it into operational service
included the Eurofighter Typhoon in 1994
and the Chinese Chengdu J-10 in 1998.
Basic design principles 
A canard foreplane may be used for
various reasons such as lift,stability,
trim, flight control, or to modify
airflow over the main wing. Design
analysis has been divided into two main
classes, for the lifting-canard and the
control-canard. These classes may follow
the close-coupled type or not, and a
given design may provide either or both
of lift and control.
= Lift =
In the lifting-canard configuration, the
weight of the aircraft is shared between
the wing and the canard. It has been
described as an extreme conventional
configuration but with a small highly
loaded wing and an enormous lifting tail
which enables the centre of mass to be
very far aft relative to the front
surface.
A lifting canard generates an upload, in
contrast to a conventional aft-tail
which sometimes generates negative lift
that must be counteracted by extra lift
on the main wing. As the canard lift
adds to the overall lift capability of
the aircraft, this may appear to favor
the canard layout. In particular, at
takeoff the wing is most heavily loaded
and where a conventional tail exerts a
downforce worsening the load, a canard
exerts an upward force relieving the
load. This allows a smaller main wing.
However, the foreplane also creates a
downwash which can affect the wing lift
distribution unfavorably, so the
differences in overall lift and induced
drag are not obvious and they depend on
the details of the design.
A danger associated with an
insufficiently loaded canard—i.e. when
the center of gravity too far aft—is
that when approaching stall, the main
wing may stall first. This causes the
rear of the craft to drop, deepening the
stall and sometimes preventing recovery.
To ensure safe pitch stability in the
stall, the canard must stall first, so
the wing must always stay below its
maximum lift capability. Hence, the wing
must be larger than otherwise necessary,
reducing or even reversing the reduction
in size enabled by the canard lift.
With a lifting-canard type, the main
wing must be located further aft of the
center of gravity than a conventional
wing, and this increases the downward
pitching moment caused by the deflection
of trailing-edge flaps. Highly loaded
canards do not have sufficient extra
lift available to balance this moment,
so lifting-canard aircraft cannot
readily be designed with powerful
trailing-edge flaps.
= Control =
Pitch control in a canard type may be
achieved either by the canard surface,
as on the control-canard or in the same
way as a tailless aircraft, by control
surfaces at the rear of the main wing,
as on the Saab Viggen.
In a control-canard design, most of the
weight of the aircraft is carried by the
wing and the canard is used primarily
for pitch control during maneuvering. A
pure control-canard operates only as a
control surface and is nominally at zero
angle of attack and carrying no load in
normal flight. Modern combat aircraft of
canard configuration typically have a
control-canard driven by a computerized
flight control system.
Canards with little or no loading may be
used to intentionally destabilize some
combat aircraft in order to make them
more manoeuvrable. The electronic flight
control system uses the pitch control
function of the canard foreplane to
create artificial static and dynamic
stability.
A benefit obtainable from a
control-canard is the correction of
pitch-up during a wingtip stall. An
all-moving canard capable of a
significant nose-down deflection can be
used to counteract the pitch-up due to
the tip stall. As a result, the aspect
ratio and sweep of the wing can be
optimized without having to guard
against pitch-up. A highly loaded
lifting canard does not have sufficient
spare lift capacity to provide this
protection.
= Stability =
A canard foreplane may be used as a
horizontal stabiliser, whether stability
is achieved statically or artificially.
Being placed ahead of the center of
gravity, a canard foreplane acts
directly to reduce Longitudinal static
stability. The first airplane to achieve
controlled, powered flight, the Wright
Flyer, was conceived as a control-canard
but in effect was also an unstable
lifting canard. At that time the Wright
Brothers did not understand the basics
of pitch stability of the canard
configuration, and were in any event
more concerned with controllability.
Nevertheless, a canard stabiliser may be
added to an otherwise unstable design to
obtain overall static pitch stability.
To achieve this stability, the change in
canard lift coefficient with angle of
attack should be less than that for the
main plane. A number of factors affect
this characteristic.
For most airfoils, lift slope decreases
at high lift coefficients. Therefore,
the most common way in which pitch
stability can be achieved is to increase
the lift coefficient of the canard. This
tends to increase the lift-induced drag
of the foreplane, which may be given a
high aspect ratio in order to limit
drag. Such a canard airfoil has a
greater airfoil camber than the wing.
Another possibility is to decrease the
aspect ratio of the canard, with again
more lift-induced drag and possibly a
higher stall angle than the wing.
A design approach used by Burt Rutan is
a high aspect ratio canard with higher
lift coefficient and a canard airfoil
whose lift coefficient slope is
non-linear between 14° and 24°.
Another stabilisation parameter is the
power effect. In case of canard pusher
propeller: "the power-induced flow clean
up of the wing trailing edge"  increases
the wing lift coefficient slope.
Conversely, a propeller located ahead of
the canard has a strong destabilising
effect.
= Trim =
A highly-loaded lifting canard may not
have sufficient spare lifting capacity
to accommodate large movements of the
centre of pressure or of the centre of
gravity. Trim may be accomplished in
similar manner to a tailless craft, by
adjustment of trailing-edge surfaces.
In particular, the use of landing flaps
on the main wing causes a large trim
change. The Saab Viggen has flaps on the
canard surface which were deployed
simultaneously to cancel out the change
in trim. The Beech Starship uses
variable-sweep foreplanes to trim the
position of the lift force.
When the main wing is most loaded, at
takeoff, to rotate the nose up a
conventional tailplane typically pushes
down while a foreplane lifts up. In
order to maintain trim the main wing on
a canard design must therefore be
located further aft relative to the
centre of gravity than on the equivalent
conventional design.
Variations 
= Close coupling =
In the close-coupled delta wing canard,
the foreplane is located just above and
forward of the wing. The vortices
generated by a delta-shaped foreplane
flow back past the main wing and
interact with its own vortices. Because
these are critical for lift, a
badly-placed foreplane can cause severe
problems. By bringing the foreplane
close to the wing and just above it in a
close-coupled arrangement, the
interactions can be made beneficial,
actually helping to solve other problems
too. For example at high angles of
attack the canard surface directs
airflow downward over the wing, reducing
turbulence which results in reduced drag
and increased lift. Typically the
foreplane creates a vortex which
attaches to the upper surface of the
wing, stabilising and re-energising the
airflow over the wing and delaying or
preventing the stall.
The canard foreplane may be fixed as on
the IAI Kfir, have landing flaps as on
the Saab Viggen, or be moveable and also
act as a control-canard during normal
flight as on the Dassault Rafale.
A close-coupled canard has been shown to
benefit a supersonic delta wing design
which gains lift in both transonic
flight and also in low speed flight.
= Free-floating canard =
A free-floating canard is designed to
change its angle of incidence to the
fuselage without pilot input. In normal
flight, the air pressure distribution
maintains its angle of attack to the
airflow, and therefore also the lift
coefficient it generates, to a constant
amount.
A free-floating mechanism may increase
static stability and provide safe
recovery from high angle of attack
evolutions. However, it negatively
affects stall characteristics, since the
main wing may stall before the canard.
Control surfaces may be added to the
free-floating canard, allowing pilot
input to affect the generated lift, thus
providing pitch control, or trim
adjustment.
= Variable geometry =
The Beechcraft Starship has a variable
sweep canard surface. The sweep is
varied in flight by swinging the
foreplanes forward to increase their
effectiveness and so trim out the
nose-down pitching effect caused by the
wing flaps when deployed.
A moustache is a small, high aspect
ratio foreplane which is deployed for
low-speed flight in order to improve
handling at high angles of attack such
as during takeoff and landing. It is
retracted at high speed in order to
avoid the wave drag penalty of a canard
design. It was first seen on the
Dassault Milan and later on the Tupolev
Tu-144. NASA has also investigated a
one-piece slewed equivalent called the
conformably stowable canard, where as
the surface is stowed one side sweeps
backwards and the other forwards.
= Ride control =
The Rockwell B-1 Lancer shows small
front fin surfaces as part of an active
vibration damping system that reduces
significant aerodynamic buffeting during
high-speed, low altitude flight. This
buffeting is a leading cause of crew
fatigue and reduced airframe life. As
placed in front of the plane, these
surfaces are described as "canard vanes"
or "canard fins".
= Stealth =
Canard aircraft can potentially have
poor stealth characteristics because
they present large, angular surfaces
that tend to reflect radar signals
forwards. The Eurofighter Typhoon uses
software control of its canards in order
to reduce its effective radar cross
section.
Canards have also been incorporated on
stealth aircraft such as Lockheed
Martin's Joint Advanced Strike
Technology program. and McDonnell
Douglas / NASA's X-36 research
prototype.
See also 
Canard Rotor/Wing
List of canard aircraft
Tandem wing
References 
= Citations =
= Bibliography =
Burns, BRA, "Were the Wrights Right?",
Air International .
———, "Canards: Design with Care", Flight
International, pp. 19–21 .
Neblett, Evan; Metheny, Michael ‘Mike’;
Leifsson, Leifur Thor, "Canards", AOE
4124 Class notes .
Garrison, P, "Three's Company", Flying
129, pp. 85–86 
Raymer, Daniel P, Aircraft Design: A
Conceptual Approach, Washington, DC:
American Institute of Aeronautics and
Astronautics, ISBN 0-930403-51-7 
Further reading 
Abzug; Larrabee, Airplane Stability and
Control, Cambridge University Press .
Gambu, J; Perard, J, "Saab 37 Viggen",
Aviation International, pp. 29–40 .
Lennon, Andy, Canard : a revolution in
flight, Aviation .
Rollo, Vera Foster, Burt Rutan
Reinventing the Airplane, Maryland
Historical Press .
Wilkinson, R. Aircraft Structures and
Systems. MechAero Publishing. 
Selberg, Bruce P and Cronin, Donald L,
Aerodynamic-Structural Study of Canard
Wing, Dual Wing, and Conventional Wing
Systems for General Aviation
Applications. University of
Missouri-Rolla. Contract Report 172529,
National Aeronautics and Space
Administration [1]
External links 
