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In aeronautics, a canard is a wing configuration in which a small forewing or foreplane is placed forward of the main wing of a fixed-wing aircraft or a weapon. The term "canard" may be used to describe the aircraft itself, the wing configuration, or the foreplane.. Canard wings are also extensively used in guided missiles and smart bombs. The term "canard" arose from the appearance of the
Santos-Dumont 14-bis The ''14-bis'' (french: Quatorze-bis), (), also known as ("bird of prey" in French), was a pioneer era, canard-style biplane designed and built by Brazilian aviation pioneer Alberto Santos-Dumont. In 1906, near Paris, the ''14-bis'' made a m ...
of 1906, which was said to be reminiscent of a
duck Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form ...
(''canard'' in French) with its neck stretched out in flight. 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 The Saab 37 Viggen ( Swedish for ''"the Bolt"'' or ''"the Tufted Duck"'' ( see name)) is a retired Swedish single-seat, single-engine, short-medium range combat aircraft. Development work on the type was initiated at Saab in 1952 and, follow ...
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 In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is ...
or during a stall. Canard foreplanes, whether used in a canard or three-surface configuration, have important consequences for the aircraft's longitudinal equilibrium, static and dynamic stability characteristics.


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 Karl Wilhelm Otto Lilienthal (23 May 1848 – 10 August 1896) was a German pioneer of aviation who became known as the "flying man". He was the first person to make well-documented, repeated, successful flights with gliders, therefore making ...
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 The ''14-bis'' (french: Quatorze-bis), (), also known as ("bird of prey" in French), was a pioneer era, canard-style biplane designed and built by Brazilian aviation pioneer Alberto Santos-Dumont. In 1906, near Paris, the ''14-bis'' made a m ...
aeroplane of 1906 had no "tail", but a
box kite A box kite is a high performance kite, noted for developing relatively high lift; it is a type within the family of cellular kites. The typical design has four parallel struts. The box is made rigid with diagonal crossed struts. There are two s ...
-like set of control surfaces in the front, pivoting on a
universal joint A universal joint (also called a universal coupling or U-joint) is a joint or coupling connecting rigid shafts whose axes are inclined to each other. It is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges ...
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 C 1 biplane fighter, having a canard foreplane and rear-mounted pusher propeller. The C 1 was a failure. First flown in 1927, the experimental
Focke-Wulf F 19 The Focke-Wulf F 19 ''Ente'' (German: "Duck") was a German experimental "canard" aircraft in the late 1920s. Design The F 19 Ente was a high-wing monoplane with a canard layout and fixed tricycle undercarriage. The pilot sat in an open cockpit ...
"Ente" (duck) 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 The Curtiss-Wright XP-55 Ascender (company designation CW-24) is a 1940s United States prototype fighter aircraft built by Curtiss-Wright. Along with the Vultee XP-54 and Northrop XP-56, it resulted from United States Army Air Corps proposal ...
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. Ultimately, no production aircraft were completed. The Shinden was ordered into production "off the drawing board" but only prototypes had flown by the time the war ended. In 1945 in Europe, what may have been the first canard designed and flown in the
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
appeared as a test aircraft, the experimental Mikoyan-Gurevich MiG-8 ''Utka'' (Russian for "duck"), a lightweight propeller aircraft. It was noted 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 (conventional layout)
MiG-15 The Mikoyan-Gurevich MiG-15 (russian: Микоя́н и Гуре́вич МиГ-15; USAF/DoD designation: Type 14; NATO reporting name: Fagot) is a jet fighter aircraft developed by Mikoyan-Gurevich for the Soviet Union. The MiG-15 was one of ...
jet fighter.


Canard revival

With the arrival of the
jet age The Jet Age is a period in the history of aviation defined by the advent of aircraft powered by jet turbine engines, and by the social change this brought about. Jet airliners were able to fly much higher, faster, and farther than older pisto ...
and supersonic flight, American designers, notably North American Aviation, began to experiment with supersonic canard delta designs, with some such as the
North American XB-70 Valkyrie The North American Aviation XB-70 Valkyrie was the prototype version of the planned B-70 nuclear-armed, deep-penetration supersonic strategic bomber for the United States Air Force Strategic Air Command. Designed in the late 1950s by North Ame ...
and the Soviet equivalent
Sukhoi T-4 The Sukhoi T-4, or "Aircraft 100", or "Project 100", or "Sotka" was a Soviet high-speed reconnaissance, anti-ship and strategic bomber aircraft that did not proceed beyond the prototype stage. It is sometimes called the Su-100. Design and devel ...
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.''Delta wing canard aircraft'', US Paten
US3188022 A
Anderson, S.B.
A Look at Handling Qualities of Canard Configurations
NASA Technical Memorimdum 88354, 1986, page 21.
It was built as the
Saab 37 Viggen The Saab 37 Viggen ( Swedish for ''"the Bolt"'' or ''"the Tufted Duck"'' ( see name)) is a retired Swedish single-seat, single-engine, short-medium range combat aircraft. Development work on the type was initiated at Saab in 1952 and, follow ...
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 Mirage is a name given to several types of jet aircraft designed by the French company Dassault Aviation (formerly Avions Marcel Dassault), some of which were produced in different variants. Most were supersonic fighters with delta wings. The most s ...
delta-winged jet fighter. These included variants of the French
Dassault Mirage III The Dassault Mirage III () is a family of single/dual-seat, single-engine, fighter aircraft developed and manufactured by French aircraft company Dassault Aviation. It was the first Western European combat aircraft to exceed Mach number, Mach 2 ...
, Israeli
IAI Kfir , abbreviated , is a Japanese martial art that emphasizes being aware and capable of quickly drawing the sword and responding to sudden attacks.Christensen, Karen and Allen Guttmann et.al (2001) ''International Encyclopedia of Women and Sport ...
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 Elbert Leander "Burt" Rutan (; born June 17, 1943) is a retired American aerospace engineer and entrepreneur noted for his originality in designing light, strong, unusual-looking, and energy-efficient air and space craft. He designed the recor ...
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 The Rutan VariEze is a composite, canard aircraft designed by Burt Rutan. It is a high-performance homebuilt aircraft, hundreds of which have been constructed. The design later evolved into the Long-EZ and other, larger cabin canard aircraft ...
and
Long-EZ The Rutan Model 61 Long-EZ is a tandem 2-seater homebuilt aircraft designed by Burt Rutan's Rutan Aircraft Factory. The Long-EZ has a canard layout, a swept wing with wingtip rudders, and a pusher engine and propeller. The tricycle landing g ...
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 The Beechcraft Starship is a twin-turboprop six- to eight-passenger pressurized business aircraft produced by Beech Aircraft Corporation. Development Development of the Starship began in 1979 when Beech decided to explore designs for a succe ...
.


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
Dassault Rafale The Dassault Rafale (, literally meaning "gust of wind", and "burst of fire" in a more military sense) is a French twin-engine, canard delta wing, multirole fighter aircraft designed and built by Dassault Aviation. Equipped with a wide range ...
multirole fighter first flew in 1986, followed by the
Saab Gripen The Saab JAS 39 Gripen (; English: ''griffin'') is a light single-engine multirole fighter aircraft manufactured by the Swedish aerospace and defense company Saab AB. The Gripen has a delta wing and canard configuration with relaxed stabilit ...
(first to enter service) in 1988, and the
Eurofighter Typhoon The Eurofighter Typhoon is a European multinational twin-engine, canard delta wing, multirole fighter. The Typhoon was designed originally as an air-superiority fighter and is manufactured by a consortium of Airbus, BAE Systems and Leonardo ...
in 1994. These three types and related design studies are sometimes referred to as the euro-canards or eurocanards. The Chinese
Chengdu J-10 The Chengdu J-10 Vigorous Dragon (; NATO reporting name: Firebird), is a medium-weight, single-engine, multirole combat aircraft capable of all-weather operations, configured with a delta wing and canard design, with fly-by-wire flight contr ...
appeared in 1998.


Basic design principles

A canard foreplane may be used for various reasons such as lift, (in)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 In aeronautics, downwash is the change in direction of air deflected by the aerodynamic action of an airfoil, wing, or helicopter rotor blade in motion, as part of the process of producing lift.Crane, Dale: ''Dictionary of Aeronautical Terms, thir ...
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 is 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 In aeronautics, a tailless aircraft is an aircraft with no other horizontal aerodynamic surface besides its main wing. It may still have a fuselage, vertical tail fin (vertical stabilizer), and/or vertical rudder. Theoretical advantages of the ...
, 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 (i.e. control-canards) 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 A tailplane, also known as a horizontal stabiliser, is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplan ...
, whether stability is achieved statically or artificially (fly-by-wire). Being placed ahead of the center of gravity, a canard foreplane acts directly to reduce longitudinal static stability (stability in pitch). 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 In fluid dynamics, the lift coefficient () is a dimensionless quantity that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area. A lifting body is a foil or a com ...
with angle of attack (lift coefficient slope) 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 (so the wing loading) 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 Camber may refer to a variety of curvatures and angles: * Camber angle, the angle made by the wheels of a vehicle * Camber beam, an upward curvature of a joist to compensate for load deflection due in buildings * Camber thrust in bike technology * ...
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 Elbert Leander "Burt" Rutan (; born June 17, 1943) is a retired American aerospace engineer and entrepreneur noted for his originality in designing light, strong, unusual-looking, and energy-efficient air and space craft. He designed the recor ...
is a high aspect ratio canard with higher lift coefficient (the wing loading of the canard is between 1.6 and 2 times the wing one) and a canard airfoil whose lift coefficient slope is non-linear (nearly flat) 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 (see above). Conversely, a propeller located ahead of the canard (increasing the lift slope 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

A close-coupled canard has been shown to benefit a supersonic delta wing design which gains lift in both
transonic Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transoni ...
flight (such as for
supercruise Supercruise is sustained supersonic flight of a supersonic aircraft with a useful cargo, passenger, or weapons load without using afterburner (also known as "reheat"). Many supersonic military aircraft are not capable of supercruise and can only m ...
) and also in low speed flight (such as take offs and landings). 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 (and therefore typically at low speeds) 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 , abbreviated , is a Japanese martial art that emphasizes being aware and capable of quickly drawing the sword and responding to sudden attacks.Christensen, Karen and Allen Guttmann et.al (2001) ''International Encyclopedia of Women and Sport ...
, have landing flaps as on the
Saab Viggen The Saab 37 Viggen ( Swedish for ''"the Bolt"'' or ''"the Tufted Duck"'' ( see name)) is a retired Swedish single-seat, single-engine, short-medium range combat aircraft. Development work on the type was initiated at Saab in 1952 and, follow ...
, or be moveable and also act as a control-canard during normal flight as on the
Dassault Rafale The Dassault Rafale (, literally meaning "gust of wind", and "burst of fire" in a more military sense) is a French twin-engine, canard delta wing, multirole fighter aircraft designed and built by Dassault Aviation. Equipped with a wide range ...
.


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 In fluid dynamics, the lift coefficient () is a dimensionless quantity that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area. A lifting body is a foil or a com ...
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 The Tupolev Tu-144 (russian: Tyполев Ту-144; NATO reporting name: Charger) is a Soviet supersonic passenger airliner designed by Tupolev in operation from 1968 to 1999. The Tu-144 was the world's first commercial supersonic transport ai ...
. 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 The Rockwell B-1 Lancer is a supersonic variable-sweep wing, heavy bomber used by the United States Air Force. It is commonly called the "Bone" (from "B-One"). It is one of three strategic bombers serving in the U.S. Air Force fleet along with ...
has small canard vanes or fins on either side of the forward fuselage that form part of an active damping system that reduces aerodynamic buffeting during high-speed, low altitude flight. Such buffeting would otherwise cause crew fatigue and reduce airframe life during prolonged flights.


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 The Eurofighter Typhoon is a European multinational twin-engine, canard delta wing, multirole fighter. The Typhoon was designed originally as an air-superiority fighter and is manufactured by a consortium of Airbus, BAE Systems and Leonardo ...
uses software control of its canards in order to reduce its effective
radar cross section Radar cross-section (RCS), also called radar signature, is a measure of how detectable an object is by radar. A larger RCS indicates that an object is more easily detected. An object reflects a limited amount of radar energy back to the source. ...
. Canards have been incorporated on stealth aircraft such as Lockheed Martin's Joint Advanced Strike Technology (JAST) program. and McDonnell Douglas / NASA's X-36 research prototype."Agility+Stealth = X-36: formula for an advanced fighter "
''Design News'' 14 January 2013


See also

*
List of canard aircraft This is a list of canard aircraft, having a foreplane in front of the main wing instead of a conventional tailplane. , - , AASI Jetcruzer , , USA , , Jet , , Transport , , 1989 , , Prototype , , 5 , , Pusher configuration. , - , AEA J ...
*
Tandem wing QAC Quickie Q2 A tandem wing is a wing configuration in which a flying craft or animal has two or more sets of wings set one behind another. All the wings contribute to lift. The tandem wing is distinct from the biplane in which the wings are ...
*
Rotorcraft A rotorcraft or rotary-wing aircraft is a heavier-than-air aircraft with rotary wings or rotor blades, which generate lift by rotating around a vertical mast. Several rotor blades mounted on a single mast are referred to as a rotor. The Internat ...


References


Citations


Bibliography

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Further reading

* . * . * . * . *


External links

{{DEFAULTSORT:Canard (Aeronautics) Aircraft components Wing configurations Aircraft wing design