Canard (aeronautics)

In aeronautics, a canard (French for "duck") is either a canard aircraft or a canard surface (foreplane) or each lateral surface of the foreplane. A canard (aircraft), or canard design, is a configuration of fixed-wing aircraft in which a main wing is setted backward, behind a smaller forward horizontal surface, named canard or foreplane, or sometimes stabilizer. In contrast a conventional aircraft has a small horizontal surface or tailplane behind the main wing.^[1][2][3]

Contents 1 History 1.1 "Canard" name 1.2 Canard asleep 1.3 Canard renewal 1.4 Modern canards 2 Canard aircraft classes 2.1 Lifting-canard 2.2 Control-canard 2.3 Close-coupled canard 2.4 Variable geometry canard 2.5 Special front surfaces 3 Canard aircraft pitch stability 3.1 Wright Flyer stability 4 Examples of canard aircraft 4.1 Aircraft with a canard foreplane 5 See also 6 References 7 Further reading 8 External links

History [edit]

The Wright brothers started it all about 1900. Following their first aeronautical experiment, a kite using wing warping for turning,^[4] they added a pitch control front surface : the "first to fly" was a canard aircraft. The Wrights selected a canard format because they were aware that Lillenthal - in a glider with an aft tail - had been killed due to a lack of pitch control and they expected a canard to be more controllable, and that in flight they would be able to see the control surface.

"Canard" name [edit]

The early aircraft Santos-Dumont 14-bis of 1906 had no tail and small control surfaces in the front. Its appearance reminded the French public of a flying duck (Fr. canard).^[5] The first floatplane, the Fabre Hydravion in 1910, of canard configuration, was named "Le Canard".^[6] From thence onwards, all aeroplanes with a forward elevator were to be knowned as canards ^[7]

Canard asleep [edit]

By 1910, european pioneers had eventually established the "conventional" tail design. The Wright canard arrangement, with other features like wing warping, is obsolete for a while. During the twenties, the Focke-Wulf F 19 is a rare example of canard experiment. Later, some experimental canards (military like Ambrosini SS.4, Curtiss-Wright XP-55 Ascender, Kyūshū J7W1 Shinden) or tandem (Miles M.35 Libellula, Miles M.39B Libellula) are built, "failing again to surpass the experimental stage".^[8]

Canard renewal [edit]

More than fifty years later, the Saab 37 Viggen became in 1967 the first mitary aircraft to enter production, opening a new perspective in military canard design. This model brought the inspiration basis for Burt Rutan personal two seater homebuilt canard, accordingly named VariViggen (1972), followed by the "different" ^[9] composite built VariEze and later Long-EZ, may be the most built canard aircraft.^[10] The eighties saw also the birth of executive canards : OMAC Laser 300, Avtek 400, Beech Starship and the cute Piaggio P.180 Avanti, a three surface (canard added) pusher aircraft.

Modern canards [edit]

The key point of the canard renewal is into the stabilisation mode. Modern computerized controls have begun to turn the complex interactions in airflow between the canard and the main wing from stability concerns into maneuverability advantages.^[11] Some canard aircraft designs may have trim advantages that allow them to better adjust for center of mass changes due to load changes or fuel use, and for aerodynamic center changes when shifting between subsonic and supersonic flight.

Canard aircraft are often said to have poor stealth characteristics because they present large, angular surfaces that tend to reflect radar signals forwards.^[11][12] Canards have nevertheless been incorporated on several proposed stealth aircraft. Northrop's proposal for the Naval Advanced Tactical Fighter (ATF), termed NATF-23, incorporated canard on a stealthy airframe.^[13][14] Lockheed Martin employed canards on a stealth airframe in the Joint Advanced Strike Technology (JAST) program.^[15][16] McDonnell Douglas and NASA's stealthy X-36 featured the use of canards.^[17] The Eurofighter Typhoon uses software control of its canards in order to reduce its effective radar cross section.^[18][19]

Canard aircraft classes [edit]

A canard foreplane may be used for lift and/or control. Canard designs may be divided into into two main classes, the lifting-canard and the control-canard.^[20] These classes may follow the close-coupled type or not.

Lifting-canard [edit]

In this configuration, the weight of the aircraft is shared between the wing and the canard.
It may be described as an extreme conventional configuration with the following features : a small highly-loaded wing, and an enormous lifting tail which enables the CG to be very far aft relative to the front surface.^[21]

A lifting-canard generates an upload, in contrast to a conventional aft-tail which generates negative lift that must be counteracted by extra lift on the main wing. As the canard lift appears to increase the overall lift capability of the aircraft, this may appear to unambiguously favor the canard layout.
However, the foreplane downwash effect on the wing lift distribution is unfavorable for the canard concept, so the difference in overall induced drag is actually not obvious, and depends on the details of the configuration.^[11][21][22] Also, pitch stability requirements dictate that the canard must stall before the wing, so the wing can never reach its maximum lift capability. Hence, the wing must then be larger than on the conventional configuration, which increases its area, weight and profile drag.^[11][22]

Control-canard [edit]

In both earlier and later control-canard, most of the weight of the aircraft is carried by the wing and the canard is used primarily for longitudinal control during maneuvering. Thus, a control-canard mostly operates only as a control surface and is usually at zero angle of attack, carrying no aircraft weight in normal flight. Combat aircraft of canard configuration typically have a control-canard. In modern combat aircraft, the canard is usually driven by a computerized flight control system.^[20]

One benefit obtainable from a control-canard is the avoidance of pitch-up. An all-moving canard capable of a significant nose-down deflection will protect against pitch-up. As a result, the aspect ratio and wing-sweep of the wing can be optimized without having to guard against pitch-up.^[20]

They are used to intentionally destabilize some combat aircraft in order to make them more manoeuvrable. In this case, electronic flight control systems use the pitch control function of the canard foreplane to create artificial static and dynamic stability.^[11][22]

Close-coupled canard [edit]

In the close-coupled canard, the foreplane is located just above and forward of the wing. At high angles of attack the canard surface directs airflow downwards over the wing, reducing turbulence which results in reduced drag and increased lift.^[23]

The canard foreplane may be fixed as on the IAI Kfir, or have landing flaps as on the Saab Viggen, or it may be moveable and also act as a control-canard during normal flight as on the Dassault Rafale.

A close-coupled canard is very useful for a supersonic delta wing design which gains lift in both transonic flight (such as for supercruise) and also in low speed flight (such as take offs and landings).^[24]

A moustache is a small, high aspect ratio foreplane of close-coupled configuration. The surface is typically retractable at high speed and is deployed only for low-speed flight. First seen on the Dassault Milan, and later on the Tupolev Tu-144.

Variable geometry canard [edit]

The Beechcraft Starship had a variable sweep canard surface.

NASA has investigated the use of a stowable canard for use at low speed that is withdrawn from the airstream at high speeds in order to avoid the Wave drag penalty of a canard design.^[25]

Special front surfaces [edit]

The Rockwell B-1 Lancer shows small front fin surfaces as part of an active vibration damping system that reduces significant aerodynamic buffeting when flying fast at low altitude, leading to crew fatigue and reduced airframe life. As placed in front of the plane, these surfaces are described as "canard vanes" ^[26] or "canard fins".^[27]

Canard aircraft pitch stability [edit]

Canard foreplanes, being placed ahead of the center of gravity, reduce static longitudinal stability, in which the foreplane is involved with the other horizontal surfaces and the fuselage. To achieve static pitch stability, the change in canard lift coefficient with angle of attack (lift coefficient slope) should be less than that for the main plane.^[28] This can be achieved with a combination of factors, essentially by making the lift slope of the foreplane less than that of the main wing.^[20]

• 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.^[28] A canard airfoil has commonly a greater airfoil camber than the wing.
• Another possibility is to decrease the aspect ratio of the canard,^[29] with again more lift-induced drag and possibly a higher stall angle than the wing.
• Burt Rutan design approach is high aspect ratio canard, higher lift coefficient (the wing loading of the canard is between 1.6 to 2 times the wing one) and a canard airfoil the lift slope of which is non-linear (nearly flat) between 14° and 24°.^[30]
• A stabilisation parameter is the power effect. In case of canard pusher propeller: "the power-induced flow clean up of the wing trailing edge" ^[30] increases the wing lift slope. Conversely, a propeller located ahead of the canard (increasing the lift slope of the canard) has a strong destabilising effect.^[31]

Some design issues :
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 nose-pitching moment caused by the deflection of trailing-edge flaps. Highly-loaded canards do not have sufficient extra lift to balance this moment, so lifting-canard aircraft cannot readily be designed with powerful trailing-edge flaps.^[20]

A danger associated with an insufficiently-loaded canard—ie 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.^[32]

Wright Flyer stability [edit]

The first powered airplane to fly, the Wright Flyer, a lifting-canard (althouh conceived as a control-canard,^[33] was "highly unstable" and barely controllable.^[34] Following the first flight, the Wright Flyers had some ballast added to the nose to move the center of gravity forward and reduce pitch instability. However the complex stability basics of a canard configuration were not understood by the Wright Brothers. F.E.C. Culick stated, "The backward state of the general theory and understanding of flight mechanics hindered them ... Indeed, the most serious gap in their knowledge was probably the basic reason for their unwitting mistake in selecting their canard configuration".^[35]

Examples of canard aircraft [edit]

Some aircraft that have employed this configuration are listed below. Date is for year of first flight.

Early canards

• 1902 Wright Glider
• Wright Flyer, 1903
• Voisin glider 1904
• Santos-Dumont 14-bis, 1906
• AEA June Bug, 1908
• Fabre Hydravion "Le canard", 1910
• Voisin Canard, 1911
• Focke-Wulf F 19, 1927

Experimental canards

• Beltrame Colibri,^[36] 1938
• Ambrosini SS.4, 1939 pusher configuration fighter prototype
• Miles M.35 Libellula, 1942 tandem wing aircraft designed for high forward visibility
• Miles M.39B Libellula, 1943 tandem wing scale aircraft for a bomber design with high tolerance to centre of gravity changes caused by release of bombload. It would also have been easily converted to jet power.
• Curtiss-Wright XP-55 Ascender, 1943 prototype high performance fighter
• Kyūshū J7W1 Shinden, 1945
• MiG-8 Utka, 1945
• Lockspeiser LDA-01, 1971 - low-cost utility transport concept
• Scaled Composites ARES, 1990

Ultralights/microlights

• Aviafiber Canard 2FL, 1977
• Eipper Lotus Microlight, 1982^[37]
• E-Go project, 2007

Human powered

• MacCready Gossamer Condor, 1977 - pusher design
• MacCready Gossamer Albatross, 1979 - pusher

General aviation and homebuilt canards

• Rutan VariViggen, 1972
• Rutan VariEze, 1975
• Rutan Long-EZ, 1979
• Rutan Defiant, 1978
• Gyroflug Speed Canard, 1980
• Rutan Amsoil Racer, 1981
• Rutan Solitaire, 1982
• Rutan Voyager, 1983
• Cozy MK IV
• Velocity SE
• Velocity XL
• Berkut 360
• Steve Wright Stagger-Ez
• Freedom Aviation Phoenix
• Chudzik CC-1, 1987^[38]
  • Junqua Ibis, 1991

Executive aircraft canards

• OMAC Laser 300, 1981
• Avtek 400, 1984
• Beech Starship, 1986
• AASI Jetcruzer, 1991

Military jet canards

In some cases the foreplane acts as a control-canard during normal flight and as a close-coupled type at high angles of attack.

• Atlas Cheetah
• Chengdu J-9
• Chengdu J-10
• Chengdu J-20^[39]
• Eurofighter Typhoon
• IAI Lavi
• Dassault Rafale
• Lockheed L-133, design submitted in 1942 for jet fighter, not accepted
• North American SM-64 Navaho cruise missile
• North American X-10
• Novi Avion
• Sukhoi T-4
• North American XB-70 Valkyrie - prototype for Mach 3 bomber project. Used for research after the bomber was cancelled.
• Qaher-313 - Iranian fighter
• Rockwell-MBB X-31
• Saab 37 Viggen, lifting and close-coupled canard
• Saab JAS 39 Gripen

Aircraft with a canard foreplane [edit]

Three surface aircraft

• Piaggio P.180 Avanti, executive
• Grumman X-29A, canard, forward-swept wing, control aft surfaces^[40]
• McDonnell Douglas F-15 STOL/MTD (1989) - technology demonstrator
• Sukhoi Su-30 MKI, military
• Sukhoi Su-33
• Sukhoi Su-34
• Sukhoi Su-27(27M variant)
• Sukhoi Su-37
• Sukhoi Su-47

Tailless (delta wing) with a small canard

• IAI Kfir C2 model, 1974
• Dassault Mirage III, late variant NG model, 1981
• Tupolev Tu-144 Civil airliner

Tailless ultralight

• Pterodactyl Ascender, variant with a control canard

See also [edit]

• Canard Rotor/Wing
• Wing configuration
• Tandem wing
• Three-surface aircraft

References [edit]

Further reading [edit]

• J Gambu & J Perard: Saab 37 Viggen, Aviation Magazine International,602, Jan 1973, pp 29–40
• Andy Lennon, Canard : a revolution in flight, aviation Publishers, 1984
• B.R.A. Burns : Were the Wrights Right ?, Air International, december 1983
• B.R.A. Burns : "Canards: Design with Care". Flight International, 23 February 1985, pp 19–21
• Daniel P. Raymer (1989). Aircraft Design: A Conceptual Approach. American Institute of Aeronautics and Astronautics, Inc., Washington, DC. ISBN 0-930403-51-7. 
• R Wilkinson (2001). Aircraft Structures and Systems (2nd edition ed.). MechAero Publishing. 
• Vera Foster Rollo, Burt Rutan Reinventing the Airplane, Maryland Historical Press, 1991
• Abzug - Larrabee, Airplane Stability and Control, Cambridge University Press, 2002.
• Neblett, Metheny and Leifsson; Canards, Virginia Tech, (2003)

External links [edit]

Wikimedia Commons has media related to: Canard Aircraft

• Desktop Aero - A Summary of Canard Advantages and Disadvantages

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