In aeronautics, canard (French for duck) is an airframe configuration of fixed-wing aircraft in which the tailplane is ahead of the main lifting surfaces, rather than behind them as in conventional aircraft, or when there is an additional small set of wings in front of the main lifting surface. The earliest models, such as the Wright Flyer, the world's first airplane, and the Santos-Dumont 14-bis, were seen by observers to resemble a flying duck — hence the name.
The term "canard" has also come to mean any horizontal airfoil mounted in front of the main wing, whether moving or not.
Canard aircraft characteristics
Canard foreplanes act in a similar way to conventional tailplane and elevators, but due to swap in position about the centre of gravity control surface actions have the opposite effect.
- A canard arrangement produces more lift than a conventional set-up when total lift produced is considered. During manoeuvres the canard control surfaces mirror those of the main wing adding to the lift to climb and decreasing the lift to descend. This means that the aircraft can move tighter and faster than with a conventional set-up.
- Because the canard generates upward lift, unlike with a tail plane which produces downward or negative lift, there is a reduction in the lift required from the main wing. This reduction in the required lift generation by the wing to over come the weight of the aircraft a reduction in lift-induced drag by the wing. As well as removal of the negative lift generated by the tailplane and the associated lift-induced drag. Overall drag and lift requirements of the aircraft is reduced.
- The canard is, sometimes, designed to stall prior to the main wing. This means that once the canard stalls, the nose tends to pitch down, thus reducing the angle of attack of the main wing. However, that is not to say that the main wing cannot stall: a vertical gust that causes a sufficiently high angle of attack on the main wing will cause both the canard and the main wing to stall.
- The wing root operates in the downwash from the canard surface, which reduces its efficiency, although the effect of the downwash does not cause as large of a problem as the tailplane would experience in a conventional set-up.
- The wing tips operate in the upwash from the canard surface, which increases the angle of attack on the tips and promotes premature separation of the air flowing over the wing tip. This premature separation at one tip or the other would promote wing-drop at the approach to the stall, leading to a spin. This must be avoided by precautions in the design of the wing, and may require extra weight in the wing structure outboard of the wing root.
- Because the canard must be designed to stall before the main wing, the main wing never stalls and so never achieves its maximum lift coefficient. This may require a larger wing to provide extra wing area in order for the airplane to achieve the desired takeoff and landing distance performance.
- It is often difficult to apply flaps to the wing in a canard design. Deploying flaps causes a large nose-down pitching moment, but in a conventional aeroplane this effect is considerably reduced by the increased downwash on the tailplane which produces a restoring nose-up pitching moment. With a canard design, there is no tailplane to alleviate this effect. The Beechcraft Starship attempted to overcome this problem with a swing-wing canard surface which swept forwards to counteract the effect of deploying flaps, but usually, many canard designs have no flaps at all.
- In order to achieve longitudinal stability, most canard designs feature a small canard surface operating at a high lift coefficient (CL), while the main wing, although much larger, operates at a much smaller CL and never achieves its full lift potential. Because the maximum lift potential of the wing is typically unavailable, and flaps are absent or difficult to use, takeoff and landing distances and speeds are often higher than for similar conventional aircraft.
- In the case of an pusher propeller, the propeller operates in the wake of the canard, fuselage, wing and landing gear. Also, the propeller diameter is often smaller than optimum, because of ground clearance considerations at rotation. A smaller propeller operating in a large wake will result in reduced propulsive efficiency.
Although some of the advantages and disadvantages above apply to all situation a few of the disadvantages can be, and have been used in the design of high performance military aircraft were aerodynamic instability can allow for a large improvement in the maneuverability of the aircraft.
Though in the civil aviation industry the disadvantages are seen to far outweigh the advantages and few canard design civil aircraft have been successful though with exception of a range of light aircraft produced by Burt Rutan.
Examples of canard aircraft
Aircraft that have successfully employed this configuration include:
- AEA Silver Dart
- Atlas Cheetah
- B-1 Lancer (small canards help negotiate low-level flying)
- Beech Starship
- Berkut 360
- Chengdu J-9
- Chengdu J-10
- Cozy MK IV
- Curtiss-Wright CW-24B
- Curtiss-Wright XP-55 Ascender
- Dassault Rafale
- Eurofighter Typhoon
- Freedom Aviation Phoenix
- Grumman X-29A
- IAI Kfir
- IAI Lavi
- Kyūshū J7W1 Shinden
- McDonnell Douglas (now Boeing) F-15 S/MTD
- MiG-8 Utka
- Miles Libellula
- North American SM-64 Navaho
- North American X-10
- Peterson 260SE (a Cessna 182 with an added canard for STOL operations)
- Piaggio P180 Avanti (3 surfaces aircraft with flapped canard for pitch trim)
- Pterodactyl Ascender
- Rockwell-MBB X-31
- Rutan Defiant
- Rutan Long-EZ
- Rutan Quickie (more a tandem than a canard)
- Rutan VariEze
- Rutan VariViggen
- Rutan Voyager
- Santos-Dumont 14-bis
- Saab Viggen
- Saab Gripen
- Steve Wright Stagger-Ez
- Sukhoi Su-30 MKI
- Sukhoi Su-33
- Sukhoi Su-34
- Sukhoi Su-35
- Sukhoi Su-37
- Sukhoi Su-47
- Sukhoi T-4
- Tupolev Tu-144
- Velocity SE
- Velocity XL
- Wright Flyer
- XB-70 Valkyrie
Chengdu J-10 fighter aircraft, on final approach to Chengdu Airport, China
Grumman X-29, an experimental aircraft for forward swept wing research
- Rockwell MBB X31.jpg
The Rockwell-MBB X-31 Enhanced Fighter Maneuverability Demonstrator Aircraft
Canards (just behind the flight deck) on the XB-70 Valkyrie experimental bomber aircraft
- P-180 Canard.JPG
Closeup of a Piaggio P180 Avanti's canards
- Mikoyan-Gurevich MiG-8.JPG
Mikoyan-Gurevich MiG-8, 1945
The Beechcraft Starship Executive Transport
Rutan Long-EZ, with canard just ahead of the cockpit
A Pterodactyl Ascender II+2 showing its canard control surface
- Aircraft Structures and Systems(Second Edition): R Wilkinson: MechAero Publishing(2001)
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It uses material from the Wikipedia article "Canard (aeronautics)".