About Canard Airplanes: Aerodynamics, Advantages, and Examples
Traditional Airplanes: Fuselage, Wings, Empennage
The traditional airplane has three main sections. The fuselage is the body of the aircraft, where passengers sit or cargo is loaded. The cockpit is enclosed at the front of this section, and on single-engine aircraft, the powerplant and propeller is generally mounted at the front of the fuselage.
The wings are another large component of an aircraft, usually mounted in the forward third of the fuselage. The wings can be mounted above, below, or in the middle of the fuselage, depending on the aircraft. The wingspan of the aircraft can be as long as the fuselage, or in some cases, longer. The wings are what generate lift to let the aircraft become airborne.
The final major section of an aircraft is called the empennage, or tail. This section is made up of the horizontal stabilizer, the elevators or stabilator, the vertical stabilizer, and the rudder. This section of the aircraft gives the pilot control over the pitch attitude of the aircraft, as well as control over the yawing motion of the aircraft.
Although these are the traditional large elements of an aircraft, some airplanes completely forego traditional design and use other concepts to provide different flight characteristics. One feature sometimes employed on these strange aircraft is called a canard. These canard airplanes create interesting flight factors.
What is a Canard?
A canard is an aircraft design which places the large main wing behind the smaller horizontal stabilizer. This results in a triangular shape of the aircraft, similar to a duck in flight, which is where the term canard originated (the word canard is french for duck). Many fighter jets use this design because of the increased speed and maneuverability it affords. The term canard can refer to both the design of the airplane, as well as the small forward flight surface that serves as the horizontal stabilizer.
Why use a Canard design?
On a traditional aircraft, which places the horizontal stabilizer behind the wing, several aerodynamic forces are at play. The wing generates lift ahead of the center of gravity of the airplane, creating a “pitching moment.” This pitching moment is where the nose of the aircraft wants to rise, due to the force of lift being applied ahead of the center of gravity. (It may be helpful to imagine a see-saw or fulcrum, with the center of gravity being the balance point and the force of lift pushing up on the left side). The horizontal stabilizer is mounted at the rear of the aircraft, and is actually an upside-down wing; this produces downward lift and balances the pitching moment from the wing, allowing the aircraft to generate lift without nosing-up.
On a canard airplane, the wing is at the rear of the fuselage, behind the center of gravity. This will make the aircraft want to pitch nose-down as lift is generated. To counteract this effect, the canard surface is placed ahead of the center of gravity, producing lift of its own to “cancel out” the pitching moment. This means that the canard aircraft has two surfaces both producing lift, while the traditional design has a main wing producing lift and the horizontal stabilizer producing “negative” or downward lift. Because the canard aircraft has two surfaces generating lift instead of a wing generating lift and a tail generating downforce, the canard airplane can be fitted with a smaller main wing. This reduction in the size of the wing results in a reduction in drag, allowing the aircraft to be faster.
Examples of Canard Airplanes
Many famous airplanes have used a canard design. Perhaps the most well-known canard airplane was the Wright Flyer: the first powered airplane featured a prominent cloth canard that controlled the pitch of the aircraft.
Canards have appeared in all aspects of flight. the Rutan-designed VariEze general aviation airplane features a canard, as does the Russian Sukhoi SU-47 jet fighter. The Piaggio P180 Avanti is a corporate transport plane that features a canard design. The Tupolev TU-144 is a Russian canard airplane that was designed as a supersonic passenger transport. Canards have been used with limited success in aviation, and only the future will tell if the canard design will emerge as a dominant feature on aircraft to come.