A three-surface aircraft or sometimes three-lifting-surface aircraft has a foreplane, a central wing and a tailplane. The central wing surface always provides lift and is usually the largest, while the functions of the fore and aft planes may vary between types and may include lift, control and/or stability.
In civil aircraft the three surface configuration may be used to give safe stalling characteristics and short takeoff and landing (STOL) performance. It is also claimed to allow minimizing the total wing surface area, reducing the accompanying skin drag. In combat aircraft this configuration may also be used to enhance maneuverability both before and beyond the stall, often in conjunction with vectored thrust.
An early designation used in 1911 was "Three plane system".The Fernic designs of the 1920s were referred to as "tandem". While there are indeed two lifting wing surfaces in tandem, the tailplane forms a third horizontal surface.
During the pioneer years of aviation a number of aircraft were flown with both fore and aft auxiliary surfaces. The issue of horizontal stability was poorly understood and typically pitch control was on the front surface with the rear surface also lifting, leading to instability problems. The Kress Drachenflieger of 1901 and Dufaux triplane of 1908 had insufficient power to take off. More successful types included the Voisin-Farman I (1907) and Curtiss No. 1 (1909). The Wright Brothers too experimented on the basic Flyer design in an effort to obtain both controllability and stability, flying it at various times in first canard, then three surface and finally conventional configurations.By the outbreak of the First World War in 1914, the rear surface had become the conventional configuration and few three surface types would be flown for many years. The Fokker V.8 of 1917 and Caproni Ca.60 Noviplano of 1921 were both failures.
In 1920s George Fernic developed the idea of two lifting surfaces in tandem, together with a conventional tailplane. The small foreplane was highly loaded and as the angle of attack increased it was designed to stall first, causing the nose to drop and allowing the aircraft to recover safely without stalling the main wing. This "soft" stall provides a level of safety in the stall which is not usually present in conventional designs. The Fernic T-9, a three-surface monoplane, flew in 1929. Fernic was killed in an accident while flying its successor the FT-10 Cruisaire.
It is possible to achieve such a soft stall with a pure canard design, but it is then difficult to control the pitching and oscillations can develop as the foreplane repeatedly lifts the nose, stalls and recovers. Also, care must be taken in the design that the turbulent wake from the stalled foreplane does not in itself disturb the airflow over the main wing sufficiently to cause significant loss of lift and cancel out the nose-down pitching moment. In the three-surface design the third, tail surface does not stall and provides better controllability.[ citation needed ]
In the 1950s James Robertson developed his experimental Skyshark. This was a broadly conventional design but with a variety of features, including a small canard foreplane, intended to give not only a safe stall but good Short takeoff and landing (STOL) performance. The foreplane allowed STOL performance to be achieved without the high angles of attack and accompanying dangers of stalling required by conventional STOL designs. The aircraft was evaluated by the US Army.Robertson's system was commercialised as the Wren 460, a modified Cessna light aircraft. This in turn was later licensed and produced during the 1980s as the Peterson 260SE and with the foreplane modification only as the 230SE. In 2006 a ruggedised variant, the Peterson Katmai, entered production. A broadly similar approach is taken by the 1988 Eagle-XTS and its derivatives, the Eagle 150 series.
Around 1979, military jet designers began studying three-surface configurations as a way to provide enhanced manoeuvrability and control, especially at low speeds and high angles of attack such as during takeoff and combat.In the United States the experimental Grumman X-29 flew in 1984 and a modified McDonnell Douglas F-15, the F-15 STOL/MTD, in 1988 but these designs were not followed up. In the Soviet Union a Sukhoi Su-27 modified with canard foreplanes flew in 1985 and derivatives of this design became the only military types to enter production.
Also in 1979, Piaggio began design studies on a three-surface civil twin turboprop which, in collaboration with Learjet, would emerge as the Piaggio P.180 Avanti. This type first flew in 1986 and entered service in 1990, with production continuing today. In the Avanti, the three-surface configuration is claimed to significantly reduce wing size, weight and drag compared to the conventional equivalent.
Two experimental aircraft adopting this configuration were subsequently built by Scaled Composites under the lead of Burt Rutan and flown in 1988. The Triumph was a twin-turbofan very light jet aircraft designed for Beechcraft. Flight testing validated the targeted performance range. 5,000 km (3,100 mi) without payload of 334.44 km/h (207.81 mph) set in 2014.The Catbird was a single-engined propeller-driven aircraft, envisioned by Rutan as a replacement for the Beechcraft Bonanza. It holds the world record for speed over a closed circuit of
Some advanced jet aircraft have a three-surface configuration, often in conjunction with thrust vectoring. This is typically intended to enhance control and manoeuvrability, especially at very high angles of attack beyond the stall point of the main wing. Some advanced combat manoeuvres such as Pugachev's Cobra and the Kulbit were first performed on Sukhoi three-surface aircraft.
The experimental Grumman X-29 was of basic "tail-first" canard configuration, with unusual forward-swept wings and strakes extending rearwards from the main wing roots. Movable flaps at the ends of the strakes effectively made it a three-surface design.The X-29 demonstrated exceptional high-angle of attack manoeuvrability.
A more straightforward three-surface design is seen in several variants of the otherwise conventional Sukhoi Su-27. Following the successful addition of canard foreplanes to a development aircraft, these were incorporated into a number of subsequent production variants including the naval Su-33 (Su-27K), some Su-30s, the Su-35 and the Su-37. The Chinese Shenyang J-15 also inherits the configuration of the Su-33.
The McDonnell Douglas F-15 STOL/MTD was an F-15 airframe modified with canard foreplanes and thrust vectoring, designed to demonstrate these technologies for both STOL performance and high manoeuvrability.
The three-surface configuration is claimed to reduce total aerodynamic surface area compared to the conventional and canard configurations,thus enabling drag and weight reductions.
On most aircraft, the wing centre of pressure moves forward and backward according to flight conditions. If it does not align with the centre of gravity, a corrective or trim force must be applied to prevent the aircraft pitching and thus to maintain equilibrium.
On a conventional aircraft this pitch trim force is applied by a tailplane. On many modern designs, the wing centre of pressure is normally aft of the centre of gravity, so the tailplane must exert a downward force.Any such negative lift generated by the tail must be compensated by additional lift from the main wing, thus increasing wing area, drag, and weight requirements.
On a three-surface aircraft, the pitch trim forces can be shared, as needed in flight, between the foreplane and tailplane. Equilibrium can be achieved with lift from the foreplane rather than downforce from the tailplane. Both effects, the reduced downforce and the extra lifting force, reduce the load on the main wing.
The Piaggio P.180 Avanti has flaps on both its forward wing and main wing. Both flaps deploy in concert to maintain pitch neutrality for take-off and landing.
On a canard aircraft, to allow natural static pitch stability in normal flight, the foreplane must provide lift. Also, in order for the aircraft to have safe stall characteristics the foreplane must stall before the main wing, pitching the aircraft down and allowing the aircraft to recover. This means that a safety margin must be used on the main wing area so that its maximum lift coefficient and wing loading are never attained in practice. This in turn means that the main wing must be increased in size.
On a three-surface aircraft, the tailplane acts as a conventional horizontal stabiliser. In the stall condition, even if the main wing is stalled the tailplane can provide a pitch-down moment and allow recovery. The wing may thus be used up to its maximum lift coefficient, an advantage that may translate into a reduction of its area and weight.
A lifting foreplane is positioned ahead of the centre of gravity, so its lift moment acts in the same direction as any movement in pitch. If the aircraft is to be naturally stable, the foreplane’s size, lift slope and moment arm must be chosen so that it does not overpower the stabilizing moment provided by the wing and tailplane. Stability constraints thus limit the foreplane’s volume ratio (a measure of its effectiveness in trim and stability terms), which may in turn limit its ability to share pitch trim forces as described above.
The minimum size of the lifting wings of an aircraft is determined by: the weight of the aircraft, the force required to oppose the negative lift produced by the horizontal stabilizer, the targeted take off and landing speeds, and the coefficient of lift of the wings.
Most modern aircraft use trailing edge flaps on the main wing to increase the wings lift coefficient during take off and landing; thus allowing the wing to be smaller than it would otherwise need to be. This may reduce the weight of the wing, and it always reduces the surface area of the wing. The reduction of surface area proportionately reduces skin drag at all speeds.
A drawback of the use of trailing edge flaps is that they produce significant negative pitching moment when in use. In order to balance this pitching moment the horizontal stabilizer must be somewhat larger than it would otherwise be, so that it can produce enough force to balance the negative pitching moment created by the trailing edge flaps. This, in turn, means that the main wing must be somewhat larger than it would otherwise have to be to balance the larger negative lift produced by the larger horizontal stabilizer.
On a canard aircraft the foreplane can provide positive lift at takeoff, reducing some of the down force the rear stabilizer would otherwise have to create. However, the main wing must be large enough to not only lift the aircraft's remaining weight at takeoff but also to provide adequate safety margin to prevent stalling. On a three-surface aircraft, neither of these handicaps is present and the main wing can be reduced in size, so also reducing weight and drag. It is claimed that the total area of all wing surfaces of a three-surface aircraft can be less than that of the equivalent two-surface aircraft, so reducing both weight and drag.
Minimum area in cruise can be further reduced through the use of conventional high-lift devices such as flaps, allowing a three-surface design to have minimum surface area at all points in the flight envelope.
Examples of reduced-area three-surface aircraft include the Piaggio P.180 Avanti, and the Scaled Composites Triumph and Catbird. These aircraft were designed to expose a minimum of total surface area to the slipstream;[ citation needed ] thus reducing surface drag for speed and fuel efficiency. Several reviews compare the Avanti's top speed and service ceiling to that of lower-end jet aircraft, and report significantly better fuel efficiency at cruise speed. Piaggio attributes this performance in part to the layout of the aircraft, claiming a 34% reduction in total wing area compared to a conventional layout.
|Aceair AERIKS 200||Switzerland||Propeller||Private||2002||Prototype||Designed as a homebuild kit.|
|Curtiss/AEA June Bug||US||Propeller||Experimental||1908||Prototype|
|Caproni Ca.60 Noviplano||Italy||Propeller||Transport||1921||Prototype||Three triplane stacks, making nine wings in all. Flying boat.|
|Curtiss No. 1||US||Propeller||Experimental||1909||Prototype||Also known as the Curtiss Gold Bug or Curtiss Golden Flyer.|
|de la Farge Pulga||Argentina||Propeller||Private||circa 1990||Modified Flying Flea|
|Dufaux||Switzerland||Propeller||Experimental||1908||Prototype||First Swiss aircraft to fly.|
|Eagle Aircraft Eagle 150||Australia||Propeller||Private||1997|
|Farman three wing monoplane||France||Propeller||Experimental||1908||Prototype|
|Grumman X-29||US||Jet||Experimental||1984||Prototype||Forward-swept wing with canard foreplane and tailboom flaps.|
|Kress Drachenflieger||Austria-Hungary||Propeller||Experimental||1901||Prototype||Failed to fly: engine lacked sufficient power to take off.|
|McDonnell Douglas F-15 STOL/MTD||US||Jet||Experimental||1988||Prototype||technology demonstrator of enhanced maneuverability including use of thrust vectoring|
|Mikoyan-Gurevich Ye-8||Soviet Union||Jet||Experimental||1962||Prototype|
|NPO Molniya 1||Russia||Transport||1992|
|Peterson 260SE and 230SE||US||Propeller||Private||1986|
|Piaggio P.180 Avanti||Italy||Propeller||Transport||1986||Production|
|Rutan Scaled Model 120 'Predator'||US||Propeller||Experimental||1984||Prototype|
|Scaled Composites ATTT (model 133)||US||Propeller||Experimental||1987||Prototype|
|Scaled Composites Triumph (model 143)||US||Jet||Experimental||1988||Prototype|
|Scaled Composites Catbird (model 181)||US||Propeller||Experimental||1988||Prototype|
|Shenyang J-15||China||Jet||High-manoeuvrability combat||2009|
|Short No.1 biplane||UK||Propeller||Experimental||1910||Prototype||Not flown.|
|Sukhoi Su-27M||Soviet Union||Jet||High-manoeuvrability combat||Some examples fitted with a foreplane in addition to the standard tailplane.|
|Sukhoi Su-30 MKI||India||Jet||Fighter||1989||Production||License-built variant of the Sukhoi Su-30|
|Sukhoi Su-33||Soviet Union||Jet||Fighter||1987||Production|
|Sukhoi Su-47||Russia||Jet||Experimental||1997||Prototype||Main wing is forward-swept.|
|Wright Model A (Modified)||US||Propeller||Experimental||1909|
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 gyroplanes. Not all fixed-wing aircraft have tailplanes. Canards, tailless and flying wing aircraft have no separate tailplane, while in V-tail aircraft the vertical stabiliser, rudder, and the tail-plane and elevator are combined to form two diagonal surfaces in a V layout.
A delta wing is a wing shaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letter delta (Δ).
Aircraft flight control surfaces are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude.
The Piaggio P.180 Avanti is an Italian executive transport aircraft with twin turboprop engines mounted in pusher configuration. It seats up to nine people in a pressurized cabin and may be flown by one or two pilots. The design is of three-surface configuration, having both a small forward wing and a conventional tailplane, as well as its main wing, with the main wing spars passing behind the passenger cabin area.
Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's pitch, and therefore the angle of attack and the lift of the wing. The elevators are usually hinged to the tailplane or horizontal stabilizer. They may be the only pitch control surface present, and are sometimes located at the front of the aircraft or integrated into a rear "all-moving tailplane", also called a slab elevator or stabilator.
A stabilator, more frequently all-moving tail or all-flying tail, is a fully movable aircraft stabilizer. It serves the usual functions of longitudinal stability, control and stick force requirements otherwise performed by the separate parts of a conventional horizontal stabilizer and elevator. Apart from a higher efficiency at high Mach number, it is a useful device for changing the aircraft balance within wide limits, and for mastering the stick forces.
In an aircraft with a pusher configuration, the propeller(s) are mounted behind their respective engine(s). According to British aviation author Bill Gunston, a "pusher propeller" is one mounted behind the engine, so that the drive shaft is in compression.
The Rutan Quickie is a lightweight single-seat taildragger aircraft of composite construction, configured with tandem wings.
The empennage, also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow. The term derives from the French language word empenner which means "to feather an arrow". Most aircraft feature an empennage incorporating vertical and horizontal stabilising surfaces which stabilise the flight dynamics of yaw and pitch, as well as housing control surfaces.
Flight mechanics are relevant to fixed wing and rotary wing (helicopters) aircraft. An aeroplane, is defined in ICAO Document 9110 as, "a power-driven heavier than air aircraft, deriving its lift chiefly from aerodynamic reactions on surface which remain fixed under given conditions of flight".
Mach tuck is an aerodynamic effect whereby the nose of an aircraft tends to pitch downward as the airflow around the wing reaches supersonic speeds. This diving tendency is also known as "tuck under". The aircraft will first experience this effect at significantly below Mach 1.
An aircraft stabilizer is an aerodynamic surface, typically including one or more movable control surfaces, that provides longitudinal (pitch) and/or directional (yaw) stability and control. A stabilizer can feature a fixed or adjustable structure on which any movable control surfaces are hinged, or it can itself be a fully movable surface such as a stabilator. Depending on the context, "stabilizer" may sometimes describe only the front part of the overall surface.
A rotorcraft or rotary-wing aircraft is a heavier-than-air flying machine that generates lift using rotary wings or rotor blades, which revolve around a mast. Several rotor blades mounted on a single mast are referred to as a rotor. The International Civil Aviation Organization (ICAO) defines a rotorcraft as "supported in flight by the reactions of the air on one or more rotors".
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.
A tailless aircraft has no tail assembly and no other horizontal surface besides its main wing. The aerodynamic control and stabilisation functions in both pitch and roll are incorporated into the main wing. A tailless type may still have a conventional vertical fin and rudder.
In flight dynamics, longitudinal static stability is the stability of an aircraft in the longitudinal, or pitching, plane under steady flight conditions. This characteristic is important in determining whether a human pilot will be able to control the aircraft in the pitching plane without requiring excessive attention or excessive strength.
Supermaneuverability is the capability of fighter aircraft to execute tactical maneuvers that are not possible with purely aerodynamic mechanisms. Such maneuvers can use controlled side-slipping and angles of attack beyond maximum lift.
The wing configuration of a fixed-wing aircraft is its arrangement of lifting and related surfaces.
The Fernic T-9, also called the Fernic F.T.9, is an early three-surface aircraft, having two lifting wings in tandem as well as a conventional tailplane. It was a light twin-engined craft intended for flight distance record setting.
The Rutan Model 72 Grizzly is a tandem-wing STOL research aircraft designed by Burt Rutan, now preserved at the EAA AirVenture Museum, Oshkosh. The aircraft exhibited excellent Short Take-Off and Landing (STOL) capabilities, proving that this is also possible with a Rutan-typical canard design.
When the controls are set so that the resultant forces and the moments about the center of gravity are all zero, the aircraft is said to be in trim, which simply means static equilibrium