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QAC Quickie Q2 A tandem wing is a
wing configuration The wing configuration of a fixed-wing aircraft (including both glider (aircraft), gliders and powered aeroplanes) is its arrangement of lifting and related surfaces. Aircraft designs are often classified by their wing configuration. For examp ...
in which a flying craft or animal has two or more sets of
wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is e ...
s set one behind another. All the wings contribute to lift. The tandem wing is distinct from the
biplane A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While a ...
in which the wings are stacked one above another, or from the canard or "tail-first" configuration where the forward surface is much smaller and does not contribute significantly to the overall lift. In aviation, tandem wings have long been experimented with, but few designs have ever been put into production. Tandem wings in nature occur only in insects and flying fish, although in the past there have been tandem-wing flying dinosaurs.


Design principles

A tandem wing
configuration Configuration or configurations may refer to: Computing * Computer configuration or system configuration * Configuration file, a software file used to configure the initial settings for a computer program * Configurator, also known as choice bo ...
has two main
wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is e ...
planes, with one located forward and the other to the rear. The difference is greater than the wing chord, so there is a clear gap between them and the aircraft centre of gravity (CG) lies between the wings.Bottomley (1977) Compared to the conventional layout, where the tailplane exerts little or no vertical force in cruising flight, both tandem wings contribute substantially to lift. The basic tandem configuration uses wings which are equal in size and in line with each other. Examples have flown successfully, such as the Peyret glider of 1922. However the rear wing is usually placed either above or below the fore wing, in order to avoid its turbulent wake. One wing is often made a little smaller than the other, according to the details of the design. Indeed, there are no clear dividing lines between the conventional vs. tandem, or the tandem vs. canard configurations.Miles (1944) The high-mounted fore wing and low-mounted aft wing arrangement is also sometimes treated as an extreme staggered biplane and referred to as the Nénandovich biplane. Interference effects between the two wings can make a tandem layout less efficient in cruise than the equivalent conventional design, however examples such as the Scaled Composites Proteus are capable of exceptional efficiency. The tandem layout creates a "slot effect" in which the front wing deflects air downwards over the rear wing, reducing the angle of attack (AoA) of the rear. At high aircraft AoA, this causes the front wing to stall first, allowing safer flight at low speeds than the equivalent conventional layout. It also offers good STOL performance. Tandem wings have also been used on ground-effect vehicles, where the front wing is used to direct air downwards beneath the rear wing to create a lifting air cushion.


Stability, control and trim

In a tandem wing the lift forces on the two wings are separated longitudinally, allowing them to act together to achieve stability, control and trim. The mechanisms of stability and control for a tandem wing are similar to those for the tail-first or canard layout; the distinction is mainly in the relative size of the forward surface. However, the larger trim forces available compared to a smaller tailplane or foreplane mean that a tandem design can offer a greater range of trim conditions, and hence of
centre of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...
(CG) location than other layouts, which can offer a practical solution where weight loadings and distributions may vary during operations. However a wide CG range leads to other problems, including a compatible undercarriage layout and safe stalling characteristics.


Joined wing

The joined wing is a tandem-wing layout in which the front wing sweeps back and/or the rear wing sweeps forwards such that they join at or near the tips to form a continuous surface in a hollow diamond or triangle shape. The joined wing is also an example of a closed wing. The Ligeti Stratos is a rare example to have flown.


Structural design

In a conventional layout, the moment arm of the outer section's lifting load is large, and this stresses the root section. However, in a tandem design each wing is smaller and the outer load is absent. This allows the wing structure to be lighter overall. In a conventional design, the fuselage is supported only in one place, with the fore and aft fuselage sections cantilevered out from it. This creates significant bending stresses. A tandem wing supports the same fuselage in two places, reducing the bending stresses. However the torsion stresses on the centre section between the wings are greater. Because it is more compact, the tandem-wing structure is stiffer overall, meaning that less allowance needs to be made for bending, and a smaller safety margin in stress levels is possible, allowing yet further weight and cost reduction.


History


Pioneers

The tandem wing configuration predates successful manned flight. As far back as the fifteenth century, Tito Livio Burraitni experimented with a tandem-wing model. Four sets of wings in tandem variously provided lift and propulsion, and Burraitni's cat became the first aeronaut to fly in a tandem design. Having also flown simpler fore-and-aft tandem models of up to in span, in 1903 Samuel Pierpont Langley built a full-size tandem-wing monoplane, the
Aerodrome An aerodrome (Commonwealth English) or airdrome (American English) is a location from which aircraft flight operations take place, regardless of whether they involve air cargo, passengers, or neither, and regardless of whether it is for publi ...
, and launched it from the roof of a houseboat. It failed to fly. After his death the
Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Found ...
sought to prove that he had flown in the weeks before the Wright brothers, and employed successful planemaker Glenn Curtiss to secretly modify the aerodrome until it could fly, as "proof" that it had flown in 1903. Curtiss added floats and made other improvements, enabling it to undertake short hops as a true waterplane in 1914. The ruse was eventually exposed, yet the Smithsonian still sought to claim that the 1902 version had been "capable of flight". It would be many more years before they recanted. Several pioneers had long made successful gliders. In 1905 John J. Montgomery flew a tandem monoplane glider, confirming that the aerodynamic principle was sound. Powered flight followed two years later. In 1906
Louis Blériot Louis Charles Joseph Blériot ( , also , ; 1 July 1872 – 1 August 1936) was a French aviator, inventor, and engineer. He developed the first practical headlamp for cars and established a profitable business manufacturing them, using much of th ...
built his third aeroplane with tandem elliptical closed wings, later modifying it as his type IV with the fore wing converted into a conventional biplane. But it was not until the next year that his type VI, a wheeled tandem monoplane of broadly similar configuration to Langley's Aerodrome, became the first tandem-wing aeroplane to fly. Between 1907 and 1911, the aerodynamics studies of
Gustave Eiffel Alexandre Gustave Eiffel (born Bonickhausen dit Eiffel; ; ; 15 December 1832 – 27 December 1923) was a French civil engineer. A graduate of École Centrale des Arts et Manufactures, he made his name with various bridges for the French railway ...
showed that the tandem layout was inherently less aerodynamically efficient that the more conventional.Poulsen (1943) Overlapping with Eiffel's work, Stefan Driezewicki developed and wind-tunnel tested an inherently stable tandem-wing design. He then built and successfully flew a full-sized example at the end of 1912.


Interwar period

Experimental tandem-wing aircraft continued to be built after World War I. The
Caproni Ca.60 The Caproni Ca.60 Transaereo, often referred to as the Noviplano (nine-wing) or Capronissimo, was the prototype of a large nine-wing flying boat intended to become a 100-passenger transatlantic airliner. It featured eight engines and three sets ...
prototype flying boat comprised a long passenger-carrying hull to which were attached in tandem three stacks of triplane wings from the successful Ca.4 line of heavy bombers and airliners, earning it the nickname "Capronissimo". However it broke up on its first attempted takeoff in 1921. The first fully controllable tandem-wing type was the French-built Peyret tandem glider, which won the first British gliding competition in 1922. Peyret's novel control system comprised full-span trailing edge surfaces on all four wings. These operated in pairs on each side as ailerons, in pairs fore and aft as elevators, and synchronously as flaps for low-speed flight. The system proved effective and, despite the glider being less efficient than the conventional high-aspect-ratio entries, it proved more controllable and manoeuvrable. This enabled the pilot M. Maneyrol to remain in updraughts for longer than the others. Although Peyret continued to develop the design, in both gliders and powered types, they remained a curiosity. The SFCA continued the work of Peyret after he died, adopting his control system. Their Taupin first flew in 1933. Its design proved practical and some 52 examples were produced. Meanwhile Henri Mignet was taking a very different approach to flight control. Intended for amateurs to build at home, his
Pou-du-Ciel The Flying Flea (french: Pou du Ciel, lit=Louse of the Sky) is a large family of light homebuilt aircraft first flown in 1933. The odd name comes from the French nickname for the Ford Model T automobile: ''Pou de la Route'', or "Louse of the R ...
(flying flea) had a novel two-axis control system to make it easy to fly. No ailerons were needed because when the rudder was operated, yaw-roll coupling ensured that the plane banked into a turn. For pitch control the whole front wing tilted to act as a canard elevator. Introduced at much the same time as the Taupin, it became a craze, hundreds were built and variations developed in many countries. However stability issues relating to the variable front wing could lead to lethal crashes in the hands of the novice pilot, and the type eventually fell out of favour.


World War II period

During the late 1930s, Maurice Delanne was working on tandem-wing designs. He proposed a fighter, the Delanne 10, featuring a gulled forward wing and twin fins on the tips of the low-set and slightly shorter-span rear wing. He first built two examples of a smaller aerodynamic test aircraft, the
Delanne 20-T The Delanne 20-T was a French tandem wing aircraft designed as an aerodynamic model for a larger fighter aircraft. It was tested during 1939. Design Though sometimes described as a tourer and at others, incorrectly, as a fighter aircraft, the ...
, which flew in 1938. The Arsenal de l'Aéronautique then constructed a prototype fighter, the Arsenal-Delanne 10. It was completed and test-flown after the German invasion of France, and was then taken to Germany for further testing. Meanwhile Westland Aircraft were considering a modification of the
Lysander Lysander (; grc-gre, Λύσανδρος ; died 395 BC) was a Spartan military and political leader. He destroyed the Athenian fleet at the Battle of Aegospotami in 405 BC, forcing Athens to capitulate and bringing the Peloponnesian War to an en ...
light observation and liaison aircraft, by adding a rear gun turret to give it some protection from attack. The Lysander already had a suitable main wing, so to support the weight of the turret Westland thought of adding a Delanne-type rear wing. By now hostilities had started but France had not yet fallen. Chief Designer W. E. W. "Teddy" Petter and Chief Test Pilot
Harald Penrose Harald Penrose, O.B.E, CEng, Royal Aeronautical Society, F.R.Ae.S, Royal Institution of Naval Architects, A.M.I.N.A (12 April 1904 – 31 August 1996) was the chief test pilot at Westland Aircraft between 1931 and 1953, a naval architect, and a ...
flew to Paris, where Penrose flew one of the 20-Ts and reported favourably on its handling. The tandem Lysander was not completed until 1941, when Penrose began test flights. Although it performed flawlessly – he wrote that "here was a military prototype that needed no alteration" – it was not ordered into production. George Miles saw the tandem Lysander at RAF Boscombe Down and realised its potential as a short-span, short-take-off Naval fighter. The ensuing Miles M.35 Libellula test aircraft differed from the Delanne design in having wings of approximately equal span, but with the rear wing given a longer chord and swept back. Although the design was rejected, it flew well enough to prompt development of the larger M.39B, a subscale test aircraft for the proposed M.39 high-speed bomber to meet Specification B.11/41. This time the fore wing was smaller and mounted low, while the swept rear wing was high-mounted with twin engine nacelles slung beneath. Flying in 1943 it performed well, but the bomber requirement was subsequently cancelled.


Postwar

After WWII, interest returned to the Flying Flea's tilting forewing concept and, with its worst dangers now understood and fixed, designers have continued to develop the idea, typically still for home construction. The Curtiss-Wright X-19 of 1963 marked the entry of the tandem wing configuration into the VTOL arena, as a quadrotor convertiplane, with large tilting proprotors mounted on each wing tip. It proved overly complex and unreliable for the technology of the day. Other tandem approaches such as the Delanne were largely forgotten, until David Lockspeiser conceived of his Land Development Aircraft, a low-cost utility transport. It was to utilise three interchangeable wing component; one each mounted high up for the left and right rear wings, and a third fore wing mounted centrally beneath the nose. His prototype LDA-01 flew in 1971. It proved successful enough to develop for production, but the project ended before it could be modified. The next breakthrough to manufacture came once again in the homebuild market. Up-and-coming maverick designer Burt Rutan was working on a low-powered but highly efficient plane for home construction. The tandem layout offered a low-drag fixed undercarriage installation, by placing the main wheels in housings at the tips of the fore wing and applying anhedral to raise the fuselage high enough for a propeller. The high-mounted rear wing had compensating dihedral. The Quickie first flew in 1977 and the next year won the EAA's Outstanding New Design Award at Oshkosh. It became popular, and several variants subsequently appeared. Rutan set up Scaled Composites and some of the company's later designs were also tandems.


List of tandem-wing aircraft

:''This list is incomplete. Please help by expanding it'' , - , Airbus A³ Vahana , , US , , Propeller , , Private , , 2018 , , Prototype , , 2 , , Tiltwing personal air vehicle. , - , Arsenal-Delanne 10 , , France , , Propeller , , Fighter , , 1940 , , Prototype , , 1 , , , - , Blériot III/IV , , France , , Propeller , , Experimental , , 1906 , , Project , , 1 , , Failed to fly as either the III or IV. , - , Blériot VI , , France , , Propeller , , Experimental , , 1907 , , Prototype , , 1 , , , - ,
Caproni Ca.60 The Caproni Ca.60 Transaereo, often referred to as the Noviplano (nine-wing) or Capronissimo, was the prototype of a large nine-wing flying boat intended to become a 100-passenger transatlantic airliner. It featured eight engines and three sets ...
, , Italy , , Propeller , , Transport , , 1921 , , Prototype , , 1 , , Nine-wing triple-tandem triplane. , - , Curtiss-Wright X-19 , , US , , Propeller , , Experimental , , 1963 , , Prototype , , 2 , , Four-engined tiltrotor
convertiplane A convertiplane is defined by the Fédération Aéronautique Internationale (FAI or World Air Sports Federation) as an aircraft which uses rotor power for vertical takeoff and landing ( VTOL) and converts to fixed-wing lift in normal flight. In th ...
, - ,
Delanne 20-T The Delanne 20-T was a French tandem wing aircraft designed as an aerodynamic model for a larger fighter aircraft. It was tested during 1939. Design Though sometimes described as a tourer and at others, incorrectly, as a fighter aircraft, the ...
, , France , , Propeller , , Experimental , , 1938 , , Prototype , , 2 , , Test plane for the Arsenal-Delanne 10 fighter. , - , Moscow Aviation Institute Sh-Tandem , , USSR , , Prototype , , Attack , , 1937 , , Prototype , , 1 , , Also known as the Grushin Sh-Tandem. MAI-3.Gordon, Yefim and Gunston, Bill; ''Soviet X-Planes'', Midland, 2000. pp.62-3. , - , Langley Aerodrome , , US , , Propeller , , Experimental , , 1902 , , Project , , 1 , , Failed to take off. , - , Ligeti Stratos , , Australia , , Propeller , , Private , , 1985 , , Prototype , , 2 , , Joined wing. (Cited in main text) , - , Lockspeiser LDA-01 , , UK , , Propeller , , Utility , , 1971 , , Prototype , , 1 , , , - ,
Mauboussin Hémiptère The Mauboussin M.40 Hémiptère was an experimental, single seat, single engine light aircraft with unequal span tandem wings, designed in France in the 1930s. Only one was built. Design and development Between 1928 and 1932 Pierre Mauboussi ...
, , France , , Propeller , , Experimental , , 1936 , , Prototype , , 1 , , , - , Mignet Pou-du-Ciel , , France , , Propeller , , Private , , 1933 , , Homebuilt , , , , , - , Miles M.35 Libellula , , UK , , Propeller , , Experimental , , 1942, , Prototype , , 1 , , , - , Miles M.39B Libellula , , UK , , Propeller , , Experimental , , 1943 , , Prototype , , 1 , , , - , Montgomery Aeroplane ''The Santa Clara'' , , US , , Glider , , Experimental , , 1905 , , Prototype , , 1 , , , - , Payen PA-22 , , France , , Propeller , , Experimental , , 1942 , , Prototype , , 1 , , Delta rear wing. Begun prewar. , - , Peyret Tandem , , France , , Glider , , Private , , 1922 , , Prototype , , 1 , , Won the 1922 British Glider Competition. , - , Peyret VI , , France , , Propeller , , Experimental , , 1933 , , Prototype , , 1 , , Forerunner of the SFCA Taupin. , - , Piel CP-10 Pinocchio , , France , , Propeller , , Private , , 1948 , , Prototype , , 1 , , Similar to the
Mignet Pou du Ciel The Flying Flea (french: Pou du Ciel, lit=Louse of the Sky) is a large family of light homebuilt aircraft first flown in 1933. The odd name comes from the French nickname for the Ford Model T automobile: ''Pou de la Route'', or "Louse of the R ...
. , - ,
QAC Quickie Q2 The Quickie Q2 or Q2 is a two-seat version of the unique Rutan Quickie, produced in kit form by the Quickie Aircraft Corporation founded by Tom Jewett and Gene Sheehan. Canadian Garry LeGare was involved in the design. The Q2 is a tandem win ...
series , , US , , Propeller , , Private , , 1980 , , Homebuilt , , , , Derivatives of the Rutan Quickie. , - , Rutan Quickie , , US , , Propeller , , Private , , 1978 , , Homebuilt , , , , , - , Scaled Composites ATTT , , US , , Propeller , , Experimental , , 1986 , , Prototype , , 1 , , , - , Scaled Composites Proteus , , US , , Jet , , Experimental , , 1998 , , Prototype , , 1 , , High-altitude endurance. , - , SFCA Taupin , , France , , Propeller , , Private , , 1936 , , Production , , 53 , , , - , SFCA Lignel 44 , , France , , Propeller , , Private , , 1946 , , Prototype , , 1 , , 4-seat development of the Taupin. , - , Viking Dragonfly , , US , , Propeller , , Private , , 1980 , , Homebuilt , , , , , - , Westland P.12 Lysander Delanne , , UK , , Propeller , , Utility , , 1940 , , Prototype , , 1 , , Modified Lysander to include rear wing and gun turret.


Tandem wings in nature


Insects

Several orders of flying insects employ tandem wings, each with its characteristic
anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having i ...
and flight modes.
Insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s with tandem flapping wings include the Odonata ( dragonflies and
damselflies Damselflies are flying insects of the suborder Zygoptera in the order Odonata. They are similar to dragonflies, which constitute the other odonatan suborder, Anisoptera, but are smaller and have slimmer bodies. Most species fold the wings alo ...
),
Lepidoptera Lepidoptera ( ) is an order of insects that includes butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 percent of the total described speci ...
(
butterflies Butterflies are insects in the macrolepidopteran clade Rhopalocera from the order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The group comprises ...
and
moths Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...
) and some Thysanoptera or Thrips. Odonata species typically have long, thin wings and can synchronise the flapping of fore and aft pairs in various different modes, allowing them to be both fast and highly manoeuvrable. By comparison the Lepidoptera have wider wings which are flapped in synchrony and may even overlap in flight, and are better suited to endurance flying. Thrips are smaller insects and the flying species have relatively stiff wings. Due to their small size, they generate lift via
clap and fling Insects are the only group of invertebrates that have evolved wings and flight. Insects first flew in the Carboniferous, some 350 to 400 million years ago, making them the first animals to evolve flight. Wings may have evolved from appendag ...
flapping rather than the usual leading-edge vortex generation of most insects. Many flying beetles, such as the
ladybird Coccinellidae () is a widespread family of small beetles ranging in size from . They are commonly known as ladybugs in North America and ladybirds in Great Britain. Some entomologists prefer the names ladybird beetles or lady beetles as th ...
, have forward wing cases which open out in flight but do not flap significantly. While on the ground they protect the delicate main, hind wings, while in the air they may be used to modify the aerodynamics of the flapping main wing.Geisler, Tomasz (2012);
Analysis of the Structure and Mechanism of Wing Folding and Flexion in Xylotupes Gideon Beetle (L. 1767) (Coloptera, Scarabaeditae)
, ''Acta Mechanica et Automatica'', Vol.6 No.3, 2012.


Flying fish

Flying fish have enlarged
pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...
s and are capable of gliding flight, though not of true flapping flight. Some species, such as the band-wing, also have sufficiently enlarged
pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two ...
s, further back along their bodies, to form a tandem layout.


Dinosaurs

Microraptor ''Microraptor'' ( Greek, μικρός, ''mīkros'': "small"; Latin, ''raptor'': "one who seizes") is a genus of small, four-winged dromaeosaurid dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. ...
was a genus of tandem-winged
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s, possibly only a single species. It is known only from the fossil record, principally in China. Both fore and hind limbs were covered in flight feathers and it is thought to have been capable of true flapping flight as well as gliding. Its flight mode is not known.


See also

* Stagger (aeronautics)


References


Citations


Bibliography

*Bottomley, J. W. (1977). "Tandem-Wing Aircraft", ''Aerospace'', vol. 4, October 1977. pp. 12–20. *Miles, George H. (1944). *Poulsen, C. M. (1943). "The Tandem Monoplane: Does it Still Have a Future? Some Past Experiences Recalled", ''Flight'', 12 August 1943, pp. 167–8. (Archive
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