Elliptical wing
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An elliptical wing is a wing planform whose leading and trailing edges each approximate two segments of an ellipse. It is not to be confused with annular wings, which may be elliptically shaped. Relatively few aircraft have adopted the elliptical wing, an even-smaller number of which attained mass production; the majority of aircraft that did use this feature were introduced during the 1930s and 1940s. Perhaps the most famous aircraft to feature an elliptical wing is the Supermarine Spitfire, a
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposi ...
-era British fighter aircraft. Another major application was the
Heinkel He 70 The Heinkel He 70 ''Blitz'' ("lightning") was a German mail plane and fast passenger monoplane aircraft of the 1930s designed by Heinkel Flugzeugwerke, which was later used as a bomber and for aerial reconnaissance. It had a brief commercial car ...
"Blitz", a German fast
mail plane A mail plane is an aircraft used for carrying mail. Aircraft that were purely mail planes existed almost exclusively prior to World War II. Because early aircraft were too underpowered to carry cargoes, and too costly to run any "economy class" ...
and
reconnaissance In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain, and other activities. Examples of reconnaissance include patrolling by troops (skirmisher ...
bomber A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped from an air ...
; early versions of the
He 111 The Heinkel He 111 is a German airliner and bomber designed by Siegfried and Walter Günter at Heinkel Flugzeugwerke in 1934. Through development, it was described as a "wolf in sheep's clothing". Due to restrictions placed on Germany after th ...
bomber also used such a wing configuration before a simpler design was adopted for economic reasons.


Properties

Theoretically, the most efficient way to create lift is to generate it in an elliptical spanwise distribution across the wing. There is no inherent superiority to pure elliptical shapes, and wings with other planforms can be optimized to give elliptical spanwise lift distributions. The basic elliptical wing shape also has disadvantages: * The almost uniform
lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobil ...
distribution of a constant-aerofoil section elliptical wing can cause the entire span of the wing to stall simultaneously, potentially causing loss of control with little warning. To improve the stalling characteristics and give the pilot some warning, designers use a non-uniform aerofoil. For example, the wing of the Supermarine Spitfire was both thinned towards the tips and twisted to give washout, reducing the load on the tips so that the inner wing would stall first. Such compromises depart from the theoretical elliptical lift distribution, increasing induced drag. An elliptical spanwise lift distribution cannot be achieved by an untwisted wing with an elliptical planform because there is a logarithmic term in the lift distribution that becomes important near the wing tips. *Elliptical wing planforms are more difficult to manufacture. In it, either leading edge or trailing edge or both are curved, and the ribs change in a non uniform way along the wingspan. In practice, most elliptical wings are approximations, for example several sections of the Spitfire leading and trailing edges are arcs of circles.


The semi-elliptical wing

For a wing to have an elliptical area distribution, it is not necessary for both the leading and trailing edges to be curved. If one of these is straight, as in the semi-elliptical planform, the wing may still have an elliptical area distribution. Several aircraft of this type have been produced; one of the most successful being the American
Seversky P-35 The Seversky P-35 is an American fighter aircraft built by the Seversky Aircraft Company in the late 1930s. A contemporary of the Hawker Hurricane and Messerschmitt Bf 109, the P-35 was the first single-seat fighter in United States Army Air Co ...
. During the
postwar In Western usage, the phrase post-war era (or postwar era) usually refers to the time since the end of World War II. More broadly, a post-war period (or postwar period) is the interval immediately following the end of a war. A post-war period ...
era, the semi-elliptical wing profile was extensively studied for its ground effect properties; it was postulated that it would be suitable for
ground-effect vehicle A ground-effect vehicle (GEV), also called a wing-in-ground-effect (WIG), ground-effect craft, wingship, flarecraft or ekranoplan (russian: экранопла́н – "screenglider"), is a vehicle that is able to move over the surface by gainin ...
s (which operate close to the water, in ground effect, to avoid the higher induced drag that occurs out of ground effect). The low level of induced drag produced by a semi-elliptical wing would be beneficial for these vehicles.


History

The British theoretical aerodynamicist Frederick Lanchester was perhaps the first person to write in detail about the elliptical wing, having done so during 1907.
Ludwig Prandtl Ludwig Prandtl (4 February 1875 – 15 August 1953) was a German fluid dynamicist, physicist and aerospace scientist. He was a pioneer in the development of rigorous systematic mathematical analyses which he used for underlying the science of ...
independently rediscovered this in 1917–1918. Despite this early head-start, the elliptical wing was initially viewed as more a theoretical concept than one for practical application, in part due to the overriding needs to compromise between an aircraft aerodynamic properties and its other design aspects. It would be quite some time before practical use of the
planform In technical drawing and computer graphics, a multiview projection is a technique of illustration by which a standardized series of orthographic two-dimensional pictures are constructed to represent the form of a three-dimensional object. Up to ...
would be made. The first aircraft to use the elliptical wing was the
Bäumer Sausewind The Bäumer B II "Sausewind" was a light sports tandem two-seat wooden cantilever monoplane. It was built by German aviation company Bäumer Aero GmbH, based at Hamburg Airport. Specifications References *Hallion, Richard P.Airplanes tha ...
, a German light sports aircraft that performed its
maiden flight The maiden flight, also known as first flight, of an aircraft is the first occasion on which it leaves the ground under its own power. The same term is also used for the first launch of rockets. The maiden flight of a new aircraft type is alw ...
on 26 May 1925. Its designers, the Günther brothers, would subsequently join the German aircraft manufacturer Heinkel and apply their designs, including the elliptical wing, to several different projects undertaken by the firm. During the early 1930s, Heinkel developed a fast
mail plane A mail plane is an aircraft used for carrying mail. Aircraft that were purely mail planes existed almost exclusively prior to World War II. Because early aircraft were too underpowered to carry cargoes, and too costly to run any "economy class" ...
and
reconnaissance In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain, and other activities. Examples of reconnaissance include patrolling by troops (skirmisher ...
bomber A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped from an air ...
, the
Heinkel He 70 The Heinkel He 70 ''Blitz'' ("lightning") was a German mail plane and fast passenger monoplane aircraft of the 1930s designed by Heinkel Flugzeugwerke, which was later used as a bomber and for aerial reconnaissance. It had a brief commercial car ...
"Blitz", which featured the elliptical wing. It proved to have excellent performance for the era, establishing eight individual world records relating to speed over distance, having reportedly attained a maximum speed of 377 km/h (222 mph). Shortly thereafter, Heinkel developed the
He 111 The Heinkel He 111 is a German airliner and bomber designed by Siegfried and Walter Günter at Heinkel Flugzeugwerke in 1934. Through development, it was described as a "wolf in sheep's clothing". Due to restrictions placed on Germany after th ...
bomber, which made its first flight on 24 February 1935. In comparison to the preceding He 70, it was a larger aircraft that initially masqueraded as a civil airliner despite having been developed from conception to provide the nascent
Luftwaffe The ''Luftwaffe'' () was the aerial-warfare branch of the German ''Wehrmacht'' before and during World War II. Germany's military air arms during World War I, the ''Luftstreitkräfte'' of the Imperial Army and the '' Marine-Fliegerabtei ...
with a fast
medium bomber A medium bomber is a military bomber aircraft designed to operate with medium-sized bombloads over medium range distances; the name serves to distinguish this type from larger heavy bombers and smaller light bombers. Mediums generally carrie ...
; this deception was due to restrictions placed on Germany after the
First World War World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
that prohibited the development or deployment of bomber aircraft.Mackay 2003, p. 7. Despite the type being produced in vast numbers before and during the
Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposi ...
, only the early production models of the He 111 were equipped with an elliptical wing.Mackay 2003, p. 9. The chief reason for dropping the He 111's elliptical wing in favour of one with straight leading and
trailing edge The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 199 ...
s was economic, the latter design could be manufactured with greater efficiency.Regnat 2004 p. 31. Perhaps the aircraft company most commonly associated with the elliptical wing was the British manufacturer
Supermarine Supermarine was a British aircraft manufacturer that is most famous for producing the Spitfire fighter plane during World War II as well as a range of seaplanes and flying boats, and a series of jet-powered fighter aircraft after World War II ...
. During the early 1920s, the company's chief designer, Reginald Mitchell, had developed the Supermarine S.4, a British elliptical wing racing
seaplane A seaplane is a powered fixed-wing aircraft capable of taking off and landing (alighting) on water.Gunston, "The Cambridge Aerospace Dictionary", 2009. Seaplanes are usually divided into two categories based on their technological characteri ...
; it conducted its first flight during 1924. While the S.4's direct successors featured a wing designed by a different designer, Mitchell remained a proponent of the planform. By 1934, Mitchell and his design staff were engaged in designing a new fighter aircraft for the
Royal Air Force The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) an ...
. They decided to use a semi-elliptical wing shape to solve two conflicting requirements; the wing needed to be thin to allow a high
critical Mach number In aerodynamics, the critical Mach number (Mcr or M*) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound, but does not exceed it.Clancy, L.J. ''Aerodynamics'', Section 11.6 At t ...
but it had to be thick enough to house the retractable undercarriage, armament, and ammunition. An elliptical planform is the most efficient aerodynamic shape for an untwisted wing, leading to the lowest amount of
induced drag In aerodynamics, lift-induced drag, induced drag, vortex drag, or sometimes drag due to lift, is an aerodynamic drag force that occurs whenever a moving object redirects the airflow coming at it. This drag force occurs in airplanes due to wings or ...
. The semi-elliptical planform was skewed so that the centre of pressure, which occurs near the quarter- chord position at all but the highest speeds, was close to the main spar, preventing the wings from twisting. The Spitfire conducted its maiden flight on 5 March 1936.Ethel 1997, p. 12. Mitchell has sometimes been accused of copying the wing shape of Heinkel's He 70. Communications between Ernest Heinkel and Mitchell during the 1930s establishes Mitchell's awareness of the He 70 and its performance. However, Beverley Shenstone, the
aerodynamicist Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
on Mitchell's team, observed that: "Our wing was much thinner and had quite a different section to that of the Heinkel. In any case, it would have been simply asking for trouble to have copied a wing shape from an aircraft designed for an entirely different purpose."Price 1977, pp. 33–34. Almost all Republic P-47 Thunderbolts, an
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
fighter aircraft, were outfitted with elliptical wings; only the last production models different, instead featuring squared-off wingtips, akin to the low-altitude Spitfire variants. The
Aichi D3A The Aichi D3A Type 99 Carrier Bomber ( Allied reporting name "Val") is a World War II carrier-borne dive bomber. It was the primary dive bomber of the Imperial Japanese Navy (IJN) and was involved in almost all IJN actions, including the a ...
, a Japanese dive bomber operated by the
Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrend ...
, also used an elliptical wing that bore considerable similarity to that of the He 70.Francillon 1979, pp. 272–273. The
Mitsubishi A5M The Mitsubishi A5M, formal Japanese Navy designation , experimental Navy designation Mitsubishi Navy Experimental 9-''Shi'' Carrier Fighter, company designation Mitsubishi ''Ka''-14, was a Japanese carrier-based fighter aircraft. It was the world ...
fighter also utilized an elliptical wing design.Green and Swanborough 1982, p. 28. Several other types had planforms which differed relatively little from the elliptical. The Hawker Tempest II fighter aircraft, which later developed into the
Hawker Fury The Hawker Fury is a British biplane fighter aircraft used by the Royal Air Force in the 1930s. It was a fast, agile aircraft, and the first interceptor in RAF service capable of speed higher than 200 mph (321 kmh). It was the fighter co ...
and
Hawker Sea Fury The Hawker Sea Fury is a British fighter aircraft designed and manufactured by Hawker Aircraft. It was the last propeller-driven fighter to serve with the Royal Navy, and one of the fastest production single reciprocating engine aircraft ...
, also utilised a near-eliptical wing planform, although squared off at the tips.Thomas and Shores 1988, p. 105.Mason 1967, p. 3. Since 2009, the British aircraft company
Swift Aircraft Swift Aircraft is a British aerospace manufacturer that designs the Swift II aerobatic training aircraft. Swift II The Swift II is a side-by-side, twin-seat training and aerobatic aircraft, and is currently in the final stages of design. Swi ...
have been reportedly developing a two-seater
Very Light Aircraft EASA CS-VLA is the European Aviation Safety Agency Certification Specification for Very Light Aircraft. The Very Light Aircraft (VLA) aircraft certification category introduced in 2003 by the European Aviation Safety Agency (EASA) is intended to ...
, Light-sport aircraft and CS-23 category aircraft, the Swift Aircraft Swift, which features elliptical wings.


References


Citations


Bibliography

* Clancy, L. J. ''Aerodynamics.'' Pitman Publishing Limited, London. 1975. . * * Ethell, Jeffrey L. and Steve Pace. ''Spitfire''. St. Paul, Minnesota: Motorbooks International, 1997. . * Francillon, René J. ''Japanese Aircraft of the Pacific War''. London: Putnam & Company Ltd., 1970 (2nd edition 1979). . * Glancey, Jonathan. ''Spitfire: The Illustrated Biography''. London: Atlantic Books, 2006. . * * Mason, Francis K. ''The Hawker Tempest I–IV'' (Aircraft in Profile Number 197). Leatherhead, Surrey, UK: Profile Publications Ltd., 1967. * McCormick, Barnes W. ''Aerodynamics, Aeronautics, and Flight Mechanics.'' John Wiley & Sons, New York, 1979. . pp. 135–139. * Milne-Thomson, L.M. ''Theoretical Aerodynamics'', 4th Ed., Dover Publications Inc, New York, 1966/1973. . pp. 208–209. * Price, Alfred. ''The Spitfire Story: Revised second edition''. Enderby, Leicester, UK: Siverdale Books, 2002. . * * Thomas, Chris and Christopher Shores. ''The Typhoon and Tempest Story''. London: Arms and Armour Press, 1988. . {{Refend


External links


The Spitfire Wing Planform: A Suggestion
via aerosociety.com

via grc.nasa.gov Aircraft wing design Wing configurations