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Delta wing

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This article is about the wing shape. For the racing car, seeDeltaWing.
TheDassault Mirage 2000is among the most successful delta-winged fighter jets, being used by many countries to this day.

Adelta wingis awingshaped in the form of a triangle. It is named for its similarity in shape to the Greek uppercase letterdelta(Δ).

Although long studied, it did not find significant applications until theJet Age,when it proved suitable for high-speedsubsonicandsupersonicflight. At the other end of the speed scale, theRogallo flexible wingproved a practical design for thehang gliderand otherultralight aircraft.The delta wing form has unique aerodynamic characteristics and structural advantages. Many design variations have evolved over the years, with and without additional stabilising surfaces.

General characteristics[edit]

Structure[edit]

The long root chord of the delta wing and minimal area outboard make it structurally efficient. It can be built stronger, stiffer and at the same time lighter than aswept wingof equivalentaspect ratioand lifting capability. Because of this it is easy and relatively inexpensive to build—a substantial factor in the success of theMiG-21andMirageaircraft series.[citation needed]

Its long root chord also allows a deeper structure for a givenaerofoilsection. This both enhances its weight-saving characteristic and provides greater internal volume for fuel and other items, without a significant increase in drag. However, on supersonic designs the opportunity is often taken to use a thinner aerofoil instead, in order to actually reduce drag.

Aerodynamics[edit]

Low-speed flight and vortex lift[edit]

Like any wing, at low speeds a delta wing requires a highangle of attackto maintain lift. At a sufficiently high angle the wing exhibitsflow separation,together with an associated high drag.[1]

Ordinarily, this flow separation leads to a loss of lift known as thestall.However, for a sharply-swept delta wing, as air spills up round the leading edge it flows inwards to generate a characteristicvortexpattern over the upper surface. The lower extremity of this vortex remains attached to the surface and also accelerates the airflow, maintaining lift. For intermediate sweep angles, a retractable "moustache" or fixedleading-edge root extension(LERX) may be added to encourage and stabilise vortex formation. The ogee or "wineglass" double-curve, seen for example onConcorde,incorporates this forward extension into the profile of the wing.

In this condition, the centre of lift approximates to the centre of the area covered by the vortex.

Subsonic flight[edit]

In the subsonic regime, the behaviour of a delta wing is generally similar to that of a swept wing. A characteristic sideways element to the airflow develops. In this condition, lift is maximised along the leading edge of the wing, where the air is turned most sharply to follow its contours. Especially for a slender delta, the centre of lift approximates to halfway back along the leading edge.

The sideways effect also leads to an overall reduction in lift and in some circumstances can also lead to an increase in drag. It may be countered through the use of leading-edge slots, wing fences and related devices.

Transonic and low-supersonic flight[edit]

Convair made several supersonic deltas. This is anF-106 Delta Dart,a development of their earlier F-102 Delta Dagger

With a large enough angle of rearward sweep, in thetransonicto lowsupersonicspeed range the wing's leading edge remains behind theshock waveboundary orshock conecreated by the leading edge root.

This allows air below the leading edge to flow out, up and around it, then back inwards creating a sideways flow pattern similar to subsonic flow. The lift distribution and other aerodynamic characteristics are strongly influenced by this sideways flow.[2]

The rearward sweep angle lowers the airspeed normal to the leading edge of the wing, thereby allowing the aircraft to fly at highsubsonic,transonic, or supersonic speed, while the subsonic lifting characteristics of the airflow over the wing are maintained.

Within this flight regime, drooping the leading edge within the shock cone increases lift, but not drag to any significant extent.[3]Such conical leading edge droop was introduced on the productionConvair F-102A Delta Daggerat the same time that the prototype design was reworked to includearea-ruling.It also appeared on Convair's next two deltas, theF-106 Delta DartandB-58 Hustler.[4]

High-speed supersonic waveriding[edit]

At high supersonic speeds, the shock cone from the leading edge root angles further back to lie along the wing surface behind the leading edge. It is no longer possible for the sideways flow to occur and the aerodynamic characteristics change considerably.[2]It is in this flight regime that thewaveriderdesign, as used on theNorth American XB-70 Valkyrie,becomes practicable. Here, a shock body beneath the wing creates an attached shockwave and the high pressure associated with the wave provides significant lift without increasing drag.

Design variations[edit]

Aérospatiale-BACConcordeshows off its ogee wing

Variants of the delta wing plan offer improvements to the basic configuration.[5]

Cropped delta– tip is cut off. This helps maintain lift outboard and reduce wingtip flow separation (stalling) at high angles of attack. Most deltas are cropped to at least some degree.

In thecompound delta,double deltaorcranked arrow,the leading edge is not straight. Typically the inboard section has increased sweepback, creating a controlled high-lift vortex without the need for a foreplane. Examples include theSaab Drakenfighter, the experimentalGeneral Dynamics F-16XL,and the Hawker Siddeley HS. 138 VTOL concept. Theogee delta(orogival delta) used on the Anglo-FrenchConcordesupersonic airlineris similar, but with the two sections and cropped wingtip merged into a smoothogeecurve.

" "
Tailless delta 		" "
Cropped delta 		" "
Compound delta 		" "
Cranked arrow 		" "
Ogival delta 		" "
Tailed delta

Tailed delta– adds a conventional tailplane (with horizontal tail surfaces), to improve handling. Common on Soviet types such as theMikoyan-Gurevich MiG-21.

Canard delta– Many modern fighter aircraft, such as theJAS 39 Gripen,theEurofighter Typhoonand theDassault Rafaleuse a combination ofcanardforeplanes and a delta wing.

Tailless delta[edit]

TheSaab 35 Drakenwas a successful tailless double-delta design

Like othertailless aircraft,the tailless delta wing is not suited to high wing loadings and requires a large wing area for a given aircraft weight. The most efficient aerofoils are unstable in pitch and the tailless type must use a less efficient design and therefore a bigger wing. Techniques used include:

  • Using a less efficient aerofoil which is inherently stable, such as a symmetrical form with zero camber, or even reflex camber near the trailing edge,
  • Using the rear part of the wing as a lightly- or even negatively-loaded horizontal stabiliser:
    • Twisting the outer leading edge down to reduce the incidence of the wing tip, which is behind the main centre of lift. This also improves stall characteristics and can benefit supersonic cruise in other ways.
    • Moving the centre of mass forwards and trimming the elevator to exert a balancing downforce. In the extreme, this reduces the craft's ability to pitch its nose up for takeoff and landing.

The main advantages of the tailless delta are structural simplicity and light weight, combined with low aerodynamic drag. These properties helped to make theDassault Mirage IIIone of the most widely manufactured supersonic fighters of all time.

Tailed delta[edit]

A conventional tail stabiliser allows the main wing to be optimised for lift and therefore to be smaller and more highly loaded. Development of aircraft equipped with this configuration can be traced back to the late 1940s.[6]

When used with a T-tail, as in theGloster Javelin,like other wings a delta wing can give rise to a "deep stall"in which the high angle of attack at the stall causes the turbulent wake of the stalled wing to envelope the tail. This makes the elevator ineffective and the airplane cannot recover from the stall.[7]In the case of the Javelin, astall warning devicewas developed and implemented for the Javelin following the early loss of an aircraft to such conditions.[8]Gloster's design team had reportedly opted to use a tailed delta configuration out of necessity, seeking to achieve effective manoeuvrability at relatively high speeds for the era while also requiring suitable controllability when being flown at the slower landing speeds desired.[9]

Canard delta[edit]

TheEurofighter Typhoonhas a canard delta wing configuration.

A lifting-canard delta can offer a smaller shift in the center of lift with increasing Mach number compared to a conventional tail configuration.

An unloaded or free-floating canard can allow a safe recovery from a high angle of attack. Depending on its design, a canard surface may increase or decrease longitudinal stability of the aircraft.[10][11]

A canard delta foreplane creates its own trailing vortex. If this vortex interferes with the vortex of the main delta wing, this can adversely affect the airflow over the wing and cause unwanted and even dangerous behaviour. In the close-coupled configuration, the canard vortex couples with the main vortex to enhance its benefits and maintain controlled airflow through a wide range of speeds and angles of attack. This allows both improved manoeuvrability and lower stalling speeds, but the presence of the foreplane can increase drag at supersonic speeds and hence reduce the aircraft's maximum speed.

History[edit]

Early research[edit]

Triangular stabilizing fins for rockets were described as early as 1529-1556 by the Austrian military engineerConrad Haasand in the 17th century by the Polish-Lithuanian military engineerKazimierz Siemienowicz.[12][13][14]However, a true lifting wing in delta form did not appear until 1867, when it waspatentedby J.W. Butler and E. Edwards in a design for a low-aspect-ratio, dart-shaped rocket-propelled aeroplane. This was followed by various similarly dart-shaped proposals, such as a biplane version by Butler and Edwards, and a jet-propelled version by the RussianNicholas de Telescheff.[15]In 1909 a variant with acanard foreplanewas experimented with by the Spanish sculptor Ricardo Causarás.[16][17]

Also in 1909, British aeronautical pioneerJ. W. Dunnepatented his tailless stable aircraft with conical wing development. The patent included a broad-span biconical delta, with each side bulging upwards towards the rear in a manner characteristic of the modernRogallo wing.[18]During the following year, in America U. G. Lee and W. A. Darrah patented a similar biconical delta winged aeroplane with an explicitly rigid wing. It also incorporated a proposal for a flight control system and covered both gliding and powered flight.[19][20]None of these early designs is known to have successfully flown although, in 1904, Lavezzani's hang glider featuring independent left and right triangular wings had left the ground, and Dunne's other tailless swept designs based on the same principle would fly.[19]

The practical delta wing was pioneered by German aeronautical designerAlexander Lippischin the 1930s, using a thick cantilever wing without any tail. His first such designs, for which he coined the name "Delta", used a very gentle angle so that the wing appeared almost straight and the wing tips had to be cropped sharply (see below). His first such delta flew in 1931, followed by four successively improved examples.[21][22]These prototypes were not easy to handle at low speed and none saw widespread use.[23][24]

Subsonic thick wing[edit]

TheAvro Vulcanbomber had a thick wing

During the latter years ofWorld War II,Alexander Lippisch refined his ideas on the high-speed delta, substantially increasing the sweepback of the wing's leading edge. An experimental glider, theDM-1,was built to test the aerodynamics of the proposedP.13ahigh-speedinterceptor.[25]Following the end of hostilities, the DM-1 was completed on behalf of theUnited Statesand the shipped toLangley FieldinVirginiafor examination byNACA(National Advisory Committee for Aeronautics, forerunner of today'sNASA) It underwent significant alterations in the US, typically to lower its drag, resulting in the replacement of its large vertical stabilizer with a smaller and more conventional counterpart, along with a normal cockpit canopy taken from aLockheed P-80 Shooting Star.[26]

The work of French designerNicolas Roland Payensomewhat paralleled that of Lippisch. During the 1930s, he had developed a tandem delta configuration with a straight fore wing and steep delta aft wing, similar to that of Causarás. The outbreak of the Second World War brought a halt to flight testing of thePa-22,although work continued for a time after the project garnered German attention.[27]During thepostwarera, Payen flew an experimental tailless delta jet, thePa.49,in 1954, as well as the tailless pusher-configurationArbalèteseries from 1965. Further derivatives based on Payen's work were proposed but ultimately went undeveloped.[28][29]

Following the war, the British developed a number of subsonic jet aircraft that harnessed data gathered from Lippisch's work. One such aircraft, theAvro 707research aircraft, made its first flight in 1949.[30]British military aircraft such as theAvro Vulcan(astrategic bomber) andGloster Javelin(an all-weather fighter) were among the first delta-equipped aircraft to enter production. Whereas the Vulcan was a classic tailless design, the Javelin incorporated a tailplane in order to improve low-speed handling and high-speed manoeuvrability, as well as to allow a greatercentre of gravityrange.[31]Gloster proposed a refinement of the Javelin that would have, amongst other changes, decreased wing thickness in order to achieve supersonic speeds of up to Mach 1.6.[32]

Supersonic thin wing[edit]

TheMiG-21fighter had a conventional tail

The American aerodynamicistRobert T. Jones,who worked at NACA during the Second World War, developed the theory of the thin delta wing for supersonic flight. First published in January 1945, his approach contrasted with that of Lippisch on thick delta wings. The thin delta wing first flew on theConvair XF-92in 1948, making it the first delta-winged jet plane to fly.[33]It provided a successful basis for all practical supersonic deltas and the configuration became widely adopted.[34][35]

During the late 1940s, the British aircraft manufacturerFairey Aviationbecame interested in the delta wing,[36]its proposals led to the experimentalFairey Delta 1being produced toAir Ministry Specification E.10/47.[37]A subsequent experimental aircraft, theFairey Delta 2set a newWorld air speed recordon 10 March 1956, achieving 1,132 mph (1,811 km/h) or Mach 1.73.[38][39][40][41]This raised the record above 1,000 mph for the first time and broke the previous record by 310 mph, or 37 per cent; never before had the record been raised by such a large margin.[39][42]

In its original tailless form, the thin delta was used extensively by the American aviation companyConvairand by the French aircraft manufacturerDassault Aviation.The supersonicConvair F-102 Delta Daggerand transonicDouglas F4D Skyraywere two of the first operational jet fighters to feature a tailless delta wing when they entered service in 1956.[43]Dassault's interest in the delta wing produced theDassault Miragefamily of combat aircraft, especially the highly successfulMirage III.Amongst other attributes, the Mirage III was the first Western European combat aircraft to exceed Mach 2 in horizontal flight.[44]

The tailed delta configuration was adopted by theTsAGI(Central Aero and Hydrodynamic Institute,Moscow), to improve highangle-of-attackhandling, manoeuvrability and centre of gravity range over a pure delta planform. TheMikoyan-Gurevich MiG-21( "Fishbed" ) became the most widely built combat aircraft of the 1970s.[45]

Close-coupled canard[edit]

TheSaab Viggenpioneered the close-coupled canard
Main article:Canard (aeronautics)

Through the 1960s, theSwedishaircraft manufacturerSaab ABdeveloped a close-coupled canard delta configuration, placing a delta foreplane just in front of and above the main delta wing.[46]Patentedin 1963, this configuration was flown for the first time on the company'sViggencombat aircraft in 1967. The close coupling modifies the airflow over the wing, most significantly when flying at high angles of attack. In contrast to the classic tail-mounted elevators, the canards add to the total lift as well as stabilising the airflow over the main wing. This enables more extreme manoeuvres, improves low-speed handling and reduces the takeoff run and landing speed. During the 1960s, this configuration was considered to be radical, but Saab's design team judged that it was the optimal approach available for satisfying the conflicting performance demands for the Viggen, which including favourableSTOLperformance, supersonic speed, low turbulence sensitivity during low level flight, and efficient lift for subsonic flight.[47][48]

The close-coupled canard has since become common on supersonic fighter aircraft. Notable examples include the multinationalEurofighter Typhoon,France'sDassault Rafale,Saab's ownGripen(a successor to the Viggen) and Israel'sIAI Kfir.One of the main reasons for its popularity has been the high level of agility in manoeuvring that it is capable of.[49][50]

Supersonic transport[edit]

Main article:Supersonic transport

When supersonic transport (SST) aircraft were developed, the tailless ogival delta wing was chosen for both the Anglo-FrenchConcordeand the SovietTupolev Tu-144,the Tupolev first flying in 1968. While both Concorde and the Tu-144 prototype featured anogival deltaconfiguration, production models of the Tu-144 differed by changing to adouble deltawing.[51]The delta wings required these airliners to adopt a higherangle of attackat low speeds than conventional aircraft; in the case of Concorde, lift was maintained by allowed the formation of large low pressure vortices over the entire upper wing surface.[52]Its typical landing speed was 170 miles per hour (274 km/h), considerably higher than subsonic airliners.[53]Multiple proposed successors, such as theZero Emission Hyper Sonic TransportZEHST), have reportedly adopted a similar configuration to that Concorde's basic design, thus the Delta wing remains a likely candidate for future supersonic civil endeavours.[54]

Rogallo flexible wing[edit]

This hang glider is a relatively broad-span and lightly swept Rogallo delta
Main article:Rogallo wing

During and after WWII, Francis and Gertrude Rogallo developed the idea of a flexible wing which could be collapsed for storage. Francis saw an application in spacecraft recovery and NASA became interested. In 1961 Ryan flew theXV-8,an experimental "flying Jeep" or "fleep". The flexible wing chosen for it was a delta and in use it billowed out into a double-cone profile which gave it aerodynamic stability. Although tested but ultimately never used for spacecraft recovery, this design soon became popular forhang glidersandultra-light aircraftand has become known as the Rogallo wing.

See also[edit]

References[edit]

Citations[edit]

  1. ^Rom, Josef (1992).High Angle of Attack Aerodynamics: Subsonic, Transonic, and Supersonic Flows.New York, NY: Springer New York. pp.15–23.ISBN9781461228240.OCLC853258697.
  2. ^abMason, Chap. 10, pp. 9–12.
  3. ^Boyd, Migotzky and Wetzel; "A Study of Conical Camber for Triangular and Sweptback Wings", Research Memorandum A55G19, NACA, 1955.[1][dead link]
  4. ^Mason, Chap. 10, p. 16.
  5. ^Corda, Stephen (2017).Introduction to aerospace engineering with a flight test perspective.Chichester, West Sussex, United Kingdom: John Wiley & Sons. pp. 408–9.ISBN9781118953372.OCLC967938446.
  6. ^Allward 1983, pp. 11–12.
  7. ^Gloster Javelin History,UK: Thunder & Lightnings, 4 April 2012,archivedfrom the original on 9 June 2011,retrieved10 February2011.
  8. ^Patridge 1967, p. 6.
  9. ^Patridge 1967, pp. 3–4.
  10. ^Probert, B,Aspects of Wing Design for Transonic and Supersonic Combat,NATO, archived fromthe original(PDF)on 17 May 2011.
  11. ^Aerodynamic highlights of a fourth generation delta canard fighter aircraft,Mach flyg, archived fromthe originalon 27 November 2014.
  12. ^"Corad Haas Raketenpionier in Siebenbürgen"[Corad Haas rocket pioneer in Transylvania].Beruehmte Siebenbuerger Sachsen(in German). Siebenbürgen und die Siebenbürger Sachsen im Internet.Archivedfrom the original on 2018-09-17.Retrieved2010-09-09.
  13. ^New Rocket Guide(PDF),NASA, archived fromthe original(PDF)on 2010-01-19.
  14. ^Orłowski, Bolesław (Jul 1973),Technology and Culture,vol. 14, JStor, pp. 461–73,doi:10.2307/3102331,JSTOR3102331,S2CID113306514.
  15. ^Wragg, David W.;Flight Before Flying,Osprey, 1974, pp. 87-88, 96.
  16. ^"El Aeroplano-Monoplano Causarás en la Presna de 1909".1909-2009 100 Anos de Aviacion Espanola.Generalitat Valencia. 2002. Retrieved 17 April 2023.
  17. ^Patent application 46026 "Aeroplano Monoplano Causarás".Ricardo Causarás. 1909. Retrieved 17 April 2023.
  18. ^J.W. Dunne;Provisional Patent: Improvements Relating to Aeroplanes,UK Patent No. 8118, Date of Application 5 April 1909.Copy on EspacenetArchived2021-10-01 at theWayback Machine
  19. ^abWoodhams, Mark and Henderson, Graeme; "Did we really fly Rogallo wings?",Skywings,June 2010.
  20. ^Lee, U. G. and Darrah, H.; US patent 989,7896, filed 15 February 1910, granted 18 April 1911.
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  23. ^Madelung, Ernst Heinrich; Hirschel, Horst; Prem, Gero (2004).Aeronautical research in Germany: from Lilienthal until today(American ed.). Berlin: Springer.ISBN3-540-40645-X.Archivedfrom the original on 2021-10-01.Retrieved2020-10-04.
  24. ^Wohlfahrt, Karl; Nickel, Michael (1990).Schwanzlose flugzeuge: ihre auslegung und ihre eigenschaften[Tailless aircraft: their design & properties] (in German). Basel: Birkhauser. pp. 577–78.ISBN3-7643-2502-X.Archivedfrom the original on 1 October 2021.Retrieved13 February2011.[Lippisch Delta I and Horten H I] Both these aircraft shown, how not to do it.
  25. ^Grommo (17 May 2008),Lippisch P13a Supersonic Ramjet Fighter footage(video),Youtube,archivedfrom the original on 15 April 2016,retrieved27 November2016.
  26. ^"Research Memorandum L7F16"Archived2017-05-03 at theWayback Machine,NACA, 5 August 1947.
  27. ^LePage, Jean-Denis G. G. (2009).Aircraft of the Luftwaffe, 1935-1945: an illustrated guide.McFarland. p. 243.ISBN978-0-7864-3937-9.
  28. ^Taylor, John W. R. (1972).Jane's All the World's Aircraft 1972–73.London: Sampson Low, Marston & Co. Ltd. pp. 71–2.
  29. ^Taylor, John W. R. (1973).Jane's All the World's Aircraft 1973-74.London: Jane's Yearbooks. pp. 75–6.ISBN0-354-00117-5.
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  33. ^Jones, Lloyd, S.;U.S. Fighters,Aero, 1975. p.247.
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  35. ^Hallion, Richard. "Lippisch, Gluhareff and Jones: The Emergence of the Delta Planform."Aerospace Historian,March 1979.
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  37. ^Wood 1975, p. 74.
  38. ^"Individual History: Fairey FD-2 Delta WG777/7986M."Archived2020-06-26 at theWayback MachineRoyal Air Force Museum,Retrieved: 13 December 2016.
  39. ^ab"50 years ago: 16 Mar 1956."Archived20 December 2016 at theWayback MachineFlight International,10 March 2006.
  40. ^Wood 1975, p. 77.
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  42. ^Wood 1975, p. 79.
  43. ^Gunston, Bill (1976),Early Supersonic Fighters of the West,Shepperton: Ian Allan Ltd., pp. 181 and 230,ISBN0-7110-0636-9,103/74
  44. ^"Mirage III."Dassault Aviation,18 December 2015.
  45. ^Sweetman, Bill & Gunston, Bill;Soviet Air Power: An Illustrated Encyclopedia.Salamander, 1978, p. 122.
  46. ^Green, W; Swanborough, G (1994),The complete book of fighters,Salamander, pp. 514 to 516.
  47. ^"1960s."Archived2020-06-29 at theWayback MachineCompany History,Saab. Retrieved 6 March 2016.
  48. ^Gunston and Gilchrist 1993, p. 244.
  49. ^Warwick 1980, p. 1260.
  50. ^Roskam 2002, p. 206.
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  52. ^Orlebar 2004,p. 44.
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  54. ^"Concorde's successor revealed at Paris Air Show",The Independent,20 June 2011,archivedfrom the original on 22 June 2011,retrieved21 June2011

Bibliography[edit]

External links[edit]

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