Editing Saab 37 Viggen (section)

== Development ==
=== Origins ===
The Viggen was initially developed as an intended replacement for the [[Saab 32 Lansen]] in the attack role and later the [[Saab 35 Draken]] as a fighter.<ref name= "Karling">{{Citation |last= Karling |first= Krister |language= sv |title= Saab 37 Viggen – utvecklingen av ett Nytt Enhetsflygplan för det Svenska Flygvapnet 1952–1971: Sett ur en Aerodynamikers Perspektiv |isbn= 91-631-2395-9 |place= Stockholm |publisher= Svenska mekanisters riksfören |series= Småskrift | issn = 1652-3563 | number = 2 |trans-title= Saab 37 Viggen – Development of a New Unitary aircraft for the Swedish Air Force 1952–1971: From an Aerodynamicist's View |year= 2002}}</ref><ref name= "saab 60" /> In 1955, as Saab's prototype Draken, the most aerodynamically advanced fighter in the world at that point, performed its first flight, the Swedish Air Force was already forming a series of requirements for the next generation of combat aircraft; due to the challenging nature of these requirements, a lengthy development time was anticipated, with the first flight intended to be no earlier than the middle of the next decade.<ref name= "bomber 243">Gunston and Gilchrist 1993, p. 243.</ref><ref name= "field 707">Field 1974, p. 707.</ref> Between 1952 and 1957, the first studies towards what would become the Viggen were carried out, involving the Finnish aircraft designer [[Aarne Lakomaa]]. Over 100 different concepts were examined in these studies, involving both single- and twin engine configurations, both traditional and [[Delta wing#double delta|double delta]] wings, and [[Canard (aeronautics)|canard wings]]. Even [[VTOL]] designs were considered, with separate lift engines, but were soon identified as being unacceptable.<ref name= "Karling" /><ref name= "field 707" /><ref name= "warwick 1260" />

From the onset, the Viggen was planned as an integrated weapon system, to be operated in conjunction with the newest revision of Sweden's national electronic air defense system, [[STRIL]]-60. It was used as the nation's standard platform, capable of being efficiently adapted to perform all tactical mission roles.<ref name= "bomber 243" /> Other requirements included [[Supersonic speed|supersonic]] ability at low level, [[Mach number|Mach]] 2 performance at altitude, and the ability to make short landings at low angles of attack (to avoid damaging improvised runways). The aircraft was also designed from the beginning to be easy to repair and service, even for personnel without much training.<ref>{{Citation | first1 = Anders | last1 = Nowotny | first2 = Sten | last2 = Ekedahl | url = http://www.aircraftresourcecenter.com/AWA1/101-200/walk200_viggen/walk200.htm | title = Viggen walkaround | publisher = Aircraft resource center | access-date = 23 April 2007 | archive-date = 20 February 2007 | archive-url = https://web.archive.org/web/20070220110308/http://www.aircraftresourcecenter.com/AWA1/101-200/walk200_viggen/walk200.htm | url-status = dead }}</ref><ref>Bitzinger 1991, p. 18.</ref>

One radical requirement of the proposed aircraft was the ability for it to be operated from relatively short runways only 500 meters long; this was part of the [[Bas 60]] air base system that had been introduced by the Swedish Air Force in the late 1950s. Bas 60 revolved around [[force dispersal]] of aircraft across many wartime air bases, including [[Highway strip|road runways]] acting as backup runways.<ref>{{Cite web | place = NU |url= http://www.fht.nu/Dokument/Flygvapnet/flyg_publ_dok_flygbassystemet_bas_60.pdf |archive-url=https://web.archive.org/web/20150924012245/http://www.fht.nu/Dokument/Flygvapnet/flyg_publ_dok_flygbassystemet_bas_60.pdf |archive-date=2015-09-24 |url-status=live|title= Flygbassystem 60 |last= Rystedt|first= Jörgen |date= 1 October 2005 | work = FHT}}</ref><ref>{{Cite web | place = [[Sweden|SE]] |url= https://www.forsvarsmakten.se/siteassets/5-information-och-fakta/historia/vagbaserna/fortv-2007-1.pdf |archive-url=https://web.archive.org/web/20170603214913/http://www.forsvarsmakten.se/siteassets/5-information-och-fakta/historia/vagbaserna/fortv-2007-1.pdf |archive-date=2017-06-03 |url-status=live |title= Svenska militära flygbaser|last=Törnell |first= Bernt |date= 5 February 2007 | work = Forsvarsmakten}}</ref><ref>{{Cite web | place = SE |url= https://www.forsvarsmakten.se/siteassets/5-information-och-fakta/historia/vagbaserna/fortv_rapport_2006.1.pdf |archive-url=https://web.archive.org/web/20170604001219/http://www.forsvarsmakten.se/siteassets/5-information-och-fakta/historia/vagbaserna/fortv_rapport_2006.1.pdf |archive-date= 2017-06-04 |url-status=live |title= Svenska reservvägbaser|last= Andersson |first= Lennart |date= 23 November 2006 | work = Forsvarsmakten}}</ref> Utilizing partially destroyed runways was another factor that motivated STOL capability. Bas 60 was developed into [[Bas 90]] in the 1970s and 1980s, and included short runways only 800 meters in length.<ref>{{Cite web | place = NU |url= http://www.fht.nu/Dokument/Flygvapnet/flyg_publ_dok_flygbassystem_90.pdf |archive-url=https://web.archive.org/web/20160514115339/http://fht.nu/Dokument/Flygvapnet/flyg_publ_dok_flygbassystem_90.pdf |archive-date=2016-05-14 |url-status=live |title= Flygbassystem 90 |last= Rystedt | first= Jörgen |date= 20 April 2009 | work = FHT}}</ref> Enabling such operations imposed several critical demands upon the design, including a modest landing speed, no-flare touchdown, powerful post-landing deceleration, accurate steering even in crosswinds on icy surfaces, and high acceleration on take-off.<ref name= "bomber 243" />

In 1960, the U.S. [[United States National Security Council|National Security Council]], led by President [[Dwight D. Eisenhower|Eisenhower]], formulated a security guarantee for Sweden, promising U.S. military help in the event of a Soviet attack against Sweden; both countries signed a military-technology agreement. In what was known as the "[[Sweden–United States relations#Military relations|37-annex]]", Sweden was allowed access to advanced U.S. [[Aeronautics|aeronautical]] technology that made it possible to design and produce the Viggen much faster and more cheaply than would otherwise have been possible.<ref name= "SDRA">{{Citation |language= sv | place = SE |url= http://www.foi.se/Global/Våra%20tjänster/Rapporter/Tidningen%20Framsyn/Framsyn%202005/Framsyn%20Nr%201%202005.pdf |title= Hemliga atomubåtar gav Sverige säkerhetsgaranti |trans-title= Secret nuclear submarines gave Sweden security guarantee |newspaper= Framsyn |year= 2005 |number= 1 |publisher= The Swedish Defence Research Agency}} {{Dead link |date= March 2018 |bot= InternetArchiveBot |fix-attempted= yes}}</ref> According to research by [[Nils Bruzelius]] at the [[Swedish Defence University|Swedish National Defence College]], the reason for this officially unexplained U.S. support was to protect U.S. [[UGM-27 Polaris|Polaris]] submarines deployed just outside the Swedish east coast against the threat of Soviet anti-submarine aircraft.<ref name= "SDRA" /> However, Bruzelius' theory has been discredited by Simon Moores and Jerker Widén.<ref name="KKrVAHT nr 4 2007">{{Citation |language= sv |url= http://www.kkrva.se/wp-content/uploads/Artiklar/074/kkrvaht_4_2007_9.pdf |archive-url=https://web.archive.org/web/20120321195606/http://www.kkrva.se/wp-content/uploads/Artiklar/074/kkrvaht_4_2007_9.pdf |archive-date=2012-03-21 |url-status=live |title= En djärv tes utan empiriskt stöd |trans-title= A bold claim without empirical support |journal= KKrVAHT |number= 4 |year= 2007 |place= SE}}</ref> The connection also appears doubtful due to the time scale – the Viggen's strike version only became operational in 1971, and the fighter version in 1978, by which time Polaris had already been retired.{{Citation needed |date= March 2016}}

=== Project launch ===
In December 1961, the Swedish government gave its approval for the development of ''Aircraft System 37'', which would ultimately become the Viggen.<ref name="saab 60">[http://saabgroup.com/about-company/history/1960s/ "1960s."] ''Company History'', Saab. Retrieved 6 March 2016.</ref> By 1962, all elements for the project either existed or were close to fully developed; these included the aircraft itself, the powerplant, ejector seat, armaments, reconnaissance systems, ground servicing equipment, and training equipment such as simulators.<ref name="bomber 243" /> In February 1962, approval of the overall configuration was given and was followed by a development contract in October 1962.<ref name="field 707" /> According to aviation authors [[Bill Gunston]] and Peter Gilchrist, the project was "by far the largest industrial development task ever attempted in Sweden".<ref>Gunston and Gilchrist 1993, pp. 243–44.</ref> During the 1960s, the Viggen accounted for 10 percent of all Swedish R&D funding.<ref>Larsson, Letell and Thörn 2012, p. 47.</ref>

In 1963, Saab finalized the aerodynamic design of the aircraft; the aerodynamic configuration was radical: it combined an aft-mounted double delta wing with a small, high-set canard foreplane, equipped with powered trailing [[Flap (aeronautics)|flaps]] mounted ahead of and slightly above the main wing; this would be judged to be the best means to satisfy the conflicting demands for STOL performance, supersonic speed, low turbulence sensitivity at low level flight, and efficient lift for subsonic flight.<ref name="saab 60" /><ref name="bomber 244">Gunston and Gilchrist 1993, p. 244.</ref> Canard aircraft have since become common in fighter aircraft, notably with the [[Eurofighter Typhoon]], [[Dassault Rafale]], Saab JAS 39 Gripen and the [[IAI Kfir]], but principally for the purposes of providing agility during flight rather than for its [[STOL]] capabilities.<ref name= "warwick 1260" /><ref>Roskam 2002, p. 206.</ref> Further aerodynamic refinements during the later stage of development included the addition of [[Leading-edge extension#Dogtooth extension|dog-tooth]] patterns upon the main wing to generate [[Vortex|vortices]], allowing for the elimination of [[blown flap]]s from the canard. The use of a [[thrust reversal|thrust reverser]] enabled the sought short landing performance.<ref name= "bomber 244" /><ref>Roskam 2002, p. 376.</ref>

[[File:AJ37 Viggen Aircraft.jpg|thumb|left|AJS 37 Viggen on display at the [[Swedish Air Force Museum]], [[Linköping]]]]
During development, Saab had opted to power the type using a single large [[turbofan]] engine. Originally, the British [[Rolls-Royce Medway]] engine had been selected to power the Viggen, which was then considered to be ideal for the basis for a supersonic engine equipped with a fully modulated [[afterburner]]; however, development of the Medway engine was cancelled due to the intended launch aircraft, the [[Hawker Siddeley Trident|de Havilland Trident]], being downsized during development.<ref name="bomber 244" /> In place of the Medway, Saab chose to adopt a licence-production version of the American [[Pratt & Whitney JT8D]] engine, the [[Volvo RM8]], instead. The RM8 was heavily redesigned, using new materials to accommodate flight at Mach-2 speeds, a Swedish-built afterburner, and a fully variable nozzle.<ref name="bomber 244" />

During 1964, construction of the first [[prototype]] aircraft commenced; on 8 February 1967, the first of an eventual seven prototypes conducted its [[maiden flight]], which had occurred as per the established development schedule.<ref name="Donald Military">Donald 1996, p. 366.</ref><ref name= "proto first" /><ref>Eliasson 2010, pp. 81–82.</ref> This first flight, which lasted for 43 minutes, was flown by Erik Dahlström, Saab's chief test pilot, who reported the prototype to have been easy to handle throughout. Writing at the time, [[aerospace]] publication [[Flight International]] described the flight as having been "Sweden's astonishing unilateral stand in the front rank of advanced aircraft-building nations…"<ref name="proto first">[https://www.flightglobal.com/pdfarchive/view/1967/1967%20-%200272.html "The Viggen Airborne."] ''Flight International'', 16 February 1967, p. 270.</ref>

Each of the seven prototypes were assigned different roles, although the initial aircraft were focused on supporting the development of the initial production variant, the AJ37.<ref name = "bomber 245">Gunston and Gilchrist 1993, p. 245.</ref> In 1967, the Swedish Government concluded that the in-development AJ 37 Viggen would be both cheaper than and superior to the [[McDonnell Douglas F-4 Phantom II]].<ref name="warwick 1261" /> In April 1968, the Swedish government formally issued the authorization for manufacturing of the Viggen to proceed, issuing an order for 175 Viggens that year.<ref name="saab 70s" /><ref name= "ford 617">Ford 1973, p. 617.</ref> Also in 1968, Saab began work on the Viggen's maritime reconnaissance and photo reconnaissance variants.<ref name= "ford 617" /> In May 1969, the Viggen made its first public appearance outside of Sweden at the [[Paris Air Show]].<ref>[https://www.flightglobal.com/pdfarchive/view/1969/1969%20-%200974.html "Paris Airshow..."] ''Flight International'', 29 May 1969, p. 880.</ref> On 23 February 1971, the first production aircraft, an AJ37 model, conducted its first flight.<ref name="bomber 247" /> In July 1971, the first production aircraft was delivered to the Swedish Air Force.<ref name="saab 70s">[http://saabgroup.com/about-company/history/1970s/ "1970s."] ''Company history'', Saab. Retrieved 6 March 2016.</ref><ref name = "Eliasson 87">Eliasson 2010, p. 87.</ref>

=== Further development ===
[[File:Saab SF 37 Viggen 37951 F 13 Bråvalla 001.jpg|thumb|An SF 37 Viggen in flight, 1977]]
As the initial AJ 37 Viggen was being introduced to service, further variants of the Viggen proceeded to complete development and enter production.<ref name = "wagner 125">Wagner 2009, p. 125.</ref> In 1972, the first SK 37, an operational trainer variant with a staggered second canopy for an instructor, was delivered to the Swedish Air Force.<ref name = "fred 279" /><ref name="ford 616">Ford 1973. p. 616.</ref> On 21 May 1973, the first prototype of SF 37 Viggen, a tactical reconnaissance variant featuring a modified nose to accommodate seven sensors, conducted its first flight.<ref>Wagner 2009, pp. 125–26.</ref>

While other variants entered production during the 1960s, Saab continued the development of the more capable all-weather interceptor version of the aircraft, the JA 37. In 1970, Sweden's air defenses had been closely inspected and it was determined that the prospective JA 37 Viggen was highly suited to the role.<ref name="warwick 1261" /> In 1972, the Swedish government authorized the development of the fighter-interceptor variant to proceed, which was followed by several major contracts for the JA 37's further development.<ref name="ford 617" /> A total of five prototypes would be produced, four of which being modified AJ 37s and one being a sole pre-production JA 37 model, to test the control systems, engine, avionics, and armaments respectively.<ref name="warwick 1261" /> In June 1974, the first of these prototypes conducted its maiden flight; later that year, an initial order for 30 JA 37s was issued by the Swedish government.<ref name="warwick 1261" />

The JA 37 Viggen featured various changes from its predecessor, including revisions to the design of the airframe, the use of the more powerful RM8B powerplant, a new generation of electronics being adopted, and a revised armament configuration employed; the principal externally visible changes from most earlier variants were a taller tailfin and the underfuselage gunpack arrangement.<ref name = "fred 279" /><ref name="warwick 1260" /><ref>Chant 2014, pp. 458–59.</ref> The JA 37, in addition to its principal aerial combat mission, also retained a secondary ground-attack capability, and was better suited to low-level operations.<ref name="warwick 1261" /><ref name="chant 458" /> In November 1977, the first production JA 37 Viggen conducted its maiden flight.<ref name="chant 459" /> Operational trials for the new variant were conducted between January and December 1979, which resulted in the type being introduced to operational service that year.<ref name="chant 459">Chant 2014, p. 459.</ref><ref name= "warwick 1265" /> According to [[Flight International]], at the time of the JA 37's introduction, it was the most advanced European fighter then in service.<ref name="warwick 1260" />

[[File:Saab JA37C Viggen, Sweden - Air Force AN1117367.jpg|thumb|left|JA 37 Viggen at the [[Royal International Air Tattoo]] 1993]]
In April 1964, the Swedish government revealed its budget proposal for the Swedish Air Force, in which it had been envisioned that 800 or more Viggens would be produced, which was in turn intended to allow all other combat aircraft then in service with the Swedish Air Force to be replaced with this single type.<ref>[https://www.flightglobal.com/pdfarchive/view/1964/1964%20-%201127.html "World News: Over 800 Viggens."] ''Flight International'', 23 April 1964, p. 630.</ref> However, a combination of [[inflation]] and other factors eventually reduced the total number of aircraft manufactured to 329.<ref name="bomber 247" /> By 1980, up to 149 JA 37 Viggens were projected to be built, and the line to be closed within the decade as the Swedish aerospace industry changed focus to the impending Saab JAS 39 Gripen, the Viggen's eventual replacement.<ref name= "warwick 1260" /> Over time, advances in computing, such as the [[microprocessor]], had enabled greater flexibility than the physical configuration of the Viggen, so further development of the Viggen platform was not viewed as cost-effective.<ref>Eliasson 2010, pp. 87, 229.</ref> In 1990, production of the Viggen ceased and the final aircraft was delivered.<ref>Forsberg 1994, p. 220.</ref><ref name = "Eliasson 82">Eliasson 2010, p. 82.</ref>

In May 1991, a [[Swedish krona|SEK]] 300-million program to upgrade 11 AJ37, SF37 and SH37 Viggens to a common multirole variant, designated AJS37, was announced. Amongst the changes involved, interchangeable armaments and sensor payloads were implemented in addition to the adoption of new mission planning and threat analysis computer systems. The onboard ECM systems were also improved.<ref name="bomber 247" /> Specifically, the implementation of a new stores management system and [[MIL-STD-1553]] [[serial communication|serial]] [[bus (computing)|data bus]], similar to that used on the newer JAS 39 Gripen, allowed for the integration of the [[AIM-120 AMRAAM]] air-to-air missile; an upgraded Ericsson PS-46A radar was installed, and a new tactical radio. On 4 June 1996, the first upgraded prototype JA37 Viggen performed its first flight.<ref name="upgrade flies" />

In 1996, according to Swedish air force material-department chief General Steffan Nasstrom, the various upgrades performed to the Viggen since its introduction had "doubled the effectiveness of the overall system".<ref name="upgrade flies">Jeziorski, Andrzej. [https://www.flightglobal.com/news/articles/saab-flies-upgraded-viggen-fighter-12677/ "Saab flies upgraded Viggen fighter."] ''Flight International'', 19 June 1996.</ref>