Saab 37 Viggen
The Saab 37 Viggen is a single-seat, single-engine multirole combat aircraft designed and produced by the Swedish aircraft manufacturer Saab. It was the first canard-equipped aircraft to be produced in quantity and the first to carry an airborne digital central computer with integrated circuits for its avionics, arguably making it the most modern/advanced combat aircraft in Europe at the time of introduction. The digital central computer was the first of its kind in the world, automating and taking over tasks previously requiring a navigator/copilot, facilitating handling in tactical situations where, among other things, high speeds and short decision times determined whether attacks would be successful or not, a system not surpassed until the introduction of the Panavia Tornado into operational service in 1981.
Development work began during the early 1950s to develop a successor to the Saab 32 Lansen in the attack role, as well as to the Saab 35 Draken as a fighter. Saab's design team opted for a relatively radical delta wing configuration, and operation as an integrated weapon system in conjunction with Sweden's STRIL-60 national electronic air defense system. It was also designed to be operated from runways as short as 500 meters. Development work was aided by the "37-annex" under which Sweden could access advanced U.S. aeronautical technology to accelerate both design and production. The aircraft's aerodynamic design was finalised in 1963. The prototype performed its maiden flight on 8 February 1967 and the following year the Swedish government ordered an initial batch of 175 Viggens. The first of these entered service with the Swedish Air Force on 21 June 1971.
Even as the initial AJ 37 model entered service, Saab was working on further variants of the Viggen. Several distinct variants of the Viggen would be produced to perform the roles of fighter bomber/strike fighter, aerial reconnaissance, maritime patrol/anti-surface and a two-seat trainer. During the late 1970s, the all-weather interceptor/strike fighter JA 37 variant was introduced. Attempts to export the Viggen to other nations were made, but ultimately proved unsuccessful. In November 2005, the last Viggens were withdrawn from service by the Swedish Air Force, its only operator; by this point, it had been replaced by the newer and more advanced Saab JAS 39 Gripen.
Name
Viggen is the definite form of the Swedish word vigg, which has two meanings. According to Saab, the aircraft's name alluded to both.The first meaning refers to the Swedish name for the tufted duck, a small diving duck common in Sweden. In this sense, it serves as a reference to the aircraft's canard configuration, as "canard" is French for duck.
Vigg is also åskvigg, or "thunderbolt", stemming from the thunderstones of Nordic folklore, called "åskviggar", said to come from the lightning strikes of Norse god Thor when he hunted giants with his war hammer, Mjölnir.
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. 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. 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 double delta wings, and canard wings. Even VTOL designs were considered, with separate lift engines, but were soon identified as being unacceptable.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. Other requirements included supersonic ability at low level, Mach 2 performance at altitude, and the ability to make short landings at low angles of attack. The aircraft was also designed from the beginning to be easy to repair and service, even for personnel without much training.
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 road runways acting as backup runways. 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. 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.
In 1960, the U.S. National Security Council, led by President 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 "37-annex", Sweden was allowed access to advanced U.S. aeronautical technology that made it possible to design and produce the Viggen much faster and more cheaply than would otherwise have been possible. According to research by Nils Bruzelius at the Swedish National Defence College, the reason for this officially unexplained U.S. support was to protect U.S. Polaris submarines deployed just outside the Swedish east coast against the threat of Soviet anti-submarine aircraft. However, Bruzelius' theory has been discredited by Simon Moores and Jerker Widén. 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.
Project launch
In December 1961, the Swedish government gave its approval for the development of Aircraft System 37, which would ultimately become the Viggen. 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. In February 1962, approval of the overall configuration was given and was followed by a development contract in October 1962. According to aviation authors Bill Gunston and Peter Gilchrist, the project was "by far the largest industrial development task ever attempted in Sweden". During the 1960s, the Viggen accounted for 10 percent of all Swedish R&D funding.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 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. 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. Further aerodynamic refinements during the later stage of development included the addition of dog-tooth patterns upon the main wing to generate vortices, allowing for the elimination of blown flaps from the canard. The use of a thrust reverser enabled the sought short landing performance.
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 de Havilland Trident, being downsized during development. 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.
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. 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…"
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. 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. 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. Also in 1968, Saab began work on the Viggen's maritime reconnaissance and photo reconnaissance variants. In May 1969, the Viggen made its first public appearance outside of Sweden at the Paris Air Show. On 23 February 1971, the first production aircraft, an AJ37 model, conducted its first flight. In July 1971, the first production aircraft was delivered to the Swedish Air Force.