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VIGGEN AJ-37 (SAAB)

In December 1961 the Swedish Government approved development of Aircraft System 37, the Viggen. The basic platform was the AJ 37 attack aircraft, to be followed by S 37 reconnaissance versions and the JA 37 fighter. The new aircraft had a novel and advanced aerodynamic configuration to meet the short take-off/landing and other performance requirements: a fixed foreplane with flaps was mounted ahead of and slightly above the delta main wing. On 8 February 1967 the first prototype of the Saab 37 Viggen family made its maiden flight. In April 1968 the Government authorized Viggen production and the first aircraft was delivered in July 1971. A total of 329 aircraft were eventually built in attack, trainer, two reconnaissance versions and the more powerful fighter variant that included new avionics, new air-to-air missiles and Europe´s first pulse-Doppler radar.

The aircraft's main wings are low-mounted, delta-shaped, extending from the body midsection to the exhaust. Small, clipped delta wings are forward of the main wings and high-mounted on the body. There is one turbofan engine in the body. There are semicircular air intakes just forward and below the secondary wings. There is a large, single exhaust. The fuselage is short and wide with a pointed, solid nose. There is a bubble canopy and a small belly fin. There are no tail flats. There is a large, unequally tapered fin with a small, clipped tip.

During the late 1950s and early 1960s very rapid technological developments continued. This occurred not only in aviation, but perhaps even more in the electronic field. At the same time the operational requirements through the constant change of the threat, prompted by weapons development and an accelerating arms race in the world around us. The expected disarmament after World War II had been transformed into a new period of arms during the Cold War. Against this background, the Air Force attack units were renewed and a replacement for A32 Lance started in 1952.

Even before the J 35 Draken first flew in 1955 began to study various concepts for a successor to J 35: an, but also a successor to the A 32 Lansen. Between 1952 and 1956 SAAB studied over 100 different types of aircraft and a large number of possible projects. One of these projects, number 1300, had a number of variants of which Project 1357 was the first with the new canard wing [nosvingen] that would become so characteristic of Viggen.

The development of Viggen took place in a climate of constant questioning from the media. Had Sweden really needs to so advanced and expensive armament systems? Financially, it was necessary to obtain a so-called unitart aircraft, which could satisfy the demands of attack, hunting and reconnaissance. During the design stage in the 1950's and early 1960's there was not the possibility that the aircraft could change weapons platform that can now be done on the JAS 39 Gripen with a few keystrokes. This meant a need for attack, hunting and reconnaissance versions. The basic requirements, however, was the same for all versions, namely, short take-off and landing distance and extremely good speed resources. There was also a requirement that the aircraft could reach an altitude of 10,000 meters two minutes after the driver released the brakes on the runway. Inexpensive maintenance and high availability, and prompt preparation of air operations were also among the basic requirements.

In February 1961 the KFF (Royal Flight Administration) gave approval for continued development of the aircraft 37. In December 1961 the KFF decided that the American engine Pratt & Whitney JT8D-D would be used in the Viggen. The JT8 D was an engine that would be used in the civilian Boeing 727 and 737. The same engine was also later on the familiar DC 9s. There was a version that had been designated JT8-22 who was one of the United States, thought military version, and this engine became the final choice of engine for the Viggen. SFA (Svenska Flygmotor - Swedish aircraft engine) had to basically rebuild the engine from the ground up to be used in the aircraft 37 in demanding military conditions. After remodeling and adding a Swedish designed afterburner, the engine got the designation RM8A. It had a thrust of 6690 kgf without EBK (efterbrännkammare - afterburner) and 11800 kg with the EBK. This engine was the time the strongest engine of a fighter ever in the world. Later fighter version of the Viggen improved RM8, now called RM8B with 7415 kg without EBK and 13125 kg with the EBK.

After various studies in phases until 1962, aimed alternatingly between hunting and / or attack aircraft, the eventual decision for a single aircraft in various versions for training, attack, reconnaissance and search missions would be developed. In April 1962 SAAB was appointed the main supplier and it was thought that 830 aircraft would be built. But there were other priorities, and in the end only 330 aircraft of all versions were built, plus 9 test aircraft.

The first version was produced series was the basic version 37. AJ attack missions against naval and ground targets, the main task for the AJ 37, but even easier hunting mission (combat air targets) could be performed. The first production aircraft was delivered to the Air Force June 21, 1971 and was followed by a further 5 aircraft for further testing and instructor training pilots in the Air Force. In 1973 came the first AJ 37 to F7 in Såtenäs, which became the first operational Viggen. The AJ 37 had no internal armament, with armament hung in pods under the wings, there was even automatic cannon pod. The Viggen was developed during the Vietnam War, and from there came the idea that internal cannon was out-dated, it was missiles and rockets that were required. That decision would later be regretted in the Air Force.

The J 37-1 first flew in February 8, 1967. The testing of 37-1 then showed that a number of steps must be performed to improve flight characteristics and soil behavior before the final version of the AJ37 could be presented. It included, among other things the rudder authority strengthened and that the reverse system was changed. The final action of the flight performance was the introduction of "Rimforsa Bulan", a form body on the ridge which balanced out the aircraft's zero torque in pitch and the special additions caused by external load. When JA37 later conceived introduced including a stronger and less susceptible to interference engine, enhanced controls and increased internal fuel.

The development of Viggen continued and in May 1973 the SF 37 flew for the first time. This version was based entirely on the AJ 37, but was designed for photo reconnaissance, and equipped with advanced camera equipment including reconnaissance dark with various IR equipment. No less than seven cameras were mounted on this type. Series deliveries for this version started in 1977 and first went to F 13 in Norrköping, then each Kallinge F 17, F 21 and F 10 Lulea Angelholm. Another reconnaissance version was produced, SH 37 was an advanced radar reconnaissance aircraft designed for maritime surveillance. SH 37 was supplied F13, F17 and F 21. Both SF and SH versions were later modernized and upgraded to be able to perform attack missions and was given the designation AJSF 37 and AJSH 37th.

The last version built by SAAB 37 was JA 37 Viggen. This was basically a new aircraft but differed only to the exterior through its larger fin and the body was prolonged by 13 cm because of the bigger engine RM8B. From the time the Viggen began had computers and electronics have made enormous steps forward and took advantage of it in the new version which had a new central computer with five times the capacity of the basic version. In addition, there were four on the basis of programmable computers on board that either did not exist in the basic version. Radar and radio and navigation system were of an entirely new generation with significantly improved performance.

The mistake of the basic version had now been remedied by building a 30mm Oerlikon cannon in the fuselage. This machine gun had an ammunition which gave six times more impact force than the Adenkanon had been in external pods to AJ 37. The autopilot was a class apart. When the driver had locked on a target autopilot took over control in the yaw and pitch plane for precision aiming with machine gun which relieved the driver so that he could devote himself to tactical and situational orientation. The JA 37 Viggen can in many cases be considered a second generation fighter. There were few other planes in the world that could compare with the Viggen.

The last of 329 Viggens, a JA 37 fighter version, was delivered from Saab in Linköping to the Swedish Air Force in 1990. Since then, Viggen has undergone several upgrades, the latest being Mod. D for the fighter version including communication and weapon systems similar to those in Gripen.

Even an export version called Saab 37E Eurofighter project was developed in the early 1970s. The aircraft intended to have the same configuration and performance JA37. Potential buyers were certain countries within NATO but also Australia in 1972 and Japan in 1973 and India in 1978. No sale was completed, however. Austria showed interest in Saab 37X, an export version of JA37 in the 1980s, but chose instead the J35DO.






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