Development of the Saab-37 was initiated to provide the Swedish air force with a completely integrated weapon system based on the concept pioneered in the USA. Prolonged research led to adoption of a then-unique canard configuration for the interceptor that was to form the airborne component of the weapon system. The configuration comprises a large rear-mounted delta wing combined with a delta foreplane incorporating trailing-edge flaps. This was adopted to provide improved STOL performance so that the Saab-37 would be able to operate from short runways and sections of roadway about 500m in length, greatly increasing the flexibility of dispersed operations. This configuration, in combination with a high-power turbofan engine, has provided the essential short take-off capability. The engine also complements short landing capability by introducing thrust reversal, its first use in a combat aircraft. The Saab-37 has been designed for a 'no-flare' approach to landing with a rate of sink of 5m per second, and this has meant the design of special landing gear able to absorb such a high rate of descent. Once on the ground, thrust reversal plus anti-skid brakes ensure the achievement of a minimum landing run. The pilot is accommodated on a zero-zero ejection seat in an air-conditioned, heated and pressurised cockpit, protected by a bird-proof windscreen. Much of the capability of this aircraft results from the incorporation of the latest avionics, including for attack a head-up display linked via an air-data computer to a digital fire-control system; for its own protection ECM (electronic countermeasures) and radar warning equipment; for navigating Doppler radar and radar altimeter; and for landing in all weathers a tactical instrument landing system plus a blind-landing guidance system.

The first of seven prototypes made its maiden flight on 8 February 1967 and the initial AJ 37 Viggen (Thunderbolt) single-seater was flown on 23 February 1971, with deliveries being made to Flygflottilj 7 at Satenas from June 1971 onwards. The AJ designation signifies Attack-Jakt, or attack-fighter, underlining its primary role as an attack aircraft. The next versions to be developed were dedicated reconnaissance Viggens. R&D funding was allocated for a nominal 'S-37' (Spanning, or reconnaissance) aircraft programme in 1971, resulting in the SF 37 Viggen (Spanning Foto, or photo-reconnaissance) which was intended to replace the S 35E Drakens and surviving Lansens in their overland mission. The first prototype flew on 21 May 1973. The SF 37 is fitted with a varied array of seven cameras in a chisel nose, which dispenses with radar of any kind. These systems can also be supplemented by pods, particularly night recon-naissance units, on the Viggen's shoulder pylons.

The second dedicated reconnaissance version is the SH 37 Viggen (Spanning Havsovervakning, or sea surveillance) aircraft. The third production Viggen served as the SH 37 prototype, first flying in that configuration on 10 December 1973. A look at any map of Sweden quickly explains why national defence policy places such great emphasis on the threat of seaborne invasion. This goes some way towards explaining the importance of the SH 37's capabilities to the Flygvapen. Fitted with a long-range Ericsson PS-371/A surveillance and attack radar, optimised for over-water operations, the SH 37 also boasts an RKA 40 camera which records radar imagery for analysis. Outwardly, the SH 37 Viggen resembles the AJ 37 aircraft, and if any additional reconnaissance systems are carried they are externally mounted on the shoulder pylons. The usual fit is a night photography pod to port and a LOROP pod to starboard. SH 37 pilots got most of their exercise observing Warsaw Pact naval manoeuvres in the Baltic Sea, but they were no strangers to NATO navy crews either.

Obviously, with the Viggen fulfilling its role as the Flygvapen's primary aircraft system, there was a pressing need for a two-seat trainer version. This role is undertaken by the Sk 37 Viggen (Skol, or school), which is somewhat unusual in having two separate cockpits for pilot and instructor.

The Sk 37s have an extended fin and retain the standard Viggen nose, but carry no radar, instead relying on Doppler equipment and DME to find their way around. Based on the AJ, the Sk 37 has reduced fuel capacity as a result of its extra cockpit, and aircraft often operate with external tanks.

The first 27 Viggens were built with weakened spars and early in its career the type gained an unfortunate reputation as a result. The basic integrity of Saab's design was never in doubt, as borne out by the long service of all its post-war military aircraft, so it came as no surprise when the decision was made to proceed with the final and perhaps most radical development of System-37. To replace the J 35 Draken in the air defence role the JA 37 Viggen (Jakt, or fighter) was conceived, externally identical to the AJ 37 but underneath a very different aircraft. Design work had been underway at a low rate since 1968, and the first contracts were awarded in 1972. A total of five prototypes were required, the first flying on 4 June 1974. The fuselage was subtly stretched by 7cm and the fin gained a distinctive extension (a la Sk 37). The other obvious external difference is a blade VHF aerial, behind the rudder.

An extensive test programme was undertaken to integrate the new Volvo-Flygmotor RM8B engine, Ericsson PS-46 multi-mode radar, BVR missile system, and all-new cockpit avionics and displays. While still a relatively small, single-engined aircraft, the JA 37 is phenomenally manoeuvrable and conforms to Sweden's exacting operational requirement for short missions but high sortie rates. Its wing has been restres-sed to cope with a higher load factor and the aircraft's weight has increased. The first of 149 production JA 37s flew on 4 November 1977, with deliveries commencing in 1980. The final aircraft was handed over to the Flygvapen on 29 June 1990, bringing to an end the Viggen's production run of 329 aircraft (substantially less than Saab had originally hoped for).

Attempts were made to export the aircraft, first as a Starfighter replacement to NATO nations and Japan, a Mirage III replacement for Australia and, later, as a deep penetration strike aircraft to India. All these efforts came to nought, chiefly because of restrictions imposed on Saab by the national legislature.

A proposal to fund attrition replacements for the Swedish air force was also defeated, and first-generation aircraft will be withdrawn before the new JAS 39 Gripen becomes fully operational. To bridge that gap Saab is undertaking an extensive upgrade programme to modify 115 AJ, SF and SH 37s to AJS 37 standard. This involves fitting a new digital databus giving each aircraft a true multi-role capability, a terrain-following radar system, and compatibility with some of the armaments being developed for the Saab Gripen (such as the DWS 39 stand-off dispenser weapon).

3-View

A three-view drawing of Saab JA 37 Viggen (800 x 759)