The prototype of the trainer variant of the SAAB 37 Viggen - SK 37 - flew for the first time in the summer of 1970. It is now exhibited at the Swedish Air Force Museum (Flygvapenmuseum) at Malmen, Linköping. See photo at top. 17 more aircraft were manufactured by SAAB and delivered to the Air Force 1972-1976.  

The SK 37 was based on the attack version of the Viggen - AJ 37. The designation ”AJ” indicates that the aircraft’s secondary rôle is as an interceptor. To get room for a second cockpit, the front fuselage fuel tank had to be removed. Because of this, the SK 37 usually flies with a large drop fuel tank. Also the radar and some other avionics were omitted. The fin was made larger and the rear cockpit was provided with periscopes. 

The engine, Swedish designation RM 8A, was license-built by Volvo Flygmotor. It was based on a Pratt & Whitney JT8D turbo-fan, designed initially for civil airliners but further developed in Sweden for its military super-sonic use. The afterburner was entirely a Swedish design. The engine had a thrust of 12.000 kp/117,6 kN (including reheat).  

When the JAS 39 Gripen was introduced in the Air Force, ten SK 37 were converted into ECM aircraft (Electronic Counter Measures) and got the designation SK 37E. The ECM operator uses the rear cockpit. The ECMO has a number of active and passive countermeasures at his command:  

Axel/U95 - Jamming pod for training and self-protection. The U95 pod is also developed for use with JAS 39 Gripen. The control and display system is unique for SK 37E. Together with the U95 pod, this system is called Axel.    

G24 - Radar jammer. The antennas are located in the nose. The SK 37E variant can be recognized by the yellow marking on the radome, which shows the ”window” which allow signals in the S- and C-band to pass the radome without being attenuated too much. 

U22/A - Jamming pod for self-protection, developed for the attack and reconnaissance variants of the 37 Viggen. 

KB - Chaff- and flare dispenser, designed and further developed for the attack and reconnaissance variants of the 37 Viggen.   

APP 27 -or ”Apparat 27” - Radar warning receiver (RVR). 

In addition to this, FR 31 (Flygradio 31) has been installed in the -E version to be used by the ECMO for communication independently from the pilot. A modern GPS (Global Positioning System) has also been integrated with the earlier navigation system.  

Length: 16,0 m. Span: 10,6 m. MTOW: 15.587 kg. Max. speed: Mach 2. 

See also the chapters Jet Fighters, Attack Aircraft and Reconnaissance Aircraft. 

Photo below: SK 37 at Wing F 7 (Såtenäs) July, 1973. Photo by Lars E. Lundin, Västervik

For the Model Builder

Revell has an excellent plastic model kit of SAAB SK 37 in the marking of the Swedish Air Force. Scale 1:72. Catalouge number 4365. Click on the thumbnail for larger image.

© Lars Henriksson

Updated 2010-03-21