SAAB 21

Background SAAB was carrying out design studies during the late 1930s into possible options for a new fighter aircraft. Many of these had been based around the use of a British Bristol Taurus radial engine and some were unconventional for the time. While this promising design study was completed, it remained dormant until 1941, when defence considerations heightened the imminent need for it. Accordingly, SAAB began looking at solutions to various anticipated production problems for their proposed fighter. ==Design==

The SAAB J 21 needed a top speed of at least , which required a powerful engine. It was decided to substitute the Taurus engine for the American Pratt & Whitney R-1830 Twin Wasp radial engine. The SAAB 21 was an unorthodox twin-boom low wing pusher configuration fighter aircraft with a tricycle landing gear, and a heavy forward-firing armament. Several recent innovations were incorporated into its design, including an ejection seat for the pilot while the pusher layout later allowed the type to be readily re-engined with a turbojet. The advantages of a pusher design include an unobstructed forward view for the pilot, and the armament can be concentrated in the nose, however, a major drawback is difficulty in making an emergency exit as the pilot could get drawn into the propeller blades. Many solutions were examined, such as jettisoning either the propeller or the engine via explosive charges prior to bailing out, before it was decided to adopt an ejection seat developed by Swedish defense firm Bofors, in parallel with the fighter. The J 21 was one of the first operational aircraft in the world with an ejection seat. Swedish Air Force enthusiasm for a jet fighter in late 1945 pushed SAAB to produce a version of the J 21 using jet propulsion. At Swedish Air Force request, existing J 21 aircraft were converted to jet propulsion in 1947 and redesignated J 21R. This required modifications to over 50 per cent of the airframe, including the tailplane and wing. The aircraft was to be powered by a single British-sourced de Havilland Goblin turbojet engine, to replace the DB 605B. It entered Swedish Air Force service as their first jet aircraft. ==Operational history==

The first example from the first batch of 54 of the first production variant, the J 21A-1 was delivered to the Swedish Air Force on 1 December 1945. During December 1945, the Svea Wing (F 8) became the first fighter unit to receive the J 21. Despite the original intention for the type to be principally used in air defence roles, in service, the J 21 was utilized mainly in the light bomber role. The type was used only by the Swedish Air Force. Officials doubted its effectiveness due to its unconventional design. In response, the Swedish Air Board requested that SAAB study a development with the engine in the nose as the J 23. ==Variants==

;J 21A-1 :First production series of fighter version. 54 built between 1945 and 1946, retired in 1949. ;J 21A-2: :Second and third production series of fighter version (62 aircraft each built between 1946 and 1947). Aircraft had better avionics and was armed with a Swedish gun. Retired between 1953 and 1954. J 21A-3 (later designated A 21A) :First and second production series of attack version (66 aircraft each built between 1947 and 1949). Aircraft was a J 21A-2 equipped with a bomb aiming sight and had pylons for bombs and rockets. It was later upgraded to be able to use two RATO rockets. ;J 21B :Planned version armed with three nose guns, radar in the starboard boom, improved aerodynamics, P-51 style bubble canopy and a stronger engine. Suggested engines were at first the Daimler-Benz DB 605E or the Rolls-Royce Griffon engine but due to the end of the war Germany could not deliver the DB-605E and the British had not yet finished the development of the Griffon engine. It was then decided to use the Swedish DB-605B engine modified to 1700 hp. A full scale mockup was built but due to the jet age the project was scrapped at the end of 1945 due to the Saab 29 project. None built. ==Operators==

; • Swedish Air Force ==Surviving aircraft==

Three aircraft are preserved on permanent static display; • J 21A-3, serial 21286, but rebuilt as an A 21R, at the Swedish Air Force Museum. ==Specifications (J 21A)==