Saab J21BSweden wished to ensure its continued neutrality through a policy of armed strength during World War II but was effectively denied access to foreign weapons. Seeking to ensure that Sweden would not be on the future menu for Nazi conquests, the Swedish air force look to build it's own fighter aircraft. The original design studies began in 1939, based around the use of a Bristol Taurus engine within the centre fuselage, behind the pilot, driving a pusher propeller. The project remained dormant until 1941. In response to the need for air defence, and faced with the prospect of imported designs being unavailable due to the war, Sweden undertook an indigenous rearmament programme including an advanced fighter. The low-wing monoplane Saab 21 fighter was ultimately designed around a license-produced version of the Daimler-Benz DB 605B engine, featured innovations such as tricycle landing gear, heavy forward-firing armament, ejector seat, and a twin-boom pusher layout that later allowed the type to be modified with a turbojet engine.
The advantages of a pusher design are that the view forward is unobstructed and armament can be concentrated in the nose, while a major drawback is difficulty in escaping from the aircraft in an emergency, as the pilot could get drawn into the propeller blades. Saab deliberated between systems that would eject the pilot, or jettison the propeller or the engine, via a system of explosive bolts, and eventually installed an early ejector seat developed by Bofors for the purpose and tested in 1943.
In 1947, the aircraft was redesigned making use of a Rolls Royce Griffon engine with over 50% airframe, tailplane and wing changes, acquiring the new designation Saab J 21B. In addition, the upper rear fuselage was cut down and a bubble canopy, styled on the P-51D Mustang was put in place, affording the pilot much improved visibility to the rear quarter. Armed with three 20mm cannon in the nose and four .50cal HMGs (two in each wing), the aircraft was fast and well armed.
Operational historyThe first of three J 21 prototypes flew on 30 July 1943 flown by SAAB test pilot Claes Smith. During the takeoff, the wrong flap setting resulted in the prototype running into a fence at the end of the runway, damaging one of the landing gears. The subsequent test flight ended with a successful landing on the undamaged undercarriage units.
A total of 54 J 21A-1 fighters constructed at the main plant in Trollhättan were delivered from December 1945, followed by 124 and 119 examples respectively of the J 21A-2 with revised armament and the J 21A-3 fighter-bomber. Utilised mainly in the bomber role, the limitation of the design led to a proposed front-engine replacement, the J 23. An evaluation of the two designs led to the decision to retain the J 21 series but to consider the modification of the airframe to accommodate either a Griffon or a jet engine. While production line J 21A series aircraft were first selected for conversion, the initial piston-engine version continued in production in five series "batches" that were completed in 1948–49. In service use, the J 21 was phased out after 1954. The J 21B was not adopted, the Goblin jet powered J 21R was used instead.
The ModelThe model combines elements of the Heller J21A and the Airfix P-51D kits. I initially just wanted to cut down the J21A fuselage and use a P-51D bubble canopy. However, after a little experimentation I decided it was easier to use the nose of the P-51D as it carried a Merlin engine in it. Then I decided that the underfuselage scoop would be needed and so that came off the P-51D fuselage. After a fair amount of PSR the two mated quite well. Then I realised the booms needed extending which was accomplished with some square tubing. Then the propeller from the P-51 had to be shortened to fit between the booms. The end result is one that looks pleasing to the eye, I think.
