Saab 21R

Design and development

In early 1945, Saab launched a project to determine how to provide the J 21A with a jet engine to get the experience of jet engines and flying at high speeds. The goal was to catch up with the development of jet aircraft, which were moving ahead fast in England, where, among others, de Havilland already had the de Havilland Vampire in production.

When the project started, the engine choice was an open question. However, as the project progressed it became possible to buy a "Goblin 2" jet engine from de Havilland Engine Company, along with the license to manufacture in Sweden. This engine became the Air Force's first Jet Engine, RM1. The rebuilt J 21A received type designation J21R. First flight with Saab's first jet took place on 10 March 1947.

Changes from the J 21A version

Because of the engine exhaust position, the stabilizer had to be raised, which meant that the tail had to be redesigned. Measures to improve the aerodynamic design of the aircraft were carried out, for example, curved front glass in the canopy and a refined wing leading edge. Airbrakes were introduced in the form of an upward and a downward flap on the outer wing's trailing edge. Ejection seat improvements were made to enable ejections at high speed. Fuel volume increased significantly with the use of tanks in the middle wing and large wingtip tanks.

The attack version A 21R added 14.5 cm attack rockets placed under the middle wing. Furthermore, an alternative external machine gun pod was created. A big sensation was that it was possible to fire all 13 weapons at the same time. This was an interesting "sensation" for the pilot as well.

A production of 124 planes was planned originally, including four prototypes. When experience with the type as a fighter was gained with the F10 wing it was concluded that all aircraft needed to be changed to attack aircraft. The production series was then reduced to 64 aircraft. Of these, 34 were J21RA fitted with the Goblin 2 engine, RM1, with 1360kp of thrust.

30 J21RB with a Swedish-made Goblin 3 engine, RM1A, with a thrust of 1500kp.

Operational history

The first prototype Saab 21R first flew on 10 March 1947, almost 2 years after the Second World War. The aircraft first entered service with F 10 in August 1950. Although the type was originally intended as a fighter aircraft, a newly developed fighter, the Saab J 29 first flew in October 1948, the number to be produced was halved from 120 to 60, and eventually all 21Rs were converted to attack aircraft as A 21RA or the A 21RB depending on the engine type.

Variants

J 21RA / A 21RA

First production series, powered by British-built engines, 34 built in 1950 (including four prototypes), retired in 1953.

J 21RB / A 21RB

Second production series, powered by Swedish-built engines, 30 built between 1950 and 1952, retired in 1956.

Operators

 Sweden

Swedish Air Force

F10 Ängelholm, 1949–51: J21RA

F7 Såtenäs, 1950–54: A21RA/B

F17 Kallinge, 1954–56: A21RA/B

Specifications (Saab 21RA)

Data from Attack and Interceptor Jets

General characteristics

Crew: One

Length: 10.45 m (34 ft 3 in)

Wingspan: 11.37 m (37 ft 4 in)

Height: 2.90 m (9 ft 8 in)

Empty weight: 3,200 kg (7,055 lb)

Max. takeoff weight: 5,000 kg (11,023 lb)

Powerplant: 1 × De Havilland Goblin 2 turbojet, 13.8 kN (3,100 lbf)

Performance

Maximum speed: 800 km/h (497 mph)

Range: 720 km (450 mi)

Service ceiling: 12,000 m (39,400 ft)

Takeoff roll: 650 m (2,133 ft)

Armament

1x 20 mm Bofors cannon

4x 13.2 mm M/39A heavy machine guns

Centerline pod for an additional 8x 13.2 mm M/39A heavy machine guns

Wing racks for either: 10x 100 mm or 5x 180 mm Bofors rockets, or 10x 80 mm anti-tank rockets.