SAAB 21

https://en.wikipedia.org/wiki/SAAB_21

The SAAB 21 was a Swedish fighter and attack aircraft designed and manufactured
by Swedish aviation company SAAB. It used a relatively unorthodox and visually
distinctive combination of a twin boom fuselage and a pusher configuration,
giving the aircraft a fairly unique appearance.

Work on the development of the 21 commenced at SAAB following a decision by the
Swedish Air Force to embark on a large-scale expansion programme in preparation
to fears that the nation might get dragged into the Second World War. The
company designed a monoplane twin-boom aircraft, powered by a single
Daimler-Benz DB 605B engine that was positioned within the rear of the fuselage,
directly behind the pilot, that drove a rear-facing propeller, commonly known as
a pusher configuration. This arrangement allowed armaments to be contained
within the aircraft's nose section as well as providing the pilot with a high
degree of external visibility. To safely enable the pilot to bail out without
striking the propeller behind him, it was decided to adopt an ejection seat.

On 30 July 1943, the 21 performed its maiden flight; on 1 December 1945, the
first model of the fighter, the J 21A-1 was introduced to service. It was
quickly followed by the improved J 21A-2, which featured a heavier armament
arrangement, and the B 21A-3, which was a dedicated fighter-bomber mode of the
type. In response to interest from the Swedish Air Force in adopting a
jet-powered fighter, SAAB developed a conversion of the aircraft, using the
British de Havilland Goblin as its powerplant. The jet-powered model of the
aircraft was designated as the 21R. During the mid-1950s, less than ten years
after its introduction, the 21 was withdrawn from service, having been replaced
by a new generation of jet-powered fighters such as the de Havilland Vampire and
the Saab 29 Tunnan.

The Saab 21 was an unorthodox twin-boom pusher configuration fighter aircraft.
It featured a low-mounted wing, a tricycle landing gear arrangement, and was
furnished with heavy forward-firing armament. Several recent innovations were
incorporated into its design, such as an ejector seat for the pilot; the pusher
layout later allowed the type to be readily modified with a turbojet engine as
well. The advantages of a pusher design are of an unobstructed forward view for
the pilot, while the armament can also be concentrated in the nose; however, a
major drawback is difficulty in escaping from the aircraft in an emergency, as
the pilot could get drawn into the propeller blades. Saab resolved this issue
via the installation of an early ejector seat, developed by Swedish defense firm
Bofors, which was developed in conjunction with the fighter itself.

The wing of the 21 was based on a SAAB-designed low drag airfoil; as the wings
could not reasonably accommodate recesses for the main landing gear when
retracted, alcoves were instead provided within the tail booms, directly aft of
the rear wing spar. Other systems, such as the center-section fuel tanks, were
incorporated into the wing, which complicated their design considerably. To
minimise drag, the coolers and ducts for the engine were housed within the
contours of the airfoil between the fuselage and tail booms.

The armament initially consisted of two 13.2 mm automatkanon m/39A (akan m/39A)
autocannons in the wings and two more 13.2 mm akan m/39A autocannons and a 20 mm
akan m/41A in the nose. On the A-2 model the 20 mm akan m/41 was replaced with a
belt fed Bofors designed 20 mm akan m/45. On the J 21A-3 (later designated A
21A) it was possible to load rockets and bombs of various sizes and types. Later
in the Saab 21's service life the 13.2 mm akan m/39 autocannons were rebarreled
to fire american 12.7x99 mm ammunition due to economics. This was not a bad
change though as the 12.7 mm AP-rounds had better performance than the 13.2 mm
AP rounds and the Saab 21 was basically only viable as an attacker after WWII
due to the jet era.


Role
Fighter and attack aircraft

Manufacturer
SAAB

Designer
Frid Wänström

First flight
30 July 1943

Introduction
1 December 1945

Retired
23 July 1954

Status
Retired

Primary user
Swedish Air Force

Produced
1945–49

Number built
298

Developed into
Saab 21R

Operational history

On 1 December 1945, deliveries of the initial production model of the fighter,
designated as the J 21A-1, commenced to the Swedish Air Force. Overall, 54 J
21A-1 fighters were constructed at SAAB's main plant in Trollhättan; deliveries
of this model continued until 5 December 1946, by which point it had been
superseded by improved models. The J 21A-1 model was quickly followed by another
124 and 119 examples of the improved J 21A-2, which featured a revised armament
arrangement, and the B 21A-3, a dedicated fighter-bomber, respectively. The type
was used by the Swedish Air Force alone. In total, 298 J 21As were constructed
prior to the production line being closed down during 1948.

During December 1945, F 8 Barkarby became the first fighter unit to receive the
J 21. During the following year, other units of the Swedish Air Force, such as
Göta Air Force Wing (F 9), also began to receive the type. However, within less
than four years, some squadrons that had received the type were being
re-equipped with a new generation of fighters harnessing jet propulsion for
greater speed, such as the de Havilland Vampire. Despite the original intention
for the type to be principally in air defence roles, in service, the J 21 was
utilized mainly in the bomber role. According to Widfeldt, officials were often
confused by its unconventional design and had doubts over the fighter's use and
effectiveness.

In response to feedback that sought alternative options, the Swedish Air Board
approached SAAB with a request to conduct design studies into the proposed
development of a front-engine replacement, which was referred to as the J 23.
This aircraft shared the same DB 605B engine as the J 21, but had a more
traditional appearance; Widfeldt observed that the J 23 concept was visually
similar to the North American P-51 Mustang, he also noted that its projected
performance was beneath that of the existing J 21, which had been a key factor
in the decision to persist with efforts to improve the existing fighter instead.
Over time, the Swedish Air Force had become increasingly interested in jet
propulsion and, as early as 1945, SAAB had been examining prospective
modifications of the airframe to accommodate a jet engine in place of its piston
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. As a result of the conversion
programme, the iJ 21A was phased out after 1954.

Specifications

General characteristics
Crew: one
Length: 10.45 m (34 ft 3 in)
Wingspan: 11.6 m (38 ft 0 in)
Height: 3.97 (13 ft 0 in)
Wing area: 22.2 m² (238.87 ft²)
Empty weight: 3,250 kg (7,165 lb)
Loaded weight: 4,150 kg (9,149 lb)
Max. takeoff weight: 4,413 kg (9,730 lb)
Powerplant: 1 × Daimler-Benz DB 605B, built by SFA. liquid-cooled, supercharged,
60° inverted V12 engine, 1,085 kW (1,455 hp / 1,475 PS)

Performance
Maximum speed: 650 km/h, 350 knots, 403 mph (fighter config), 560 kmh, 302
knots, 347 mph (attacker config)
Cruise speed: 495 km/h (265 knots, 308 mph)
Range: 750 km (466 mi)
Service ceiling: 11,000 m (36,090 ft)
Rate of climb: 15 m/s (2,950 ft/min)

Armament
J 21A-1
1× 20 mm akan m/41A with a 60 round drum magazine in the nose
2x 13.2 mm (0.53 in) akan m/39A with 350 rpg in the nose
2x 13.2 mm (0.53 in) akan m/39A with 325 rpg in the wings

J 21A-2 & A-3
1× 20 mm akan m/45 with 140 rounds in the nose
2x 13.2 mm (0.53 in) akan m/39A with 350 rpg in the nose
2x 13.2 mm (0.53 in) akan m/39A with 325 rpg in the wings





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