saab18

Design and developmentIntended as a replacement for the Junkers Ju 86 in service with the Swedish Air Force,[1] the requirement that led to the Saab 18 called for a three-seat fast reconnaissance aircraft.[2]

AB Svenska Järnvägsverkstädernas Aeroplanavdelning (ASJA), SAAB, and AB Götaverken (GV) submitted designs for consideration by the Swedish Air Force.[1] GV's GV8 appeared to be the best suited to the requirement, however its cost, and the departure of their chief designer, resulted in SAAB — the company having merged with ASJA in the meantime — being awarded a contract for development of their design.[1]

As a number of Americans were on the design staff of SAAB and ASJA,[3] the Saab 18's design shared some similarities with American designs.[1] The outbreak of World War II in 1939 led to a change of priorities by the Swedish Air Force, and production of the Saab 17 was accelerated, at the expense of work on the Saab 18,[1] which, along with a change of requirements that added the role of medium bomber to the specification, resulted in the first flight of the aircraft being delayed until 19 June 1942.[2]

Manned by a crew of three — a pilot and navigator under a glazed, offset canopy, and a bombardier in the nose[2] — the Saab 18 prototype was a mid-wing monoplane with twin vertical stabilisers,[2] and was powered by two Pratt & Whitney R-1830 Twin Wasp radial engines.[2] Armament consisted of three 13.2-millimetre (0.52 in) machine guns, one fixed firing forwards and controlled by the pilot, the others being in flexible defensive mounts for use by the navigator and bombardier.[1] Up to 1,000 kilograms (2,200 lb) of bombs could be carried in an internal bay, while up to eight 50-kilogram (110 lb) bombs could be carried on underwing hardpoints.[1]

Flight testing showed that the aircraft was underpowered.[2] However, as there was no immediate prospect for the acquisition of more powerful engines, the Saab 18 was ordered into production in both bomber (B 18A) and reconnaissance (S 18A) versions.[2]

[edit] Operational historyThe B 18A entered service in June 1944,[1] and quickly became Sweden's standard medium bomber aircraft.[4] As license-built Daimler-Benz DB 605 liquid-cooled, inline engines had become available, they were incorporated into the improved Saab 18B, which first flew on 10 July 1944.[2]

Ordered into production as the B 18B dive bomber, the 18B design was further developed into the T 18B, which was planned to be a torpedo bomber variant.[2] Due to difficulties with the torpedoes, however,[1] the T 18B was instead developed into a heavy ground-attack aircraft, mounting a Bofors 57-millimetre (2.2 in) cannon under the nose.[2]

By the late 1940s, the third crewmember's position had been eliminated, reducing the crew of the aircraft to two; the provision of air-to-ground rockets and improved bombsights had removed the requirement for a bombardier. By this time the Saab 18 had established a reputation for suffering a serious rate of attrition, and this led to the decision to outfit all of the surviving aircraft with ejection seats for the pilot and navigator/gunner.[5]

Production of the Saab 18 totaled 245 examples,[6] with the last T 18B being delivered in 1948. Used in trials of early Swedish air-to-surface missiles,[1] the Saab 18 remained one of Sweden's frontline ground attack and reconnaissance platforms until the late 1950s, when it was replaced by the jet-powered, swept wing Saab 32 Lansen,[7] the B 18B and T 18B being replaced by the A 32A in 1958,[1] with the last S 18As being replaced by S 32Cs
Specifications (B 18B)Data from [1][2]

General characteristics

Crew: 3 (pilot, navigator/gunner, and bombardier)
Length: 13.23 m (43 ft 5 in)
Wingspan: 17 m (55 ft 9 in)
Height: 4.35 m (14 ft 3 in)
Wing area: 43.75 m2 (470.9 sq ft)
Empty weight: 6,100 kg (13,448 lb)
Max takeoff weight: 8,800 kg (19,401 lb)
Fuel capacity: 1,700 litres (370 imp gal; 450 US gal)
Powerplant: 2 × Daimler-Benz DB 605 inverted-vee piston engines, 1,100 kW (1,475 hp) each
Performance

Maximum speed: 575 km/h (357 mph; 310 kn)
Range: 2,600 km (1,616 mi; 1,404 nmi)
Service ceiling: 9,800 m (32,152 ft)
Armament


Guns: one 7.92mm fixed forwards-firing gun in wing root; two 13.2mm defensive guns.
Rockets: 8 air-to-surface rockets on underwing stubs
Bombs: 1,500 kilograms (3,300 lb) in internal bay