DETLEF BILLIG COLLECTION
No. 10005. Saab B 17B (17005) Swedish Air Force
Photographed at Flygvapenmuseum, Linköping, Sweden, July 27, 2008, by Detlef Billig

Saab B 17B

09/30/2010. Following an Air Force evaluation of the two different projects submitted, one by AFF (Aktiebolaget Forenade Flygverkstader, United Aircraft Company), the other by ASJA (Aktiebolaget Svenska Järnvägsverkstädernas Aeroplanavdelning, Swedish Railroad Workshops Companies' Aeroplane Division), a contract for two L-10 light bomber and reconnaissance aircraft prototypes was awarded to ASJA on 29 November, 1938. After being incorporated on April 2, 1937, Saab (Svenska Aeroplan Aktiebolaget, Swedish Aeroplane Comapny) was restructured in March 1939 and took over ASJA, the L-10 became the Saab 17.

For the fledgling Swedish aircraft industry the Saab 17 represented a great technological challenge. It was the first all-metal, stressed-skin aircraft ever designed in Sweden. To make possible a rapid start for the development work, ASJA had augmented its engineering staff by hiring a total of 46 American designers and stress specialists in 1938-39. Their stay in Sweden, however, was to prove rather brief as most of them were called back to the United States when war began in Europe in September 1939. Their input of experience was very valuable, however, and significantly contributed to the excellent reliability of the aircraft.

The first prototype of the Saab 17 made its first flight at Trollhättan on 18 May, 1940, with the company's chief test pilot Claes Smith at the controls. The first prototype was powered by an 880 hp Bristol Mercury XII nine-cylinder air-cooled radial engine, the second by an 1,065 hp Pratt & Whitney R-1830 Twin Wasp fourteen-cylinder two-row air-cooled radial engine. Both engine types were license-built by Nohab (Nydqvist & Holm Aktiebolaget) at Trollhättan. Nohab became SFA (Svenska Flygmotor Aktiebolaget, Swedish Aircraft Engine Company) in 1941.

The aircraft had very sleek lines and many advanced design features, including flush-riveting for low drag. For maximum strength the centre section was designed without any cut-outs for the undercarriage. The rearward-retracting main undercarriage units and their covering doors were intended for use as air-brakes during dive-bombing, and the tail wheel was also retractable.

The aircraft was also almost unique in having a retractable ski undercarriage which actually produced less drag than the wheel type. Even the water-based version which was normally equipped with floats was converted to have skis in the winter. The floats were of the Edo type manufactured under license by Hagglund & Soner at Ornskoldsvik in Northern Sweden.

The fuselage, which had a roomy, high-visibility cabin for the pilot and observer/navigator/rear-gunner, contained an internal bomb-bay. The Saab 17 carried up to 1,543 lb (700 kg) of bombs of various sizes from 110 up to 1,102 lb (50 up to 500 kg). In the internal bomb-bay a 551 lb (250 kg) bomb, or eight 110 lb (50 kg) bombs could be carried. The armament comprised two 0.52 in (13.2 mm) M/39A machineguns in the wings and one flexible 0.311 in (7.9 mm) at the rear seat.

An early version of the aircraft used for classic dive-bombing tactics was equipped with a special 'fork', lowering the external carried 500 kg bomb free of the propeller arc. During the production life of the aircraft the Saab BT-2 'toss' bombsight became available, making dive-bombing obsolete. This also made the use of the undercarriage doors as air-brakes unnecessary. The reconnaissance version carried an N-2 camera in the fuselage.

The development and production of the Saab 17 was complicated by the problems of engine availability. Initially, the aircraft was planned for the Pratt & Whitney Twin Wasp. This version was designated B 17A in the Air Force. The Twin Wasp engine however did not become available until 1943-44, and therefore the first version of the aircraft to go into production was the B 17B powered by a Mercury XXIV of 980 hp. This engine also powered the seaplane version which was designated S 17BS.

In 1941 the Air Force was able to procure the Italian Piaggio P XIbis RC 40 of 1,040 hp which powered the B 17C version. The Wasp-powered B 17A thus became the last version to go into service. The engines in the B 17A and B 17B had Hamilton Standard variable-pitch propellers built under license in Sweden by Svenska Flygmotor. The Piaggio engines drove Piaggio P 1001 propellers.

In addition to the three prototypes, the Swedish Air Force ordered a total of 322 B 17/S 17s in four batches during the period December 27, 1940, to September 1, 1942. The first production aircraft flew on December 1, 1941, and the last delivery took place on September 16, 1944. The type was manufactured both in Linköping and at Trollhättan. In fact, only 55 of the 322 production aircraft were completely built at Linköping.

The production of the four versions was split as follows: 132 B 17 A; 116
B/S 17B (38 were delivered as seaplanes under the S 17BS designation); and 77 B 17C. The Air Force career of the Saab 17, which began in early 1942, was very distinguished and six light-bomber and reconnaissance wings were equipped with the aircraft. It was retired as a combat aircraft in 1948.

In the final phase of the Second World War it was feared that the German troops in Denmark (and Norway) would not obey Germany's order for total surrender. In Sweden the Danish Brigade, first organized in 1943, also included a number of Danish Air Force officers who in 1944 had been trained in the use of the Saab 17.

Fifteen B 17Cs were actually allocated to the Danish Brigade and were ready for deployment to Denmark and carrying Danish colors at the Swedish Air Force F 7 Wing at Såtenäs, but the order to fly to Denmark never came from the Danish Government. (In 1970 the Swedish Air Force presented a B 17A to Denmark as a gift and it is displayed in Danish markings at Egeskov Castle on the island of Funnen.)

In the period 1947-53 the Ethiopian Air Force, which had been organized by Swedish officers after the war at the request of Emperor Haile Selassie, eventually procured a total of 47 Saab 17As in three batches. Responsible for the organization of the Ethiopian Air Force was the Swedish Colonel Count Carl Gustaf von Rosen. The Saab 17s proved ideal for the rugged conditions in Ethiopia. In the late 1950s a number of Fairey Firefly attack aircraft were acquired from Canada in order to modernize the Air Force but these aircraft finished their service in Ethiopia well before the Saab 17s, which were still operating in squadron strength in 1960.

Even in the 1970s some Saab 17s were operating in Ethiopia after more than 25 years of service in that country. The Ethiopian Saab 17s had their main base at Asmara, 7,546 ft (2,300 m) above sea level. The Saab 17s endurance of more than 4 hours was vital in that part of the world. Ethiopia, with its many high mountains and few airfields, covers twice as large an area as the Netherlands, Belgium, the Federal Republic of Germany, Switzerland and Austria combined.

Starting in 1951, the Air Board released a number of Saab 17 As to serve as civil registered target-towing aircraft for the Swedish armed forces. The aircraft were still owned by the Air Board but operated by private companies, Svensk Flygtjänst (Swedish Air Service) and AVIA, the latter company based on the island of Gotland in the Baltic Sea.

Eventually, a total of 20 Saab 17s were on the Swedish civil aircraft register, most of these serving with Svensk Flygtjanst. Two S 17BS seaplanes were also in civil use during 1949-51 owned by Ostermans Aero AB. One ex-Svensk Flygtjänst target-towing 17A was sold to Austria in 1957 and two years later two similar aircraft went to the Finnish Air Force..


Created September 30, 2010