On 18 May 1940 — exactly 86 years ago today, and a week after the German invasion of the Netherlands — a single-engined dive bomber lifted off the runway at Linköping, Sweden, and entered an aviation history that almost nobody outside Sweden remembers. The aircraft was the Saab 17. It would become the first all-metal Swedish military aircraft, the workhorse of the Swedish Air Force during the Second World War, and — eventually — the first Saab export. It would also be the first time the modest Linköping aircraft factory became a name that meant something in international aviation.

Sweden was officially neutral throughout the war. The Saab 17 was the aircraft that made neutrality credible: a reconnaissance bomber, fast enough to escape interceptors and ranged enough to reach any approaching threat. It was the first time Sweden could defend itself without buying foreign aircraft. And it set the template — domestic design, world-class engineering — that would lead to the Tunnan, the Lansen, the Draken, the Viggen, and eventually the Gripen.

A Swedish aircraft for a Swedish war that never happened

Sweden in 1939 had a problem. Its Royal Swedish Air Force, the Flygvapnet, had been formed only in 1926 and was reliant on imported British, German, and American aircraft. As war loomed, every country Sweden bought from suddenly needed its own aircraft and refused export licenses. The Flygvapnet faced the prospect of being grounded by supplier embargo at precisely the moment Sweden’s strategic situation looked most exposed.

Saab — formally founded only in 1937 — was asked to design a domestic dive bomber from scratch. The brief was demanding: all-metal stressed-skin construction (Sweden had little aluminium-aircraft fabrication experience), capable of carrying a 500-kilogram bomb load, capable of operating from short, rough Swedish airfields, capable of being adapted for reconnaissance and torpedo roles. The aircraft had to be designed, built, and in operational service within thirty months. Chief designer Frid Wänström delivered.

The clever bit: a landing gear that doubled as a dive brake

The most distinctive engineering feature of the Saab 17 is also the cleverest. Like most of its dive-bomber contemporaries — the Junkers Ju 87 Stuka, the Aichi D3A, the Vultee Vengeance — it had fixed landing gear in its production form. Unlike them, the Saab 17’s fixed gear served a dual purpose. The main wheels were enclosed in large faired spats, and the spats themselves were rotated by hydraulic actuators to act as a dive brake during the bombing run. When the pilot pushed into the dive, the spats rotated 90 degrees to present a flat face to the airflow, slowing the aircraft to the target accuracy speed of approximately 300 km/h. When the pilot recovered, the spats rotated back to streamlined position.

It was a beautifully Swedish solution. Instead of adding weight by fitting dedicated dive brakes — as the Stuka did with its Schräger Sirenen “Jericho trumpet” arrangement — Saab made the landing gear do the job. The result was an aircraft of marginally lower top speed than its German rival but with comparable dive-bombing accuracy and significantly lower mass. It was the first time a Saab engineering team showed the kind of sideways thinking that would later define the Draken and Viggen.

War on skis, war on floats

Swedish geography is brutal. The Flygvapnet needed an aircraft that could operate from forward dispersal airfields in winter — when most of Sweden’s northern airbases are snow-covered and runways unusable — and from coastal sites where the only available “runway” was a sheltered fjord. Saab adapted the 17 for both. The S 17BS variant fitted twin floats for water operations; the S 17BL variant fitted skis for snow operations. Both were operational by mid-1942. No other contemporary single-engined bomber was offered in three undercarriage configurations from the same airframe.

The Flygvapnet flew the Saab 17 across the war years primarily on training, patrol, and photo-reconnaissance missions. The aircraft saw no combat — Sweden remained neutral — but its presence in deployable numbers gave the Swedish government negotiating leverage with both the Allies and the Axis. The number of Soviet, German, and Allied aircraft that violated Swedish airspace during the war was significant; the number that did so without being intercepted by a Saab 17 was, eventually, almost none.

“We did not have the luxury of starting from a clean sheet of paper, and we did not have the luxury of waiting for ideal conditions. We had thirty months and an air force that needed to be re-equipped before it became irrelevant. Every shortcut we took, we took deliberately.”

Frid Wänström — Chief designer, Saab AB (in a 1972 interview about the Saab 17 programme)

Sold to Finland, sold to Ethiopia, retired by Sweden

When jet aircraft entered Flygvapnet service in the late 1940s, the Saab 17 became surplus. Sweden sold sixty examples to Ethiopia in 1947, which used them as the backbone of the Imperial Ethiopian Air Force’s strike capacity through the 1960s. A small number went to Finland and Denmark. The last Saab 17 in active military service was an Ethiopian airframe, retired in 1968 — twenty-eight years after the type’s first flight.

One Saab 17 remains airworthy today. The Swedish Air Force Museum at Linköping operates a single B17A — registration SE-BWH — that flies at airshows across Scandinavia. It is the only example of an aircraft type that taught Saab how to be Saab. Every Gripen, every Viggen, every Draken, every Tunnan traces its institutional ancestry back to a single-engined dive bomber that first flew in May 1940, when the only thing Sweden could be sure of was that it could no longer rely on anybody else.

Sources: Flygvapenmuseum Linköping, Saab AB historical archive, FlightGlobal, Swedish Air Force Historical Society.