The Swedish Air Force before World War 2 – or the frantic search for the right modern fighter aircraft


When in 1939 it was clear that it was only a matter of time before a new major war would break out in Europe, Sweden, in common with many other countries, was ill-prepared for what was to come. This was particularly so in the case of combat aircraft. During the inter-war period Sweden had a number of minor aircraft manufacturers who had put forward several promising proposals, and the ASJA company had even built the J6 Jaktfalken, for its time a modern biplane fighter that was a good competitor relative to foreign manufacturers. However only a small number were built and the Swedish Air Force lacked the interest and money for more to be made.

The Swedish fighter situation had really lagged far behind. For a long time the focus had been on bomber aircraft, above all light bombers. The idea was that one could destroy the opposition’s fighters on the ground, so that no fighter aircraft were needed. “The bomber will always get through”. However many fighters one had, the bombers would always prevail, even though some would be shot down on their way. Also in the 1930s bomber aircraft were faster and more modern than fighters. New designs made use of aluminium skinning, more powerful engines and all were monoplanes. The fighter aircraft meant to stop them were still usually biplanes, often with open cockpits and armed with two machine guns above the nose, a style that had not changed since the First World War. One of the reasons why biplanes were still popular was that they were more manoeuvrable than monoplanes, and many believed that manoeuvrability was more important than speed and firepower.

A Gloster Gladiator in swedish colours. Photo: Flygvapenmuseet (Swedish Air Force museum)

Sweden had one fighter unit, No. 8 Wing based at Barkarby near Stockholm. In 1939 it was equipped with the relatively new British fighter, the Gloster Gladiator, with Swedish designation J8, where “J” stood for Jakt, meaning fighter. The Gladiator was somewhat of a hybrid, with one foot in the First World War dogfights and the other in the future. It was a biplane, as were many of its fighter predecessors, and thereby a conservative design. Its armament consisted of four machine guns. The Gladiator had some modern details, such as an enclosed cockpit, which made for more pilot comfort, but had a fixed undercarriage which increased drag.

.However during its evaluation in the mid-1930s the Swedish Air Force had considered that biplanes were more suited to the Swedish military’s often grass-covered airfields. As it was at that time the most advanced biplane, so the Gladiator was chosen. Altogether Sweden acquired 56 of them up to 1939. But at the same time that the Gladiator was introduced in Sweden, Great Britain amongst other countries was bringing out new fighters that were monoplanes, such as the German Messerschmitt 109 and the British Hawker Hurricane. These aircraft had retractable undercarriages and were faster and heavier armed than the Gladiator. Even more importantly, they were faster than the contemporary modern bombers and carried sufficient armament to destroy a modern bomber aircraft.

Fighter aircraft purchasing in the shadow of war

Thus it was at the 11th hour that Sweden realised that the Gloster Gladiator had not been the right choice. So in 1939 began a febrile search for a modern alternative somewhere overseas. Interest fell upon the USA, since the European manufacturers were fully engaged in arming their own countries’ air forces, and none of them wanted to sell their products to Sweden. It turned out that Nils Söderberg, who since 1938 had been the head of department at the Aviation Administration had visited the Seversky factory in 1937 and there made the acquaintance of the Seversky P-35, a monoplane fighter with an enclosed cockpit and all-metal construction, which had been launched in 1935. Söderberg had already, at the time the Gloster Gladiators were procured, proposed that the Seversky P-35 should be acquired instead, but this proposal was rejected on cost grounds. Now Seversky was contacted again and they offered their improved version, the Seversky EP-106 Guardsman (also known as the Seversky EP-1) of which 15 were ordered in May 1939, and were assigned the Swedish designation J9. In October 1939, after the war had started, a further 45 aircraft were ordered and in January 1940 60 more. The last batch was intended to equip a fighter group that was to be established to defend Gothenburg.

 The USA already considered the Seversky EP-106 to be an obsolescent design, so the question is why did Sweden choose this particular aircraft. Was it a question of money, or that even the USA wanted to make sure that its own air force above all received the latest aircraft? One aspect that could have played a part was that Seversky was able to deliver immediately, which was of course important. The first aircraft were ready for delivery in December 1939 after the Swedish engineer Bo Lundberg had inspected and approved them. We shall meet Bo Lundberg again soon.

However getting the aircraft to Sweden was easier said than done. 16 of them had been unloaded and transported away from Trondheim just before the Germans attacked Norway on the 9th of April. Four boxed aircraft were captured by the Germans and 6 more managed to get to Sweden in some other way. It now became difficult to get the aircraft into Sweden, and this problem ended when the USA gave approval for the remaining aircraft to be delivered via the then Arctic port of Petsamo, at that time part of Finland. This was an adventure in itself whereby Finnish engineering troops helped to build a road along which the aircraft could laboriously be transported to Sweden on lorries.

So Sweden could only receive 60 out of the ordered total of 120 before the USA introduced an export ban on war material to Sweden, among other countries. Gothenburg received no J9s and the 60 aircraft it had were obliged to work hard throughout the war. But despite intensive use, there were still 51 J9s in service in 1945, which could be seen as a good rating for the aircraft’s functionality and durability, compared to the other types of aircraft that were used by the Swedish Air Force during the war.

Most of the aircraft impounded by the USA ended up in the Philippines, where they met a sorry fate when they were forced to fight against numerically and technologically superior Japanese aircraft after December 7, 1941, and over time were all destroyed. Only three examples of the Seversky EP-106 remain today, and all three derive from the 60 aircraft that were successfully delivered to Sweden.

The J10, engine problems and Italian second class aircraft

In connection with the purchase of the J9, Sweden also ordered spare engines for the aircraft. These were the tried and tested Pratt & Whitney R-1380 Twin Wasp variant R-1380-SC-3-G (abbreviated to TWC-3) of 1,065 horsepower. In February 1940 Sweden placed a fresh order in the USA, this time with the manufacturer Vultee, who had just launched a new fighter aircraft, Vultee P66 Vanguard. Sweden was the first out of the gate and quickly ordered 144 aircraft before several problems with the prototype had been rectified! There was no longer time to wait.

In connection with this large order for what would become the J10, Sweden also ordered a large quantity of Twin Wasp engines, partly as reserves for the J9 and J10, and also for forthcoming Swedish aircraft projects. Therein was namely a problem, and this was that Sweden no longer had any domestic manufacturing facility for manufacturing high performance aircraft engines.

However things were going just as badly as with the second J9 series that had been ordered in 1940. When finally all 144 J10s were ready for delivery in September 1941 the weapons embargo had come into force. Not one single J10 had found its way to Sweden and only a handful of the ordered Twin Wasp engines had arrived. There, then was Sweden with a negative number of 204 of her ordered fighter aircraft and hardly any engines. Without these engines Sweden couldn’t build any of her planned fighter aircraft either, which made the deficiency even more dangerous. This led to a bold and quite controversial decision by the Swedish Government, to which we shall return.

Two Fiat CR 42 aircraft flying over the Mediterranean. In Sweden this type was designated J11.

Sweden was now forced to buy aircraft from one of the few nations that were willing to deliver, such as Italy. Italy was a participant in the war, so even in this case Sweden had to make do with second class aircraft. Among other things it became another biplane, the Fiat Cr 42, that was ordered for No. 9 Wing in Gothenburg, designated J11, and the Reggiane Re2000 that became the J20 issued to No. 10 Wing at Ängelholm. The designer of the Re 2000 had acquired much inspiration from the Seversky P-35 and this was clearly apparent in the lines of the aircraft, which however was not to the liking of the Italian Air Force.

Sweden also eventually purchased the twin engined Caproni 313 bomber and reconnaissance aircraft which became the B16 (bomber) or S16 (reconnaissance). After a number of fatal accidents due to the aircraft not tolerating the Swedish winter climate, a major rebuilding programme was undertaken. In defence of the Capronis it must be said that the Swedish Air Force did not take into account either that the aircraft were designed for use in a warmer climate and not at all intended to stand outside during cold and damp Swedish winters.

The Reggiane Re 2000, known in Sweden as the J20, which was, until the J22 entered service, the fastest fighter in the Swedish Air Force.

Thus the Swedish Air Force had to make the best of the situation with a really motley selection in its aircraft fleet, which in itself went directly against all reasonable logical thinking and that was far from what was wished for.

In connection with Sweden’s hunt for fighter aircraft, contact was even made with the Soviet Union. The USSR was engaged in the development of a new fighter, the Yakovlev Yak-9 which looked to be very promising. But in the end, the Soviet Union could only offer the obsolescent I-16. They were rearming for a forthcoming war too, and also the Yak-9 was not ready. The first prototype only first flew in 1942 but when it finally reached the squadrons it showed that it could match or even exceed all expectations. This aircraft was more than a match for the German Luftwaffe’s best machines and contributed to breaking the German aerial dominance on the Eastern Front.

However the strangest episode, which is at the same time the most interesting to think about, is that Sweden, by means of the Japanese air attaché received an offer to copy a variant of the Mitsubishi A6M, an aircraft that achieved fame under the name of the Zero. Details of the whole story are somewhat vague, but is seems that both direct imports and possible Swedish production under licence came up in the discussions. The whole idea was probably shelved on the grounds that it would not be possible to guarantee shipments from Japan, especially after Japan attacked the USA at Pearl Harbor on December 7th, 1941.

Two Mitsubishi A6M Zero aircraft flying over China.


The Swedish dilemma

The situation for the Swedish Air Force in 1941 was thereby worse than had been expected. To be sure, SAAB was developing aircraft, and by 1939 had produced a proposal for a new fighter aircraft, but when came down to it, SAAB was actually full up with bringing out the B17 light bomber and working on the larger twin-engined B18 bomber. SAAB could not accept any more orders, without halting progress on other projects that were also very important to the Air Force.

Above all this was another dire problem, namely the shortage of modern aircraft engines. SAAB could produce remarkable aircraft, but without engines they would be just on paper. The emergency purchase from the Italians could only provide a brief respite and would not solve the basic problem even for a short time.

It looked pretty dark for Sweden and the Swedish Air Force. It would take extraordinary measures to find a solution. Nils Söderberg was one of the decision-makers wrestling with the problem. Of course there were a number of smaller aircraft manufacturers in Sweden apart from SAAB, but apart from the fact that there were no engines, all the available aluminium was needed for SAAB’s production of the B17 and later the B18.

However Nils Söderberg had contacted Bo Lundberg, who had previously worked for Sparmann Workshops and later Götaverken and sketched out two Swedish aircraft projects, in brief named the GP8, a bomber, and GP9, a fighter. He had been involved in the purchase and quality assessment of the aircraft purchases in the USA. When the threat of an American arms embargo started to appear, Bo Lundberg was asked to find a solution and he presented a proposal for a new Swedish fighter aircraft. When he returned to Sweden from the USA in October 1940 he carried with him a draft of what would become fighter aircraft project P22.

The engine problem would have to be resolved in another and more radical way. Desperate times demand extraordinary solutions.

The STWC-3, or the Swedish Twin Wasp

In conjunction with Sweden’s large orders of aircraft and engines from the USA, the small Swedish aircraft engine company Svenska Flygmotor (SFA) began to plan for licensed production of Twin Wasp engines for SAAB. However when the USA imposed an embargo to prevent sales of war material to other countries including Sweden, that decision included licensing rights. This dashed the hopes of licensed manufacture, but Sweden desperately needed aircraft engines, otherwise none of her projects could be realised.

The lack of modern aircraft engines led to several Swedish projects, the SAAB B17, SAAB B18 and even the FFVS J22 being severely delayed. It therefore didn’t matter how quickly the constructors worked. Without engines series production could not begin. In the desperate situation that applied after the USA had implemented its embargo against Sweden in 1940 and the fact that there was no tendency to cancel the embargo in sight, Svenska Flygmotor was given a new task. This was namely to begin Swedish manufacture by copying the TWC-3 on the basis of existing examples. In other words, pirate copying. Pratt & Whitney would hardly appreciate this course of action, especially as it was a question of future serial production of these copied engines. But needs must when the devil drives. The Swedish Government would have to deal with any problems that arose.

The engineers at Svenska Flygmotor set to work and started the arduous task of taking existing engines apart and measuring every part in meticulous detail. There were no drawings of any kind, so everything had to be created on the basis of studying existing engines. In addition they were forced to make the necessary machinery for manufacturing the parts.

Sweden waits, purchases second-hand and makes a find near the end of the war

While waiting for its Swedish-built engines Sweden started to look for possibilities of obtaining existing Twin Wasps. Finland was doing the same, and it is not clear to what extent the two countries co-operated or haggled over the same engines. Anyway, Sweden found out that Germany had taken a batch of brand new Twin Wasp of the same type as those sought by Sweden as war booty during the invasion of France in 1940. Now started the task of persuasion, and it took until June of 1943 before Sweden gained access to a total of 115 engines. These played a key role in finally proceeding with Sweden’s aircraft projects.

The Swedish Warbird Society owns such a war booty engine which can now be seen here at the Aeroseum. The engine has some Pratt & Whitney markings and others in French.

In 1942 Svenska Flygmotor was able to test run a prototype of their engine and in 1943 could present the finished product. The Swedish Air Force was very satisfied and ordered 567. Finally Sweden could start serious production of several aircraft types, including some that had already been built but not in the quantities originally desired. The Swedish-made engines were called STWC-3 where the “S” stood for Swedish. It was an engineering marvel and Svenska Flygmotor had even managed to improve on the original design so that the Swedish copies had somewhat better performance than the originals.

Even Finland bought in the Swedish engines to power her own design, the Myrsky fighter, so the engines also went for export.

After the war the situation that had been feared came to pass. Pratt & Whitney were not at all pleased with the pirate copying. This was however complicated by what Sweden also saw as American pirate sales, of the Bofors 40 mm anti-aircraft cannon. Bofors had sold the licensing rights to the USA, but only for that country’s own needs. The USA had however sold and “lent” a large number of such cannons, not least to Great Britain, which according to Bofors was a breach of contract. Bofors had tried already during the war to get compensation via the American courts, but initially had no success. So Svenska Flygmotor decided it would be best to try to make things right on its own and sent a delegation to Pratt & Whitney. The delegation had taken with them an offer to pay for licensing in arrears for whatever amount Pratt & Whitney would want. This gesture of sincere honesty touched the Americans to the extent that they sold the licence retroactively for a symbolic sum. On top of this, the delegation received a promise that they could have whatever they wanted. The surprised Swedes couldn’t think of anything just at the time, but some years later needed some money to fit out a day room for the Military Academy aviation classes, which was being built. Contact was made with Pratt & Whitney to ask whether the offer was still valid, and it was. Pratt & Whitney therefore paid for all the fittings in the day room.

Sweden found a bargain in the second-hand market during the last year if the war. The USA had already before the war ended redundant aircraft, so that Sweden could now buy modern fighters such as the North American P51D Mustang cheap! The first arrived in Sweden on April 10th 1945, one month before the end of the war. Between 1945 and 1948 Sweden would purchase a total of 161 examples of this aircraft, which many regarded as one of the all time best propeller-driven aircraft. But it was obvious already in 1945 that the propeller-drive aircraft era was over and that jet aircraft were the future.

The Twin Wasp experience came to be useful to Svenska Flygmotor that in time turned into Volvo Aero. The Swedish aviation industry now entered the jet age and with the long experience of SFA in licensed production and its ability to improve on existing products made them an important part in what came to be an advanced domestic aviation industry well able to compete with the major powers.