I will try to stay focused on the technical aspects of the J22 and not wander
off too much about the background and the issues that led to the development of
the J22.
But without the basic understanding of the issues that played a major part in
the Swedish aircraft industry in the 1940's, it would be difficult to understand
why this aircraft was developed in the first place.
Background
During WWII Sweden was cut off from most military supplies. The aircraft; Vultee
48C Vanguard which Sweden had ordered from the USA, could not be
delivered due to the War situation and they needed to come up with alternate solutions.
SAAB was busy working on their two bomber projects, the B17 and B18, and also one
fighter/attack
aircraft, the J21.
There was a need for a decent fighter to fill the gap created when the order from the USA
fell through.
Mr. Bo Lundberg was a Swedish Aircraft designer and an Airforce officer
who was working for the
Swedish Air Commission as an Aircraft Inspector at Vultee Aircraft in
San Diego, CA. He was overseeing the production of the 48 C Vanguard which was
supposed to be delivered to the Swedish Airforce.
He was approached by the Swedish Government's procurement office through General
Nils Söderberg to develop a fighter design for the Swedish Airforce. Fortunately, he already had a project that he had been working on for some time, which was called
GP 9.
To make a rather long story short, the Swedish government decided to go for his project
and the design work started in 1941.
Due to the shortage of aircraft material, such as 2024 T3 Aluminum and other crucial
components, the structural design of the aircraft came to be rather unconventional.
Saab had already allocated all the available aluminum for their aircraft. It was
decided that all the materials and components for this new project had to come
from domestic sources.
The basic structure of the aircraft was a Chrome molybdenum steel tube truss, welded together and then covered with load carrying laminated wooden panels. Some of the panels were removable for inspection and for replacement.
The single primary wing spar was also a welded truss assembly. The inner part stretched from one half of the wing to the other half of the wing. Outboard of this was
a sheet metal structure that was bolted on the inner spar structure. The spar caps were
tapered steel
tubes and due to the machines that produced the tubes, the wing spars could not be made in one piece.
The Engine was a copied Pratt and Whitney R-1830 SC3-G, rated at 1050Hp at 2700rpm, 42" of manifold pressure. This engine was called STWC-3G in Sweden.
This was the only available engine at the time. Bo Lundberg knew that the
available power was marginal for a new fighter design, but there were no other
choices. Much emphasis of the aerodynamic design was to reduce drag in order to
get performance equivalent or better than the best fighters available in 1940-41;
The Spitfire Mk II and the Messerschmitt BF 109 E and F.
The first 150 J 22's had a "regular" P&W R-1830 though, and these engines were bought from the Germans who in turn had
acquired them as War Trophies from the French, as the French were using them for their Curtiss
H75/P36 Hawk's.
The first flight was September 20th, 1942.
The aircraft was very fast. It was known as "the fastest aircraft in the world in
reference to engine power". It could reach 318mph at S.L. and 357mph at 11,500ft
at WEP (War Emergency Power, or Combat power), and 348mph at 14,120ft. Not bad
for 1050hp! After the war when higher octane fuel was available the speed at
S.L. increased to 332mph, while speeds at altitude remained the same.
Compared to the Spitfire Mk1a and the Messerschmitt 109E-3/4, it was about 20-40 mph faster. These aircraft had about the same horsepower.
The problem, though, was that when the aircraft entered service, in October 1943, it was
slightly underpowered compared to the competition, as predicted, but it could
still hold its own if the fight was at low to medium altitudes. Above 15,000ft
it was no match for the later designs as the P-51 Mustang, Spitfire Mk XIV and
Me 109-K. Even for such prominent fighters as the FW 190A-4 through A-6, which
were in service in 1943, it would have been a fairly well balanced match, as we will
see later in the fighter comparison section.
In 1943 the British had the Spitfire Mk Va and later that year the Mk IX. The Mk Va was able to reach a speed of 370mph and the
early Mk IX was able to reach a speed of
390mph. These speeds were reached at 20,000ft. The Germans had their Messerschmitt 109F and,
later on, the G versions which were able to reach about the same speeds as the Spit's. All these aircraft had engines with 1250-1450hp.
The interesting comparison, which we will talk more about later, was that the
J22 was equal or better to most aircraft in 1943 from S.L. up to 15,000ft.
Above that altitude the speed dropped. If the J22 would have been equipped with the
R-1830-86 (see theoretical J22-C), it would have been able to reach 390mph at
about 20,000. Thus equal to the Spitfire and Me 109F-G. Unfortunately this never
happened.
More about performance comparison later.
Nonetheless, the J 22 was a very nimble fighter and extremely maneuverable at altitudes up to 15,000ft.
Service Ceiling was 31,000ft and the absolute ceiling was about 42,000ft.
Due to the shortage of high octane fuel, the Swedish Airforce had to do with 87 octane for all their fighters. This limited the available horsepower of the engine and during the War, they could only get
1050Hp from the R-1830.
After the War, they were able to get 100-150 octane AVGAS and thus they could change to boost pressure and ignition timing to make it produce 1200Hp.
The Swedish Airforce used the J22 from 1943 to 1952 and they were replaced by, among others the J26 (P-51D) Mustang.
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