My entry for this challenge, again hanging this on my nebulous proto-AU Bereznik:
Following the devastation of the Second World War which saw Bereznik almost defeated by the combined Iron Pact members, of Germany under Hitler's Nazi Party and Stalin's Soviet Union, the Bereznik air force had to be rebuilt and modernised along with the rest of the nation.
Three fortuitous events enabled the creation of a modern jet fighter;
Pavel Sukhoi, who had been chief designer at the Minsk AK before the war, returned from his enforced absence in the United States in 1945 and began rebuilding a design team as the devastated Minsk factory was rebuilt.
The new Attlee Labour government in Great Britain had also agreed to sell Brezenik 50 of its latest Rolls-Royce Derwent and Nene centrifugal-flow turbojets and more importantly a production licence.
Third, in the occupied Eastern Zone of Germany was a veritable load of aeronautical plunder; designers from Junkers who found employ under Sukhoi, aerodynamic research data on swept wings and fuselages, alternative jet-engines in the form of the Jumo 004 and machine tools and jigs to re-equip the destroyed Bereznik factories.
Sukhoi's work on the S-9 began in 1946 but it took time to refine the design. While Sergei Tumansky's company Tumansky KAR was trying to get to grips with the Jumo 004, the Ternow KsRR aircraft engine factory was built in Ternow during 1947 with British assistance to build the Derwent and Nene turbojets. Impressed by its greater power and reliability, Sukhoi selected the Derwent, manufactured as the RD-50, for the S-9. Problems with finding suitable alloys and fabricating parts meant that most of the initial S-9 production series had British-made or RD-50 engines with British-made turbines. The first prototype did not fly until 25 March 1949 but a hundred S-9 fighters were soon in production, enabling General Bereznik to boast that his air force had modern jet fighters during the summer parades of 1950.
From 1950, the S-9A became the main production model with a few changes to improve reliability and a new frameless plexiglass canopy which had proven difficult to develop. Just over 900 were built, some being supplied to Hungary during 1950 to re-equip their fighter force. Plans to licence-build the S-9A in Czechoslovakia came to nothing.
From 1953 many were updated to S-9A1 standard with PR-3 IFF, ASR-9B gyro gunsights and improved radios and two underwing plyons were added for 500kg bombs or large rockets. Some also received up0rated RD-50A engines. Increasingly obsolete as the 1950s continued, efforts were made to sell surplus S-9As to the Middle East, but buyers instead found favour with the superior Nene-powered Sukhoi S-11.
The air force as early as 1949 had foreseen the need for a jet conversion trainer and Sukhoi developed a basic design with the addition of a seat and cockpit for the instructor replacing the main forward fuel tank and one cannon was removed to make room for the re-located radios. The cockpit was cramped and visibility for the instructor poor, but many of these S-9T trainers were built pending more suitable purpose-designed trainers and they served well into the 1960s.
The air force leadership soon turned its attention to all-weather interception given the poor weather conditions which meant day fighters were limited in their ability to find their targets all-year round. Sukhoi in early 1950 was asked to investigate fitting the new RP-2 'Lightning' radar to the S-9. The radar was surprisingly compact for an early generation set, but offered little more than a modest search facility with its main use for ranging. The pilot workload was high. Sukhoi made few structural changes to the S-9N other than enlarging the cockpit 'bullet' in the intake to accomodate the radar electronics and the scanner was placed in a new nosecone, the intake being given bulged 'cheeks' to maintain the same airflow to the RD-50A engine. The windscreen was also modified to allow better rain dispersion and more room for the ASR-7 gyro gunsight. Only around 300 were built, 24 being exported to Hungary.
From 1953 many were updated to S-9N1 standard with PR-3 IFF, ASR-9R gyro gunsights and improved radios and uprated RD-50A engines.
During 1951, Świdnik ZA was established as an additional state-owned factory and repair centre. With Sukhoi's design team increasingly overworked Świdnik was given the task of further developing the S-9 as a ground-attack aircraft. The S-9 was deemed ideal as stocks of RD-50A engines existed and high performance was not required. This work was overtaken by the need to develop an escort fighter for the long-range bomber fleet in the early 1950s. Świdnik's design team had to pack as much fuel as it could and the newer RP-5 'Spear' radar into the S-9 airframe. The nose intake was replaced by bifurcated cheek intakes under the wing-roots, the large RP-5 occupying the nose. Extra internal fuel tanks were fitted as will as external slipper tanks under the wings. The planned armoured cockpit and revised undercarriage for short field operations was retained. The armament was revised with four 20mm cannon and two underwing pylons could be fitted along with the slipper tanks. The prototype S-9D made its maiden flight on 4 May 1953 and production at Minsk AK followed soon after. Less than 200 were built as newer designs materialised quicker than originally expected, but they served a useful role as long-range interceptors until the early 1960s.
Świdnik having retained many features of the planned S-9G in the S-9D lobbied to fulfil its original goal of a ground attack aircraft. The resulting S-9S was essentially a S-9D without the RP-5 radar and with the addition of two cameras for tactical reconnaissance and four weapon pylons, although slipper tanks could also be fitted. 500 were built and formed the bulk of the fighter-bomber fleet until the 1950s with some going to Hungary and Romania.