Ikarus S-49: Born out of Necessity

thanosaekk · October 22, 2023, 1:45am

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Ikarus S-49, Yugoslav Air Force, 1950-1961
Part of the Yugoslav Air Tree suggestion

Introduction:
The Ikarus S-49 was Yugoslavia’s attempt to build something that could defend its airspace in the volatile years of the early Cold War. It followed the trajectory of the pre-war IK-3, but with new engines and armament depending on what Yugoslavia had available at the time. 158 were built in total.

Variants:
S-49 variants were distinguished by the last letter, which indicated which engine was used.

The S-49A was the initial production model, with mixed construction of metal and wood, a Klimov VK-105PF-2 engine, a ShVAK and two UBs, and no hardpoints for ground ordnance.

The S-49B would have housed a German DB 605A engine, but remained unbuilt.

The S-49C was the improved series variant, all-metal with a Hispano-Suiza 12Z17 engine, an MG 151, two .50 cals, and hardpoints for limited ground ordnance.

Other unbuilt concepts included the Allison-powered S-49D and Merlin-powered S-49E.

Specifications:
Crew: 1

Dimensions
Length: 8.42 m (S-49A) / 9.06 m (S-49C)
Wingspan: 10.30 m
Height: 3.20 m
Wing area: 16.60 m²

Mass
S-49A
Empty: 2,326 kg
Max take-off: 2,950 kg

S-49C
Empty: 2,818 kg
Max take-off: 3,568 kg

Propulsion
S-49A
Engine: Klimov VK-105PF-2
Engine power: 956 kW (1300 hp)

S-49C
Engine: Hispano-Suiza 12Z-17
Engine power: 1103 kW (1500 hp)

Performance
S-49A
Maximum speed: 554 km/h
Climb rate: 4000m altitude achieved in 3 min, 54 sec (-> 17.1 m/s average)
Range: 690 km
Flight ceiling: 9,500 m

S-49C
Maximum speed: 628 km/h
Climb rate: 6000m altitude achieved in 6 min, 54 sec (-> 14.5 m/s average)
Range: 800 km
Flight ceiling: 10,000 m

Armament
S-49A
1 x 20 mm ShVAK
2 x 12.7 mm Berezin UB

S-49C
1 x 20 mm MG 151 (100 rpg)
2 x 12.7 mm M2 Browning (140 rpg)
2 x 50 kg bombs or 4 x 127mm HVAR rockets

History:

The end of World War II found Yugoslavia’s aviation industry effectively destroyed. The post-war Yugoslav Air Force was made up from a mix of foreign aircraft: the majority were Yak fighters from the Soviet Union (Yak-1, Yak-3, Yak-9), some were British Spitfires and Hurricanes, and a few were Bf 109 Gs that were withdrawn from service in 1947. However, the Tito-Stalin split of 1948 ended all deliveries of Soviet fighters or spare parts for the maintenance of existing fighters to the JRV. Thus, the domestic air industry that was only starting to recover would have to fend for itself.

Kosta Sivčev had been one of the three designers of the pre-war IK-3 fighter aircraft, and accepted the task of developing a new piston fighter for the air force. Thanks to technical documentation that survived the war, he started working on the design of a new plane together with Slobodan Zrnić and Svetozar Popović, that was effectively a development of the IK-3. The old fighter was reconstructed to house the only available engine, the Klimov VK-105PF-2 of which 45 remained in Yugoslavia for the maintenance of Yak-3s. Its armament would also correspond to the Yak-3, as it included a central 20mm ShVAK and two 12.7 Berezin UBs. The upper part of the rear fuselage was re-designed.

The resulting plane, the S-49A, was a distinct evolution of Yugoslavia’s pre-war fighter despite its resemblance to the Yak-3. The design was rapidly completed in three months and the prototype flew already in 1949, with the production order being given before the tests were even complete. The first deliveries were on May 21, 1950. In total, 45 S-49As were produced - the same as the number of VK-105PF-2 engines available in Yugoslavia’s inventory.

Due to the limited number of Soviet engines and the need to produce more planes, an alternative engine would have to be used. Options from every Western power were examined, including the DB 605A, the Allison and the Merlin, but finally the French Hispano-Suiza 12Z17 with 1500hp was chosen to power the new series of fighters, the S-49C. First flying on August 23, 1952, the S-49C featured a number of other improvements: an all-metal construction, multi-role capability with 50kg bombs and HVAR rockets, as well as an entirely new armament suite: the ShVAK and Berezin UBs were replaced by a 20mm MG 151 and two 12.7mm Brownings respectively. 113 S-49Cs were built in total.

The S-49A and S-49C served in the Yugoslav Air Force throughout the 1950s, and though outdated, they were the best the country could achieve. The last were retired in 1961, and by that time the JRV had acquired its first American jets, while also experimenting with its own domestic jet designs.

Gallery:

Gallery

S-49A

S49A 1