Assisted by Ing. Zrnić, the design team initiated the design of a single-wing fighter that would be a marked improvement over the biplane fighters then in use. They began work in 1936 under strict secrecy. Wind tunnel testing work was carried out in France, before they submitted the design to the Yugoslav Air Ministry, who then approved construction of a single prototype. Construction of the IK-3 was assigned to Rogožarski A. D. in Belgrade.
Prototype
The prototype first flew in the spring of 1938.
The IK-3 prototype was powered by a Hispano-Suiza 12Y-29 liquid-cooled supercharged V12, rated at 890 hp (664 kW) for take-off and at 920 hp (686 kW) at 11,810 feet (3600 m) altitude. The prototype was armed with one 20 mm Hispano-Suiza HS-404 cannon and two 7.92 mm FN-Browning machine guns mounted over the engine in the forward fuselage. The aircraft was of mixed steel tube, wood, and fabric construction with the retractable landing gear of Messier design. Its construction was similar to the British contemporary Hawker Hurricane fighter. Six test pilots flew the prototype in a mostly-successful test program (alterations were required to the retractable landing gear and to the engine installation) before the airplane was destroyed in a fatal crash. On January 19, 1939 the test pilot, Captain Milan Pokorni, after a series of aerobatic maneuvers, entered a terminal velocity dive from which he did not recover. The subsequent accident investigation could not find an aircraft-related cause for the accident, and the Yugoslav Air Ministry ordered an initial production lot of twelve aircraft.
IK-3 Production
Several changes were added to the production version of the IK-3:
More structural members were added to the rearward-sliding canopy enclosure;
Bulletproof glass was incorporated into the windshield;
Use of a Czech-built version of the Hispano-Suiza engine used in the prototype, the Avia H.S. 12Ycrs.
The first IK-3s were delivered in the summer of 1940 to an experimental fighter squadron whose pilots preferred it to the Messerschmitt Bf 109E-3 and the Hawker Hurricane, as the IK-3 was more maneuverable and could make tighter turns. Additionally, the aircraft was found to be very maintainable.
With the success of the IK-3, planning began for licensing manufacture in Turkey as well as increased production by Rogožarski - a second production batch of 25 aircraft were ordered. However, production of the second batch had just started when Germany invaded Yugoslavia on April 6, 1941.
Planned design improvements to the IK-3
As production of the IK-3 proceeded the design team was working on improved versions of the IK-3 and other designs. Among the IK-3 improvements in work was installation of a more powerful engine. Engines that were considered:
An upgraded 1,100 hp Hispano-Suiza 12Y-51;
The Daimler-Benz DB-601A;
The 1,030 HP Rolls-Royce Merlin III engine
Also, Rogožarski was pursuing a new fighter design, the IK-5 [1] , that was to be powered by two Hispano-Suiza 12Y engines. Two versions of the design were planned, a single seat interceptor and a two seat long range “destroyer” with heavy nose mounted armament. Models of the IK-5 had been tested in wind tunnels and construction of a prototype begun when the German invasion ended this and all other efforts.
The Ikarus S-49 fighter, prodced after the Second World War, was based on the IK-3.
Operational history
At the beginning of the April war, only 6 out of 12 IK-3 from the first production series were operational. One aircraft was lost in a fatal accident before the war (it dived into the Danube River under power; investigators concluded the pilot had blacked out), four were grounded for scheduled services and repairs and one aircraft was undergoing modification to Series II IK-3 standard in the Rogozarski airplane factory. The six remaining IK-3s were assigned to 161st and 162nd fighter squadron (3 IK-3 each) of the 51st Fighter group. The 51st fighter group was part of the 6th fighter regiment of Royal Yugoslav Air Force which was tasked to defend Yugoslav capital, Belgrade. Both fighter squadrons were stationed at Zemun airport. One source [2] states: " . . the IK-3s put up a valiant resistance against the Luftwaffe, scoring a number of "kills" before they were finally destroyed in combat." Another source [3] claims 11 victories for the IK-3, with Narednik (Flight Sergeant) M. Semiz as most successful (4 victories).
General characteristicsCrew: 1
Length: 27 ft 5 in (8.38 m)
Wingspan: 33 ft 10 in (10.33 m)
Height: 10 ft 8 in (3.23 m)
Wing area: 179 ft² (16.6 m²)
Empty weight: 4,123 lb (1,874 kg)
Loaded weight: 5,291 lb (2,405 kg)
Powerplant: 1× Avia-built Hispano-Suiza 12Ycrs V-12 liquid-cooled engine, 920 shp (686 kW)
Performance
Maximum speed: 327 mph (526 km/h) at 17,715 ft (5,401 m)
Range: 310 miles (496 km)
Service ceiling: 26,250 ft (8,000 m)
Wing loading: 29 lb/ft² (113 kg/m²)
Power/mass: 0.17 hp/lb (0.29 kW/kg)
Armament
Guns:
1× 20 mm Hispano-Suiza HS-404 cannon
2× 7.92 mm FN-Browning machine guns
