Rogožarski IK-3

The Rogožarski IK-3 (Serbian Cyrillic:Рогожарски ИК-3) was a 1930s Yugoslav low-wing monoplane single seat interceptor fighter with retractable landing gear, and was designed by Ljubomir Ilić and Kosta Sivčev as a successor to their IK-1/IK-2 fighter. It was regarded as a generally effective aircraft, easier to handle than the contemporary Messerschmitt Bf 109E and Hawker Hurricane Mk.I.

Design and development
Development of the IK-3 was initiated in 1936 as a replacement for the IK-2 parasol monoplane then is use, with the intention of providing a significant improvement in performance. Wind tunnel testing was carried out in France before being submitted to the Yugoslav Air Ministry, who approved construction of a single prototype. Construction of the IK-3 was assigned to Rogožarski A. D. in Belgrade.

The first prototype IK-3 was completed in the spring of 1938 and the first flight was achieved on April 14, 1938 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 and was armed with one 20 mm Hispano-Suiza HS-404 cannon and two 7.92 mm FN-Browning machine guns mounted over the engine. It was of mixed steel tube, wood, and fabric construction with a Messier retractable landing gear.

After the initial test flights proved successful, the prototype of IK-3 was transferred from Test group ("Opitna grupa") to the 6th Fighter Regiment where further tests were conducted. During testing on 19 January, while attempting a high speed low level pass the starboard wing structure failed causing a fatal crash, likely as a result of damage sustained during a heavy landing earlier in the day.

Subsequent investigation concluded that the failure occurred due accumulated damage on the wing spar near the wheel wells caused by several rough landings during testing. Comparative test flights during 1940 against Hawker Hurricane and Messerschmitt Bf 109E fighters, operated by the Royal Yugoslav Air Force, found the IK-3 to be an improvement over the Hurricane in general and more maneuverable than the Messerschmitt, but slower and with a poorer rate of climb.

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 same 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 over the Messerschmitt Bf 109E-3 and the Hawker Hurricane, as the IK-3 was more maneuverable. Additionally, the aircraft was found to be easily maintained.

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 only 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. Among the IK-3 improvements planned was the installation of a more powerful engine. Engines that were considered included an upgraded 1,100 hp Hispano-Suiza 12Y-51, the Daimler-Benz DB 601A and the 1,030 HP Rolls-Royce Merlin III.

Simultaneously, Rogožarski was pursuing a new fighter design, the IK-5, that was to be powered by two Hispano-Suiza 12Y engines. Two versions 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 wind tunnel tested and construction of a prototype begun when the German invasion ended work.

The Ikarus S-49 fighter, produced after the Second World War, was based on the IK-3.

Operational history
At the beginning of the April war, only 6 of the 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 to defend the Yugoslav capital, Belgrade. Both fighter squadrons were stationed at Zemun airport. One source 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 claims 11 victories for the IK-3, with Narednik (Flight Sergeant) M. Semiz as most successful (4 victories).

Operators

 * Kingdom of Yugoslavia
 * Royal Yugoslav Air Force
 * 🇩🇪 Germany
 * Luftwaffe