The Ikarus IK-2 was a high-wing monoplane, representing Yugoslavia’s first attempt at creating a domestic fighter aircraft. It started as a private endeavor by two engineers, and after two prototypes, much opposition and a lot of dramatic background, 12 planes of the type were produced by the Ikarus factory for the needs of the Air Force. Though obsolete by 1941, the IK-2s still served their country in wartime.
The IK-L1 was the original prototype of the fighter with the 860hp 12 Ycrs engine, and an intended armament of a 20mm HS.404 and 2 7.7mm Darne machine guns that was, however, not fitted before the plane crashed.
The IK-02 was the second prototype. Its key differences were metal sheeting on the wings as opposed to the fabric cover on the IK-L1, and 7.92mm Browning FN machine guns instead of Darne. It was also tested at some point with an Oerlikon FF instead of an HS.404.
The IK-2 is the definitive production version. It differs little from the IK-02, with the exception of some minor revisions and slightly improved efficiency of the engine.
The IK-2 with a Browning FN was a modification made to several IK-2s in 1940, replacing their hub-firing 20mm cannon with a 7.92mm Browning FN. The standard configuration was returned by February 1941.
Specifications (IK-2 production):
Length: 7.88 m
Wingspan: 11.40 m
Height: 3.84 m
Wing area: 18 m²
Empty: 1,502 kg
Max take-off: 1,857 kg
Engine: Hispano-Suiza 12 Ycrs
Engine power: 640 kW (860 hp)
Maximum speed: 453 km/h
Climbing speed: 923 m/min (15.4 m/s)
Range: 700 km
Flight ceiling: 12,000 m
1 x 20 mm Hispano-Suiza HS.404, hub-firing (60 rpg)
2 x 7.92mm Browning FN (250 rpg)
In 1932, aeronautical engineers Ljubomir Ilić and Kosta Sivčev, after returning from France, began privately working on a new design for a domestic Yugoslav fighter plane that would replace the outdated Czechoslovak BH-33. The initial design called for a low-wing monoplane, but this was changed to a high-wing due to opposition from Air Force personnel who favored the old biplanes. Emphasis was placed on speed, climb rate, maneuverability and firepower. For that reason, the French 20mm HS.404 was selected, firing through the 860hp Hispano-Suiza 12Ycrs - considered an extremely powerful engine for the time. The structure and armament dictated the use of metal in the construction.
In 1933, the engineers had a wooden scale model tested at Paris’ Eiffel wind tunnel, and then revealed the until-then secret project to their superior, who gave his full approval. The Ikarus factory in Zemun was given the order to construct the first prototype, designated IK-L1 (IK for Ilić and Kosta, the initials of the engineers, L for Lovac, and 1 for first). It was completed by 1934, but only made its first flight on April 22, 1935 under Leonid Bajdak, a vocal opponent of the entire program. The IK-L1 flew unarmed for tests - it was planned to have the hub-firing HS.404 cannon and two synchronized Darne machine guns. On its second flight, the L1 pilot performed unplanned aerobatics and the fabric on the wind was observed to have loosened. On the third flight, another maneuver in the form of a shallow dive and a sudden pull-out ripped the fabric of the leading edge open, sending the prototype into a spin. Pilot Bajdak bailed out, but the plane crashed.
The design came under heavy criticism after the crash, but the Ikarus factory pushed forward with a second prototype after it was deemed that the crash was caused by poor build quality, and more testing was needed. After 10 months, the second IK-02 prototype was completed in June 1936, this time with metal sheeting over the wings, better pilot visibility, and Browning machine guns instead of the previously planned Darne. Janko Dobnikar was the new test pilot, with the first flight on August 24, 1936. The testing was rigorous this time, with equipment to measure different flight characteristics. Dobnikar followed the test program, achieving the unofficial European speed record for the fastest fixed-undercarriage plane and the total Yugoslav speed record with 435 km/h.
Mock dogfights were held in 1937 with the Yugoslav Fury biplane then in service, where the IK-02 out-climbed it, out-turned it and had greater speed. Dobnikar even challenged pilot Bajdak, who was still expressing his opposition to the plane, to a climbing, racing and dogfight contest where Dobnikar would pilot the IK-02 and Bajdak would pilot the Fury. The biplane was defeated in all three aspects, and soon the first order for 12 IK-2 production planes with slight improvements was placed on November 20, 1937.
The production IK-2 fighters arrived in units by early 1939, already obsolete in comparison to the high-wing monoplane. When war struck in April 1941, 8 out of 12 were operational, with two being repaired and two badly damaged. IK-2s participated in the air war, first flying mainly patrol and reconnaissance missions, and later being involved in dogfights together with Yugoslav Hurricanes. The Germans likely captured 5 of the last IK-2s not destroyed by their own pilots, and gave 4 to their puppet state, the Independent State of Croatia, where they remained in service until 1944. None survived the war. However, engineers Ilić and Sivčev had also spearheaded the creation of a new, more modern Yugoslav fighter, the IK-3.