Category Archives: Yugoslavia

Rogožarski IK-3

WW2, Yugoslavia, , ,

Yugoslavia (1938)

Type: Fighter aircraft

Number built: 1 prototype plus 12 production aircraft

The most modern Yugoslavian domestically developed fighter IK-3. (http://www.airwar.ru/image/idop/fww2/ik3/)

The Kingdom of Yugoslavia, despite its rather undeveloped industry and infrastructure, still possessed several aircraft manufacturing companies. During the 1930s, these produced a series of aircraft that would be adopted for military use. These were mostly training aircraft but there were also several fighter designs that would see service with the Kingdom of Yugoslavian Royal Air Force (RYAF). Among them was the IK-3 fighter, created by the well-known Yugoslavian aircraft engineers Ljubomir Ilić, Kosta Sivčev, and Slobodan Zrnić.

History

During the 1930s, the RYAF was mainly equipped with old and obsolete biplane fighters. While this would be eventually solved by the introduction of more modern, foreign designs like the Bf 109 and the Hawker Hurricane, some Yugoslavian aircraft engineers wanted to develop domestic fighter designs. This motivated two aircraft engineers from Ikarus, Ljubomir Ilić and Kosta Sivčev, to start working on such a design. They were already involved in designing a new high-wing fighter named IK-2. This aircraft proved to be superior to older biplane fighters that were in RYAF service. But after a small production series of 12 aircraft, it became obvious that this aircraft would quickly become obsolete, in contrast to other nations’ low-wing fighters.

The IK-2 fighter aircraft. (http://www.vazduhoplovnetradicijesrbije.rs/index.php/istorija/565-ikarus-ik-2)

For this reason in 1933, Ljubomir Ilić and Kosta Sivčev began working on improved fighters on their own initiative. While initially, they tested various ideas, eventually both agreed that a low-wing design was the best option. While having experience in fighter design, these two quickly realized that this project would require more work than the two engineers could achieve on their own. So they asked another engineer Slobodan Zrnić to assist in their work. All three of them worked on this project under the veil of secrecy. Finally, in 1936 they had a finalized project which was presented to the RYAF officials. After some time spent considering this new proposal, the RYAF gave the green light for it at the end of March 1937. A deal was made for the construction of a single prototype for testing and evaluation. While the IK-2 was built by Ikarus, the construction of the new aircraft was given to Rogožarski instead. Given the experience this company had working with wooden airframes, the new fighter was to have a primarily wooden construction to reduce costs and speed up development time.

Name

This project would receive the IK-3 designation. At that time it was common practice that any newly developed aircraft was to be named based on the designer’s initials. In this case, I stood for Ilić and K for Koča, which was Kosta Sivčev’s nickname. The number 3 represents the third fighter project of these two engineers.

Construction of the Prototype

After one year of work, the first prototype was completed. In appearance and design, this was quite a modern aircraft. It was built using a mixed construction and was powered by a 925 hp V-12 Hispano-Suiza 12Y29 engine. It was flight tested for the first time on the 14th of April, 1938. An initial series of test flights were carried out near the capital of Belgrade at Zemun. The test pilot at this early stage was Captain Milan Bjelanović. These flight tests lasted up to the late summer of 1938. During this time, there were no major problems reported with its design, and the aircraft was given to the RYAF for future testing.

The IK-3 first prototype was tested in 1938. (http://www.airwar.ru/image/idop/fww2/ik3/)

A commission of several RYAF officials was elected for the planned army testing and it was agreed that the whole process should last 100 flight hours. For this, the aircraft was to be fully armed which included a centerline mounted 20mm cannon which fired through the propeller hub, and two 7.92 mm machine guns placed in the upper engine cowling.

Following the conclusion of the testing by the RYAF, a report was issued in which its performance was deemed sufficient. The armament was installed and functioned without any major issues, however, it was desirable to add two more machine guns in the wings. The aircraft offered good overall flying performance though its controls were noted to be somewhat problematic and some changes were requested. To resolve this it was asked to improve the design of the flaps, by increasing their deployed angle and size. The canopy was of rather poor quality and was reflective, forcing some test pilots to fly the aircraft with open canopies. The engine had overheating problems which required extensive work before finally being solved by adding an improved cooling system. During these trials, the maximum speed achieved was slightly over 520 km/h. While not bad, the RYAF commission wanted it to be increased to at least 540 km/h, which was not achieved on this aircraft. Overall, this aircraft was deemed worth developing further by the RYAF commission, which gave a recommendation for a small series of 12 aircraft to be produced.

The production of the IK-3

Following the production orders for the IK-3, an accident happened that threatened the realization of the project. On the 19th of January 1939, an accident occurred during a test flight, and test pilot Captain Milan Pokorni was killed, and the plane was lost. A commission was formed to examine what went wrong. After analyzing the wreckage it was determined that the IK-3 prototype’s structural design was not at fault, nor did the pilot make any mistakes. Prior to this accident another pilot Dragutin Rubčić, had a harsh landing, damaging the aircraft in the process. Why this was not properly examined before another take-off by Captain Milan Pokorni is unclear. In another account, during a dive, the canopy broke free which probably made the pilot enter a climb. This seemingly caused enough force to be put on the already damaged aircraft, resulting in structural failure.

While this accident did not lead to the cancellation of the whole project, it did cause huge delays in the delivery of new aircraft. The RYAF officials wanted the aircraft to be thoroughly examined and tested before any further production order was given. Finally, in November 1939, the project received a green light again.

The second prototype, which was also the first aircraft of the first production series, was completed in December 1939. This aircraft was examined in detail over the next few months. As no major issues with the prototype were found, the production of additional 5 aircraft was completed by the 17th of April 1940. The other six aircraft could not be completed as the IK-3’s propellers had to be imported. As there were delivery problems with the last six aircraft, instead of the hydraulically controlled Hispano-type propeller, they were equipped instead with Chauviere-type propellers. It used pneumatic commands which necessitated changes to the engine and its compartment. These were finally completed in July 1940. Once all were available these were allocated to the 51st Fighter Group in July 1940. These were divided into two six-aircraft strong squadrons (the 161st and 162nd) stationed at Zemun airfield near the capital Belgrade.

Members of the 51st Fighter Group in front of their IK_3 during the summer of 1940. (https://nasaborba.com/rogozarski-ik-3-ponos-srpskog-ratnog-vazduhoplovstva/)

Second series proposal

In march 1940, the Rogožarski company proposed to the RYAF another production run of 25 to 50 new IK-3 aircraft. It was to incorporate a number of improvements like self-sealing fuel tanks, a redesigned radiator, adding radio equipment, armor for the pilot seat, an aerodynamically improved engine cowling, and a new gunsight. The company proposed that these could be completed in a period of 9 months. To speed up the developing process, one IK-3 (serial number 7) was selected to be converted as the prototype of this new series. This aircraft was completed by the end of March 1941. It was flown in early April, managing to reach a speed some 15 to 20 km faster than the standard IK-3. Its further development was stopped due to the outbreak of the war.

The second IK-3 prototype was also the first aircraft of the small production series. (http://www.airwar.ru/image/idop/fww2/ik3/)

Further IK-3 modification proposals

Some accounts claim that the aircraft was tested with a DB 601 from one of the RYAF’s imported German fighters. According to eyewitness accounts, this model was fully completed and tested. If this was true, it was not confirmed by any historical documentation or photographic evidence. At the same time a Hurricane aircraft was tested with this engine (known as LVT-1). It is possible that an eyewitness simply confused these two.

Another proposed project was the IK-3/2 two-seater trainer. It was planned to add another position to the rear of the pilot, reduce the armament to two machine guns, and move the cooling radiator some 50 cm to the rear. As a number of modern Bf 108 aircraft were acquired, this project was dropped with no prototype ever constructed.

In service, prior to the war

The newly produced IK-3 entered service at the end of 1940 and was used primarily in training flights. They were especially used to test their performance against the Bf 109, which was also in service with the RYAF. The Bf 109 offered better horizontal and climbing speed. In comparison, the IK-3 possessed better horizontal maneuverability, possessing a smaller turning radius of 260 m, the Bf 109 on the other hand had a turning radius of 320 m. The IK-3 also had a somewhat more stable armament installation, providing better accuracy during firing. As the pilots who flew on the IK-3 were not entirely accustomed to flying on modern airplanes, harsh landings were quite common. This necessitated that many IK-3 were often in workshops awaiting repairs of their landing gear units.

The IK-3’s Achilles Heel was its landing gear unit which was of poor quality. This led to a quite common breakdown of the landing gear during landings. This aircraft was damaged in this way a day before the outbreak of the war. The Germans would capture it and later, in 1942, send it to be scrapped. (http://www.airwar.ru/image/idop/fww2/ik3/)

The sixth produced IK-3 would be lost in an accident that happened on the 3rd of September 1940. During a mock dogfight with a Potez 25, pilot Anton Ercigoj lost control of the fighter and fell into the Danube river. The pilot was killed on the spot and the aircraft could not be salvaged. While it was not clear how the accident happened, it was speculated that it did occur due to the pilot being too tired from previous flights.

In War

Just prior to the outbreak of the so-called April war, from the 6th to 17th April 1941, between the Kingdom of Yugoslavia and the Axis forces, only 6 IK-3 were combat-ready. The remaining 5 aircraft were awaiting repairs. Three were located at the Rogožanski workshop in Bežanijska Kosa, and two more at the Zemun Airfield. The war began with massive Luftwaffe bombing raids on vital military, communication, infrastructure, and civilian targets. The capital, Belgrade, was a primary target of strategic bombing and was majorly hit. The whole 6th Fighter Regiment, to which the 51st Fighter Group belonged, was tasked to defend Northern Serbia and parts of Croatia and Bosnia from any potential enemy attacks. The 51st Fighter Group reinforced the 102nd Fighter Squadron equipped with Bf 109 and was tasked with defending the Northern sector. Its primary defense point was the capital Belgrade.

The 51st Fighter Group was informed of a possible enemy attack almost an hour before it occurred. At 0645, the unit was informed of two approaching enemy aircraft formations. Five minutes later, all available IK-3s took to the sky to defend the capital. One aircraft, due to engine problems, had to abort the flight and went back to the base.

During the first engagement, some 5 to 6 enemy aircraft (at least one Ju 87) were shot down. One IK-3 was shot down and three more were damaged. Two of these were badly damaged and they were not used in combat after this point. The defenders were then left with only three operational IK-3 aircraft. Late that morning, another bombing raid was launched by the enemy. While only three IK-3 were available at this point, their attack was supported by the Bf 109s from the 51st Group. While the Yugoslavian fighters reported no losses, they managed to take down one Bf 109 and damaged two Ju 87. During the first day of combat, the Germans used nearly 500 bombers which dropped some 360 tonnes of bombs on Belgrade.

The following day, enemy activity came in the form of smaller formations that attacked specific targets. The Ik-3s once again saw action, managing to shoot down more enemy aircraft. While they received no losses, many aircraft were badly damaged by enemy return fire. For example, the IK-3 fighter piloted by Milisav Semiz received 56 hits. The engine itself received some 20 direct hits. While fully covered in engine oil the pilot managed to land safely at the Zamun airfield, the aircraft had to be written off. This unit was reinforced with one IK-3 of the second series. Due to heavy enemy activity, the unit was repositioned some 50 km away from Belgrade at Ruma. For the next few days due to bad weather, the IK-3 was not used. On the 11th of April, the Yugoslavian positions were discovered by a Me 110, which proceeded to attack the airfield. It failed to do any damage, but one IK-3 began a pursuit of it. Eventually, it managed to close in on it and shoot it down. Later that day, two IK-3s took to the sky and managed to shoot down two Ju 87s.

At 1700 hours, due to an enemy ground advance, it was decided to move the available units to Bosnia. The retreat was to commence on the 12th of April, but due to sudden enemy advances and poor weather, the evacuation could not be achieved. The unit commander and pilots agreed to burn down any surviving aircraft to prevent them from falling into enemy hands. This action basically marked the end of the IK-3 service with the RYAF.

Remains of the burn-down IK-3 at Ruma airbase. (N. Miklušev Maketar Plus)

In total both the 161st and 162nd squadrons reported some 15 air victories. These included two Ju 88, one Do 17, two Ju 87, two Bf 109, three Me 110, and one He 111. The remaining claims remain a mystery.

In German hands

The victorious Germans managed to capture a number of operational and damaged IK-3s fighters. Most were captured at Rogoarski repair workshops, with a few more at the Zemun airfield, all being abandoned. This included the IK-3 with serial numbers 2151 (which was actually the second prototype) 2152, 2153, 2157, 2158, 2160, and 2161. Most of these would be left exposed to the elements, near the capital Belgrade, until 1942 when they and many other captured aircraft were scrapped. At least one IK-3 was transported back to Germany. It is unlikely that it was used for testing, and some sources suggested but instead placed in the Berlin Aviation Museum. Its fate is unknown but likely lost when the museum was bombed by the Allies in 1944.

A captured IK-3 near the Capital of Belgrade after the April war. (http://www.airwar.ru/image/idop/fww2/ik3/)
Many captured Yugoslavian aircraft were gathered at the Zemun airfield. There at least three IK-3s could be seen together with some Hurricanes and Caproni aircraft. Most if not all of these would be left exposed to the elements and finally scrapped in 1942. (N. Miklušev Maketar Plus)

Technical characteristics

The IK-3 was a low-wing, mixed-construction single-seat fighter. Its fuselage consisted of welded chrome-molybdenum tubes supported with wooden stringers, and covered in duralumin skin. The rear part of the fuselage was covered in plywood and canvas. The wings were mostly made of wood with some metal links added for better structural stability. The IK-3 wings were covered with birch plywood which was in turn covered in bakelite. The ailerons were made of metal, but covered with canvas. While the trailing edge flaps were made of duralumin, assembly was made using the same materials as the wings.

The IK-3 was powered by a 925 hp, V-12 Hispano-Suiza 12Y29 liquid-cooled engine. It used a Hamilton-type constant-speed propeller. The cooling airflow was adjustable by changing the angle of the grills located on the radiator intakes.

The canopy initially was made by using concave-convex side panels. These proved to be problematic as they distorted the pilot’s vision and were replaced with simpler flat sides. The instrument controls panel and command were directly copied from French designs. The first prototype and the later first-moved aircraft of the second series were only equipped with radios.

The IK-3 was designed as a low-wing mix construction single-seat fighter. (http://www.airwar.ru/image/idop/fww2/ik3/)

The landing gear was of a conventional design consisting of two front legs which retracted outwards, with the tail wheel being fully retractable. To provide better landing, the front landing gear units had shock absorbers. The IK-3 landing gear was of rather poor quality and it often broke down during landing, and led to many aircraft being constantly under repair.

Initially, the armament consisted of one 2 cm HS 404 cannon placed behind the engine, and two 7.7 mm M.31 Darne machine guns, positioned above the engine. This was used on the prototype for firing testing. Later production models were rearmed with one 2 cm Oerlikon M.39 cannon supplied with 60 rounds of ammunition. The 7.7 mm machine guns were replaced with two 7.92 mm Browning machine guns. The ammunition load for each machine gun consisted of 500 rounds.

The IK_3 was fairly strongly armed with one 2 cm cannon and two machine guns. The cannon is actually firing through the propeller center, which is visible in this photograph. (https://nasaborba.com/rogozarski-ik-3-ponos-srpskog-ratnog-vazduhoplovstva/ )

Production

Despite its advanced design, only one prototype and 12 aircraft would be built. This took an extended period of time to be completed from December 1939 to July 1940. While proving to be one of the better domestically developed aircraft, the RYAF was reluctant to order more IK-3 fighters as it was heavily dependent on imported parts.

Production Versions

  • IK-3 Prototypes – Two prototypes were completed
  • IK-3 – Production version
  • IK-3 II Series – One aircraft converted to this version
  • IK-3 powered by a DB 601 engine – Allegedly one aircraft was modified this way, but the evidence is lacking
  • IK-3/2 Series – Proposal for a two-seater trainer, none ever completed

Conclusion

Despite being a very capable design, the IK-3 saw only limited production. This was mainly the case due to many of its parts having to be imported, something that could not be easily done in war-torn Europe. When used in combat, despite the limited number of operational aircraft, they performed well, with claims for 10 enemy aircraft at the loss of only one IK-3. Ultimately they could do little to turn the tide of the war, and most were either captured or destroyed by their own crews to avoid being captured.

IK-3 Specifications
Wingspans 10.3 m / 33 ft 4 in
Length 8 m / 26 ft 3 in
Height 3.5 m / 10 ft 9 in
Wing Area 16.5 m² / 178 ft²
Engine 925 hp V-12 Hispano-Suiza 12Y29 liquid-cooled engine
Empty Weight 2.070 kg / 4.560 lbs
Maximum Takeoff Weight 2.630 kg / 5.800 lbs
Maximum Speed 520 km/h / 325 mph
Cruising speed 400 km/h / 250 mph
Range 600 km / 370 miles
Maximum Service Ceiling 9,400 m
Fuel 330 Liters
Crew 1 pilot
Armament
  • One 2 cm cannon and two 7.92 mm machine guns

Gallery

IK-3 Prototype - 1940
IK-3 Prototype – 1940
IK-3 51.Grupa, 6.Lovacki Puk No.2158 Br.9 April 1941
IK-3 161.Eskadrilla, 51.Grupa No.218 April 1941
IK-3-161.Eskadrilla,-51.Grupa-No.10 - April 1941
IK-3 161.Eskadrilla, 51.Grupa No.2159 Br.10 – April 1941
Possible markings for captured IK-3 being tested by a German research unit

Credits

  • Article written by Marko P.
  • Edited by  Henry H. and Medicman11
  • Ported by Marko P.
  • Illustrations by Ed Jackson

Source:

  • N. Miklušev (2014) Maketar Plus, IMPS Srbija
  • Č. Janić i O. Petrović (2011) Kratka istorija vazduhoplovstva u Srbiji, Aero Komunikacije
  • D.Babac Elitni vidovi Jugoslovenske vojske u Aprilskom ratu.
  • Z. Rendulić (2014) Lovačka Avijacija 1914-1945, Teovid
  • B. Dimitrijević, M. Micevski and P. Miladinović (2016) Kraljevstvo Vayduhoplovstvo 1912-1945
  • N. Miklušev (2014) Maketar Plus, IMPS Srbija
  • N. Miklušev (2004) Avijacija Br.6
  • M. Hrelja, Rogožanski IK-3, Srpska Akademija Nauka I Umetnosti
  • http://www.vazduhoplovnetradicijesrbije.rs/index.php/istorija/563-rogozarski-ikz-ik3

 

 

Ikarus IK-2

WW2, Yugoslavia, , ,

kingdom of yugoslavia flag Yugoslavia (1933)
Fighter – 2 Prototypes & 12 Production Aircraft Built

The IK-2 fighter aircraft. Source: www.vazduhoplovnetradicijesrbije.rs

During the early 1930’s, the Royal Yugoslav Army Air Force (RYAF) was mainly equipped with old and obsolete biplane fighters. The introduction of a new fighter was desirable, but its development was hampered by the resistance of leading military officials, and pilots who still believed in the superiority of the biplane. Once Ikarus commenced production of the new high-wing IK-2, it readily demonstrated its superiority over the biplanes of the prior generation.

History of Ikarus 

Ikarus was one of the first Yugoslavian domestic aircraft manufacturers. It was formed in October 1923 by a group of businessmen from the city of Novi Sad. The aircraft development department was led by Josip Mikl and Dimitrije Konjević. Josip Mikl had previously been involved in the development of hydroplanes for the Austro-Hungarian Empire during World War I, while Dimitrije Konjević was a former high-ranking officer in the Yugoslav Naval Air Force. The company saw success during the twenties and received a series of new orders for the production of aircraft, mostly for training. In 1927 thanks to increasing revenues, Ikarus opened a new production plant located in Zemun near the capital of Belgrade. It was heralded as a great success when it received a large production order for some 200 license-built Potez 25 aircraft in 1932.

Ikarus crest. Source: Wiki

The IK-2 Development

In early 1930, the main fighter of the RYAF was the aging Avia BH-33 biplane fighter. In the hopes of replacing it with a new domestically-developed fighter, two aircraft engineers from Ikarus, Ljubomir Ilić, and Kosta Sivčev began working on a new design. Interestingly this was a private venture and not ordered by the state, which was unusual.

While initially intended to be a low-wing fighter with retracting landing gear, due to fierce opposition from many Air Force officers and pilots who favored the old biplane design, this new concept had to be abandoned at an early stage of development. The two engineers then decided to proceed with a high-wing fighter design that was to be powered by a strong engine. A wooden mock-up was completed in 1933 which would be tested using a wind tunnel in Paris. After the first drawings and testing of the mock-up were completed, the result of this work was given to the RYAF officials in September 1933. After an analysis of all available data, a green light was given for the project, and Ikarus was instructed to build the first prototype.

At this early stage, the new fighter received the IK-L1 designation. As was common in Yugoslavia at the time, new aircraft designs usually received a designation based on the designer’s initials. In this case, I stand for  Ilić and K stands for Koča which was Kosta Sivčev nickname. The L1 represents L for Fighter (Lovac in Yugoslavian) and the number 1 indicates the first prototype. The first fully functional prototype was completed by September 1934.

The first prototype IK-L1 with its two designers Ljubomir Ilić and Kosta Sivčev next to it. Source: www.vazduhoplovnetradicijesrbije.rs

Testing the First Prototype

While the IK-L1 prototype was scheduled to be flight tested shortly after the first prototype was fully completed in September 1934, due to numerous delays it wasn’t conducted until April 1935. Unfortunately for the Ikarus and its design team, the first prototype had a very short and abrupt service life. As it was being prepared for the first series of test flights, an upswell of opposition, mainly from Captain Leonid Bajdak and other pilots, vehemently objected to the introduction of such a radical new design, arguing that the biplanes were superior. Regardless, Bajdak was chosen to fly test the IK-L1 prototype.

The maiden flight was made on the 22nd of April, 1935 at an airfield near Belgrade in Zemun. The first day of flying was rather successful, with the prototype exhibiting generally good performance. The test the following day produced largely similar results, but upon landing, some of the wing’s fabric skin was noted as slightly loose. Regardless, it was agreed that the testing should carry on. On the 24th of April, while flying the prototype, Captain Bajdak performed a series of unplanned aerobatics. At a height of 1,000 meters, he made a sharp dive, followed by an abrupt climb. This of course caused massive stress on the wing, which led to part of it breaking off the aircraft. Bajdak lost control and had to bail out. While he survived without injury, the IK-L1 prototype crashed and was completely destroyed.

According to Captain Bajdak in his report, he wrote that the IK-L1 had good controls and was pleasant to fly. The most obvious issues were the lack of visibility, due to the high-wing design. Another of his objections was the long take-off of some 300 meters. This was a surprisingly fair report from a pilot who professed such serious misgivings about this new design.

Work on a New Prototype

After an analysis of the IK-L1 wreckage, it was discovered that the accident was primarily due to poor build quality. As Captain Bajdak’s report was insufficient to make a final conclusion, Ikarus officials decided to produce another prototype. This time great care was taken to ensure the overall quality of its construction. Another change made was that the aircraft was built using mostly metal construction, with the exception of the aft fuselage and tail. The second prototype was designated IK-02 and took about ten months to be built, completed in June 1936. A new test pilot was chosen, Flight Lieutenant Janko Dobnikar. The series of flight tests were carried out at the newly opened test center stationed at the Zemun airfield. Early flight tests were quite satisfactory, with the IK-02 reaching a top speed of 435 km/h.

In 1937 the IK-02 prototype was tested in a mock dogfight against the Hawker Fury, the RYAF’s then-current biplane fighter. After a series of 16 such exercises, the IK-02 easily beat the Hawker Fury in almost every category of flight performance,  speed, climb rate, and turning ability, among others. Frustrated by the success of the new fighter, Captain Bajdak and Lieutenant Dobnikar frequently got into fierce quarrels. It ended with Lieutenant Dobnikar challenging Captain Bajdak to a flight contest. The conditions of the contest were as follows: both pilots had to reach a height of 4 km over Zemun, after which they were to race a distance of 140 km from Belgrade to Novi Sad and back. The competition was meant to end in a mock dogfight between the two. Lieutenant Dobnikar IK-02 easily won the first two rounds of the race. The mock dogfight was fierce but Captain Bajdak’s Fury was constantly overtaken by the superior IK-02. In the end, he had to admit defeat and thus concede that the IK-02 had bested the biplane. Unfortunately, the IK-02 would be lost when it was hit by lightning during a flight. As the aircraft began to catch fire, the pilot bailed out. While he survived, the aircraft crashed and burned, completely destroying it.

Limited Production

Despite both prototypes being lost to separate accidents, their overall performance was deemed acceptable and a small production order was given. In November 1937 Ikarus was instructed to produce 12 IK-2 aircraft. The first six were delivered in December 1938, with the remaining aircraft arriving by February the following year. After a brief period of adjustment and training, the IK-2 was allocated to the 6th Fighter regiment stationed in Zemun. In October 1939, the IK-2 was redeployed to Zagreb and given to the 4th Fighter Regiment. Just prior to the Yugoslavian entry into World War II, the 4th Fighter Regiment would be repositioned to Bosanski Aleksandrovac close to Banja Luka. It was part of the 107th Squadron with the task of protecting the 8th Bomber Regiment, consisting of some 23 Bristol Blenheim bombers.

Despite being superior to other fighter designs that were in service with the RYAF, it too would be replaced by the later developed IK-3 fighter. Source: www.destinationsjourney.com

Technical Characteristics

The IK-2 was a high-wing, single-engine, almost all-metal fighter aircraft.  Its fuselage was constructed of a chrome-molybdenum steel tube frame which was then covered with duralumin skin. The rear section of the fuselage close to the tail unit was covered with fabric.

The semi-cantilever wings were built using the same principle as the fuselage. The difference was that the first prototype used a fabric skin. The second prototype and the production aircraft used a duralumin skin. Two larger struts were placed beneath each wing. The tail unit was of a standard design, with one horizontal and two vertical stabilizers.

Close-up view of the IK-2 wing struts construction. Source: N. Miklušev Maketar Plus

The fixed landing gear consisted of two larger wheels and a smaller tailwheel. To help during landing the front landing gear was equipped with pneumatic shock absorbers. These were also fitted with brakes. The tailwheel was steerable. Initially, the front landing wheels were covered in a protective cover, also known as ‘spats,’ which were later removed.

The cockpit was fully enclosed. Interestingly its sliding canopy actually slid down into the fuselage sides. Quite similar to those used on ordinary cars. Due to the high wing design, the pilot’s visibility was severely limited. To somewhat remedy this issue two small glass windows were placed on the cockpit fuselage sides to help during landing.

The IK-2 cockpit was fully enclosed, but its sliding canopy slides down into the fuselage sides. Source: N. Miklušev Maketar Plus
To help the pilot cope with the cockpit’s fairly limited visibility, two smaller glass windows were placed on the cockpit fuselage sides. Source: N. Miklušev Maketar Plus

The two IK-2 prototypes were powered by an 860 hp Hispano-Suiza V-12 engine. It was equipped with an adjustable pitch three-blade propeller. The fuel tanks were located just aft of the engine in front of the cockpit. The production aircraft was powered by an 860 hp Avia HS engine. This engine was built under license in Yugoslavia. Overall performance of the aircraft did not change much, as the engine swap was mainly done to facilitate ease of maintenance.

The IK-2’s armament consisted of two 7.7 cm Darne Mle 1930 machine guns, and one 20 mm Hispano HS-9 cannon. The machine gun’s ammunition load consisted of 250 rounds each, and 60 rounds for the cannon. The cannon fired through the center of the propeller shaft, while the two machine guns were placed on each side of the front of the fuselage. Some IK-2’s had their cannon replaced with a 7.92 Browning machine gun. But by the time of the war, all available aircraft were equipped with the 20 mm cannon.

According to D. Babac, the two Darne Mle 1930 machine guns were at some point replaced with two 7.92 Browning machine guns. In addition, this author notes that the machine guns were placed above the engine compartment and not on the sides.

In War

When the war broke out on the 6th April 1941 the 4th Fighter Regiment had only 8 fully operational aircraft ready for service. Four IK-2’s suffered from mechanical breakdowns and were undergoing repairs at Zemun and Zagreb workshops. Author Z. Rendulić mentioned that only 10 IK-2 were available.

Two IK-2 (With 31 and 34 white painted markings) from the 4th Fighter Regiment were taken at Borongaj airfield in Zagreb in 1940. Note the long groove for the machine gun located above the exhaust pipes. Source: N. Miklušev Maketar Plus

In addition, the 4th Regiment had 18 to 20 Hawker Hurricanes, making this unit among the most up-to-date in the RYAF. On the first day of the war, the IK-2 was mainly used for reconnaissance. The following day, two IK-2s tried to bring down a German reconnaissance aircraft but failed to do so. One IK-2 would be lost, possibly due to mechanical breakdown. The first proper combat engagement of the IK-2 occurred on the 9th of April when during reconnaissance, a group of some 23 Bf 109 were spotted.  While one IK-2 had to land to refuel, the second one provided a delayed action in hopes of giving the 4th Fighter Regiment enough time to muster its available fighters. Shortly after, some 5 or 6 IK-2 and 8 Mk.I Hurricanes joined the fight. The German fighters were attacking in well-coordinated groups, protecting each other, while the Yugoslav fighters entered the battle in a somewhat disorganized manner. After a fierce skirmish that lasted some 10 minutes, the Germans broke off and retreated back to their base of operations in Austria. The Germans lost two aircraft, while the Yugoslavians lost three, one IK-2 and two Hurricanes.  In the next few days, engagements with the enemy were rare, but the IK-2 managed to shoot down one Ju 88, in addition to two other Luftwaffe aircraft.

The 4th Regiment would meet its fate on the 14th of April when the pilots decided to destroy their remaining aircraft in order to prevent them from falling into enemy hands. Despite their attempts, the Germans managed to capture one slightly damaged IK-2 belonging to the 4th Fighter Regiment. Four additional aircraft were acquired when the repair workshops in Zagreb and Belgrade were captured.  Some internet sources noted that up to 9 aircraft were captured by the Germans, but this seems highly unlikely and that the number of 5 is probably correct.

While a number of IK-2 were lost due to mechanical failures, the majority would be destroyed by their own crews to prevent them from being captured by the Germans. Source: www.destinationsjourney.com

In NDH Service 

Following the defeat of Yugoslavia, the Independent State of Croatia, a German puppet state was created. In June 1941 a request was made to the Germans to provide over 50 captured Yugoslavian aircraft including the IK-2, in an attempt to create a Croatian Air Force. The Germans were more than willing to give the most obsolete aircraft including four IK-2. The fate of the fifth aircraft is not clear. It may have been cannibalized for spare parts, or even sent to Germany for evaluation, but due to a lack of precise sources, we can not be sure. The Croatian Air Force regularly had problems acquiring spare parts for the Yugoslavian aircraft, as these were either destroyed, sabotaged, or commandeered by the Germans. Surprisingly the IK-2 remained in service for a few years until 1944 when they were finally withdrawn from service. They were rarely used by the Croats who often complained about its poor visibility.  Sadly no IK-2 survived the war, with all likely being scrapped.

Production Versions

  • IK-L1 –  First prototype aircraft that was lost in an accident only a few days after initial trials were conducted
  • IK-02 – The second more successful prototype
  • IK-2 – Production version

Operators

  • Kingdom of Yugoslavia – Eight were used during the April War.
  • Independent State of Croatia NDH – Used four aircraft supplied by the Germans, their service was limited.

Conclusion 

The Ikarus IK-2 was one of the earliest Yugoslavian attempts to develop the first proper fighter aircraft and was intended to replace the aging biplanes then in service with the Yugoslavian Royal Air Force.  While it proved to possess superior performance to biplane fighters, it too was quickly made obsolete by the introduction of new low-wing fighter aircraft. Regardless, the IK-2 was a sound design, which proved that the Yugoslav aviation industry, despite its small size, was capable of producing a viable mono-wing fighter aircraft.

The Ikarus’ powerful engine and impressive armament paved the way for Yugoslavia’s later advanced monoplane, the IK-3. Its performance in key areas gave it an advantage over the Hawker Fury. The IK-2 saw combat against Germany’s advances in the early 1940s before it was ultimately superseded by more advanced aircraft.

IK-2 Specifications
Wingspans 11.4 m / 37 ft 4 in
Length 7.88 m / 25 ft 8 in
Height 3.84  m / 12 ft 6 in
Wing Area 18  m² / 59 ft²
Engine One 860 hp Avia HS12YCrs
Empty Weight 1.500 kg / 3.300 lbs
Maximum Takeoff Weight 1.875 kg / 4.130 lbs
Climb Rate to 5 km In 5 minute 25 seconds
Maximum Speed 450 km/h / 280 mph
Cruising speed 250 km/h / 155 mph
Range 700 km/ miles
Maximum Service Ceiling 12,000 m / 39.370 ft
Crew 1 pilot
Armament
  • Two 7.7 mm machine guns and one 2 cm cannon
Yugoslav IK-2 107 Eskadrila, 34 Grupa, 4 Lovački Puk No.2104
Yugoslav IK-2 107 Eskadrila, 34 Grupa, 4 Lovački Puk No.2108
IK-2 in NDH service

Credits

  • Written by Marko P.
  • Edited by Henry H. & Ed J.
  • Illustrated by Ed J.

Sources

  • T. Likos and D. Čanak (1998) The Croatian Air Force In The Second World War, Nacionalna i Sveučilišna Knjižnica Zagreb
  • V. V. Mikić (2000) Zrakoplovstvo nezavisne države Hrvatske 1941-1945, Target Beograd
  • Č. Janić i O. Petrović (2011) Kratka istorija vazduhoplovstva u Srbiji, Aero Komunikacije
  • D.Babac Elitni vidovi Jugoslovenske vojske u Aprilskom ratu.
  • Z. Rendulić (2014) Lovačka Avijacija 1914-1945, Teovid
  • B. Dimitrijević, M. Micevski and P.  Miladinović (2016) Kraljevstvo Vazduhoplovstvo 1912-1945
  • N. Miklušev (2013) Maketar Plus, IMPS Srbija
  • http://www.vazduhoplovnetradicijesrbije.rs/index.php/istorija/565-ikarus-ik-2

 

Fizir Prelazni FP-2

WW2, Yugoslavia, , , , ,

Yugoslavia flag Yugoslavia (1933-1947)
Training aircraft – 81 Built

Front view of the FP-2. [vazduhoplovnetradicijesrbije.rs]
The FP-2 was designed as an advanced two seater biplane trainer for the Yugoslav Royal Air Force in late 30s. It would be used to equip pilot training schools for some years before WW2. During World War II, it would be used by the Axis powers, which managed to capture a number of them, for limited ground attack operations. The FP-2 would survive the war in smaller numbers and remain in use up to 1947.

History

As the Yugoslav Royal Air Force began to develop and acquire more modern types of aircraft, the need for advanced training aircraft became apparent. Due to the obsolescence of older trainers, the Yugoslav Royal Air Force Command issued orders to begin developing a new series of advanced trainers in 1933. One of the designs submitted was the Fizir FP-1 biplane made by Zmaj. Despite its disappointing overall performance, a new design was desperately needed. At the same time, a design team composed of Rudolf Fizir and Dušan Stankov began working on a new model named FP-2. In a later address to Zmaj management in May of 1940, Dušan Stankov wrote that he was responsible for the design of the FP-2, with little to no input from Rudolf Fizir. While the Royal Air Force command was more in favor of a monoplane design, the FP-2 nevertheless received a green light.

Name

The capital letters in the name FP-2 are an abbreviation for “Fizir Prelazni 2” (Физир Прелазни ФП-2). Depending on the source, it is also sometimes identified as F.P.2. During its operational service in the Yugoslav Royal Air Force, it was also known as F.P.2-K7 after its engine name, or Fizir-Stankov F.P.2 after its designers. This article will use the FP-2 designation, as it is best known today.

What is interesting is that the FP-2 name may suggest that it was an improved version of the earlier FP-1. In reality, these two projects had nothing in common. This name was done mainly for administrative reasons, in order to obtain the funds allocated for FP-1.

Work on the Prototype

Work on the first prototype began in early 1933. At this time, the Yugoslav Royal Air Force officials were negotiating with the French for licenced production of several Gnome-Rhone engine designs, including the K-7, K-9 and K-14. For this reason, it was decided to test the performance of these engines by installing them into several prototype aircraft. This decision included the FP-2 ,which was to be powered by a French Gnome-Rhone K-7, making 420 hp.

The first prototype was officially completed by the end of 1933. It was flight tested by Zmaj test pilot Pavle Bauer. The pilot performed a series of test flights without any problems. As the first flights were successful, the FP-2 was given to the Yugoslav Royal Air Force for further testing in early 1934. For the testing of the FP-2, a commission of seven members was tasked with determining its exact flight performance. The test flight series began on the 19th of February, and after only four days a preliminary report was submitted to the Yugoslav Royal Air Force Command. The report gave mostly positive remarks on the FP-2 performance, with a few changes requested, such as increasing of the fuel load, a better position for the instruments inside the cockpit, modifications of the seats etc. The K-7 engine performance was deemed sufficient, and it was also noted that the testing of the FP-2 with any other engines at the moment was not required. This commission also urged for the FP-2 to be put into production as soon as possible. 

The FP-2 design team expected that a production order was to be given shortly by the Yugoslav Royal Air Force Command. But this was not the case for several reasons. The main problem was the inability of the Rakovica factory to locally produce the K-7 engine by 1936.  Due to high prices, the Yugoslav Royal Air Force could not buy these engines directly from France. Another issue was the adoption of the new Rogožarski ‘PVT’ high-wing training aircraft which used the same engine and offered better performance than the FP-2.

In order to solve this problem, the Zmaj engineers decided to replace the K-7 with the nine-cylinder Valter Pollux II (320 hp) engine. The ensuing flight tests carried out showed that the new engine only worsened the flight performance of the FP-2, due to lower power output. Thus, Zmaj was forced to replace it with the original K-7.

From the end of October to the first half of November 1934, more tests were carried out on the FP-2 with the K-7 by a second commission. This new commission had six members and was tasked with FP-2’s overall performance more thoroughly. These tests also included the testing of a few different types of propellers. The results showed that the metal type propellers gave better performance. In addition, the operational radius was evaluated and the results showed that, at the speed of 100 mph (161 km/h), the FP-2 could stay operational for three hours. Several pilots flight tested the FP-2 and, in general, positive remarks were given about its performance. The changes in the cockpit instrument arrangement was also rated as an improvement. After the tests were completed, this commission gave positive reviews for the FP-2 and suggested that it should be adopted for production as a basic trainer, but not as a fighter trainer due to the lack of performance for this role.

Technical Characteristics

The FP-2 was designed as a single-engine, two-seater basic trainer biplane. The FP-2 was made using wood as its main construction material and then covered with canvas. Its wooden elements were connected using metal pleats and rivets. The fuselage consisted of 16 oval shaped frames that were all connected with four long wooden spars. The wing’s construction was made of wood and then covered with fabric. Rear tail unit was made using a combination of metal and wood, which was then covered in  fabric. The landing gear was a fixed design with two wheels equipped with shock absorbers. There was no rear tail wheel and instead used a small skid which also was provided with a shock absorber. In winter, the front wheels could be replaced with skis.

It was powered by the French K-7 Gnome-Rhone 313 kW (420 hp) engine. The engine itself was placed on a ring shaped housing made of metal and duralumin construction. The maximum speed achieved with this engine was 148 mph (238 km/h). Being designed as a trainer aircraft, its crew consisted of a pilot/instructor and the student.

In Service Before War

For its service in the Yugoslav Royal Air Force, the first prototype was purchased for 577,000 Dinars in 1934. Next year, the contract for the construction of the first batch of 20 aircraft was signed. These were to be produced and given to basic training schools by 1936. All 20 aircraft were completed on time and were given to the First and Second basic training Schools. A few were temporarily given to the Fighter plane school until the more advanced PVT could be built. Once the PVT was adopted for service, the fighter school FP-2s were given to the basic training schools.

The FP-2 was mainly used to replace older training aircraft models that were in service. In its intended role, the FP-2 proved to have satisfactory performance and generally fulfilled the role of a basic trainer successfully. Only one accident was reported in 1938, when, due to a pilot error, control of the plane was lost and it crashed to the ground. The pilot managed to jump out of the plane and safely landed.

The FP-2 was considered a successful basic trainer by the Royal Air Force before the war. [airwar.ru]
During the production run, there were only minor modifications between the different planes. The FP-2 which were built in 1939 were modified with improved control panels with more updated instrumentation. Zmaj also proposed a modified FP-2H powered by the K-9 engine for use by the navy, but it was not adopted. 

By March 1941, around 9 FP-2 aircraft were reportedly awaiting repairs at the Zmaj factory. The fifth batch of 15 FP-2 were to be built by mid-1941. The materials and engine were assembled but, due to the outbreak of the war, none were delivered to the Yugoslav Air Force. Production of the FP-2 was carried out until the Axis invasion of Yugoslavia in April 1941. 

During the April War

At the time of the Axis attack on Yugoslavia in April 1941, all FP-2 were still assigned to the two basic training schools. The First pilot school was transferred near Sarajevo shortly before the outbreak of the war, along with 10 FP-2. The school was operational until the German capture of Sarajevo. The commander of this school, Colonel Adalbert Rogulja, ordered the entire unit to surrender to the Germans without attempting to sabotage its aircraft. 

The Second pilot school, located at the Kapino polje near Nikšić, had 15 FP-2. As the area was not  attacked by Axis forces, this school was operational until the end of war. The remaining FP-2s were stationed in smaller numbers across Yugoslavia. One was destroyed by the Germans in Novi Sad, and a few more in Niš and Pančevo. By the war’s end, both the Germans and Italians managed to capture an unknown number of FP-2s.

In German Service

The Germans managed to capture the Zmaj factory and an unknown number (possibly more than 15) of FP-2 across Yugoslavia. But they were more interested in the factory itself than the FP-2, and for this reason did not use the aircraft that were captured.

In Italian Service

The Italians managed to capture around 13 fully operational FP-2. One was transported to Italy to be flight tested with other captured Yugoslav aircraft (Do-17K and Hurricane) in early June 1941. The remaining 12 FP-2s were stationed at Tirana, but then repositioned in May 1941 to Shkodër to join the 5° Gruppo, which was part of the 39ª Squadriglia. This unit was equipped with older IMAM Ro-37 aircraft. As these were prone to malfunction, the Italians simply reused the FP-2 and pressed them into service. They were mainly used for liaison missions between Tirana and Shkodër. But Partisan activity began to increase in the area and faced with a lack of any other aircraft, the Italians began to arm the FP-2s. The FP-2s were armed with machine guns taken from the Ro-37 aircraft.

The 39ª Squadriglia would be operational until June 1943 in the Shkodër region. It was then returned to Italy and, while it is not clear, there is a chance that at least three FP-2 were still operational with this unit. The final fate of the FP-2s in Italian service is unfortunately not known.

In NDH Service 

After the April War ended, the Germans captured all surviving aircraft production factories, including Zmaj, in Yugoslavia. They restarted production for their own needs. The newly formed NDH (Independent State of Croatia) puppet state asked the Germans for a number of aircraft for their newly formed air force. This included any available Yugoslavian aircraft that survived the war. The Germans supplied the NDH with FP-2s captured in Sarajevo during the war.

In the case of the FP-2s at the Zmaj factory, there were engines and parts for the incomplete fifth production series that could potentially be built. The Germans delayed any decision whether to allow the NDH to take these aircraft. In 1943, an arrangement was reached between the NDH Aviation Force officials and the representatives of Zmaj for the delivery of the 15 FP-2 aircraft. The production process was slow due to the lack of a qualified workforce and constant sabotage by resistance movements. By 1944, only eight FP-2s were completed for the NDH. The remaining seven would remain in Zmaj factory hangars until they were captured by the victorious Communist Partisan forces in October 1944. 

During the war, the NDH Air Force used the FP-2 in its original role of a training aircraft. As the Partisan activity began to rise, some FP-2s were modified by adding bomb racks for six 12 kg (27 lb) bombs. These were then used to fight the Partisans, but as neither the pilot nor the observer were supplied with parachutes, these operations were dangerous.

FP-2 in Croatian service during the Second World War. [histaviation.com]
By 1944, it was obvious that the Axis were on the losing side and, for this reason, many NDH pilots tried to escape to the Partisan side whenever it was possible. One of them was Mitar Оbućanin. While flying an FP-2 (6822) in late August 1944, he escaped to the Partisan held island of Vis. This plane would be used by the Partisans for reconnaissance and liaison. Another attempt was made in October by pilot Drago Markotić and assistant Milan Aćimović. The escape failed and the plane was shot down by German AA ground fire. The pilot was captured and executed but his assistant managed to escape.

This FP-2 (6822) is the plane in which Croatian pilot Mitar Оbućanin defected to the Partisan side. It was then put into service by the Partisans from the isle of Vis. The FP-2 received a large Red Star painted on its side.[vazduhoplovnetradicijesrbije.rs]
The NDH had around 23 FP-2s in their Air Force. The aircraft supplied by the Germans received serial numbers 6801 to 6815 and the ones acquired from Zmaj were 6816 to 6823.

After War Service

With the liberation of Zemun, where the Zmaj factory was located, seven incomplete FP-2s were found abandoned. By late April 1945, two FP-2s were completed and put to use by the new Communist Yugoslav Air Force. The last five were completed by mid 1945. In total, around 13 were operated by the Yugoslav Air Force after the war. They would not remain long in service due to a lack of spare parts. They were mostly used as a target tug to haul flying targets for ground AA crew training.

The parts of one FP-2 can now be seen at the Belgrade Aviation Museum near the Nikola Tesla Airport.

Side view of the FP-2. [airwar.ru]
One of the 13 FP-2s operated by the new Communist Yugoslav Air Force after the war. [vazduhoplovnetradicijesrbije.rs]
 

Production

The FP-2 was produced in several batches from 1934 to 1940. The first batch consisted of 20 aircraft, followed by a second one with 15 planes in 1937, another 15 planes in 1939, and the final batch of 15 in 1940. An additional 15 planes were to be built in 1941, but due to the outbreak of the war, this was never completed. 

Before the war, the total production number of FP-2s made by Zmaj was 65 aircraft, plus the prototype. During the war and, in small numbers, after the war, an additional 15 were built. In total, 81 FP-2 were built.

Modifications

  • FP-2 – Main production version
  • FP-2H – A proposed naval version powered by the K-9 engine, but not adopted for service.

Operators

  • Kingdom of Yugoslavia – Used some 66 planes for pilot training.
  • SFR Yugoslavia – After the war used seven aircraft of this type. They were all captured at the Zmaj factory. These planes were designed for the NDH but never delivered on time.
  • NDH – A dozen aircraft of this type were delivered to the Air Force of the NDH in 1941 by the Germans. In 1944, another eight aircraft were delivered from the Zmaj factory in Zemun.
  • Italy – Used 13 captured planes from May 1941 to June 1943 against the rebels in Montenegro and Albania.
  • Germany – Captured smaller numbers of FP-2s but did not use them.
FP-2 Specifications
Wingspan 35 ft 5 in / 10.8 m
Length 25 ft  11 in /  7.9 m
Height 9 ft 6 in / 2.9 m
Wing Area 310 sq ft / 28.8 m²
Engine One Gnome-Rhone 7K, 7-cylinder radial, 313kW (420 hp) engine
Empty Weight 1.630  lbs / 740 kg
Maximum Takeoff Weight 3.170 lbs / 1,450 kg
Maximum Speed 148 mph / 238 km/h 
Cruise speed:  124 mph / 200 km/h
Effective range 360 mi / 580 km
Maximum Service Ceiling 22,300 ft / 6,800 m 
Crew Two (Instructor and student)
Armament None

Gallery

Illustrations by Carpaticus

FP-2 in Croatian service during the Second World War
FP-2 in Italian Service – 39ª Squadriglia

Credits

  • Article by Marko P.
  • Edited by Stan L. and Ed J.
  • Illustrations by Carpaticus
  • Č. Janić i O. petrović (2011) Kratka Istorija Vazduhoplovstva U Srbiji, AEROKOMUNIKACIJE Beograd.
  • D.Babac (2008), Elitni Vidovi Jugoslovenske Vojske U Aprilskom Ratu, Publish.
  • Vojislav V. Mikić (2000) Zrakoplovstvo Nezavisne Države Hrvatske 1941-1945, Vojno  istorijski institut Vojske Jugoslavije
  • Vojislav V. Mikić (1998) Italijanska Avijacija u Jugoslaviji 1941-1943, Vojno  istorijski institut Vojske Jugoslavije
  • B. Nadoveza and N. Đokić (2014), Odbrambena Privreda Kraljevine Jugoslavije, Metafizika Beograd.
  • T. Lisko and D. Čanak (1998), The Croatian Air Force In The WWII, Nacionalna i sveučilišna knjižnica, Zagreb
  • F. Vrtulek (2004) Ludbrežanin Inženjer Rudolf Fizir, Podravski Zbornik.  
  • http://www.vazduhoplovnetradicijesrbije.rs/index.php/istorija/229-fizir-fp-2

Ikarus MM-2

WW2, Yugoslavia, ,

Yugoslavia flag Yugoslavia (1939)
Prototype Advanced Trainer – 1 Built

The MM-2 prototype had an unusual color scheme with a combination of red and polished aluminum.

With the emergence of new fighter planes in the years leading up to the Second World War, it became necessary to replace the older biplane trainer aircraft, which were too slow, in order to efficiently train new pilots to fly the newest fighters. Thus, it was logical that more modern advanced trainer aircraft would be needed. The MM-2 was an experimental Yugoslavian solution to this problem.

First Steps

At the end of the thirties, the Yugoslav Air Force was equipped with modern planes, such as the German Me-109, the indigenous IK-3, and the British Hurricane, highlighting the need for an updated trainer. There were several older aircraft in use for the role, like the FP-2 and the Rogožarski PVT, with a maximum speed of around 140 mph (230 km/h) but there was a need for a much faster and modern aircraft trainer.

The designer of the MM-2 trainer, Captain Dragutin Milošević.

To fill this gap, Air Force engineer and pilot Captain 1st Class Dragutin Milošević, on his own initiative, began to work on a new advanced trainer in 1936. The first aerodynamic calculations, choice of engine, structure, and the design were done by 1937. This new plane was conceived as a two-seater with seats one behind the other, with an enclosed cockpit and dual controls. It had a low wing, mixed construction, with a single engine and retractable landing gear. The engine would have been the Renault 6Q-02, giving 162 kW (220 hp). Milošević never gave a designation for this plane, but was later simply named the M-1.

Captain Dragutin Milošević submitted this project to the Yugoslav Department of Aviation in 1937. The Department analyzed this proposal and, while on paper it would have had great flying performance, a decision was made to reject it because the parts necessary for its construction had to be imported from abroad.

This decision did not discourage Captain Milošević, and he made attempts to improve his design. He proposed replacing the Renault with the license-built Gnome-Rhone K-7 309 kW (420 hp) air-cooled 7-cylinder engine. By adding this engine, the length of the plane would be reduced from 23 ft 7 in to 20 ft 4 in (7.2 m to 6.7 m) but the total weight increased to 2,160 lbs (980 kg). To improve the landing characteristics of the aircraft, it would have been necessary to increase the distance between two front landing wheels from 6 ft 2 in to 7 ft 10 in (1.9 m to 2.39 m). All aerodynamic and statistical calculations were finished by 1939. The second version was named M-2 and it was, in essence, the basis of the future MM-2 aircraft.

One wooden model (1:10 scale) was built by the Albatros factory in Sremska Mitrovica. This model would be used to test the aerodynamic properties and accuracy of earlier calculations. Aerodynamic properties were tested in the Paris wind tunnels on the 17th and 18th of July 1939. After these trials, the fuselage length reverted to the original 23 ft 7 in (7.2 m).

Later, Captain Milošević did new calculations that showed that certain changes to the design of the aircraft were necessary. Adding weapons and increasing fuel capacity would lead to an increase of the mass of the M-2 by 242 lbs (110 kg), some 60 lbs (30 kg) in fuel and 176 lbs (80 kg) in armament. After all the other modifications, the total mass reached 2,782 lbs (1,262 kg) compared to the initial 2,160 lb (980 kg). The wing area had to be increased from 129 to 146 sq ft (12 to 13.6 m²) and the wingspan from 27 ft 10 in to 30 ft 3 in (8.5 to 9,23 m).

Adoption of a Prototype

Captain Milošević submitted a letter, together with documents, plans and calculations, to the supreme headquarters of the Yugoslavian Air Force, notifying them of the test results of the proposed M-2 aircraft. Since he did not receive any kind of response, he asked Major Đorđe Manojlović, also an aviation engineer, for help. Although Đorđe Manojlović did not have a direct impact on the design of the M-2, his great influence and connections in the Supreme Air Force Command lead to the continuation of the project. The cooperation of these two men lead to the final approval for construction of the M-2 aircraft project.

The only MM-2 prototype during its construction by Ikarus.

When the Air Force Headquarters of the Army of the Kingdom of Yugoslavia accepted the M-2, construction of this project was given to the Ikarus factory. The contract was signed on the 25th March 1940. It was planned to build one prototype aircraft for testing in order to ascertain if the M-2 was fit to be accepted for serial production. The project was monitored by a team composed of engineer Sava Petrović, Air Force Major Vojislav Popović and the technician Stefan Lazić. The prototype was ready by the first half of November 1940.

Origin of the Name

In the Kingdom of Yugoslavia, there was a custom of using the initials of the names of the designers as the official designation for most of new types of aircraft in service (like the IK-2/3), and MM-2 was no exception. MM comes from the initials of the surnames of Captain Dragutin Milošević and the constructor and engineer Major Đorđe Manojlović. There is sometimes confusion about the exact name of this aircraft. It is sometimes also called MiMa-2. In some documents found after the war, it is also called M.M. 2. In this article, the MM-2 name will be used, as it is the most common.

Technical Characteristics

Captain Dragutin Milošević’s first drawing of the MM-2. Note that the engine nose design appears to be for an inline engine, different from the actual prototype.

The MM-2 was designed as an advanced two-seater trainer, with seats one behind the other, with dual controls and a fully enclosed cockpit. It was a low wing, mixed construction, a combination of wood and metal, single engine aircraft with retractable landing gear.

The wings had a trapezoidal shape with a rounded top. They were constructed by using two racks which were made of steel tubes welded together. The racks were welded to the plane’s hull and the wooden ribs were connected to them by rivets. The wings were covered with canvas, except for the central parts, which were made of aluminum sheet. This was done so that the technicians and repair crews could have easy access to the inside of the wing. The ends of the wings were made of wood that were held in place by steel fittings. The flaps were covered in canvas and operated either manually or hydraulically.

The MM-2 hull was of mixed construction. The main body was made by using welded pipes. The front part was covered with aluminum sheet and the rear with canvas. The tail was made mostly of wood and covered with canvas.

The main engine was the Gnome-Rhone K-7, which supplied 310 kW (420 hp). It was domestically built under license from Franch aircraft manufacturer Rakovica. It was hoped to use a two-bladed metal propeller but, due to the lack of resources, wood was used. The maximum estimated speed (never achieved) was around 250 mph (400 km/h), with an effective range of 475 mi (764 km) with some 40 gallons (150 l) of fuel capacity. Climbing to 6,500 ft (2,000 m) could be achieved in 3 minutes and 9 seconds, but the maximum service ceiling was never adequately tested.

The landing gear was supposed to be of the ‘Nardi’ type imported from Italy, but it was planned to domestically build the landing gears for the production version, to avoid being dependent on foreign countries. On the prototype, no radio was installed but it was hoped to equip all future production aircraft with the FuG VII radios.

The main armament consisted of two wing-mounted 7.7 mm Darn-type machine guns with 175 rounds of ammunition for each gun. The total bomb load consisted of four 10 kg bombs carried under the wings. It must be noted that the armament was never installed on the prototype, as testing was interrupted by the beginning of the war.

First Test Flights

MM-2 Side View

The first test flights were made by the beginning of the 1941 at the Zemun airport. The pilot for these flights was Vasilije Stojanović, the test pilot of the Ikarus factory. By the end of March 1941, some 45 flights had been made with a total of 20 flying hours. The pilot assessed the flying performance of this plane as excellent. The results of these tests indicated that this aircraft had good flight performance. The controls were adequate, both instructor and the students cockpits had enough room with a good field of view and, during flights, the aircraft did not present any tendencies for sudden unpredictable movements. Due to its good air brakes and flaps, take-offs and landings were quite easy. There were no major objections from the test pilot about the MM-2.

The MM-2 could very easily reach speeds of up to 217 mph (350 km/h). The design maximum speed was never tested, but calculations suggested that it could be as high as 250 mph (400 km/h). This was never confirmed due to the outbreak of the war. The MM-2 prototype had an unusual color scheme with a combination of red on most of the rear fuselage and wings, and polished aluminum on the majority of the fuselage and the engine section, with a small Yugoslav flag painted on both sides of the tail.

On the 25th of March 1941, a contract was signed between Ikarus and the Air Force. According to this contract, Ikarus was to prepare for production of MM-2 trainer planes in the near future. Before the production would begin, a last series of tests was to be conducted by a test group at an airfield near city of Kraljevo. An order was given to Stojanović to fly the MM-2 from Zemun to the Kraljevo airfield. Once there, it was planned to do some more flight performance trials in order to examine the limit of the flying characteristics of the MM-2 aircraft. Stojanović completed the flight on the 4th April. Final production was never achieved due to the German invasion of Yugoslavia that started only a few days later.

Operational Service

The MM-2 did not see any active service in the Royal Yugoslav Army because of the beginning of the April war, the German attack on Yugoslavia in April 1941. After the defeat of the Yugoslav army, the Independent State of Croatia, or NDH, was created. In order to form the new NDH military air force, it was necessary to find and obtain planes to equip these new units. Like many other former Yugoslav planes, the MM-2 was also pressed into NDH service in a very limited role.

It seems that the MM-2 had some engine problems (possibly sabotaged) when it was captured by the Germans at airfield near Kraljevo. It is possible that it was in a bad condition since the Germans did not even bother to repair it and put it into operational use.

The MM-2, together with other Yugoslav captured aircraft, was collected and handed over to the NDH. After a while, the MM-2 was repaired under code name No. 6301, and returned to active service. Additional flight tests were conducted by Georgije Jankovski, a test pilot for Dornier-Werke. In September 1941, the plane was transferred to the Zemun airport and handed over to Croatian Major Ivan Pupis for future use. Major Pupis was the leader of the group responsible for the repair, reception and later transfer of all Yugoslavian aircraft captured during the April war. When the MM-2 was repaired and ready for active service, Pupis to keep it for his personal use rather than handing it over to the military.

On the May 13 1942 pilot Vid Saić, he lost control of the aircraft and crashed due to inexperience. The MM-2 was deemed too complicated and expensive to repair.

The MM-2 was ‘owned’ by Pupis until March 23rd, 1942, when he received a direct order from the Croatian Aviation Command to transfer the MM-2 to the ‘Rajlovac’ airfield near the city of Sarajevo in Bosnia. The aircraft arrived at the beginning of April 1942. The MM-2 was given to the 17th Squadron (Jato) which was part of the 6th group (Skupina) under the Command of the Major Romeo Adum. The MM-2 was used mostly for limited test flights. On May 13, 1942 while piloted by Vid Saić (from the 18th Squadron), the plane crashed. The pilot survived the crash with no injuries. A commission was formed to investigate the causes of the crash and found several irregularities: The pilot did not ask for permission and had no orders to fly on the MM-2 that day, and he also did not know anything about the flying characteristics or the condition of the plane. The conclusion was that the pilot was guilty for the accident and, as punishment, Vid Saić lost his Pilot rank. The damage to the MM-2 was estimated to be around 90%. There was no point to try to rebuild it from scratch and the remaining parts were destroyed. There is no information whether it was equipped with any armament in Croatian military service.

Production

Due to the outbreak of war on April 6th, 1941, except for the prototype, no other specimen of this aircraft was ever built. In some documents and letters found after the Second World War, it was discovered that the Ministry of Aviation planned to order around 50 copies of the MM-2 aircraft. Along with this, the Yugoslav military negotiated with Germany for the purchase of Arado Ar 96 training planes, but nothing came of this.

After the war, the new communist Ministry of Aviation and the Ikarus factory representatives were also interested in restarting the production of this aircraft but, as the chief designer had died in one of the many German prison camps and the necessary machines and tools were lost during the war, this was too difficult and was abandoned.

Operators

  • Kingdom of Yugoslavia – Built and tested the single prototype.
  • Independent State of Croatia NDH – Used the MM-2 captured during the April war, but it was lost in an accident.

MM-2 Specifications
Wingspan 30 ft 6 in / 9.23 m
Length 23 ft 7 in / 7.20 m
Height 9 ft 6 in / 2.89 m
Wing Area 14.6 ft² / 13.60 m²
Engine One Gnome-Rhone K-7, 309 kW (420 hp) air-cooled 7-cylinder engine
Empty Weight 1,071 lbs / 894 kg
Maximum Takeoff Weight 2,290 lbs / 1,330 kg
Fuel Capacity 150-160 l
Maximum Speed 250 mph / 400 km/h
Cruising Speed 390 mph / 630 km/h
Range 475 mi / 764 km
Maximum (estimated) Service Ceiling 6,600 ft / 2,000 m
Climb speed Climb to 2,000 m in 3 minutes and 9 seconds
Crew Two, instructor and student pilot
Armament
  • Two Darn M30 7.7 mm machine guns in wings
  • Total bomb load around 40 kg.

Gallery

Illustration by Haryo Panji https://www.deviantart.com/haryopanji

Ikarus MM-2 Side View [Haryo Panji]
MM-2 Front View
MM-2 Rear View

Sources