# Ikarus IK-3



## Milos Sijacki (Oct 29, 2007)

The Rogožarski IK-3, a low wing monoplane single seat interceptor fighter with retractable landing gear, was a product of the design team of Ljubomir Ilić and Kosta Sivčev as a follow on to their IK-1/IK-2 fighter. Joined by Ing. Zrnić, they initiated the design in 1936 under strict secrecy, wind tunnel testing was done in France, before submitting the design to the Yugoslav Air Ministry. Construction of the IK-3 was assigned to Rogožarski A. D. in Belgrade and the prototype flew for the first time in the spring of 1938.
Artist vision of encouter between IK-3 and Me
Artist vision of encouter between IK-3 and Me

The IK-3 was powered by a Hispano-Suiza 12Y-29 liquid-cooled inline engine that was rated at 890 hp for take-off and at 920 hp at 11,810 feet 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 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 Hawker Hurricane.
Pilots of 51st fighter group in Zemun airport 1940,behind pilots is IK3 fighter.
Pilots of 51st fighter group in Zemun airport 1940,behind pilots is IK3 fighter.

Six test pilots flew the prototype in a very successful test program before it was lost. On January 19, 1939 the test pilot, Captain Pokorni, after a series of acrobatic maneuvers entered a terminal velocity dive from which he did not recover. After an investigation the aircraft was found not at fault and the Air Ministry ordered an initial lot of twelve aircraft.

The production IK-3 was refined with a number of changes including modifications to the sliding cockpit canopy, addition of a bullet proof windshield, and installation of the Avia H.S. 12Ycrs inline engine, a Czech built version of the Hispano-Suiza installed in the prototype. 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. But before the second lot of IK-3 could be started German forces invaded Yugoslavia.

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 to various extents were an upgraded 1,100 hp Hispano-Suiza 12Y-51, the Daimler-Benz DB-601A, and the 1,030 HP Rolls-Royce Merlin III engines. Also, Rogožarski was pursuing a new fighter design, the IK-5, 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.

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 an air accident before the war, four were in workshop on scheduled services and repairs and one aircraft was undergoing modification to Series II IK-3 standard in Rogozarski airplane factory. Six remaining IK-3s were allocated to 161st and 162nd fighter squadron (3 IK-3 each) of the 51st Fighter group. 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.

Operators

* Kingdom of Yugoslavia

General characteristics

* Crew: one, pilot
* 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: 4,123 lb (1874 kg)
* Loaded: 5,291 lb (2405 kg)
* Maximum takeoff: lb (kg)
* Powerplant: 1× Avia-built Hispano-Suiza 12Ycrs twelve cylinder Vee liquid-cooled engine, 920 shp (686 kW) each


Performance

* Maximum speed: 327 mph at 17,715 ft (526 km/h at 5401 m)
* Range: 310 miles (496 km)
* Service ceiling: 26,250 ft (8,003 m)
* Rate of climb: ft/min (m/min)
* Wing loading: 29 lb/ft² (113 kg/m²)
* Power/mass: 0.17 hp/lb (0.29 kW/kg)

Armament

* 1× 20 mm Hispano-Suiza HS-404 cannon
* 2× 7.92 mm FN-Browning machine guns


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## Aggie08 (Oct 29, 2007)

Cool, never heard of it before. I googled it, here are some pics.

IK


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## mkloby (Oct 30, 2007)

Good post, milos. A lot of people haven't heard of the aircraft. Definitely a great success of Yugoslav industry, although cut short.


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## Watanbe (Oct 30, 2007)

Nice, thanks for posting that I hadn't heard of it either. THe plane looks like the offspring of a Hurricane and Dewontine!!


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## Milos Sijacki (Oct 31, 2007)

Thanks guys. This plane actually was designed around Hurricane which served in RYAF. There were also plans to power the later types of this airplane with Daimler-Benz engines. This was a good fighter, but German fighter pilots were all veterans, so it wouldn't do much good anyway.


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## Watanbe (Oct 31, 2007)

Milos Sijacki said:


> Thanks guys. This plane actually was designed around Hurricane which served in RYAF. There were also plans to power the later types of this airplane with Daimler-Benz engines. This was a good fighter, but German fighter pilots were all veterans, so it wouldn't do much good anyway.



Yeh and no way could they get enough in the air to pose an real threat to the Germans! Was the design ever considered by any other Nations??


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## imalko (Aug 26, 2009)

Milos Sijacki said:


> ...This was a good fighter, but German fighter pilots were all veterans, so it wouldn't do much good anyway.



In April War of 1941 Yugoslav IK-3 pilots shot down four German aircraft and claimed one probable. One Yugoslav pilot was killed in action and two wounded.(Source: "Naša krila" magazine)



Watanbe said:


> Yeh and no way could they get enough in the air to pose an real threat to the Germans! Was the design ever considered by any other Nations??



Low production rate and production in small limited series plagued Yugoslav aircraft industry throughout the existence of Yugoslav Kingdom. I think that IK-3 was never considered by other nations, but one captured example was tested by the Luftwaffe at Rechlin. However, after the war new fighter was developed - Ikarus S-49A (picture 2 in attachment) and its advanced version S-49C - and these were based on prewar Rogožarski IK-3.

First prototype of IK-3 (picture 4) had different wind screen and was painted overall gray and with pronounced national markings including large national flag painted on the rudder. IK-3s of serial production (only 13 examples build) were painted with camouflage colors and low visibility national markings adopted by Royal Yugoslav Air Force (RYAF) for front line aircraft (picture 1 and 3).


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## Waynos (Aug 28, 2009)

Milos Sijacki said:


> Thanks guys. This plane actually was designed around Hurricane which served in RYAF. There were also plans to power the later types of this airplane with Daimler-Benz engines. This was a good fighter, but German fighter pilots were all veterans, so it wouldn't do much good anyway.



Do you mean structurally? Externally it looks much closer to the Dewoitine in the side profiles, and my oh my, with the bubble hood doesn't it resemle a Yak!


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## imalko (Dec 18, 2009)

Milos Sijacki said:


> .... There were also plans to power the later types of this airplane with Daimler-Benz engines.



Here's one drawing of Daimler-Benz powered Ik-3 project (see the atachment) and also a link for more info on Rogožarski Ik-3: IK-3_intro


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## LWulf (Dec 21, 2009)

In the fight it was hell flying the IK-3 since LW pilots could easily make out its shape, unlike for other Yugoslav pilots flying Bf 109s, which were usually only attacked after starting attacks on LW aircraft.

It's been a while since I've read "Zapisani nebu", a book on Slovenian combat pilots, but I remember them saying that while the IK-3 had lighter controls and tighter turning circle it was outperformed by the Bf 109. One pilot commented on this saying they preferred the IK-3 because of the few mock dogfights they had flying IK-3 versus the Bf 109. Not knowing any better they only turned around until getting on the tail of the other guy. The pilots emphasised many times their lack of experience in combat flying, so I am not surprised that they preferred the IK-3 over the Bf 109 E, despite the difference in performance.
From what I gathered the IK-3 was slightly slower than the Hurricane and climbed similarly, but had more responsive controls and better weapons (I guess they meant the cannon and its placement vs wing mounted MGs). I also remember that the IK-3 didn't have radios? Not sure about this tho.
IMHO the IK-3 was not on par with the contemporary fighters, despite the best efforts of the engineers behind it. :/ I still like its looks tho. 

A bit offtopic, but for a while I hoped that we might get an IK-3 in the il2 game, since there were other "only one built" aircraft, but il2 devs said that unless a user makes it they had no plans to make it. Oh well. 
I remember that in the "Freebirds" sim they had a recreation of the battle over Belgrade with Yak-1s and/or Hurricanes replacing the IK-3s. Must've been nice.

Anyway, it's good to see that this aircraft and the brave men flying it are not completely forgotten.


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## Shortround6 (Dec 21, 2009)

Waynos said:


> Do you mean structurally? Externally it looks much closer to the Dewoitine in the side profiles, and my oh my, with the bubble hood doesn't it resemle a Yak!



It looks like it was much more of a development of the Ikarus IK-2. The fabric covered rear fuselage was not uncommon at the time ( and easier to make). If you are using a Hispano V-12 engine the nose of the aircraft is probably going to be similar to other Hispano powered aircraft unless the designer really mucks things up. If it was designed in with help from a French wind tunnel then the similarity to French aircraft is easy to understand.


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## papa_bear (Dec 22, 2009)

Hello, I'm sorry for digging up this topic, but...
New model in 1/72 scale is on the market soon. Producer is AZ Models.
We still don't know is it shape good, but we know that painting instruction is very big What IF!
If you want to build good IK3, accurate model, with realistic paintjob, please do not use any drawing or profile from guy Srecko Bradic... All of his profiles are not accurate. Mostly are what if again.
I'm not supporting Nenad Miklusev, but his work is accurate nearly100%
If you want to build good Ik fighter, visit this site. Linky: IK-3_intro
Sry if I was boring...
Happy modelling,
Dada


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## imalko (Dec 23, 2009)

I was really hoping this won't be mentioned, but since it was here is a short explanation of Dada's post...
You see, there is unresolved copyright issues (which will probably see their epilogue on the court) between few Serbian authors of whom some had published works on IK-3 both in Serbian and foreign magazines. Likewise there is bitter rivalry between profile artist about whose profiles are more accurate and so on. There's no need for me to emphasize here how difficult it can be to interpret black&white photos correctly. But in my opinion this dispute (which is raging for a while now as can be seen on some Serbian aviation forums for example) is completely unnecessary. Instead of accusing each other on whose profile work is accurate or not, they should really discuss it together and try to interpret photos the best way possible and with other available data on colors used,etc came up with as accurate color profiles as possible. This would only benefit everyone.

Appearance of new IK-3 kit in 1/72 scale on the market is great news and I'm first to welcome it as such. Hope this will be accurate and good kit for enjoyment of scale modelers everywhere.

Ok, I'm done with off topic. The real purpose of this thread is to share information and discuss the Rogožarski IK-3 fighter with our forum friends from other countries. Along those lines here are few pictures taken from book "Ilustrovana istorija vazduhoplovstva".

*Picture 1:* First prototype of IK-3 which was destroyed during flight testing on 19th January 1939. Note the rounded one-piece windscreen which was later changed on production models.
*Picture 2: *Design team behind IK-3 fighter: (from left hand) Slobodan Zrnić, Ljubomir Ilić and Kosta Sivčev
*Picture 3:* Production model of Rogožarski IK-3 at Belgrade airport in 1940. The aircraft was armed with Oerlikon 20mm motor cannon and two synchronized machine guns Browning 7,92mm.
*Picture 4:* Instrument panel of the production model of IK-3.


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## imalko (Dec 23, 2009)

And few more also taken from book "Ilustrovana istorija vazduhoplovstva"...

*Picture 1:* Pilots of 51st Fighter Group of Royal Yugoslav Air Force in front of one production model IK-3 at Belgrade airport in 1940.
*Picture 2:* Three view color drawing of Rogožarski IK-3. (Artist: Danijel Frka)


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## imalko (Jan 19, 2010)

*This Day 71 Years Ago - Crash of IK-3 Prototype*

On this day, 19th January 1939, Yugoslav test pilot Captain Milan Pokorni tragically ended his life when he crashed during a test flight with prototype of Rogožarski IK-3 fighter aircraft.
After successfull initial test flights prototype of IK-3 was transferred from Test group ("Opitna grupa") to the 6th Fighter Regiment where further test were to be conducted. On 19th January it was planned to test the plane in full throttle sharp turns. First flight on that day was made by Col. Dragutin Rubčić, commanding officer of the Regiment. Flight ended with rough landing in spite of pilot's great experience. Plane struck hard to the ground with starboard landing gear leg, bounced off and then landed roughly. The plane was immediately examined by Ing. Marko Radosavljević from Rogožarski factory. With no apparent damage second flight on that day was authorized with Cpt. Pokorni in the cockpit. At the end of flight while returning to the airfield and probably in an effort to make high speed low level pass Captain Pokorni dived with IK-3 at high speed above the airfield. At one moment starboard wing broke off and aircraft crashed at the edge of the airfield killing the pilot. 
Subsequent investigation concluded that wing structural failure occurred due acumulated damage on the wing spar near to the wheel bays caused by number of rough landings during testing. Test pilot Cpt. Milan Pokorni was buried at Novi Sad.

Compiled by Nenad Miklušev - Translated by imalko

Picture 1: Captain Milan Pokorni





Picture 2: Prototype of IK-3 with Captain Milan Bjelanović in the cockpit.





Picture 3: Starboard wing at the crash site.


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## JOEJAN (May 18, 2010)

Well you probably didn't know they were planning to build IK5,but the war started,just as in 1991 for NOVI AVION... (
IK5 would probably be the best fighter in WWII,please don't sheet German planes are the best,SIZE OF THE COUNTRY DOESN'T MATTERS!
IK3 could compare to the best fighters at the beginning of the WWII,but it was outnumbered,and they didn't put fire munition on them(fools)...
IK5 pics:


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## tomo pauk (May 19, 2010)

JOEJAN said:


> ...
> IK5 would probably be the best fighter in WWII,*please don't sheet *German planes are the best,SIZE OF THE COUNTRY DOESN'T MATTERS!...



Excuse me, expert, what are the best planes?


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## imalko (May 19, 2010)

Bottom line is you can't compare aircraft which never left the drawing board to the types which saw large scale service during the war. One could argue that IK-5 had potential to be among the best twin engined fighters of the time, but since the design was never build we will never know.

I fail to see what IK-5 has to do with thread dedicated to Rogožarski IK-3 though.


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## Knegel (May 20, 2010)

Hi,

the IK-3 had very much the same specs like the MS405 and even the same engine and it looks like a hybrid of the Hurri and MS405. I guess the performence also was very similar.

Rather smal wings with an high aspect ratio and a light body. I bet with an DB601A it would have been a great high alt fighter. Though, the light weight must have had some bad drawbacks(no radio??, bad armor, self sealing tanks?? Smal amo load??).

Greetings,

Knegel


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## VG-33 (May 20, 2010)

Knegel said:


> Hi,
> 
> the IK-3 had very much the same specs like the MS405 and even the same engine and it looks like a hybrid of the Hurri and MS405. I guess the performence also was very similar.


I hope for Yougos it wasn't so. MS-405 never exceeded 450 km/h, and Hurry was a big peace of cake; it's performance was mostly due to it's 1030 hp Merlin rather to the very roomy airframe and thick wings.

With the same Hispano 880 hp power it's performance would have certainly been pityfull. So the IK-3 airframe was better than both of theese and should be compared to the very improved MS-410 (510 km/h).





> Rather smal wings with an high aspect ratio and a light body. I bet with an DB601A it would have been a great high alt fighter. Though, the light weight must have had some bad drawbacks(no radio??, bad armor, self sealing tanks?? Smal amo load??).


Why high alt? The low power request generated by high aspect ratio and a light wing loading plays a rule at any hight to outclimb or outfight in turning circles the same (what if) powered Me-109.

I don't think that IK-3 technology was more advanced that the Hurricane's, Bf-109's and MS-406 one's, but at least it was cleverly concieved (i mean optimised for it's low available power).

Like the french D-520, D-550, VG-33, soviet I-17, I-18, Czekh Avia B-135 and the rest of the unlucky underrated family...

Regards

VG-33


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## Knegel (May 20, 2010)

Hi,



VG-33 said:


> I hope for Yougos it wasn't so. MS-405 never exceeded 450 km/h, and Hurry was a big peace of cake; it's performance was mostly due to it's 1030 hp Merlin rather to the very roomy airframe and thick wings.
> 
> With the same Hispano 880 hp power it's performance would have certainly been pityfull. So the IK-3 airframe was better than both of theese and should be compared to the very improved MS-410 (510 km/h).
> Sorry, MS405 was a type, wanted to write MS406.
> ...


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## VG-33 (May 23, 2010)

Hello



> Knegel said:
> 
> 
> > Hi,
> ...


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## Knegel (May 24, 2010)

Hi,

the D-520 was smaler (wings) and had the Hispano-Suiza-12Y-45 with way more power than the Hispano-Suiza-12Y-31.

I never did read anywhere that the MS406 didnt reach 480km/h, while the MS410 should reach 510km/h??
I guess this is also mainly due to a better engine, not the aerodynamic. At this slow speeds IAS in 5000m, the aerodynamic is not as important as at sea level or with later planes, which did reach 200km/h more. 

The advantage of smal aspectratio wings over high aspect ratio wings at high speed(smal AoA) is caused the problem to shift away airmasses. As smaler the aspect ratio, as easyer the airmasses can go around the wing.

Though, at the rather slow speeds in a horizontal flight of the early planes surly this is not the most important part, like the problems of creating a stable structure with a high aspect ratio wing and the resulting disadvantage in the rolling axe caused by the longer wings.
And this is mainly a problem in low alt, where the propeller/engine produce way more thrust than in high alt.

There is a reason why some jets got movable wings and why high alt planes in WWII got extended wings, while low/medium alt fighters had a smal aspectratio.

You wrote: "I cannot understand your logic and TAS, IAS matters."
As more thrust a plane have, as smaler will be the relative AoA he use, cause his speed will be higher. 

In high alt(lets say 7000m), the Hispano engine had just around 50% of its max power and the thin air reduced the thrust even more. So at this altitude the plane for sure couldnt loop anymore and had trouble to make a barrel roll, without an big altitude drop.
Under such circumstanes the structural problems of an high aspect ratio wing dont matter much anymore, cause high g-forces are not expected, but the plane always need a rather high AoA, even to maintail altitude.

In low level, the engine/propeller produce most thrust and so the plane only need a very smal AoA to maintain altitude. 
Here the planes get into high G force fightes, where the wings tend to bend and break appart and where this structural limits and the pilots ability to withstand high g-forces turn to be the limiting factor for the turn and roll.

So all over the in the middle used AoA will be way smaler than above critical altitude, in same degree the advantage of the high aspect ratio wing smelt down, while the disadvantages increase.

As result the FW190D9 is faster and more manouverable than the Ta152H in low alt. Same goes for the Spitfire with clipped wings.

Greetings,

Knegel


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## VG-33 (Jun 16, 2010)

Hi,



> the D-520 was smaler (wings) and had the Hispano-Suiza-12Y-45 with way more power than the Hispano-Suiza-12Y-31.



It’why i have wrote



> [I*]With the same 860-880hp Ycrs engine, *the D-520 was able to reach 510 and + km/h, the MS 410 509-511, the Arsenal VG-33, 558 km/h. And the Laté 298, 310 km/h…[/I]


In other way it’s making no sense. We can compare also with an experimental MS-406 fitted with the same HS 12Y 45:
493 km/h at 5500m for the MS-406
534 km/h for the D-520. 
We can also report, that D-520 aiframe evolved from the first trials with an HS Y-31 and the later with HS Y-45 ones.




> I never did read anywhere that the MS406 didnt reach 480km/h, while the MS410 should reach 510km/h??


As previously, i have already asked to that question:



> _Mainly to exhaust blow-effect pipes, a much improved (less draggy) coolant system. Some better little aerodynamic details, without great importance on their own, witch taken altogether make the difference_.



The MS 410, had a different wing and a tunneled radiator, and numerous other details to make it faster. (SN° 1028, 1040). 
With hispano-suiza blowing pipes, instead of the bronzavia collector, the speed was improved from 44 to 41 km/h on SN° 1035, 1005 airframes. Some sources quoted that SN° 1035 had a fixed tunneled radiator during the trials, so the blow effect was _only _for 20-25 km/h increase, still not negligible indeed.*




> I guess this is also mainly due to a better engine, not the aerodynamic. At this slow speeds IAS in 5000m, the aerodynamic is not as important as at sea level or with later planes, which did reach 200km/h more.



There might be some discrepancy between the serial engines, but no global increase in power from early to late Y-31 was never reported, at least some reliability improvements.



> The advantage of smal aspectratio wings over high aspect ratio wings at high speed(smal AoA) is caused the problem to shift away airmasses. As smaler the aspect ratio, as easyer the airmasses can go around the wing.



Shift away? At sustainted flight the downwash is exactly the same for a 5 asect ratio or a 10 AR wing. For a 3000 kg airplanes, it makes exactly 3000 kg/s rate of flow in both cases. Except that at higher AoA the high AR wing does it better, at lower drag coast. At minimal Cd point (Cd0), no differences, at lower and negatives AoA the small AR had lower Cd values, but what’s the use for that? Look on Cl/Cd polars.



> Though, at the rather slow speeds in a horizontal etc etc....In low level, the engine/propeller produce most thrust and so the plane only need a very smal AoA to maintain altitude.


All that seems confused and badly assimilated in your reply. Take advantage of your banishement to read good mechanics of flight books...




> As result the FW190D9 is faster and more manouverable than the Ta152H in low alt. Same goes for the Spitfire with clipped wings.


The Ta-152 had bigger wings, with higher AR; it was more manouvrable in turing circles (both due to higher lift and lower induced drag values) and climb than the D9 even at low alt; worse on roll, pure speed, diving. This with the same engine power, but with uncertainlies about the increase of weight due to the bigger (heavier) wing. I supposed no increase of Wing Loading value at least. 


Just to say, the french company Azur had recently released a good-looking plastic kit 1/72th scale of the Rogozarski IK-3. Saw it two weeks ago, seems detailed and accurate, but i’m not the IK-3 specialist...

for instance
Maquette Azur FR013 Rogozarski IK-3 'Belgrade Defence'

Regards

* Mach 1, encyclopédie de l'aviation, n°88,89.


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## Milos Sijacki (Apr 5, 2012)

Ikarus S-49 combined elements of both YAK fighters and Ik-3. For example, in that picture, you can see YAK nose and IK-3 tail.


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