The roadmap is there, The Block III were supposed to be the "true stealth" variant. While Block I and II is for maturation and weapons integration.
im confused as i read on recently

Block I - maturation airframe and equipment, Integration

Block II is supposed to be Stealth but I read that it was an upgrade from Block 1... to Block 2 but not the internal weapon bay.. semi-Stealth also uses 6th generation equipment Radar and data network, and test and operators use these.

Block "EX" "not called block III" is Internal Weapon Bay (True stealth variant) also the 6th generation not the 5th.

there is no block III :S

I will double recheck these...

Poland (more likely to get Block II or EX as they have been enquired about these) and S.Arbabic (I think they will go KAAN indeed), and Ukraine are interested purchase these (also they are interested buy KAAN too).
 
KF-21 Block I
The block I focuses on the air-superiority capabilities.

KF-21 Block II
After further developments, the KF-21 will become a swing role fighters with attack and reconnaissance capabilities added.

Potential variants
KF-21N
In September 2022, KAI unveiled a model of the KF-21N, a carrier-based version of the fighter. In May 2022, the Ministry of National Defense (MND) decided to drop funding for the CVX, a planned small aircraft carrier capable of operating STOVL F-35B jets. It was later clarified that the MND would consider purchasing a larger aircraft carrier design, if a maritime jet fighter could be developed indigenously. Anticipating this, KAI began a preliminary design concept to make the KF-21 carrier-capable. The wings are 20% larger to ensure safety and stabilization when taking off and landing, and they fold for more compact storage. Structural changes would make the airframe capable of CATOBAR and STOBAR operations.

If the Republic of Korea Navy (ROKN) decides to procure an aircraft carrier large enough to operate fighters and identifies a requirement, KAI claims it would be able to build the KF-21N "in a few years.

KF-21EA
One of the three new variants revealed in June 2024. Will serve as an electronic warfare aircraft comparable to the EA-18G Growler. This variant would be based on the two-seat KF-21B, with a position at the back for the electronic warfare officer.

KF-21EX "Block III" (Change name to "EX")
One of the three new variants revealed in June 2024. Will reportedly be a fully stealth variant with reduced radar cross section and internal weapons carriage. It is also expected to integrate the Next Air Combat System (NACS), a combat network for the air force.

KF-21SA
One of the three new variants revealed in June 2024. Will reportedly be a variant specifically dedicated to the export market, with opportunities for the client to modify the aircraft.
 
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The naval Boramae sounds interesting djpowell1984, but why the indecision between CATOBAR and STOBAR operations? I thought that CATOBAR would be the best option for the South Korean Navy as that would offer better options for especially where large aircraft are concerned like naval AWACS and for COD.
 
The naval Boramae sounds interesting djpowell1984, but why the indecision between CATOBAR and STOBAR operations? I thought that CATOBAR would be the best option for the South Korean Navy as that would offer better options for especially where large aircraft are concerned like naval AWACS and for COD.
Agreed, I think KF-21 "N" i think it is a good option for Carrier for South Korea, (Better over F-35 "B" as local so supports local jobs and common part of repairing or replacing part for Air Force and Navy Air force S.Korea,) STOBAR/CATOBAR carrier.

CATOBAR / STOBAR i think both will work well, STOBAR might cheaper to build than CATOBAR. yet might limited CATOBAR ie AWCAS etc.

I think Naval AWACS in the future, we will more like will be Sea Guardian type with aew pod - not E-3 Hawkeyes type.

which STOBAR are better optional (I think E-3 modern Hawkeyes will be good as Manned compare to in event the Jammer (gps) or hack, or cant connection to Sea Guardian) if they want this - hawkeye so CATOBAR will better optional yet will stress airframe and reduce life service compare to STOBAR (which they more airframe life due no stress by CATO.)
 
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10 Indonesian Lawmakers Visit South Korea for Meeting with Foreign Affairs Committee "No Leakage of Sensitive KF-21 Data" Indonesia and South Korea Reach Consensus on Continuing Defense Cooperation

In September last year, Indonesia officially informed South Korea’s Defense Acquisition Program Administration (DAPA) that it would only be able to negotiate amendments to the agreement once the engineers were cleared of allegations.

Recently, Indonesia has also requested a temporary return of the five engineers, who are currently under a travel ban and under investigation, ahead of the upcoming Ramadan period.

The Gyeongnam Provincial Police Agency, which investigated the case at DAPA’s request, concluded its investigation in December last year and forwarded the case to the prosecution. However, the prosecution requested further investigation, leading to an ongoing inquiry.

So far, it has been reported that the USB devices, which were confiscated when the Indonesian engineers were caught attempting unauthorized data transfers, did not contain sensitive KF-21-related information.

Additionally, the photos taken from monitors could have been obtained through formal requests to KAI, suggesting procedural violations rather than breaches of classified information.

However, the combined impact of Indonesia’s reduced financial contribution and the data leak controversy has led to a deterioration in South Korean public sentiment toward Indonesia.

A government source stated, “As far as we know, no confidential or sensitive materials were leaked during the investigation. However, public opinion must be considered. Various options are being explored to sustain cooperation with Indonesia on the KF-21 project, and working-level discussions are ongoing.”

Some experts argue that a pragmatic approach is necessary, considering Indonesia was the first major customer of South Korea’s now globally recognized defense industry. They also point out that despite the 2011 hotel intrusion incident involving Indonesia’s special envoy and South Korea’s National Intelligence Service, Indonesia did not escalate the matter, demonstrating its longstanding cooperation.

Representative Yoo Yong-won of the People Power Party, who attended the meeting with Laksono, stated, “Indonesia was the first customer of our country’s aircraft exports and remains a key client of K-defense, having purchased the KT-1 basic trainer, T-50 advanced trainer, and even submarines.” He added, “During the meeting, we emphasized that Indonesia, as a partner in the KF-21 project, is successfully carrying out this win-win initiative between the two countries and highlighted the importance of defense cooperation between South Korea and Indonesia.”

Representative Yoo further stated, “Regarding the security incident involving Indonesian engineers, the South Korean government and National Assembly are making every effort to resolve the issue. We have asked the Indonesian side to trust us and actively cooperate in addressing the matter.”
 
So when will we be seeing Indonesia finally signing for the Boramae? They have been quiet lately in regards to the future purchase of the KF-21.
 
So when will we be seeing Indonesia finally signing for the Boramae? They have been quiet lately in regards to the future purchase of the KF-21.

In September last year, Indonesia officially informed South Korea’s Defense Acquisition Program Administration (DAPA) that it would only be able to negotiate amendments to the agreement once the engineers were cleared of allegations.
 
 
Is this still up to date on the KF-21 Treatment ?

1740662040947.png

Basically showing that the Radar absorber treatment are limited to surfaces, radome is a bandpass design while the canopy has no RAM but conductive and matched to the airframe electrically (just in case people wonder what is the meaning of electrically matched is no electrical discontinuity between the canopy and airframe).

I have the fuselage ready. Soon the other surfaces, flaps and internals.

1740663959228.png

As for absorber.. i will use Hexaferrite and Honeycomb composite RAS. Basically similar as one i use for my Su-57 estimate.
 
With clean config? Yes obviously. But the lowest it can get with a combat load? Maybe with semi-conformal Meteors only, but there's no way this is achievable with underwing pylons, drop tanks and pods:

GeXVJ7KW8AAxfws.jpg

I'm sure that, if ROKAF keeps pursuing it instead of choosing to divert those funds for the future Korean 6th gen, it'll become something that competes with J-&F-35 (and AMCA when it takes shape). But Boramae is, in its current form, NOT a fifth gen - this is just a fact.

It is more like a 4.75th gen due to its differences to other "4.5th" gens such as the Rafale or the F-15EX. They could've chosen to develop something more ambitious but this is the risk-averse project management route that they've taken due to their urgent need to replace aircraft.

1-2.png
diffraction.jpg
f-35-inlet-again-l-band.png
2-1.png

The main advantage the current variant has over other "4.5th" gens is that it places more importance into having a LO shape and seemingly also has MADL or DTS-03 like equipment.

message-editor%2F1619795549072-ifdl-madl.jpg


Second of all; even though we've all initially thought that it was a just demonstrator for testing some of J-36's capabilities before its emergence; recent developments suggest that J-20S has garnered enough interest from PLAAF and is also going to enter the service's inventory.

Edit: And Sukhoi is also devoloping not just a twin seater Su-57 but a twin seater Su-75 as well.

Su57-biplace.jpg
official-models-of-revised-su-75-variants-twin-seat-single-v0-inqalmpxxkfd1.png

the Traditional-style IRST also has a huge effect on the—without a doubt most critical—frontal RCS. There are also some other small improvements to be made, but even as it is, it's a pretty kickass plane.

My personal guess, using the good old Mk1 Eyeball, in a situation similar to what I've described as the 'lowest combat load RCS,' would be around 0.2–0.3, but it's not like I actually have the means to back this up...
 
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So, here it is.. some improvements to my KF-21 RCS Estimates, compared to years ago. things have improved. bit, with hopefully better model.

Clean topInlet ductingEngineSome frontal detailsIRST and the bird slicers
CleanTop.png Ducting Systems.png F414GE.png Grilles.png IRST-IFF.png


The treatment are as mentioned in old Sheldon's image, limited to surfaces and inlet system. The material used are RAS (Radar Absorbent Structure) in movable surfaces and RAM coating (Hexaferrite) paint for large surfaces.

Treatment.png

For armed configuration, it's pretty much similar as what was promoted back then. With full load of Meteor missiles, K-TGP, External fuel tanks and some "Indonesianized" payload.. namely the AIM-9X instead of Iris-T and GBU-32 JDAM, something that we have ready in stock, thanks to Falcon-Star program.


As for the comparison, the estimates will cover Clean and Armed configuration. The estimates will be compared with some 4 and 4.5 gen aircrafts i previously estimated e.g Su-35, Rafale and F-16's. Those which representative for what the current Block I and soon II KF-21 are designed to be comparable with. For clean configuration, there are 2 "variants" namely one with gunport open and the other closed. KF-21 have frangible cover like Dassault Rafale for gunport.


Which can be seen above, left image depict closed gunport while right one is open. As for result. The frequency used in the estimate is from VHF down to X-band (150 MHz up to 14 GHz). With some interactions as follows :

CleanArmed
KF21CleanPhysics.gif KF21Armed.gif

As for graphical results :

Clean ConfigurationsArmed Configurations
CleanKFX.png Armed Configuration.png

For armed configuration comparison, this is what's the "opponent fighter"'s armed configuration

RafaleSu-35S
Rafale-A2G-weapons.png GFfyvUEaAAALAVi.png

My conclusion is that the current Block 1 is pretty much meet what was Korean and our designers (afaik it was Indonesian designers insistence to go with conventional instead of Delta canard layout) envisaged back in 2010's, that early iteration will be Reduced RCS. With some edge against the current Gen 4.5. Tho the reduction seems bit modest like in order of 0.6-0.9 sqm in high frequency and clean configuration compared to "Gen 4.5" being compared.

It's rather modest, but has to be weighed with the induction of Meteor AAM's. For Indonesia wise.. this KF-21 will provide us with opportunity in operating and maintaining fighters with reduced RCS or stealth one as well as finally giving our fighter pilot a taste of DACT with something with RCS below 1 sqm. For context our T-50 Combat trainer have RCS of about 2 sqm in X-band, with KF-21 which provide about 0.6 sqm in same band, clean. That hopefully will light some bulbs in our general's mind on low RCS threat.

Anyone interested with "playing" with the projectfiles can visit here :


it of course not for free but i can guarantee the funds will go to not only getting myself remain alive but also better computers and literatures.
 
Don't buy it, I know the French did quite a bit of work to get the RCS down from the original version, so for a bigger jet with 2 fins to have a lower RCS is quite questionable.

I mean the RAM i used for the Rafale is bit old as it coming from my earlier estimate.
 
With clean config? Yes obviously. But the lowest it can get with a combat load? Maybe with semi-conformal Meteors only, but there's no way this is achievable with underwing pylons, drop tanks and pods:
Conformal weapons are just as much RCS offenders as ones on pylons. They help aerodynamics, but such carriage still by default leaves long, big, elaborate sets of "corner reflectors".

Even purely geometrically it surprises me.
When su-35s was in development, they found that major source of enormous flanker RCS was access hatches and various small gaps.
Cleaning all of it(de facto redesigning outer skin and access layouts anew) was one of major items in its development.

Still, indeed surprising. Flanker was designed before RCS became significant design consideration, Rafale was designed after and with it in mind.
 
When su-35s was in development, they found that major source of enormous flanker RCS was access hatches and various small gaps.
Cleaning all of it(de facto redesigning outer skin and access layouts anew) was one of major items in its development.

Also inlet treatment, use of Bandpass radome, use of conductive canopy, so it's no longer dielectric. Things like that.
 
So, i'm also made estimates but speculative for KF-21 Block III. Some assumptions however :

-More extensive RAM paint treatment which now cover fuselage instead just wings, but RAS treatment remains the same (wing LE/TE and inlet)
-F-35'esque EOTS
-True "flatbottom" as Internal weapon bay take over.
-The production attempt to retain as many techniques, materials and procedures from Block I and II as possible, for smooth serial production and reduce needs to retrain workers and retooling of the factory.

Details can be viewed here :
Top of the airframe​
Bottom​
The "K-EOTS"​
CleanBlockIII.png CleanBottom.png KimchiEOTS.png

The Treatment

RAS (Radar Absorbent Structure)​
RAM (Radar Absorbent Material) paint​
KF-21Block-III.png RAM Treatment.png

same as my previous KF-21 estimates. Frequency is VHF down to Ku Band. Result wise tho, across all the frequencies.. the reduction is in average about 72%. I Would say great. Could be better with much more advanced absorber materials.

Speculative Block III.png

I wish i could expand upon my material library. But i guess that will be a very long term and uncertain endeavour.
 
The Boramae will go down in history as the only fifth generation fighter with a twin seat trainer variant. I wonder what will be next for the twin seat?
Drone wrangler.



So will it happen or not? That is the million dollar question.
The IWB version?

I expect it to happen. If we're lucky only 5 years after the Block II.
 


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