KAI KF-21 Boramae (KFX Korean Indigenous Fighter program)

Scott Kenny said:
I don't think it's that challenging. The F414 burns 0.84lb/hr/lbf, so you're only talking ~5% fuel burn improvement. There's been quite an improvement in turbine engines since the F414 was designed. For example, the CFM56-2 (737 classic) burns 0.386-0.396lb/hr/lbf while the -7B (737NG burns 0.356-0.386lb/hr/lbf at takeoff. That's a ~10% improvement at the low range.
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It is very challenging. The fuel burn improvement of the 737 example is directly linked to the bypass ratio increase. Commercial jets increase bypass ratio by fitting a bigger fan. On a fighter jet if you increase bypass ratio but keep the diameter the same then the thrust reduces. To improve both thrust and fuel efficiency is then extremely challenging.

The older F404 actually has around 3% better fuel burn than the F414 as it has a higher bypass ratio of 0.34 versus 0.25.

The RB199 actually has 15% better fuel burn than the F414 in a similar size engine. But the RB199 has 30% less dry thrust due to its higher bypass ratio 1.1

If you keep bypass ratio constant there has only been a 5% fuel burn improvement over the last 30 years. The F414 actually has great fuel efficiency for an engine with such a low bypass ratio.

It would be nearly impossible for Korea to improve fuel burn by 5% AND increase thrust beyond the current F414. If they do manage to achieve this then the engine will probably be running so hot that the aircraft needs a new engine every month. Massively trading durability to achieve higher performance like what the USSR did for decades.
 
insidersource said:
It is very challenging. The fuel burn improvement of the 737 example is directly linked to the bypass ratio increase. Commercial jets increase bypass ratio by fitting a bigger fan. On a fighter jet if you increase bypass ratio but keep the diameter the same then the thrust reduces. To improve both thrust and fuel efficiency is then extremely challenging.
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The two engines I compared have almost identical fan diameters.


insidersource said:
It would be nearly impossible for Korea to improve fuel burn by 5% AND increase thrust beyond the current F414. If they do manage to achieve this then the engine will probably be running so hot that the aircraft needs a new engine every month. Massively trading durability to achieve higher performance like what the USSR did for decades.
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I don't think it's that dire, cooling tech has also gotten a lot better.

But even if they need to overhaul the engines every 500 hours (roughly annually, and that's about as often as J58s needed overhaul!), that's tolerable. For that matter, F110s need to be overhauled about every 750 hours. F119s and F414s use a cycle-count to determine TBO, and that doesn't neatly map to hours.
For example: a ferry flight where they start the engine, run it up to TOGA power, throttle down to cruise power, then land and shut down is 1 cycle, even if it's a 10 hour flight across the Pacific. But a 1 hour BFM training flight might count as 25 or even 50 cycles, depending on how much the pilot rows the throttle in maneuvers.​
 
Scott Kenny said:
The two engines I compared have almost identical fan diameters.
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But it's still bigger. 1inch bigger fan. But let's say it's identical for arguments sake.

There is 15 years between the first flight of the 737 classic and 737NG. Only ~3% improvement in fuel burn.

40 years later the latest CFM-56-7B is a ~8% improvement. It is pretty unrealistic to think Korea can achieve a 5% fuel burn improvement and increase thrust in the same size/weight.

Scott Kenny said:
I don't think it's that dire, cooling tech has also gotten a lot better.
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Korean cooling tech?

Scott Kenny said:
But even if they need to overhaul the engines every 500 hours (roughly annually, and that's about as often as J58s needed overhaul!), that's tolerable.
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Not for an export KF-21. The KF-21 was meant to be cheaper than the F-35. Overhauling two engines far more often will put up the operating cost.
 
NMaude said:
Don't the Block 1 and 2 aircraft have IWBs but they're non-functional?
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yeah the space is there, you can see it in earlier posts in this thread.
its covered by the panel for the semi recessed missiles.
I don't know if it's confirmed, but supposedly that space is being used to hold something else with the current models
 
helmutkohl said:
I don't know if it's confirmed, but supposedly that space is being used to hold something else with the current models
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Will at least be the ammunition box for the gun which is quite obvious in the pictures, and the weapon ejectors and control units for the semi-conformal weapons.

The assembly pictures are pre systems install so there may be all sorts of cabling, pipes, hydraulic accumulators etc. in there as it's a good location for accessibility.
 
Ainen said:
But KF-21, IWB or no IWB, is a chubbier M=1.6, F414 design. IWBs don't come free in the first place - as they (obviously) push you to have airframe around the iwb volume. I.e. you're paying with drag penalty for that in almost any imaginable case.
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The KF-21 has hit Mach 1.81 with fixed air intakes. Both the Rafale and Super Hornet also have fixed intakes they also have a top speed of Mach 1.8. With fixed intakes they start to become a restriction at higher speeds above say Mach 1.5.

The Rafale has a top speed of Mach 1.8 yet can supercruise at Mach 1.4. These numbers are close together.

The Eurofighter has variable intakes which is the main reason it can go Mach 2+. Same as the F-15. The variable intakes reduce that restriction at high speed. The top speed isn't always a good indicator of supercruise speed. Plenty of Mach 2+ fighters can't supercruise at all.

I would estimate the KF-21 could supercruise between Mach 1.3 and Mach 1.4 with uprated F414 or EJ230 engines.
 
insidersource said:
The Rafale has a top speed of Mach 1.8 yet can supercruise at Mach 1.4. These numbers are close together.
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From that I understand(I don't really, it took a whole to read through cloudy sentences and I gave up midrace), Rafale supercruise at M=1.4 with 6 missiles and 1 tank was anticipated capability with M88-3 engines. Which, much like EJ230, don't exist. And since they don't exist, who knows what else could've changed.

Somehow it got transfered over into "already can", and Dassault just keeps this notion around without elaboration.
Rafale as is (88-2) can barely cross mach barrier and sustain M=1.2 clean(i.e. two wingtip MICAs). This is a type of "supercruise"most modern fighters sort of can.

In any case, Rafale is a significantly smaller, slimmer aircraft without IWBs, one that is actually built for supersonic performance（and always understood to be somewhat let down by available engine). Its aerodynamics are probably outright better.

As of now, though, beyond f-22 only eurofighter does operationally meaningful supercruise. And both raptor and eurofighter were built as supercruisers - for the latter it's its defining trait.
insidersource said:
I would estimate the KF-21 could supercruise between Mach 1.3 and Mach 1.4 with uprated F414 or EJ230 engines.
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To me it sounds not too dissimilar from eyeballing RCS.

KF-21 was never advertised as a supercruiser， i.e. it wasn't built for it, and original engines(F414) support this strongly.
Changing engines to supercruising ones - a choice that Korea could've made, but didn't - won't change rest of the plane.

I.e. it's very much unlike J-20 and Su-57, which are built as supercruisers, but are held back by their current engines.
 
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Ainen said:
To me it sounds not too dissimilar from eyeballing RCS.

KF-21 was never advertised as a supercruiser， i.e. it wasn't built for it, and original engines(F414) support this strongly.
Changing engines to supercruising ones - a choice that Korea could've made, but didn't - won't change rest of the plane.
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I'm not the one making incorrect conclusions.

You've just claimed clearly that the F414 is not supercruise capable. I am certain you have based this entirely from the fact the F414 engines are used on the Super Hornet. The Super Hornet just happens to be one of the slowest 4th gen fighters in the world.

The Super Hornet is slow because it has a 20% lower thrust to weight ratio, canted pylons and a very draggy wing designed for slow carrier approach speeds. It has nothing to do with the F414 engine.

The F414 was selected in the Lockheed X-59 where the supercruise speed is listed at Mach 1.42. The F414 has an extremely low bypass ratio. The F414 is 100% supercruise capable.

I believe the F119doctor once said on F-16.net that the F414 is as good as the EJ200 at supercruise.

Ainen said:
In any case, Rafale is a significantly smaller, slimmer aircraft without IWBs, one that is actually built for supersonic performance（and always understood to be somewhat let down by available engine). Its aerodynamics are probably outright better.
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So the KF-21 isn't built for supersonic performance?

Korean aerodynamics are outright inferior?

Wild claims you are making.
 
insidersource said:
So the KF-21 isn't built for supersonic performance?

Korean aerodynamics are outright inferior?

Wild claims you are making.
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If you're treating different - more useful, - optimization point as a national insult, what can I say. Chill? That has nothing to do with Korea or Korean engineers.
Just a fatter airframe, carrying IWB space, and designed from outset to carry outsized external payloads far enough in strike role.
Eurofighter doesn't compromise for the latter - one of major reasons it's a commercial failure, by the way.
insidersource said:
You've just claimed clearly that the F414 is not supercruise capable. I am certain you have based this entirely from the fact the F414 engines are used on the Super Hornet. The Super Hornet just happens to be one of the slowest 4th gen fighters in the world.
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F414 was born out of F412, I.e. F404 development for a subsonic long range strike aircraft. Which was then adapted specifically for F/A-18E/F. It isn't a poor unlucky engine put into a bad-bad airframe. It's a couple.
Super hornet didn't happen to be slowest 4th gen jet, it was designed to be like this, because experience shown it to be most optimal. And it is, in fact, optimal.
Which is why almost half of entire 5th generation are more or less further evolution of hornet/superhornet concept, using its engines. As it achieved actual ideal multirole balance.

I don't know anything abt X-59 to somehow comment.
 
Ainen said:
F414 was born out of F412, I.e. F404 development for a subsonic long range strike aircraft. Which was then adapted specifically for F/A-18E/F. It isn't a poor unlucky engine put into a bad-bad airframe.
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The F412 is completely different to the F414.

The F412 had a higher bypass ratio around 1:1 with a two stage low pressure turbine. It was completely optimised for subsonic cruise. The drawing shown below appears to show a bypass ratio similar or slightly larger than the F110 series which has a 0:87:1.

The F414 was not optimised for subsonic speeds at all. Its primary design goal was to get as much thrust as possible in the same footprint as the F404. The Super Hornet can then use the same engine bay as the classic hornet. This resulted in a very low 0.25:1 bypass ratio. No blades are shared with the F412.

You have made yet another false conclusion. That the A-12 was subsonic and the F412 was subsonic optimised that means the F414 must not be optimised for supercruise.

images - 2025-10-01T225827.964.jpeg
 
insidersource said:
The F412 is completely different to the F414.
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It is. Which doesn't change the fact that F414 is a compact evolution of thereof.
insidersource said:
The F414 was not optimised for subsonic speeds at all. Its primary design goal was to get as much thrust as possible in the same footprint as the F404. The Super Hornet can then use the same engine bay as the classic hornet.
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Yes, and as such, it was most clearly optimized for a mach 3 supercruising. Ideal for superhornet, as there's really just one parameter defining engine (bypass).
As such, clearly neither GE nor MD had any semblance of idea what they were doing.
As protective as you are of korean aerodynamics, your opinion of Americans doesn't appear to be high.
 
Lieutenant Colonel PNB Mohammad Sugiyanto, a TNI AU test pilot with the callsign "Mammoth," successfully conducted the maiden flight test from the front seat of the KF-21 Boramae prototype on September 30, 2025, in Sacheon, South Korea. In the one-hour mission alongside KAI test pilot Koh Hwi Seok, he evaluated performance as well as Stability & Control aspects at altitudes of 10,000–20,000 feet.

Previously, in May 2023, Sugiyanto became the first foreign pilot to fly in the rear seat of the KF-21, and his success in the front seat now underscores Indonesia's active contribution to this program.
 

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ComradeVortex said:
.Previously, in May 2023, Sugiyanto became the first foreign pilot to fly in the rear seat of the KF-21, and his success in the front seat now underscores Indonesia's active contribution to this program.
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Indonesia's active contribution to the program is rather contrary to their inability to pay their fair and contractually agrees share for many years...
 
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Amazing flying qualities. Surgical pilot skill. Notice also the acceleration demonstrated in turns and the split rudder aerobraking (not in effect a split rudder but use opposite deflection to the same effect).
 
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View: https://youtu.be/csqWLEMCIYw?si=G6xtPlDmIpV84FGO

Minute 1:26

"우리와의 방산 협력을 감안하면 인도네시아의 행보가 다소 불편하다고 지적했습니다"

"Considering our defense cooperation, it was pointed out that Indonesia's actions are somewhat uncomfortable."

They are uncomfortable with a MoU of Cooperation that Indonesia has made with North Korea, even though we have good cooperation with South Korea.
 
helmutkohl said:
stuff that happened this week as Indonesia tries to connect North Korea with ASEAN, although based on statements, Indonesia sees itself as a possible mediator between the north and south
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Here's the thing, Indonesia is as a matter of fact non-aligned and active, which is why it establishes many cooperations with many countries.
However, for many parties, it still stand in a gray zone of uncertainty.
The visit to North Korea by the Ministry of Foreign Affairs and the signing of the MOU will certainly become a negative sentiment in South Korea. Regardless of the relationship between the two countries, closeness to a party considered an "enemy" will create a skeptical attitude that affects the level of trust between South Korea and Indonesia.
 
synetic said:
View attachment 788807
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The numbering says 11 hardpoints, 10 for weapons. No wingtip rails, despite how the lines on the poster lay out.

The head-on of the EO targeting pod looks like Sniper, and weight checks out. I'm just surprised that there isn't a built-in EOTS.

Also, a pure air-to-air loadout suggests that stations 3 and 8 would be free for fuel tanks. 6x Meteors/BVRAAMs and 2x WVRAAMs.
 
Well, they ordered KF-16 replacement, they're getting just that. Same capability, but better and much more sovereign.

Cynically speaking, though, there's arguably just one outstanding quality in current configuration, namely ability to take off with 4 KEPD-350 (big progress over rather wasteful f-15k:Taurus pylon combo).
Won't fly far, not like Korea really needs to for their core missions; for others, F-15k is still not going anywhere.

Other than that, in it's current form, KF-21 is dangerously close to being more or less similar capability baseline to Gripen E (and arguably way less capability NET), on twice the plane.

This is a hefty price for future development path, which is now mostly only good for bigger ammo drum(i.e. wasted weight).
Scott Kenny said:
The head-on of the EO targeting pod looks like Sniper, and weight checks out. I'm just surprised that there isn't a built-in EOTS.
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Will appear on KF-21EX. Now it's probably one step/risk/development too far, especially since it doesn't really change anything, and shoulder position offers better angles.
 
Geo said:
I can't help it, but the Boramae is simply gorgeous and in the EX version with IWB and ideally Korean engines it will be just perfect.
A balanced machine that, conceptually speaking, will cover the needs of most air forces in the world for many decades to come.
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Agreed. The KF-21EX is going to dominate the market among those nations not buying F-35s.
 

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