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

Umigami

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But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.

This. That's one of the weirdest aspects of the F-35 tri-service controversy... even when it is not there, the lift-fan (I mean, its empty space !) still impacts the aircraft negatively. A simple example: F-35 rear visibility is not as good as all the other bubble-canopy fighters.
And also, exactly what's in the quote - I'd never realized that before ! : no centerline weapons bay, once again because of the lift-fan empty space.
I remember reading stuff about the JSF-JAST-X35 - F-35 20-25 years ago "on the non VSTOL variants the lift fan will be replaced by a fuel tank" okay... not a bad idea, but there is still a price to pay, you see...
If you look closely, KF21's rear visibility isn't really good either.
Screenshot_20210129-013108_YouTube.jpg
It got blocked.

Screenshot_20210418-101405_Chrome.jpg
Martin baker Mk18 that Boramae use.
 

VTOLicious

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And my eyes are telling me the KF-21 its sleeker less bulbous airframe can probably best the 35 in some acceleration scenarios; at least when its carrying missiles internally. But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.
But it only looks like a finer fuselage because it doesn't carry as many / as large weapons internally as F-35 so its not a fair comparison. Centre fuselage packaging is a huge driver for these sorts of aircraft.
...And one should not forget that F-35 is single engine, including single duct. Due to twin engine / duct the layout of KF-21 is completely different from the outset.
 

rooster

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And my eyes are telling me the KF-21 its sleeker less bulbous airframe can probably best the 35 in some acceleration scenarios; at least when its carrying missiles internally. But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.
But it only looks like a finer fuselage because it doesn't carry as many / as large weapons internally as F-35 so its not a fair comparison. Centre fuselage packaging is a huge driver for these sorts of aircraft.
...And one should not forget that F-35 is single engine, including single duct. Due to twin engine / duct the layout of KF-21 is completely different from the outset.
Exactly. You made my point. It doesn't carry 4000 lbs of munitions in an overly fat fuselage. Its a fighter. Its sleek and probably will best the F-35 in some scenarios as a fighter. The 35 could have had a narrower waistline but the fusealge was taken up by a liftfan for only a few hundred stovl variants. Single engine or not they could have kept the aircraft leaner with a central weapons bay. The 35 is a fine aircraft but even a blind person can see its fat and because its fat its acceleration suffers at certain speeds, specifically supersonic acceleration where drag goes up faster than subsonic. The pentagon was wowed by f117 performance in gulf war 1 and wanted to replicate its payload plus carry aams plus carry a lift fan. The pentagon really did not need nearly 2000 fighters that could carry 4000 pounds of "bombs" plus a compliment of aams to self escort; I think 500 would have sufficed. For having the worlds most powerful engine, the 35 isn't exactly fast. Its the slowest frontline fighter the USA has produced since what the early 60s? And its 4 aim120 can't be fired in a turning fight. For that it has to use external winders that diminish its stealth. Time and use in combat will be the final judge. The Chinese and the Europeans and now the orient aren't copying the girth of the 35.
 

TomcatViP

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It's not the slowest. It's in fact the fastest with an operational load...
It can go also farther (see how Israel is planning having the capacity to strike deep inside Iran without air-refuelling).
 

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Define operational load... for A/A missions, that's just 4 internal AAMs on the F-35, with a possible upgrade path to 6 in the future. That kind of load out can be carried externally in low-drag configurations (wing tips, inlet tunnel, semi-conformal wells) by *many* legacy fighters. Typhoon, Rafale and Su-35 can possibly supercruise with such a payload!

OTOH, if you consider the A/G role, the F-35 will at least not be outperformed - I doubt any 4.5 gen fighter will supercruise carrying 2x 2000lb PGMs.

More generally, the large contribution to internal volume by the huge tank capacity of the F-35 should not be forgotten. It's cardinal dimensions (length, span) are roughly comparable to Typhoon, but the 8.3t fuel capacity alone will require more than 4m³ of additional volume over and above the penalty for the weapons bays! As with the F-22, the airframe packaging LM came up with is astonishingly efficient, but with the external dimensions constrained to such a degree, something has to give.
 
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Trident

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But it only looks like a finer fuselage because it doesn't carry as many / as large weapons internally as F-35 so its not a fair comparison. Centre fuselage packaging is a huge driver for these sorts of aircraft.

And quite probably not as much fuel, too. The fuel fraction on the non-STOVL F-35 variants is insane! I would be cautious about the <12t OEW claimed for the KF-21 - this seems very optimistic to me unless it has less than 6t maximum internal fuel.

...And one should not forget that F-35 is single engine, including single duct. Due to twin engine / duct the layout of KF-21 is completely different from the outset.

The single engine bay is probably the bigger difference, the F135 is quite a bit longer than the F414 and installed relatively far forward in the airframe due to STOVL CG considerations. With the F-35 having bifurcated intakes, the length of the combined duct section is therefore probably quite short, and the engine bay rather more impactful.
 

superpower42

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But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.

This. That's one of the weirdest aspects of the F-35 tri-service controversy... even when it is not there, the lift-fan (I mean, its empty space !) still impacts the aircraft negatively. A simple example: F-35 rear visibility is not as good as all the other bubble-canopy fighters.
And also, exactly what's in the quote - I'd never realized that before ! : no centerline weapons bay, once again because of the lift-fan empty space.
I remember reading stuff about the JSF-JAST-X35 - F-35 20-25 years ago "on the non VSTOL variants the lift fan will be replaced by a fuel tank" okay... not a bad idea, but there is still a price to pay, you see...
If you look closely, KF21's rear visibility isn't really good either.
View attachment 655864
It got blocked.

View attachment 655865
Martin baker Mk18 that Boramae use.
...And Martain baker reveal the test

Source: https://martin-baker.com/2021/04/28...in-baker-mk18-seat-unveilled-at-kai-showcase/
 

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GARGEAN

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It's not the slowest. It's in fact the fastest with an operational load...
It can go also farther (see how Israel is planning having the capacity to strike deep inside Iran without air-refuelling).
Any F-15 can go much faster with heavy load than 35 with none at all. And will get to that speed much faster. 16 is more humble but not lagging behind any feelingly. Now F/A-18 is indeed more sluggish, possibly ever without any load, but is this really a line to beat?..
 

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Trident

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If by enhanced engines you mean the -229 or equivalent GE engines, these are only available in the Strike Eagle airframe, which is considerably heavier (and the E-model CFTs weigh a bit more too, IIRC). For the fighter Eagles, there's not much in it between the -100 and -220(E) engine variants in terms of thrust.

So the F-15 is 0.15 of a Mach faster in comparable configuration - that is exactly my point! What I'm saying is that the F-35 is indeed outclassed (in terms of kinematics) in the A/A role, but perfectly competitive in A/G missions.
 
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TomcatViP

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@H_K : I doubt you'll fly 500Nm at Mach1.75 in your Eagle...
Most combat range with A2G loads are in the 450/550kt speed range. The cruise speed of a M2K low is around 440kt for example.
With internal carriage and clever aerodynamics, an F-35 can fly over 600kt in the same configuration which is undeniably faster. Being a VLO airframe, it can cruise also at high altitude where any other non-stealth platform are denied in any 21st century scenario. So the cruise profile will be flown at a more efficient altitude, increasing ground speed significantly (and range for any given time).

Comparing attack profiles, range and ground speed of a previous generation fighter with that of the F-35, is like comparing the time spent and profile of a cross country flight with a DC-3 and a 707.

You need to have the overall picture in mind when making such comparisons.

Yet, this has been extensively debated often...
 
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Umigami

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But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.

This. That's one of the weirdest aspects of the F-35 tri-service controversy... even when it is not there, the lift-fan (I mean, its empty space !) still impacts the aircraft negatively. A simple example: F-35 rear visibility is not as good as all the other bubble-canopy fighters.
And also, exactly what's in the quote - I'd never realized that before ! : no centerline weapons bay, once again because of the lift-fan empty space.
I remember reading stuff about the JSF-JAST-X35 - F-35 20-25 years ago "on the non VSTOL variants the lift fan will be replaced by a fuel tank" okay... not a bad idea, but there is still a price to pay, you see...
If you look closely, KF21's rear visibility isn't really good either.
View attachment 655864
It got blocked.

View attachment 655865
Martin baker Mk18 that Boramae use.
...And Martain baker reveal the test

Source: https://martin-baker.com/2021/04/28...in-baker-mk18-seat-unveilled-at-kai-showcase/
Does Boramae's canopy has explosive chord ?
 

H_K

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@TomcatViP You’re right. It was just an interesting factoid... not implying the F-15 is superior in A2G.

Now the real interesting datapoint would be to compare a twin-engine VLO aircraft with a somewhat similar planform to an F-15 vs. the F-35. Then we could see how much of a drag penalty the F-35’s “short fat” airframe has.

... and in some ways the F-21 isn’t too far off from that notional VLO F-15 (just a little skinnier).
 

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For the fighter Eagles, there's not much in it between the -100 and -220(E) engine variants in terms of thrust.

Not in terms of static, uninstalled thrust at sea level. Actually, the -220 has somewhat lower thrust rating.
But real life performance improved a lot between the -100 and the -220.
 

GARGEAN

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So the F-15 is 0.15 of a Mach faster in comparable configuration - that is exactly my point
Question is by far not only in top speed. If airframe needs more than minute to reach it - not much use of those numbers.
 

helmutkohl

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But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.

This. That's one of the weirdest aspects of the F-35 tri-service controversy... even when it is not there, the lift-fan (I mean, its empty space !) still impacts the aircraft negatively. A simple example: F-35 rear visibility is not as good as all the other bubble-canopy fighters.
And also, exactly what's in the quote - I'd never realized that before ! : no centerline weapons bay, once again because of the lift-fan empty space.
I remember reading stuff about the JSF-JAST-X35 - F-35 20-25 years ago "on the non VSTOL variants the lift fan will be replaced by a fuel tank" okay... not a bad idea, but there is still a price to pay, you see...
If you look closely, KF21's rear visibility isn't really good either.
View attachment 655864
It got blocked.


Martin baker Mk18 that Boramae use.
seems to be common with many 5th gen designs as of late

X-32 rear view isnt great
x32-25.jpg


nor the F-35. it has a slight bubble but most of it is covered by metal.
d2a22cj-038c8297-0ed0-4f35-8239-9eb609353bca.jpg
 

Trident

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Or the Su-57, for that matter.

Not in terms of static, uninstalled thrust at sea level. Actually, the -220 has somewhat lower thrust rating.
But real life performance improved a lot between the -100 and the -220.

I would describe the improvement as one of handling, rather than performance. The -100 was beset by compressor stall problems during throttle transients and in flight attitudes with distorted inlet flow (high AoA/sideslip, etc.), as well as unreliable afterburner light-off. As the thermodynamic cycle parameters did not change much, there is no reason to assume the changes in the -220 had much of an impact on steady-state thrust at any speed or altitude, so none of this should affect max Mach.
 

Trident

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Question is by far not only in top speed. If airframe needs more than minute to reach it - not much use of those numbers.

If the combined weight & drag of the CFTs and bombs is enough to take almost 0.8 Mach off the top speed of the F-15, its acceleration will be nowhere near as good as in clean config either. The F-35 at least does not suffer a drag penalty at all...

It's probably still not going to out-accelerate the best of its competitors, but in the A/G role the F-35 at least is no slouch.
 

robunos

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But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.

This. That's one of the weirdest aspects of the F-35 tri-service controversy... even when it is not there, the lift-fan (I mean, its empty space !) still impacts the aircraft negatively. A simple example: F-35 rear visibility is not as good as all the other bubble-canopy fighters.
And also, exactly what's in the quote - I'd never realized that before ! : no centerline weapons bay, once again because of the lift-fan empty space.
I remember reading stuff about the JSF-JAST-X35 - F-35 20-25 years ago "on the non VSTOL variants the lift fan will be replaced by a fuel tank" okay... not a bad idea, but there is still a price to pay, you see...
If you look closely, KF21's rear visibility isn't really good either.
View attachment 655864
It got blocked.


Martin baker Mk18 that Boramae use.
seems to be common with many 5th gen designs as of late

X-32 rear view isnt great
x32-25.jpg


nor the F-35. it has a slight bubble but most of it is covered by metal.
d2a22cj-038c8297-0ed0-4f35-8239-9eb609353bca.jpg

Does it matter when you have EODAS ?

cheers,
Robin.
 

stealthflanker

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So, yeah. For sake of curiousity. I added IRST and Meteor Missiles to my KF-21 model.

C-107WithWeapons.png

The goal was of course to "see" the "radar signature" of the design when carrying the missile in its respective semi-conformal mount. For this purpose i used 3 frequencies. L-band (1 GHz), S-band (3GHz) and X-band (8 GHz). The aspect being considered is frontal, This is when viewed from front horizontally. about -45 to 45 degrees while vertical is from the base of fuselage to canopy which is about 65 degrees down to 110 degrees. The assumptions are as follows :

1.Inlet RCS are not simulated yet, as i dont have idea yet on the layout of the S-duct. probably in the future i will include one. So the inlet are "shut" off with Perfect RAM.
2.PEC Material.
3.No RAM As i'm still have no idea of the specification of the Korean absorbers. To allow estimates i need to know at least the Impedance (ohm/meter) of the RAM or electrical parameters such as Permitivitty, Permeability and tangential loss of the materials

The output Data is in shape of contour as this one and a 2D contour plot. This one is in X-band, there is another in L-band.
X-band 3D plot (With Missiles)

X-band KFXconf.png
L-band (1 GHz)
L-bandPlotKFX.png


The 2D contour plot with Meteor Missiles.

L-band (Clean)

IRST2.png
The two main red lines at 45 and -45 degrees angle are contributions from the wing.

This one is with Meteor missile

WithMeteor2.png

Qualitatively speaking, there is noticeable increase in Radar signature at lower fuselage due to meteor missiles. Those smaller "blue" area is probably numerical errors (well my model isnt perfect)
This one is the result for the X-band
KFX-Conformal Weapons X-band.png
One can see the strong return caused by the Meteor Missiles under the fuselage which basically occupy half of the plot.

The thing that remains is of course how to present the data in the "practical" means e.g for say calculating radar detectability of the aircraft. The following is the raw data in excel format.

0point15.png

To "process" the data i use Median as apparently this merit is most used in literature.


Zoomed in Data.png

The result, as one can see there are 5 coloumns. The leftmost is for calibration purpose where i deliberately put Perfect RAM in the IRST balls to see if it would be considerably different to the one with PEC (Perfect Electric Conductor) material. Turns out the differences are relatively minimal. Therefore i proceeded to the L-band with Meteor missiles fitted which yielded the Median RCS of 0.14 sqm. I continued to S-band (3 GHz) But that one only in clean configuration, which shown the Median of 0.07 sqm it's lower but not much lower than L-band.

Later moved to X-band. This shown the one with meteor missiles. As seen the calculated median RCS is 0.15 sqm.

The model appears to have weak dependence on frequency, below is my earlier "study" where the configuration's RCS vs Frequency can be shown. It's fluctuative but only show weak dependence of RCS vs Frequency.
C107VHFtoX.jpg

Well now the question remains on whether this presentation is acceptable. There appears to be still no real standard on how RCS or radar signature data have to be presented. Feel free to drop advice on how i should process the real data or maybe some tips for better mesh.
 

helmutkohl

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But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.

This. That's one of the weirdest aspects of the F-35 tri-service controversy... even when it is not there, the lift-fan (I mean, its empty space !) still impacts the aircraft negatively. A simple example: F-35 rear visibility is not as good as all the other bubble-canopy fighters.
And also, exactly what's in the quote - I'd never realized that before ! : no centerline weapons bay, once again because of the lift-fan empty space.
I remember reading stuff about the JSF-JAST-X35 - F-35 20-25 years ago "on the non VSTOL variants the lift fan will be replaced by a fuel tank" okay... not a bad idea, but there is still a price to pay, you see...
If you look closely, KF21's rear visibility isn't really good either.
View attachment 655864
It got blocked.


Martin baker Mk18 that Boramae use.
seems to be common with many 5th gen designs as of late

X-32 rear view isnt great
x32-25.jpg


nor the F-35. it has a slight bubble but most of it is covered by metal.
d2a22cj-038c8297-0ed0-4f35-8239-9eb609353bca.jpg

Does it matter when you have EODAS ?

cheers,
Robin.
yeah i was thinking the same.. the abandonment of the full bubble canopy since the F-22 (ok J-2o might be an exception), and the forward centric canopies of all the new designs since then probably indicates that improvements in avionics, etc mean its not as important as before.
 

Trident

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The 2D contour plot with Meteor Missiles.
[...]
Well now the question remains on whether this presentation is acceptable. There appears to be still no real standard on how RCS or radar signature data have to be presented. Feel free to drop advice on how i should process the real data or maybe some tips for better mesh.

To me the 2D contour plot seems the most intuitive. You should make sure the contour range and levels are identical between them though, so comparing different plots does not require mental arithmetic.
 

F119Doctor

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Or the Su-57, for that matter.

Not in terms of static, uninstalled thrust at sea level. Actually, the -220 has somewhat lower thrust rating.
But real life performance improved a lot between the -100 and the -220.

I would describe the improvement as one of handling, rather than performance. The -100 was beset by compressor stall problems during throttle transients and in flight attitudes with distorted inlet flow (high AoA/sideslip, etc.), as well as unreliable afterburner light-off. As the thermodynamic cycle parameters did not change much, there is no reason to assume the changes in the -220 had much of an impact on steady-state thrust at any speed or altitude, so none of this should affect max Mach.
The -220 had significantly improved in-flight performance over the -100, primarily due to improved control system scheduling with the full authority DEEC control system. The core module also had improved turbine material & design that lasted longer and suffered much less performance deterioration over time than the -100. The -220 started off at 102% of rated thrust when new and would maintain it for the whole 4000 cycle overhaul interval.
 

Trident

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The -220 had significantly improved in-flight performance over the -100, primarily due to improved control system scheduling with the full authority DEEC control system. The core module also had improved turbine material & design that lasted longer and suffered much less performance deterioration over time than the -100. The -220 started off at 102% of rated thrust when new and would maintain it for the whole 4000 cycle overhaul interval.

From the pilot's perspective, the greatly improved throttle response would no doubt be characterized as superior performance, but did any of this really expand the steady-state speed envelope? For example, I'm pretty sure SAC aircraft performance data makes no allowance for deterioration due to aging.

The -220 upgrade might well have improved acceleration times, but if we look closely enough for the engine spool-up contribution to matter, the F-35/F135 is likely to come off even better in a comparison.
 

F119Doctor

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The -220 had significantly improved in-flight performance over the -100, primarily due to improved control system scheduling with the full authority DEEC control system. The core module also had improved turbine material & design that lasted longer and suffered much less performance deterioration over time than the -100. The -220 started off at 102% of rated thrust when new and would maintain it for the whole 4000 cycle overhaul interval.

From the pilot's perspective, the greatly improved throttle response would no doubt be characterized as superior performance, but did any of this really expand the steady-state speed envelope? For example, I'm pretty sure SAC aircraft performance data makes no allowance for deterioration due to aging.

The -220 upgrade might well have improved acceleration times, but if we look closely enough for the engine spool-up contribution to matter, the F-35/F135 is likely to come off even better in a comparison.
Not just spool up times, although the -220 and -229 could start lighting the AB while the main engine was spooling up to Mil, which might have saved 4 seconds on a Idle to Max AB transient. While the increased performance of the -220 may not have expanded the total 1G envelope, aircraft acceleration was noticeably improved in the middle of the envelope. When the USAF was testing the ASAT missile at Edwards AFB, the -100 powered F-15 had difficulty reaching the high altitude speed / climb angle launch parameters consistently. When-220 engines were installed on the test aircraft, no problem consistently hitting the launch parameters. We’re not talking huge improvements, probably 5-10% better in parts of the envelope.
 

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But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.

This. That's one of the weirdest aspects of the F-35 tri-service controversy... even when it is not there, the lift-fan (I mean, its empty space !) still impacts the aircraft negatively. A simple example: F-35 rear visibility is not as good as all the other bubble-canopy fighters.
And also, exactly what's in the quote - I'd never realized that before ! : no centerline weapons bay, once again because of the lift-fan empty space.
I remember reading stuff about the JSF-JAST-X35 - F-35 20-25 years ago "on the non VSTOL variants the lift fan will be replaced by a fuel tank" okay... not a bad idea, but there is still a price to pay, you see...
If you look closely, KF21's rear visibility isn't really good either.
View attachment 655864
It got blocked.


Martin baker Mk18 that Boramae use.
seems to be common with many 5th gen designs as of late

X-32 rear view isnt great
x32-25.jpg


nor the F-35. it has a slight bubble but most of it is covered by metal.
d2a22cj-038c8297-0ed0-4f35-8239-9eb609353bca.jpg

Does it matter when you have EODAS ?

cheers,
Robin.
yeah i was thinking the same.. the abandonment of the full bubble canopy since the F-22 (ok J-2o might be an exception), and the forward centric canopies of all the new designs since then probably indicates that improvements in avionics, etc mean its not as important as before.
This Boeing NGAD concept has a tiny window, probably only adequate for TO and landing. I suspect that it's to minimize the risk of the pilot being blinded by lasers. Beyond that its almost certain to depend on synthetic vision.

British Aerospace's P.125 concept had none at all.


 

stealthflanker

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To me the 2D contour plot seems the most intuitive. You should make sure the contour range and levels are identical between them though, so comparing different plots does not require mental arithmetic.
Thanks, Yeah. I'll equalize them in the future iterations.
 

helmutkohl

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But Thats what you get when you have a centerline weapons bay because you didn't need to keep room for a lift fan.

This. That's one of the weirdest aspects of the F-35 tri-service controversy... even when it is not there, the lift-fan (I mean, its empty space !) still impacts the aircraft negatively. A simple example: F-35 rear visibility is not as good as all the other bubble-canopy fighters.
And also, exactly what's in the quote - I'd never realized that before ! : no centerline weapons bay, once again because of the lift-fan empty space.
I remember reading stuff about the JSF-JAST-X35 - F-35 20-25 years ago "on the non VSTOL variants the lift fan will be replaced by a fuel tank" okay... not a bad idea, but there is still a price to pay, you see...
If you look closely, KF21's rear visibility isn't really good either.
View attachment 655864
It got blocked.


Martin baker Mk18 that Boramae use.
seems to be common with many 5th gen designs as of late

X-32 rear view isnt great
x32-25.jpg


nor the F-35. it has a slight bubble but most of it is covered by metal.
d2a22cj-038c8297-0ed0-4f35-8239-9eb609353bca.jpg

Does it matter when you have EODAS ?

cheers,
Robin.
yeah i was thinking the same.. the abandonment of the full bubble canopy since the F-22 (ok J-2o might be an exception), and the forward centric canopies of all the new designs since then probably indicates that improvements in avionics, etc mean its not as important as before.
This Boeing NGAD concept has a tiny window, probably only adequate for TO and landing. I suspect that it's to minimize the risk of the pilot being blinded by lasers. Beyond that its almost certain to depend on synthetic vision.

British Aerospace's P.125 concept had none at all.



its becoming like Ace Combat 3. all cockpits are fared over with metal
-Nh_LT8fyftmWyAhEYoMtuaNhomQqfQl42FIuFi3URfUcmo2NSkIVyc9nr-LQ-mcV3YFXXRFWeYkF8k2r-yNwlGsuF2CL6ymq777AGY8Al2mXiZ_
 

LMFS

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As with the F-22, the airframe packaging LM came up with is astonishingly efficient,
I am being admittedly picky here, but if sacrificing supersonic performance is the price, then is not so astonishing. They got some min cross section values given by the bays in parallel with the engines and (wisely) filled the internal volume created with fuel, since the drag penalty could not be avoided. This is a compromise no other fighter indulges in, so it is not really fair to compare. I agree with the rest of your rationale
 

Trident

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That depends entirely on the specification LM designed it to satisfy, and how well said spec reflects real-world needs. From LM's point of view, it was very successful in faithfully executing the extremely difficult and often contradictory requirements it was given, achieving the maximum speed demanded though falling short somewhat on acceleration. So the specification allowed for this compromise in performance on LM's part and you can't hold that against it - whether it's a sensible solution to actual combat operations is another matter. Jack of all trades, master of none applies - the F-35 by design is an answer to a great many tasks, and claimed by marketing to solve even more. It can't possibly be all these things at once, but that doesn't mean it isn't an impressive feat of engineering just for achieving what it does.
 
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stealthflanker

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So, yeah. i think i get a bit of "systematic" here. Finally.

Now i got both Armed and unarmed version "looked" in the X-band (8 GHz). The polarization is Horizontal, while the "look angle" is basically what i consider the Frontal aspect (-45 deg to 45 deg Horizotal with 65-110 Deg vertical) The materials are still PEC but the Inlet are shut off due to reason mentioned some messages above. No RAM is assumed yet.

The Armed versionThe Unarmed version
c-107withweapons-png.656172
NoWeapons.png
Their respective 3D view
x-band-kfxconf-png.656173
KFX-Clean2.png
The 2D projection of the above
kfx-conformal-weapons-x-band-png.656177
No armament KFX X-band.png


The differences are very evident between the conformal storage vs flying clean. The 2D projection plot has been "equalized" So the colors are comparable. Unfortunately the ANSYS just not allow me to use same color conversion. So only the max and minimum value are the same.

"Statistically" however in terms of Median. it doesnt seem to look much. probably because i take all the value into the Median.

KF-21 Table.png

The frequencies are as follows :
VHF is 0.15 GHz or 150 MHz, used by things like P-18, P-14 and probably Nebo UE
L-band is 1 GHz used by Long range air defense Radar like say the Seek Iglo
S-band is 3 GHz used by things like typical air defense radar and AEW
X-band is 8 GHz to represent fighter or SAM Radar's.

I would love to use more representative 9500-11000 MHz but the Simulation just take forever, the X-band took about 8 Hours. i started from 1.15 AM and finished at about 9.49 AM. and i'm but one man with only one PC. Conversion is possible tho through use of simple rule of thumb of wavelength dependence of RCS.

Anyway... What to do after estimating the RCS value ? Well naturally for me and hopefully Indonesian in general. This offers at very least a leap in terms of learning as KF-21 again.. would offer a low signature target, giving a new challenge to our fighter pilots who at best handling 1 Sqm target (T-50 Golden eagle) Now they will have more representative 12 dB lower regional challenge in terms of RCS. Might not be as low as what potentially FC-31 or other LO targets but still.
 

TomcatViP

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I see some impressive results while no ram has yet been applied.
To save some computational time, have you tried to apply symmetry?
 

stealthflanker

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I see some impressive results while no ram has yet been applied.
To save some computational time, have you tried to apply symmetry?

Yeah was promising indeed. I would say the Korean is trying to get the basic shape first for future development.

On computational time wise.. well i have some options :
-Use lower frequency (L-band is faster)
-Reduce the data point (e.g from every 1 degrees to 3 degrees or 10) Tho i need to pay attention to resolution.
-Narrowing the simulation angle (e.g from 45 deg to 20 deg)

I would love to use symmetry, that's what i did before. It's just that when IRST is added it's not really possible.
------

Anyway... Just found this. Korean RCS range


The outdoor range
Outdoor range.png

Seems similar to Russian range at Tver albeit this one seems to have better pavement.
 

Frogfigther

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There appears to be still no real standard on how RCS or radar signature data have to be presented. Feel free to drop advice on how i should process the real data or maybe some tips for better mesh.
2018110212254617948.jpg
In respect of the mesh, I think it is better to add Boundary Layer Diverter and its bleed systems and to delete gloves on main wing because it will make your model much similar to real KF-21. They might make some RCS changes I guess.
 

helmutkohl

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recent article talking about the integration of various air to ground missiles on both the FA-50 and KF-21. basically the Taurus series and LIG
its interesting to note how many European missiles the KF-21 is planned to operate. its basically a Eurofighter but Korean
it says it would take 2 years to integrate or something like that


2021051412005336118.jpg

2021051411202165138.jpg
 

Maro.Kyo

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There appears to be still no real standard on how RCS or radar signature data have to be presented. Feel free to drop advice on how i should process the real data or maybe some tips for better mesh.
View attachment 656596
In respect of the mesh, I think it is better to add Boundary Layer Diverter and its bleed systems and to delete gloves on main wing because it will make your model much similar to real KF-21. They might make some RCS changes I guess.
Definitely will affect the frontal aspect RCS figures. F-22 for instance has a stealthy mesh-like installation where the upper part of the BL duct exit is, covering it off while still allowing the airflow.
 
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