Obviously I'm basing that on missions currently envisioned for KF-21s. What a future fighter, be it a block 3 or KF-XX, would fulfill is still an unkown for us and we could only speculate. And as a purely DCA fighter just like KF-16s, once more, that fuel capacity isn't ths biggest deal breaker. With stand off I've implied the extensive usages of long range ALCMs like Chunryong. There's not a single stealth fighter tha could load a misille of that size internally as of now, not even F-35. F-35s will carry JASSM and LRASMs externally for instance.
Also, avionics IS a concern due to the fact that it would require an extensive (re)certification process to work out the EMI problems and make it EMC conforming.
I'll stop here since I'm getting way off topic.
Not sure how obvious it was since you replied to this specific quote
KF-21 won't be a 5th gen fighter jet anyway as the aircraft could hold only 12,000lb (about 5,500kg) of fuel internally. This will severely restrict its combat radius. By contrast, F-35 is designed to carry 18,250lb (about 8,278kg) even though it is a single-engine fighter jet. This is why there is an early talk of moving to KF-XX in Korea.
Clearly I was talking about hypothetical KF-21 Block III, the 5th gen fighter aircraft and I plainly explained my reservation as KF-21's seemingly lack of internal fuel in contrast to F-35 will limit KF-21 Block III's role as a stealth multirole combat aircraft and that's why ROKAF is already considering a new platform, KF-XX.
If you were not interested in discussing the potential upgrade of KF-21 as a LO~VLO aircraft then I don't understand why you even bothered commenting on internal fuel as you and I both understand that non-stealth KF-21 will carry drop tanks & long-range missiles externally for those missions anyway.
I strongly implied the improvements that are required to evolve KF-21 into a true 5th gen fighter aircraft may need various structural changes and may be nearly impossible or too impractical for KAI/ROKAF to undertake. Meanwhile, avionics are also challenging, but they are doable and I doubt you'd disagree with this.
However, you claimed
There are bigger problems on the avionics side
That baffled me as things such as structural limitation are equally if not more challenging than implementing advanced avionics to turn KF-21 into a true 5th gen fighter.
However, I believe It was all due to a simple misunderstanding. I was talking about turning KF-21 into a 5th gen stealth combat aircraft. You were talking about maximising KF-21's capability as a 4.5 multirole combat aircraft.
Edit : I will stop here too as It is indeed getting irrevelant to the thread's topic.
