Two books below describe an actual engagement between the F-4J and MiG-21 over North Vietnam in 1972.

The F-4J locked up on one of four MiG-21s at 25 nautical miles, but lost lock soon. Then at 15 nautical miles it reacquired the target.

But note that at 25 and 15 nautical miles the F-4J had no positive ID of the approaching aircraft, so no BVR shot.

Scream of Eagles: The Dramatic Account of the U.S. Navy’s Top Gun Fighter – Page 311

When advised of the MiGs, Pettigrew thought of dropping their wingboard fuel tanks, but decided to wait until one of them had spotted the bandits. They nosed down and gunned north at 500 knots. Almost immediately, Hughes’ RIO, LTJG Joe Cruz, got a lock on one of the MiGs. It was an unsual lock given their radars: velocity only, a tough one to hold. Since McCabe, Pettigrew’s RIO, didn’t have one, Pettigrew gave the lead to Hughes, becoming – as he’d taught so often at Top Gun – Hughes’ wingman. The bandits were about 25 miles away, closing swiftly. Suddenly, Cruz lost lock.

US Navy F-4 Phantom II MiG killers: 1972-73 – Page 21

He locked-up the return and called a 900-knot closing velocity before the radar broke lock when the MiG went to beam. At about 15 nautical miles Lt Hughes reacquired the contact and secured another radar lock-up. Pettigrew immediately called his wingman. ‘I’ll go shooter. You’ve got the VID (visual identification)’,

will the plane have internal bay or not ?

It may, or it may not. We don’t know yet.

That scenario I think will always be a scenario. Since realistically I don’t think South Korea will ever faced a nuclear power alone. Off course unless if that nuclear power is North Korea.

And if ROK will have to face DPRK alone (say China and US will stay out from any armed conflict in peninsula and let the two Korea’s faced each other alone), than whatever DPRK has can be match easily with KF-X or even with existing F-16 or even the aging F-5 and F-4.

Besides if the situation happen, with nuclear technology that ROK has right now, ROK will have no much trouble to become nuclear power it self in short time right ?

In short, if KF-X can come out as something as stealthier twin engine FA-50 which in theory can surpass current F-16 block 50, Flankers or PRC J-10B, it will be in trouble only if facing USAF with both F-35 and F-22.

I just point out unless your scenario put USAF or USN as potential adversary for ROKAF, then KF-X seems will be enough for ROK need. After all again ROKAF seems not plan to make KF-X their most advance fighters in the future. Just the most numerous one right ?

A PTDI director I met told me he prefers single-engine designs. Don’t know whether it’s his personal opinion or the company’s official one.

To be numerous enough, lift-cycle costs should be as low as possible, and generally single-engine fighters are cheaper than twin-engine ones (the twin J85-powered F-5 is a rare exception).

That’s what I heard from DI team in here after they being briefed by KAI team. I will not be surprised if KF-X final design will be some kind more stealthy twin engined FA-50.

And nothing wrong with that, since it will be sophisticated enough from 2020 + environment.

If an affordable and stealthier FA-50 or whatever derivative is good enough against future threats from the 2020’s to 2040’s, I would heartily endorse the program.

Would it really be good enough? That’s a ten billion dollar question.