Beautiful analysis of sustained turn rate of Mig21 against USAF F15s on international military forum.. i was trying to find our depletion of energy (speed) with increases Gs (turns) on delta wing fighters and stumbled on an interesting read...
Fighter performance; actual plane analysis
OK, this is really weird. I know that guy Adriann, who posted in the link you provided. He posted the exact same thing on WAB (world affairs board) of which I am a member, and we generated 6+ pages of discussion, where I think I dished his argument a bit.
Discussion on WAB
I think Adriann (a thoughtful and apparently nice guy) wrote a paper perhaps for his government, advocating upgrading older MiG-21 rather than acquiring a new airframe.
There are some advantages and disadvantages to the pure, tail-less delta planform of jets like the Mirage, the F-106. The MiG-21, while having a tail, has a nearly pure delta wing, and exhibits these properties.
Advantages - lower parasite drag, superior acceleration
, excellent instantaneous turn rates.
Disadvantages - Not as effective sustaining energy. Bleeds energy at high rates due to higher induced drag. Induced drag (as opposed to parasite drag) is the
drag generated by lift, meaning as you demand more lift from an airframe (high-G turning), the delta wing is not as effective as other wingforms.
All this means is that the delta wing can create an initial turn that is eye-watering, but the turn rate falls off rapidly as energy is depleted. Adriann's position (and there is some truth to it) is that high instantaneous turn, combined with point & shoot off-boresight IR missiles, is a potent combination.
But more modern airframes with specialized flight controls, canards, and/or thrust vectoring, can have the best of both worlds - a high instantaneous turn rate,
and an ability to sustain energy when neeed.
Again, the Mirage series are excellent, but I think there are better out there.