milosh wrote:MiG-31 had gun only to be able to down recon balloons, that was requirement.
Beef up airframe compared to MiG-31 is more for supersonic turns then for subsonic. Dogfight wasn't reason for that.
MiG-31 role isn't just interceptor it is AEW too, Soviets expect AWACS not to last long in case of WW3 they wanted MiG-25 to modify in AEW (big side mounted PESA arrays) but tech wasn't there so they developed advanced networking (for that era) for new interceptor which in combination with big PESA radar allow formation of MiG-31s to act as AWACS but much closer to front.
This is where better agility came in play, MiG-31s formation can turn faster and so better searching of airspace.
JH-XX, if it's ever built, will likely end up doing something similar, since the J-20 is designed for speed regimes similar to the F-22, and a subsonic AEW&C / stealth bomber simply can't keep up for that mission. At 30 meters long, you're looking at a pretty impressive radar aperture or EODAS pod if such a thing is used.
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Biggest problem with the MiG-31 seems to be its 5G limit; the Panavia Tornado is at 7.5G limit (at what flight regimes?) and even the F-111 has a 7.33G limit.
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Re: the F-18 shootdown, the USAF / USN had terms of engagement that prevented them from properly tracking and intercepting the MiG-25, and the MiG-25 scored a BVR kill.