Limitations in upgrading a 4th Gen fighter with 5th Gen features

[FuturePAF]

This engineer seems to bring up good points. Basic conclusion I draw from his video is the F-16 Block 60/70/ F-21 is basically the end of what can be put into the F-16 Airframe. Hence why the USAF is considering a new clean sheet design for a 4++ Gen Fighter

 

[Dalit]

4th gen airframes were designed with a different philosophy in mind and this is where the limitations start in my opinion. Certain 5th gen electronics and sensors can be incorporated into 4th gen airframe structures which in itself is a big upgrade for an older generation aircraft. In fact this has already been demonstrated by various air forces around the world.

We already know what sets apart a 5th gen aircraft from a 4th gen aircraft. Such differences and limitations cannot be compensated.

 

[FuturePAF]

4th gen airframes were designed with a different philosophy in mind and this is where the limitations start in my opinion. Certain 5th gen electronics and sensors can be incorporated into 4th gen airframe structures which in itself is a big upgrade for an older generation aircraft. In fact this has already been demonstrated by various air forces around the world.

We already know what sets apart a 5th gen aircraft from a 4th gen aircraft. Such differences and limitations cannot be compensated.

So what the USAF is really asking for is a 5 - (Five minus) generation fighter that cheaper to maintain; and possibly no internal weapons bays to minimize the weight/design limitations that has on the design of the aircraft. Perhaps the best bet for the USAF would be to just acquire the KFX in its current design. It’s in advanced stage of development and without a weapons bay it has room for more fuel, so it’s range could be as great as or better then legacy platforms like the F-16. It would also make a good replacement for the F/A-18E/F for the navy.

If keeping costs (to procure, operate and maintain relatively low) is the main driver of a 5-/4++ fighter then, working with the Swedes to develop the FS2020 single engine design (but using the engine from the F-35) would probably be the most affordable option (The Swedes advertise lower maintenance and operational costs for their Gripens, then their legacy aircraft).