MiG 19 -> Soviet F-5 -> Soviet F-20?

[tomo pauk]

Lets send the MiG company on the path not chosen wrt. their 'budget' fighters.
Instead, they make a spin-off of the MiG 19 that has a wing better suited for high speeds (not 8.74% t-t-c at root as on the -19, but under 4.5% as it was case with MiG-21; wing is also of the shorter span), and lateral intakes that leave the nose free for an actual radar set. All of this happens in the second half on 1950s.
By second half of 1960s, they move on 1-engined version of this, but with slant intakes akin to what MiG-25 had for better high AoA abilities.
By late 1970s/early 1980s, engine is RD-33, wing is of modern shape for better low-speed abilities.

How much of an impact this can have on the appeal of these fighters? Commercial success vs. what was it historically so? What for late 1980s/early 1900s?

 

[CV12Hornet]

A swept-wing MiG-21 is not impossible - the initial trials between the swept-wing Ye-2 and delta-wing Ye-5, shockingly, went in favor of the swept-wing Ye-2. Further development of the Ye-5 wing design led to the OTL MiG-21, which outperformed the Ye-2, but it's entirely possibly to make a POD that prompts the Soviets to go all-in on the Ye-2 design. Similarly, the R-11 engine was decidedly troublesome in its early goings, and weight-wise you could replace the single R-11 with twin RD-9s, though you'd get a larger, wider fuselage.

However, I don't think it would enjoy the popularity the MiG-21 did on the global fighter market - this would be heavier and less maneuverable than the OTL MiG-21, and given the state of Soviet radar and missile development would likely not be able to compensate with BVR capabilities even with a solid nose.

 

[overscan (PaulMM)]

The primary point of departure is the 1970 "MiG-23", where many Mikoyan engineers were against the size increase. The thing is, the size of the avionics demanded by the mission really made it impossible to stay with the MiG-21 size airframe.

So the "MiG-23" in this timeline probably can't have BVR weapons and lookdown radar.

It have to use the R-25 engine (produced from 1971)

RD-33 was unlikely be mature enough until late 1980s for a single engine fighter.

 

[tomo pauk]

However, I don't think it would enjoy the popularity the MiG-21 did on the global fighter market - this would be heavier and less maneuverable than the OTL MiG-21, and given the state of Soviet radar and missile development would likely not be able to compensate with BVR capabilities even with a solid nose.

Heavier it would've been, but also with more thrust - 74 kN vs. 60.
Missiles that Soviets were willing (or were able to) install on the 'frontline' fighters were nothing fancy anyway until we're in the 1970s.

So the "MiG-23" in this timeline probably can't have BVR weapons and lookdown radar.

It have to use the R-25 engine (produced from 1971)

Yes, the R-25 is probably the engine of choice.
Fighter will probably use a better radar than it was on the MiG-23S and MiG-2bis, together with R-23s (those were not all that great wrt. range).

RD-33 was unlikely be mature enough until late 1980s for a single engine fighter.

I'd wager to say early 1980s.

 

[overscan (PaulMM)]

I'm not sure on RD-33, but AL-31F had reliability issues early on.

 

[kocovgoce]

swept-wing MiG-21 something like the family of su-7 11 and su-17/22