World's 5th gen fighters - relative strengths and weaknesses


Inst

Senior Member
Stealth is probably better than the Su-57, but mainly because the Russians don't care that much. The J-20, contrary to what people think, does not have planform alignment on the canards (the canard angle to the opposite wing is not 0), and it has ventral fins sticking out.

It is quite possibly as stealthy as the F-22, but compared to the F-35, which is a smaller platform, it'd be much more challenging. Chinese analysts have already admitted that it's not as stealthy as the F-35, and hopes to use its stronger radar to compensate. And that's only in radar stealth bands. The IR stealth is going to be worse as it doesn't have flat nozzles like the F-22 does, and it has greater total engine power than the smaller F-35. And since the J-20 is high-speed optimized, once it goes high-speed (Mach 0.9 to Mach 1.5), it becomes rather bright on IR sensors.

As for sensor suite, it has an advantage over the F-22 in that it has both EOTS and EODAS, but the F-22 is has been upgraded to an IRST itself, in place of its MAWS.

Compared to the F-35, it has a larger radar, but notably, the EOTS aperture on the J-20 is not larger than on the F-35, implying that the J-20 won't have an IR sensor superiority compared to the F-35, a key design error that should have been remedied.

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Kinematically speaking, first, when it comes to WVR agility, as I've said before, you're dead if you show up on sensors. Short-ranged WVR missiles track very well using your IR signature, or a UV displacement signature. DIRCM can work, but put enough missiles on the target and DIRCM gets overwhelmed.

And when it comes to WVR agility, we're trying to quantify the J-20's agility. The overall airframe design (i.e, increased lift from the LERX-Canard-LERX-Wing formula) only increases lift at high AoA; it's an excellent ITR performer that relies on engines for STR. Being in the low speed regime where you're not 9G capped, by the way, also means you're WVR missile bait.

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But that's like latenlazy's agenda. He thinks that the J-20's agility advantages (and the F-35 is actually quite agile on low fuel, which it'll have when it's defending a base or in short range) are sufficient to make it an effective air superiority platform. I, on the other hand, think it's equal to the F-35 (at best) because future air-to-air combat will be dependent on BVR-type combat using sensors and stealth, including datalinked sensors from AEW&C (H-20).

That said, however, even if you buy (and we can argue about this endlessly) my argument about the J-20 not being such an effective air superiority fighter, it HAS exceptional range. As I've told Indians, you can base J-20s in Chengdu, and they'd be able to fly to either the Indian border or Taiwan on internal fuel. It makes it so that the Indians can't even dream of hitting J-20s in Chengdu on the ground. The same applies to the Americans; they can try to launch Tomahawks or whatever newfangled strike missile they've come up with, but their strike missile range is dwarfed by the J-20's range, either with or without tanks.

This makes the J-20 an excellent defensive fighter simply because you can have multiple lines of J-20 bases, some of which are intended to be offensive, others which are intended to be defensive. At 2000 km combat radius (based on 5500 km and subtracting for external fuel tanks, then using a .4 modifier), you can actually further extend the combat radius by using bases further afield; take off from Chengdu, land in Jiangxi, and you can supercruise part of the way (likely supercruise range will be around 1100 km) because you simply don't need the fuel that'd otherwise be used to return to base.

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In other words, like the Mitsubishi Zero, the key selling point of the J-20 is its sheer range. No other fighter, barring perhaps the classified PCA aircraft, can go as far as the J-20 can, allowing it to strike (with weaker strike missiles, of course) further than other aircraft can, or defend Chinese airspace from further inland than other aircraft can. Even if you compare it to the Su-57 on internal fuel, you're still looking at another almost 50% combat radius.

For humor's sake, the range of the Mitsubishi Zero is roughly 1900 km. If you look at most fighter aircraft to date, most of them are short-ranged on internal fuel. What we finally have with the J-20 is a modern jet aircraft that can match the Zero when it comes to combat radius.
 
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Inst

Senior Member
The range and speed is fairly important; the high range means that the J-20 can sacrifice superfluous range just to hit afterburners or supercruise and reduce range. And think about it this way, the J-20 has almost twice the F-35A's range (and twice the F-35B's range).

The combination gives China a very strong OODA / strategic advantage; i.e, the Chinese can concentrate J-20s from a dispersed area to force the enemy to meet an unexpected concentration of force, while the combination of speed and range means that the enemy can be picked off (i.e, 12 F-35s vs 24 J-20s) through force concentration, just as with Korea.

That said, the high range and speed on the J-20 seems more oriented toward escorting JH-XXs in its present version. The J-20 is abysmal at strike right now, and would need substantial redesign before it ever becomes a credible strike fighter. Still, the very fact that you can hit F-35s on their airbase from virtually out of range is a strong plus for the J-20.
 

Inst

Senior Member
You really shouldn't have removed the range question. Let's put it another way, the Rafale likely has around 800 km of combat radius on internal fuel. For the J-20, if it's got a load of internal fuel at 12,000 kg, and has a combat radius of 2000 km on internal fuel in an air to air mission, the J-20 only needs 25% of its internal fuel to perform at this range. If you assume the J-20's bearing 1000 kg worth of weapons, the weight comes down to between 22,500 and 23,500 (based on 18.5 tons to 19.5 tons empty weight).

Under this circumstance, thrust to weight rises to about 1.24 with 137 kN WS-10C or 1.28 with 142 kN WS-10C. Wing loading drops to only 300 kg / m^2.

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As mentioned before, with the F-35, its kinematics improve significantly if it's allowed to dump fuel due to its very high fuel fraction (40%). If the J-20 has a 2000 km range, the same applies even more (the F-35C has a 1350 km combat radius, meaning a 800 km radius is is only 60% of its fuel capacity or about 35% at its destination point, while a J-20 can do it on 40% or 25% at its destination point).

If you have almost twice the combat radius of an F-22, well, your performance improves significantly because at the same combat radius, you have significantly less fuel, around 35% of 12,000 kg (4200 kg) vs 60% of 8200 kg (4920 kg). Over approximately the same wing area, you end up with better wing loading and competitive thrust to weight to a higher-powered fighter because you're lighter.


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The realistic combat range on internal fuel matters, because if it's good, you have much better weight performance at short distances. It is strategically extremely useful in being able to deploy the aircraft over long distances (away from enemy anti-airbase weapons) and operationally useful by giving you the ability to have a much lighter plane at the destination.

Consider: the J-20 is designed for low parasitic drag (i.e, relatively low drag at cruising distances), takes inputs from the high fuel fraction F-35, and is a larger plane than the F-35. Does it follow that the J-20 has an excellent combat radius?
 
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Inst

Senior Member
Once again, you're being asked about the J-20's combat radius. There are some claims on cjdby.net citing 2000 km combat radius. There are other claims elsewhere that claim a closer to 1100 km range, as well as things in between.
 

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