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


Japhethsdecendent

New Member
Registered Member
If the Americans could upgrade the F-22 with tech and equipment that's already available on the F-35, then they've got a perfect 5th gen. I recall reading the Americans wanted to build such a fighter for Japan which would also restart their own production line and if there is scale, they can actually buy a decent number of these new F-22s. Japan didn't go for that option or rather hasn't decided to commit and it's doubtful the US would allow Japan to have a superior or even equal version to them. But the F-22 would benefit from some upgrades. Obama shut the production presumably because the F-35 is overall a better value option and they decided all the way back then that fighting China will be with carrier delivered and supported fighters since regional airbases don't stand much chance. Even if airfields can be repaired, the F-22s flying from those bases will need to land in other civilian or military fields in Japan if US airfields are being repaired after missile strikes. Nearly 200 F-22s is still plenty enough. They've actually planned and timed this well considering where PCA probably is in development.
 

Japhethsdecendent

New Member
Registered Member

If the Americans could upgrade the F-22 with tech and equipment that's already available on the F-35, then they've got a perfect 5th gen. I recall reading the Americans wanted to build such a fighter for Japan which would also restart their own production line and if there is scale, they can actually buy a decent number of these new F-22s. Japan didn't go for that option or rather hasn't decided to commit and it's doubtful the US would allow Japan to have a superior or even equal version to them. But the F-22 would benefit from some upgrades. Obama shut the production presumably because the F-35 is overall a better value option and they decided all the way back then that fighting China will be with carrier delivered and supported fighters since regional airbases don't stand much chance. Even if airfields can be repaired, the F-22s flying from those bases will need to land in other civilian or military fields in Japan if US airfields are being repaired after missile strikes. Nearly 200 F-22s is still plenty enough. They've actually planned and timed this well considering where PCA probably is in development.
Hard to say where PCA is but it was deemed a better investment than restarting f-22. F-22 is still being upgraded and withing 3-5 years as I understand it we should have a better idea what MLU will be, talk of a sensor upgrade and whatever weapons like aim-260 which should be ioc in 2022. Perhaps work on other weapons coming out and perhaps an upgrade to give it some sort of DAS capability but not much details are out. I saw a little about engine upgrades for both f-22 and f-35 but that will be at least mid to late 20s. The strategy seems to be rolling out upgrades more as they seem to be needed as recent f-22 upgrades were systems other jets already had but were deemed not needed for f-22 yet. I don't think f-22 would be kept out of the fight in the pacific, it is going to be one of the highest priorities to find and protect it's airstrips. It will probably prolong a war effort as having to go slower and more deliberately as to deal with airfields and try to protect them on the ground. Those ballistic missiles can slow things down for fighters to some degree. The further out the less ballistic missiles to deal with, I imagine there aren't that many df-21-26s and then you figure some of those will be trying to hit ships and some will be most likely jammed or intercepted to some degree. f-35B/C will be mainly protecting ships and passing out targets frantically in opening days.
 

Inst

Senior Member
I've finally got it for why the J-20 has demonstrated such bad agility in airshows. Reason? It's a delta-canard with exceptionally low aspect ratios (1.6 vs 1.4 wingspan on the F-22, Su-57).

This has nothing to do with the Chines-LERX-Canard-LERX-Delta-Body Lift layout, but rather it has everything to do with why you see swept wings instead of deltas on American and Russian aircraft.

What's the problem with delta wings? Deltas, as it turns out, have lower length to wingspan ratios than other wing shapes. This is good for supersonic agility, but when it comes to subsonic agility, the lower your wingspan, the greater your induced drag. When it comes to high AOA performance, this is a good thing if you're using Chines-LERX-Canard-Delta type layouts, since body lift kicks in at high AoAs and high lift coefficients show up, but for low AOA (sustained turns) the low aspect ratio really kills it for the J-20 with induced drag.

In other words, at low speeds, the J-20 is pretty non-performing, and will likely have a higher corner speed than other fighters of its class. The defects of unstable canards (tails add lift when unstable, i.e, the F-22 actually has a 20% higher lift level than what's otherwise stated due to its tails, but canards only add lift when stable, they subtract lift otherwise) also penalize the J-20, as effective wing loading increases.

Of course, if you have a crap sustained turn rate, one easy way to fix it is to simply add more engine power to counter induced drag. And that might be the fundamental issue with the J-20; if it's designed for 180 kN engines, at 142 kN it's underpowered and the aircraft can't hit a sufficient sustained AoA for the Chines-LERX-Canard-LERX-Delta-Body Lift's Body Lift to begin kicking in. Even then, the J-20 is likely to have a higher sustained 9G speed than the F-22 or Su-57 because of the low aspect ratios.
 

latenlazy

Colonel
I've finally got it for why the J-20 has demonstrated such bad agility in airshows. Reason? It's a delta-canard with exceptionally low aspect ratios (1.6 vs 1.4 wingspan on the F-22, Su-57).

This has nothing to do with the Chines-LERX-Canard-LERX-Delta-Body Lift layout, but rather it has everything to do with why you see swept wings instead of deltas on American and Russian aircraft.

What's the problem with delta wings? Deltas, as it turns out, have lower length to wingspan ratios than other wing shapes. This is good for supersonic agility, but when it comes to subsonic agility, the lower your wingspan, the greater your induced drag. When it comes to high AOA performance, this is a good thing if you're using Chines-LERX-Canard-Delta type layouts, since body lift kicks in at high AoAs and high lift coefficients show up, but for low AOA (sustained turns) the low aspect ratio really kills it for the J-20 with induced drag.

In other words, at low speeds, the J-20 is pretty non-performing, and will likely have a higher corner speed than other fighters of its class. The defects of unstable canards (tails add lift when unstable, i.e, the F-22 actually has a 20% higher lift level than what's otherwise stated due to its tails, but canards only add lift when stable, they subtract lift otherwise) also penalize the J-20, as effective wing loading increases.

Of course, if you have a crap sustained turn rate, one easy way to fix it is to simply add more engine power to counter induced drag. And that might be the fundamental issue with the J-20; if it's designed for 180 kN engines, at 142 kN it's underpowered and the aircraft can't hit a sufficient sustained AoA for the Chines-LERX-Canard-LERX-Delta-Body Lift's Body Lift to begin kicking in. Even then, the J-20 is likely to have a higher sustained 9G speed than the F-22 or Su-57 because of the low aspect ratios.
Eurofighter.
 

Inst

Senior Member
Eurofighter.

Which has:

1.45 length wingspan as opposed to 1.61 on the J-20.
Better wing loading at 60% fuel with 1kg of munitions
Significantly better thrust to weight at 60% fuel with 1 kg of munitions (1.22 vs 1.08).

Raffy is a better example, since its lerx / canard / lerx delta is closer to the J-20, and is underpowered to boot.

===

Still, the STR vs ITR hypothesis gets us to explain why the J-20's airshow performance sucks vs its stated aims of being agile. It can do very strong ITR performances at speeds where 4th gens fall apart, but when it comes to STR, it needs higher speeds to get strong STR performance than other aircraft due to high induced drag from its low aspect ratio.

Being a high speed fighter, likewise, the J-20 actually benefits a lot from its ITR, since ITR causes energy bleed, which decreases speed, which increases turn rates in terms of degrees per second as opposed to G.
 

latenlazy

Colonel
Which has:

1.45 length wingspan as opposed to 1.61 on the J-20.
Better wing loading at 60% fuel with 1kg of munitions
Significantly better thrust to weight at 60% fuel with 1 kg of munitions (1.22 vs 1.08).

Raffy is a better example, since its lerx / canard / lerx delta is closer to the J-20, and is underpowered to boot.

===

Still, the STR vs ITR hypothesis gets us to explain why the J-20's airshow performance sucks vs its stated aims of being agile. It can do very strong ITR performances at speeds where 4th gens fall apart, but when it comes to STR, it needs higher speeds to get strong STR performance than other aircraft due to high induced drag from its low aspect ratio.

Being a high speed fighter, likewise, the J-20 actually benefits a lot from its ITR, since ITR causes energy bleed, which decreases speed, which increases turn rates in terms of degrees per second as opposed to G.
If you’re measuring total aircraft length to wingspan then what you’re measuring is not wing aspect ratio.
 

Inst

Senior Member
If you’re measuring total aircraft length to wingspan then what you’re measuring is not wing aspect ratio.

Go by induced drag formula then, using wing area as a proxy for lift.

2Lift^2 / (air density * true airspeed^2 * pi * wing length).

Isolate, you basically have a ratio of lift to wing length.

Use 78 m^2 as a wing area (although the J-20's actual wing area is closer to 75, and it's a 3 m^2 canard area that can subtract lift if the aircraft is unstable. Then: J-20's wing area to wing length ratio squared is 36.27.

The Rafale, in contrast, is 17.57, the Eurofighter is 20.

F-22 as a comparison point is 33.09, Su-57 is 31.23. F-35 is at 15.28 (although it suffers from high wing loading).

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If you look at the aircraft design, it's more designed to limit parasitic drag at higher speeds due to its lower aspect ratio, but it has higher lift-induced drag at lower speeds.
 

Inst

Senior Member
In other and more entertaining information, any news on the J-20's internal fuel and combat radius? That IS the one area where it seems to excel; some estimates make the 2000 km combat radius (i.e, can hit most of Japan from Shandong) seem credible, using a 5500 km ferry range with 4 600 gallon external tanks.
 

ougoah

Colonel
Registered Member
In other and more entertaining information, any news on the J-20's internal fuel and combat radius? That IS the one area where it seems to excel; some estimates make the 2000 km combat radius (i.e, can hit most of Japan from Shandong) seem credible, using a 5500 km ferry range with 4 600 gallon external tanks.

Excel including it's stealth that's only matched by F-22/F-35? And it's internal bays only matched by F-22 in displacement? What about its sensor suite? Sure it's an unknown but looking at how long China's fielded AESA radars on fighters, AWACS, warships and considering China's absence of weaknesses electronics, telecomm, and software technologies, I'd say it's a pretty damn safe bet the J-20 also excels in sensors and sensor fusion. Only thing fielded that is in the same league is the F-35. Not even the F-22 can make a decent case since it's been out of production for nearly a decade now. Upgrades is hard to match ground up e.g. EODAS equivalent.

With a pair of WS-15 the J-20 would also be one of the best kinematic performers ever. It's already a good enough performer with great lift, low drag, relatively low weight for a stealth fighter, and 4th gen matching thrust to weight. It's capable of supercruising with just WS-10. If we're to entertain your nonsense about one fly by being absolute proof that J-20 cannot turn (actually the fly bys show it's quite a capable turner but whatever) than why should we ignore the facts that it has better lift, lower drag owing to internal carriage and fuselage design? Why should we not also take their word that it's capable of supercruising and absolutely dominates everything else in PLAAF in supersonic flight even with modnernised WS-10 and Al-31?

What fighter outside of the F-22 and F-35 has the J-20's stealth? What fighter outside F-22 has J-20's internal carriage capability? What fighter outside F-35 has the J-20's sensor capability? J-20 only excelling in range is like India only excelling in breeding humans. It's an inconsiderate simplification and misses every point.

Point is one cannot see an F-16 flying straight because that's what that specific flight is only meant to show, is not proof that the F-16 can only fly straight and has already demonstrated its maximum speed. But that's obvious to everyone who isn't a troll or stupid. You seem to be both since you've stated the equivalent of the above with so much authority, arrogance, and plain old stupidity. Let me say this, the J-20s "performances" and fly bys in a few of the past anniversary shows were NOT airshow demonstrations like the Soviet fighters in Europe back in the 80s and 90s. They were not pulling hard, they were not flying to show the limits or even half of what it is capable of. We simply do not know. And to be honest, even the show where the J-20 pair let loose a little bit shows pretty awesome subsonic turning. Almost no afterburner used throughout contrasted to the constant afterburner used in airshows elsewhere.
 
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latenlazy

Colonel
Go by induced drag formula then, using wing area as a proxy for lift.

2Lift^2 / (air density * true airspeed^2 * pi * wing length).

Isolate, you basically have a ratio of lift to wing length.

Use 78 m^2 as a wing area (although the J-20's actual wing area is closer to 75, and it's a 3 m^2 canard area that can subtract lift if the aircraft is unstable. Then: J-20's wing area to wing length ratio squared is 36.27.

The Rafale, in contrast, is 17.57, the Eurofighter is 20.

F-22 as a comparison point is 33.09, Su-57 is 31.23. F-35 is at 15.28 (although it suffers from high wing loading).

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If you look at the aircraft design, it's more designed to limit parasitic drag at higher speeds due to its lower aspect ratio, but it has higher lift-induced drag at lower speeds.
Wing area to wing length is also not aspect ratio.

The J-20 is a bigger plane than the Rafael and Eurofighter so obviously it’s going to have greater induced drag, just like the F-22 is going to have greater induced drag than either of those fighters, but it also has larger engines for that reason.
 

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