J-20 5th Generation Fighter VII

Fedupwithlies said:

Bummer.

You sure you don't want to leak some classified documents to us? At this rate we're going to be less informed than the Warthunder forums.

Oh well, I guess we'll have to wait for Gaijin to release the F-22 in-game to get the good stuff.

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The fact that Warthunder has caused so many information leaks on so many systems is genuinely hilarious. I don't think Warthunder will be releasing the 5th generation fighters into their games, though. At least, they won't release it unless it's a premium.

But yes, enough of this! We should be talking about the J-20.

Fedupwithlies said:

Bummer.

You sure you don't want to leak some classified documents to us? At this rate we're going to be less informed than the Warthunder forums.

Oh well, I guess we'll have to wait for Gaijin to release the F-22 in-game to get the good stuff.

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source code has been decompiled

Fedupwithlies said:

My understanding is that Patches is saying the F-22 is a one trick pony, that is A2A and it does it extremely well, better than the J-20, but the J-20 can do other things like (I'm just guessing here) command drones, act as a sensor node, and generally fit in better with the Chinese strategy than the F-22 can fit in the US strategy.

In other words, F-22 vs J-20 goes to the F-22, a strike package with F-22s vs a strike package with J-20s would go to the J-20.

Which is probably why the US would send F35s for that strike package.

They've been pretty consistent in saying that, I don't think I've read anything they've typed that contradicts that.

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Even though nobody here including Patches himself really knows if his assessment is correct, this really does make sense and is in line with Chinese philosophy. When the enemy is strong at one point, don't dick-head it out with him on that point; defeat him by undermining him where he is weak. Same reason China didn't have a shouting match with Trump but ended up winning the trade war anyway. The US has fantastic engine technology and everything lines up for them to make a sheer A2A marvel, so instead of trying to use weaker engines to engineer a jet that can outmuscle a Raptor at its best event, make a more overall excellent jet that can more comprehensively use resources to defeat the Raptor (even if it has the same or similar tools). Not saying he's right, but if he is, it makes sense with how China does things.

Can someone give a a TL;DR of the last pages?

taxiya said:

Everything is possible without data. Proposing a possibility just because of lack of evidence to prove either way is just wild, isn't it?

The paper does not give exact data. However, it emphasizes in multiple times that the improvement is NOT only lift in low speed, BUT also in lift-drag ratio.

This is what J-20 did

Increase the static instability from commonly used 3% to 10%. That leads to improve subsonic and trans-sonic lift-drag characteristic.
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You have to read the full paper to get a feeling of where J-20 may be. Bits and pieces from my unprofessional translation is not enough.

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My entire point is we don't have the data to call it one way or another just from this paper alone, not trying to prove anything. Now it is entirely possible due to canard-lerx-delta vortex coupling J-20 may enjoy higher L/D over F-22 at all AoA/airspeed/altitude, indeed I would be positively overjoyed if that is the case.

However low aspect ratio delta wings is known to have higher drag increase from AoA due to larger cross section area to the flow direction, so I need a little more data to see how much does all that complex vortex coupling helps in this regard.

enroger said:

My entire point is we don't have the data to call it one way or another just from this paper alone, not trying to prove anything. Now it is entirely possible due to canard-lerx-delta vortex coupling J-20 may enjoy higher L/D over F-22 at all AoA/airspeed/altitude, indeed I would be positively overjoyed if that is the case.

However low aspect ratio delta wings is known to have higher drag increase from AoA due to larger cross section area to the flow direction, so I need a little more data to see how much does all that complex vortex coupling helps in this regard.

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The F-22 isn’t absolved from the same general tendencies wrt to higher drag increases at higher angle of attack from more cross sectional area of the wing though. It’s also a delta (or more specifically a low aspect trapezoid). And some of this disadvantage actually reverses itself once you’re at higher altitudes or once you’re at higher speeds, especially as you enter the transonic range where shock drag starts to take over. The drag from cross section is a function of wing area after al, so a higher aspect wing with a similar wing area would be seeing similar effects at an angle of attack.

EDIT: I’d also add that TVC probably does help a bit here, because if you’re fighting drag during a sustained turn at a particular bank angle you don’t have to pitch up your nose up to get a better lift coefficient while eating more drag. You can simply keep your bank angle and have your vectored thrust add more to your forward vector to counteract that drag.

latenlazy said:

The F-22 isn’t absolved from the same general tendencies wrt to higher drag increases at higher angle of attack from more cross sectional area of the wing though. It’s also a delta (or more specifically a low aspect trapezoid). And some of this disadvantage actually reverses itself once you’re at higher altitudes or once you’re at higher speeds, especially as you enter the transonic range where shock drag starts to take over. The drag from cross section is a function of wing area after al, so a higher aspect wing with a similar wing area would be seeing similar effects at an angle of attack.

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F-22 will suffer the same tendencies to a lesser degree due to higher aspect ratio wings -> proportionally shorter wing chord. You're right about the tendencies reverses, J-20 being a low aspect ratio canard delta will absolutely have superior L/D at high speed high altitude regime no doubt about it. The question is L/D versus AoA in subsonic regime, how much does the complex coupling scheme helps? We don't know

enroger said:

F-22 will suffer the same tendencies to a lesser degree due to higher aspect ratio wings -> proportionally shorter wing chord. You're right about the tendencies reverses, J-20 being a low aspect ratio canard delta will absolutely have superior L/D at high speed high altitude regime no doubt about it. The question is L/D versus AoA in subsonic regime, how much does the complex coupling scheme helps? We don't know

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The key factor in the effect you’re describing is going to be wing area. Higher aspect actually induces a bit more drag than lower aspect for the same wing area because you have a wider span facing the free stream. The tradeoff of course is that the higher aspect wing should also get better lift, all else held equal. Also see my edit wrt to TVC. I think that’s also going to play a role here. But since both designs employ a lot of vortex lift with strong coupling dynamics it really is hard to say.