Chengdu J-20 5th Generation Aircraft News & Discussions

[Brainsucker]

According to Gongke in CJDBY (he seems to be a reliable insider there), at current configuration, J-20's empty weight is less than Su-27.

And according to Pupu (who is a quite reliable source), the current J-20 has the highest thrust/weight ratio among all PLA fighters in service, which sidely proved Gongke's claim.

Which means, J-20's empty weight should not be more than 16 ton, which is considerably lighter than F-22's 19.7 ton and slightly higher than F-35's 13.5 ton.

About a year ago, Sina has published an article on the innovation of J-20's manufacturing process, include the intensive usage of advanced process and 3d-printing to reduce structural weight yet maintain structural strength, and advanced stealth coating tech could be another reason why J-20 is so light-weighted.

Due to J-20's optimization at super-sonic, some source claimed even with AL-31F, J-20 can reach Mach-1.5 without afterburner, but the time takes it to that speed are not satisfy super-cruise standard, but still, quite an achievement. Thanks to the J-20 aerodynamic design, actually the ratio of supersonic resistance (sorry don't know the term in English) for J-20 is just 70% of Su-27, no wonder the PLAAF J-20 pilot say when it comes to supersonic range, no one can match the performance of it.

No wonder PLAAF chief openly praised J-20 (the only PLA equipment received such honor) and rush to mass production of J-20 even without target engine.

Yes. AL-31F is the engine of flying truck (Flanker is sooo big like a truck). So if J-20 has less weight than SU-27, then yes, it's not under-powered like what people said. Actually it's quite fast

 

[ZeEa5KPul]

So if J-20 has less weight than SU-27, then yes, it's not under-powered like what people said.

It's a bit more complicated than that. As @52051 pointed out, the J-20's acceleration to > Mach 1 without afterburners in the current configuration leaves something to be desired. I believe the reason is although the WS-10B has a sticker thrust of ~130kN, that's the afterburner thrust. The dry thrust is lower as a percentage of the afterburner thrust than in the F119 (I speculate that this is because the WS-10B has a higher bypass ratio), so the non-afterburner thrust available to accelerate the J-20 is comparatively poor vis-a-vis the F-22, even though the F-22 is significantly heavier.

 

[sinait]

To be fair, Gambbit is also pretty racist - in his own words - "to the core". He always begins his arguments by attacking Chinese people in general ... rather than a specific poster

I wonder if this guy ever met a person who took the trouble to say words to try and alleviate some of the anger that may have been inadvertently caused to him due to harsh words used in the heat of a debate.
Ya, no point being nice to petty and racist types.
.

 

[ZeEa5KPul]

WS-10B has a thrust of 140 kN ... not 130.

Same point applies, the dry thrust to wet thrust ratio in the WS-10 series is lower than that in the F119 - if it were otherwise and the reported weight of the J-20 is accurate, then it would have no problems accelerating to Mach 1.5 similarly to the F-22 (in fact, the J-20 would then have a higher thrust-to-weight ratio than the F-22, so the acceleration would be superior, if both have roughly the same drag).

If we assume the supercruise rumour is accurate, this leaves the following possibilities, just based on a simple balance-of-forces analysis:

• The J-20 is significantly draggier than the F-22.
• The J-20 is significantly heavier than reported.
• The WS-10B has significantly lower wet thrust than reported.
• The dry thrust to wet thrust ratio of the WS-10B is significantly lower than the F119's ratio.
• If all of the above are false, then the F-22's acceleration to Mach 1.5 also sucks.

 

[52051]

Same point applies, the dry thrust to wet thrust ratio in the WS-10 series is lower than that in the F119 - if it were otherwise and the reported weight of the J-20 is accurate, then it would have no problems accelerating to Mach 1.5 similarly to the F-22 (in fact, the J-20 would then have a higher thrust-to-weight ratio than the F-22, so the acceleration would be superior, if both have roughly the same drag).

If we assume the supercruise rumour is accurate, this leaves the following possibilities, just based on a simple balance-of-forces analysis:

• The J-20 is significantly draggier than the F-22.
• The J-20 is significantly heavier than reported.
• The WS-10B has significantly lower wet thrust than reported.
• The dry thrust to wet thrust ratio of the WS-10B is significantly lower than the F119's ratio.
• If all of the above are false, then the F-22's acceleration to Mach 1.5 also sucks.

Actually dry-thrust is not a static number, it varies at different flight conditions.

And you should think about that: the turbine-fan engine's fan could possibly mainly serve as a drag in supersonic range, the thrust for it could be less than it is in sub-sonic phase.

That's' why the by-pass ratio of F119 is extremely low, and it is considered as optimized towards supersonic phase, whilst AL-31F is still a traditional turbine fan engine with large by-pass ratio and therefore its thrust at supersonic range will be comprised without afterburner.

So Al-31F/WS-10 will has less thrust to push J-20 at supersonic range, could be well less than its rated dry thrust.

 

[ZeEa5KPul]

Actually dry-thrust is not a static number, it varies at different flight conditions.

And you should think about that: the turbine-fan engine's fan could possibly mainly serve as a drag in supersonic range, the thrust for it could be less than it is in sub-sonic phase.

That's' why the by-pass ratio of F119 is extremely low, and it is considered as optimized towards supersonic phase, whilst AL-31F is still a traditional turbine fan engine with large by-pass ratio and therefore its thrust at supersonic range will be comprised without afterburner.

So Al-31F/WS-10 will has less thrust to push J-20 at supersonic range, could be well less than its rated dry thrust.

I see, very interesting. I take it this is the issue (supersonic performance vs range/fuel efficiency) is what variable cycle engines try to address?

 

[52051]

I see, very interesting. I take it this is the issue (supersonic performance vs range/fuel efficiency) is what variable cycle engines try to address?

To be honest I have no idea, I just read some book on that, it seems that actually trubine jet engine is optmized for supersonic phase, thats why F119 is estientally a turbine engine pretending to be turbofan one

Of cause turbine jet engine has the problem of low fuel efficieny and less rated dry thrust at a given size of flow, thats one of the reason why F-22 has a range issue.

And for the same reason, comparing to F119, F-135's increased thrust mainly come from increased by-pass ratio, thats one of the reason why despite of the high thrust of F-135, F-35 still cannot do super-cruise like F-22.

 

[gambit]

Are you trying to defend gambit claiming his BS claim about control of J-20?

The only person qualify to talk about J-20 and authentic about their talk in J-20 for the control are these few pilots who flow the real J-20.

Flip back my post and see where did I mention about these video related to what? You shall stick back at SDF and stop coming to here if you do not even know who the real culprit you shall challenge.

I think you shall refrain from BS about J-20 until you can fully absorbed what the J-20 pilot interview I posted.

Did you recently learn how to use the word 'shall'?

If what I posted so far about the J-20's canard operations are obviously BS, then you should have no problems refuting me. Why have you not? Just because you did not understand a thing I posted, that does not mean what I speculated is baseless. The claim that the J-20 is '5th gen' does not excuse it from the real laws of physics.

Let us take an aerodynamicist who have been working only on glider wings. Do you really believe that when he sees the LE flaps on the J-20's delta wings, he is going to ask: 'WTF are they?'

No, he will know EXACTLY what they are and their functions. He may not know the mathematical details of their displacement and rate of, or how much the differential pressure over the wings, but he will have the general principles of wing shape alterations for higher lift for certain flight conditions. That is what flaps -- LE and TE -- does.

When professionals encounter something new, it is only natural that they will speculate about the new thing base upon their own experiences. If I am forbidden to speculate, then what make you guys qualified to speculate on non-Chinese hardware, especially when none of you ever had anything to do with aviation outside of being a passenger on an aircraft?

So what really sticks it to you are that...

1- You did not understand a thing posted.
2- You could not refute based upon content.
3- An American is doing a better job of talking about a Chinese jet than ALL of you could.

There are plenty of keywords for you to use. If you are too lazy and/or do not have the brains to use those keywords, then STFU. Hopefully, you will learn something.

 

[yantong1980]

To be fair, Gambbit is also pretty racist - in his own words - "to the core". He always begins his arguments by attacking Chinese people in general ... rather than a specific poster

Agree, pity all of us stuck with these guy, unfortunately all of us confused by rumour, by based only by what someone talking about from another forum. Seems we need 'expert' kind of guy that based in China, really knowing what going on there, not biased. But I'm afraid it never gonna happen. Sorry being out of topic.

 

[siegecrossbow]

Agree, pity all of us stuck with these guy, unfortunately all of us confused by rumour, by based only by what someone talking about from another forum. Seems we need 'expert' kind of guy that based in China, really knowing what going on there, not biased. But I'm afraid it never gonna happen. Sorry being out of topic.

People with inside information in China probably 1) don't know fluent English and 2) aren't allowed to post on forums.

 

[yantong1980]

People with inside information in China probably 1) don't know fluent English and 2) aren't allowed to post on forums.

Agree. Seems pretty much about J-20 will stay 'stealth', even we know what it look like now.

 

[phancong]

Did you recently learn how to use the word 'shall'?

If what I posted so far about the J-20's canard operations are obviously BS, then you should have no problems refuting me. Why have you not? Just because you did not understand a thing I posted, that does not mean what I speculated is baseless. The claim that the J-20 is '5th gen' does not excuse it from the real laws of physics.

Let us take an aerodynamicist who have been working only on glider wings. Do you really believe that when he sees the LE flaps on the J-20's delta wings, he is going to ask: 'WTF are they?'

No, he will know EXACTLY what they are and their functions. He may not know the mathematical details of their displacement and rate of, or how much the differential pressure over the wings, but he will have the general principles of wing shape alterations for higher lift for certain flight conditions. That is what flaps -- LE and TE -- does.

When professionals encounter something new, it is only natural that they will speculate about the new thing base upon their own experiences. If I am forbidden to speculate, then what make you guys qualified to speculate on non-Chinese hardware, especially when none of you ever had anything to do with aviation outside of being a passenger on an aircraft?

So what really sticks it to you are that...

1- You did not understand a thing posted.
2- You could not refute based upon content.
3- An American is doing a better job of talking about a Chinese jet than ALL of you could.

There are plenty of keywords for you to use. If you are too lazy and/or do not have the brains to use those keywords, then STFU. Hopefully, you will learn something.

Your not American, your just a naturalized US citizen. After 5 yrs holding US green card, anyone can become a US citizen.

 

[seesonic]

If you are referring to @gambit, he is an asset to these forums.

Have some respect for a retired fighter pilot.

He has more experience and knowledge about these matters than you or I ever will.

Are you gambit?

I never claim I am an expert unlike some who BS about some canard control of J-20 as if he ever flow or sit inside a real J-20 cockpit? Got it?

Thats why we have leechers leeching off chinese members such as you to do free translation for them while they leech off with your translation.

 

[Avicenna]

Your not American, your just a naturalized US citizen. After 5 yrs holding US green card, anyone can become a US citizen.

Being a US citizen makes him American.

Are you gambit?



Thats why we have leechers leeching off chinese members such as you to do free translation for them while they leech off with your translation.

LOL no I’m not gambit.

 

[phancong]

Being a US citizen makes him American.



LOL no I’m not gambit.

He spoke in a way of US born American, many in here opinion of him rode on the success of the US to belittle other nation but everyone knew the land he was born and raise up at still a poor 3rd world nation.