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Chengdu J-20 news and analysis Part III

FighterJock

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Good news for the PLAAF's 1st Air Brigade Deino, any idea as to what aircraft the J-20's will be replacing.
 

Deino

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Good news for the PLAAF's 1st Air Brigade Deino, any idea as to what aircraft the J-20's will be replacing.

Within the 1st Brigade the oldest J-11Bs.
 

Deino

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Oh please not Minnie Chan again!
I really don't know why anyone outside believe that BS,she writes and sometimes I have the feeling her true job is to spread faked information which were always eagerly picked up by any Western media.

Anyway let's take a look on her latest news and how much they contradict to everything we know and even to her own reports:


- as usual,. it is all again based on her "unknown source close to..."
- we know since mid-2019 that no J-20 has been built with AL-31FN but all since then are using WS-10C.
- why a TVC-AL-31FN-X if the WS-10B-3 was demonstrated in Zhuhai 2018 already and allegedly also tested on a J-20?
- it makes no sense to built one batch of J-20 with AL-31FN, then a second batch J-20A with WS-10C and now a third production batch of J-20B with a TVC-AL-31FNX??
- "They held a "ceremony last week, unveiling the modified J-20B" ... and started "production of the J-20B on Wednesday." ... makes no sense!

- already in 2018 she noted the J-20 is using the WS-10B (which was wrong then: https://scmp.com/news/china/militar...-stealth-fighters-missile-carrying-capability)
- and even earlier she mentioned the J-20 would already use serial WS-15s.
screwy


That all does not fit and contradicts all we know.
 

Archibald

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Minnie Chan
O RLY ?



Well, Minnie mouse, time for you to learn self-defense and become a badass. Rather than playing the damzel-in-distress.
(cuts to Minnie kicking the arse of Evil Pete, kung-fu style)


 

zebra159357

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Oh please not Minnie Chan again!
I really don't know why anyone outside believe that BS,she writes and sometimes I have the feeling her true job is to spread faked information which were always eagerly picked up by any Western media.
I was a bit skeptical about the article, since I have read some bs on scmp before. Thank you for clarification though.
 

aonestudio

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:rolleyes:

Recently, there has been another good news in the field of China's aviation industry. The "lifting body side-striped wing-duck layout" adopted by China's fifth-generation stealth fighter J-20 won the patent award issued by the State Intellectual Property Office and the World Intellectual Property Organization. . This is also the first time that China Aviation Industry Corporation Chengdu Aircraft Design and Research Institute has won a national patent award.

Compared with the traditional duck-wing layout, the J-20 adopts the duck-style layout while adding wing body fusion lift body and side wing design. By designing a pair of side strips between the canard and the main wing, the canards and side strips can increase the main wing at the same time, so that the maximum lift coefficient of the J-20 fighter exceeds 2, which is the current world lift coefficient. The largest fighter, and the US F-22 fighter lift coefficient is 1.6.


 

helmutkohl

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Chinese media has officially unveiled Shenyang's losing design for the J-20
they competed with Chengdu

pic from Alert5


the Shenyang design is called Snow Owl.

I wish I could access hui-tong's old page because there was a drawing of a stealth jet with this exact or similar tri-plane configuration
they were right a ll along.
 

BLACK_MAMBA

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J20 only has DIRECTIONAL STEALTH that is only stealth from the front and is visible in VHF band. J20s PL15 BVR's SSKP (single shot kill probability) is okay but not good. https://intelpage99.blogspot.com/2019/06/myth-of-j20s-stealth.html
This feels like a very sensationalist article especially with the all caps sentences and words spread around. I'd take it's content with a grain of salt.

There is no denying the J-20 is behind its US counterparts but that article reads with the lone agenda of bashing the Chinese and their capabilities. If anything they have shown more advancement in the field of stealth than the Russians have the last decade. With regards to sensor fusion we can only speculate how far off/close they are to parity/beating US levels of integration.
 
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stealthflanker

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Have anyone tries to estimate the fuel capacity of the J-20's ?. So yeah basically im doing a bit of "look" of it using google Earth :

J-20 size.jpg

From there one can start guessing the wing area, The reference wing area to be more exact. For what i am trying to do was to use interpolations gained from comparing known aircrafts, then make an interpolation equation. For me it's a simple excel linears, which relates wing area with wetted area and then fuel capacity. Like wetted area seems to be better indicator as it's taking account of the whole fuselage, and it's more useful as it would also allow prediction of some aerodynamics qualities.

The problem however is that i dont have many data points in the first place. This is how the chart look like including the relationship.
Wetted area vs Fuel capacity.png
The baseline data : These are from the Midland Red Star book.

Fuel Cap.png

The fuel capacity is internal fuel, no drop tanks and why its divided by 100 ?, that's for sake of readability of the chart.

So from that and my looks on the wing reference area provided by the image i arrived at wing reference area of 70.95 sqm. This then indicates wetted area of about 343.41 sqm. And estimate of fuel capacity of 11100 Kg. Accuracy is of course will be at doubt. pairing the equations with the baseline data, basically shows that the relationship can under-predict by 20% or over-predict by 6-10%.

Would love to hear suggestions for improvements.

Fuel capacity estimate can be used to guesstimate the range, endurance and avionics cooling capacity which can then be used to estimate the bound on TR module power. and then radar range.
 

totoro

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For what it's worth, I will paste my previous volume guesstimate from breaking down the drawings of planes to smaller geometric shapes.

My personal volume measurements (from available images and scaling j-20 to be 20,5 m long) say Raptor is around 46 cubic meters while J-20 is around 56 cubic meters. If true, that'd be some 20% larger. How much of it is useful? Who knows... Longer intake ducts would eat up a large portion, i'd say 4-5 cubic meters. Larger weapon bays should take around 1 more cubic meters. Internal structure could go either way, though. Future engines might be a bit larger but who's to know. Anyway, I'd say there might be room for 3-5 cubic meters of internal fuel, over the volume F-22 has.

Probably closer to 3 than 5, though.
 

stealthflanker

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For what it's worth, I will paste my previous volume guesstimate from breaking down the drawings of planes to smaller geometric shapes.

My personal volume measurements (from available images and scaling j-20 to be 20,5 m long) say Raptor is around 46 cubic meters while J-20 is around 56 cubic meters. If true, that'd be some 20% larger. How much of it is useful? Who knows... Longer intake ducts would eat up a large portion, i'd say 4-5 cubic meters. Larger weapon bays should take around 1 more cubic meters. Internal structure could go either way, though. Future engines might be a bit larger but who's to know. Anyway, I'd say there might be room for 3-5 cubic meters of internal fuel, over the volume F-22 has.

Probably closer to 3 than 5, though.
You have to put it into context. For example, F-22 Fuel tank locations and volume are not secret.
F-22A_fuel_tanks.jpg

Makes the total internal volume for fuel for F-22 to be 3082 US gal or 11166 Litres (11.6 cubic meters) Assuming fuel density of 800 Kg/m^3 the fuel weight would be 9280 Kg.

From your volume calculations the fuel would take about 25% of the aircraft. Use the same ratio for your value for J-20 then you would have about 14 cubic meters or 14000 Litres or 11200 Kg of fuel weight. Additionally you can perhaps taking count of volume distribution on how much fuel in wing and how much in fuselage. The F-22 stores about 76% of its fuel in fuselage while remaining 24% in wings.
 

totoro

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F-22 is most often cited with 8200 kg of internal fuel. https://www.lockheedmartin.com/en-us/products/f-22/f-22-specifications.html

J-20 wings are maybe 5% bigger than F-22's in area. Perhaps Lerx could add a bit more. But where J-20 would add more fuel, compared to F-22 is in the fuselage. A few meters longer section above the inlets. Those would be equivalents of the F2 and A3 tanks on the schematic above, only longer. Possibly somewhat longer F1 tanks (but not by that much) and again a few meters longer A-1 tanks.

Extremely rough estimate:
~3000 L in the tanks behind the cockpit
~5000 L in the tanks above the inlets
~4000 L in the tanks around the engines
~3300 L in the tanks within the wings/LERX

15300 L or 12.2 tons of fuel when comparing the hypothetical 9280 kg F-22 fuel load, translating to 10850 kg when comparing to the LM's claim of 8200 kg of internal fuel

but the above is still a bit pointless when the margin of error is likely huge, resulting in a ton or fuel more or less.
 

stealthflanker

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but the above is still a bit pointless when the margin of error is likely huge, resulting in a ton or fuel more or less.
The point of making estimates in general is to get something reasonable out of whatever data points or method one possess, something which methodology can be traced, having clear reasoning on why it's done the way it is and allow it to be repeated by others. To get more accuracy one have to wait for more information to be available or strive to actually find one and then improve the methodology.

In context of J-20 or other stealth fighters in development, asking for a small maybe 10 or 5% of error margin is a huge demand and basically killing any discussion in the first place.
In my view as long as the methodology looks good or can be supported scientifically, then it's fine. Any error in its result is a subject of discussion.
 

paralay

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My personal volume measurements (from available images and scaling j-20 to be 20,5 m long) say Raptor is around 46 cubic meters while J-20 is around 56 cubic meters.
According to my estimation, the volume of F-22 is 65 m3, J-20 - 64 m3. The weight of the fuel J-20 12800 kg
 

BDF

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For what it's worth, I will paste my previous volume guesstimate from breaking down the drawings of planes to smaller geometric shapes.

My personal volume measurements (from available images and scaling j-20 to be 20,5 m long) say Raptor is around 46 cubic meters while J-20 is around 56 cubic meters. If true, that'd be some 20% larger. How much of it is useful? Who knows... Longer intake ducts would eat up a large portion, i'd say 4-5 cubic meters. Larger weapon bays should take around 1 more cubic meters. Internal structure could go either way, though. Future engines might be a bit larger but who's to know. Anyway, I'd say there might be room for 3-5 cubic meters of internal fuel, over the volume F-22 has.

Probably closer to 3 than 5, though.
You have to put it into context. For example, F-22 Fuel tank locations and volume are not secret.
View attachment 641002

Makes the total internal volume for fuel for F-22 to be 3082 US gal or 11166 Litres (11.6 cubic meters) Assuming fuel density of 800 Kg/m^3 the fuel weight would be 9280 Kg.

From your volume calculations the fuel would take about 25% of the aircraft. Use the same ratio for your value for J-20 then you would have about 14 cubic meters or 14000 Litres or 11200 Kg of fuel weight. Additionally you can perhaps taking count of volume distribution on how much fuel in wing and how much in fuselage. The F-22 stores about 76% of its fuel in fuselage while remaining 24% in wings.

This older Tech Ord is weird. it clearly shows an internal fuel load of 20,650lbs and while the official fuel load is 18,448lb. It could be the 2,202lbs is ullage volume and unusable fuel. This would seemingly make sense BUT if you look at the other aircraft in that particular TO they correspond accurately to known internal fuel loads. The F-15 listed isn't accurate for the F-15C but it is correct for the F-15A. I'm not sure why the discrepancy between the F-22's fuel and the others. Listing unsuable fuel makes sense since this is part of a CFR manual but 12% unusuable seems very high, especially for a fighter.
 

TomcatViP

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IMOHO Heat transfer (cooling system). You can still burn that amount of fuel in case of an emergency but would loose gradually your stealthiness and some systems could shut down.
 

Grey Havoc

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Could well be. They had to make a lot of compromises to shrink the YF-22 down into the (what was supposed to be cheaper) F-22A. They would have been much better served by sticking with the original design.
 
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sferrin

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Could well be. They had to make a lot of compromises to shrink the YF-22 down into the (what was supposed to be cheaper) F-22A. They would have been much better served by sticking with the original design.
Lost a lot of fuel but gained speed (and probably maneuverability). Originally closer to 23k internal IIRC. Look at the aft area from below. Much slimmer in F-22A than YF-22.
 

BDF

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IMOHO Heat transfer (cooling system). You can still burn that amount of fuel in case of an emergency but would loose gradually your stealthiness and some systems could shut down.
Yeah I thought about that too. It seems odd that its that much of a limitation to reduce your usable fuel by 12%; I would think that one could accept not being able to use, say, the radar much during the recovery phase of flight which I'm guessing is the highest heat load in the avionic cooling loop. Granted there could be other items such as pumps that require the extra cooling too. Perhaps they can accept less combat capability at lower risk airfields and thus could ostensibly use that extra fuel in such a situation if the mission required it. Assuming the actual fuel volume is 20.6K. Anyway, didn't meant to drag it off topic as this is about the J-20.
 

rooster

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Could well be. They had to make a lot of compromises to shrink the YF-22 down into the (what was supposed to be cheaper) F-22A. They would have been much better served by sticking with the original design.
The yf22 was sexier anyway. :)
 
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