J-20 goes operational again

Military aircraft - Post cold war aircraft, including for example B-2, Gripen, F-18E/F Super Hornet, Rafale, and Typhoon.
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inst

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Unread post25 Sep 2019, 21:22

Weight estimate on the J-20 would be between 17.5 to 22 tons empty, depending on whose kool-aid you're drinking and how much weight growth occurs on the J-20. Dimensions would be roughly 20.4 to 20.6 meters long with 12.9 meters wingspan.

And I agree on the weapons bay; the J-20's weapons bay capacity is only superior to the F-35's because of the side bays, which likely will end up getting eaten up by pods or short-range missiles. Otherwise, it has roughly the same bay volume, although the Chinese have been ranting about their larger weapons bay. I also think attaching missiles to the bay doors is doubtful given that it'd increase weight further and make the bay doors more liable to fail.

Re: Rick Joe; that's Bltizo (Blitzo) at SDF. I assume Joe is actually Zhou. I've been here in part because I've had massive arguments with the SDF folks, they're committed to the J-20 as a dogfighter narrative because they overreacted to the Western media calling it an interceptor or a striker (it can dogfight, but it's more in the class of a YF-23 or a Eurofighter than an F-22. Then we have the missing guns, although there's a placement location for gun ports). Likewise, they get really pissy when I bring up the Su-57 as a Chinese import because of matters of nationalist prestige, with the usual arguments that the Russians can't get it that cheap, etc etc etc.

They also try to play the bay depth argument because they want to denigrate the J-20 as a striker, when we've seen F-35-style munitions at Chinese arms expos, indicating that a strike role is likely in the future.

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I don't see the J-20 as a carrier fighter as impossible; as we've stated, it's smaller than it looks and if the Chinese can get Su-33 / J-15 off their carriers, they can get a navalized J-20 off it. The Type 003 carriers they have on the drawing board are slated to get EMALS, so the J-15 being crippled by ski-jump problem will be solved.

The USN, I know, wants a replacement for the F-14 Tomcat which is a heavyweight naval interceptor. The F-35s are medium-weight and are more reliant on technological superiority to compete, and while the Super Hornets are heavyweight, they're basically a wing extension and remoulding on the standard Hornet and don't come with the same large aperture radar as the F-14, although the F-14 IIRC never received AESA upgrades.

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Edit: on the weight, on two dimensions, the J-20 should be about 2.5% larger than the F-22. Body height seems to be about the same. The Chinese claim the J-20 is 20% titanium, but their 3D titanium manufacturing results in 40% weight savings, so the aircraft should be about 12% lighter than otherwise. 18,000 KG seems reasonable as a weight estimate, although you could go lower or higher depending on subsystems.

If you go by the J-15 / Su-33 compared to the J-11 / Su-27, there's roughly a 7% weight gain. So a navalized J-20 should be about 19,000 kg vs a wing area of 75-76 square meters. Stuff in 12,000 kg of fuel and munitions, you get about 413 kg/m^2 wing loading on take-off.
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weasel1962

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Unread post25 Sep 2019, 23:20

Can wait until a flying prototype appears before commenting. Right now it's too early. Neither j-20 or j-31 can be carrier fighter without modification to the base design.
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Unread post26 Sep 2019, 10:40

Corsair1963 wrote:So, what are the dimensions of the J-31 Weapons Bays???


Weapon bay is similar to J-20:
https://defense-update.com/wp-content/u ... ns-bay.jpg

Primarily A-A oriented, any bigger weapon would problematic for second AAM. It isn't like F-35, F-22 or Su-57 which can carry two big weapons and two AAM.
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Unread post01 Oct 2019, 07:25

The J-20 weapons bay is something like 400-600mm depth, 4-4.5 meters long, 2 meters wide. The J-31 bays seem considerably smaller than the J-20 bays, mostly in the width dimenison, although I wouldn't be surprised if the depth was lower as well.
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Unread post01 Oct 2019, 08:29

The J-31 bay is the same size as the J-20.
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FC-31V2 dimension estimations.jpg
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Unread post01 Oct 2019, 09:46

Remeasured, then is the J-20 weapons bay 2.4-2.5 meters? I recall clearly that the J-20 has a wider weapons bay than the J-31.
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Unread post02 Oct 2019, 15:12

weasel1962 wrote:The J-31 bay is the same size as the J-20.


Pretty shameless knock off of the F-22 wing/fuselage/canopy, coupled with inlets from the F-35. I have a lot more respect for the J-20's design, albeit you could argue that too was inspired by the Mig I.44. While I think the J-20 may prove to be truly VLO, I don't think the same thing can be said about the J-31. I see it as built for export, vs. filling out Chinese aviation wings with something to succeed the J-10. I think J-10B's and C's are going to be around for a long time. The J-10C has RCS reduction features, and this I think they'll deem "good enough", especially considering USAF will be hanging on to lots of legacy F-15's and 16's in coming years...
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Unread post02 Oct 2019, 18:43

mixelflick wrote:
weasel1962 wrote:The J-31 bay is the same size as the J-20.


Pretty shameless knock off of the F-22 wing/fuselage/canopy, coupled with inlets from the F-35. I have a lot more respect for the J-20's design, albeit you could argue that too was inspired by the Mig I.44.


Ahem:
ce_002.jpg
"There I was. . ."
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Unread post02 Oct 2019, 18:48

weasel1962 wrote:The J-31 bay is the same size as the J-20.


Even though I don't like it because it is clear copy of other designs, airframe looks excellent in therms of stealth, I would say better then anything else (I exclude materials to be clear).
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Unread post03 Oct 2019, 08:01

Neither J-20 or J-31 is an exact copy of any aircraft. The general shape may be there but the reality is aeronautical design is designed around the engines. Simplistically, the engines being different will result in a different aircraft. The size of the wings will then be dependent on the fuselage, weight etc. No doubt the shape of the wings could have relied upon F-35/F-22 as a basis but that's just incorporating what others have learnt.

If one takes the definition that if it looks roughly alike then its a copy then every fighter designed to date is a copy. Example, in order to break the sound barrier, designers realized that the shape of the plane had to take into account both wings and fuselage together (previously designed separately). Today, everyone applies the same principle, otherwise one can't break the sound barrier. One might argue everyone is a copy but imho, that's too broad a definition.

Today's fighter shape is such that in order to achieve stealth, that's the optimal design for stealth. If designers can find something better, they would but logically, fighters that want to achieve the level of stealth would have to adopt something like a flying wing design. You can't achieve stealth otherwise (unless a breakthrough happens - which may happen with the PCA/NGAD). The J-20 is slightly different in view the Chinese incorporated canards into the design. I originally thought it would render the design less stealthy but clearly they incorporated the canards as a necessity for the performance of the aircraft.

There are so many basic design differences to the mig 1.44 that only a lay person would suggests its the same. Its like saying airbus copied boeing for all their airliners because both have 2 wings and a tail and look alike. Just a simple basic feature difference is the location of the intakes. Whilst China has a well earned reputation for a copy nation, I think objectively, both J-20 and J-31 designs are really local designs. Another person who has the same mig 1.44 blueprints would not have come up with a J-20 design.
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Unread post03 Oct 2019, 08:08

I would say the J-20 and J-31 are inspired by the US F-22 and F-35. Yet, not copies per se...
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Unread post03 Oct 2019, 16:12

milosh wrote:
weasel1962 wrote:The J-31 bay is the same size as the J-20.


Even though I don't like it because it is clear copy of other designs, airframe looks excellent in therms of stealth, I would say better then anything else (I exclude materials to be clear).


A lot of people like the J-31 simply because it resembles the F-35 and F-22. But it's a lazy fighter that won't be stealthy in comparison to F/A-X and F/A-XX fighters. They'd have been better off trying to clone the YF-23 platform, but Shenyang Aerospace Corporation is lazy and keeps on losing contracts to Chengdu, which did the J-20.

As for the J-20, it's original mainly because it incorporates so many different design ideas. There's actually two separate sets of LERX on the J-20, in front of the canard and behind the canard, similar to the Rafale. There's ventral strakes as on the J-10 and F-16, and the long-coupled canard evokes the Eurofighter Typhoon with AMK, using LERX to compensate for poor vortex generation off long-coupled canards.

Then there's the anhedral-dihedral canard-wing configuration. The canards are actually angled to match the plane of the opposite wing, allowing the canards to be lifted above the main wing as on most canard fighters outside the Su-30 and Su-33.

@Corsair: in the sense that they're all stealth aircraft and stealth shaping imposes limitations, sure. But the J-20 is definitely original insofar as it just implements too many different ideas not to be original. Going by your reasoning, all aircraft are knock-offs of American aircraft because of the Wright Brothers' flight at Kitty Hawk.
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Unread post03 Oct 2019, 17:12

sferrin wrote:
mixelflick wrote:
weasel1962 wrote:The J-31 bay is the same size as the J-20.


Pretty shameless knock off of the F-22 wing/fuselage/canopy, coupled with inlets from the F-35. I have a lot more respect for the J-20's design, albeit you could argue that too was inspired by the Mig I.44.


Ahem:
ce_002.jpg



And this is who's concept art?

Tough to say based on the illustration.
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Unread post03 Oct 2019, 17:16

weasel1962 wrote:Neither J-20 or J-31 is an exact copy of any aircraft. The general shape may be there but the reality is aeronautical design is designed around the engines. Simplistically, the engines being different will result in a different aircraft. The size of the wings will then be dependent on the fuselage, weight etc. No doubt the shape of the wings could have relied upon F-35/F-22 as a basis but that's just incorporating what others have learnt.

If one takes the definition that if it looks roughly alike then its a copy then every fighter designed to date is a copy. Example, in order to break the sound barrier, designers realized that the shape of the plane had to take into account both wings and fuselage together (previously designed separately). Today, everyone applies the same principle, otherwise one can't break the sound barrier. One might argue everyone is a copy but imho, that's too broad a definition.

Today's fighter shape is such that in order to achieve stealth, that's the optimal design for stealth. If designers can find something better, they would but logically, fighters that want to achieve the level of stealth would have to adopt something like a flying wing design. You can't achieve stealth otherwise (unless a breakthrough happens - which may happen with the PCA/NGAD). The J-20 is slightly different in view the Chinese incorporated canards into the design. I originally thought it would render the design less stealthy but clearly they incorporated the canards as a necessity for the performance of the aircraft.

There are so many basic design differences to the mig 1.44 that only a lay person would suggests its the same. Its like saying airbus copied boeing for all their airliners because both have 2 wings and a tail and look alike. Just a simple basic feature difference is the location of the intakes. Whilst China has a well earned reputation for a copy nation, I think objectively, both J-20 and J-31 designs are really local designs. Another person who has the same mig 1.44 blueprints would not have come up with a J-20 design.


That's why I used the word inspired, not copied when referring to the J-20 and its likeness to the Mig I.44. Regardless of design input, inspiration etc. I think we can all agree it's going to be limited by its motors. By the time China develops engines with adequate reliability/thrust etc., the basic airframe is going to be dated. I think there's a reason we don't see hundreds in service already (according to most estimates). The engine/airframe is a total mis-match, worse than the F-14/early TF-30's. They're only going to glean so much from the SU-35's engine, and it isn't designed to super-cruise, be stealthy in the RF/IR spectrum etc..
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Unread post04 Oct 2019, 01:49

inst wrote:Remeasured, then is the J-20 weapons bay 2.4-2.5 meters? I recall clearly that the J-20 has a wider weapons bay than the J-31.


2m wide. Same size. The depth is shallower than F-35. That will restrict fat-bodied A2G munition (but some have argued its still feasible). Can still fire ARMs or missile-type AGMs.

For many years, PLAAF doctrine operated separate fighter and attack regiments with separate distinct roles. Today its blurred with multi-role aircraft. The J-20 is still assumed to be an air superiority fighter supplemented by J-10s and J-16s before the latters are re-tasked to A2G.
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