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.
  • Author
  • Message
Offline

milosh

Elite 1K

Elite 1K

  • Posts: 1229
  • Joined: 27 Feb 2008, 23:40
  • Location: Serbia, Belgrade

Unread post07 Jan 2021, 09:28

@charlielima223

I was talk about configuration, Su-57 is same configuration as F-22 or F-23 not canard and no ventral fins as J-20.

Canard configuration isn't good because canards are radar reflectors in case of J-20 huge one:
https://i.redd.it/pfw4j47mqik11.jpg

J-20 canards don't have platform alignment. So you have quite long surfaces which aren't angled as wings not good at all from stealth point of view:
https://geopolitics.news/wp-content/upl ... -00599.jpg

Radar blocker isn't something not used before in stealth design, F-23 would have one too, its intake bend is simply short to be efficient enough compared to F-22 or F-35. F-32 would have one too, and in case of F-32 engine is lot less hidden and bigger then in case of Su-57.

Also radar blocker in case of Su-57 is only used in subsonic flight, in supersonic one ramps hide engine without problem something which is overlooked:
https://fullafterburner.weebly.com/uplo ... n_orig.jpg

@jessmo112

J-20 doesn't use old AL-31 (Su-30 engine before upgrade).

J-20 have ~290kN thrust, if we do math it would need to have ~32tons on loaded weight to have same T/W ratio sa F-35A with 50% of fuel.

So there is plenty of thrust already there but Chinese want better super cruise engine.
Offline

jessmo112

Senior member

Senior member

  • Posts: 335
  • Joined: 16 Mar 2020, 02:09

Unread post07 Jan 2021, 11:02

So you think that the J-20 is only 32 tons fully loaded?
Offline

milosh

Elite 1K

Elite 1K

  • Posts: 1229
  • Joined: 27 Feb 2008, 23:40
  • Location: Serbia, Belgrade

Unread post07 Jan 2021, 11:15

jessmo112 wrote:So you think that the J-20 is only 32 tons fully loaded?


Nope, I only point out how heavy J-20 need to be to have ratio as F-35A with 50% of fuel. 32tons, and I doubt J-20 is 32tons with just 50% of fuel, wiki data I didn't check it myself but I think it is 50% + weapon load.

Btw empty weight of J-20 is 20tons (anything lot heavier is nonsense when Su-34 is +22tons) so you could be right, fully loaded J-20 could be 32tons.
Last edited by milosh on 07 Jan 2021, 11:22, edited 1 time in total.
Offline

jessmo112

Senior member

Senior member

  • Posts: 335
  • Joined: 16 Mar 2020, 02:09

Unread post07 Jan 2021, 11:21

Also the wiki page says this.
Crew: one (pilot)
Length: 20.4 m (66.8 ft)
Wingspan: 13.5 m (44.2 ft)
Wing area: 78 m2 (840 sq ft)
Empty weight: 19,391 kg (42,750 lb)
Gross weight: 32,092 kg (70,750 lb)
Max takeoff weight: 37,013 kg (81,600[124] lb)
Fuel capacity: 11,340 kg (25,000 lb) internally
Powerplant: 2 × Saturn AL-31FM2[56][57] afterburning turbofan, 145 kN (33,000 lbf) with afterburner

So why would you use J-20 numbers using the,AB to match the F-35, in dry thrust. Loaded weight is a normal combat load and not gross weight.
Did I miss something?


Crew: 1
Length: 51.4 ft (15.7 m)
Wingspan: 35 ft (11 m)
Height: 14.4 ft (4.4 m)
Wing area: 460 sq ft (43 m2)
Aspect ratio: 2.66
Empty weight: 29,300 lb (13,290 kg)
Gross weight: 49,540 lb (22,471 kg)
Max takeoff weight: 70,000 lb (31,751 kg)
Fuel capacity: 18,250 lb (8,278 kg) internal
Powerplant: 1 × Pratt & Whitney F135-PW-100 afterburning turbofan, 28,000 lbf (120 kN) thrust dry, 43,000 lbf (190 kN) with afterburner
Offline

milosh

Elite 1K

Elite 1K

  • Posts: 1229
  • Joined: 27 Feb 2008, 23:40
  • Location: Serbia, Belgrade

Unread post07 Jan 2021, 11:30

Okey wiki isn't precise enough about F-35A t/w ratio with 50% of fuel (1.07:1 is quite low for max AB)

so I did math:

F-35A max AB thurst is 190kN,loaded weight (50% fuel and four AIM-120) is ~18tons

190kN or 10.56kN/ton

J-20, max AB thrust with AL-31FM3 or its clone ~290kN, so to have 10.56kN/ton, loaded weight is 27.46tons

Empty weight of J-20 isn't public but highest what i find is 20tons, so fuel and weapons is ~7.5tons

One ton for missiles (four PL-15 and two PL-10) and 6.5tons of fuel, if that is 50% of fuel then it carry 13tons of fuel which fit in estimated role of J-20 aka Chinese Foxhound or fast long range interceptor.

So max weight of J-20 is 20+13+1, 34tons of couse if it really carry 13tons of fuel.

With super cruise engine it would have superb supersonic range. I wouldn't be surprise to see Chinese bought Su-57 only to get AL-51 for J-20, I doubt WS-15 is good as AL-51 is.

USAF could have something similar if they choice F-23 but they didn't. F-23EMD would two additional fuel tanks compared to YF-23 and would be less draggy then YF-23 and YF-23 already showed superb super cruise capability doing whole test sortie supersonic.
Offline

madrat

Elite 2K

Elite 2K

  • Posts: 2853
  • Joined: 03 Mar 2010, 03:12

Unread post07 Jan 2021, 13:16

I can remember when internet guessing tried to assert the J-20 was merely 60 feet long. Clearly the guesses on weight are along the same wishful thinking.
Offline

milosh

Elite 1K

Elite 1K

  • Posts: 1229
  • Joined: 27 Feb 2008, 23:40
  • Location: Serbia, Belgrade

Unread post07 Jan 2021, 14:07

madrat wrote:I can remember when internet guessing tried to assert the J-20 was merely 60 feet long. Clearly the guesses on weight are along the same wishful thinking.


This is why I don't use internet estimates which is +19tons for weight, that is why I used 20tons, it is higher then what even some serous sites estimated and more realistic.

21tons would be very close to MiG-31/Su-34 weight and it surely isn't there. Before someone wrote Su-34 is 22.5tons, it have 1ton of armor.

Btw if we just look plane length want you think how heavy F-23EMD would be with its 70'50":
https://web.archive.org/web/20150518200 ... 201500.gif
Offline

charlielima223

Elite 1K

Elite 1K

  • Posts: 1278
  • Joined: 12 Jan 2014, 19:26

Unread post07 Jan 2021, 20:09

milosh wrote:@charlielima223

I was talk about configuration, Su-57 is same configuration as F-22 or F-23 not canard and no ventral fins as J-20.

Canard configuration isn't good because canards are radar reflectors in case of J-20 huge one:
https://i.redd.it/pfw4j47mqik11.jpg

J-20 canards don't have platform alignment. So you have quite long surfaces which aren't angled as wings not good at all from stealth point of view:
https://geopolitics.news/wp-content/upl ... -00599.jpg

Radar blocker isn't something not used before in stealth design, F-23 would have one too, its intake bend is simply short to be efficient enough compared to F-22 or F-35. F-32 would have one too, and in case of F-32 engine is lot less hidden and bigger then in case of Su-57.

Also radar blocker in case of Su-57 is only used in subsonic flight, in supersonic one ramps hide engine without problem something which is overlooked:
https://fullafterburner.weebly.com/uplo ... n_orig.jpg



The J-20 and Su-57 are designed for different requirements. I would make a SWAG that China wanted a long range cruising aircraft with a balance of stealth and maneuverability. Russia on the other hand want just enough stealth but primarily focused on super-maneuverable aspects.

If you believe the canards on the J-20 are detrimental to stealth than the Su-57's movable LEVCONs are also detrimental to the aircraft stealth features.
Image
They are also of good size when compared to thr aircraft.
Further more the J-20's canards are planform aligned with its main wing structure
Image

As I pointed out earlier by comparing the two aircraft, the intake/inlet design of the Su-57 is NOTHING like the one seen on the YF-23. Here it is again incase you skipped over it.
YF-23
Image
Su-57
Image
From a head-on point of view the engine is slightly less visible than that of a Super Hornet
Image
Image
The J-20's air intake looks very similar to that of the F-35.
Image
Image

Again, the YF-23's intake design is more curved and the engine is buried deeper in the airframe. From a purely head-on view, the difference between the two are obvious. Pointing to the X-32 as an example that a radar blocking device with a short intake is a good radar reflective reducing measure when compared to the F-35's combined DSI and complex intake is a poor example. The X-32 lost the JSF competition incase you forgot. I dont believe it was all purely on looks and STOVL/VTOL perfomances during the experimental/prototyping phase.

Nice try by the way using a CGI of the aircraft of a speculated design implementation that has never been confirmed.

So NO, the Su-57 DOES NOT take any design cues from F-22 or YF-23. While there are universal radar reducing design features seen on the Su-57 (planform alignment, IWBs, blended surfaces etc), it is it's own design and has nothing that is visually in common with either China's J-20 or anything the US currently has.
Offline

sprstdlyscottsmn

Elite 4K

Elite 4K

  • Posts: 4979
  • Joined: 10 Mar 2006, 01:24
  • Location: Nashua NH USA

Unread post07 Jan 2021, 20:35

milosh wrote:This is why I don't use internet estimates which is +19tons for weight, that is why I used 20tons, it is higher then what even some serous sites estimated and more realistic.

If you compare the top view of the F-22 to the J-20, and move the F-22 tails up to a canard position (to mimic the arrangement of the J-20) you see that the fuselage of the J-20 is colossal compared to the F-22 while the wing sizes are largely similar. The F-22 weighs 22 US tons, 20 metric tons. How do you propose the larger aircraft of similar design is not going to be 21-22 metric tons empty?
"Spurts"

-Pilot
-Aerospace Engineer
-Army Medic
-FMS Systems Engineer
-PFD Systems Engineer
-PATRIOT Systems Engineer
Offline

milosh

Elite 1K

Elite 1K

  • Posts: 1229
  • Joined: 27 Feb 2008, 23:40
  • Location: Serbia, Belgrade

Unread post07 Jan 2021, 20:52

sprstdlyscottsmn wrote:
milosh wrote:This is why I don't use internet estimates which is +19tons for weight, that is why I used 20tons, it is higher then what even some serous sites estimated and more realistic.

If you compare the top view of the F-22 to the J-20, and move the F-22 tails up to a canard position (to mimic the arrangement of the J-20) you see that the fuselage of the J-20 is colossal compared to the F-22 while the wing sizes are largely similar. The F-22 weighs 22 US tons, 20 metric tons. How do you propose the larger aircraft of similar design is not going to be 21-22 metric tons empty?


Because not everything is clear from outside, you can't judge plane based purely on dimensions and shape, for example F-22 have this inside:
Image

J-20 have this:
Image

See some noticeable difference? And do you think it doesn't impact weight noticable?

Second example is F-23EMD, NG was marketing it not noticable heavier then YF-23 but it was longer airframe and not demostrator.

So how they plan to do that? Using much higher % of composites.

So materials are surely different then in case of F-22, in fact if you look F-35 and Su-57 (we have data for both) both birds using more composites then F-22 and interestingly more aluminium, titanium is something Russians have a lot but still they use less Ti compared to Su-35 to reduce Su-57 weight.

And then we have Su-34 and MiG-31 which are 21-22tons, so I really don't buy idea J-20 is something like 21-22tons just because F-22 is 20tons.

@charlielima223


I never wrote Su-57 intake is same as F-23 it isn't what I wrote F-23 would need radar blocker to hide engine compared to F-22, and I think some kind of blocker was mentioned on yf-23.net

Su-57 CGI picture of intake ramps was done based on drawings, reason why Su-57 have quite strange intake mouth is integration of ramp and intake to hide engine from radar in supersonic flight.

Moving Levcon and canards are totally different control surfaces, and Su-57 doesn't need to use levcon movement at all it could still fly without problem, J-20 without canards not so much. Also levcon movement is nowhere near big as in case of canards.
Offline

jessmo112

Senior member

Senior member

  • Posts: 335
  • Joined: 16 Mar 2020, 02:09

Unread post07 Jan 2021, 21:09

milosh wrote:
sprstdlyscottsmn wrote:
milosh wrote:This is why I don't use internet estimates which is +19tons for weight, that is why I used 20tons, it is higher then what even some serous sites estimated and more realistic.

If you compare the top view of the F-22 to the J-20, and move the F-22 tails up to a canard position (to mimic the arrangement of the J-20) you see that the fuselage of the J-20 is colossal compared to the F-22 while the wing sizes are largely similar. The F-22 weighs 22 US tons, 20 metric tons. How do you propose the larger aircraft of similar design is not going to be 21-22 metric tons empty?


Because not everything is clear from outside, you can't judge plane based purely on dimensions and shape, for example F-22 have this inside:
Image

J-20 have this:
Image

See some noticeable difference? And do you think it doesn't impact weight noticable?

Second example is F-23EMD, NG was marketing it not noticable heavier then YF-23 but it was longer airframe and not demostrator.

So how they plan to do that? Using much higher % of composites.

So materials are surely different then in case of F-22, in fact if you look F-35 and Su-57 (we have data for both) both birds using more composites then F-22 and interestingly more aluminium, titanium is something Russians have a lot but still they use less Ti compared to Su-35 to reduce Su-57 weight.

And then we have Su-34 and MiG-31 which are 21-22tons, so I really don't buy idea J-20 is something like 21-22tons just because F-22 is 20tons.

@charlielima223


I never wrote Su-57 intake is same as F-23 it isn't what I wrote F-23 would need radar blocker to hide engine compared to F-22, and I think some kind of blocker was mentioned on yf-23.net

Su-57 CGI picture of intake ramps was done based on drawings, reason why Su-57 have quite strange intake mouth is integration of ramp and intake to hide engine from radar in supersonic flight.

Moving Levcon and canards are totally different control surfaces, and Su-57 doesn't need to use levcon movement at all it could still fly without problem, J-20 without canards not so much. Also levcon movement is nowhere near big as in case of canards.


Is see so the plane is noticeably larger than a F-35 or F-22 yet lighter than both?!
Offline

milosh

Elite 1K

Elite 1K

  • Posts: 1229
  • Joined: 27 Feb 2008, 23:40
  • Location: Serbia, Belgrade

Unread post07 Jan 2021, 21:17

jessmo112 wrote:Is see so the plane is noticeably larger than a F-35 or F-22 yet lighter than both?!


Lighter then F-35?!? Where did I wrote that?

What I point out in comparison, if you have two big engines of course you have more thrust reserve then in case of one engine fighter even though it have more powerful engine.

F-22 have heavy flat nozzle system which weight a lot and not so high % of composite compared to other stealths. And J-20 isn't really that bigger then F-22 at least not bigger as early estimates were, it was like 1/3 longer.

In fact J-20 is shorter then F-23EMD and have smaller surface.
Offline

weasel1962

Elite 2K

Elite 2K

  • Posts: 2465
  • Joined: 07 Jun 2012, 02:41
  • Location: Singapore

Unread post08 Jan 2021, 05:07

The F119 & AL31F engine weights aren't that different (1.8 vs 1.6 tons) which is ~400kg for 2 or under 1000 lbs.

jessmo112 wrote:Is see so the plane is noticeably larger than a F-35 or F-22 yet lighter than both?!


Other than material weight, the aircraft weight is mainly determined by volume which is LxBXH. If the LxB is larger by virtue of the wing area, that means H is fairly small. The J-20 having 2 engines would likely be volume larger than the F-35 but less clear vis the F-22.

Looks can be deceptive. For example, that is a widespread assumption that the J-20 is bigger than the Flanker (LxB wise) but in reality, it isn't.
Offline

milosh

Elite 1K

Elite 1K

  • Posts: 1229
  • Joined: 27 Feb 2008, 23:40
  • Location: Serbia, Belgrade

Unread post08 Jan 2021, 08:58

weasel1962 wrote:The F119 & AL31F engine weights aren't that different (1.8 vs 1.6 tons) which is ~400kg for 2 or under 1000 lbs.


F119 weight is without massive flat nozzle system.

Btw F119 would have better thrust with round nozzle, close to 40k lbs class. But because of stealth they decide to go with flat nozzle which weight "a ton" and impact thrust.

download/file.php?id=873&mode=view
https://media.defense.gov/2007/Oct/10/2 ... 4S-008.JPG
Offline

mixelflick

Elite 4K

Elite 4K

  • Posts: 4248
  • Joined: 20 Mar 2010, 10:26
  • Location: Parts Unknown

Unread post08 Jan 2021, 16:42

OK Milosh, let's say you're an engineer who's tasked with building the ultimate air to air machine..

Do you use a flat nozzel, incur the weight penalty but preserve maximal stealth? Or do you go with a round engine nozzel, trying to eek out additional thrust and compromise on the stealth thing?

BTW, I think your assumption that the F-119 isn't a 40,000lb class engine may not be correct. In all fairness, none of us knows. But really, even if it doesn't have that extra thrust it still has an absurd thrust to weight ratio and more power than the pilots know what to do with (their words, not mine). So thrust isn't an issue with the F-22.

The SU-57 may ultimately have more powerful engines, in part due to round nozzel design. But it just as easily may not, and sacrificing its stealth qualities will most likely mean it gets spotted, shot at and killed first. That really is the crux of it. If I'm flying the SU-57, I'd much rather have a better (lower) RCS vs. a few extra thousand pounds of thrust.

It's a big sky out there, and not knowing where the F-22 is (even if its T2W ratio is .5/1) would be very, very concerning to me..
PreviousNext

Return to Modern Military Aircraft

Who is online

Users browsing this forum: No registered users and 4 guests