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Author Topic: Chengdu J-20 news, pictures, analysis Part III  (Read 49900 times)

Offline Ainen

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #150 on: February 14, 2018, 05:47:52 am »
Smith thinks the particular configuration - the delta- allows more fuel and a  broad  under fuselage  gives  a longer weapons bay.
But it's Bay is as long as it's necessary to comfortably fit current bwr missiles(pl-15).
Heavy usage of dtop tanks(as well as proliferation of Flanker family) sujests what internal range isn't that great either.

Offline duker

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #151 on: February 14, 2018, 11:41:56 am »
I dont think Ive seen a photo of the J-20 with drop tanks ?

And this  comparison image  of the J-20 with Su-27 , Pak-FA and F-22 shows its a bigger plane than the F-22, and along with  commentary of the design expert I mentioned, supports the  large  internal fuel.

https://i1.wp.com/fightersweep.com/wp-content/uploads/2016/09/size-chart.jpg?resize=1024%2C516&ssl=1

Offline sferrin

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #152 on: February 14, 2018, 11:56:40 am »
I dont think Ive seen a photo of the J-20 with drop tanks ?

See page 2 of this topic.
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Offline kcran567

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #153 on: February 14, 2018, 01:36:07 pm »
Have seen the pictures months ago and pondering them...seems like the Chinese want "Global self-deployment" capability. J-20 can Ferry itself anywhere without a refuel? Range and fuel fraction alone clean is probably higher than any other 5th Gen machine out there.

Offline Blitzo

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #154 on: February 14, 2018, 07:57:50 pm »
I dont think Ive seen a photo of the J-20 with drop tanks ?

And this  comparison image  of the J-20 with Su-27 , Pak-FA and F-22 shows its a bigger plane than the F-22, and along with  commentary of the design expert I mentioned, supports the  large  internal fuel.

https://i1.wp.com/fightersweep.com/wp-content/uploads/2016/09/size-chart.jpg?resize=1024%2C516&ssl=1

That comparison image was one of the first made back when prototype 2001 came out and nobody knew how big it really was. In other words, that comparison is wrong.

This one from CSIS is much more accurate.


Offline Blitzo

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #155 on: February 14, 2018, 08:02:19 pm »
...
J-20 can carry four EFTs and I would be surprised if it ever carries them outside of Chinese airspace defended by IADS during a high end conflict.


In any case, I think between the YF-22 and YF-23, the latter's greater size and longer range would've made it more suitable for the pacific theatre that we see now.
...
To be fair, I am not even sure if unrefueled range of J-20 is that large to call it especially long-legged, heavy usage of EFTs for clearly non-frontline configuration sujests it can be actually not that large.
Otherwise, why so many? Addition of this capability doesn't come for free.


The further, the more it seems what J-20 is quite pure air superiority bird with only secondary a2g or anything else.

I'm not sure what you mean by "heavy usage of EFTs for clearly non-frontline configuration".

As you describe, four EFTs are obviously a non-frontline configuration, meaning the addition of those four EFTs is for other purposes, such as ferry in safe environments. There will obviously be situations where having four EFTs may be useful, and it makes sense to flight test that configuration.

Whether an aircraft is able to carry four or two EFTs or whatever I think should have no implication for what we estimate its internal fuel capacity is.

Offline Ainen

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #156 on: February 14, 2018, 11:27:31 pm »
Whether an aircraft is able to carry four or two EFTs or whatever I think should have no implication for what we estimate its internal fuel capacity is.
Ability to carry 4 fuel tanks requires additional complication of fuel system.
No one will do it without a proper reason. Even more so for a 5th generation fighter.

Simplest possible reason is a ferry range, of which they want really a lot(5500 was quoted by Xinhua).
Without these EFTs we just drop 8+t of fuel out of equation. Which basically is a full Raptor worth of fuel.

Offline totoro

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #157 on: February 15, 2018, 12:19:57 am »
F-22 is internally configured to carry up to four tanks. But in the end they never tested for four, only two.
F-35 is plumbed for two tanks, never tested though.
Su-35 same as above, two tanks, never tested.

Range is certainly something Chinese require as A) they gravely lack in air refueling capacity, and B) their operational requirements likely include ability to operate at first island chain line, meaning up to 450 nm away from coastline. If one wishes to operate from bases more inland, to protect them from enemy attacks, that may add further few hundred nm to range requirement.

I will repeat one of my older posts:
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.

So i don't believe it's implausible J-20 carries 35% more fuel than F-22 internally, if not more.  The four tanks seen would add to that. They seem to be sized pretty close to US 600 gallon tanks, so that would add another 7+ tons. Of course, actual range is hard to predict, fuel consumption may be somewhat worse than F-22.
 
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Offline sferrin

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #158 on: February 15, 2018, 05:13:12 am »
So i don't believe it's implausible J-20 carries 35% more fuel than F-22 internally, if not more.  The four tanks seen would add to that. They seem to be sized pretty close to US 600 gallon tanks, so that would add another 7+ tons. Of course, actual range is hard to predict, fuel consumption may be somewhat worse than F-22.

Just look at the difference in fuel load between the YF-22 and the F-22A, and they were pretty much the same size.
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Offline Ainen

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #159 on: February 15, 2018, 05:35:22 am »
So i don't believe it's implausible J-20 carries 35% more fuel than F-22 internally, if not more. 
Yes, I feel it to be like this too.Maybe a bit smaller.
Basically, it brings us to the typical 5th generation internal range window.
Raptor is just below it, because of changes between YF-22 and F-22A.


Offline Blitzo

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #160 on: February 18, 2018, 11:03:29 pm »
Whether an aircraft is able to carry four or two EFTs or whatever I think should have no implication for what we estimate its internal fuel capacity is.
Ability to carry 4 fuel tanks requires additional complication of fuel system.
No one will do it without a proper reason. Even more so for a 5th generation fighter.

Simplest possible reason is a ferry range, of which they want really a lot(5500 was quoted by Xinhua).
Without these EFTs we just drop 8+t of fuel out of equation. Which basically is a full Raptor worth of fuel.

Yes, of course the engineering and testing to allow an aircraft to carry four or two EFTs needs time, and money and effort.

However, that merely means the Air Force would've believed that it would have been worthwhile for the aircraft to have that ability. It does not convey to us on what the aircraft's internal fuel capacity/range is, nor does it tell us what the aircraft's internal+EFT fuel capacity/fuel range is.


In other words, we know the Air Force definitely has fuel and range requirements, both with and without EFTs, but the fact that they decided to allow the aircraft to carry four EFTs doesn't tell us what those requirements are.

Offline PaulMM (Overscan)

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #161 on: February 19, 2018, 12:05:38 am »
It may just mean they are short on tankers.
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Offline Ainen

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #162 on: February 19, 2018, 08:29:30 am »
In other words, we know the Air Force definitely has fuel and range requirements, both with and without EFTs, but the fact that they decided to allow the aircraft to carry four EFTs doesn't tell us what those requirements are.
It's the most logical explanation. AndI believe design of aircraft to be logical more often than not.  :)
There are too few reasons to do it on a stealth fighter this way apart from additional ferry range.
Otherwise internal fuel wins.

2Paul
You mean as a buddy tanker? While possible, sounds a bit wasteful on a non-naval 5th gen fighter.
« Last Edit: February 19, 2018, 08:31:03 am by Ainen »

Offline PaulMM (Overscan)

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #163 on: February 19, 2018, 11:20:29 am »
No - I mean, they may want it to be able to deploy long distances (China itself is kind of big) without relying on tanker support like the US does for its F-22s.
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Offline VTOLicious

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Re: Chengdu J-20 news, pictures, analysis Part III
« Reply #164 on: February 19, 2018, 11:32:24 am »
No - I mean, they may want it to be able to deploy long distances (China itself is kind of big) without relying on tanker support like the US does for its F-22s.

And J-20 doesn't feature in flight refueling so far...
http://chinesemilitaryreview.blogspot.co.at/2013/02/boom-tanker-in-flight-refueling-chinese.html?m=0