Chengdu J-20 5th Generation Aircraft News & Discussions

[Asoka]

Who he is is rather important here, as he's a liberal arts major with zero experience in either military or engineering. His observation of "enormous airframe and small wings" and "huge weapons bay" are incorrect, and any analyses drawn upon shaky foundations is of course pure crap, like all his articles are.

@antonius123 Let your eyes be the witnesses. Watch a few youtube videos and see how much maneuverability J-20 has.

The impression that long and slender strike fighter or interceptor are good at high speed, but poor in maneuverability was gained in the 1960's. They were built to intercept high speed bombers. They need but to fly straight toward the bombers and launch their missiles.

Modern 5th generation fighters have combined extreme maneuverability with high speed, including Supersonic Cruise. F-22 has extreme maneuverability at low and post-stall speed, but it is also built for high speed. It could cruise at Mach 1.6 for over 30 min. It could pull 5G maneuvers at Mach 1.6, at 30,000.

We don't know the J-20's flight envelope yet. But judging from the fact that J-20 has Differential Movable Canards, Delta-wings, Lifting Body, 8 sets of vortex generators, Leading Edge Extensions, All-moving tails, possibly TVC nozzles, J-20 will also extreme maneuverability as well.

The Movable Canards alone will give extreme maneuverability that is far better than anything in the 1960's. Look at the Typhoon, Rafael, J-10, and Gripen.

Long and slender shape means high speed. But that doesn't necessarily exclude extreme maneuverability. Modern AA missiles are long and slender. They could fly at Mach 3-4, and do 60G. That's because they have the wings called canards at the front, and vector thrust nozzle at the back. And a powerful rocket engine.

How would you like to dog fight an AA missile?

 

[Ultima Thule]

[

There are some indications that the J-20 is a primarily a strike aircraft but with a robust air-to-air capability. Like the American F-35, the newest J-20 prototypes appear to have an electro-optical targeting system mounted under the nose. That sensor could be Beijing A-Star Science and Technology’s EOTS-89 electro-optical targeting system (EOTS). A dedicated air superiority fighter wouldn’t need that kind of sensor.

its a stealth version of IRST

Perhaps the most compelling evidence that would point to the J-20 being optimized for the strike role is the fact that the airframe is enormous but has relatively small wings. It’s also seems to have huge weapons bays. While such a configuration works well for a fast supersonic strike aircraft, it’s not ideal for an air superiority fighter that needs be able to sustain high rates of turn.

CANARD DELTA is unstable relax negative stability which its have extreme agility and maneuverability

Simply put (for the designs you mention) - high speed maneuverability.


The US don't seem to like canards from the outside, but looking closer, they didn't design a new fighter for high speed maneuvering before TVC became a serious option.

This allowed them to prioritise radar shape on the F-22 (avoid the canard fuselage junction in the forward quadrant radar 'wetted' area) while using TVC to trim the aircraft for supersonic flight (giving them back good maneuvering capabilities).



There are a number of factors to consider over which is better, some of these are:

1. A canard generates upthrust when pitching nose up, while a traditional elevator generates a downthrust - thus a canard should allow for better sustained turning performance.

2. A canard can generate a little upthrust in steady level flight, allowing for a smaller wing - meaning less inertia & damping, thus better dynamic response rates (in pitch and roll).

3. A canard when pitching nose up will induce a downwash over the main wing, reducing its effectiveness, which conflicts with (1) and (2). Increasing the distance from canard to wing can help offset this (Eurofighter).

4. A canard can be used as a replacement for a LERX for high AoA flight, and its normally more efficient in cruise. Close coupling of canard and wing helps achieve this (Rafale).

5. With a canard, the main wing can be placed further back, hence the c.g of the aircraft is further back, hence the gear is further back, hence more aggressive rotation angles can be used for take-off. The canard also is better at inducing rotation than a tailplane.

6. A canard requires a junction between wing and fuselage - this junction is harder to hide on radar. Its preferred to hide this behind the main wing on an elevator (like the F-22).

Before addressing the pros and cons of the canard delta with any other configuration, you must understand the reason for the canard in the first place.

A tailless delta wing, when increasing angle of attack (in manoeuvring flight - ie:- turning) must generate a downward force aft of the CG. To do this the elevons must be deflected upwards (which in the case of slow speed flight is the opposite of lowering flaps), and this results in an overall loss of lift from the wing (meaning that to remain level in a turn even more AoA is required). Therefore the tailless delta is at a disadvantage in manoeuvring flight with regard to other configurations. In the slow speed regime, you can see that if a tailless delta were to deploy flaps, they would act is exactly the opposite way to the elevons which would be deflected upward - and this would look exactly like a split trailing edge speedbrake! Hence the lack of flaps on tailless deltas, and a resulting high landing speed (Do you see why there have been no delta shipboard aircraft?)

By adding a conventional tailplane (and elevators) ala MiG-21, the tail can produce the downward force to increase the angle of attack while the wing produces more lift and can also be fitted with flaps to increase the lift of the wing in slow speed flight.

The use of a canard instead of a conventional tail (on both a delta and any other wing configuration) is to provide the pitching moment by an upward force (lift) ahead of the CG rather than a downward force aft of the CG resulting in an overall increase in lift greater than provided by the conventional tail (downward force at the tail=loss of lift which must be subtracted from the increase in lift generated by the wing due to its increased angle of attack). The greater the increase in lift with change of angle of attack vs the increased drag that results, then the better the aircraft will be able to maintain energy in a turn.

The 'downside' of placing the pitch control forward of the wing, is that the airflow over the canard which can disturb the airflow over the wing. Careful design has minimised the harmful effects (which obviously change throughout the flight envelope) and in certain parts of the envelope (especially very high angles of attack) the airflow and vortices off the canard and how they affect the wing have been used to advantage to maintain lift from the wing at angles of attack that would normally result in a stall.

That the US has not gone down that road, has really been that the US never embraced the delta in the first place - with the exception of the F-102 / F-106 tailless delta interceptors. However, of late, the US has become interested in the subject (at least from a research perspective) with the X-31, which then continued into the realm of all axis control by thrust vectoring.

The US did test canard surfaces (retaining a conventional tail as well) on the F-4 Phantom and the F-15 Eagle.
http://www.abovetopsecret.com/forum/thread312810/pg1
so you see J-20 is basically a air superiority fighter

What I mean is : if there is no evidence about existence (of J-23/J-25 or any other "J=" of Chinese black project) doesn't mean it is non existence. Except the officials have said so (that china is not doing any other stealth fighter development other than J-20 and J-31).

no one knows 6th gen jets are in initial phase of development they are nameless how do you know there names that they are J-23/J-25 just in your baseless imaginations and assumptionsand as for your information those are if they exist are above top-secret

 

[Asoka]

[


its a stealth version of IRST


CANARD DELTA is unstable relax negative stability which its have extreme agility and maneuverability

Simply put (for the designs you mention) - high speed maneuverability.


The US don't seem to like canards from the outside, but looking closer, they didn't design a new fighter for high speed maneuvering before TVC became a serious option.

This allowed them to prioritise radar shape on the F-22 (avoid the canard fuselage junction in the forward quadrant radar 'wetted' area) while using TVC to trim the aircraft for supersonic flight (giving them back good maneuvering capabilities).



There are a number of factors to consider over which is better, some of these are:

1. A canard generates upthrust when pitching nose up, while a traditional elevator generates a downthrust - thus a canard should allow for better sustained turning performance.

2. A canard can generate a little upthrust in steady level flight, allowing for a smaller wing - meaning less inertia & damping, thus better dynamic response rates (in pitch and roll).

3. A canard when pitching nose up will induce a downwash over the main wing, reducing its effectiveness, which conflicts with (1) and (2). Increasing the distance from canard to wing can help offset this (Eurofighter).

4. A canard can be used as a replacement for a LERX for high AoA flight, and its normally more efficient in cruise. Close coupling of canard and wing helps achieve this (Rafale).

5. With a canard, the main wing can be placed further back, hence the c.g of the aircraft is further back, hence the gear is further back, hence more aggressive rotation angles can be used for take-off. The canard also is better at inducing rotation than a tailplane.

6. A canard requires a junction between wing and fuselage - this junction is harder to hide on radar. Its preferred to hide this behind the main wing on an elevator (like the F-22).

Before addressing the pros and cons of the canard delta with any other configuration, you must understand the reason for the canard in the first place.

A tailless delta wing, when increasing angle of attack (in manoeuvring flight - ie:- turning) must generate a downward force aft of the CG. To do this the elevons must be deflected upwards (which in the case of slow speed flight is the opposite of lowering flaps), and this results in an overall loss of lift from the wing (meaning that to remain level in a turn even more AoA is required). Therefore the tailless delta is at a disadvantage in manoeuvring flight with regard to other configurations. In the slow speed regime, you can see that if a tailless delta were to deploy flaps, they would act is exactly the opposite way to the elevons which would be deflected upward - and this would look exactly like a split trailing edge speedbrake! Hence the lack of flaps on tailless deltas, and a resulting high landing speed (Do you see why there have been no delta shipboard aircraft?)

By adding a conventional tailplane (and elevators) ala MiG-21, the tail can produce the downward force to increase the angle of attack while the wing produces more lift and can also be fitted with flaps to increase the lift of the wing in slow speed flight.

The use of a canard instead of a conventional tail (on both a delta and any other wing configuration) is to provide the pitching moment by an upward force (lift) ahead of the CG rather than a downward force aft of the CG resulting in an overall increase in lift greater than provided by the conventional tail (downward force at the tail=loss of lift which must be subtracted from the increase in lift generated by the wing due to its increased angle of attack). The greater the increase in lift with change of angle of attack vs the increased drag that results, then the better the aircraft will be able to maintain energy in a turn.

The 'downside' of placing the pitch control forward of the wing, is that the airflow over the canard which can disturb the airflow over the wing. Careful design has minimised the harmful effects (which obviously change throughout the flight envelope) and in certain parts of the envelope (especially very high angles of attack) the airflow and vortices off the canard and how they affect the wing have been used to advantage to maintain lift from the wing at angles of attack that would normally result in a stall.

That the US has not gone down that road, has really been that the US never embraced the delta in the first place - with the exception of the F-102 / F-106 tailless delta interceptors. However, of late, the US has become interested in the subject (at least from a research perspective) with the X-31, which then continued into the realm of all axis control by thrust vectoring.

The US did test canard surfaces (retaining a conventional tail as well) on the F-4 Phantom and the F-15 Eagle.
http://www.abovetopsecret.com/forum/thread312810/pg1
so you see J-20 is basically a air superiority fighter



no one knows 6th gen jets are in initial phase of development they are nameless how do you know there names that they are J-23/J-25 just in your baseless imaginations and assumptionsand as for your information those are if they exist are above top-secret

Nice explanation. But please be easy with the colors and font size.

Too many fanboys, influenced by know nothing and highly biased journalists and think tankers, think China put a canards on J-20 just for the sake of INCREASE the RCS. They don't know what canards are for, and they claim J-20 has no maneuverability, because its only a large striker/interceptor.

 

[Deino]

Well thanks. But I myself is more interested with the content of the analysis rather than who he is

What I mean is : if there is no evidence about existence (of J-23/J-25 or any other "J=" of Chinese black project) doesn't mean it is non existence. Except the officials have said so (that china is not doing any other stealth fighter development other than J-20 and J-31).

Without evidence, both who claim existence or non existence are same speculating.

Oh come on ! that's the same stupid argument we have to read here much too often: Since I cannot prove the J-20 uses NO WS-15, it surely has one; since I cannot prove it cannot fly Mach 3 it surely can ... since I have no evidence that there are green men on Mars there must be some. Come on; is this the level You want to argue?

My point is simply the there are a few guys out there in the Western media like Nationalinterest, like Kanwa, like WarIs Boring represented by such guys like Dave Majumdar, who are - to say it politely - not very much interested in facts but more in feelings. But if You want to believe him it's up to You ...

Deino

 

[Asoka]

Oh come on ! that's the same stupid argument we have to read here much too often: Since I cannot prove the J-20 uses NO WS-15, it surely has one; since I cannot prove it cannot fly Mach 3 it surely can ... since I have no evidence that there are green men on Mars there must be some. Come on; is this the level You want to argue?

My point is simply the there are a few guys out there in the Western media like Nationalinterest, like Kanwa, like WarIs Boring represented by such guys like Dave Majumdar, who are - to say it politely - not very much interested in facts but more in feelings. But if You want to believe him it's up to You ...

Deino

"Since I cannot prove the J-20 uses NO WS-15, it surely has one; "

You have twisted my argument, Deino. There is no evidence that excludes the possibility that WS-15 is on J-20 already.

But there is evidence that could exclude the possibility J-20 is using WS-10 or AL-31F, because these two engines do not provide enough Dry Thrust for J-20 to do vertical climbing and Supersonic Cruising.

So we must leave that possibility that WS-15 is on J-20, open.

 

[Deino]

I still disagree with You, but that's not the point.

My point was simply that in science You cannot prove anything by the absence of a prof for the contrary ! That's plain wrong, ridiculous ... in fact even stupid.

But I would beg to come back to the topic, this discussion - and also size and colour of the post - has become a bit too much off !

Deino

 

[grey boy 2]

Found a couple of HD pictures, not sure it has been posted before

 

[Ultima Thule]

You have twisted my argument, Deino. There is no evidence that excludes the possibility that WS-15 is on J-20 already.

but not final version, lots of parts in this interim version of WS-15 is using from WS-10 series of engines as @ChineseTiger1986 says

 

[nang2]

I still disagree with You, but that's not the point.

My point was simply that in science You cannot prove anything by the absence of a prof for the contrary ! That's plain wrong, ridiculous ... in fact even stupid.

But I would beg to come back to the topic, this discussion - and also size and colour of the post - has become a bit too much off !

Deino

haha, absence of evidence vs evidence of absence.

 

[Asoka]

I still disagree with You, but that's not the point.

My point was simply that in science You cannot prove anything by the absence of a prof for the contrary ! That's plain wrong, ridiculous ... in fact even stupid.

But I would beg to come back to the topic, this discussion - and also size and colour of the post - has become a bit too much off !

Deino

There is Absence of Proof (or no proof) that something is Impossible, and then there is Proof that something is plainly Impossible.

1.) It is plainly impossible for WS-10X or AL-31FN to lift J-20 vertically, using Dry Thrust alone.
(Their Dry Thrust is only around 8.6 tons (60% of 140kN or 14.29 tons). 2 x 8.6 = 17.2 tons, less than the empty weight of Su-30MKI, 18.4 tons).

2.) And there is no proof that it is Impossible for WS-15 to be already installed on J-20. So we can speculate that the engine could be WS-15.

3.) I have to admit that I have no direct proof that J-20's engine is WS-15. I have no confirmed picture, no official announcements for that effect. Other than we know WS-15 exists and it is intended for J-20.

4.) Since WS-10x and AL-31FN got ruled out (by the vertical climb demonstration), I simply assume J-20's engine must be the mysterious WS-15, because there is no other engines available.

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." -- Sherlock Holmes.

but not final version, lots of parts in this interim version of WS-15 is using from WS-10 series of engines as @ChineseTiger1986 says

Yes, there is still room to speculate which version of WS-15 is on J-20 right now, the prototype (with parts from WS-10) or production type.

But there is no possibility that WS-10X or AL-31FN could lift J-20 vertically with Dry Thrust only.

NO POSSIBILITY. ZERO. NONE. ZIP.

haha, absence of evidence vs evidence of absence.

or Absence of Evidence of Impossibility vs Evidence of Impossibility.

 

[Ultima Thule]

Yes, there is still room to speculate which version of WS-15 is on J-20 right now, the prototype (with parts from WS-10) or production type.

But there is no possibility that WS-10X or AL-31FN could lift J-20 vertically with Dry Thrust only.

NO POSSIBILITY. ZERO. NONE. ZIP.

But J-20 using interim version of WS-15 not final version with a parts from WS-10 series of engine as @ChineseTiger1986 said

 

[Asoka]

There is some people noticed that starting prototype 2012, the J-20 looks different around the engine area.

The gap between the engines is now deeper and the engine compartment is shorter. They speculate that it is because the production version of WS-15 is shorter and smaller, than the interim version. The WS-15's compressor has only 3 stages, vs 5 stages for the WS-10.

I don't know this is true. It is simply speculation.

 

[Ultima Thule]

Well, I assume the engine core is the WS-15, with some parts from WS-10. The engine core determines the thrust performance. If you got a more powerful core, you have got a new engine.

What about higher thrust and special variant of WS-10 with thrust 155 Kn-160 Kn for J-20

The gap between the engines is now deeper and the engine compartment is shorter. They speculate that it is because the production version of WS-15 is shorter and smaller, than the interim version. The WS-15's compressor has only 3 stages, vs 5 stages for the WS-10.

if it had WS-15 it is not a final and production version of WS-15

 

[Asoka]

What about higher thrust and special variant of WS-10 with thrust 155 Kn-160 Kn for J-20


if it had WS-15 it is not a final and production version of WS-15

"155 kN-160 kN" is still not high enough. And there is no variant of WS-10 with thrust > 140kN.

If we assume J-20 is two tons heavier than F-22 (19.7 tons) and it carries 3 tons of fuels for demonstration (total 25 tons), then the minimum thrust required is > 200kN.

"if it had WS-15 it is not a final and production version of WS-15"
I am not worry about this. The engineers still have time to get WS-15 right, before mass production. It is still LRIP.

I assume, the production version of WS-15 is in the advance stage of testing already. Otherwise, it is behind the J-20's entering service date of 2017-2019, as planned.

The J-20 prototypes that are numbered 2001-2017 are all testing planes. It is not too much a leap of faith to believe that they could be used to test WS-15, interim version or production version.

This is the main difference I have with other PDF members. They have categorically rejected the possibility that at least the interim version of WS-15 is already tested on J-20.

They still believe only the WS-10x or AL-31FN could be running on J-20.

I fully understand that the lack of official announcements on the status of WS-15 has a lot to do with our feverish speculations.

 

[Ultima Thule]

If we assume J-20 is two tons heavier than F-22 (19.7 tons) and it carries 3 tons of fuels for demonstration (total 25 tons), then the minimum thrust required is > 200kN.

oh that is over capability for J-20 various site state that WS-15 have a thrust of 18 to 19 tons which it will slightly inferior or same thrust as F-135

If we assume J-20 is two tons heavier than F-22 (19.7 tons) and it carries 3 tons of fuels for demonstration (total 25 tons), then the minimum thrust required is > 200kN.

oh that is over capability for J-20 various site state that WS-15 have a thrust of 18 to 19 tons which it will slightly inferior or same thrust as F-135