Chengdu J-20 5th Generation Aircraft News & Discussions

[Fsjal]

All this talk about which plane is stealthier and not much of a mention of the YF-23 or the planned X-44 MANTA.

 

[Su33KUB]

Come on, there's tons of reason how each of fifth generation fighter layout designed, but overall I pretty sure that has something to do with each nations AF strategic needs or doctrines such as American that place priority on full spectrum stealth, but of course different perspectives for China and Russia. So my point was to debated all stealth characteristic of J-20 and F-22 was pointless since their created based on different standard. From my point of view, J-20 for China was first step plus minus, build J-20 mean for China can gained a lot thing of stealth characteristics, beside J-20 still has plenty room for improvement. And don't forget China's 6th generation still on waiting list.

the main issue for China, Japan or Russia at this moment is they lack operational engines as powerful as F119 or F135, both Su-57 and J-20 do not have full aspect stealth because 2D nozzles reduce thrust and add weight, less thrust means drag has a higher impact, the Japanese for example still are developing the XF9 engine which still is not better than 117S that powers Su-57, Su-57 may fit a 2D nozzles like F-22, but at the moment are regular axisymmetric nozzles in both 117S and T-30 engines.

In the case of F-35, flat 2D nozzles like those on F-22 means lower thrust and added weight, basically putting too much strain on the TWR of F-35, J-31 well has old RD-93 of very low power yield for a 5th generation aircraft.

This design constraint is behind some of the less stealthy features of J-20, in order to achieve higher STR, you need higher thrust, and in order to have maximum lift, canards were added, the wing canard interaction assures higher lift than with aft planes; the ventral fins are basically for high AoA regimes, because the J-20 fuselage can blank the dorsal all moving vertical fins and render them useless by the turbulent wake, so its ventral fins are not in the wake of turbulence assuring controllability at high AoA, the F-22 has taller and higher dorsal vertical fins but adds controllability by the use of Thrust vectoring control nozzles for pitch control and roll control by aft tails, but in order to have full aspect stealth and thrust vectoring control they have very powerful engines.

Then F-22 does not need ventral fins, Su-57 with 3D thrust vectoring nozzles well does not need ventral fins either.

J-20 future variants might change that once that have an engine powerful enough to add 2D flat nozzles and even a tailless design

 

[antonius123]

In what way am I 'exaggerating' and exaggerating what?

My point was that the F-22's classic intakes with their diverter plates are irrelevant at some aspects but the J-20's canards are available at all aspects.

How?

How do you know canards contribute more rcs compared to classic intake with mechanical diverter?

 

[ZeEa5KPul]

How?

How do you know canards contribute more rcs compared to classic intake with mechanical diverter?

He doesn't. He's a know-nothing janitor with delusions of being an aeronautical engineer/pilot who should be booted from here like he was booted from SDF. As you've undoubtedly noticed, you'll get nothing but canned nonsense from him if you ask him anything outside janitorial lines. I'm being generous in assuming he can answer janitorial questions cogently, but it's a wholly unwarranted assumption.

 

[Figaro]

the main issue for China, Japan or Russia at this moment is they lack operational engines as powerful as F119 or F135, both Su-57 and J-20 do not have full aspect stealth because 2D nozzles reduce thrust and add weight, less thrust means drag has a higher impact, the Japanese for example still are developing the XF9 engine which still is not better than 117S that power Su-57, Su-57 may fit a 2D nozzles like F-22, but at the moment are regular axisymmetric nozzles in both 117S and T-30 engines.

In the case of F-35, flat 2D nozzles like those on F-22 means lower thrust and added weight, basically putting too much strain on the TWR of F-35, J-31 well has old RD-93 of very low power yield for a 5th generation aircraft.

This design constraint is behind some of the less stealthy features of J-20, in order to achieve higher STR, you need higher thrust, and in order to have maximum lift, canards were added, the wing canard interaction assures higher lift than with aft planes; the ventral fins are basically for high AoA regimes, because the J-20 fuselage can blank them and render them useless by the turbulent wake, so its ventral fins are not in the wake of turbulence assuring controllability at high AoA, the F-22 has taller and higher dorsal vertical fins but adds controllability by the use of Thrust vectoring control nozzles for pitch control and roll control by aft tails, but in order to have full aspect stealth and thrust vectoring control they have very powerful engines.

Then F-22 does not need ventral fins, Su-57 with 3D thrust vectoring nozzles well does not need ventral fins either.

J-20 future variants might change that once that have an engine powerful enough to add 2D flat nozzles and even a tailless design

How?

How do you know canards contribute more rcs compared to classic intake with mechanical diverter?

Can we stop arguing about this pointless topic? Clearly we are going in circles. This thread should consist of J-20 pictures, updates, and developments instead of a bunch of arguments based on conjecture.

No HMD, I guess...

There was a picture of the J-20 HMD picture taken this year or last year ... google it. Normally, there is only footage of the pilots in these light, non-HMD helmets.

 

[Fsjal]

"both Su-57 and J-20 do not have full aspect stealth because 2D nozzles reduce thrust and add weight, less thrust means drag has a higher impact...

...flat 2D nozzles like those on F-22 means lower thrust and added weight..."

Stealth-wise, 2D rectangular thrust nozzles have better stealth properties than 3D circular thrust nozzles. While the latter can swivel in any direction and is lighter, the former reflects radar waves in well-defined directions rather than scattering them everywhere. However, no thrust-vectoring and instead just fixed heat-ablating nozzle exhaust like YF-23 is the most superior for extremely-low stealth, but Chengdu picked circular nozzle for J-20 for lower weight and higher maneuverability, even F-35's F135 engine uses circular nozzle for similar reasons.

 

[Su33KUB]

"both Su-57 and J-20 do not have full aspect stealth because 2D nozzles reduce thrust and add weight, less thrust means drag has a higher impact...

...flat 2D nozzles like those on F-22 means lower thrust and added weight..."

Stealth-wise, 2D rectangular thrust nozzles have better stealth properties than 3D circular thrust nozzles. While the latter can swivel in any direction and is lighter, the former reflects radar waves in well-defined directions rather than scattering them everywhere. However, no thrust-vectoring and instead just fixed heat-ablating nozzle exhaust like YF-23 is the most superior for extremely-low stealth, but Chengdu picked circular nozzle for J-20 for lower weight and higher maneuverability, even F-35's F135 engine uses circular nozzle for similar reasons.

in general most aircraft are designed with on design parameters and off design features, aircraft like F-117 have the ideal low IR, low RCS nozzles, disadvantage they cool and lower the pressure of the jet engine that the jet engines lose thrust, stealth not always goes well with aerodynamics in fact the Su-27 forebody is the ideal for low drag, basically its radome is a missile type forebody, but it is not good for stealth, J-20 has a better fuselage for stealth but creates more drag, so all technologies have pros and cons, in reality J-20 will need to know the rivals on design features to find the off design disadvantages, here is where tactics become relevant, it is not that any aircraft is the best in everything, that only exist in the mind of fans, in reality a fighter pilot has to find the advantages of his aircraft against its rival, to give you an example, most fighter aircraft during the cold war did not use weapons bays because they increase weight and size, semi-recessed weapons were the lowest drag possible in example Tornado or F-14, but that is not good for stealth, this forces J-20 to have a very powerful engine, let us remember it has a substantially larger fuselage than other stealth aircraft, i read a few days ago a Russian article that says chinese TV said they plan to make 36 J-20s a year, and one of the production lines will have Al-31s powered J-20 and other WS-15, but the fact is without a good engine is hard to make an equivalent to F-22.

The fifth-generation Chinese fighter J-20 will be produced at a speed of at least 36 units per year, CCTV reported on October 1.
According to the channel, at the moment, three assembly lines for J-20 fighter jets are being equipped at enterprises in the military-industrial complex of China.

It is specified that two lines are designed for the production of a fighter with Russian AL-31F engines, and one for the production of aircraft with a Chinese-made WS-15 engine.

Chinese media say that the capacity of each of these lines makes it possible to produce one fighter per month, and in just a year it will be possible to assemble 36 aircraft of this type.

https://regnum.ru/news/2735501.html

 

[Su33KUB]

To understand why F-117 type nozzles are not used on J-20 we need to know that this type of nozzles reduced the thrust of each engine of F-117 from 10540 lb to 9040lb, so it has a very low IR and RCS but it losses almost 1500lb of thrust in each engine around 3000 lb of thrust in total

J-20 does not have extra engine power to have lower IR and RCS

source
https://books.google.co.jp/books?id=WaedCwAAQBAJ&pg=PA31&lpg=PA31&dq=f-117+nozzle+reduced+thrust&source=bl&ots=fJVKZsyNEo&sig=ACfU3U2Rtx_iC4tKZfFy1P0i2Glfw5cqaw&hl=en&sa=X&ved=2ahUKEwiy4JH7mIblAhWEy4sBHTAFC5Q4ChDoATABegQIBhAB#v=onepage&q=f-117 nozzle reduced thrust&f=false

. The major performance penalties associated with incorporation of IR suppressors are discussed below: (a) Additional weight of IR suppressor: The IRSS systems prior to BHO included moving parts like blowers. The BHO does not have moving parts, and is lighter by 180 kg over prior systems [106]. Most passive IR suppressors for helicopters (based on optical blocking and mixing of exhaust gases with ambient) [4,117] add to the weight, as illustrated in Table 4. (b) Power loss due to bleeding of air and modification of exhaust geometry that increases engine backpressure: Most IR suppressors need airflow to cool heated parts or ejector passages for sucking ambient air, resulting in reduced engine thrust


Infrared signature studies of aerospace vehicles Shripad P. Mahulikar, Hemant R. Sonawane, G. Arvind Rao Department of Aerospace Engineering, Indian Institute of Technology—Bombay, P.O. IIT Powai, Mumbai 400076, India

 

[yantong1980]

Can we stop arguing about this pointless topic? Clearly we are going in circles. This thread should consist of J-20 pictures, updates, and developments instead of a bunch of arguments based on conjecture.


There was a picture of the J-20 HMD picture taken this year or last year ... google it. Normally, there is only footage of the pilots in these light, non-HMD helmets.

Agree

 

[gambit]

...to give you an example, most fighter aircraft during the cold war did not use weapons bays because they increase weight and size,...

When I was active duty and assigned to the F-111, the jet have a weapons bay but it was hardly ever used. In fact, the F-111's weapons bay became a cargo bay for deployment. We packed personal items to souvenirs.

Anway...One negative aspect of having a weapons bay is that it limits the type of ordnance you can carry, which limits upgrades. In other words, a weapons bay design will either limit flexibility or even lock the aircraft into what type of mission it can fly.

The advent of low radar observability or 'stealth' compelled the return of an internal weapons bay design, and yes, it does force the airframe's design to have a higher mass/weight and internal volume. In flight, aircraft performance is influenced by aerodynamics, which includes drag, and weight. Expendable weight like fuel, in internal and external tanks, do not reduce drag. Discarding the external fuel tanks reduces drag. Same with expendable weight like external ordnance. Internal weight like expendable ordnance do not reduce drag but reduce weight, which affects aircraft performance differently than with both reduced drag and weight. All of this must be factored in from conception, everything from airframe to propulsion to avionics. If the J-20 continues to have propulsion related issues, the jet will have less flexibility in what types of mission it can perform, whereas with the F-22, while it was originally designed for air superiority, the F-22 will be tasked for ground strike missions with no deterioration of performance whenever needed.

Technical issues like these are not 'minor' in any way. They may not be well known but they are as crucial as how to shape for 'stealth'. For most people on forums like this one, these technical issues are practically unheard of and supporters of one jet or the other talks about their jets as if they know everything about the jets.

 

[Ultima Thule]

most fighter aircraft during the cold war did not use weapons bays because they increase weight and size

delta dart had a weapon bays, so did Voodoo

 

[gambit]

delta dart had a weapon bays, so did Voodoo

That is why he said 'most'. My F-111 has a weapons bay.

 

[LKJ86]

Via PLAAF's Weibo

 

[Su33KUB]

delta dart had a weapon bays, so did Voodoo

let me clarify, as Gambit already told a few aircraft carried internal weapons bays, but they were big or attack aircraft, F-111, A-5 Vigilante were interdictors, F-106 was huge, compared to a Mirage III it was too big, in order to have internal weapons bays, you need to increase thrust in a fighter.

F-15 has almost the same TWR to F-22, but F-22 has no aerodynamic clutter so it has no drag generated by external hardpoints or fuel tanks, but but here is the most important part it has engines of 16 tonnes, really economical compared to F100 so it can have higher performance.

try to see, internal weapons bays increase the fuselage size and weight, this creates more drag, in order to solve this you need no external weapons hardpoints, no external fuel tanks and much more powerful engines.

117S for example has less thrust than f119, so you can not expect Su-57 to have better performance than F-22, at similar weights.

F-15 does not need external weapons bays, it is lighter than F-22, thus it needs less thrust to achieve similar TWR than F-22.

Then you have to see both China and Russia if they do not develop high power engines, then J-20 and Su-57 are under powered and even if they do not carry weapons externally they have to overcome much more weight and drag, so F-22 has the need for bigger wings and more powerful engines, as shown in combat Eurofighter with semi-recessed weapons can outfight F-22 in WVR, because it has very high TWR and low wing loading.

F-22 uses TVC nozzles and has high power engines, without similar engines you can not expect J-20 to be a peer and outmaneuver F-22, J-20 is heavy, much much heavier than F-15 and if it uses engines for Su-27 type aircraft, no way it can compete with F-22 in tactics at BVR and WVR because without similar supercruise speed and TWR and TVC nozzles.

 

[Ultima Thule]

let me clarify, as Gambit already told a few aircraft carried internal weapons bays, but they were big or attack aircraft, F-111, A-5 Vigilante were interdictors, F-106 was huge, compared to a Mirage III it was too big, in order to have internal weapons bays, you need to increase thrust in a fighter.

F-15 has almost the same TWR to F-22, but F-22 has no aerodynamic clutter so it has no drag generated by external hardpoints or fuel tanks, but but here is the most important part it has engines of 16 tonnes, really economical compared to F100 so it can have higher performance.

try to see, internal weapons bays increase the fuselage size and weight, this creates more drag, in order to solve this you need no external weapons hardpoints, no external fuel tanks and much more powerful engines.

117S for example has less thrust than f119, so you can not expect Su-57 to have better performance than F-22, at similar weights.

F-15 does not need external weapons bays, it is lighter than F-22, thus it needs less thrust to achieve similar TWR than F-22.

Then you have to see both China and Russia if they do not develop high power engines, then J-20 and Su-57 are under powered and even if they do not carry weapons externally they have to overcome much more weight and drag, so F-22 has the need for bigger wings and more powerful engines, as shown in combat Eurofighter with semi-recessed weapons can outfight F-22 in WVR, because it has very high TWR and low wing loading.

F-22 uses TVC nozzles and has high power engines, without similar engines you can not expect J-20 to be a peer and outmaneuver F-22, J-20 is heavy, much much heavier than F-15 and if it uses engines for Su-27 type aircraft, no way it can compete with F-22 in tactics at BVR and WVR because without similar supercruise speed and TWR and TVC nozzles.

How can internal weapon bays increase drag of the 5th gen stealth jet kindly explain maybe it increases little bit weight and both Russia and China working their 5th gen engine for their 5th gen jets from day one both Su-57/J-20 known to have interim engine,and as they(China/Russia)have different philosophy then USA they will use tactics against enemy(USA)shoot and scoot (leave)guideness of BVR is/will be the job of AWACS @Su33KUB