November 3, 2016

China's Chengdu J-20 Shows Little Evidence of Stealth Capabilities


China's Chengdu J-20 (above) showed less stealthiness and less flying ability than the 26 year old Northrop YF-23 technology demonstrator. 

America's YF-23 (immediately below) supercruised in 1990 while the J-20 only managed moderate subsonic in 2016 - 26 years later.


----------------------------------------------------------------------------------------

Below are some YF-23 plans. Is it possible China stole plans from an ex Northrop source to help design China's J-20?


--------------
COMMENTS

Submarine Matters studies, above water, jets sometimes. 


At one of China's major weapons PR events (the China International Aviation & Aerospace Exhibition, Zhuhai city, Guangdong Province) China showcased the beginnings of a technology demonstrator - which may become a Chengdu J-20 stealth fighter in a decade. 


The J-20 has:


-  the splayed out tail of a 26 year old YF-23 technology demonstrator, and 


-  canards like the Saab Gripen and some other fourth generation jets. 


Aircraft aficionados will recall that the YF-23 competed against and to the Lockheed YF-22 in 1991 in what effectively became the US stealth superiority fighter fly-off. China, like Russia and India, all have optimistic visions of developing stealth air superiority fighters in a mere 5-10 years time. This is unlikely. See the list of just some stealth requirements below.


STEALTH REQUIREMENTS 


1.  The easiest part is putting together impressive looking angles, by minimising verticals, to try to make the aircraft look flat - essentially a flying wing. Jack Northrop achieved a semi-safe flying wing  by 1943.


2.  The next most obvious attempted stealth qualities is how it moves using its jet engines. Recessing the engines so they will be less noisy and (most important) their heat signatures don't show much, and don't attract missiles, is difficult.


The F-22 can supercruise - the F-35 cannot. With relatively low fuel use an F-22 can rely on the "cruise" setting of its engines to achieve supersonic speeds. That is, there is no need to use loud, hot, after-burners. Afterburners flames can be seen at night, infrared detecters can also see them. Sensor/missile combinations can shoot after-burners users down. 


The ability of an engine to efficiently and regularly thrust-vector is also important to stealthy/Fifth generation air superiority fighters. In that respect Russia, and many other observers, believe China really made a long fought deal to receive examples of Russia's Su-35 fighter in order to reverse engineer the jet engines that the Su-35 uses. Creating a Chinese copy of Russia's AL-41F1S series engine may be a prime Chinese intention.


3.  Those with passive electromagnetic reception gear might be able to assess how unstealthy the J-20 radar, communications and other electronic emissions are.


4.  Those friendlies with distributed active radar pulses (without the ability to cue a jet in an airshow with their eyeballs) might want to assess how easily the J-20 can be detected and targetted.


5.  The radar absorbing presence and aerodynamic effectiveness of the J-20's Radar/Radiation Absorbent Material (RAM) coating (if it has any) would be the next checklist item in an assessment of the J-20's stealthiness. Assessing RAM may be difficult with a flying J-20 at a distance - much easier on the ground chipping off some RAM coating one foot away.  


See many of these aircraft stealth requirements here.




BACKGROUND

The Chengdu J-20 (not yet stealthy) fighter made its first mobile public appearance on October 31, 2016, at China's International Aviation & Aerospace ExhibitionZhuhai city,


The tentative, gentle movements of the J-20 in its only public flight - is captured in the Youtube above


The two flying J-20s looked flyable enough for their 25 tonne (near empty) weight and didn't test any major capabilities. 

Stealthy weapons bays, if there were any, remained shut. This might mean that the J-20s still need to hang highly unstealthy stores (bombs, missiles, sensor pods and fuel containers) from their wings and centerlines.


In terms of what is seen in the Youtube above it appears the J-20 is at least 25 years behind the F-22 in flight dynamics. However the Chinese are generally subtle in their conventional weapon testing. The J-20 may be capable of much more when the camera isn't looking.  

14 comments:

Nicky K.D Chaleunphone said...

Hi Pete,
What I think China just showed is what the YF-23 should have been. Which could have been out modernized F-16.

Andrej T said...

Some experts says that it Chinese plane take basics from Russian project 1.44...

Peter Coates said...

Hi Andrj T

Good weapons program managers certainly gain from studying, stealing or buying technology from a strategic competitors (or neutral Sweden's) weapons programs.

Yes there are some similarities with the 1.44 at the more superficial end of stealth assessments eg. airframe (certainly the tail(s) and canards). https://en.wikipedia.org/wiki/Mikoyan_Project_1.44#Testing_and_cancellation

Equally I could claim that the Chinese J-20 and J-31 and Russo-Indian T-50/PAK FA has taken basic airframe ideas from the F-22 and F-35.

Regards

Pete

Swanand Dixit said...

J-20 is worst try for 5th gen stealth..its useless threat..canard configuration ..exposed engines..large size..are few of the factors which makes it ridiculous stealth fighter..look at pak-fa or rafale if you want canards..they are LERX leading edge root extensions or more advanced X-36 of mcdonell douglous..chinese are ridiculous in copying also..each and every chinese product comes with no warrenty and no guarenty..a rafale even a SU-30MKI can beat ass out of this J-20

Josh said...

@Pete

I don't know nearly enough about aircraft to judge the RCS of aircraft. That said the top of the engine intakes to seem a little too perpendicular to the axis of travel, I'd expect an outward slanting LERX or more of a 'notch' like the F-35 intake. I've heard that canards are an RCS no-no, though its has never been explained to me why - I would have thought if they are properly angled like the wing they can reflect away from the a/c just as well. I am quiet certain that the compressor fan faces are in fact concealed in the airframe (or else this is not a low RCS design AT ALL) and I know previous prototypes of the J20 definitely had internal weapon bays with operational doors, if not actual weapon delivery capability.

Noise isn't a consideration in stealth aircraft as far as I can tell. In fact the F-22/35 are as far as I know the loudest a/c in USAF inventory right now, though apparently the F-104 was pretty legendary in this regard as well (and also could super cruise, before it was cool). Similarly thrust vectoring does nothing for stealth and is purely a maneuverability feature, though is a feature in some 5th and 4.5 gen a/c. The Russians seem to put those most stock into thrust vectoring; the only other production example I can think of is the F-22.

The much bigger question would be avionics - I'm assuming an AESA will be installed and their appear to be EO/IR ports on the side of the aircraft which could be a DAS like system, or minimally a 360 missile warning detection system. There does NOT seem to be an internalized targeting/IR system like the F-35, but since this a/c is probably more BVR fighter and anti-ship fighter bomber they likely have no pressing need for one. There's no indication one way or another if there is a comprehensive ESM or ECM system. And of course the level of integration between sensors will be a big question mark barring someone stealing a plane.

In terms of performance, if Chinese engines are used then those aircraft are probably just as anemic as they look in the video. The Chinese are still perfecting jet engine manufacture and recently consolidated ~20 engineering and parts firms into one large national engine manufacturer in an attempt to push their engine tech forward to the point of being competitive with Pratt/GE/Royce. It will take a few years to a decade before they are in that league, but they'll likely get there considering the shear amount of resources they are throwing at the problem.

Mostly though I'm spinning my wheels here; really about all we can say about the J20 right now based on this video is that it does in fact fly and is reportedly loud.


Cheers,
Josh

Anonymous said...

My 2cents:

- Convergence -> Similar requirements and same law of physics will lead to similar solutions.

- Espionage -> Only fools would not try to get their hand on foreign mil-tech through whatever channel. Everything is fair in love and war.

- What we have seen so far, is just four demonstrators and around 11 prototypes. The earlier series-blocks be then be tweaked and later production-batches could be massively upgraded.

- Software, sensors, ammo and materials is unknown territory for us and maybe even for "interested parties".

- Sooner or later China's size will be enough to push them into the front in many fields. Aviation will be among it.

- I am very much tired of the old China-stole-this-meme. Their Y20 transport-plane was conceptualized by Antonov. Kamov got the contract to develop the Z-10 combat-helicopter. France still receives royalties for the licensed Super-Frelons. Maybe in 10 years we will learn that MiG is a sub-contractor on this plane.

@ Swanand Dixit: India is no position to critize the Chinese MIC. The J-20 is a clear sign how far India is trailing China now. 15 year-saga of MMRCA and not a single jet delivered. Let's talk business when India's AMCA comes along.

Regards,
Team Eurowussies

Anonymous said...

@Anon

Size doesn't determine performance. All male snickering aside. The Great Leap Forward and the Cultural Revolution devastated the Chinese in terms of academics and engineering. They really had to start from zero. In fact I know a Japanese poster on another forum who revers The Chairman because he feels otherwise China might be a much more capable country, and Mao sufficiently destroyed China such that the Pacific rim could prosper without having to worry about China.

And this is true: they have 5th generation looking planes, but they lack engines on par with the Russians, who aren't known for being at the fore front of engine technology. They are struggling to make their first multi engined MPA and cargo plane. Most of their domestic large multi engined designs are Y-8 based (which is An-22, with US pre Tienenmen Sq pressurization tech from Lockheed). So while when China focuses on some technologies and does catch up mostly, broadly they are incapable of being competitive. The CCP is willing to be behind the times if it means they have more control; they'd rather have a 1950's era bomber than have 1930's revolution in my opinion.

Cheers,
Josh

Peter Coates said...

Hi Josh

Where you say “I've heard that canards are an [radar cross section] RCS no-no, though its has never been explained to me why”
Perhaps the gap between the canard and that portion of the wing’s leading edge immediately behind the canard is unstealthy?

Yes having stealthy (minimally detectable radiation emitting) avionics (radar, electro-optical/infrared (EO/IR) etc) is important.

Here are some good points on RCS. "An object reflects a limited amount of radar energy back to the source. The factors that influence this include:

• the material of which the target is made;
• the absolute size of the target;
• the relative size of the target (in relation to the wavelength of the illuminating radar);
• the incident angle (angle at which the radar beam hits a particular portion of target which depends upon shape of target and its orientation to the radar source);
• the reflected angle (angle at which the reflected beam leaves the part of the target hit, it depends upon incident angle);
• the polarization of transmitted and the received radiation in respect to the orientation of the target"

"ACTIVE CANCELLATION

With active cancellation, the target generates a radar signal equal in intensity but opposite in phase to the predicted reflection of an incident radar signal (similarly to noise canceling ear phones). This creates destructive interference between the reflected and generated signals, resulting in reduced RCS. To incorporate active cancellation techniques, the precise characteristics of the waveform and angle of arrival of the illuminating radar signal must be known, since they define the nature of generated energy required for cancellation. Except against simple or low frequency radar systems, the implementation of active cancellation techniques is extremely difficult due to the complex processing requirements and the difficulty of predicting the exact nature of the reflected radar signal over a broad aspect of an aircraft, missile or other target....

see more at http://en.wikipedia.org/wiki/Radar_cross-section

Regards

Pete

Peter Coates said...

Hi Team Eurowussies

Complaints that China steals are probably unfair: I see reasons as:

1. Racism

2. That China is the No.2 economic power which may surpass the US position in 20 years, and

3. China is particularly good at casting a wide information net, reverse engineering high tech, then mass produccing weapons or components.

4. China's authoritarian yet very competitive system makes it all the more efficient in doing "3."

Regards

Pete

Anonymous said...

Some people speculate about the aim of the J-20. The interesting thougt for me is that this aircraft is there to hunt the big game: AWACS, tanker and such aircraft.

The aircraft just needs some kind of frontal stealth and a few longe range missiles between the engines.

Regards,
MHalblaub

Swanand Dixit said...

Did you ever heared words like fully baked caked or half baked caked? Both will look same from outside.But nobdy will eat half baked cake to abvoid stomache pain..The same case with J-20, i am not comparing chinese fighter with Indian one..if you want to stand out come come compare with F-22,PAK-FA,Rafale,Typhoon etc..chinese are competing with these fighters which are present now..a stolen MIG 1.44 design does not mean china achieved something..Indians dont do that..the AMCA design is purely ours and we never eat half baked stuff..we have our fighters to be pass through stingent processes like IOC, FOC etc unlike yours..

Peter Coates said...

Hi Swanand [at 9/11/16 8:57 PM]

I may be wrong but suggest a cultural difference between China and India is:

- China does not list all its arms program hopes, in terms acronyms decades before their programs are finalised but,

- But Indian politicians and officials do.

Hence for those who wish to keep track. India's longterm aircraft program to-do list includes:

- "AMCA" https://en.wikipedia.org/wiki/HAL_AMCA which for some unknown reason is ethereal and kept distinct from the Indo-Russo PAK FA

- IOC and FOC seems to be widely applied to the Tejas (Mirage III in a time warp) light fighter first conceived in 1969 https://en.wikipedia.org/wiki/HAL_Tejas#Origins

The situation is little better with India's multi-decade unfinished submarine (SSBN and SSN) visions. Although I do admit India has assembled one SSK in the 21st century (one Kalvari Scorpene) https://en.wikipedia.org/wiki/Kalvari-class_submarine - athough INS Kalvari has not yet been commissioned https://en.wikipedia.org/wiki/INS_Kalvari_(S50) .

What I'm saying is China quietly achieves many arms breakthroughs, and substantial production. Too many Indian politicians and officials talk about acheivement being only 2-3 years away, but it turns out more like 2-3 decades away.

Regards

Pete

Anonymous said...

Canard configuration can present low RCS. During the ATF evaluation decades back, several canard-delta wing configurations were presented and they did present comparable low RCS to F22. The USAF does not like canards but Europeans do.

For the limited showing of the J20 we have seen, the aircraft acceleration and roll are slow (even though the engines are next to each other and not spread out like the F14). Clearly not a dogfighter. It seems it loses quite a bit of speed during those not so high G turns as most delta wings do. The gaps on the air frame are quite large so its RCS is probably not top.
KQN

Peter Coates said...

Thanks KQN

The J20 clearly needs years of development, including much more powerful engines, to become a fifth generation fighter-bomber.

Regards

Pete