Chengdu J-20 5th Generation Aircraft News & Discussions

[DrSomnath999]

That's exaclty what an engineer from Dassault Aviation tolde me 2 years ago. When I shown him the first pics of J-20, he said that the fact that the canards are alined on the same plan with the wings, the "bad" impact of canard on RCS is highly reduced.

Henri K.

Hi



can you elaborate this thing a bit if you can

CHEERS

 

[DrSomnath999]

the pic claims
the canard with cut away portion showed lesser RCS than canard without cut away portion

thanks henri K

CHEERS

 

[gambit]

Note the addition of a 'sawtooth pattern' on the canards.

Also note the sawtooth pattern on the trailing edge of the Rafale's canards.

View attachment 180407

If it is true that the J-20's canards received physical radiation control methods -- those sawtooth structures on the trailing edge -- that should tell you that the J-20's engineers KNEW that the canards would be an RCS contributor in ways they did not like.

Why are those sawtooth structures on the trailing edges ? Because that is where surface traveling waves leave the canards and impact the fuselage and the wings. So with those sawtooth structures, the J-20's engineers hope that diffracted signals would be in different directions, minimizing any interactions with the fuselage and the wings. Minimization, not complete elimination.

 

[DrSomnath999]

If it is true that the J-20's canards received physical radiation control methods -- those sawtooth structures on the trailing edge -- that should tell you that the J-20's engineers KNEW that the canards would be an RCS contributor in ways they did not like.

Why are those sawtooth structures on the trailing edges ? Because that is where surface traveling waves leave the canards and impact the fuselage and the wings. So with those sawtooth structures, the J-20's engineers hope that diffracted signals would be in different directions, minimizing any interactions with the fuselage and the wings. Minimization, not complete elimination.

sir it really confirms your prevoius POV

that J20 designers must have taken rafale's strutural design as referrence while designing the canard/LERX part of J20 so they have incorporated saw tooth design too

Chengdu J-20 5th Generation Aircraft | Updates & Discussions. | Page 125

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[aziqbal]

... and even more the YF-23 proposal for the Naval version had a Canard configuration as well (and if I'm not completely wrong, the current Boeing proposal for the F/A-18 successor too). So a canard is not necessarily a reason for being non-stealthy.

Hi Deino I have been logged out of SDF since the server switch over and can't remember my password, a reset isn't working and facebook log in doesn't work either can you get Webby to have a look

Btw I'm Asif iqbal from SDF thanks

 

[gambit]

Canards are not a 'RCS control problem' anymore than main wings and horizontal stabilizers. In fact, all leading and trailing edges on an aircraft reflect radar. The key is planform alignment.

Yes, they are. You are not going to get away with 'Chinese physics' here.

The rules for designing a radar low observable complex body are controls of:

- Quantity of radiators
- Array of radiators
- Modes of radiation

If there is a minimum necessary quantity of radiators on this complex body, the control of their arrays, or configurations and relationships, to each other comes into play. In this, everything is at least an 'issue of concern' if not outright a problem. If canards are necessary but their quantity ( 2 ) cannot be offset by the elimination of other major contributors, then they breached the line from being a normal 'issue of concern' to being a genuine problem.

The above is a drastic example but a necessary one.

Depending on a radiator A's location and array to other structures/radiators, the elimination of other structrures/radiators may not be sufficient to offset radiator A's contribution to final RCS. For the example above, we can work on shrouding the engines, cockpit treatment, etc., but as long as we cannot do anything to that array of radiators in the rear -- the vertical/horizontal stabs configuration that produces the dreaded 90 deg corner reflectors -- all our other works are essentially worthless. The rest of the aircraft can be below the graph but there will always be a large spike above, giving the aircraft away.

Same thing with the J-20's canards. You can bring on charts showing their -- alleged -- individual RCS measurement data like in post 4346, but for those who know better, those charts are meaningless in the absence of any data regarding rule 2: Control of array of radiators.

In other words, we need measurement data for the entire body in order to make any definitive judgement.

Further, complex bodies are unique in their final RCS values. Yes, these aircrafts have cockpits, pairs of wings and stabilators that are in same locations and configurations and they will produce a common RCS signature, but when there are additional radiators like antennas or panel gaps that are unique from aircraft to aircraft, the final RCS values are going to be as unique as the human fingerprints. That mean the canards' contributorship on one aircraft may not be as significant as on another.

If we are to take public opinions as approximate gauges, then the consensus among radar specialists is that the J-20's canards straddles the line between being an 'issue of concern' and being a genuine problem, and that is being generous in the absence of hard measurement data, which all know the Chinese government will not reveal.

 

[longlong]

Yes, they are. You are not going to get away with 'Chinese physics' here.

The rules for designing a radar low observable complex body are controls of:

- Quantity of radiators
- Array of radiators
- Modes of radiation

Those rules can only be employed fully by J-20, not F-22, for J-20 is stealth optimized by the fastest super computer in 21s.

F-22 is an aircraft with some stealth features backed to 1980s and the project is terminated and will be replaced by problematic F-35 and the promised 6-gen aircraft on imagination.

F-22, a generation faded without f*cking in real.

 

[applesauce]

So with those sawtooth structures, the J-20's engineers hope that diffracted signals would be in different directions, minimizing any interactions with the fuselage and the wings. Minimization, not complete elimination.

no.

those engineers don't hope. they test and test and test again, digitally and flight tests and verify that it works, thats the whole point of flight testing.

 

[nomi007]

Suspected Chinese Shen Fei defeated fifth generation aircraft program exposure! Or the F -32?
In January 2011, using the canard of Chengdu J-20 first flight success. Although SAC subsequently introduced in the conventional layout "falcon hawk", but losing four generations of machine program is exactly what has been the focus of everyone's attention. However, the absence of any reference information can, SAC four generations of machines became a fan.

2011, AVIC published his Academy series. Disclose details of the original bid when four generations of machines. However, in this series of illustrations, a wind tunnel model pictures Shenyang four generations of machines were hit mosaic
Despite being obfuscated users based on photographs were analyzed and plotted imagination shape figure, but still can not get "what kind of aerodynamic configuration "message.
In Shenyang had four generations of machine program soon to be forgotten when China Airlines reported a story on December 23 for the first time disclosed without coding processing photos.

Decrypted image is clearly visible in the wind tunnel model: This model uses "canard wing horizontal tail , "the three wing aerodynamic layout, with the previous network spread a black and white picture is more consistent.

Three wing is trying to duck and the general layout of the comprehensive advantages of the new aerodynamic layout, but not as good as canard layout and overall design of conventional indicators and stealth capabilities.
Sukhoi Su-47 is the ultimate representative of three wing technology practical effort, but its maneuverability and canard aircraft was no obvious advantage, but do not have the canard shortened fuselage and reduce structural weight. After this, Shenyang introduced midsize four-generation machine "falcon hawk" with a conventional aerodynamic layout

 

[hk299792458]

Analysis : End of year surge for Chengdu J-20 fighter programme

Richard D Fisher Jr, Washington, DC - IHS Jane's Defence Weekly
06 January 2015

In November and December 2014 two additional prototypes of the Chengdu Aircraft Corporation's (CAC) J-20 fifth-generation fighter emerged, advancing its development towards a possible initial operational capability (IOC) of 2017-18.

The J-20 programme currently features six known prototypes. Two are early technology development articles (serial numbers 2001 and 2002) that emerged in 2009 and 2010, while four are modified versions closer to operational prototypes (serial numbers 2011, 2012, 2013, and 2015) that all emerged in 2014.

No prototype numbered 2014 has yet to appear and may not, given the traditional Chinese view that four is an unlucky number.

Chinese aircraft spotters responsible for early internet photos report that the latest prototypes, 2013 and 2015, made their maiden flights from the CAC airfield on 29 November and 18 December 2014 respectively.

Both have most of the refinements seen on aircraft 2011, which emerged in February 2014: cropped canards and vertical stabilisers, a modified air intake, modified wing leading-edge extensions, and a new electro-optical targeting system (EOTS) under the nose.

However, 2013 and 2015 lack the nose-mounted pitot tubes that featured on the earlier prototypes. In addition, number 2015 has longer and sharper-shaped rear-fuselage horizontal strakes. Although this aft surface does not appear to be movable, it may contribute to aircraft stability, as a similar - though movable - surface did for the Grumman X-29 technology demonstrator.

Early internet-sourced images have also emerged of the J-20's retractable refuelling probe, placed on the upper starboard of the nose. The development status of an indigenous Chinese turbofan for the J-20, often referred to as the WS-15, remains unknown. There is speculation that early J-20 examples may use a version of the Russian Saturn AL-31 turbofan.

In April 2014 an Asian government source told IHS Jane's that China would have 24 J-20s by 2020, which if realised, could constitute a first operational regiment. This would indicate that IOC may occur in the 2017-18 timeframe.

Henri K.

 

[cnleio]

J-20 open all weapons-bay

 

[sancho]

... and even more the YF-23 proposal for the Naval version had a Canard configuration as well (and if I'm not completely wrong, the current Boeing proposal for the F/A-18 successor too). So a canard is not necessarily a reason for being non-stealthy.

That depends on where the focus is, on the RCS reduction or the navalisation! Both the naval YF23 as well as Boeings latest concepts are meant to be carrier fighters and just as for J15, the canards are mainly added to improve the handling during carrier landings. So these examples might compromise on RCS, in favour for specific operational benefits, contrary to the original YF23 design for example, that was aimed on a very low overall signature.

 

[Deino]

Interesting comparison ...

if the gif-image does not work, here's the original link:

http://www.fyjs.cn/thread-1111107-1-1.html

Deino

 

[Deino]

PS ... even if they're not accounting for potential perspective effects. !

 

[Deino]

From yesterday ...