J20 Stealth Fighter

[MiG-29SMT]

 

[Karthi]

Just one thing stealth is not the ultimate word in air battle, All of you are only considering Frontal RCS , the RCS is much bigger in other angles , Canards slightly add RCS but at the same time sligh reduces the RCS from the rear , if we apply the same rule .


Moreover Radars will not be able to track Stealthy Aircrafts from long distance but still it can detect the presence by some unusual Blips in their Radar, that is fade contacts . They will immediately alerted in the presence of Stealth aircraft .


Su 57 is a perfect example of antistealth , it has enough Stealth to delay the detection when ever the adversaries detect Su 57 enemies also fell into the Sensor coverage of Su 57 , and with its superior kinematics Su 57 can defeat almost anything in the air , J20 is not capable as Su 57 .

Moreover everything is based on tactics

 

[MiG-29SMT]

Just one thing stealth is not the ultimate word in air battle, All of you are only considering Frontal RCS , the RCS is much bigger in other angles , Canards slightly add RCS but at the same time sligh reduces the RCS from the rear , if we apply the same rule .


Moreover Radars will not be able to track Stealthy Aircrafts from long distance but still it can detect the presence by some unusual Blips in their Radar, that is fade contacts . They will immediately alerted in the presence of Stealth aircraft .


Su 57 is a perfect example of antistealth , it has enough Stealth to delay the detection when ever the adversaries detect Su 57 enemies also fell into the Sensor coverage of Su 57 , and with its superior kinematics Su 57 can defeat almost anything in the air , J20 is not capable as Su 57 .

Moreover everything is based on tactics

in the case of J-20 the canards are visible from behind and front of the aircraft

from behind too it is quiet visible

F-22 has a more homogeneous planforming even from behind

those canards are pretty visible from any quarter

 

[IndianHawk]

in the case of J-20 the canards are visible from behind and front of the aircraft

View attachment 48808

from behind too it is quiet visible
View attachment 48809
F-22 has a more homogeneous planforming even from behind

View attachment 48810

those canards are pretty visible from any quarter
View attachment 48811

Absolutely..
There is a reason why f22 f35 and su57 none of them have canards. And proposed European design fcas and tempest don't have canards either.

And neither does kfx or amca have canards.

Chinese don't want to admit it. But j20 is half assed compromise. Its stealth is at best marginal.

 

[Karthi]

in the case of J-20 the canards are visible from behind and front of the aircraft

View attachment 48808

from behind too it is quiet visible
View attachment 48809
F-22 has a more homogeneous planforming even from behind

View attachment 48810

those canards are pretty visible from any quarter
View attachment 48811

It's visible but Radar return is minimum ,it's mainly the deflection of control surfaces causes the Radar return , in F22 or F35 the horizontal tail causes The Radars return is if the Enemy Aircraft illuminate from a lower altitude and the same goes to illuminate from above , J20 have Canard but dont horizontal tail , if each aircraft approaches in a straight line , the manuvering is less so the deflection Canards is minimum but just slightly adds up for RCS that is not a significant contribution.

J20 is a good aircraft but the least advanced in all 5th gen fighters but better than all 4th gen fighter

 

[MiG-29SMT]

It's visible but Radar return is minimum ,it's mainly the deflection of control surfaces causes the Radar return , in F22 or F35 the horizontal tail causes The Radars return is if the Enemy Aircraft illuminate from a lower altitude and the same goes to illuminate from above , J20 have Canard but dont horizontal tail , if each aircraft approaches in a straight line , the manuvering is less so the deflection Canards is minimum but just slightly adds up for RCS that is not a significant contribution.

J20 is a good aircraft but the least advanced in all 5th gen fighters but better than all 4th gen fighter

In the case of F-22 and Su-57 they have thrust vectoring control nozzles so they do not deflect the tail as aircraft without this type of nozzles, thus they are stealthy; frontally the canards are not hidden, nor from the back plus at this moment J-20 has no thrust vectoring nozzles.

the J-20 uses more aerodynamic control devices, this creates more deflection of flaps or canards, F-22 and Su-57 deflect less their aerodynamic control surfaces so in general terms the F-22 is far much more stealthy than J-20.

Su-57 already super cruises so faster speeds and lower control surfaces makes for a more difficult target.

The J-20 has low observable reduction measures but is not the most stealthy aircraft, the Chinese over hype their aircraft

 

[MiG-29SMT]

Absolutely..
There is a reason why f22 f35 and su57 none of them have canards. And proposed European design fcas and tempest don't have canards either.

And neither does kfx or amca have canards.

Chinese don't want to admit it. But j20 is half assed compromise. Its stealth is at best marginal.

The advantage of levcons is they do not kill lift with canard downwash over the wing and are better for planforming

In general terms LEVCONs do not kill lift due to downwash and the Su-50 wing fences in the under the wing weapons bays




The results indicated that although downwash from the canard reduced the wing lift at angles of attack up to approximately 16°, the total lift was substantially greater with the canard on than with the canard off. At angles of attack above 16°, the canard delayed the wing stall. Changing canard deflection had essentially no effect on the total lift, since the additional lift generated by the canard deflection was lost on the wing due to an increased downwash at the wing from the canard.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740003706.pdf

 

[Karthi]

In the case of F-22 and Su-57 they have thrust vectoring control nozzles so they do not deflect the tail as aircraft without this type of nozzles, thus they are stealthy; frontally the canards are not hidden, nor from the back plus at this moment J-20 has no thrust vectoring nozzles.

the J-20 uses more aerodynamic control devices, this creates more deflection of flaps or canards, F-22 and Su-57 deflect less their aerodynamic control surfaces so in general terms the F-22 is far much more stealthy than J-20.

Su-57 already super cruises so faster speeds and lower control surfaces makes for a more difficult target.

The J-20 has low observable reduction measures but is not the most stealthy aircraft, the Chinese over hype their aircraft

TVC and Control Surfaces are working in tandem To manuvering , the control surfaces deflect even after inititation of TVC. and what do you mean by stealth control surfaces , Range of Motion , and cooling for IR apart from That is there any special stealth features for Control surface rather than planform alignment??

 

[MiG-29SMT]

TVC and Control Surfaces are working in tandem To manuvering , the control surfaces deflect even after inititation of TVC. and what do you mean by stealth control surfaces , Range of Motion , and cooling for IR apart from That is there any special stealth features for Control surface rather than planform alignment??

with thrust vectoring nozzles there is a reduction in deflection in fact the tailerons of F-22 are used more for roll than for pitch thanks to TVC nozzles, J-20 needs to deflect more it is less stealthy for sure

 

[MiG-29SMT]

The goal of increasing controllability is to increase the envelope of positive control for the pilot, especially at high angles of attack or sideslip. A solution for increased controllability demands is for a thrust vectoring control system (TVCS) to provide the required forces and moments (ref. 6).





Reduction in Vertical Tail Size
Aircraft designers have suggested that the installation of TVCS increases the amount of control power and allows a size reduction of the vertical tail. The size reduction of the vertical tail also decreases the lateral-directional stability of the aircraft as well as control power of the rudder thereby changing the dynamics of the aircraft. To estimate the effects of vertical tail size reduction with TVCS control 22 power, the dynamic response for the aircraft was studied with maximum afterburner and deflection thrust vectoring at 100, 75, 50, and 0 percent tail height and compared with the baseline aircraft.



The vertical tail height can be reduced significantly for an aircraft by using thrust vectoring; however, only through careful attention to the tail size, vectoring effectiveness, as well as vane to rudder scheduling will the optimum control and performance be obtained.



https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19920012114.pdf

Su-57 thanks to TVC nozzles reduced the vertical tail size, that a smaller MiG-35 has bigger vertical tails

Su-35 also has bigger tails than Su-57

Stealth The one area in which great benefits can be achieved through the use of thrust vectoring is that of stealth. Because radar cross-section is a measure of the observability of the aircraft and is an logarithmic function of the profile area presented by the aircraft, small reductions in this area realize great benefits. From a side view of the aircraft, the fuselage, cockpit, and vertical stabilizer are the main contributors of observability (ref. 15). The current stealth modifications to the F-16 aircraft include radar absorbing materials in the intake and a reflective gold-covered canopy. Because the fuselage size is relatively constant, it can be concluded that the reduction of the vertical stabilizer has the largest room for improvement (ref. 16). The addition of a TVCS may nominally increase the observability of the aircraft, but a large reflective vertical tail is harder to mask than a faired TVCS. Quantitative improvements in radar observability are very difficult to predict and require thorough testing. The amount that the tail size can be reduced is largely a consideration of the dynamic stability and control of the aircraft

J-20 could not do that and retained even ventral fins

 

[MiG-29SMT]

The drag coefficients were calculated at 0° angle of attack with no surface deflections and, therefore, do not include the trim drag, the drag caused by control surfaces, or the unvectored jet-induced drag. Skin friction drag can be reduced by removing the vertical tail. Since skin friction drag accounts for a little more than half the drag caused by the tail, higher drag savings could be expected. By removing the vertical tail, substantial drag reduction could be achieved if drag as a result of the TVCS is not significant.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19920012114.pdf

The J-20 used ventral fins that reduced stealth but increase directional lateral stability, since ventral vertical fins are not blanketed by the fuselage as dorsal vertical fins at high AoA.

Also these ventral fins reduced any gain of vertical tail size reduction

The ventral fin is apparently added when the fuselage shields so much of the vertical stabilizer at higher angles of attack that a fin is appended to the belly. This is often used to prevent yaw, especially in twin-engine aircraft where only one engine is operating. To gain more stability, two ventral fins are often installed

Aviation Words — Ventral Fin | EAA

www.eaa.org

 

[MiG-29SMT]

 

[Karthi]

The Chinese fifth-generation J-20 fighter could be powered by new Russian engine

China is interested in acquiring a batch of Product 30 aircraft engines, which are being developed specifically for the Su-57 fighter, learned BulgarianMilitary.com citing Chinese journalists report.

The latest Su-57 is the most advanced Russian fighter, whose strengths include its excellent maneuverability. At the moment, AL-41F1 power units are used on these aircraft, but in the future they will be replaced by completely new engines, known in the media under the code name Product 30. China wants to have this unique motor at its disposal, Moscow will receive an offer to purchase it right after the start of its mass production.

“While maintaining high performance and traction Product 30 boasts low fuel consumption, this parameter is 30% lower than that of its predecessors,” noted Sohu authors.

However, not only its low fuel consumption attracts the new Russian engine of the Chinese military. The nozzle of the power unit can be deflected at a sufficiently large angle, which allows for impressive maneuverability for the aircraft. During air combat, this factor can be crucial.

Beijing intends to install these engines on J-20 fighters, which are currently equipped with other engines from the Russian Federation – AL-31FN. China will make every effort to agree with the Russian Federation on the supply of Product 30, an extremely tempting offer will be made to Moscow

 

[J20!]

I do not misunderstand, i said the Chinese knew the limits of placing a high wing on J-20, the limitation was no room to place the canard above wing level.

Having that limitation the wing and canard were coplanar in design, but they knew as many studies on the west with dihedral you increase lift.

Consider adding weapons bays increase weight and` frontal cross section, furthermore the intake inlet ducts by being S Shaped, they increase weight, the wing was pushed aft, they fixed that by a negative sweep to the trailing edge of the wing and transitioning from diamond cross section to rounded one on the engine nozzles and nacelles.

So the wing by being pushed back by the canard, increase the need to more lift.
thus the dihedral.



On Rafale you have real well designed canards with close distance to the wing, LERX and wing fuselage blending

View attachment 48700
on the J-20 the wing trailing edge is closer to the engine nozzles than Rafale
View attachment 48701

This right here is the problem with your analysis.

You keep trying to apply configurations from the Rafale onto the J20 just because they are both canard delta's. They have vastly different performance requirements. Performance requirements define the design compromises made on any airframe, not the other way around.

The Rafale was designed around being an "omnirole" aircraft. The J20's configuration is obviously "intended to provide good sustained supersonic cruise performance with a suitable engine type, and good manoeuvre performance in transonic and supersonic regimes" as Carlo Kopp puts it. This is clearly detailed in the study performed by Dr. Song and his team.

Even against the Typhoon, the Rafale cannot climb as fast, fly as high, retain speed as well or maneuver as well at transonic and supersonic speed.

Adopting the Rafale's configuration would cripple the J20's supersonic performance. Which is why I find it odd that you repeatedly bemoan that Chengdu didn't just copy Rafale's aerodynamics. The rafale's aerodynamic configuration is not synonymous with the interceptor role due to limits on its supersonic performance by the very canard configuration you advocate for.

The longer distance between canards and the leading edge of the wing translates to maximised maneuverability during supersonic flight with an air superiority load. Close coupled canards ala Rafale or the J10 are optimised for maximum lift generation and ordinance carrying capacity over a wider speed envelope.

The J10 or Rafale will never match the J20's performance in the supersonic flight envelope because of their aerodynamics. They will both struggle to retain speed when maneuvering because of their canard configuration vis-a-vis the J20 and Typhoon.

As to the position of the main wing, I believe you are versed enough to notice that this arrangement is clearly meant to minimise supersonic drag on the airframe. The modelling performed and detailed in Song's paper clearly show that this configuration (canard, LERX and lft body) maximised lift whilst minising overall drag on the airframe ie met their performance requirements. The wing wasn't "pushed aft", its there by design to meet performance requirements.

China did not innovate, there is nothing in aerodynamics the West learnt from China on J-20

As to innovation, I believe anyone can see that the configuration chosen by 611 institute demonstrates a commitment to innovating to meet performance requirements whilst overcoming inherent restrictions (eg. engine thrust - until WS15's enter production). Not even going into their aircraft being the first stealth aircraft developed and produced outside of the US and Russia.

 

[shiphone]

is it the Product/Item 30 ?

---------------------------------------
at this moment ,the WS-10C powered J-20A is in mass production.

--------
another image of PT-2013 with pylons...the image was taken long time ago.

 

[J20!]

Limitations of the model:

1. The simulator at this time does not model backscatter from edge diffraction effects although the resulting error will be mitigated by the reality that in a mature production design these RCS contributions are reduced by edge treatments (not done yet, I can pull images to point out where the edge treatment isn't still done);

Untrue. So far we've seen 2 layers of edge treatments. Images of the J20 in primer show either or both sawtooth paterns and composite stealth structures on all control surfaces:

In addition to the edge treatment, all access hatches and operating doors are sawtoothed and all apetures are edge-aligned as seen above.

The edge treatment on the J20 once painted in also obvious to see. The inlets, canards, LERX, wing leading edge, vertical stabilizers, tail booms and vertical fins are all treated.

Please provide the photos that show the untreated edges you allude to...

1. The simulator at this time does not model backscatter from surface travelling wave effects (biggest motherload of all),. In the forward and aft hemispheres these can be dominant scattering sources where specular contributions are low. The magnitude of these RCS contributions is reduced by edge treatments, lossy surface coatings, gap treatments, and panel serrations; (Now mitigates in the FOC variant)
2. The simulator at this time does not model backscatter from the AESA bay in the passband of a bandpass radome, due to the absence of any data on the intended design of same, the resulting error will be mitigated by the reality that in a mature production design much effort will be expended in suppressing passband RCS contributions;
3. The simulator at this time does not model backscatter from the engine inlet tunnels (because its solution is serpentine intakes which is applied in J20) or engine exhaust tailpipes,
4. The simulator at this time does not model structural mode RCS contributions from antenna and EO apertures, panel joins, panel and door gaps, fasteners and other minor contributors; although the resulting error will be mitigated by the reality that in a mature production design these RCS contributions are reduced by RCS reduction treatments. (Now mitigates in the FOC variants)
5. The PO computational algorithm performs most accurately at broadside or near normal angles of incidence, with decreasing accuracy at increasingly shallow angles of incidence, reflecting the limitations of PO modelling. The simulator does not implement the Mitzner/Ufimtsev corrections for edge currents (See MIT lecture, for the edge currents on a planform). While a number of test runs with basic shapes showed good agreement between the PO simulation and backscatter peaks in third party test sample measurements, even at incidence angles below 10°, characteristically PO will underestimate backscatter in nulls. This limitation must be considered when assessing results for the nose and tail aspects, where most specular RCS contributions arise at very shallow angles39.

The APA modelling was done on the very 1st prototype shortly after its first flight; which is why it is a "preliminary assessment". There have been 3 iterative changes to the airframe since. Which is why they repeatedly allude to a "matured production airframe". Ofcourse the study has limitations judging by the fact that they do not have access to the actual airframe.

Coming to the point to your questions

1. I never said RCS spike due to canards would be "disastrously drastic". I said, it going to spike RCS time to time especially during STR performance which will contribute to different AoA as trailing edge electric diffractions. (In MIT lecture).
Why do you assume the canards would be always in neutral position? (Read #1 again)
2. I am not talking about frontal aspect stealth here, J20 achieves that thus making it LO. Refrain yourself from pulling this discussion to a different angle such as "frontal aspect stealth characteristics".
"Please understand that LO doesn't mean VLO."

Here's what an expert has to say. (Watch from 2:18) and here's the drawdown:

LO at frontal aspect, but not all aspect (here the benchmark is F22, not F35 nor SU57)
Airspace denial, putting high value assets such as tankers, awacs, bombers or gunships at bay.
High endurance, interceptor.

3. Its a bomber too, considering missions where stealth isn't required, with its long endurance, high service ceiling and upcoming better engines, why wouldn't PLAF would consider it as nuclear delivery platform? Cruise missiles can be fitted on its pylons considering its a Delta Canard?

Exactly. So where do you hear him calling it a bomber? Large fuel capacity, good supersonic performance, LO airframe. Where does "bomber" come in? The F22 can carry 2 2000lb bombs or 8 SDB's internally but its never been called a bomber? I'm not even sure it has any cruise missiles integrated with it.

We've NEVER seen any kind of A2G ordinance on the J20. Even in its operations with J16's and J10's its always operated in an air superiority role to clear the way for A2G ladden J16's.

Your "bomber" assertions come with no evidence other that "its large". Well yeah, so is the SU35, but its not a bomber either. The performance requirements for the JXX programme have all pointed towards air superiority, not a bomber role. According to pentagon intel reports there are VLO strategic and regional bomber platforms in the works for the PLAAF.

Eventually the PLAAF will integrate a2g munitions on the J20 as the platform matures however, even being capable of undertaking SEAD or classic strike missions does not make it a "bomber".

Nice write up from Rick Joe from the diplomat below. I have a subscription, but I believe the first 5 articles are free or something.

https://thediplomat.com/2018/12/chinas-stealth-fighter-its-time-to-discuss-j-20s-agility/

3. Finally, I'll ask a single question to end this debate once and for all. Why is your next J31 fighter drops the idea of canards all together than? Why go to a conventional stealth jet airframe design much like F35?
Because J20 was never considered all aspect stealth (True VLO stealth), J31 can be thought as VLO at frontal aspect.
And to your question that F35 and SU57 is VLO? Yes and No. Yes because at frontal aspect, F35 show radar returns much lower than even F22. No because not all aspect stealth.

1. Again, the FC31 is not a PLA sanctioned project yet.
2. In addtion, the FC31 does not have the same PERFORMANCE REQUIREMENTS as the JXX programme. its a medium-weight airframe with obviously a much smaller range.
3. The FC31 even if it where purchased by the PLAAF is not a successor or replacement for the J20. The VLO intecerpt and air superiority mission would still fall to the J20, so your point is moot
4. The losing bid for the JXX programme was a "conventional stealth airframe WITH CANARDS ie. the J20 met the requirements for stealth, supercruise, supersonic and transonic maneuvering better than the "conventional airframe".
5. Just like the operational SU57, F35 and the yet to fly AMCA and KFX, the J20 is not VLO in the rear aspect because it uses conventional engine nozzles which brings compromises to detection in the IR spectrum. J20, SU57 and F35 have RCS reduction measures applied in the rear aspect, but overall, I believe its quite telling that none of them went the F22 route. How much does it really impact operational viability in the air superiority role not to have full all aspect stealth? Is it worth the price and weight penalties?

Here the end cookie
Figure1:

Proposed advanced design to J20.
Observations:

1. Complete elimination of tail section, essentially a tailless configuration. (looks like someone is cutting down on RCS at tail section and Canards desperately)
2. Canards size reduced.
3. Improved LO.

Was this "proposed design" subjected to aerodynamic modelling and wind tunnel testing? Which studies support the implementation of such a design? What are the aerodynamic implications of changing the shape and size of the canards? And what are the aerodynamic implications of placing the wings there? What are the weight penalties of using that nozzle arrangement and which engines will compensate for that weight with additional thrust? What with the abnormal placement of the vertical stabilizers? How will this design compensate for Yaw instability created by removing the vental fins? How does this model overcome the penalty of lift loss from the shift away from dihedral canards?

Armchair aeronautical engineers can put up all the fantasy designs they want on the net, but they :

1. Do not have access to ALL the requirements put on the airframe
2. Do not have access to the modelling required to produce a viable platform
3. Do not have access to wind tunnels and anechoic chambers to assess the aerodynamic or VLO performance of their "designs"
4. Do not know all the specific technological limitations on the Chinese aero industry

So I'd call that "design" worthless when weighed against the considerations made by Dr. Yang Wei, his team or their predecessors at 611 institute which materialized into the J20 programme as we see it today.

 

[MiG-29SMT]

This right here is the problem with your analysis.

You keep trying to apply configurations from the Rafale onto the J20 just because they are both canard delta's. They have vastly different performance requirements. Performance requirements define the design compromises made on any airframe, not the other way around.

The Rafale was designed around being an "omnirole" aircraft. The J20's configuration is obviously "intended to provide good sustained supersonic cruise performance with a suitable engine type, and good manoeuvre performance in transonic and supersonic regimes" as Carlo Kopp puts it. This is clearly detailed in the study performed by Dr. Song and his team.

Even against the Typhoon, the Rafale cannot climb as fast, fly as high, retain speed as well or maneuver as well at transonic and supersonic speed.

Adopting the Rafale's configuration would cripple the J20's supersonic performance. Which is why I find it odd that you repeatedly bemoan that Chengdu didn't just copy Rafale's aerodynamics. The rafale's aerodynamic configuration is not synonymous with the interceptor role due to limits on its supersonic performance by the very canard configuration you advocate for.

The longer distance between canards and the leading edge of the wing translates to maximised maneuverability during supersonic flight with an air superiority load. Close coupled canards ala Rafale or the J10 are optimised for maximum lift generation and ordinance carrying capacity over a wider speed envelope.

The J10 or Rafale will never match the J20's performance in the supersonic flight envelope because of their aerodynamics. They will both struggle to retain speed when maneuvering because of their canard configuration vis-a-vis the J20 and Typhoon.

As to the position of the main wing, I believe you are versed enough to notice that this arrangement is clearly meant to minimise supersonic drag on the airframe. The modelling performed and detailed in Song's paper clearly show that this configuration (canard, LERX and lft body) maximised lift whilst minising overall drag on the airframe ie met their performance requirements. The wing wasn't "pushed aft", its there by design to meet performance requirements.



As to innovation, I believe anyone can see that the configuration chosen by 611 institute demonstrates a commitment to innovating to meet performance requirements whilst overcoming inherent restrictions (eg. engine thrust - until WS15's enter production). Not even going into their aircraft being the first stealth aircraft developed and produced outside of the US and Russia.

If you want a really low drag aircraft you make something like

Why then you need a canard?

to improve the delta wing.

The Rafale has a superior design and t is a more beautiful aircraft too.

The reason is Eurofighter needs vortex generators due to the very ineffective canards it has.

The lower drag of Eurofighter type of canard is not as effective as a tailless design like Drakken or F-16XL

So why J-20 has canards? simple the contradictions of the design are as follows:


low drag versus controlability?

You get lower drag with a compound double delta and higher stealth, but a Tailless has the disadvantage in pitch control since a higher lift flap deflection makes a pitch down movement, thus most aircraft have tailerons to avoid that disadvantage

The canard does not help it in stealth, specially since its dihedral breaks planforming.

Will it improve a lot over Rafale?

see the size of Rafale canards

It is obvious J-20 has bigger canards with respects its wing than Rafale so it does not seem they generate less drag

 

[scatterStorm]

If you want a really low drag aircraft you make something like

View attachment 49233

Why then you need a canard?

to improve the delta wing.

The Rafale has a superior design and t is a more beautiful aircraft too.

The reason is Eurofighter needs vortex generators due to the very ineffective canards it has.

The lower drag of Eurofighter type of canard is not as effective as a tailless design like Drakken or F-16XL

View attachment 49234

So why J-20 has canards? simple the contradictions of the design are as follows:


low drag versus controlability?

You get lower drag with a compound double delta and higher stealth, but a Tailless has the disadvantage in pitch control since a higher lift flap deflection makes a pitch down movement, thus most aircraft have tailerons to avoid that disadvantage

The canard does not help it in stealth, specially since its dihedral breaks planforming.

Will it improve a lot over Rafale?

see the size of Rafale canards

View attachment 49235


View attachment 49236

It is obvious J-20 has bigger canards with respects its wing than Rafale so it does not seem they generate less drag

Can you explain this dude, this giant ass Canard is just misaligned. Like you shown frontal aspect pictures already.

 

[MiG-29SMT]

Can you explain this dude, this giant ass Canard is just misaligned. Like you shown frontal aspect pictures already.

see the J-20 canard is so big even with the dihedral that its tip gets already deep into the leading edge of the wing

The J-20 due to the dihedral seem smaller but if they were coplanar and horizontal they would be closer to the wing tip

Rafale has control canards since most of the lift is generated by the wing.


The only reason J-20 is stealthier than Rafale is it carries weapons in weapons bays and twin tails, but Rafale is a much better aircraft in Aerodynamics

 

[scatterStorm]

Untrue. So far we've seen 2 layers of edge treatments. Images of the J20 in primer show either or both sawtooth paterns and composite stealth structures on all control surfaces:

In addition to the edge treatment, all access hatches and operating doors are sawtoothed and all apetures are edge-aligned as seen above.

The edge treatment on the J20 once painted in also obvious to see. The inlets, canards, LERX, wing leading edge, vertical stabilizers, tail booms and vertical fins are all treated.

Please provide the photos that show the untreated edges you allude to...

The APA modelling was done on the very 1st prototype shortly after its first flight; which is why it is a "preliminary assessment". There have been 3 iterative changes to the airframe since. Which is why they repeatedly allude to a "matured production airframe". Ofcourse the study has limitations judging by the fact that they do not have access to the actual airframe.



Exactly. So where do you hear him calling it a bomber? Large fuel capacity, good supersonic performance, LO airframe. Where does "bomber" come in? The F22 can carry 2 2000lb bombs or 8 SDB's internally but its never been called a bomber? I'm not even sure it has any cruise missiles integrated with it.

We've NEVER seen any kind of A2G ordinance on the J20. Even in its operations with J16's and J10's its always operated in an air superiority role to clear the way for A2G ladden J16's.

Your "bomber" assertions come with no evidence other that "its large". Well yeah, so is the SU35, but its not a bomber either. The performance requirements for the JXX programme have all pointed towards air superiority, not a bomber role. According to pentagon intel reports there are VLO strategic and regional bomber platforms in the works for the PLAAF.

Eventually the PLAAF will integrate a2g munitions on the J20 as the platform matures however, even being capable of undertaking SEAD or classic strike missions does not make it a "bomber".

Nice write up from Rick Joe from the diplomat below. I have a subscription, but I believe the first 5 articles are free or something.

https://thediplomat.com/2018/12/chinas-stealth-fighter-its-time-to-discuss-j-20s-agility/

1. Again, the FC31 is not a PLA sanctioned project yet.
2. In addtion, the FC31 does not have the same PERFORMANCE REQUIREMENTS as the JXX programme. its a medium-weight airframe with obviously a much smaller range.
3. The FC31 even if it where purchased by the PLAAF is not a successor or replacement for the J20. The VLO intecerpt and air superiority mission would still fall to the J20, so your point is moot
4. The losing bid for the JXX programme was a "conventional stealth airframe WITH CANARDS ie. the J20 met the requirements for stealth, supercruise, supersonic and transonic maneuvering better than the "conventional airframe".
5. Just like the operational SU57, F35 and the yet to fly AMCA and KFX, the J20 is not VLO in the rear aspect because it uses conventional engine nozzles which brings compromises to detection in the IR spectrum. J20, SU57 and F35 have RCS reduction measures applied in the rear aspect, but overall, I believe its quite telling that none of them went the F22 route. How much does it really impact operational viability in the air superiority role not to have full all aspect stealth? Is it worth the price and weight penalties?

Was this "proposed design" subjected to aerodynamic modelling and wind tunnel testing? Which studies support the implementation of such a design? What are the aerodynamic implications of changing the shape and size of the canards? And what are the aerodynamic implications of placing the wings there? What are the weight penalties of using that nozzle arrangement and which engines will compensate for that weight with additional thrust? What with the abnormal placement of the vertical stabilizers? How will this design compensate for Yaw instability created by removing the vental fins? How does this model overcome the penalty of lift loss from the shift away from dihedral canards?

Armchair aeronautical engineers can put up all the fantasy designs they want on the net, but they :

1. Do not have access to ALL the requirements put on the airframe
2. Do not have access to the modelling required to produce a viable platform
3. Do not have access to wind tunnels and anechoic chambers to assess the aerodynamic or VLO performance of their "designs"
4. Do not know all the specific technological limitations on the Chinese aero industry

So I'd call that "design" worthless when weighed against the considerations made by Dr. Yang Wei, his team or their predecessors at 611 institute which materialized into the J20 programme as we see it today.

Counter to point 1: (read carefully this time)

Canards torque arm have gaps. While moving those canards, radar waves will eventually get deflected by a large curved object that's.

Misaligned Canard, not conforming to frontal planner form.

Tell me are they aligned to wing root? Untrue.

The underwing bulged control surface actuator (nice round shape). (see below)

Counterbalancing stealth using radio-spectrum-airfoil & its limitations to the fighter jet:

So you've reduced backscatter through sawtooth edge treatment, done some paint job so specular reflections are covered and surface em waves covered?

What about Mie scattering for which newer radars such as this one is developed for, exploiting's the resonance regions of a stealth jet?

"That why I said this model is not tested for real world conditions".

Infact, the emphasis on radio-spectrum-airfoils (stealth) for fighters and for reduced drag - can force:

• Internal weapon bays / carriage restrictions. (Check for J20)
• Reduced space for internal fuel. (Check for J20)
• Which force increased aircraft size / or the use of external tanks. (Check J20)
• All bad for "the element of surprise" Stealth's hallmark feature.

Draw down to Mie Scattering:

"As the radar wavelength grows, non-specular reflections intensify and specular reflections widen. For flat surfaces, traveling waves grow with the square of wavelength and their angle of peak backscatter rises with the square root of wavelength: at 1/10th the surface length, it is over 15 deg. Tip diffractions and edge waves from facets viewed diagonally also grow with the square of wavelength. Specular reflections from flat surfaces decrease with the square of the wavelength, but widen proportionally: at 1/10th the surface length, they are almost 6 deg. wide. In addition, most RAM types become less effective as wavelength increases. For all these reasons, stealth specialists say the RCS of a stealth aircraft grows approximately with the square of wavelength from the lowest frequency for which it was designed, and that above-mentioned effects become significant when the wavelength reaches about 1/10th the size of a structure.

this regime —where the wavelength is between one and 1/10th the size of the structure—is known as the “resonance region.” Maximum RCS is often reached when the wavelength reaches the approximate size of the structure. "

Counter to your point no 2:

So where do you hear him calling it a bomber?

Never said, he called it a bomber. I was putting the point to why its LO rather than VLO.

@MiG-29SMT posted a J20 with a pylon, with supersonic fuel EDT.

Now why do we do that on a "so called stealth jet"? If this huge jet cannot take ATGMs in its IWB, than it can surely carry on its pylons, a subsonic ATGMs. Since munitions are still developing, is highly likely, that it would carry a subsonic cruise missile, supersonic cruise missile or ATGM payloads.

"With its LO (stealthy) characteristics, it will eventually become a swing-role supersonic LO bomber fighter jet confining to the mission parameters of Mirage 2000 like fighter jet".

Counter to your Point no. 3: FC-31 and its shenanigan's.

FC-31 is now being funded partially funded by PLAAF (unofficially). Its happening, as much as you deny it, its literally on the table. To provide weight here are some questions, Why the marketing? Why on this dudes desk? With a PLAAF army logo?

Now you would say, so what its a model, to which my argument is simply, why put models just for show, because you are marketing it already to the PLAAF.

Ok you are still not convinced then, a full gray paint job with a pitot tube would suffice and its a fairly recent one, I am pretty sure you have it seen already

FC31 is VLO and would enter in both for airforce and navy roles, much like the F35B and F35C variants.

I can clearly see that this jet was designed for VLO, rear end not much because of the engine technology which is understandable. In fact, it has taken lesson from J20 and improved upon it. All it requires damn good engines.

Conclusion:

1. J20 is LO jet, a "stealthy jet" for what SU57 is also mocked for by western BS media.

"However, SU57 is clearly a thought out technology, that's why I say "Russians had very different mission parameters stated for it, to counter F35 and F22".

2. J20 isn't a stealth jet (VLO), not much data is available for its EW capabilities which also adds to the stealthy characteristics of a jet. Much of the armaments are still in development, and we might see ATGMs for it.

"Hence its role for stealth is unclear".

3. J20 Mission parameter as you clearly stated,

"Do confine to regimes such as maneuverability, Long range endurance, air superiority fighter jet."

4. I would add my speculations as well,

"Swing-role, fighter bomber".