J-20 5th Gen Fighter Thread V

[zaphd]

I don't think that's correct, actually. Underpowered as the J-20 may be, if the airframe is designed to supercruise at standard load, there should be some fuel load in which it's T:W ratio is equal to what its T:W ratio would have been at standard load. That means the current J-20s should be able to supercruise, though they may not be able to reach the top supercruise speeds they were designed for with WS-15s.

It's not only about T:W ratio. That argument would hold if you had only lift induced drag, but at supersonic speeds you have stuff like wave drag, which doesn't depend on weight. It's a highly unlinear situation.

 

[latenlazy]

It's not only about T:W ratio. That argument would hold if you had only lift induced drag, but at supersonic speeds you have stuff like wave drag, which doesn't depend on weight. It's a highly unlinear situation.

Yes, but if the plane is designed for supercruise, then induced drag isn't the limiting factor.

 

[Hyperwarp]

I don't think that's correct, actually. Underpowered as the J-20 may be, if the airframe is designed to supercruise at standard load, there should be some fuel load in which it's T:W ratio is equal to what its T:W ratio would have been at standard load. That means the current J-20s should be able to supercruise, though they may not be able to reach the top supercruise speeds they were designed for with WS-15s.

Its not just about the T/W ratio. It depends on how draggy the J-20 design is. An example would be YF-22 vs YF-23. Despite the same engines the YF-23 was much better at supercrusing.

Lot depends on the dry thrust of the engine. F119 officially can produce at least 155kN in full afterburner. Unofficially it is even higher. Dry thrust is lower but I've heard rumors that the F119 can produce as much thrust as a AL-31F in full afterburner. About 115kN - 120 kN dry vs the 122kN of the AL-31F in full AB. In-contrast the 117S can produce only 86kN max dry thrust and its not clear how long it can sustain that. We don't know how much max dry thrust the current Salut engines can produce.

The EF, Rafale, Gripen can supercruise at around Mach 1.2 with 4 AAM. EF can supercruise with 2x ASRAAM + 4x AMRAAM and one centerline drop tank. But remember these are much smaller planes and shorter range. We don't know the exact supercruise values for the Su-35S either. How much and how long can is supercruise with 8x AAM hanging from the pylon and that assuming it actually can.

 

[latenlazy]

Its not just about the T/W ratio. It depends on how draggy the J-20 design is. An example would be YF-22 vs YF-23. Despite the same engines the YF-23 was much better at supercrusing.

Lot depends on the dry thrust of the engine. F119 officially can produce at least 155kN in full afterburner. Unofficially it is even higher. Dry thrust is lower but I've heard rumors that the F119 can produce as much thrust as a AL-31F in full afterburner. About 115kN - 120 kN dry vs the 122kN of the AL-31F in full AB. In-contrast the 117S can produce only 86kN max dry thrust and its not clear how long it can sustain that. We don't know how much max dry thrust the current Salut engines can produce.

The EF, Rafale, Gripen can supercruise at around Mach 1.2 with 4 AAM. EF can supercruise with 2x ASRAAM + 4x AMRAAM and one centerline drop tank. But remember these are much smaller planes and shorter range. We don't know the exact supercruise values for the Su-35S either. How much and how long can is supercruise with 8x AAM hanging from the pylon and that assuming it actually can.

Again, if the J-20 is designed for supercruise, then the limiting factor isn't induced drag, but T:W ratio, which changes with fuel load. In so far as we care about thrust, it is through how thrust acts on mass.

 

[Hyperwarp]

Again, if the J-20 is designed for supercruise, then the limiting factor isn't induced drag, but T:W ratio, which changes with fuel load. In so far as we care about thrust, it is through how thrust acts on mass.

Lets do a crude, unscientific calculation. Lets use the F-22 with F119 and J-20 with 117S. I am using the 117S because we know the dry thrust.

Assuming max dry thrust of the F119 to 120kN (probably higher) and max supercruise of Mach 1.7-1.8. The max dry thrust of the 117S is 86kN.

Now the BIG IFs! Assuming drag is irrelevant and the F-22 and J-20 weighs the same, then the theoretical max supercruise for the J-20 will be around Mach 1.2 - 1.3 at most. But we do not know the weight of the J-20. J-20 is larger than the F-22.

 

[taxiya]

i will tell you my opinion.

CNN is not completely wrong, the canards, the ventral fins, the nozzles are less stealthy than the F-22 you like it or not you accept it or not.
In that i think the J-31 is the better fighter.

The jet is large, it is between 20.5 to 21.5 meters, its engines lack TVC nozzles, so it canards flap like crazy, very likely it has Al-31FNs, so it is underpowered.
Now this is a fact anyone outside the Chinese community will see right away.

Now is avionics is another thing, the jet might pack advanced avionics, the american general is just guessing, perhaps with some good intel but i doubt he knows the kind of systems J-20 has, so here i agree, no one knows what radar or avionics it has.
The Chinese brass also will say the J-20 is wonderful, like most of you do say.


CNN says something many say, the larger size of J-20 means it carries more fuel, that is excellent if you consider it needs to fly like the AM-6 over large expanses of ocean.

Why the J-20 is larger? first the canard was set far ahead of the wing because the weapons bay demanded a longer fuselage and the canard had no way it could be set above wing level the wing also was set far aft to improve the supersonic aerodynamics by reducing the cross section of the engine nacelles, so it has the shape of a strong person, the intakes are like broad shoulders, but the legs are thinner

The ventral fins are something more interesting, they are unwanted reflectors, and even worse they are canted too, they are not canted by aerodynamic reasons, but by stealth reasons.


So you like it or not the flight displays you have seen lack post stall, when have we seen it? never, despite here people present the regular turns as incredibly agile the jet has not shown post stall, and without TVC means limits in cruise flight F-22 and PAKFA do not lack, in terms of flight control, plus the canards are huge.

So regardless what you say the F-22 continues to be the best over all aerodynamics/stealth blend aircraft, if you look at the transition of the flat sides of the weapons bays and the engines nacellles, sorry to say this but J-20 has a poor job done, look at F-22 and the transition is smooth, the mid wing on F-22 blends nicely, on J-20 it does not.


but well i know you will not accept it, so over-hype J-20, J-31 will be the better fighter once it gets a better engine, and China will not abandon the J-31, that is the better fighter, it only needs a better engine

Hi b787, as you always do, again this time you stretched my post to fit your thought, or inserted your imagination to my mouth.

Did I say anything (agree or disagree) about that CNN article? No, I did not. I was purely commenting about CNN's credibility and ethics regardless their words based on my past experience. If the same words were said by somebody else, I will give more considerations. But from CNN, No. It's just that.

 

[shen]

The J-20 has two huge bulges on each side of the inlets, the DSI bulge, this is huge, thus forcing the intake mouth to be a wide gap too, this increases the cross section, the intake is followed by the weapons bays, this increases the area of the frontal cross section, thus the engine nacelles change abrutly from a trapezoidal to a circular shape, this increases the size of the J-20 fuselage, F-22 manages to fit the same engine weapons bay in a smaller and shorter fuselage and the booms are well blended, the J-20, could not do that, thus the transition from the trapezoidal cross section of the intakes and weapons bay to the circular cross section of the engine nacelles has not a smooth transition, J-31 in that is much better, the J-31 only is inferior to J-20 because both jets use old engines but RD-33 do not have a supercruise version neither can carry lots of fuel, thus the PLAAF will prioritize the larger aircraft because of range, in the same way Russia prioritized Su-27 over MiG-29, but the better aircraft is J-31 and F-22 is a much better approach to area ruling because flat nozzles are lower drag solution.

The J-31 if it has the right engine, will be a better fighter than J-20, J-20 is overhyped because is the larger jet and in long range missions is a better option flying over sea or land

Don't know what you are talking about. Narrow waist of area ruled aircraft is not to compensate for the bugle of intakes. Narrow waist is compensating for the wings, which is always the widest part. Intake bulges is in fact often used as a component of area ruling. Compare the original F-102 design (not the production model) vs the fully area ruled F-106.

F-22 is not a great example of area ruled airframe either. F-35 is a much better example, necessary due to lower thrust to weight ratio, the same reason J-20

 

[taxiya]

If you want people to believe your confident claims give actual cross section areas.

i can assure you J-20 has a length no shorter than 20.5 meters and a Max of 21.5, it has a canopy of almost the same size of F-22`s but a much larger forebody cross section by the large bulges, this for a regular person will give you a good idea of how massive the jet is, but be my guess think it is small, and just 30 cm longer than F-22 i am laughing a lot, at how CNN is saying what most people with some criteria say, but fans neglect to see and dig their head on the ground thinking the jet is small, ventral fins are good, the aft section of the engines are stealthy and canards are good for stealth specially without TVC nozzles

Latenlazy asked "cross section", and you answered "length". If I ask you color, you will tell me it is cold?

Please stop your usual practice of distraction, changing subject, diversion, twisting other's meaning, goal-post moving etc. etc. It does not look smart on you and it is a torture of the rest of us. May all Gods of all human-beings have mercy on all of us including you.

 

[Air Force Brat]

You're spot on here son, and I am in 150% agreement with you, and furthermore, I still do NOT believe China is going to thow away money to buy SU-35s, when they have NO real interest in OVT, and they build better Flankers anyway??? just my honest opinion?? if I'm wrong about the SU-35s I will issue a public apology and retraction. Brat

 

[vesicles]

You're spot on here son, and I am in 150% agreement with you, and furthermore, I still do NOT believe China is going to thow away money to buy SU-35s, when they have NO real interest in OVT, and they build better Flankers anyway??? just my honest opinion?? if I'm wrong about the SU-35s I will issue a public apology and retraction. Brat

Amen to that! The Chinese officials have not said a single thing about it. I will accept it when I see the Su-35 in PLAAF color.

I will sign that apology form with Brat if that ever happens... I am totally fine with it since I have been wrong plenty times in my life. In fact, I have been wrong way more than when I've been right.

Even IF the PLAAF will buy the Su-35 in the future, I still do not think it is the right thing to do. I still maintain that they should tough it out on their own. It's not about pride or ego. It's about throwing away the crutches and be on your own.