J-20 5th Gen Fighter Thread V

[b787]

And the DSI on the F-35 is stealthy ???

Come on ... were are back again right in a discussion we already had so often and since no-one really knows that stuff, these arguments are more or less baseless ..

Deino

is not stealth what i was talking, but drag, a larger frontal cross section will require an Whitcomb area rule on the nacelles, the solutions varied on J-31, F-22, J-20 and F-35, but J-20 has a very large frontal cross section in the intake and forebody section, the bulges of the DSI are big, and the length of the intake engine section of F-22 is much shorter than the J-20`s intake and engine length, this is a direct result of the position taken by the canard and the overall dimensions of the engines and cavities of each aircraft.

It is not subjective, because F-22 super cruises at speeds of Mach 1.8 and has flat nozzles well known to have lower drag than round nozzles

 

[latenlazy]

is not stealth what i was talking, but drag, a larger frontal cross section will require an Whitcomb area rule on the nacelles, the solutions varied on J-31, F-22, J-20 and F-35, but J-20 has a very large frontal cross section in the intake and forebody section, the bulges of the DSI are big, and the length of the intake engine section of F-22 is much shorter than the J-20`s intake and engine length, this is a direct result of the position taken by the canard and the overall dimensions of the engines and cavities of each aircraft.

It is not subjective, because F-22 super cruises at speeds of Mach 1.8 and has flat nozzles well known to have lower drag than round nozzles

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

 

[b787]

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]

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

I don't dispute the estimated length, but I asked for cross sectional area figures to back your claims that the J-20 has a bigger cross section, which you still haven't provided. No amount of cheap eyeballing substitutes for actual measurements.

Also Whitcomb area rule follows a ratio. That means the actual cross section area doesn't matter. What matters is the cross section distraction to length ratio.

 

[Hyperwarp]

....

It is not subjective, because F-22 super cruises at speeds of Mach 1.8 and has flat nozzles well known to have lower drag than round nozzles

I don't think anyone disputes the F-22s supremacy. The ATF supercruise requirement of Mach 1.58 was exceeded by at least 15% by the F-22. There is no match anywhere in world when it comes to Stealth and Supercruise capability of the Raptor.

If those 117S of the Su-35 goes to the J-20 (which I doubt) and/or even if they manage to reverse engineer the 117S (which will take hell of a long time) it is not going to change much against an F-22 supercruising at Mach 1.7+ and at over 60,000 ft.

 

[Richard Santos]

is not stealth what i was talking, but drag, a larger frontal cross section will require an Whitcomb area rule on the nacelles, the solutions varied on J-31, F-22, J-20 and F-35, but J-20 has a very large frontal cross section in the intake and forebody section, the bulges of the DSI are big, and the length of the intake engine section of F-22 is much shorter than the J-20`s intake and engine length, this is a direct result of the position taken by the canard and the overall dimensions of the engines and cavities of each aircraft.

It is not subjective, because F-22 super cruises at speeds of Mach 1.8 and has flat nozzles well known to have lower drag than round nozzles

Flat nozzles having lower drag is unknown to me. Appearently unknown to every other engine, jet or rocket, that has round nozzles either. But the flat TVC nozzle on the f22 is known to be very heavy, and thus bringing the thrust to weight ratio of an otherwise exceptionally advanced f119 engine back down to something similar to the previous generation of engines, such as those on the f15 and su27. and it also materially reduce the exhaust efficiency of the engine compare to an axial symmetrical nozzle.

Through the flat TVC nozzle the F22 sacraficed a lot on the altar of thrust vectoring and higher nozzle stealthiness.

 

[Engineer]

thiis is the funny aspect of this forum you get the funniest explanations in order to avoid reality.

Face it, J-20 still is in a development stage with some limitations, it has no Al-31F-2, it has limitation its engines are old Al-31s, they gave estrange solutions like ventral fins, but not here these are smart solutions.

This is the funny aspect of this guy, giving the funniest explanation to avoid reality. Face it, J-20 is already in LRIP, meaning development is done despite not using WS-15. Your beloved PAKFA is not yet in LRIP even with its half-baked 117S engines. Quit projecting your own insecurities on other people.

Furthermore, ventral fin is acknowledged as the best in achieving lateral stability. The reason it isn't used often is because such fin interferes with the ground during take-offs and landings. Such information can readily be found in basic flight dynamics text books. Using ventral fins is actually smart design. Using sophisticated and heavy machineries to do something that can be achieved with no moving-part is bad design.

PAKFA like J-20 are in some way alike, their designers accepted some aerodynamic concessions are worth using them if they help, on J-20 they sacrificed stealth, the F-22 with its flat nozzles and booms blends the fuselage smoothly and stealth was not sacrificed, on J-20 the ventral fins help the jet at high AoA because it does not use TVC as substitute for aerodynamic controls, the end result is a wing aft strake thinner where the ventral fins are set, a good solution for its wing design since a thin wing is better for high speed, however the fuselage transition from a flat surface cross section of the weapons bay and the rounded engine nacelles was poorly made having a zig zag shape.

J-20 and F-22 are nothing alike to the PAKFA. PAKFA lacks an internal weapon bay and is not a true stealth fighter.

Also, just because designers of PAKFA have trouble balancing multiple requirements without making large concessions, that doesn't mean everyone has to do the same thing. Designers of F-22 and J-20 achieved more with less concessions because the designers had better resources available.

The jet still will need the 117 of Su-35 if it wants to go supersonic without afterburner, without the 117, or even ws-15 J-20 is like the F-14A with TF-30 or early Su-27s with Al-21s.
But of course all is charity in the alternate reality

So say the Russian fantasy. First, we were told that China wanted Su-35 to compete with F-22. Then, J-20 appears, and we told that J-20 needs 117S engines and that's why China wants Su-35. Now, with J-20 went into LRIP and began service, we are being told that China wants Su-35 for Russian languages on flight displays. Talk about giving funniest explanations in order to avoid reality.

 

[Engineer]

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...

That's not how cross-section works. The bulge and the intake do not even lie on the same plane!

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.

That's not how area-ruling works. Longer fuselage is actually better for area-ruling, because it allows cross-sectional area to vary more smoothly thus achieving lower-drag. This idea is summarized in a term known as fineness-ratio. You argued for the exact opposite -- the opposite to Laws of Physics.

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

Any aircraft is better with better engines. Even J-20 will be better than current J-20 with better engines. That doesn't mean J-31 is better.

 

[siegecrossbow]

There are rumors that the J-20 might perform again between the 4th and the 6th. Fingers crossed folks!

 

[b787]

Flat nozzles having lower drag is unknown to me. Appearently unknown to every other engine, jet or rocket, that has round nozzles either. But the flat TVC nozzle on the f22 is known to be very heavy, and thus bringing the thrust to weight ratio of an otherwise exceptionally advanced f119 engine back down to something similar to the previous generation of engines, such as those on the f15 and su27. and it also materially reduce the exhaust efficiency of the engine compare to an axial symmetrical nozzle.

Through the flat TVC nozzle the F22 sacraficed a lot on the altar of thrust vectoring and higher nozzle stealthiness.

you are correct the F-22 sacrifices thrust for lower IR signature and lower fuselage nozzles drag, most rockets or engines will not sacrifice thrust, but consider F119 has more thrust available than any engine outthere except f135, and has a thrust to weight ratio no engine can offer, so F-22 will supercruise at Mach 1.7 and this will be done at lower IR and drag than any other aircraft including PAKFA or Eurofighter