Yeah, you really have a unique way of pointing out my many mistakes:

you should pay attention to how the debate stated , i said from start that even with low frequency, radar still need to be positioned at certain direction to detect stealth fighter : Laurie Hilditch ( Eurofighter’s head of the future requirements capture) , Professor Oleg I. Sukharevsky , American institute of Aeronautics and Astronautics , Professor Yakov D. Shirman. 2001 ,and computer simulation all agree with my assessment that stealth fighter can still achived low frontal RCS again low frequency radar
http://forum.keypublishing.com/showthread.php?135977-Su-35-versus-F-35-in-command-sim/page8

Still no explanation why your squares don’t match the whole X-axis? K.

it matched now , happy ? 😉 , doesn’t make any different at all , it still show that you dont know how to read a simple graph
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Anyways, I’ve e-mailed Marcelo Bender Perotoni, Luiz Alberto de Andrade, Mirabel Cerqueira Rezende,

should have explained to others that these are guy who did the simulation you cited ,otherwise they may thing you listing name of very famous people :rolleyes:

Eugene F. Knott, John Shaeffer, Michael Tuley the management of Northrop Grumman and last (but not least) Edward ‘Radarman’ Lovick Jr. to say they have all been *corrected*. I’m sure, like myself, they’ll really appreciate your knowledgeable efforts.

which one of them stated frontal RCS of stealth aircraft will increased by 20-30 dBsm at low frequency such as L band ?

:highly_amused: :highly_amused: COME BACK Mr. ActionJackson!!! ALL IS FORGIVEN!!!

you truely believed fighter will have exactly same RCS from all angle ? really?
here are some simulation that show otherwise

even missiles like Aim-9 will have massive RCS from certain angle

RCS of some stealth aircraft at S band without RAM



XB-70 RCS

So much blah, blah, blah and not a single answer of any substance. No answers because you don’t have any.

actually, i pointed out many of your mistakes such as reading graph wrong
why stealth aircraft have very high RCS from these aspect you ask ? because from these aspect the wing sweep is perpendicular to the radar direction of travel

The graphs & charts I read every day are very different to the ones you come across in high school. Btw, speaking of “nice tries” why don’t your squares match further down the x-axis? Hmmm…

then you should understand the basic of “how people connect point on graph”

Did you even consider for one moment how your beloved ug stealth plane is going to fly, fight and survive with a beam aspect of 100m^2 (20dB) @ 10GHz??! That’s the same as a B-52!! Was that in the RFP too?!:highly_amused:

1) it a beam aspect with narrow angle , because the aircraft is constantly moving , that beam aspect will be shown to enemy for a very short amount of time, stealth aircraft can have side RCS of thousands square meters and it still doesn’t matter , the thing that mater the most is frontal aspect
2) aircraft havent been treated with RAM
3) RFP only mentioned frontal aspect

4) and unless your aircraft is a sphere , it wont have low RCS from all aspect

It’s like explaining to a child. I have NEVER claimed 40dBsm* – it is you who has claimed I did (slanderously). But if that measly point means so much to you in the face of your laughable understanding of the subject, then by all means e-mail the dude for clarification over that anomaly.

the simulation have been your main point ,and i pointed out the mistake in it , if it make such big obvious mistake then the accuracy of he other part of the simulation are questionable

Incidentally, does your line not strike 18dB first?

actually no ,not all , do you know why ?
because in their graph , they connected the point below 2 Ghz (-10dBsm ) with that 40 dBsm point , instead of the 18 dBsm point,
do you even know how to read a graph ?

You cannot knock down what I originally posted so easily:

Nice try but 200 MHz to 600 MHz isnt L band , and have nothing to do with discussion from the start , the ” ~20dBsm is confirmed in other literature” is about L band , all others simulation posted from start didn’t go bellow 1 Ghz

So your beloved undergraduate study achieved 10m^2 @ L-band compared to 100m^2 shown by Professor Oleg I. Sukharevsky. So is the Professor a liar?

Have the undisputed ‘Kings of Stealth’ (Northrop) made an absolute stinker with the B2 and been bettered by an undergraduate? Only one of the two is a ‘broadband’ stealth design, can you guess which? Do you even know what is meant by broadband stealth? Where are the computational electromagnetic studies to back up the ug’s claims?

That’s too many questions for you, just explain this:

Undergraduate study/ notional stealth striker = 10m^2 @ 1GHz

Professor Oleg I. Sukharevsky/ Northrop B-2 = 100m^2 @ 1 GHz.

nice try Sakura , you take a single RCS value at very narrow aspect and tried to claim that is the B-2 RCS at 1 Ghz :highly_amused: ,but you know what funny? if you actually paying attention , the undergraduate study also showed massive RCS from exactly the same aspect , also reached 20 dBsm (aka 100 m2 )
however both design still showed relative small frontal RCS at 1 Ghz

Nothing confusing about a B-2 plot of 100m^2 @ 1GHz, buddy (from your post btw):

‘Oh-oh-spaghettios’!!…and still at least 10x more reflective from the more discrete aspects!

Concurring quite well with the 18-20dBsm increase for 1GHz stated by industry academics & professionals (at least in the worst offending regions).

Also kinda runs riot with your attempts to portray a 10GHz plot that closely matches a 1 GHz plot for a (non-stealth) MiG-29 as directly extrapolating for the notional stealth bomber from your linked undergraduate ‘study’.

the only place where B-2 get the huge RCS of 100m2 is at it’s worst aspect ( 30 degree off boresight), from most important aspects ( aka frontal) the different between 1Ghz and 10 Ghz is around 10 dBsm for B-2 and all other aircraft, missiles that were put in simulation

the poster here who can’t tell the difference between 18 and 40dBsm).

ok Jo, you take a ruler and draw a line from the 40dBsm point down, and see for yourself where it touch

i can assure you the point is 1Ghz
the line between 1Ghz and 2Ghz is irrelevant since they only connected the point between 1Ghz and 2Ghz without simulated it

Lastly, most stealth aircraft have RCS spikes, but these are engineered so it’s towards the 90 degree angle; i.e, you’re never going to be able to keep a fighter on the 90 degree aspect angle. Most RCS spikes are also relatively mild, the 2001 J-20 according to Kopp is the only stealth aircraft that has a -10 to -0 dBsm zone in the frontal sector; the F-22 and PAK-FA seems capable of having -40 dBsm in the frontal sector, while the F-35 only has -20 dBsm in the frontal sector. You’ve just as well seen the polar chart as I have; it’s a huge area where you have frontal returns.

Can you post the study and the graphics where they show PAK-FA and F-22 achieved -40 dBsm in frontal sector while F-35 limited to -20 dBsm?
was the simulation with or without RAM? , i would assume that value is without RAM since there is no way they would know the absorbing characteristics of these aircraft ‘s RAM
and not all RAM have similar absorbing characteristics
some work well at high frequency , ithers work well at low frequency

Perhaps Kopp will redo the RCS chart once the J-20 hits IOC, and with the adjustments to the LERXes and the refinements the J-20 might be comparable to the F-35 in the frontal sector.

Kopp really isn’t a reliable source, his analysis always affected too much by his opinion, agenda

S
@ mig-31:

DSI doesn’t necessarily mean the aircraft can’t supercruise,

i mean DSI isn’t optimum for high speed ( because it not flexible and possible to design a fixed intake that works well both in dogfight speed and mach 2.5, above) , especially with the DSI exactly the same as F-35, J-20 will loss quite a lot of thrust at speed > mach 1.4-1.5, with quite weak engine i dont see how it can fly past mach 2.5, let alone mach 2.8 like the PDF files that MSphere posted suggest

for instance, there are claims that the F-35A can supercruise around Mach 1.3 under certain weight conditions that are combat impractical.

yeah, there was claim that F-35 can fly supersonic for 150 miles at mach 1.2 without reheat, but that the only infor we have, the rest are all speculation

The point of DSI is that it’s non-adjustable, DSI can be optimized for a specific Mach number, above and below which performance begins to suffer, but that Mach number can be supersonic.

The problem is J-20 DSI is similar ( if not exactly the same as F-35) , if it was built to fly at mach 2.5-2.8 for long distance then the DSI intake should be quite narrower

The reason I assume that the aircraft is built for speed is because of the high aspect ratio of the aircraft; the ratio of wingspan to length is higher than in many other aircraft, and the sweep of the wings is higher than in the PAK-FA and the F-22, not to say the F-35

.

Mirage all versions have better aspects ratio and wing sweep than F-22, Mig-31, Mig-25, F-15 and it is still slower than all of them

By contrast Bell X-1 have trapezium wing and have hit mach 3 before
what really important for speed is the intake and engine design

About the wing loading, as mentioned before, the J-20 has less internal volume than the PAK-FA, and even high estimates of the J-20’s 100% fuel weight is around 34,000 kg. Assuming 78 m^2 wing area, that comes down to 425 kg/m^2, which is still superior to the F-35; if the weight is lower and it’s closer to the F-22 (length * wingspan is roughly the same as the F-22), it can have around 375 kg/m^2. In either case, it’s better than the F-35A, which has an incredible 600 kg/m^2 wing loading at 100% fuel.

they are aircraft of different weight and have different drag, and use different engine thus they will need very different amounts of fuel for same distance, or same time on afterburner, carry weapons also affected them differently

About the AESA jamming; any sufficiently advanced and powerful radar is capable of jamming by focusing its beam on enemy radars. The F-22’s radar can be upgraded for similar features, and the J-20 can have jamming built into its radar as well

up until now, only APG-81 have tested that jamming capabilities, sure in far future, there will be a point when all AESA radar will have that ability, however at the moment and near future that still an advantage that F-35 have
anyway, jamming or not, my point is it very unlikely that Stealth fighter will detect others from any significant distance by radar ( sure radar will get more powerful im future but so is jamming, and low RCS just make jamming alot more effective )

I do agree with many other posters, though, that WVR maneuverability doesn’t matter anymore with modern HOBS missiles (which the Chinese also have)

for this i agree, i think WVR dogfight is a dangerous place to be when everyone start getting their HMD and HOBS missiles

Oh yes we do:

that mean little without knowing altitude, fuel load and weapons load, a slow aircraft at low altitude can turn much faster ( much higher turn rate) with far less G needed compare to something that
moving high and fast

From where did you pull that? the same place you got the idea L-band is ineffective against stealth?

dont try to bend my words Sakura.
i didn’t said L band isn’t effective again stealth, in fact i even said Stealth is less effective at low frequency, however, low frequency isn’t magic, the F-22 won’t suddenly have RCS of 10000 m2 at L band like you suggested, anyway that belong to another topic, let not derail this one

Whatever the variations in DSI design (primarily bump, intake lip & area), performance deficiencies don’t kick in ’till post M1.3 and later depending on the individual design characteristics.

To supercruise at mach 1.8 and have top speed of mach2.8 like ins suggests, J-20 would need very different intake from the one it have now

One thing I don’t get is why the J-20 is expected to be less maneuverable than the F-35 in certain regimes. Engine power is between 125kn to 135kn, if you consider the latest AL-31s provided by the Russians to the Chinese, thrust to weight could possibly be lower, depending on how much the aircraft turns out to weigh, but it has canards to compensate in subsonic regimes and has been shown to have around 20 degree sustained turn rate and 30 degrees instantaneous turn rate at low speeds. Not excellent, but good enough, if you compare it to the F-35.

you dont even know the turn rate at slow speed of F-35
also the amount of fuel and altitude will make significant difference to turn rate

I mean, if you want to bash the J-20 as mediocre, be my guest; it’s built more for high-speed interception and high-speed maneuverability

why do you assuming it was buit for high speed maneuver or high speed?

. The unimaginable thing is that you’re claiming that the F-35 is superior to the J-20 when both, according to estimates, are RCS -40 dBsm craft on off direct bore,

can you cite that study?

the J-20 has a larger radar

only by a little bit, and to be fair it would make little to know different since both have very low RCS that allows them to even hide from AWACS and massive ground SAM radar, F-35’s APG-81 also have ability to jam enemy’s radar

is built for supercruise,

I dont think so, it may be able to supercruise, or it may not, but i dont really see any features that show it optimum to supercruise
: weak engine, canards, DSI intake

The F-35 consistently loses in dogfights against 4th gens, the J-20 isn’t the most maneuverable aircraft but it’s competent compared to most 4th gens.

last time i heard, F-35 only done dogfight exercise with F-16 and that dogfight was only to asset how control software react at max AoA
what 4 gen that J-20 done dogfight exercise with?

Other issues are, the J-20 seems to have a higher potential max Mach number (a Virginia Tech simulation by Americans using mostly accurate size estimates claimed that the J-20 will have max Mach 2.85 with proper engines and max Mach 2.1 with present engines),

can you cite that study?
it pretty much sounds like BS to me, a bit more thrust ( 20-25%) wont increase speed that much, the importance factor is how much thrust the engine will lose at high speed, since J-20 use a DSI style intake, i really doubt that it can even reach mach 2

its wing area using Lockheed-style body lift is around 78-80 m^2, comparable to the F-22 and far superior to the F-35…
.

you cannot compared lift and ignore the weight figure , if you just compare the wing area then something like B-2 would be superior to everything else