milosh wrote:Yes Russians go with stealth proven direction (something between F-22 and F-23):


while J-20:

doesn't look nothing like F-22/23
We can argue about small order for Su-57 but saying it isn't design as stealth airframe is nonsense.
The Su-57 may look like a good example for stealth shaping but when looked at more closely, it has designs features that compromise what could be an outstanding LO design.
Pretty sure we've discussed here before but I will reiterate...
Its IRST is an obvious give away.
The F-35's EOTS is both faceted and treated with radar absorbent properties.

The Chinese J-20 takes cue from the F-35 in mimicing the design...

Despite the F-117 having a round node for its FLIR, and being limited by computer modeling at the time; it was buried, hidden inside a faceted compartment, and had a angled cover also treated with RAM


When looked at from the side the FLIR housing for the F-117 appears flush with the outline of the aircraft.

The same cannot be said of the Su-57. While others have claimed it is treated with RAM, its shape is not the most opitimal nor is its placement on the aircraft.

Another thing that stands out that comprises its stealth is its engine nacelle design. Both F-22 and J-20 attempt to have a flush, smooth, and uniform fuselage to reduce their RCS.
F-22

J-20

The YF-23 has a relatively flat and smooth surface

The Su-57 on the other has seperated engine nacelles offer more reflective surfaces for radar waves


If the J-20's canards are detrimental to a stealthy design, than so is the Su-57's movable LEVCONs...

The F-35 and F-22 both have IR sensor nodes enabling full spherical 360 coverage. The F-22's AN/AAR-56 and F-35's DAS are flush with the aircraft's outer mold. The same however cannot be said of the Su-57's DIRCM nodes...

Finally the engine inlet/intake design. Recent photos of the "first" production version of the Su-57. They show a radar blocker to reduce radar return similar to the F/A-18 Super Hornet...


While this is a simple way to reduce visibility of the engine to a radar, it is not the most effect means. The F-22 and F-35 engines are buried deep within the aircraft in complex S (for F-22) and Y (for F-35) intakes. At no point are the engine faces of the F-22 and F-35 visible.
Others have attempted to compare the Su-57's inlet/intake design to the YF-23. The major difference is how much deeper and more curved the YF-23's inlet/intake is.

So
NO, the Su-57
DOES NOT take design cues or have similarities to F-22 or YF-23. From a purely visual observation the J-20 has design similar to or same features to F-22 and F-35. The J-20's nose and fuselage look similar to F-22. The J-20 has DSI like the F-35 as well as vertical tail shape. The Su-57 on the other hand looks like a flatened Flanker with IWBs. If I was going to give the Su-57 a NATO code name I would have called it "flapjack".