Technical reply to issues raised by Angeldemon_007.
1. Su-30 and T-50/Pak-Fa IRST creates a radar signature, because AESA radar is X-band. X-band wavelength is 2.5 (one inch) to 4cm. Also, IRST is a round sphere and not a shaped nose (e.g. duck bill shape/continuous curvature or faceted/diamond shape).
Therefore, X-band radar will detect the Su-30/Pak-Fa IRST. Hence, the Su-30/Pak-Fa is not stealthy.
Citation:
HowStuffWorks "How does stealth technology work?"
"
How does stealth technology work?
...
Most conventional aircraft have a rounded shape. This shape makes them aerodynamic, but it also creates a very efficient radar reflector. The round shape means that no matter where the radar signal hits the plane, some of the signal gets reflected back:
..."
Three posts ago, Gambit was arguing the T-50/Pak-Fa IRST probe is like a two-dimensional saw-toothed edge and is therefore stealthy. Do you agree with him? Or does the T-50/Pak-Fa IRST probe look like an excellent round radar reflector to you?
2. Look at the picture above with the rivets. Does it look like a metal-framed canopy to you? Even China's advanced materials science doesn't have the high-strength plastics that you are theorizing. Everyone has to climb the same tech ladder.
The F-22 uses a frameless bubble cockpit canopy. China also developed a frameless bubble cockpit canopy for the J-20. It is highly unlikely that Russia could just leapfrog past the next technological step of a framles bubble cockpit canopy.
3. Look at your picture again (see below). I have drawn the surface area of the fuselage behind the pilot. The T-50/Pak-Fa is much taller and occupies a lot of area. This will strongly reflect radar at many angles.
If you look at other pictures of the F-22 and J-20, you will notice they use continuous curvature to shape the area behind their cockpit canopy. However, when you look at pictures of the T-50/Pak-Fa, you will see two large triangular slabs from the side.
Compare the small surface area behind the F-22 pilot to the large surface area behind the T-50/Pak-Fa pilot.
4. RULE #1 - never look at cartoons in performing an analysis. Let me show you real photographs of the T-50/Pak-Fa. All of them show there is no S-duct on the T-50/Pak-Fa.
From the midpoint of the airduct to the midpoint of the engine, it is a straight line. There is no curved duct. The T-50/Pak-Fa engine layout is identical to the Su-30.
From a lateral view, we will once again draw a line from the midpoint of the airduct to the midpoint of the engine, it is clearly a straight line. There is no curved duct.
5. It has been two years and Sukhoi's T-50/Pak-Fa third prototype looks exactly like the first prototype externally. Unless Sukhoi performs a radical redesign (which increasingly appears unlikely), a straight airduct will mean the T-50/Pak-Fa will be almost as non-stealthy as a Su-30.
When the enemy radar waves bounce off the single-crystal metallic engine fan blades on the T-50/Pak-Fa, the F-22 or J-20 radar screen will light up like a Christmas tree.
6. It has been two years and Sukhoi hasn't been able to wrap the T-50/Pak-Fa engines in RAM cladding. As more years pass, it becomes increasingly unlikely that Sukhoi can fix this problem. I believe it is a cooling issue.
If we keep seeing this exposed metal-engine problem on the next few prototypes then it means Sukhoi can't change the design due to a likely cooling need for the engines.
7. When the T-50/Pak-Fa or Su-30 bay doors are closed during flight, they lie flush against the fuselage. However, due to the non-saw-toothed edges, enemy radar will reflect off the large discontinuities. The F-22, F-35, and J-20 all have saw-toothed bay doors to minimize this RCS problem.
8. Vents are not stealthy, because of radar scattering from edge diffraction.
9. An uneven underside is not stealthy. It creates many new angles for a radar reflection. Australia Air Power wrote a detailed report and criticized the modified F-35 for the "lumps and bumps" along its underside. The original F-35 prototype had a clean and flat underside like the F-22 and J-20.
Due to the need for air-to-air missiles with the development of the J-20, the F-35 underside is a mess and it is less stealthy.
Reference:
http://www.ausairpower.net/APA-2009-01.html
10. When an enemy radar hits the "back wall" (or intersection between fuselage and airduct), it will produce a nice radar return. This is poor stealth design. This problem exists on both the Su-30 and T-50/Pak-Fa.
