@Martin2 By Chinese Logic Only Saw-Toothed Edges Are Stealthy ?
I am surprised that you and Firemaster are unaware of the stealthiness of saw-toothed edges.
Both of you frequent the J-20 thread and you must have read my previous explanations. However, I will provide the citation here in this thread for the first time on saw-toothed edges. Hopefully, you won't demonstrate your ignorance again regarding the stealth design feature of saw-toothed edges.
I am very disappointed in many of you. You have been discussing stealth design for two years now and many of you don't seem to have the faintest understanding of the basics of stealth design for a fighter aircraft. If you are ignorant, why do you keep challenging my list of 17 features for stealth fighter design?
Moving along, you are referring to item #9 on my list (see below). I am providing a citation to buttress item #9.
Reference:
Aerospaceweb.org | Ask Us - Stealth Technology
Saw-tooths are a basic element of stealth design on the B-2, F-22, and J-20. However, unlike the American and Chinese stealth aircraft, many bay doors on the Russian T-50/Pak-Fa have no saw-tooths (see picture below).
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Why hasn't Russia fixed the T-50's problems in the last two years?
Sukhoi hasn't fixed a single stealth design problem in two years.
The list of T-50/Pak-Fa design problems is well known. The more interesting question is why hasn't Sukhoi fixed a single problem in two years. I believe Russia has reached its technological limits.
1.
Protruding IRST - To recess the IRST, it would displace space in the nose section of the plane. This would affect the size of the radar that can be installed. Apparently, there isn't enough space for both a recessed IRST and the planned radar.
2.
Metal-framed canopy - Only two countries, the United States and China, have built a frameless bubble canopy. This is a high-tech item that must withstand sustained supersonic speeds or a bird strike. Russia apparently lacks the technology to build a frameless bubble canopy.
In addition to stealth, a frameless bubble canopy provides an unobstructed view of the airspace.
3.
Tall fuselage behind pilot - If you make a detailed comparison between the T-50 and the Su-30, you will find many similarities. The T-50 appears to be an evolutionary design of the Su-30 and not a completely new design.
The tall fuselage area behind the pilot appears to house satellite communication equipment and cannot be reduced readily.
4.
Engine fan blades in straight airduct - To build a stealthy S-duct, the T-50 would have to be completely redesigned. Sukhoi chose the practical option of installing a linear engine pod, because a S-duct would crimp the payload area.
Also, it is very difficult for maintenance to access a S-duct integrated into the fusleage of the fighter. To design a F-22 or J-20, it would require countless hours of CAD design to ensure that every part was accessible to maintenance personnel.
Sukhoi was willing to sacrifice stealth for ease of maintenance.
5.
Vents reflect radar - In the design of the T-50 and Su-30, the vents are important to shape the airflow and probably to achieve the proper pressure in the engines. Sukhoi cannot simply remove the vents to improve the stealthiness of the T-50.
6.
Metal engine pods reflect radar - Engines are hot and they need to be properly cooled. Sukhoi cannot simply encase the metal engine pods in RAM. Once the engine pods are encased in insulating RAM, Sukhoi must resolve the cooling requirement by building a plumbing network to redistribute the heat.
This would add weight, complexity, and cost to the T-50. Sukhoi may have decided the costs outweighed the benefits of stealth.
The primary purpose of the T-50 is not to win battles against the F-22 or J-20. Russia relies on its thermonuclear arsenal to ensure its safety. In other words, the effectiveness of the T-50 against the F-22 or J-20 is not an issue for Russia.
For foreign purchasers of the T-50, the exposed metal engine pods are a death knell for their airforce. The RCS for exposed metal engine pods is huge. The T-50's exposed metal engine pods are no different from a fourth-generation non-stealthy Su-30 and they can be detected at tremendous distances.
7.
Gaps between airducts and fuselage - The gaps between the airducts and fuselage cannot be eliminated, because there are vents along the side of the airducts that provide a vital aerodynamic function.
Also, you can't just move the airducts and engine pods against the fuselage. There are aerodynamic airflow considerations, heat issue, and maintenance access problems. The airducts and engine pods on both the Su-30 and T-50 were intentionally placed at their exact locations.
If you move the airduct and engine pod, the center of mass of the wing changes and it affects the stability of the plane.
8.
Uneven heights of underside - To achieve a smoother and stealthier underside, there are only two choices. Either reduce the size of the airducts and engine pods or expand the fuselage and extend it downwards.
The airduct size can't be changed, because the engines require a flow of a minimum cubic feet of air per second. The engine pods can't be reduced, because the combustion chamber needs a minimum size to achieve a desired thrust.
The other choice is to extend the fuselage downwards. This is not a simple proposition. This affects the rigidity of the entire fuselage. The fuselage ribs will be much larger (i.e. heavier) and it may compromise airworthiness. Preserving the same width, longer fuselage ribs are weaker and cracks may develop earlier.
Also, an extended fuselage will block the internal side vents. This is a constant theme. If Sukhoi tries to improve the stealth characteristic of the current T-50, it tends to conflict with an existing aerodynamic need.
9.
Lack of stealthy saw-toothed edges on bay doors - If you look closely at pictures of a J-20 with its saw-toothed bay doors closed, it is impossible to see the outline of the saw-toothed edges. This is a credit to China's machine tool industry. The precision of the machining can achieve very fine tolerances.
On the other hand, pictures of the closed straight-edged bay doors on the T-50 show the clear outlines of the doors. Without machining to fine tolerances, Sukhoi has probably concluded the closed bay doors aren't stealthy anyway. There is no point in introducing non-stealthy saw-toothed bay doors.
Russia lacks an advanced machine tool industry and stealthy saw-toothed doors are beyond her current technological capability.
10.
Round engine-pod shape reflects radar - I've already covered this issue in item #6. Sukhoi cannot just encase the hot engine pods in RAM material.
11.
Lack of gold-colored transparent RAM for cockpit canopy - There are pictures of F-22 and J-20 with gold-colored transparent RAM on their frameless cockpit canopies. To date, I have never seen a T-50 picture with similar transparent RAM.
Russian material science technology appears to have reached its limit. Russia may be capable of manufacturing opaque RAM for the plane in general. However, in two years, Sukhoi has not been able to produce transparent gold-colored RAM.
On the other hand, Sukhoi may have decided gold-colored transparent RAM is pointless. Since the metal-framed cockpit canopy is already reflecting radar, there is no point in applying transparent RAM to the T-50 cockpit canopy.
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In conclusion, Sukhoi hasn't tried to fix all of the well-known problems with the T-50/Pak-Fa because the alteration of part of the plane affects the performance of other parts of the plane. In other words, Sukhoi is trapped.
Sukhoi can't make the T-50/Pak-Fa more stealthy, because the Su-30 airframe was never meant to be used as a stealth platform. To build a F-22 or J-20 class stealth fighter, Sukhoi needs to start with a clean sheet. However, the development of a world-class stealth fighter can take a decade or more.
Russia doesn't have the luxury of starting with a new design and it needs a "stealth" fighter for export now. Hence, the result is a severely-compromised T-50/Pak-Fa.
The T-50 is an evolutionary improvement on the basic Su-30 airframe by having a stealthy shaped nose, internal weapon bays, planform alignment, canted forward airduct, and canted vertical stabilizers.
If you are counting, you will notice the T-50/Pak-Fa lacks 12 stealth design elements (when you include non-serrated round engine nozzles) and only has five stealth design features.
The T-50/Pak-Fa is clearly not competitive with the F-22 or J-20. Sukhoi has a long way to go. It will be interesting to see if Sukhoi is able to improve on the currently deficient third T-50/Pak-Fa prototype.
The youtube video I posted is about YF23. It is assumed that F23 is much better than F22. Come back to India and watch it 
. However, I will provide the citation here in this thread for the first time on saw-toothed edges. Hopefully, you won't demonstrate your ignorance again regarding the stealth design feature of saw-toothed edges.
