gambit
PROFESSIONAL
- Joined
- Apr 28, 2009
- Messages
- 28,569
- Reaction score
- 148
- Country
- Location
I bet you spent a few hrs on the Internet going thru various forums looking for what you want but found none so you just simply made up that answer.Professional Chinese aviation engineers have said those horizontal edges along the nose is used to create vortexes to maximize lift and maneuverability. I will take their words over a fanboy's.
Those ridges are called 'chines'. When I told you 'wrong', it was not because the chines have no influence on aerodynamics. They do. But aerodynamics is not the only factor. You were wrong in relation to radar detection, specifically, a contribution to making the aircraft low radar observable. The most visible example is the SR-71 where the jet's design demands the most 'extreme' of chines possible.
https://en.wikipedia.org/wiki/Chine_(aeronautics)
Wikipedia is too general. Not wrong, just too general. Avoidance of corner reflectors, specifically the 90 deg type, is a must anyway. The F-22, F-35, and J-20 do have corner reflectors.Blending the chines into both the fuselage and the main wing avoids presenting corner reflectors or vertical sides to radars.
But I will give a more specific explanation.
I gave you and your Chinese friends two clues regarding radar signals behavior:
- Ten lambda
- Conic
Clues I know my trainees a long time ago, before the F-35 and J-20, would not need to understand why.
First... clue is the 10 lambda ( λ ) rule: This rule states that the creeping wave behavior WOULD NOT exist if the physical diameter of the circle is 10 TIMES the operating wavelength ( freq ) of the impinging radar signal.
Lambda ( λ ) is the symbol used to represent wavelength or frequency.
Curvature produces surface wave behavior. As the signal travels on the surface, there are minute amount of radiation call 'leaky waves'.
Just in case you think I made this stuff up...
http://www.sciencedirect.com/science/article/pii/0165212595000139
So in designing a low radar observable structure, we DO NOT want the creeping wave behavior. The leaky waves can be minimized, not completely eliminated, with absorbers, so if they are low amplitude enough, they can be lost in background clutter. But the creeping wave behavior must be dealt with and the best way is to enlarge the diameter to ten times the physical wavelength.The coupling coefficient Gl is approximated for the description of the launching and detachment of leaky guided waves on spheres and circular cylinders.
Again...Just in case you think I made this stuff up...
Please note the 'INTRODUCTION' paragraph...
Note the authors' names. They are not Westerners. Finally, the paper's date: 1997.When the geometric dimension is large enough (>10λ), the quantity of creeping wave on the backward direction can be neglected.
Second... clue is the conic or conical shape: The cone is cylindrical but it also has a taper, or a gradual slope towards a smallest point.
In trying to convey the many ideas in radar detection, most visual depictions of the radar signal is an arrow.
But in reality, this is what a radar signal actually looks like...
The radar signal is actually a long cone with many 'petals'. The central structure is called the 'main beam' or 'main lobe', and the many petals are called 'side lobes'. The main lobe is where the bulk of radar detection occurs. The side lobes are weaker in amplitude, more incoherent, and more prone to produce erroneous information, hence, side lobes data are usually discarded.
When we add the two clues together, what else does the chines do besides providing some aerodynamics effects ?
To date, all radomes are roughly conical in shape, which means they have a taper towards a small point, which also means that eventually, the creeping wave behavior will occurs on the radome and the radar signal will return to source direction. For a 'stealth' aircraft, this is undesirable.
But we do not want the radome to be angular as well. A flat surface is an excellent reflecting surface. We want some curvatures. Remember rule 3:
- Control of quantity of radiators
- Control of array of radiators
- Control of modes of radiation
What the chines do is create an edge to break up the creeping wave behavior. The radar signals essentially traverses the curve and finally radiate into space on the other side. The weakest signals that may return to source direction would be at the radome's tip and should be lost in background clutter.
Am I a 'fanboy' ? You bet. I have no problems with the label. I am a fanboy of US airpower in specific, and of the US in general. But none of you PDF Chinese fanboys of the Chinese military can produce a credible technical post like this one or like post 6311.You don't have the laws of physics on your side. Your understanding may be flawed. You are not a professional aviation engineer. You have no working experiences or even superficial knowledges in this field. You don't have extensive measurements and test results to back up and verify your claims. Chinese engineers have vast amount of resources and experiences to minimizes the effect of canard on RCS. This is my point and I stick with it.
Not even you or anyone has claimed that the canard's RCS can not be minimized or reduced drastically. So stop making a fool of your self with your little bit of 'knowledge' or misunderstanding.
I am a USAF veteran on two jets, F-111 ( Cold War ) and F-16 ( Desert Storm ). After the military, I worked as a field engineer for a company that shall remain unnamed in designing open environment radar detection testing for 'unmanned autonomous flight vehicles', aka 'drones'. I changed industry for family related reasons and am currently in semiconductor, specifically in Probe engineering.
When I said I am %99.999 confident that I am correct about the radomes based upon looks alone, that does not mean I am truly correct. It just mean I am that confident of my guess. I can say that I am %100 confident that Marvin the Martian will be the next UN Secretary General and I will be wrong. But regarding the radomes ? I doubt I am wrong as to why they are shaped that way.
Which leads up to the canards. My point is that in the INITIAL assessment specifically to being a low radar observable design, based upon the three rules that I have repeated posted on this forum over the yrs, the canards are immediately suspect. I do have the laws of physics on my side on this. Whether or not they are treated in some ways to minimize their contribution to RCS, we do not know. At best, we can guess with %99.999 confidence that their leading and trailing edges are treated with absorbers to control edge diffraction. We can see this treatment from various photos.
But that does not eliminate all signals that will come off the canards. I do not care how many times you cry 'vast resources' for the Chinese engineers. Nothing is perfect, not even the Chinese, no matter how much you want to believe of yourselves. Some radiated signals will come off the canards and interacts with signals from nearby structures. This is where I said we should be generous and do not make definitive statements in the absence of hard measurement data.
You PDF Chinese do not like it and would make the definitive statement that the canards do not matter. How can you make that statement in the absence of measurement data, the same demand that you made of me ? Faith is what you have. When I said I am %99.999 confidence of my opinion, it came from knowledge, experience, and logical thinking processes. Faith is that tiny %.001. In your case, faith is %100.