Amiga500The author(s) of that patent are OKB Sukhoi employees and are specifically assigned to the development of the T-50’s avionics. That patent is the second (of three) incarnations. The third (most recent) differs only in minor updates.
I’ve lodged patent applications on behalf of OEMs before and they are about as near to going on airframes as warp drives!
Patent =/= On aircraft.
Amiga500Easy jet? A319/A320 only I think.
edit1: Ahh, Jet2 in the article.
edit2: Storm in a tea-cup. Unburnt fuel from the combustor* igniting in the the nozzle duct probably – and not on the airframe.
*which was probably damaged due to a foreign object… e.g. daffy duck.
Amiga500well AGM-86 was designed with reduced RCS in mind , it’s size is much smaller thus make it much easier for resonance and creeping wave to work , but it’s RCS still increased b only 10 dBsm frontal
Which is why I need to read the book to see what they’ve done, why and how.
Amiga500far enough but according to that then F-16 RCS is around 99% the same between 1 Ghz and 10 Ghz
the cruise missiles’s average RCS increase alot but it’s frontal RCS still only increase by 10 dBsm when frequency moved from 10 Ghz down to 1 Ghz
Indeed, but the F-16 has not been designed to remove the effect of the small features on RCS… hence increasing frequency doesn’t result in a change in RCS.
Amiga500Still haven’t had (and won’t find for some time)… erm… time to investigate OhhShiny’s links.
——————-
One thing reads weird though (MIG post #305):
“The SBR method is valid when the largest object dimension is at least 100 wavelengths long”
Valid when the largest dimension is at least…?
I smell a f__kup… somewhere*. If its a model that is supposed to analyse the detail of a shape, then only being effective when the largest dimension reaches a certain point is nonsensical.
*A typo in writing this, a mis-read in CST2012, a typo in writing CST2012 or a misunderstanding along the way.
BTW: The B2 is not a good basis for comparison here, its too large c.f. F-35 and has no “vertical” tail.
These are a bit more relevant:
F-16
[ATTACH=CONFIG]240297[/ATTACH]
Cruise missile
[ATTACH=CONFIG]240295[/ATTACH]
Amiga500Its hard to take a story from faux news seriously… particularly when they say things like:
days after a secret Moscow meeting in late July between Iran’s Quds Force commander — their chief exporter of terror
Does the re|ard who wrote the article not realise that the “main exporter of terror” is actually good ol Saudi Arabia and Sunni Islam? [Same Sunni Islam as ISIS?]
Meanwhile, Iran are 90-95% Shi’a, and are seen as half-way to unbelievers by extremist Sunnis?
Once again, strike up another bull€hit story to Faux.
Amiga500From Electromagnetic Wave Scattering by Aerial and Ground Radar Objects
Professor Oleg I. Sukharevsky. 2015.
https://www.crcpress.com/Electromagnetic-Wave-Scattering-by-Aerial-and-Ground-Radar-Objects/Sukharevsky/9781466576780From Computer Simulation of Aerial Target Radar Scattering, Recognition, Detection, and Tracking
Professor Yakov D. Shirman. 2001.
http://www.amazon.com/Computer-Simulation-Scattering-Recognition-Detection/dp/1580531725
Good sources.
Certainly food for thought for me.
I’ll get back to you on these; I’ll need to read them and my Russian ain’t up to scratch for the first one!
Since posting this, at what point did you realize that you got your fundamental maths entirely back to front for the second link. The equations on P 133 actually show that RCS decreases as wavelength gets larger for those shapes.
Indeed, detail features will always become more pronounced at higher freq; hence shaping for X-band etc. So, conventional fighters without thought to radar shaping have astronomically high RCS at higher bands.
But, it is also why, as wavelength increases, shaping becomes irrelevant, it is the existence of the body rather than the shape of the body which counts.
So, for VLO aircraft that direct the radar waves away from the emitter, that technique becomes less effective as wavelength increases.
As the details disappear, what are you left with:
Wings, control surfaces and fuselage:
Wings being approximated by:
[ATTACH=CONFIG]240344[/ATTACH]
Fuselage being approximated by:
[ATTACH=CONFIG]240345[/ATTACH]
As you’ll no doubt point out, neither of the above are ∝ lambda^2, but I’m not sure if the equations in the 2nd reference include resonant effects or not.
Amiga500iam not talking about the red point-line Armiga, iam talking about their computed blue line
I didn’t write it, I’ve no idea what assumptions and maths they used. I’ve not been using that graph as a basis for my statement.
hence i said the conclusion that target RCS will always proportional to wavelength is wrong
I am quoting a rule of thumb MiG – nothing more.
Amiga500Most RAM absorbing less than 28 dBsm at 10 Ghz while still absorbing around 10-15 dBsm at 8 Ghz, so overall F-22 still have lower RCS at 8 Ghz than 10 Ghz
That graph has 2 data points for F-22 at 8 and 10 GHz at exactly the same dB.
What the the person that made it has, is probably a single RCS number for I-band.
I-band being from 8-10 GHz.
They then conclude that having equal RCS points at both 8 and 10 GHz is an accurate way to represent this [its not].
Which leads to people drawing the wrong conclusions [which is frustrating to try and explain*].
*Not blaming you, the reader cannot always be expected to have the knowledge and experience to interpret what has been done if its a haphazard representation of fact, its the Author’s fault.
Amiga500Anyway, wouldn’t that conclusion strongly contradicting with the graphics simulation that Jo Sakura posted ?
No, because Jo’s graph is doesn’t include RAM.
RAM is extremely effective in X-band, thus being a very good reason for the differential in X-band numbers.
Move away from X-band, and not only does shaping become less effective, but so does RAM. [There are materials which can act over a decent range of wavelengths, but effectivity is reduced.]
Amiga500While i agree that lower frequency reduce stealth aircraft effectiveness, i have to disagree with your assumption that at 1-2 Ghz, stealth aircraft won’t reduce enemy’s radar range significantly
Look – an aircraft cannot always fly straight and level toward a radar. When it starts to present any kind of side aspect, RCS due to angle shoots up and couple that to RCS due to wavelength and low freq. detection range is hundreds of km for a useful search radar.
From what we know F-22 was able to hide from E-2/E-3 radar in exercise, we also know that BAE promote a way to neutralise F-35’s stealth by positioning AWACS out side of it’s 50-60 degree frontal arcs. If stealth no longer work in low frequency how did f-22 hide from AWACS ?, why in their simulation BAE have to station their AWACS in some exact location to intercept f-35?
Singulars are not IADS. Again, you cannot fly straight and level all the time toward a radar – and you definitely cannot fly straight and level toward a series of interlocking radar.
i looked at the page you say but still cant find the part where they state ” target RCS is proportional to observe wavelength” can you screen shot that part and upload here?
“Vehicles with low RCS values will generally show an RCS response proportional to the radar wavelength squared.”
Sentence starts 3 lines from top of page 19A-5.
Amiga500So based on your rule of thumb which is exclusively dependant on frequency, the rcs of a stealth aircraft at 1ghz is still going to be thousands of times smaller than that of a legacy airframe, and subsequently will still have the same impact on detection range against low band radar as it does at xband.
Yes, the detection range for a VLO will be reduced c.f. conventional airframe, but it won’t be to ranges that are significant. The horizon will be of more relevance.
Perhaps you could cite some sources to validate your “rule of thumb” and show rcs results for VLO airframes at different wavelengths as others have produced.
Sure, here’s a couple. First one is generalised comment, 3rd line in page 19A-5, the second link gives a table of geometric features and sensitivity to frequency/wavelength on page 133/134.
http://ftp.rta.nato.int/public//PubFullText/AGARD/AG/AGARD-AG-300-14///21cha19a.pdf
http://legacy.sname.org/sections/chesapeake/events/2005-05.pdf
Amiga500that rule is wrong though , look at the example of flat plate RCS at 10 Ghz and 1 Ghz ( both big and small flat plate have lower RCS at 1 Ghz than at 10 Ghz)
A flat plate is not an aircraft.
Please stop comparing apples to oranges.
Amiga500As I said earlier in the thread, a good rule of thumb is the change in RCS is proportional to the wavelength^2.
[Which was completely and utterly mis-understood by MiG-31. Numbers below.]
Wavelength = c/frequency
So, if RCS = 1 m2 at 10GHz (wavelength = 0.03 m)
then at 8GHz (wavelength = 0.0375 m), RCS ~ 1.6 m2
At 1 GHz (wavelength = 0.3 m), RCS ~ 100 m2
The rule of thumb is applicable to LO aircraft. But obviously, its a rule of thumb, hence approximate and not to be considered exact. But its enough to show the undergraduate report as a load of utter balls.
Amiga500Your point was the modelling is too simplistic? Seems BAE disagreed when they bought into the sim.
Yes, and of course BAe haven’t completely re-written the back end and retained the GUI and maybe pilot actions. :rolleyes:
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