F-22 and F-35 RCS revealed by USAF

[delvo]

I've adopted the late, great, Professor J. Rufus Fears' convention of using the Greek phonetic spelling of 'Hybris'.

That's neither Greek nor phonetic. It's a mistaken and misleading Romanization of a word whose original spelling isn't even in this alphabet, and whose pronunciation is not what that spelling looks like to modern English-speakers. Spelled phonetically in the Latin alphabet (ours), it would have a "u", not a "y", because the sound is actually more like in "flu" or "flew", not "fly". Spelled in the Greek alphabet, which the letter "y" was meant to evoke to Latin audiences because their established familiar alphabet had no such letter, the whole word would look different, not just one letter.

The letter "y" was a late addition to the Roman alphabet, based on the Greek letter upsilon, the equivalent of Latin "u". It was entirely redundant to "u", representing exactly the same sound, and had no use in Latin spelling other than in the transliteration of Greek names & terms to make them look more foreign and exotic, like the fake-foreign elements in the modern English name "Häagen-Dazs". Later, when the letter "y" was established as part of the Latin alphabet but its sound-value shifted so it wasn't the same as "u" anymore, any word from earlier times that kept it would get mispronounced (like "hyper/hypo", which were pronounced "huper/hupo" originally, before the pronunciation got influenced by the lingering "y"-spelling), and any whose original pronunciations were preserved needed to use "u" for that phonetic spelling (like "hubris").

Of course, that got further complicated by the modern English habit of pronouncing "u" as "yu" even in words that weren't like that originally, but the fact remains that just replacing "u" with "y" in a word of ancient Greek origin does not make the spelling either Greek or phonetic.

[smsgtmac]

No....Not Even Close.
The ‘flat plate’ equation you present is not relevant to a flat plate tilted at the angle indicated. If you had read the paragraph after that equation in your source, you would have read this:

formula_again.png

Note the highlighted point of interest.

What does it mean? Let me explain.
If we have a laboratory, a set of devices to generate and measure a signal of interest, and we are going to perform some precise measurements, we should at first calibrate our devices. It means the measurement of exactly known pattern.
Let's take a closer look to the formula - biuld a dependency on freq (6-15 GHz) and in wide angle span:

formula_dependence.png

So, indeed, we can calibrate ony in very narrow angle span near normal line.
But stop now!
Why we are talking about calibration at all? Who cares of it?
Does it mean that the formula is wrong or has a limited usage (i.e. rcs of plane undergoes different laws)?
NO.
So what was that? What kind of logical fallacy -
Composition fallacy - http://www.nizkor.org/features/fallacies/composition.html
or Red Herring ? http://www.nizkor.org/features/fallacies/red-herring.html

Go further.

formula_dependence2.png

Your ".1m" edge would have a .1m^2 effective area. Guess what that does to your calculations.

You've posted just a part of paragraph. Please, pay attention to underlined words.
Should I replace S=a*b in formula (5.23) by b*b ? What should I do with lambda squared?
What should I do with sin(x)/x, where x is also dependent on tilted edge "a"?

I'll tell you what it REALLY means:
Independence of frequency, as for sphere, means that we are in this region:

optical.png

For this region RCS is equal to geometric square of object (normal to line of sight)
For shpere it is pi*R^2, and it really frequency-independent.

For tilted plate just its square S=a*b is replaced by S=b*b,
so the result RCS is 0.01 sq.m. - much greater than I calculated.
And with NO placement to (5.23) formula.

I understand that you are trying to fool me (and every forum visitor who read this).
It is just another trap for weak minds.

Curved surfaces require treating specular diffraction of RF energy as a return from striking a "specular point" (Knott et al, P. 549). I have no desire to spend my time explaining what this means, even if we just covered what we could find in the public domain.

I tell you - this is Huygens–Fresnel principle I've mentioned.

At aspect angles greater than ~40 degrees, the relevance of the theory of physical optics “gives way” (Knott et al, P. 232) to edge diffraction

“4?” You cannot treat the RCS of the canopy as an independent RCS number if it is integrated into the overall design such that the canopy is properly ‘blended’ into the rest of the aircraft.
“5?” A good LO aircraft has excellent impedance matching between its constituent components and to the airstream.

Two statements contradicting each other? I dont know how is this logic fallacy (or trap) called, maybe you know better.
Just decide first - Edge diffraction or integration into design with no discontinuities?

1. I calculated RCS without edge diffraction which of cause can be added too.
2. Do you mean this:

discontinuity.png

It's just ridiculous.
It is true for tooth-like edges between parts of airframe, but not for canopy.

Now, go read up on this stuff. I dont know who is troll here.

BTW, if it may help, I am 36, live in Belarus, have a family, 3-room apartment, 2 dogs, and I drive a 17-yo peugeot.

Mityan! You came back!
Yes, I do have a talent for ferreting out logical fallacies (decades of test design experience will do that for you). Your latest reply contains at least five (In order: Red Herring, Non-Sequitur, Non-Sequitur/Burden of Proof, Red Herring via False Dilemma, and a Fallacious Appeal to Ridicule). But as today is our (American) day of Thanksgiving, I am not inclined to spend it ‘Fisking’ your claims.
Instead, for now I refer all to Chapter 5 of Knott etal’s Radar Cross Section, which fortunately is found in its entirety here.

For reference by others, I may later post relevant excerpts, or perhaps just the chapter summary with emphasis added to significant points. The chapter clearly exposes Mityan's contretemps on HF RCS as overly-simplistic, while also supporting my, and several others’ here, observations/points about the same.

Happy Thanksgiving everyone!

[smsgtmac]

I've adopted the late, great, Professor J. Rufus Fears' convention of using the Greek phonetic spelling of 'Hybris'.

That's neither Greek nor phonetic. It's a mistaken and misleading Romanization of a word whose original spelling isn't even in this alphabet, and whose pronunciation is not what that spelling looks like to modern English-speakers. Spelled phonetically in the Latin alphabet (ours), it would have a "u", not a "y", because the sound is actually more like in "flu" or "flew", not "fly". Spelled in the Greek alphabet, which the letter "y" was meant to evoke to Latin audiences because their established familiar alphabet had no such letter, the whole word would look different, not just one letter.

The letter "y" was a late addition to the Roman alphabet, based on the Greek letter upsilon, the equivalent of Latin "u". It was entirely redundant to "u", representing exactly the same sound, and had no use in Latin spelling other than in the transliteration of Greek names & terms to make them look more foreign and exotic, like the fake-foreign elements in the modern English name "Häagen-Dazs". Later, when the letter "y" was established as part of the Latin alphabet but its sound-value shifted so it wasn't the same as "u" anymore, any word from earlier times that kept it would get mispronounced (like "hyper/hypo", which were pronounced "huper/hupo" originally, before the pronunciation got influenced by the lingering "y"-spelling), and any whose original pronunciations were preserved needed to use "u" for that phonetic spelling (like "hubris").

Of course, that got further complicated by the modern English habit of pronouncing "u" as "yu" even in words that weren't like that originally, but the fact remains that just replacing "u" with "y" in a word of ancient Greek origin does not make the spelling either Greek or phonetic.

Delvo
You’re right. I was mis-remembering Fears’ explanation of his use of 'Hybris' as being a linguistic ‘translation’ when he actually identified it as a ‘transliteration’. My bad.

[mityan]

Mityan! You came back!
Yes, I do have a talent for ferreting out logical fallacies (decades of test design experience will do that for you). Your latest reply contains at least five (In order: Red Herring, Non-Sequitur, Non-Sequitur/Burden of Proof, Red Herring via False Dilemma, and a Fallacious Appeal to Ridicule). But as today is our (American) day of Thanksgiving, I am not inclined to spend it ‘Fisking’ your claims.
Instead, for now I refer all to Chapter 5 of Knott etal’s Radar Cross Section, which fortunately is found in its entirety here.

For reference by others, I may later post relevant excerpts, or perhaps just the chapter summary with emphasis added to significant points. The chapter clearly exposes Mityan's contretemps on HF RCS as overly-simplistic, while also supporting my, and several others’ here, observations/points about the same.

Happy Thanksgiving everyone!

Have a nice holidays!

Yeah, it would be much better to emphasis on actual formulas and their physical meaning. Cause they dont subject to logical traps.
Siplistic point of view does not mean that more precise look at the subject will lead to a completely different values (significantly lower in particular).

BTW, google.books has a limit of pages to be viewed.
Here is a russian website where almost the whole RCS book by Knott is available for free download in PDF (e-mail required).
http://www.twirpx.com/file/305691/
(some chapters endings are lost)

[popcorn]

DId Gen. Bogdan just confirm F-35 has superior stealth vs. F-22?



http://www.airforcemag.com/MagazineArch ... roach.aspx

Hostage caused a stir in late spring when, in press interviews, he said the F-35 would be stealthier than the F-22, its larger USAF stablemate. Conventional wisdom had pegged the F-22, with its angled, vectored-thrust engines, as a stealthier machine than the F-35. Hostage also said the F-35 would be unbeatable when employed in numbers, which is why the full buy of aircraft is "so critical."

"I would say that General Hostage … is accurate in his statement about the simple stealthiness of the F-35 [with regard] to other airplanes," Bogdan said in the interview. The statement was accurate for radar cross section, as measured in decibels, and range of detectability, he said, and he scoffed at the notion that anyone can tell how stealthy an aircraft is just by looking at it.

The comment about the effectiveness of F-35s together "has less to do with stealthiness and more to do with overall survivability," he said.

"We are going to ask the F-35 to do things that no other airplane—fourth gen or otherwise—is going to be able to do in the future," he stated. For some of those missions, "it would be much better to do it with more than one F-35."

Besides their stealthiness, the F-35s share information and can perform electronic warfare, electronic attack, and cyber missions.

"When you put two F-35s in the battlespace, … they become even more survivable when they do it together," Bogdan asserted. With two or more, "the sum of the parts is greater than the whole," especially when the aircraft are teaming up "from different parts of the airspace, on the same targets. It becomes quite effective."

[KamenRiderBlade]

DId Gen. Bogdan just confirm F-35 has superior stealth vs. F-22?



http://www.airforcemag.com/MagazineArch ... roach.aspx

Hostage caused a stir in late spring when, in press interviews, he said the F-35 would be stealthier than the F-22, its larger USAF stablemate. Conventional wisdom had pegged the F-22, with its angled, vectored-thrust engines, as a stealthier machine than the F-35. Hostage also said the F-35 would be unbeatable when employed in numbers, which is why the full buy of aircraft is "so critical."

"I would say that General Hostage … is accurate in his statement about the simple stealthiness of the F-35 [with regard] to other airplanes," Bogdan said in the interview. The statement was accurate for radar cross section, as measured in decibels, and range of detectability, he said, and he scoffed at the notion that anyone can tell how stealthy an aircraft is just by looking at it.

The comment about the effectiveness of F-35s together "has less to do with stealthiness and more to do with overall survivability," he said.

"We are going to ask the F-35 to do things that no other airplane—fourth gen or otherwise—is going to be able to do in the future," he stated. For some of those missions, "it would be much better to do it with more than one F-35."

Besides their stealthiness, the F-35s share information and can perform electronic warfare, electronic attack, and cyber missions.

"When you put two F-35s in the battlespace, … they become even more survivable when they do it together," Bogdan asserted. With two or more, "the sum of the parts is greater than the whole," especially when the aircraft are teaming up "from different parts of the airspace, on the same targets. It becomes quite effective."

The man is on top of the inside track and pretty much the head of the program.

If anybody knows the real RCS numbers, it's that man, General Bogdan.

If he says it's lower than the F-22, I can believe his words. The advances in technology between the F-22 and F-35 development on top of knowledge gained from the F-22 would've pushed Stealth technology further ahead. It makes sense that the F-35 would end up being stealthier than the F-22 in the long run given that:

1) F-35 is newer than the F-22, ergo the latest in Stealth / Aerodynamics / Aerospace engineering is put into 1 plane
2) Lockheed Martin learns from any mistakes or weakness in Stealth design of the F-22 and fixes it for the F-35
3) More powerful computers allow better design of Stealth fighters and a better overall aircraft

[mityan]

But what does it mean?
The metal marble is much bigger than it was considered?
Or F-35 has a pin-head RCS?

pin.jpg (7.45 KiB) Viewed 175605 times

[hornetfinn]

There are many sizes of marbles. Maybe F-22 has an RCS of a large marble and F-35 a small marble. Large marbles are larger than golf balls or even tennis balls, so the metal marble reference can mean a lot of things. What's important is that both have very low RCS in any case compared to any previous fighter jet.

[popcorn]

Definitely not beachball-sized though... paging Peter Goon

[mityan]

DId Gen. Bogdan just confirm F-35 has superior stealth vs. F-22?

By the way, it is very interesting, what would Dr. Carlo Kopp say about it.

[taog]

Hey guys, recently I receive some information of JSF program from others. One is a picture comes from LM's paper ("F-35 Program History – From JAST to IOC") which shows that during the development of JSF projram (before SDD phase), there had a requirement for low band RCS reduction. (Highlighted with a red box in the figure )



Also, there was an article published on Aviation Week in 1999/2, "JSF Reflection Is Golf Ball-Sized", which not only stated that the requirement of the RCS spec. for JSF was -30 db but also mentioned that the JSF would have the low-observability ability in VHF band. So it seems like the military, at least, had once considered the VHF RCS reduction for the JSF program (maybe happened at JIRD-1 or -2 or -3 ? Configuration 220-2 was the baseline design when JIRD-1 was released.). Do you guys have any further information about this or whether this low band RCS reduction requirement was retained or dropped after the program entered SDD phase ?




PS. what does "in a 40-deg. vertical fan" mean in the below picture ?

Does there have any report or rumor mentioned the JSF RCS spec. earlier than that article (1999/2) ?

[wrightwing]

Reports from 1999 and earlier, are way out of date. In recent years, it's been revealed that the F-35 has a lower RCS than the F-22. I'd also recommend googling LM"s CNT RAM patents, to get an idea of the frequency range, that it's effective against.

[zero-one]

Reports from 1999 and earlier, are way out of date. In recent years, it's been revealed that the F-35 has a lower RCS than the F-22.

I thought the general consensus was that they are roughly the same. -40 dBm2
While other sources say the F-22 is stealthier from certain angles.

https://www.globalsecurity.org/military ... ft-rcs.htm

From the front, the F/A-22's signature is -40dBm2 (the size of a marble) while the F-35's is -30 dBm2 (the size of a golf ball). The F-35 is said to have a small area of vulnerability from the rear because engineers reduced cost by not designing a radar blocker for the engine exhaust." [Aviation Week & Space Technology; 11/14/2005, page 27]

[taog]

Reports from 1999 and earlier, are way out of date. In recent years, it's been revealed that the F-35 has a lower RCS than the F-22.

I thought the general consensus was that they are roughly the same. -40 dBm2
While other sources say the F-22 is stealthier from certain angles.

https://www.globalsecurity.org/military ... ft-rcs.htm

From the front, the F/A-22's signature is -40dBm2 (the size of a marble) while the F-35's is -30 dBm2 (the size of a golf ball). The F-35 is said to have a small area of vulnerability from the rear because engineers reduced cost by not designing a radar blocker for the engine exhaust." [Aviation Week & Space Technology; 11/14/2005, page 27]

But at final, the F-35 have added the blocker.

In 2001, a report ("Lockheed Martin touts JSF stealth improvement", Aviation Week) said that the F-35 for cost saving, didn't use the blocker. (Also, it mentioned in 2001, LM announced the F-35's RCS already superior to the -30 db. )



But in 2010, there was a news:
"Pratt points out that the F119 and F135 are the only production engines with stealthy augmentors. Their design eliminates conventional spray bars and flame holders and integrates multi-zone reheat fuel injection into curved vanes that block the line-of-sight to the turbine. "

Also, in the recent PDF, F135 truly have the blocker.

[wrightwing]

Reports from 1999 and earlier, are way out of date. In recent years, it's been revealed that the F-35 has a lower RCS than the F-22.

I thought the general consensus was that they are roughly the same. -40 dBm2
While other sources say the F-22 is stealthier from certain angles.

https://www.globalsecurity.org/military ... ft-rcs.htm

From the front, the F/A-22's signature is -40dBm2 (the size of a marble) while the F-35's is -30 dBm2 (the size of a golf ball). The F-35 is said to have a small area of vulnerability from the rear because engineers reduced cost by not designing a radar blocker for the engine exhaust." [Aviation Week & Space Technology; 11/14/2005, page 27]

Depending on the source, they may be better than -40dBm2. The golfball/marble analogy is out of date, too.