F-35 vs Su-30/35

The F-35 compared with other modern jets.
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sferrin

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Unread post10 Apr 2015, 23:53

eloise wrote:the F-135 engine will only be visible if you managed to get directly behind the F-35 ( that is not very possible )


Actually, the F135 in the F-35 has a radar blocker in the exhaust like the F-22 does in it's F119s.

From the Ares blog 3/17/11:

"Pratt says screech is a phenomenon caused by pressure pulsations in the afterburner at low altitude and high speed. The problem was discovered during development testing around March 2009, having previously been encountered - and solved - in the F-22's F119 engine, from which the F135 is derived. 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."
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Unread post11 Apr 2015, 00:01

Thanks 'sferrin' - had forgotten that bit - go here for more SCREECH! : viewtopic.php?t=15287 (the ARES blogpost URL does not work now - I'll go look)
A4G Skyhawk: www.faaaa.asn.au/spazsinbad-a4g/ & www.youtube.com/channel/UCwqC_s6gcCVvG7NOge3qfAQ/videos?view_as=subscriber
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charlielima223

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Unread post11 Apr 2015, 02:26

ata wrote:
For example F-35 has no protection or any shielding of it's engine, so from the back at least engine must be absolutely visible. I've seen here the picture where even F-22 with shielded engines has 20dB (!!!) higher RCS than in front direction. Only turbine blades should give us about 1 sq.m. It's absolutely clear that from the top or from the bottom it's RCS must be much higher than from the front direction. I've heard here about 0.001 sq.m. value. Ok, but what were the conditions of measurements? I've seen many graphs, is it modelling? If not, if those graphs based on measurements, then what is standard .


conventional jet engine exhaust nozzle...
Image

Someone here mentioned the F-16 LOAN (low observable asymmetric nozzle) that was used as a technology test and evaluation for (then) JSF a ways back
Image
Image

.... i might be misunderstanding the content if so I am sorry :?
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munny

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Unread post11 Apr 2015, 03:03

ata wrote:Moreover munny if you already know what equation is, you probably can see that gain is squared, while for power there is a linear function. So having 3dB less gain you need 4 times more power to compensate it. It's math basics, you probably need to go back to the school or finish the school first.


My old man always told me to make sure I have my argument straight before I bother to insult someone's competence. For example, before suggesting I go back to school, did you bother to check that I had indeed factored in Gain squared in my simplified calculation? :oops:

Basically the forth root of 7 times the power * 7 times the gain squared, or basically single beam range = 80nm * 7^3^.25


I guess no amount of fancy book learnin' can make up for poor attention to detail and inability to comprehend?

My statement was that in the test video shown, precisely at 1.1-1.2 seconds into the test, the APG-81 detected a target beyond 80nm while emitting 7 separate beams simultaneously. (anecdotally, the rear aspect is one of the lowest RCS angles for most civilian aircraft such as airliners if that is what the radar is detecting in the test).

80nm.jpg


https://www.youtube.com/watch?v=CRkpFsXz9yk

Obvious, previously stated Assumption 1 - was that all 7 beams transmitted equal power - probably incorrect as hornetfinn mentioned, as the radar will use a minimal number of modules to track closer/larger targets. Without knowing the specifics on the distribution, 1/7th power (1/7th TRM count running at APO) was used for simplicity. One should note that in the video, at the moment it detected the target at 80nm, at least 3 beams were in search mode (2 had no targets within the beams, 1 had a target within the beam, but was also the one that detected the 80nm target so must have been searching).

search beams.png


Obvious, implied Assumption 2a was that Gt = Gr so G^2 was used. Assuming equal transmit and receive gain based on the relationship to surface area alone for the APG-81 is also probably incorrect due to differences in receive and transmit efficiency for the TRMs.

Obvious, implied Assumption 2b was that 1/7th of total antenna area was used for each beam for simplification. This is also not fully accurate due to the way array thinning is actually performed. Rather than splitting the array into sections of contiguous emitters like so.....

contiguous.jpg


...phased array thinning works by spacing out active emitters for each beam, but not so much as to cause grating waves (ie. it would aim to keep active emitters within half wavelength separation for each beam).

thinned.jpg


Assumption 3 was that the beams shown in the video directly represent dwell times, but there's the possibility that there may actually be fewer beams rapidly switching back and forth between locations but 7 directions are being scanned in that 10th of a second. Operating this way would lead to lower overall dwell times which impacts detection range anyway.

I'm surprised I had to spell all this out for you with you being so smart and educated and all :mrgreen:
Last edited by munny on 11 Apr 2015, 06:50, edited 9 times in total.
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Unread post11 Apr 2015, 03:41

ata wrote:Moreover, PESA in general is able to create more powerful beam in single point


Please describe, in credible detail, by what mechanism a PESA array can generate a more powerful, directional beam than an AESA array considering equal, average power output?

Please compare appropriate operating modes.
Please don't forget to provide sources for your assertions on AESA limitations.
Please do not just post some obscure link with no supporting text demonstrating insight.
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Unread post11 Apr 2015, 06:03

charlielima223 wrote:.... i might be misunderstanding the content if so I am sorry :?


Think they are talking about what's INSIDE the nozzle. Eg, F-22 vs F-15 below....

nozzle.png


The picture's not very hi-res, but it looks like there's two stages of "spray bars or flame holders" present in the F-22 nozzle if I'm looking at the right thing.

Willing to bet that the two stages are spaced at a certain distance apart (eg a multiple of 30mm, add 15mm) to cause destructive interference at 10GHz. There's a TV documentary on the F-35 on youtube somewhere where the person escorting the camera crew told them to stay away from pointing the camera at the "Device" inside the nozzle, so there's certainly something signature related and classified in there.

The outer nozzles close quite a bit on both aircraft though, which would improve rear sector RCS as well as frontal Infrared signature significantly.

f35 noz.jpg


I wonder what speed the F-35 can do at that nozzle setting. The "holy sh*t I need to GTFO of here!" setting is quite open...

open.png
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Unread post11 Apr 2015, 10:04

munny wrote:
charlielima223 wrote:.... i might be misunderstanding the content if so I am sorry :?


Think they are talking about what's INSIDE the nozzle. Eg, F-22 vs F-15 below....

nozzle.png


The picture's not very hi-res, but it looks like there's two stages of "spray bars or flame holders" present in the F-22 nozzle if I'm looking at the right thing.

Willing to bet that the two stages are spaced at a certain distance apart (eg a multiple of 30mm, add 15mm) to cause destructive interference at 10GHz. There's a TV documentary on the F-35 on youtube somewhere where the person escorting the camera crew told them to stay away from pointing the camera at the "Device" inside the nozzle, so there's certainly something signature related and classified in there.

The outer nozzles close quite a bit on both aircraft though, which would improve rear sector RCS as well as frontal Infrared signature significantly.

f35 noz.jpg


I wonder what speed the F-35 can do at that nozzle setting. The "holy sh*t I need to GTFO of here!" setting is quite open...

open.png


It was either a Canadian or Australian documentary (I am pretty sure its Australian). Unfortunately it had two PoS individuals interviewed who like throw around their ignorance like monkeys fling poo. During a walk around when the film crew was getting real close to the back end of the aircraft the military liaison was quick to stop them. Also now that you mention it, when I was at the Nellis AFB open house last year when they had the static F-35 on the ground... the engine exhaust opening was covered.
if you want to watch the video for SnGs... please request to post because I wouldn't know where to put it.
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Unread post11 Apr 2015, 10:42

munny wrote:
ata wrote:Moreover, PESA in general is able to create more powerful beam in single point


Please describe, in credible detail, by what mechanism a PESA array can generate a more powerful, directional beam than an AESA array considering equal, average power output?

Please compare appropriate operating modes.
Please don't forget to provide sources for your assertions on AESA limitations.
Please do not just post some obscure link with no supporting text demonstrating insight.

PESA having the same power as the AESA will be much older and belong to the previous generation.
If you take PESA and AESA radars around of equal area and time ,PESA will have more power.
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Unread post11 Apr 2015, 10:51

the F-135 engine will only be visible if you managed to get directly behind the F-35 ( that is not very possible )
RCS from the top or bottom of F-35 will obviously higher than from front , however it not relevant because the only time you see F-35 directly from the top or bottom is in close range dogfight,
most other time your radar will look at F-35 frontal angle
about the pictures i posted, these are graph of F-22, YF-23 RCS scattering simulation if they was made purely from metal ( based on 3D model of the aircraft )


sorry, I didn't notice it's simulation for metal shape. Anyway, Do you remember what I've started from here? I said, let's talk about real life. In real life it's not necessary to talk about 10 sq. m. objects. If in some directions any of them F-22 of F-35 will have RCS more than 0.01 sq. m. that means they're visible. Even if they have that relatively low RCS at front direction it's quite a strange to make your life deal on something which must be always turned in only one direction to your enemy. Now the question is only "if F-35 reaches 0.01 sq. m. or more in some directions". My opinion is "yes". Even if it has engine stealth protection it simply can't be very effective. It maybe reduce RCS from 1 sq. m. to 0.1 (which is still better than nothing), but it will not help in real life. And of course it will be visible not only "directly behind the F-35" but from quite a wide angle.

thus i make the conclusion that with shaping + RAM it not very hard to achieved frontal RCS around - 30dBsm to - 40dBsm in X band


Frontal - maybe. Moreover, because I have no evidences against this calculation I will say "yes, ok... in front direction let's declare F-35 is invisible in real life". But I already said about "front invisibility only".

if the simulation are acceptable accurate the value of 0.001 m2 for F-35 is achieved with angle of around 45 degree each side frontal


This is based on F-22 (!) 2D (!) simulation and we have, I believe, very limited understanding of how that simulation had been done. In addition we have statement that F-35's RCS at least 10 times higher than that for F-22. All of that give me an idea, that because it's not very big gap between 0.01 (practically visible) and 0.001 (practically invisible) it can be reached in many directions different from frontal.

btw, most statement in this thread are not from LM


I've seen many of theirs promo videos, and the guys were using almost the same words as I've seen here. Journalists came to LM parties, LM engineers, LM sales, LM articles... It's obvious, because LM is the only source of ANY information about F-35.

i already explained to you that LPI is achieved because enemy's RWR classifying AESA radar signal not as a radar signal but as background clutter ( not necessary because the signal is weak, but because they spread for a wide frequency and and dont have particular pattern)
and as explained before RWR can't generate fire solution again moving air target, thus even if the RWR on Su-35 detect and recognised APG-81, it still wont allow you to attack the F-35


Please, don't EXPLAIN me how radar works. In radio tech there is only meaningful values here are LEVELS. Remember that radar of F-35 has also to detect it's own signal from noise. I've got an idea - LPI radar is able to collect information from long time measurements and this make it able to operate lowest possible power. But to be detectable for it's own radar level of reflected signal must be at least comparable with noise level. In the meantime power of LPI signal received at target side will be THOUSANDS time higher than reflected back to F-35. Again, imagine working radar as a torch in the sky. Or better imagine you come to a dark room with very-very weak lamp, you can only hardly see what is in that room. But for the guy how sits in that room will you be the same "hard to see"?


F-35 have 2 optical sensor :
EOTS for long range = narrow Fov
DAS for short range = 360 degree Fov
F-35 likely use Apg-81 to detect Su-30/35


Using radar to detect Flanker (I've explained me idea about LPI already) would mean F-35 has no even it's stealthy advantage. So, no advantage against Flanker at all.

P/s: you have to stop with you double standards Ata, anything good related to F-35 and you instantly said it just advertising, anything good related to Su-30 and you instantly accepted it as the truth, that isnot a healthy attitude for arguing


The difference between us, is that I'm operating numbers (at least those I can find somewhere) and you operate statements. As I said, ALL the information about F-35 you/me can get only from LM. There is simply no other source. And the problem is that all the numbers LM provide us are about things not related to F-35's tactical advantages. No info about RCS, nothing about DAS sensor. No required info about LPI. All we know is about EOTS and it's Flanker detection range. But EOTS is the same "straw" as all modern fighters have, no advantage.
All those things like "ok, LPI radar will detect you easily and we see-first-kill-first, and we also have mega-superior optical sensors" - it's what I call commercial. No numbers, no even explanation how that will appear in real fight.
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Unread post11 Apr 2015, 11:01

munny wrote:
ata wrote:Moreover, PESA in general is able to create more powerful beam in single point


Please describe, in credible detail, by what mechanism a PESA array can generate a more powerful, directional beam than an AESA array considering equal, average power output?

Please compare appropriate operating modes.
Please don't forget to provide sources for your assertions on AESA limitations.
Please do not just post some obscure link with no supporting text demonstrating insight.


It's very simple. My source is physics, is it credible source for you? Do you want a link to "physics"?
When AESA works at every moment not all the modules are working at highest power. This "power distribution map" moves when radar scans. I actually don't know what the exact phase distribution model guys had chosen, but you know... there is very universal level in radio tech which is always working well :D - 0.7
So, I have no evidence, and you're in your right to say I'm faking you, but I would say in best case, in scan mode APG-81 has about 0.7 of it's max power (calculated by each module power * number of modules).
There is no that problem for PESA. In case of PESA it's like virtual oscillators in the spot transmit more power than guys in AESA, but because there is only one real oscillator, it always works at max power.
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Unread post11 Apr 2015, 11:28

My old man always told me to make sure I have my argument straight before I bother to insult someone's competence. For example, before suggesting I go back to school, did you bother to check that I had indeed factored in Gain squared in my simplified calculation? :oops:


I was not referring to your "simplified calculation" because it's just wrong. I'm not referring to something what is wrong. I was talking about your gain understanding. 7 beams is mostly not a question of power, but question of gain. Even gain of every beam will be much lower, but because gain plays it's game twice at transmitting and receiving step it's squared.

I guess no amount of fancy book learnin' can make up for poor attention to detail and inability to comprehend?

My statement was that in the test video shown, precisely at 1.1-1.2 seconds into the test, the APG-81 detected a target beyond 80nm while emitting 7 separate beams simultaneously. (anecdotally, the rear aspect is one of the lowest RCS angles for most civilian aircraft such as airliners if that is what the radar is detecting in the test).

80nm.jpg


https://www.youtube.com/watch?v=CRkpFsXz9yk


:doh:
What do you see at that video? I mean I've seen it several times. I have no idea what those grey sectors mean. Do yo have? Do you think beams? What makes you think this? Again, I'm absolutely confused of those promos made but LM. Not only this video but many others. No details, no reference, no numbers. Why do you think those objects in the video are Flanker-size? Again, what did you see at that video, exactly?


Obvious, implied Assumption 2a was that Gt = Gr so G^2 was used. Assuming equal transmit and receive gain based on the relationship to surface area alone for the APG-81 is also probably incorrect due to differences in receive and transmit efficiency for the TRMs.

Obvious, implied Assumption 2b was that 1/7th of total antenna area was used for each beam for simplification. This is also not fully accurate due to the way array thinning is actually performed. Rather than splitting the array into sections of contiguous emitters like so.....


Ohhh...
You can play with power/phase distribution as you want. In some cases you'll get better result, in some worse, but it doesn't change the simple fact, that your gain will be ALWAYS lower (much lower) than max possible value. That's it.

So, you're great guy. Let's just forget about your calculation. F-35 has enough advantages even without your radar concept.
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sferrin

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Unread post11 Apr 2015, 15:11

munny wrote:Think they are talking about what's INSIDE the nozzle. Eg, F-22 vs F-15 below....


That's the YF-22. The F-22A's back end is very different.
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Unread post11 Apr 2015, 21:55

ata wrote:sorry, I didn't notice it's simulation for metal shape. Anyway, Do you remember what I've started from here? I said, let's talk about real life. In real life it's not necessary to talk about 10 sq. m. objects. If in some directions any of them F-22 of F-35 will have RCS more than 0.01 sq. m. that means they're visible. Even if they have that relatively low RCS at front direction it's quite a strange to make your life deal on something which must be always turned in only one direction to your enemy. Now the question is only "if F-35 reaches 0.01 sq. m. or more in some directions". My opinion is "yes". Even if it has engine stealth protection it simply can't be very effective. It maybe reduce RCS from 1 sq. m. to 0.1 (which is still better than nothing), but it will not help in real life. And of course it will be visible not only "directly behind the F-35" but from quite a wide angle.
Frontal - maybe. Moreover, because I have no evidences against this calculation I will say "yes, ok... in front direction let's declare F-35 is invisible in real life". But I already said about "front invisibility only".
This is based on F-22 (!) 2D (!) simulation and we have, I believe, very limited understanding of how that simulation had been done. In addition we have statement that F-35's RCS at least 10 times higher than that for F-22. All of that give me an idea, that because it's not very big gap between 0.01 (practically visible) and 0.001 (practically invisible) it can be reached in many directions different from frontal.

Firstly, neither F-22 or F-35 are invisible , they just have really low RCS thus enemy cant detect them soon enough, allow them to have first look, first shot, first kill advantage ( just like a submarine)

Secondly, recently according to general Hostage, F-35 is even more stealthy than F-22 ( it likely that at the start they didn't required f-35 to have better LO characteristics than F-22, however it
is said that F-35 excess the LO requirements)

Thirdly, almost most all fighter radar only have FoV of around 60 degree ahead, and in BVR they are likely to go head on to the other



Last, look at the pictures below ( RCS simulation of stealth fighter like F-22, F-23)
Image

without RAM the 90 degree frontal arcs have RCS of around - 20 dBsm with some part reached - 13 dBsm, 2 spike reached - 5 dBsm but the angle is too narrow to have significant impact

without RAM the 90 degree tail arc have RCS fluctuating between -5 dBsm and 0 dBsm , and reached the peak of 10 dBsm if the enemy is directly behind

RCS from the side are very high, however when you fly perpendicular to enemy then doppler effect on reflect signal will be really low thus they are rejected by enemy radar, as a result your fighter become invisible

Now we dont know exactly what kind of RAM and paint that F-22 and F-35 use, they are likely using many different kind of advanced RAM at the same time, so we can only estimated
Image
Image
Image

it can be seen from these graph that using different kind of RAM can reduce RCS by another 18-30 dBsm depending on frequently
( now you can put this and the picture above together to estimated F-22/35 RCS from different angle if they have RAM, may be come up with sth like this, yourself

Image





--------—-------

ata wrote:I've seen many of theirs promo videos, and the guys were using almost the same words as I've seen here. Journalists came to LM parties, LM engineers, LM sales, LM articles... It's obvious, because LM is the only source of ANY information about F-35.

by your way of thinking then any information related to Su-30/35 come from sukhoi as well so what is your point?
btw the theory about how stealth affected jamming and radar range doesn't come from LM, the radar equation doesnt come from LM , the simulation of RCS and RAM that i posted above doesn't come from LM either, even the theory of how LPI doesn't come from LM. they are not even advertising but rather the principles based on physics


ata wrote:Please, don't EXPLAIN me how radar works. In radio tech there is only meaningful values here are LEVELS. Remember that radar of F-35 has also to detect it's own signal from noise. I've got an idea - LPI radar is able to collect information from long time measurements and this make it able to operate lowest possible power. But to be detectable for it's own radar level of reflected signal must be at least comparable with noise level. In the meantime power of LPI signal received at target side will be THOUSANDS time higher than reflected back to F-35. Again, imagine working radar as a torch in the sky. Or better imagine you come to a dark room with very-very weak lamp, you can only hardly see what is in that room. But for the guy how sits in that room will you be the same "hard to see"?

No things are not that simple
again you dont understand how a RWR classified the signal as threat, just because it can detect something doesnt mean it can classified that thing as enemy radar, if RWR instantly classified anything it detect as enemy radar then your screen will be filled with background noise, ground reflection from your own radar, datalink or ECM : ( read the slide below about compression of pulse)
Image




------------------------------------
ata wrote:Using radar to detect Flanker (I've explained me idea about LPI already) would mean F-35 has no even it's stealthy advantage. So, no advantage against Flanker at all.

i have explained this before
Firstly, it very very unlikely that your RWR recognised APG-81 signal as radar signal
Secondly, even if it does, and you managed to track the F-35 by your RWR , you still cant attack it by missiles because you cant use RWR to measure range or speed of a moving air target, the only thing you know is the direction
there are 6 ways a RWR can geolocate a ground radar for an aircraft to attack it
Image
owever none will work again air target using AESA radar
here is why :
1- triangulation method required target to be stationary , and take very long time
2- Azimuth / Elevation method will not work because you dont know enemy fighter altitude ( for a ground target you know the altitude is 0 ) thus cant use the Sine and Cosine function to work out the distance to target
3 - Time different arrival method required at least 3 aircraft stay at significant distance from the other ,but doesnt work again AESA radar due to it very small side lobe , and thin beam

there are some additional methods to determine distance by RWR included :
4- phase rate change : doesnt work again air target because it required target to be stationary to be accurate
5- determine distance by signal strength : required to threat radar characteristic to be known , and still doesnt work because F-35 can reduce radar transmitting power at short range to reduce probably of detection
6- RF doppler processing : doesnt work again air target because both side are moving ,and you dont know the moving speed of enemy
,




-----------------------------
ata wrote:The difference between us, is that I'm operating numbers (at least those I can find somewhere) and you operate statements. As I said, ALL the information about F-35 you/me can get only from LM. There is simply no other source. And the problem is that all the numbers LM provide us are about things not related to F-35's tactical advantages. No info about RCS, nothing about DAS sensor. No required info about LPI. All we know is about EOTS and it's Flanker detection range. But EOTS is the same "straw" as all modern fighters have, no advantage.
All those things like "ok, LPI radar will detect you easily and we see-first-kill-first, and we also have mega-superior optical sensors" - it's what I call commercial. No numbers, no even explanation how that will appear in real fight.

no, i gave you many number, as well as theory on how things work, most of them not even from LM, but you just dont bother to read any of that
for example the RCS have been discussing many time, and you got the info from both USAF, LM, as well as simulation of the third party , but you just really un willing to accept it
Last edited by eloise on 11 Apr 2015, 22:18, edited 2 times in total.
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Unread post11 Apr 2015, 22:15

sferrin wrote:From the Ares blog 3/17/11:

"Pratt says screech is a phenomenon caused by pressure pulsations in the afterburner at low altitude and high speed. The problem was discovered during development testing around March 2009, having previously been encountered - and solved - in the F-22's F119 engine, from which the F135 is derived. 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."

First time i heard of that, thanks
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