estorilm
Topic Author
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PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Tue Jan 03, 2017 3:54 pm

I HATE to do this, but I'm just fuming over these pro-Russian aviation kids on Instagram posting pictures of the T-50, and touting ridiculous misguided assumptions about the incredible superiority of all-things Russian and T-50.

Now granted, I 'm not "stooping to their level" - but most of my arguments were based on prior knowledge of these things, as well as analyst takes. It blows my mind how blind some people can be. Especially when they say something like "well, so what - Russia invented stealth" - uh. Even if that were true, the list of successful operational/retired US stealth aircraft is unrivaled.

In any event..

One specific aspect of the PAK-FA that hits me EVERY time I see an image of it, is its' (apparent) lack of high quality stealth lines at the rear of the aircraft, specifically near / along engine nacelles and obviously the "turkey feathers" which I suppose it needs for 2-axis vectoring, but compared to the design of the F-22, there would appear to be a DRAMATIC RCS difference between the two aircraft, when viewed from below/behind.

It also appears that the lower engine covers are not only round (no bueno for RCS) but some form of unfinished metal, titanium or something? No paint or RAM etc AT ALL?!

It obviously lacks the cockpit glass coatings, and some other stealthy aerodynamic features (from all angles, not just bottom/rear) plus appears to be a (relatively speaking) large aircraft.

With all of this in mind, just how much worse do you think the RCS of the PAK-FA is from a given angle?

Also, regarding radar and sensor capabilities the propaganda kids keep talking about - I must keep reminding them that the wing-mounted sensors (even if capable of detecting a stealth aircraft) are incapable of passing along targeting information to the weapons. If they're just for SA - does that mean a PAK-FA pilot would simple disengage in a long-range BVR engagement with a known hostile, hypothetically something like an F-22?

So I'm also curious what you think hypothetical tactics would be, given the incredibly high odds of a BVR-type scenario that many think the planes would find themselves in almost exclusively.

PS: I realize that the last statement implies a lack of importance to the aft and belly RCS, which is obvious, but again I'm just thinking hypothetical RCS from a given angle, out of curiosity.

Without knowing the performance of the RAM both countries are employing, I suppose this is all highly pointless (though given prior experience, I'd expect exceptional performance on the F-22) - but for argument sake, let's go for it. :)
 
WIederling
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Tue Jan 03, 2017 5:39 pm

A question of dogma.
Your basic argument is "we have $something and think that $feature is the best ever"
followed by "$other does not have this and is thus inferior."

There are different ways to make an omelet.

IMU stealth shows its best advantage for an aggressor in a surprise attack.
That is the US domain but not the MoO of other countries.
Murphy is an optimist
 
LightningZ71
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Tue Jan 03, 2017 6:22 pm

As the previous poster pointed out, it's all about tactical docterine and industry capability. The F-22 was designed as an all aspect air superiority fighter. It was to operate in an environment where it was vastly outnumbered and had to survive many missions. For this reason, a primary design factor was maximum survivability both at bvr and after the WVR merge as well as being able to rtb safely.

The F-35 is a strike fighter designed for first day penetration operations in a high A2AD environment. It has a secondary role for BVR combat, recon, and battlespace management. It needs to get in unseen, destroy the high value target, and leave while in a high threat area.

So far, Russian and Chinese stealth designs have largely focused on countering US strengthen by exploiting it's knock on weaknesses. For this, they developed aircraft that have good frontal RCS reduction, at the expense of other aspect detectability. This isn't to say that they are bad. They are still low detectability designs from all aspects, they just make different trade offs. The US weakness they want to exploit is the US reliance on tankers and AWACS aircraft. Most US fighters are rather short legged, by design, trading fuel fraction for equipment and performance. If an adversary can get within firing range of those large, vulnerable assets, they can either chase them off, resulting in mission kills for US forces, or destroy them, preventing the US from operating from its comfort zone.

Of note, in addition to the low RCS fighters, Russia and China have been both hard at work on very long range A2A missiles. Missiles with projected ranges of greater than 125-150nm and fully autonomous mid course guidance and terminal homing.
 
VSMUT
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Tue Jan 03, 2017 8:14 pm

Apart from what is noted by the previous posters:

1. The PAK-FA isn't complete yet, so we don't know what improvements might find their way onto production variants. Even when it enters service, experience shows that the Russians tend to keep developing and refining the basic design and fielding new and improved variants.

2. It is still a significant improvement over existing types in the Russian arsenal.

3. Russia operates with a total defence budget that is miniscule in comparison with the F-35 program alone (and smaller than the F-22s total cost). With that small budget they have to develop and field new tanks, ships, submarines, cargo planes, bombers and upgrades to all existing equipment and infrastructure. Expecting Russia to come up with a gold-plated F-22 style solution on such a small budget is probably a bit optimistic.

estorilm wrote:
I HATE to do this, but I'm just fuming over these pro-Russian aviation kids on Instagram posting pictures of the T-50, and touting ridiculous misguided assumptions about the incredible superiority of all-things Russian and T-50.


Learn to ignore them. The internet is full of those types. Go back just a few years and a lot of websites were full of these pro-American aviation kids doing the exact same. In the next ten it might be the Chinese or Indians or whatever. Best to just avoid them like the internet trolls they are.
 
ThePointblank
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Wed Jan 04, 2017 3:26 am

I would be more concerned about the quality control on the PAK-FA than anything else. From the pictures of some of the prototypes and aircraft that were in production, the panels don't appear to line up perfectly; this is very critical for aircraft that are supposed to be stealthy. Any sort of crease or visible seam is greatly magnified on radar. That's why you hear of aircraft like the F-22 and F-35 being assembled used laser alignment and differential GPS type system for assembly; getting the alignment and tolerances just right so all of the seams are perfect requires a lot of advanced technologies and attention to quality control, something the Russians haven't demonstrated.
 
estorilm
Topic Author
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 05, 2017 1:58 pm

Thanks for the replies everyone - and I hope my post wasn't taken the wrong way, it was never meant to tout sort of overwhelming superiority over the aircraft - that's a different subject all together. My "interactions" elsewhere had me curious about certain elements, from a technical and design point of view.

Essentially I was mostly curious to what degree people thought certain shortcuts and compromises were made to rear/belly RCS, simply based on the photos.

Previous Russian fighters all tend to have long metal aft nacelle covers, but you'd think they'd make some attempt to ditch that at least (as someone mentioned, perhaps in production?) I guess the fact that it shares the engines with the SU-35 might have a lot to do with that, but who knows? They're rumored to have new engines ready for testing this year.

I'm definitely curious about the wing-mounted sensors, I guess the l-band AESA?

Though at the end of the day, it really comes down to the extreme range of the air-to-air missiles deployed.
 
virage
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 05, 2017 4:30 pm

estorilm wrote:
I HATE to do this, but I'm just fuming over these pro-Russian aviation kids on Instagram posting pictures of the T-50, and touting ridiculous misguided assumptions about the incredible superiority of all-things Russian and T-50.


Haven't we had enough Russia-bashing during the Obama/Hillary tenure? Those two harbor an almost pathological hatred for all things Russian. Let's turn the page on that. Hopefully, Trump will act with rationality and civility to return us to the days when US-Russia relationships were friendly and the view of Russia was balanced.
 
iamlucky13
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 06, 2017 5:22 am

Instagram is irrelevant. Even as a secondary source one of the oddest outlets to give credence to I can think of. Even worrying about things said on Twitter is less bizarre.

That said, there are some interesting things about the PAK-FA, and Russia has long proven they are no slouches at aerodynamics nor the kind of advanced metallurgy that is required for high performance engines. Claims about electronic capabilities including information management are a lot more questionable, not as much on the basis of their technical prowess as on how complex this gets and how limited their defense funding is. Their funding limitations are also likely to significantly slow the maturity of the air frame and engines, but those two elements we should almost certainly assume will ultimately be top notch, and likewise should assume that it will at least have a far smaller RCS from most aspects than the Flanker. How close they'll get to the F-22 in terms of stealthiness is a harder question to answer, but compromises they made in the prototypes have been pointed out by quite a few observers, including rear-aspect and low-angle RCS.

I think their wing-embedded radars are one of the interesting aspects, although the pseudo-scientific way the Russian media discusses it makes all their claims seem a lot less credible.

From what I've been able to find once I was able to get past the rubbish about "photonic radars," there's conflicting claims about whether it's a lower frequency L-band radar or an EHF "mm wavelength" radar. Either could potentially mitigate somewhat the stealthiness of opposing aircraft, but do not eliminate it, which Russia obviously also agrees on or else they would not bother with their own stealth program.

MM-wavelengths can obviously be used for missile guidance, as that's what the US Longbow system uses, but range is generally limited due to relatively high atmospheric absorption. I don't know if an L-band seeker head can even fit in a reasonably sized missile, but the system doesn't have to guide missiles to potentially be useful if it can at least provide basic direction and range info on stealthy adversaries at longer ranges than X-band radars can.

I don't see that BVR-only engagements as a reality. Stealth aircraft facing stealth aircraft seems like a recipe for closer range engagements, not longer range. Either way, the Pak-FA has all-moving tail surfaces, thrust vectoring, and leading-edge extensions, all of which mean Russia is making maneuverability a priority that points to an expectation of close-range combat.

What extreme range missiles are you talking about? The AA-12 is a medium-range missile. Did I miss something else in development?

virage wrote:
Haven't we had enough Russia-bashing during the Obama/Hillary tenure? Those two harbor an almost pathological hatred for all things Russian.


Criticizing hyperbole isn't bashing.

And your quip about Obama and Clinton is ironically amusing, since in the US they mainly get criticized for downplaying - for civility's sake let's call it the "complexity" - of US-Russian relations. In the 2012 US presidential election, Obama actually mocked his opponent for exaggerating the potential of a US-Russian conflict.
 
VSMUT
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 06, 2017 9:26 am

iamlucky13 wrote:
What extreme range missiles are you talking about? The AA-12 is a medium-range missile. Did I miss something else in development?


Lots. A whole bunch of R-77 derivatives (under the R-VV program) featuring everything from new seekers to ramjets. There is also the Novator KS-172, which is designed to kill AWACS planes, supposedly at ranges of up to 400+ km. Development has been slow due to economic problems in the early 00s, but they seem to be getting some traction by now.

estorilm wrote:
Previous Russian fighters all tend to have long metal aft nacelle covers, but you'd think they'd make some attempt to ditch that at least (as someone mentioned, perhaps in production?)


The tail stinger? It actually serves a purpose. Some types have the APU mounted back there. Most have a whole bunch of sensors mounted in them, including rear-facing radars. It is also a result of the Sukhoi method of designing aircraft. The PAK-FA and Su-27 families are essentially just flying wings with underslung engines. The canyon between the engines increases lift by quite a bit, and the stinger is part of that.
 
tommy1808
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 06, 2017 12:30 pm

VSMUT wrote:
The tail stinger?


I think he means the bare metal surrounding some of the Afterburner pipe. Just like the F100 Super Sabre used to have...

best regards
Thomas
Wait for Donalds Trump´s new book: "The Art Of The Retreat"
 
Calder
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 06, 2017 1:52 pm

Here's an excellent picture for pointing out the tail stinger.

I know I don't need to point out to you all what part is being referred to.

Image
C. T.
 
VSMUT
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 06, 2017 1:59 pm

tommy1808 wrote:
VSMUT wrote:
The tail stinger?


I think he means the bare metal surrounding some of the Afterburner pipe. Just like the F100 Super Sabre used to have...

best regards
Thomas


It's funny, because the Su-34 doesn't feature it, and I believe the rear airframe of the Su-34 is based on that of the Su-27UB.

But it is probably a combination of weight savings, design and ease of maintenance. It's a flying wing construction, so there is not really any space to fit heat isolation. It might also have something to do with the fact that it is made from some sort of heat resistant alloy that can't really be painted.
 
estorilm
Topic Author
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 06, 2017 3:45 pm

VSMUT wrote:

estorilm wrote:
Previous Russian fighters all tend to have long metal aft nacelle covers, but you'd think they'd make some attempt to ditch that at least (as someone mentioned, perhaps in production?)


The tail stinger? It actually serves a purpose. Some types have the APU mounted back there. Most have a whole bunch of sensors mounted in them, including rear-facing radars. It is also a result of the Sukhoi method of designing aircraft. The PAK-FA and Su-27 families are essentially just flying wings with underslung engines. The canyon between the engines increases lift by quite a bit, and the stinger is part of that.

Nah, the actual engine covers that look to be ~6-10' long (ALL metal) - and I stand corrected, as they're actually on the top AND bottom of the aircraft. I believe the F-15 has something similar; the metal actually covers the lower portion of the engine area AND the void between the engines. This was very typical of 3rd & 4th gen fighters from what I can recall.

The "stinger" definitely jumps out at you when you look at the PAK-FA, but like you said - I realized early on, it's supposedly some location for integrated sensors and rear-threat detection. Definitely ugly though, and -definitely- not very stealthy. Honestly the entire rear of the aircraft just looks like they gave up on stealth. It's not really a bash on the Russians, just an interesting observation as the aircraft was clearly given specific performance targets/goals, and that area wasn't one of them.
 
iamlucky13
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 06, 2017 11:37 pm

estorilm wrote:
Nah, the actual engine covers that look to be ~6-10' long (ALL metal) - and I stand corrected, as they're actually on the top AND bottom of the aircraft. I believe the F-15 has something similar; the metal actually covers the lower portion of the engine area AND the void between the engines. This was very typical of 3rd & 4th gen fighters from what I can recall.

The "stinger" definitely jumps out at you when you look at the PAK-FA, but like you said - I realized early on, it's supposedly some location for integrated sensors and rear-threat detection. Definitely ugly though, and -definitely- not very stealthy. Honestly the entire rear of the aircraft just looks like they gave up on stealth. It's not really a bash on the Russians, just an interesting observation as the aircraft was clearly given specific performance targets/goals, and that area wasn't one of them.


It looks to me like composite over the fan section, and a mix of materials over the hot section:
https://upload.wikimedia.org/wikipedia/ ... tyukov.jpg

It doesn't look like provisions have been made to add additional covers later, but that doesn't mean it can't still be changed, especially once the new engines are integrated. The tail stinger actually looks to have been designed with some deliberate shaping, but it's hard to tell from some angles.

Regardless, there's no sign of shrouding or shaping the nozzles intended as was done on the F-22, and there seems to be less "shadowing" of the nozzles by the tail surfaces, so presumably the rear aspect RCS will be larger than the F-22, and the angle over which the nozzles are visible to radar is probably wider. The F-22 supposedly could have achieved slightly higher thrust and lower weight with round nozzles, so there's an engineering tradeoff for Sukhoi to consider.

I suppose a marketing person would discuss the rear aspect RCS by saying, "The PAK-FA wasn't designed with running away in mind." :box:

VSMUT wrote:
Lots. A whole bunch of R-77 derivatives (under the R-VV program) featuring everything from new seekers to ramjets. There is also the Novator KS-172, which is designed to kill AWACS planes, supposedly at ranges of up to 400+ km. Development has been slow due to economic problems in the early 00s, but they seem to be getting some traction by now.


I wouldn't consider the KS-172 relevant to this discussion since the focus is on fighter vs. fighter encounters. The images that have been shown of that missile indicate high weight and small aero-surfaces, fitting the role of long-range AWACS counter, not a weapon for hitting fighters. Besides, it's too large for internal carriage.

I get the point about extended range derivatives of the AA-12, but in terms of engagements against other 5th generation fighters, I have to go back to the point that the ability to actually detect and guide to terminal-acquisition at long ranges is questionable. For engaging 4th generation fighters, I concede the longer range variants are more relevant.
 
WIederling
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Sat Jan 07, 2017 10:21 am

My guess would be that the gyrations around N'th versus N+-1'th generation is too simple a view.
( Einstein: make the model as simple as possible _but not simpler_ .)
Too much overlap and too much difference design targets.

The US designs most of their stuff for (preemptive, my ass, nothing to preempt in most cases) attack.

Most other countries, the Soviets/Russians up front design for defence and/or standoff.
Murphy is an optimist
 
VSMUT
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Sat Jan 07, 2017 10:52 am

iamlucky13 wrote:
I get the point about extended range derivatives of the AA-12, but in terms of engagements against other 5th generation fighters, I have to go back to the point that the ability to actually detect and guide to terminal-acquisition at long ranges is questionable. For engaging 4th generation fighters, I concede the longer range variants are more relevant.


Thats assuming that they don't do anything to improve the missile other than the powerplant/range, which as I already mentioned they are ;)

You are right about the KS-172 being pretty much just an AWACS killer, but it does have an impact regardless. If the E-3 is forced to stay 400+ km away from the frontlines, then the F-22s and F-35s will be forced to fight the Russian jets on equal or disadvantageous terms. Turn on your radars to find the enemy then you will be just as visible as an F-15C. Don't use your radar and you run the risk of finding yourself in a WVR dogfight with a highly maneuverable Russian jet. The Russians also have IR guided variants of their BVRAAMs, so would be even more capable of operating in a non-radar environment ;) As the US forces lack a similarly capable missile (compared with the KS-172), the Russians would also be able to bring up their own AWACS planes much closer to the front. At the end of the day, the threat of the KS-172 would make life harder for opposing forces, just like the threat of ballistic carrier-killing missiles has forced US carriers to give China a wider berth.

This is of course a very theoretical discussion over a scenario which is unlikely to happen. It also assumes that the Russians actually manage to complete development all those variants. But hey, our two resident LM PR reps rarely hesitate to bring up laser weapons, CUDA missiles and advanced jammer pods either, sooo...

:)
 
Ozair
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Sat Jan 07, 2017 9:37 pm

WIederling wrote:
The US designs most of their stuff for (preemptive, my ass, nothing to preempt in most cases) attack.

Most other countries, the Soviets/Russians up front design for defence and/or standoff.

??? That makes no sense... Both sides have just as many weapons as each other designed for both attack and defence and no, Russia does not design weapons for defensive purposes only...

VSMUT wrote:
You are right about the KS-172 being pretty much just an AWACS killer, but it does have an impact regardless. If the E-3 is forced to stay 400+ km away from the frontlines, then the F-22s and F-35s will be forced to fight the Russian jets on equal or disadvantageous terms. Turn on your radars to find the enemy then you will be just as visible as an F-15C. Don't use your radar and you run the risk of finding yourself in a WVR dogfight with a highly maneuverable Russian jet. The Russians also have IR guided variants of their BVRAAMs, so would be even more capable of operating in a non-radar environment ;) As the US forces lack a similarly capable missile (compared with the KS-172), the Russians would also be able to bring up their own AWACS planes much closer to the front. At the end of the day, the threat of the KS-172 would make life harder for opposing forces, just like the threat of ballistic carrier-killing missiles has forced US carriers to give China a wider berth.

Your scenario is wrong. Stealth aircraft are not designed to be VLO for radar frequencies only. Stealth aircraft for instance have significantly reduced IR emissions, communications equipment that is very hard to near impossible to detect as well as low probability of intercept radars. LPI radars make your scenario null and void as these radars would make detection very very difficult. It gives the stealth aircraft a significant advantage in being able to identify, target and engage opposing aircraft without being seen. Likely the only notification a targted aircraft would detect is the BVR missile radar going active.

VSMUT wrote:
This is of course a very theoretical discussion over a scenario which is unlikely to happen. It also assumes that the Russians actually manage to complete development all those variants. But hey, our two resident LM PR reps rarely hesitate to bring up laser weapons, CUDA missiles and advanced jammer pods either, sooo...

I'm sure the Russians have plenty of concepts they want to implement, they just don't have the funding to bring most of them into service.

iamlucky13 wrote:

Regardless, there's no sign of shrouding or shaping the nozzles intended as was done on the F-22, and there seems to be less "shadowing" of the nozzles by the tail surfaces, so presumably the rear aspect RCS will be larger than the F-22, and the angle over which the nozzles are visible to radar is probably wider. The F-22 supposedly could have achieved slightly higher thrust and lower weight with round nozzles, so there's an engineering tradeoff for Sukhoi to consider.

I suppose a marketing person would discuss the rear aspect RCS by saying, "The PAK-FA wasn't designed with running away in mind." :box:

RCS is not just about a single aspect, radar energy reflects across the whole airframe so neglecting a specific aspect is somewhat pointless. As for F-22, the performance reduction from round to square nozzles is negligible but round nozzles if designed properly can also be low RCS and IR. For example, the F-35 uses a LOAN, http://www.f-16.net/f-16_versions_article20.html

iamlucky13 wrote:
I wouldn't consider the KS-172 relevant to this discussion since the focus is on fighter vs. fighter encounters. The images that have been shown of that missile indicate high weight and small aero-surfaces, fitting the role of long-range AWACS counter, not a weapon for hitting fighters. Besides, it's too large for internal carriage.

I get the point about extended range derivatives of the AA-12, but in terms of engagements against other 5th generation fighters, I have to go back to the point that the ability to actually detect and guide to terminal-acquisition at long ranges is questionable. For engaging 4th generation fighters, I concede the longer range variants are more relevant.

Longer range does have the advantage of increasing the range of no escape but you need to be able to detect the threat in the first place.

A simplistic scenario is available here, https://www.aerosociety.com/news/does-the-f-35-really-suck-in-air-combat/#sthash.LFir6BjG.dpuf that goes through a typical engagement sequence. A few things wrong with it but it gives a generic idea of how an engagement may go and the advantages stealth aircraft have.

estorilm wrote:
With all of this in mind, just how much worse do you think the RCS of the PAK-FA is from a given angle?

This is Russia's first attempt at a real LO design. They have clearly made trade-offs regarding certain aspects of the design but we have also seen them iterate the design as new test air-frames have been produced. I highly doubt they will get to F-22 or F-35 VLO levels but that probably wasn't the design intention. PAK-FA has the potential to be exported in greater numbers than used by the Russians so a design that is cheap enough and maintainable by their customer base is probably a big factor in their trade-off.
estorilm wrote:
I'm definitely curious about the wing-mounted sensors, I guess the l-band AESA?

The Russians have already released that the L-band system in the wings is for IFF purposes only. It is not a radar used to guide missiles.
 
iamlucky13
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Tue Jan 10, 2017 12:37 am

Ozair wrote:
Longer range does have the advantage of increasing the range of no escape but you need to be able to detect the threat in the first place.


Given the size of the aero-surfaces of the KS-172 images I've seen, I'm not sure it has any no-escape range against fighters aware of and maneuvering to evade them. I think the fighters' main concerns about such a weapon in service would be the threat to their AWACS support.
 
Ozair
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Tue Jan 10, 2017 1:21 am

iamlucky13 wrote:

Given the size of the aero-surfaces of the KS-172 images I've seen, I'm not sure it has any no-escape range against fighters aware of and maneuvering to evade them. I think the fighters' main concerns about such a weapon in service would be the threat to their AWACS support.

Probably, AIM-54 was reportedly not very effective against fighter sized targets either although it all comes down to detection. If you don't know there is a missile targeting you then you are unlikely to conduct evasive manoeuvres.

Just to be clear though, a no-escape zone refers to the kinematic capability of the missile. Essentially, does the missile have the kinematic capability to engage the target no matter how the target moves. For example, if a fighter jet is targeted and a missile is launched at which point the fighter target flows cold (reverses direction) the missile may not have the ability to catch the fighter jet via a tail chase. The ability of the missile to actually hit the target is the pK (involves seeker capability, manoeuvrability of the missile and target, counter measures on both platforms etc) and is not a factor for the calculation of range of no escape.
 
LightningZ71
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Tue Jan 10, 2017 4:19 am

A lot of the AIM 54's problem against fighters was related to mass and speed. At range, it's a big, heavy missile going Mach 3+. It's got a lot of mass and resulting momentum to swing around to hit a maneuvering target. It was designed for two main tasks: hitting Russian bombers attempting to make cruise missile runs against US carriers, and hitting the early Russian fighter sized cruise missiles that those same bombers could launch. That capability became useless once sea skimming cruise missiles were developed (a limitation of the active seeker that was somewhat improved through its life) as did it's role against bombers once the longer range cruise missiles were developed. Of course, the 54's biggest problem was reliability, but that's a different story.
 
User avatar
Synapse
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Wed Jan 11, 2017 7:49 am

No matter, what you think about F-22. No matter, what they think about PAKFA. I bet, they will never fight against each other. There no politician idiots in both countries, that have might to start war US-Russian or NATO-Russian war. Carribbean crysis prooved this. Both fighters have great capabilities against another threats and both fighters have rough parity in economical accessibility considering country economic capabilities. So keep calm and enjoy beauty and power of fifth generation fighter jets)
 
Jano
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Wed Jan 11, 2017 4:44 pm

Synapse wrote:
Carribbean crysis

Crimean annexation?
The Widget Air Line :)
 
Ozair
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Wed Jan 11, 2017 9:26 pm

Jano wrote:
Synapse wrote:
Carribbean crysis

Crimean annexation?

I think he was referring to the Cuban missile crisis but Crimea may be another example.
 
WIederling
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Wed Jan 11, 2017 10:15 pm

Ozair wrote:
Jano wrote:
Synapse wrote:
Carribbean crysis

Crimean annexation?

I think he was referring to the Cuban missile crisis but Crimea may be another example.


Interesting reference.
What came to be known as Cuba Missile Crisis was kicked of with deployment of
Jupiter missiles to sites in Eastern Italy and Turkey.
https://en.wikipedia.org/wiki/PGM-19_Jupiter https://en.wikipedia.org/wiki/Cuban_Missile_Crisis
it ended 6 month after the public "end of Cuba threat" with removal of the Jupiter missiles
as negotiated with the Soviets.

Assume that the "real" Krim Crisis didn't start with the RF taking over the Krim peninsula.
Murphy is an optimist
 
User avatar
Synapse
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 10:43 am

Jano wrote:
Synapse wrote:
Carribbean crysis

Crimean annexation?

I didnot suggest, that Crimean crysis can be compared to Carribean crysis. In 1962 WW3 was feasible. But Crimean people in 2014 upholded Russia, so that was just local conflict between Russia and Ukraine.
 
flyingcat
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 2:52 pm

The Russians invented stealth???

This is like Chekov telling Kirk that Cognac is from Kazakhstan?
 
WIederling
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 3:10 pm

flyingcat wrote:
The Russians invented stealth???

This is like Chekov telling Kirk that Cognac is from Kazakhstan?


https://en.wikipedia.org/wiki/Petr_Ufimtsev

nice gimmick:
https://en.wikipedia.org/wiki/MBB_Lampyridae
They were forced to stop it because the US didn't like it.
Murphy is an optimist
 
tommy1808
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 3:16 pm

flyingcat wrote:
The Russians invented stealth???


No, for real. The west just happened to have Computers fast enough to actually apply the theory to an airframe.

P.Ya. Ufimtsev: Method of Edge Waves in the Physical Theory of Diffraction

The National Air Intelligence Center bought it, translated it, probably violated copyright laws......

best regards
Thomas
Wait for Donalds Trump´s new book: "The Art Of The Retreat"
 
tommy1808
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 3:19 pm

WIederling wrote:
https://en.wikipedia.org/wiki/MBB_Lampyridae
They were forced to stop it because the US didn't like it.


which had lower RCS than the F117 and could, in theory, go supersonic....
Wait for Donalds Trump´s new book: "The Art Of The Retreat"
 
mxaxai
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 6:26 pm

tommy1808 wrote:
flyingcat wrote:
The Russians invented stealth???


No, for real. The west just happened to have Computers fast enough to actually apply the theory to an airframe.

P.Ya. Ufimtsev: Method of Edge Waves in the Physical Theory of Diffraction

The National Air Intelligence Center bought it, translated it, probably violated copyright laws......

best regards
Thomas


And they were developing FBW systems, which help a lot when you are dealing with inherently unstable aircraft, like most stealth aircraft are. Especially on the first model, the F-117, the engineers must have been happy to be able to concentrate on stealth and ignore some aerodynamic caveats. As long as the flight control department knows what it's doing, at least...
 
GDB
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 8:13 pm

WIederling wrote:
Ozair wrote:
Jano wrote:
Crimean annexation?

I think he was referring to the Cuban missile crisis but Crimea may be another example.


Interesting reference.
What came to be known as Cuba Missile Crisis was kicked of with deployment of
Jupiter missiles to sites in Eastern Italy and Turkey.
https://en.wikipedia.org/wiki/PGM-19_Jupiter https://en.wikipedia.org/wiki/Cuban_Missile_Crisis
it ended 6 month after the public "end of Cuba threat" with removal of the Jupiter missiles
as negotiated with the Soviets.

Assume that the "real" Krim Crisis didn't start with the RF taking over the Krim peninsula.


That and the fact that despite his bluster about turning out ICBM's 'like sausages', the General Sec. of the USSR knew full well he only had a handful. very vulnerable in taking days to fuel, also the Soviet strategic bomber force was a fraction of the size of SAC.
He did however have plenty of IRBM's so these were deployed to Cuba, the Jupiter missiles were considered obselete and only a stop gap, their dismantling had been ordered by JFK and he was surprised when the crisis broke that they had not yet been. The intention was that new Polaris subs deployed in European waters would replace them - SSBN's - another area where the USSR was way behind.

Removing the missiles from Cuba was a political issue, more than military, hence JFK blockading the island rather than bombing the missiles, NATO could not be seen to remove systems - however useful they actually were - under duress.
But the Soviet plan would only work if the US was presented with a fait accompli of the SS-4 and SS-5's fully operational before the US found them. As we know, that didn't happen and the rest is history.
 
Ozair
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 9:42 pm

tommy1808 wrote:
WIederling wrote:
https://en.wikipedia.org/wiki/MBB_Lampyridae
They were forced to stop it because the US didn't like it.


which had lower RCS than the F117 and could, in theory, go supersonic....


While I have no problem with the fact that Russian scientists came up with the theory of reflective stealth we need to take a step back and stop these absurd claims on competing designs including the above. No one else has spent even a third of the money on stealth tech development that the US has and they remain the only nation with stealth aircraft in operational service.

The Lampyridae progressed as far as a full scale mock-up, it couldn't fly and was many years from being ready for flight let alone a realistic calculation of its RCS.
 
iamlucky13
Posts: 586
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 10:19 pm

tommy1808 wrote:
flyingcat wrote:
The Russians invented stealth???


No, for real. The west just happened to have Computers fast enough to actually apply the theory to an airframe.

P.Ya. Ufimtsev: Method of Edge Waves in the Physical Theory of Diffraction

The National Air Intelligence Center bought it, translated it, probably violated copyright laws......


It sounds like Ufimtstev didn't develop radar stealth, but did the foundational theoretical work that led to it. I think he could reasonably be called the father of stealth technology, but not the inventor.

Possibly copyright implications of translating a purchased journal article seem to pale in comparison to the usual back and forth technological espionage that has gone on pretty much forever. Strictly speaking, such espionage is illegal. Usually only the messenger gets in trouble, however, while, the government backing them up at worst has to endure a sternly worded letter. For example:
https://en.wikipedia.org/wiki/John_Anthony_Walker
 
WIederling
Posts: 3212
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Thu Jan 12, 2017 10:35 pm

Ozair wrote:
While I have no problem with the fact that Russian scientists came up with the theory of reflective stealth we need to take a step back and stop these absurd claims on competing designs including the above. No one else has spent even a third of the money on stealth tech development that the US has and they remain the only nation with stealth aircraft in operational service.

The Lampyridae progressed as far as a full scale mock-up, it couldn't fly and was many years from being ready for flight let alone a realistic calculation of its RCS.

The full scale RCS results appeared to have been rather promising.
Flyability was proven good. All over pretty good value for the invested money.

And:
Oh, sure. US are best at everything, no inventions ever made beyond the homeland.

It is not what you spend on something but what you get out of that spending.
Stealth for the US was disproportionally expensive.
Murphy is an optimist
 
Ozair
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 13, 2017 12:45 am

WIederling wrote:
The full scale RCS results appeared to have been rather promising.

Do you understand what a full scale mock up is? It is an empty shell, it has none of the avionics systems, radar, communications antennas etc that make up an actual aircraft. Until you add all those systems then there is no way you will get a representative RCS value.

WIederling wrote:
Flyability was proven good.


How did they test flyability on an airframe that never flew?

WIederling wrote:
All over pretty good value for the invested money.

Such good value Germany went on to produce a stealth aircraft?


WIederling wrote:
Oh, sure. US are best at everything, no inventions ever made beyond the homeland.

What are you talking about? The US in not best at everything but when it comes to designing, building and bringing into service stealth aircraft they can rightly claim “best” given they are the only ones to have done it.

WIederling wrote:
It is not what you spend on something but what you get out of that spending.
Stealth for the US was disproportionally expensive.

Perhaps they spent more money on Stealth than they should have but they retain a capability advantage over the rest of the world when it comes to stealth aircraft. They have built four operational stealth aircraft, have three in operational service totalling over 250 aircraft with another thousand aircraft coming in the next 10 years.

Compared to this, Russia has one in development and testing (perhaps 8 aircraft) and China has one in development and testing (perhaps 10 aircraft). While the jury is currently out both rivals do not appear to have gone to the level of RCS and IR reduction found on American designs. Hence the US investment in stealth appears to have and continues to provide them with a capability advantage.
 
tommy1808
Posts: 5000
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 13, 2017 8:21 am

Ozair wrote:
How did they test flyability on an airframe that never flew?


There are those things called "Wind Tunnels" and "Computers", that predict flight performance with high fidelity and have done so for decades.

Such good value Germany went on to produce a stealth aircraft?


Nah, considered a rather pointless enterprise as Radar was considered virtually useless over the WKIII battlefield in Europe with ranges limited to tens of Kilometers at best and even less for fighter radars due to Jamming. The very reason why European fighters of that area got pretty good optical systems .....

best regards
Thomas
Wait for Donalds Trump´s new book: "The Art Of The Retreat"
 
Ozair
Posts: 1509
Joined: Mon Jan 31, 2005 8:38 am

Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 13, 2017 9:43 am

tommy1808 wrote:

There are those things called "Wind Tunnels" and "Computers", that predict flight performance with high fidelity and have done so for decades.

I don't think you understand your claim or you're not being serious. If we have had these things for decades, why do we even bother testing aircraft? Rafale, Eurofighter, F-35, F-22 etc all went through extensive flight test programs. Could you image if the Gripen didn't either and the FCS issues would have manifest themselves during operational service...

tommy1808 wrote:
Nah, considered a rather pointless enterprise as Radar was considered virtually useless over the WKIII battlefield in Europe with ranges limited to tens of Kilometers at best and even less for fighter radars due to Jamming. The very reason why European fighters of that area got pretty good optical systems .....

Well that was a poor bet on behalf of the Germans but your claim isn't supported by reality. For starters the claim there would be that much jamming is absurd, there is simply too much frequency, especially as the frequency gets higher, to cover and during the cold war both sides had anti-radiation missiles and systems to triangulate and target jammers. Second, German F-4s were upgraded with better radars and BVR missiles, right at the time you consider that Germany was deciding that radars would be ineffective. The Germans in concert with the Italians, British and Spanish also started development of the Eurofighter from the middle 80s with a key requirement being long range radar and BVR missiles. The French, Swedes and Americans also didn't seem to think radars would be useless, installing radars and radar guided missiles on all their new airframes.
 
tommy1808
Posts: 5000
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 13, 2017 10:41 am

Ozair wrote:
I don't think you understand your claim or you're not being serious. If we have had these things for decades, why do we even bother testing aircraft?


i said "high fidelity", not 100% perfect match. Name an military aircraft that had significant deviations from predicted performance after the F102 ....

For starters the claim there would be that much jamming is absurd, there is simply too much frequency, especially as the frequency gets higher, to cover and during the cold war both sides had anti-radiation missiles and systems to triangulate and target jammers.


I heard they work on radars too.. so that is a non-argument. The reasoning is the well documented reason behind the Pirate IRST.

Second, German F-4s were upgraded with better radars and BVR missiles, right at the time you consider that Germany was deciding that radars would be ineffective


There was no high-end IRST sensor to put on those fighters and that wasn´t at the same time, but after the USSR seized to be.

The Germans in concert with the Italians, British and Spanish also started development of the Eurofighter from the middle 80s with a key requirement being long range radar and BVR missiles. The French, Swedes and Americans also didn't seem to think radars would be useless, installing radars and radar guided missiles on all their new airframes.


Plus the Key Requirement to be able to use those BVR missiles without the Radar to their full kinetic abilities.

best regards
Thomas
Wait for Donalds Trump´s new book: "The Art Of The Retreat"
 
Ozair
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 13, 2017 11:22 am

tommy1808 wrote:
Ozair wrote:
I don't think you understand your claim or you're not being serious. If we have had these things for decades, why do we even bother testing aircraft?


i said "high fidelity", not 100% perfect match. Name an military aircraft that had significant deviations from predicted performance after the F102 ....

Let us be clear. Your were defending the claim that they were able to determine flyability (whatever that even means) without ever flying the jet. Wind tunnels and computer modelling do not tell you how the jet handles.

tommy1808 wrote:

I heard they work on radars too.. so that is a non-argument. The reasoning is the well documented reason behind the Pirate IRST.

No, the agument is that the frequency range is too broad to cover and there were plenty of counter measures available to combat jamming.

tommy1808 wrote:
There was no high-end IRST sensor to put on those fighters and that wasn´t at the same time, but after the USSR seized to be.

Get your timeline right. First you say after the Germans abandoned the jet it was because radars were useless, then you claim the F-4 mods were too late. The prototype was abandoned in the late 80s, after Eurofighter had started development and just as the Germans decided to mod the F-4s. The F-4 modes happened in 91/92 but the ground work for it happened several years beforehand.

tommy1808 wrote:
Plus the Key Requirement to be able to use those BVR missiles without the Radar to their full kinetic abilities.

I don't deny that was probably a requirement, but it was not fostered from a determination that radar would be useless.
 
tommy1808
Posts: 5000
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 13, 2017 12:38 pm

Ozair wrote:
Let us be clear. Your were defending the claim that they were able to determine flyability (whatever that even means) without ever flying the jet. Wind tunnels and computer modelling do not tell you how the jet handles.


Riiiiight, because FBW systems are programmed out of the blue....
Name a military aircraft that handled badly with absolutely no indication before having a flying prototype.

tommy1808 wrote:
No, the agument is that the frequency range is too broad to cover and there were plenty of counter measures available to combat jamming.


Obviously a whole bunch of experts thought it feasible.

tommy1808 wrote:
Get your timeline right. First you say after the Germans abandoned the jet it was because radars were useless,


Which is was

then you claim the F-4 mods were too late.


You said it was the same time, it wasn´t. The world war III extreme jamming environment scenario didn´t exist anymore, hence Radar was fairly reliable again and it was simply the most cost effective update that was available at that time. They could have bought F-16s of course, which would have been more money for little more efficiency, as Luftwaffe Pilots have conclusively shown in training with the very A2A savvy IAF the F-4F ICEII was almost as effective as their F-16s when used for its mission and adjusted tactics. In fact they achieved a kill ratio of almost 1:1

[quote9The prototype was abandoned in the late 80s, after Eurofighter had started development and just as the Germans decided to mod the F-4s. The F-4 modes happened in 91/92 but the ground work for it happened several years beforehand.[/quote]

It was actually a fairly rush job, as they where never slated for an update, but to be replaced by the fighter 90, which then turned into the Eurofighter with significant delay.

tommy1808 wrote:
I don't deny that was probably a requirement, but it was not fostered from a determination that radar would be useless.


It was. Use as counter stealth wasn´t even in the cards.

best regards
Thomas
Wait for Donalds Trump´s new book: "The Art Of The Retreat"
 
estorilm
Topic Author
Posts: 77
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Fri Jan 13, 2017 2:04 pm

WIederling wrote:
Ozair wrote:
While I have no problem with the fact that Russian scientists came up with the theory of reflective stealth we need to take a step back and stop these absurd claims on competing designs including the above. No one else has spent even a third of the money on stealth tech development that the US has and they remain the only nation with stealth aircraft in operational service.

The Lampyridae progressed as far as a full scale mock-up, it couldn't fly and was many years from being ready for flight let alone a realistic calculation of its RCS.

The full scale RCS results appeared to have been rather promising.
Flyability was proven good. All over pretty good value for the invested money.

And:
Oh, sure. US are best at everything, no inventions ever made beyond the homeland.

It is not what you spend on something but what you get out of that spending.
Stealth for the US was disproportionally expensive.

I believe the monetary disproportion was due to the fact that the US had developed the technology into front-line service (and an actual production-rate) at a time when no one else had - obviously teething problems during the age of slide-rules for design and good old chemistry for RAM production materials probably played a part, at least for the SR-71 - which many forget was initially trashed and sent back to the drawing boards till they could produce a stealthy design (in the wake of Powers).

Many of the aircraft which required a stealthy profile were also inherently complicated and revolutionary in their overall mission profiles as well; ala SR-71, F-117, B1, B2 - which all had many other unheard of specs to meet in addition to stealth (continued into the more modern generations today). Clearly the cost of SR-71 development wouldn't center around "stealth" as much of a factor, yet some may argue that you should toss it in there with "expensive US stealth development" - while missing the big picture; they also achieved a nearly perfect mission-oriented aircraft that was never topped (and never will be).

In any event, I'm glad this turned into an enlightening and informative thread. :)

PS that's really interesting about the L-band wing-mounted sensors being IFF. There were SO MANY rumors about long-range detection, etc.

So what are all these "43 integrated sensors" and such that the aircraft is known for? Long range detection is still relegated to the same AESA tech as the rest, right? However the actual power, along with software / avionics could be DRAMATICALLY different between any given aircraft - and also probably the most top secret elements of all the designs in question. Oh well. ;)
 
Ozair
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Sun Jan 15, 2017 9:50 am

tommy1808 wrote:
Riiiiight, because FBW systems are programmed out of the blue....
Name a military aircraft that handled badly with absolutely no indication before having a flying prototype.

The programing takes ages but good handling doesn't come simply from being FBW. As for an aircraft, classic Hornet had a number of issues that needed to be corrected that were not discovered until flight test. No matter how much time they spent with the software, only flight test detected the issues. Gripen was the same.

tommy1808 wrote:

Obviously a whole bunch of experts thought it feasible.

Can you please point to a report provided by these experts? Given those experts were at odds with the Russians and Americans I think an actual document to review the alleged scenario would improve the credibility of your claim.

tommy1808 wrote:

You said it was the same time, it wasn´t. The world war III extreme jamming environment scenario didn´t exist anymore,

So the Russians just packed up their jammers and went home. Again, the timing you are claiming doesn't make sense. When did the extreme jamming end?
 
YIMBY
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Re: PAK-FA - RCS / stealth design shortcomings? Esp. at rear?

Sun Jan 15, 2017 9:38 pm

estorilm wrote:
PS: I realize that the last statement implies a lack of importance to the aft and belly RCS, which is obvious, but again I'm just thinking hypothetical RCS from a given angle, out of curiosity.


They have made compromises, realising that it is very challenging to have low RCS from the aft without sacrificing performance too much, and virtually impossible to have low RCS from the belly. Those are less important when confronting an enemy fighter, but belly would be important against ground radars and missiles.

Anyway, what compromises they do depends on which missions they design it for. Is it
1) to attack some third world countries while minimizing own losses
2) to make the first strike to West-Europe,
3) to intercept American bombers attacking Russia, or
4) to sell it for other countries or dictators that want more power or higher ego

The Russian air force has always been more defensive than generally believed in the west. The big bomber/strike squadrons of the Soviet Union have been either misinterpretation of intelligence data (Bomber gap) or propaganda of military industry.

The PAK-FA would never enter unobserved to western Europe, unless some countries have neglected to build a credible surveillance or keep sleeping, as I am afraid some do. Probably neither F-35.

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