PAK FA vs F-22A

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popcorn

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Unread post09 Feb 2018, 01:36

hornetfinn wrote:The document says that individual Mk-82 bomb has RCS of about 0.05 to 0.1 square meters from most angles. 2 TERs with 6 Mk-82s has RCS of about 0.5 to 1 square meter according to this. Modern A-G weapons likely have a lower RCS than that.

What would your educated guess be for the RCS of an AIM-9X mounted on a F-35 stealth pylon?
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Unread post09 Feb 2018, 02:13

marsavian wrote:
gta4 wrote:
mixelflick wrote:So if they're similar performing machines at low speed and the Flanker holds the edge in acceleration/straight line speed....


This may surprise you, but F/A-18E is at least on par with, or slightly better than Flanker in subsonic acceleration.

A Su-27 single seater at 18920 kg flying weight (very little fuel on board) accelerates from 600km/h to 1100km/h in 15 seconds. Average acceleration is 9.26m/s^2.

A super hornet at 17241kg flying weight (definitely carries more fuel than a 18920 kg Su-27) accelerates from 360 kts to 550kts in 10 seconds, average acceleration is 9.77m/s^2.

During the operation test and evaluation, the F/A-18E demonstrated subsonic acceleration comparable to Mig-29A, which was designated as the "primary threat".


From your figures I make the Hornet's average acceleration to be 6.69 m/s^2. In 10s the Hornet has increased its speed by 31% whereas the Su-27 has increased its speed by 83% in 15s.


I made a typo. F18 accelerates from 360kts instead of 420kts

Figures are from super hornet block ll flight manual.
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element1loop

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Unread post09 Feb 2018, 03:51

citanon wrote:The su57 is a defendor, not a penetrator.

So, I'm wondering if the su57 is meant to be a mainly defensive fighter in Russian service.

In the years since its debut one thing= that's never made sense to me is the apparent neglect of stealth treatment on the bottom of the aircraft.

Today I saw a Russian state media video boasting of the extremely short takeoffs for the su57 and it all started to make sense.

These characteristics:

Stealthy top side, short takeoffs, extreme maneuverability, would make sense for a plane designed from the ground up to work over friendly territory with friendly air defenses to defend against enemy air incursions.

In this scenario, the situation would operate close to the ground, below the altitude of enemy aircraft, as a mobile, stealthy air defense element. This is why most of the stealth treatment is on top.

It will use its speed and the support of friendly iads to close in undetected on enemy aircraft or suspected positions of said aircraft, and engage them in close range fights.

The offensive fight will mostly be left to the army and long range precision fires. The job of the su57 is to buttress aa/ad over friendly territory to allow sustainment of such fires.


Alternatively, it's a product of post-Soviet collapse and extremely limited austerity budget, and desperation, in the face of US 5th-gens, plus Eurocanards.

Which likewise explains the Su35 and late build MiG29s.

In 2005, as F-22A was becoming a thing, RuAF were scarcely able to afford fuell to train pilots and maintain corroding parked aircraft.

As I've pointed out before if you take the rear half of the PAK-AF (ignore the pointy end) it's not much different from an Su35s rump section.

Thus, it's not just the underside which is unimpressive.

And we all know about the intake tunnel design.

No need to over think it, PAK-AF design has a context, it's the product of severe austerity and desperation ... and continues to be that, due to the oil price collapse and sanctions of recent years.

It is as it is, because there were no good finance and tech options available to develop a more impresive design.

They need money - and time - lots of both.
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Unread post09 Feb 2018, 04:30

I mean, the Su-57 is basically nothing more than a stealthified Flanker...
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Unread post09 Feb 2018, 06:26

They've done it before in the Su34 'Platypus', which also has a 'stealthified' nose shaping, a hat-tip to contemporary ATF shaping development when it was being designed, as a development of the Flanker. The proof in the pudding is the evolved AL31 --> AL41 heritage within all three, Su34, Su35 and Su57. No budget for a new donk. No budget for a serious 5th-gen effort. Glorified target drone? ... ok, maybe that's a bit harsh but I wouldn't want to flying one of them into an air battle in 2025 ... nor will anyone else.
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Unread post09 Feb 2018, 07:58

element1loop wrote:
Alternatively, it's a product of post-Soviet collapse and extremely limited austerity budget, and desperation, in the face of US 5th-gens, plus Eurocanards.

Which likewise explains the Su35 and late build MiG29s.

In 2005, as F-22A was becoming a thing, RuAF were scarcely able to afford fuell to train pilots and maintain corroding parked aircraft.



I have no doubt the Su57 is a product of Russia's constraints. What I think is interesting though, is given those constraints, and their inability to do better, could they still come up with a strategy to exploit what they could manage to slap together?

I mean adaptation under austerity is part and parcel of the Russian military hardware heritage.

So, what I'm saying is, given that we accept the Su57 is essentially a modded flanker, what could they get out of it? Could they make it dangerous to our 5th gen aircraft? Could they use it to enhance their offensive posture?

And the answer, I think, is a maybe.
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Unread post09 Feb 2018, 10:38

popcorn wrote:
hornetfinn wrote:The document says that individual Mk-82 bomb has RCS of about 0.05 to 0.1 square meters from most angles. 2 TERs with 6 Mk-82s has RCS of about 0.5 to 1 square meter according to this. Modern A-G weapons likely have a lower RCS than that.

What would your educated guess be for the RCS of an AIM-9X mounted on a F-35 stealth pylon?


That's really tough to say without simulating that with some software. However Brazilians measured their MAA-1 Piranha (basically AIM-9L/M in shape and size) to have RCS of about 0.01 to 0.1 square meters from most angles (except directly perpendicular and directly from behind where there were spikes). AIM-9X and ASRAAM have a lot smaller fins and wings and their shape is better for low RCS. Their IIR seekers are also I'm sure the materials have improved a lot, but the RCS effects are impossible to know from public info.

That Brazilian study:
http://www.jatm.com.br/papers/vol3_n1/J ... 10_GHz.pdf

My guess is that AIM-9X/ASRAAM have RCS of something like 0.001 to 0.01 square meters or better depening on materials used. Being mounted on pylons probably increases RCS somewhat, but pylon could have quite a lot of RAM to help the situation. I think two AIM-9X or ASRAAMs on F-35 will not have that huge impact on RCS. It will increase for sure and there will likely be bigger RCS spikes from some directions. IMO, F-35 will still be a lot stealthier than any other fighter aircraft (besides F-22 of course). I'd guess they will be used when tasked for air to air missions but likely omitted when on air to ground missions against fully operational defenses.
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Unread post09 Feb 2018, 12:00

hornetfinn wrote:
popcorn wrote:
hornetfinn wrote:The document says that individual Mk-82 bomb has RCS of about 0.05 to 0.1 square meters from most angles. 2 TERs with 6 Mk-82s has RCS of about 0.5 to 1 square meter according to this. Modern A-G weapons likely have a lower RCS than that.

What would your educated guess be for the RCS of an AIM-9X mounted on a F-35 stealth pylon?


That's really tough to say without simulating that with some software. However Brazilians measured their MAA-1 Piranha (basically AIM-9L/M in shape and size) to have RCS of about 0.01 to 0.1 square meters from most angles (except directly perpendicular and directly from behind where there were spikes). AIM-9X and ASRAAM have a lot smaller fins and wings and their shape is better for low RCS. Their IIR seekers are also I'm sure the materials have improved a lot, but the RCS effects are impossible to know from public info.

That Brazilian study:
http://www.jatm.com.br/papers/vol3_n1/J ... 10_GHz.pdf

My guess is that AIM-9X/ASRAAM have RCS of something like 0.001 to 0.01 square meters or better depening on materials used. Being mounted on pylons probably increases RCS somewhat, but pylon could have quite a lot of RAM to help the situation. I think two AIM-9X or ASRAAMs on F-35 will not have that huge impact on RCS. It will increase for sure and there will likely be bigger RCS spikes from some directions. IMO, F-35 will still be a lot stealthier than any other fighter aircraft (besides F-22 of course). I'd guess they will be used when tasked for air to air missions but likely omitted when on air to ground missions against fully operational defenses.


Thanks, JPO may be willing to accept a small RCS penalty in lieu of development spending for internal carriage.
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Unread post09 Feb 2018, 12:23

sprstdlyscottsmn wrote:Not going to lie, I thought that would be higher than 1m^2


It is. 1 and 2 refer to the average RCS of Su-27/stealthy Su-27 which according to the right horizontal scale is just over 20 m^2 and just under 10 m^2 respectively.

http://vivovoco.astronet.ru/VV/JOURNAL/ ... STELLS.HTM

Fig. 3. The "facet" model of the Su-27 (above) and the effective scattering surface diagram of the aircraft
as a function of the viewing angle in the horizontal plane (bottom)
The solid line corresponds to the diagram of the scattering of a real aircraft, the dashed line corresponds to an aircraft with a reduced radar visibility; 1 and 2 - averaged over the range of angles ± 30 ° EPR values


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Unread post09 Feb 2018, 14:48

marsavian wrote:
sprstdlyscottsmn wrote:Not going to lie, I thought that would be higher than 1m^2


It is. 1 and 2 refer to the average RCS of Su-27/stealthy Su-27 which according to the right horizontal scale is just over 20 m^2 and just under 10 m^2 respectively.

I was referring to two TERs of Mk82s
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Unread post09 Feb 2018, 17:05

hornetfinn wrote:My guess is that AIM-9X/ASRAAM have RCS of something like 0.001 to 0.01 square meters or better depening on materials used. Being mounted on pylons probably increases RCS somewhat, but pylon could have quite a lot of RAM to help the situation. I think two AIM-9X or ASRAAMs on F-35 will not have that huge impact on RCS. It will increase for sure and there will likely be bigger RCS spikes from some directions. IMO, F-35 will still be a lot stealthier than any other fighter aircraft (besides F-22 of course). I'd guess they will be used when tasked for air to air missions but likely omitted when on air to ground missions against fully operational defenses.


Thats indeed a very low impact on the RCS. I assume Amraam and Meteors RCS should be higher. Whats your opinion about the RCS of fuel tanks? Would be helpful for a discussion in a other thread.
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Unread post10 Feb 2018, 03:22

I used Google Scholar and searched some keywords like "pylon" "RCS", no useful results so far
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Unread post11 Feb 2018, 15:18

hornetfinn wrote:
It's pretty clear that SH has significantly lower RCS than Su-27 or even Su-35S. We don't have exact figures for operational aircraft, but there are lot of modeling software available which can give fairly good idea about RCS of these aircraft. Most models I've seen give roughly those figures but of course it also depends on very small details and materials used. The difference might be bigger in real life as SH seemingly has a lot more work put into those small details.

Weapons and EFTs don't necessarily affect RCS that much (for 4th gen fighters) with modern weapons and tanks that are designed for lower RCS. Western weapons definitely have lower RCS than Russian ones. AMRAAM, AIM-9X and ASRAAM have much better design from RCS PoV than R-77, R-27 or R-73/74 in Sukhois. They have a lot less reflecting surfaces and could easily have order of magnitude lower RCS even with equal materials and built quality. There have been studies made about different weapons. Even old weapons have pretty low RCS:
https://nsarchive2.gwu.edu/NSAEBB/NSAEB ... a51_13.PDF (document by Boeing from 1975)

The document says that individual Mk-82 bomb has RCS of about 0.05 to 0.1 square meters from most angles. 2 TERs with 6 Mk-82s has RCS of about 0.5 to 1 square meter according to this. Modern A-G weapons likely have a lower RCS than that.

Good source
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Unread post11 Feb 2018, 15:23

marsavian wrote:the last few decades has been for combat to become more BVR


Though I firmly believe that the majority of air combat would be BVR, I don't think saying that BVR accounted for the majority of kills during the past decades is a good way to prove this. Because people can counter by saying, the most recent air to air kills the past few years have been WVR.

Just like how a certain set of conditions were met to allow BVR kills in past wars, certain circumstances can also lead to the recent influx of WVR kills as of late.
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Unread post11 Feb 2018, 15:47

zero-one wrote:
marsavian wrote:the last few decades has been for combat to become more BVR


Though I firmly believe that the majority of air combat would be BVR, I don't think saying that BVR accounted for the majority of kills during the past decades is a good way to prove this. Because people can counter by saying, the most recent air to air kills the past few years have been WVR.

Just like how a certain set of conditions were met to allow BVR kills in past wars, certain circumstances can also lead to the recent influx of WVR kills as of late.


We haven’t had any major aerial conflicts since NATO bombed Yugoslavia in the late 90s. Even in the most recent Iraq War (not Gilulf War), there was almost no resistance in the skies.

Most of the shoot downs in the past ~19 years have been between sides that are not officially at war. In “peacetime” conditions, the ROEs are going to be vastly different.
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