Fox3 chaff resistance

[TheAncientOne]

2 patches ago fox3's (especially amraams) were very chaff hungry and went for the chaff all the time when it shouldn't. 

 

Chaff resistance has been buffed, but now it is in the point where fox3 does not go for the chaff at all. Even when you are dropping chaff and go into or through the notch missiles just dont care about chaff now under any conditions. 

 

Aim54's which is really old missile now also do not care about chaff. 

 

There is now no point carrying any chaff. 

 

Maybe the chaff resistance numbers should be revisited cos the buff was overdone?

[nighthawk2174]

IMO its more accurate this way especially for the 120's.  There are numerous ways to reject chaff that these missiles have access too.  Range gating, velocity gating, rejection if outside resolution cell, monopulse seekers can have possible but more limited rejection inside the res cell, rcs edge tracking, and possible other algorithms that can reject the chaff due to sudden RCS changes on the target.  Chaff is just a limited CM, there's a reason western jets moved to towed decoys and a emphasis on stand off jamming.  A document I have, and posted on another thread, was a test of a 50's era pulse tracking radar against chaff and it had a very low chance of break lock against an aircraft dropping chaff; often less than 1%, increasing towards 2% near the beam.

[TheAncientOne]

Don't know. i feel like at least when you get into notch and missile looses track, it should pick up chaff. 

[nighthawk2174]

18 minutes ago, TheAncientOne said:

Don't know. i feel like at least when you get into notch and missile looses track, it should pick up chaff. 

Except the chaff itself looses velocity very quickly, i've seen numbers ranging from 1200-1600m/s.  So it would also fall into the notch very quickly and also fall away from the aircraft very quickly.

Edited July 28, 2021 by nighthawk2174

[GGTharos]

On 7/28/2021 at 4:35 AM, TheAncientOne said:

Don't know. i feel like at least when you get into notch and missile looses track, it should pick up chaff. 

 

 

Why?  I mean it could but it quite just as well not - if you're in the notch, so is the chaff.   This aren't this cut and dry IRL but what is cut and dry is that you're going in one direction and the chaff in another - in fact, from the missile's POV it's more like you're stationary (this is what PN does) and the chaff is shooting off at high speed behind you - all of the filters used to smooth target track would have a good chance of rejecting the chaff.   Perhaps if you were to successfully stay in the notch for long enough, the missile would decide that it needs to throw open the search gates and then there might be a chance that it would pick up chaff.

 

As well, at certain distances where the target SNR is so much more prominent compared to any noise source (clutter for example) it's possible that the clutter notch is removed or maybe even overcome by target scintillation and then chaff would just be useless against anything but a really dumb missile.

 

It's hard to know what all happens for real of course, and chaff isn't going to be entirely useless either - it can be used in combination with ECM which is something that is not at all modeled in DCS. 

Edited August 1, 2021 by GGTharos

[Kula66]

Some interesting comments about early 120As being unable to handle chaff at all: https://podcasts.google.com/feed/aHR0cHM6Ly93d3cuc3ByZWFrZXIuY29tL3Nob3cvNDU3NjE4OC9lcGlzb2Rlcy9mZWVk/episode/aHR0cHM6Ly9hcGkuc3ByZWFrZXIuY29tL2VwaXNvZGUvNDM1MzczMDE?sa=X&ved=0CAUQkfYCahcKEwjg5LriyJLyAhUAAAAAHQAAAAAQAQ

[SgtPappy]

On 7/27/2021 at 7:05 PM, nighthawk2174 said:

IMO its more accurate this way especially for the 120's.  There are numerous ways to reject chaff that these missiles have access too.  Range gating, velocity gating, rejection if outside resolution cell, monopulse seekers can have possible but more limited rejection inside the res cell, rcs edge tracking, and possible other algorithms that can reject the chaff due to sudden RCS changes on the target.  Chaff is just a limited CM, there's a reason western jets moved to towed decoys and a emphasis on stand off jamming.  A document I have, and posted on another thread, was a test of a 50's era pulse tracking radar against chaff and it had a very low chance of break lock against an aircraft dropping chaff; often less than 1%, increasing towards 2% near the beam.

It's a good paper. If anyone is interested, the paper is here: https://apps.dtic.mil/dtic/tr/fulltext/u2/a151928.pdf  Just being nitpicky but fig. 24 shows that the probability of break lock is ~2% for a hot target (table parameters for this simulation shows hot target and the paragraph above that states that the filter easily filters chaff due to the intercept geometry). Fig. 25 shows the the probability of break lock as a function of aspect and it's basically 2% until around 85 deg. aspect and then it shoots almost asymptotically to 100% at 90 deg. This is consistent with old pulse radar. 

 

To add to the above, the newer missiles also have multiple medium PRFs to try and find the target in some clutter clear returns, not to mention the use of Ku rather than X-band for finer resolution. 

 

On 8/2/2021 at 10:42 AM, Kula66 said:

Some interesting comments about early 120As being unable to handle chaff at all: https://podcasts.google.com/feed/aHR0cHM6Ly93d3cuc3ByZWFrZXIuY29tL3Nob3cvNDU3NjE4OC9lcGlzb2Rlcy9mZWVk/episode/aHR0cHM6Ly9hcGkuc3ByZWFrZXIuY29tL2VwaXNvZGUvNDM1MzczMDE?sa=X&ved=0CAUQkfYCahcKEwjg5LriyJLyAhUAAAAAHQAAAAAQAQ

 

Nice! Just because I'm super lazy, do you know which one it is that talks about the AMRAAM? I get a page of several episodes form this link

[nighthawk2174]

5 minutes ago, SgtPappy said:

It's a good paper. If anyone is interested, the paper is here: https://apps.dtic.mil/dtic/tr/fulltext/u2/a151928.pdf  Just being nitpicky but fig. 24 shows that the probability of break lock is ~2% for a hot target (table parameters for this simulation shows hot target and the paragraph above that states that the filter easily filters chaff due to the intercept geometry). Fig. 25 shows the the probability of break lock as a function of aspect and it's basically 2% until around 85 deg. aspect and then it shoots almost asymptotically to 100% at 90 deg. This is consistent with old pulse radar. 

 

To add to the above, the newer missiles also have multiple medium PRFs to try and find the target in some clutter clear returns, not to mention the use of Ku rather than X-band for finer resolution. 

 

 

Nice! Just because I'm super lazy, do you know which one it is that talks about the AMRAAM? I get a page of several episodes form this link

Yes i've also posted this paper in other threads, considering the tech difference between a PD/Monopulse/Ku band/Digital electronics amraam and this radar heavily implies that chaff has a significantly lower chance of break lock.

[Kula66]

1 hour ago, SgtPappy said:

Nice! Just because I'm super lazy, do you know which one it is that talks about the AMRAAM? I get a page of several episodes form this link

Episode 6 Weapons A/A  .. but before you ask, I can’t remember the exact time, sorry.

Edited August 8, 2021 by Kula66

[SgtPappy]

9 hours ago, nighthawk2174 said:

Yes i've also posted this paper in other threads, considering the tech difference between a PD/Monopulse/Ku band/Digital electronics amraam and this radar heavily implies that chaff has a significantly lower chance of break lock.

Haha at this point I think we're just quoting each other because we spend so much time on these kinds of threads 

 

8 hours ago, Kula66 said:

Episode 6 Weapons A/A  .. but before you ask, I can’t remember the exact time, sorry.

 

 

I think I'd be a bit too lazy if I asked that. Thanks!