R-27R, AIM-7M being spoofed by chaff despite target hot and guiding their missiles at gimbals

[SgtPappy]

I have noticed a few instances of a player managing to spoof my AIM-7's in the 80's Blue Flag server while at gimbal limits (i.e. 60 deg. aspect or so). They dive under me, put their radar at gimbals and spam chaff and somehow, the AIM-7 goes stupid even if the target is at Mach 1.2 at gimbals - all the while they are guiding their own missiles. It can't be seen in the tacview, but I never lose lock in these situations.

 

So I tried to do it myself vs AI. I know AI has different chaff and flare rejection characteristics, but it appears that since you can do this stunt at all vs AI means that it would simply take more chaff to do it vs a human player.

 

I do not believe that this should be possible or practical and it seems to be a limitation of DCS. It makes notching an unnecessary tactic at least at these ranges (~10 nm) and also highlights the lack of proper range gating in lookdown situations (i.e. if my target is at 15000 feet, my missiles probably shouldn't be super spoofable if I'm at 17000 feet.

    - spoofing AIM-7 vs AI: https://streamable.com/qmn3bf
    - spoofing R-27R vs AI: https://streamable.com/qmn3bf
    - human spoofing AIM-7: https://streamable.com/hgm3c3 and associated track (sorry I couldn't compress it any more): https://ufile.io/nvufw2zo and associated tacview: https://ufile.io/mvm1xb9w. Another example: https://streamable.com/4qua18 

 

Is my understanding correct? Chaff should be easily rejected at these geometries/ closure speeds but I wonder if I am missing something and this is by design. 

Edited August 16, 2021 by SgtPappy

[lev-kusanagi]

Notching a sparrow at 60 degrees and M1.2 should not be possible. I was there and have also seen the tacviews.

Edited August 16, 2021 by lev-kusanagi

[Cmptohocah]

7 minutes ago, lev-kusanagi said:

Notching a sparrow at 60 degrees and M1.2 should not be possible. I was there and have also seen the tacviews.

 

One can only notch at approx. 90 degrees (no relative radial velocity to the supporting radar), so this was certainly not notchin'.
In DCS chaff act like flares, only for SARH/ARH missiles: you dump enough of them, and they will eventually decoy the missile.

Edited August 16, 2021 by Cmptohocah

[TLTeo]

4 hours ago, SgtPappy said:

Chaff should be easily rejected at these geometries/ closure speeds but I wonder if I am missing something and this is by design

As far as I understand, countermeasures in DCS are just a dice roll on whether the missile tracks or not, and the probabilities are entirely independent of geometry or target speeds, much like RCS is independent of viewing angle and aircraft loadout. Which, of course, is extremely unrealistic and will only be changed when/if we get a whole new EW model.

Edited August 16, 2021 by TLTeo

[Cmptohocah]

3 minutes ago, TLTeo said:

As far as I understand, countermeasures in DCS are just a dice roll on whether the missile tracks or not, and the probabilities are entirely independent of geometry of target speeds, much like RCS is independent of viewing angle and aircraft loadout. Which, of course, is extremely unrealistic and will only be changed when/if we get a whole new EW model.

 

I think chaff should screw with the missile's proximity fuse as well, but I am not 100% on that one.

Edited August 16, 2021 by Cmptohocah

[ruxtmp]

1 minute ago, Cmptohocah said:

I think chaff should screw with the missile's proximity fuse as well, but I am not 100% on that one.

 

For certain missile types it should but is highly dependent on its dispersion and the missile would need to be within the chaff bloom or very close to it. The jammer should also impact fuzing performance on certain missiles, again highly dependent on aspect and range.

[SgtPappy]

19 minutes ago, TLTeo said:

As far as I understand, countermeasures in DCS are just a dice roll on whether the missile tracks or not, and the probabilities are entirely independent of geometry of target speeds, much like RCS is independent of viewing angle and aircraft loadout. Which, of course, is extremely unrealistic and will only be changed when/if we get a whole new EW model.

 

I wonder if there's something that can be done in the meantime.. I mean you can't do this versus an AIM-120 and you cant do it directly facing the shooter while flying at 300 kn and spamming chaff even vs an AIM-7 (or maybe you can?) so perhaps there is a bit more to it than just closure speed. And even then, the guy's closure speed was showing up in excess of 700 kn on the VSD with no indication of my radar losing track (blinking TD box when target is at low closure speed).

 

Maybe there's someone who can share more on the actual requirements of spoofing these missiles because what's then stopping me from just diving under you and popping all my chaff at once ? An extreme case, but I feel that whats happening now isn't far from that.

Edited August 16, 2021 by SgtPappy

[GGTharos]

3 hours ago, Cmptohocah said:

I think chaff should screw with the missile's proximity fuse as well, but I am not 100% on that one.

 

 

You are correct, but the only opportunity is if the chaff is in the missile's flight path.   In DCS this has very little application since chaff doesn't stay in the air long and most trajectories don't go near enough the chaff.

[GGTharos]

@NineLine @BIGNEWY  While this is not a  bug (working as designed), it is not correct.  I think the devs will understand this if you bring this information to them:

 

Currently:

1) Every CM release triggers a 'die roll'

2) The probability of retargeting rises with certain factors such a look down and number of chaff in the view of the missile - the 'incorrectish' part is is bolded (it should be based on chaff RCS)

 

Therefore:

Cap the maximum probability of switching regardless of how many CMs are in view for RADAR only (heat seekers resolve things differently, so this is important) - this can be done in a number of ways:

 

1) Allow only a maximum number of chaff to be considered in the field of view (in other words, your target may drop 100 but you would only consider 3)

2) Cap the maximum number of 'die rolls' to a specific time frame, meaning specifically a delay between each die roll.

3) If possible ensure the chaff effectiveness is based on closure, not aspect (currently based on aspect I believe)

 

Or some combination of the above.   These measures should deal with the problem of raising the probability of retargeting to nearly 100% when dumping high numbers of chaff in a short amount of time

 

 

For reference:  We have the probability of a very old missile, an AIM-7E or perhaps older, switching to chaff on a graph.  The cumulative retarget probability due to chaff is less than 2% at all aspects other than within some 5 degrees of the beam.   While reality is a little more complicated, newer missiles really shouldn't be spoofable head-on, at least not without proper ECM which we don't have in DCS anyway.  So to be clear, R-27Rs, AIM-7Ms, cumulative (this word is important) probability of retarget in any aspect but the beam should be well under 1% IMHO.  It should be there but no one should even be pretending to point at their target if they want to avoid the missile guiding on them.

 

Basically, if the missile doesn't force you to the beam to evade it, the CM retargeting probability is not right.

 

Edit: Removed the reference to 'jaff' after getting better informed on the subject.

Edited August 16, 2021 by GGTharos

[GGTharos]

3 hours ago, TLTeo said:

As far as I understand, countermeasures in DCS are just a dice roll on whether the missile tracks or not, and the probabilities are entirely independent of geometry of target speeds, much like RCS is independent of viewing angle and aircraft loadout. Which, of course, is extremely unrealistic and will only be changed when/if we get a whole new EW model.

 

 

They are completely dependent on geometry, but maybe not closure - geometry is a close enough approximation although not entirely correct.   The problem is that you can spike up the retarget probability high as there's no limit to the cumulative probability for this.

Edited August 16, 2021 by GGTharos

[SgtPappy]

8 hours ago, GGTharos said:

@NineLine @BIGNEWY  While this is not a  bug (working as designed), it is not correct.  I think the devs will understand this if you bring this information to them:

 

Currently:

1) Every CM release triggers a 'die roll'

2) The probability of retargeting rises with certain factors such a look down and number of chaff in the view of the missile - the 'incorrectish' part is is bolded (it should be based on chaff RCS)

 

Therefore:

Cap the maximum probability of switching regardless of how many CMs are in view for RADAR only (heat seekers resolve things differently, so this is important) - this can be done in a number of ways:

 

1) Allow only a maximum number of chaff to be considered in the field of view (in other words, your target may drop 100 but you would only consider 3)

2) Cap the maximum number of 'die rolls' to a specific time frame, meaning specifically a delay between each die roll.

3) If possible ensure the chaff effectiveness is based on closure, not aspect (currently based on aspect I believe)

 

Or some combination of the above.   These measures should deal with the problem of raising the probability of retargeting to nearly 100% when dumping high numbers of chaff in a short amount of time

 

 

For reference:  We have the probability of a very old missile, an AIM-7E or perhaps older, switching to chaff on a graph.  The cumulative retarget probability due to chaff is less than 2% at all aspects other than within some 5 degrees of the beam.   While reality is a little more complicated, newer missiles really shouldn't be spoofable head-on, at least not without proper ECM which we don't have in DCS anyway.  So to be clear, R-27Rs, AIM-7Ms, cumulative (this word is important) probability of retarget in any aspect but the beam should be well under 1% IMHO.  It should be there but no one should even be pretending to point at their target if they want to avoid the missile guiding on them.

 

Basically, if the missile doesn't force you to the beam to evade it, the CM retargeting probability is not right.

 

Edit: Removed the reference to 'jaff' after getting better informed on the subject.

 

These seem like really good ways to make ECM more realistic with the resources available today! Thanks for suggesting them.

 

Just to add to the evidence, I also have a few more clips of the Su-27 and F-15 dodging AIM-7M's by just spamming chaff while at gimbals. I thought I had a good one of the R-27R being spoofed but evidently, I'll have to make more attempts at that. The R-27R is a lot harder to spoof but not impossible (I probably just need to spam more chaff). See below for clips where I maintain lock at gimbals but still defeat several AIM-7Ms launched in MP by my friends:

https://streamable.com/ifslnz

https://streamable.com/wl1gfq

 

And here's one of a Mirage, barely maneuvering managing to do the same thing once again while I had lock the whole time:

https://streamable.com/lkt8v8

Edited August 17, 2021 by SgtPappy

[Cmptohocah]

2 hours ago, SgtPappy said:

The R-27R is a lot harder to spoof but not impossible (I probably just need to spam more chaff). 

 

Wait, what? I mean did I read this correctly?

@SgtPappy I'm goinna go out on a limb here and assume you have never flown a R-27 carrying platform in DCS.

 

Spamming chaff sucks, I hate it my self, but saying that the Alamo has more chaff resistance is just... a no-no.

Please try it out next time in a Flanker/Fulcrum. Untill the latest updates which fixed their performance, Alamos were almost equivalent to rocket-powered stones.

[SgtPappy]

8 hours ago, Cmptohocah said:

 

Wait, what? I mean did I read this correctly?

@SgtPappy I'm goinna go out on a limb here and assume you have never flown a R-27 carrying platform in DCS.

 

Spamming chaff sucks, I hate it my self, but saying that the Alamo has more chaff resistance is just... a no-no.

Please try it out next time in a Flanker/Fulcrum. Untill the latest updates which fixed their performance, Alamos were almost equivalent to rocket-powered stones.

I fly the Su-27 all the time. I never said the R-27R was phenomenal.. both the AIM-7M and R-27R chaff resistance suck, but the R-27R just sucks slightly less. Note that I'm not using the AIM-7MH which might have slightly better chaff resistance than the AIM-7M because you can't control its loft in the F-15.

 

I assume you haven't done the above experiments that I've been doing. Try it with a friend (like with me ). I simply found that I couldn't get the R-27R to bite the chaff in this "gimbal spoof" experiment as often. That's all.

Edited August 17, 2021 by SgtPappy

[Cmptohocah]

37 minutes ago, SgtPappy said:

I assume you haven't done the above experiments that I've been doing....

Guilty as charged.
I have, however, spent 90% of my time in MP on the same server.

[SgtPappy]

@NineLine @BIGNEWY, any idea if this is something that can be looked at? It's fairly influencial to the outcome of a lot of the Fox 1 fights and I would assume it may have some effect on more modern missile encounters as well.

 

Edited August 19, 2021 by SgtPappy

[Hummingbird]

Did a load of experimental flights with Pappy to investigate this issue, and indeed the R-27R is harder to spoof than the AIM-7M.

 

But to get on topic, the fact that chaff works at all when the target isn't at near 90 deg, and there's a very high closure speed, that just can't be right and definitely needs a fix.

Edited August 22, 2021 by Hummingbird

[SgtPappy]

On 8/22/2021 at 12:31 AM, Hummingbird said:

Did a load of experimental flights with Pappy to investigate this issue, and indeed the R-27R is harder to spoof than the AIM-7M.

 

But to get on topic, the fact that chaff works at all when the target isn't at near 90 deg, and there's a very high closure speed, that just can't be right and definitely needs a fix.

 

We did a few more tests and it appears that the AIM-7MH and R-27R are roughly equivalent in being spoofed by these gimbals + loads of chaff maneuvers and the AIM-7M is much more easily spoofed. However all three  - AIM-7M, MH and R-27R are spoofable and it seems only when they are above the target and there's a lot of chaff in their FoV. We clocked closure rates in excess of 900 kn so this is just further evidence that something is amiss. Keeping my fingers crossed that this can be addressed

Edited August 26, 2021 by SgtPappy