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Aim-120 Range


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The problem is that the radar sees the chaff, but its autopilot should reject the chaff if new target suddenly doesn't match the previous track history.

 

DCS missiles vs real world missiles... I don't think DCS CM modeling is any more than each chaff /flare has some x% chance of decoying the missile.

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DCS missiles vs real world missiles... I don't think DCS CM modeling is any more than each chaff /flare has some x% chance of decoying the missile.

 

Yeah there ain't difference.

 

Chaff is same as Flare. You get a few seconds (IIRC some developer said it was 4 second lifetime) to roll a dice that does missile seek to CM or not.

 

One thing that should be clearly improved as chaff should be up there for hours if not even day or two, blocking the radar emissions nicely and causing lots of trouble for everyone.

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Fire in TWS, Mach 1+ and from 25.000+ feet then you'll get 20nm shots easily. Especially against AI, which just flies into TWS launches. The 120 is currently one of the best misiles we have in game so it is entirely on you to employ it correctly.

 

I was practicing TWS in the Viper and couldn't get close to 20nm shots. Nose-on, bandits at 22,000ft M0.8~M0.9, me at 31,000ft M1.1, and I didn't get a max-range firing solution until 17nm....

 

Meanwhile the bandits already had R-27s in the air at 20nm separation....

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I was practicing TWS in the Viper and couldn't get close to 20nm shots. Nose-on, bandits at 22,000ft M0.8~M0.9, me at 31,000ft M1.1, and I didn't get a max-range firing solution until 17nm....

 

Meanwhile the bandits already had R-27s in the air at 20nm separation....

The DLZ of the F-16 might be messed up. I don't even use it really. Kills from 20-25 nmi are possible, though the AMRAAM likes to go for chaff and the AI knows how fast your missiles are traveling, so they know when they can just turn around and run.

 

 

Also note that the AI doesn't take into account that you will maneuver after a shot. If you charge them at high alt and speed they will fire a missile that will hit you if you don't turn. If you do turn the missile will struggle to reach you.

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The problem is that the radar sees the chaff, but its autopilot should reject the chaff if new target suddenly doesn't match the previous track history.

 

For that second turn it is not on track not even it's radar cone, but still it goes for chaff

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For that second turn it is not on track not even it's radar cone, but still it goes for chaff

That's because missile radar seeker limits are too wide in DCS. FOX 3 missiles often keep track of targets that would normally be outside of their seeker limits.

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The problem is that the radar sees the chaff, but its autopilot should reject the chaff if new target suddenly doesn't match the previous track history.

 

It should see the chaff as target with windspeed doppler shift .. so essentially chaff is in the notch filter immediatly if below horizon or otherwise should be rejected quickly by track integration and doppler shift of the real target.

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When the chaff is dropped in the notch the missile cannot differentiate between real target and chaff, because the monopulse seeker receives a mix of target and chaff return, and in the notch they are within the same frequency and range. So the monopulse seeker does not see two independend targets where he can decide which one to take, the seeker sees just one target that is a mix of both targets the same time.

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When the chaff is dropped in the notch the missile cannot differentiate between real target and chaff, because the monopulse seeker receives a mix of target and chaff return, and in the notch they are within the same frequency and range. So the monopulse seeker does not see two independend targets where he can decide which one to take, the seeker sees just one target that is a mix of both targets the same time.

 

True. That is the one point where chaff makes sense.

In reality you would want to make sure to have little doppler shift to the target, dump out an ample amount of chaff and cause the radar that's painting you to go back to search mode to reaquire you among the mess.

 

Then you want to do an in plane maneuver (split-s or something) that points you at a place where the radar doesn't expect you to be by the time it reaquires, so that the lock breaks.

 

 

In DCS however chaff is currently working very weirdly. Let A (flying upwards) be the target aircraft, C be chaff and M be the missile flying and steering towards A. Then there is still a change in the depicted situtiation that the missile will turn 90° and go for the chaff, and that's wrong.

 

A
|
|      M
|       `---
|
C

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It should see the chaff as target with windspeed doppler shift .. so essentially chaff is in the notch filter immediatly if below horizon or otherwise should be rejected quickly by track integration and doppler shift of the real target.

 

Chaff is not "zero speed". It is not a big brick wall that just hangs in the sky.

 

The chaff is full of tiny pieces that are specifically designed for the radars emissions so that when they move in the sky, they constantly and extremely rapidly cause huge speed changes for the radar. They effectively blocks the radar visibility through them, and they stay up in the air for hours or days even depending weather.

 

You can't see the doppler effect as for the radar that area is constantly moving huge target at rapid manner. And as it is your own real radar signature, you are blinded effectively.

 

The current missiles doesn't seem to have anything of the real radar beam scanning, no search patterns, no logic what to do when the target is lost, no idea what to do when they see suddenly multiple targets at various speeds going various directions etc.

 

It is just rolling a dice that is it locked or not in given time.

 

Current chaff in DCS is like a flare is to IR missile. Just a multiplier, so chaff enough and you increase change that missile is forced to lock on one of them.

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For that second turn it is not on track not even it's radar cone, but still it goes for chaff

 

The chaff that missile will lock on, is released just second before the missile locks to it. And there were even the fuel tanks ejected on the same time, creating a third target trajectory. Missile doesn't know should it follow the fighter, fuel tanks or a chaff.

 

It is well in the missile radar cone, and it is exactly in the logic for the missile to see that target size increase and missile rejects the real target.

The problem is just that the chaff works extremely simple manner, and even too ineffectively. But it does correct thing.

 

The missile seeker is not directly to its vector, it is looking at the target continually to its left. When the chaff is released, the seeker sees the target speeds to change high and low, size gets increased and missile needs to start performing that does it chase a big large return thats speed is constantly changing, or does it go in blind faith to previous intercept point that was calculated by previous X seconds.

 

Missile doesn't know where the target is, it just knew where it was suppose to be going, and then when chaff is released it gets new possibilities where it should be going.

Because chaff is spread on the sky, it doesn't become invisible because it is traveling below doppler filter speed.

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Chaff is not "zero speed". It is not a big brick wall that just hangs in the sky.

 

The chaff is full of tiny pieces that are specifically designed for the radars emissions so that when they move in the sky, they constantly and extremely rapidly cause huge speed changes for the radar. They effectively blocks the radar visibility through them, and they stay up in the air for hours or days even depending weather.

 

You can't see the doppler effect as for the radar that area is constantly moving huge target at rapid manner. And as it is your own real radar signature, you are blinded effectively.

 

 

I really want to understand it physically.

I understand that chaff is essentially hanging in the air at wind speed. It doesn't have it's own propulsion, but as leaves in the wind, it can have an oscillation or movement of sorts.

I understand that this will create all sorts of echos for a radar for whos frequencies it was designed / cut to length. However, I don't understand how it should ever have a doppler shift high above ambient wind speeds + glide to a degree where it wouldn't be rejectable by a pulse doppler radar.

 

Any information on that is welcomed!

 

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Agreed plus one has to keep in mind unless the chaff is at the specific cut length (and orientation) for the radar its countering its effectiveness falls off exponentially.

jDpgk8B.png

For example this is from a doc called Chaff Countermeasures and Air Defense design, which was declassified in the 70's and is not restricted in any way. As you can see each specific cut works really well for only a really small set of frequencies. I have a doc somewhere (need to find it) with a similar chart to the above for the chaff used by navy aircraft in - I believe - the late 80's to mid 90's. And even though it covered a broader spectrum of frequencies it still had the issues of frequencies where it had limited effectiveness. Also with chaff bundles one has to wonder how long does it remain in a cloud with enough density to prevent radar signals from effectively passing through them? Especially for the small bundles used in aircraft self protection.

 

Additionally as far as I understand it the effect you see is more of a range of Doppler shifts instead of a point target:

Ahmuapn.png -from same doc as above image

I need to read the document again but I believe this was the basis for some filtering techniques that were proposed for Air to Air radars.

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Thank you for the information, nighthawk2174!

 

I am trying to wrap my head around the fact that 10.000 mini dipoles might create a doppler shift higher than a not-notching target. or even broader spread.

I would have understood if there was some spread around the ambient wind speed, but nothing that would come close to a jet plane.

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Does anyone know if the AMRAAM got updated yesterday (2.5.6)? Whether it did or did not, I still believe it is underperforming. Example, two F-16’s head on, both Mach 1, 30000ft, opponent fires Aim-120c at 11nm, Defender (me) performs split S at 10nm and burns for the deck, AMRAAM looses energy and misses, closest point, a bit under half a mile. Example 2, F-16 and Jf-17, same physical parameters as in example one, opponent fires SD-10 at 11nm, defender performs split s at 10nm and burns for the deck more aggressively than before, SD-10 successfully intercepts. In reality Aim-120c should be equal or better in performance to SD-10, not completely inferior. Will we see more improvements to the Aim-120 that will bring it up to par with the Sd-10 or is this the end of the line? I for one think the SD-10 is a perfect benchmark to shoot for.


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Thank you for the information, nighthawk2174!

 

I am trying to wrap my head around the fact that 10.000 mini dipoles might create a doppler shift higher than a not-notching target. or even broader spread.

I would have understood if there was some spread around the ambient wind speed, but nothing that would come close to a jet plane.

 

Think it this way. Each emission you send to chaff, each tiny piece of chaff is quickly scattered to large area. Each individual piece is rotating at high speed all directions. And each tiny piece is designed to be maximum at reflectivity for given frequency.

 

Now you have multiple pieces at wide distance from each others, causing you a "mirror effect" where your radar is measuring huge speed differences as one microsecond the signal is close, on other it is far further, then again somewhere else in distance.

 

The radar sees chaff as multi-dimensional high speed object that it can't detect as solid or stationary, or even moving.

 

Chaff basically jamms your radar to see things that ain't there, at speeds that ain't there, yet is.

 

Your radar sees huge Doppler effect happening inside the chaff, regardless the chaff is floating at speed of the air, spreading quickly to large area and distracting visibility through it, to both ways.

 

As your radar has limited resolution, it can't make out the chaff size nor speed nor direction. It just is "black hole" that is solid. And as it is not a known, you can somewhat filter it out, but you are filtering your own radar emissions continually.

 

The easiest way is simply make an logic. If you track object for 10 seconds and it moves 550km/h to given vector, if it suddenly does stop or alter heading but something continues movement to last known prediction based last 10 seconds, then logical is to follow the prediction instead new measurement. But as the missile is to go largest return, that has speed, chaff becomes very attractive, especially when it is between target and radar, effectively hiding the target.

 

Now here is a question. Missiles with proximity fuses should as well blow themselves up when they fly through chaff, as the chaff will trigger proximity radar by returning the signal. Now that doesn't happen in dcs but missiles flies just trough the chaff. Because chaff is already gone in few seconds after release.

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  • ED Team
My understanding is that previously ED only had a sort of fixed drag curve that could be shifted up/down in terms of CD, but the curve was not accurate at high Mach.

 

 

The new curve gives them more control, so missile drag at high M increased according to CFD results, but at mid and low M the CD is down. Lift increased massively, which is what really gives the AIM-120 the improved range with the latest flight model. It's harder to get them to loft now, but when they do they lose a lot less speed pulling out of the loft because they don't need as extreme an AoA to maneuver.

Yes, right.

 

If the loft is updated to let the missile cruise at altitude and avoid going into the dive too early and too eagerly I expect the AIM-120 to get another significant range boost.

We are working on it.

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  • ED Team
Does anyone know if the AMRAAM got updated yesterday (2.5.6)? Whether it did or did not, I still believe it is underperforming. Example, two F-16’s head on, both Mach 1, 30000ft, opponent fires Aim-120c at 11nm, Defender (me) performs split S at 10nm and burns for the deck, AMRAAM looses energy and misses, closest point, a bit under half a mile. Example 2, F-16 and Jf-17, same physical parameters as in example one, opponent fires SD-10 at 11nm, defender performs split s at 10nm and burns for the deck more aggressively than before, SD-10 successfully intercepts. In reality Aim-120c should be equal or better in performance to SD-10, not completely inferior. Will we see more improvements to the Aim-120 that will bring it up to par with the Sd-10 or is this the end of the line? I for one think the SD-10 is a perfect benchmark to shoot for.

Right now flight dynamic of 120B/C close to real prototypes.

About SD-10 I can't say nothing because it is not ED missile.

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  • ED Team
Are we at least going to get those 300 knots back that nighthawk was talking about or is that cfd result final?

We are working on a new flight dynamics of 120. It will be built on new principles and much deeper. We use a virtual wind tunnel. I can’t say what will be have in final.

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