AIM-120B (SPAM)RAAM vs (unguided rocket) R-27T

[Cmptohocah]

All jokes a side,

did an online flight after a long time in the non 80's theater and I have a few questions/concerns regarding the performance of the fore mentioned weapons:

 

1. What is the search capability of the AIM-120B once the launching platform has lost lock on the target?
From my flight analysis it's a volume of space that goes at least 40° in vertical and at least 56° in horizontal. This is a huge area to cover and with such a tiny antenna (tiny compared to what fighters have). Frankly, it seems a bit too much. This basically means that AIM-120B is not only "fire-and-forget", but also "fire anywhere and forget" as it does not need support of the launching platform what so ever. Just fire the missile in a general direction and it will take a role of a "tiny fighter" , find the target and lock on to it.

This can be seen on the attached track called track01-search-area-notch.zip at time stamp 00:01:10. The enemy launched the AMRAAM in TWS mode and I have turned cold. The missile clearly flies blind and then acquires me at 56° right of its nose and 20° down. Also it seems not to go below mach 0.7~0.8, but I guess it's cause it lofted earlier and now it's going down.

The case of "fire anywhere and forget" can also be seen in tack02-search-and-r27t.zip at timeline 00:00:16, where the launching platform fired @ roughly 25km and then lost lock.

 

Side view:

Top view:

2. Doesn't the AIM-120B suffer from notching?

In the track track01-search-area-notch.zip at time stamp 00:02:02, two AIM-120C are descending down on me with a 90° angle compared to my plane of motion. This means that my relative velocity in relation to their radar is around 0, and since they are in a look-down situation and I am also dispensing chaff. How is it that they still manage to keep track?
I am not 100% about this one, so if someone with more knowledge on the matter can step in, that would be great.

 

3. Why is the tracking of R-27T so bad?
In the attached track tack02-search-and-r27t.zip at time 00:03:52 I fire first R-27T (unguided rocket) and it looses energy due to enemy maneuvering - nothing strange here. Then at 00:04:04, second R-27T comes of the rail and has a clear line of sight to the target. What it does is, it decides to lock on and destroy the first R-27T that has its engine already burned out. It doesn't go for the flares, it doesn't go for the target's afterburners, but to a trashed rocket that is gliding in the sky. This all happened at around 10km distance from the target.
I was so sure that the missile hit the target, that I actually called out a "splash" - little did I know.

Thanks in advance for reading.
 

tack01-search-area-notch.zip

tack02-search-and-r27t.zip

Edited December 8, 2020 by Cmptohocah
Added comment. Fixed a typo.

[Coxy_99]

ED answer is dont give AF simple.

[Teknetinium]

If AIM-120 dont have magic INS its a Bug.

If AIM-120 go for chaff it is a bug.

If Aim-120 go for Jammers is a bug.

 

AIM-120 is a laser in DCS for long time now :) ED LOL ED 

 

[Coxy_99]

I still see no bug report from EDots on ECM either, 120 didnt hit must be a bug please fix.

[GGTharos]

10 hours ago, Cmptohocah said:

All jokes a side,

did an online flight after a long time in the non 80's theater and I have a few questions/concerns regarding the performance of the fore mentioned weapons:

 

1. What is the search capability of the AIM-120B once the launching platform has lost lock on the target?
From my flight analysis it's a volume of space that goes at least 40° in vertical and at least 56° in horizontal [/quote]

 

either 55 or 60 deg, ie. the entire gimbal space, in a spiral/conical search which happens too fast.  

 

10 hours ago, Cmptohocah said:

This is a huge area to cover and with such a tiny antenna (tiny compared to what fighters have). Frankly, it seems a bit too much. This basically means that AIM-120B is not only "fire-and-forget", but also "fire anywhere and forget" as it does not need support of the launching platform what so ever. Just fire the missile in a general direction and it will take a role of a "tiny fighter" , find the target and lock on to it.[/quote]

 

It is, but if you're out of the way the turn it has to make to get to you will end it with not enough speed to get to you.  So yes, it's wrong and should be dealt with, but it's also not the end of the world.   

 

10 hours ago, Cmptohocah said:

2. Doesn't the AIM-120B suffer from nothing?[/quote]

 

It certainly does, like all radar guided missiles.  However, if you're running around trying to notch at 600kts, you might find it hard to remain in the correct geometry to be successful.  Also, the closer it gets, the less it cares about the notch - but it's always a factor.

 

10 hours ago, Cmptohocah said:

 

3. Why is the tracking of R-27T so bad?
What it does is, it decides to lock on and destroy the first R-27T that has its engine already burned out. It doesn't go for the flares, it doesn't go for the target's afterburners, but to a trashed rocket that is gliding in the sky. This all happened at around 10km distance from the target.[/quote]

 

An unguided missile decided to lock onto something you didn't intend for it to lock-on to?  If this is the case, then maybe you should just consider this a lesson learned

 

If the missile was locked on target there are several things that could happen:

1) The target dumped power and the missile lost lock, started search and found the missile

2) The flares caused or contributed to the break-lock, causing the missile to search again and find the missile

[dundun92]

Yes the AIM-120 suffers for notching quite a bit actually, its far from being a super weapon. BTW, what you were doing isnt notching. Its not about putting your lift vector on him. Its about making a 90° angle between the LOS of the missile and your velocity vector. Your roll has nothing to do with it. Essentially your trying to do this:

 

 

Annotated version of the tacview linked:

 

Here are some videos:

 

Edited December 8, 2020 by dundun92

[Cmptohocah]

@dundun92
I see what you mean, but the point was not the velocity vector.  That line that's extending where my v.v. pokes out, is the actual line of sight from the missile seeker. Now since it's at 90° degrees to my plane of motion, there is no relative velocity between us.
For example if both the missile and I are flying at 100m above ground level, I will enter notch by flying 90 degrees to it's flight path. But imagine that this time the missile is diving at me straight from the vertical - like someone fired it from straight above. I should be able to fly any direction (heading) and I will still be in a notch compared to the missile seeker, since there is no relative motion between us again. In this case I would need to fly either up or down to come out of the notch.

[dundun92]

18 minutes ago, Cmptohocah said:

@dundun92
I see what you mean, but the point was not the velocity vector.  That line that's extending where my v.v. pokes out, is the actual line of sight from the missile seeker. Now since it's at 90° degrees to my plane of motion, there is no relative velocity between us.
For example if both the missile and I are flying at 100m above ground level, I will enter notch by flying 90 degrees to it's flight path. But imagine that this time the missile is diving at me straight from the vertical - like someone fired it from straight above. I should be able to fly any direction (heading) and I will still be in a notch compared to the missile seeker, since there is no relative motion between us again. In this case I would need to fly either up or down to come out of the notch.

Yes, if the missile is right above you youll notch it, because in that case your VV is pointed forwards level at w/e heading, and the LOS to the missile is 90° (straight up). Cos 90° is zero, so yes youd be in the notch regardless of TAS*. But if its say even 5° from vertical, and you flew "away" from it (putting it behind you), youd have cos 85 * 520 kts or 42kts of closure, already enough to put you out of the notch. Again, the simple way to tell if you notching is to measure the angle between the LOS to the missile (pointing from you to the missile) and your velocity vector (straight ahead where you are going)., and multiply its cosine by your TAS You are either trying to minimize cos X (by flying closer to 90°) or your TAS flying slower, or ideally both.

 

*in the diagram above I meant TAS not GS. Point still stands though

 

EDIT I think I see what your saying. It is not 90° relative to your POM. Your POM, aka bank angle, has nothing to do with this. Its 90° between your VV and the LOS. Think of it like your radar's off-boresight/antenta train angle (not quite exact as thats not your VV but your nose position, which differs from your VV by your AoA but it illustrates the point)

Edited December 8, 2020 by dundun92

[Cmptohocah]

49 minutes ago, GGTharos said:

An unguided missile decided to lock onto something you didn't intend for it to lock-on to?  If this is the case, then maybe you should just consider this a lesson learned

 

If the missile was locked on target there are several things that could happen:

1) The target dumped power and the missile lost lock, started search and found the missile

2) The flares caused or contributed to the break-lock, causing the missile to search again and find the missile

I see what you mean, and to be honest it would be great if this kind of thing happened more often on a global scale, as IMHO it would bring the simulation a bit closer to reality - as opposed to the kind of binary system of True/False we have now.
The thing I respectfully disagree with though, is the explanation of loosing lock, searching and eventually finding a new target. Why am I saying this?
Well first of all, there is no way that a burned out missile can give better contrast and IR signature than flares or an aircraft. The missile never went for neither flares nor the target. The argument doesn't stand ground since the 27-T never looses lock to flares and then re-acquires, the target for example. If it does, I would certainly be more than grateful to see a track or a video in action. I am yet to experience this.
I know in RL IR missiles can track many other heat sources than the intended ones, but this is not implemented in DCS.
Also, if you have a look at the first track and the 2nd and 3rd AMRAAM, you can see that they fly right next to each other in close "formation" and they don't interfere with each other at all. Neither of them gets spoofed by the chaff and notching effect are not there.
It seems to me that there might be a slight disparity, but maybe it's just me.
I am slowly reaching a conclusion that only guns solution is the one that can yield optimum results, since extensive flaring/chaffing renders the R-27 family useless even from very short distances.

Sorry for the long post.

 

Edited December 8, 2020 by Cmptohocah

[dundun92]

7 minutes ago, Cmptohocah said:

I know in RL IR missiles can track many other heat sources than the intended ones, but this is not implemented in DCS.

They can in DCS as well, ive had plenty of IR missiles switch targets. Also they will track on the sun as well. There was one case actually where I fired an R-73 at a dude but for some reason went after his incoming AMRAAM and shot it down

 

7 minutes ago, Cmptohocah said:

Also, if you have a look at the first track and the 2nd and 3rd AMRAAM, you can see that they fly right next to each other in close "formation" and they don't interfere with each other at all. Neither of them gets spoofed by the chaff and notching effect are not there.

Because they are radar missiles, and they are already locked on the correct target, they dont switch targets in DCS once locked afaik unless the lock is lost. But if they got within proxy fuze range, they will blow each other up. Also, i have had AMRAAMs ive shot decide to go after the bandits incoming AMRAAm instead of the bandit himself haha.

Edited December 8, 2020 by dundun92

[Cmptohocah]

1 minute ago, dundun92 said:

They can in DCS as well, ive had plenty of IR missiles switch targets.

 

Because they are radar missiles. But if they got within proxy fuze range, they will blow each other up.

Thanks for the reply @dundun92,
what I was referring to in this case were water reflections from the ground, the sun, clouds etc.

What is the difference if they are radar guided or IR when it comes to objects jumping in between the LOS of the seeker and the target?

Do the ARH missiles have a filter to cancel out this effect?

[dundun92]

2 minutes ago, Cmptohocah said:

Thanks for the reply @dundun92,
what I was referring to in this case were water reflections from the ground, the sun, clouds etc.

What is the difference if they are radar guided or IR when it comes to objects jumping in between the LOS of the seeker and the target?

Do the ARH missiles have a filter to cancel out this effect?

I havent seen a missile (Radar or IR) that switched to anything but the sun or CMs while being locked onto a target. When they loose track however, they can go after different targets.

[Cmptohocah]

Nice videos @dundun92 , by the way.

[GGTharos]

7 hours ago, Cmptohocah said:

I see what you mean, and to be honest it would be great if this kind of thing happened more often on a global scale, as IMHO it would bring the simulation a bit closer to reality - as opposed to the kind of binary system of True/False we have now.

 

 

 It would be very nice, but you shouldn't expect it to work anywhere except where you've shot your missile into a furball and it switched for your target to your buddy

 

 

7 hours ago, Cmptohocah said:

[quote]The thing I respectfully disagree with though, is the explanation of loosing lock, searching and eventually finding a new target. Why am I saying this?
Well first of all, there is no way that a burned out missile can give better contrast and IR signature than flares or an aircraft.[/quote]

 

Why?  These things will happily lock onto clouds IRL.  You don't want it to be binary above, but you do over here.  The missile doesn't care which 'signature' you believe it should prefer, it goes for whatever attracts it first after it loses a lock - coincidentally, why pre-emptive flares are effective ... the idea being to get them out before the seeker locks onto anything.

 

Note that missile search patters in DCS are DCSisms.  We don't really know much about what these seekers are really doing.

 

7 hours ago, Cmptohocah said:

 

The missile never went for neither flares nor the target. The argument doesn't stand ground since the 27-T never looses lock to flares and then re-acquires, the target for example. If it does, I would certainly be more than grateful to see a track or a video in action. I am yet to experience this.

 

You're not likely to see this happen because heat seekers are looking through a straw.   It could happen, thus why you can shoot an R-27ET beyond its seeker range and hope that it'll pick something up.

 

7 hours ago, Cmptohocah said:

Also, if you have a look at the first track and the 2nd and 3rd AMRAAM, you can see that they fly right next to each other in close "formation" and they don't interfere with each other at all. Neither of them gets spoofed by the chaff and notching effect are not there.
It seems to me that there might be a slight disparity, but maybe it's just me.
I am slowly reaching a conclusion that only guns solution is the one that can yield optimum results, since extensive flaring/chaffing renders the R-27 family useless even from very short distances.

Sorry for the long post.

 

 

I guess you don't shoot a lot of 120s ... the Pk isn't what us AMRAAM shooters believe it to be.  I guess no one's happy so something's got to be going right

6 hours ago, Cmptohocah said:

What is the difference if they are radar guided or IR when it comes to objects jumping in between the LOS of the seeker and the target?

Do the ARH missiles have a filter to cancel out this effect?

 

Radar guided missiles have at minimum the ability to use doppler and range gates to help them track the 'right thing', both of which heat seekers lack since they cannot measure distance or closure.  They have the ability to estimate or receive a range estimate and count it down for other purposes, but it's not useful for target discrimination.

[GGTharos]

 

7 hours ago, Cmptohocah said:

For example if both the missile and I are flying at 100m above ground level, I will enter notch by flying 90 degrees to it's flight path.

But you have to keep turning.

7 hours ago, Cmptohocah said:

But imagine that this time the missile is diving at me straight from the vertical - like someone fired it from straight above. I should be able to fly any direction (heading) and I will still be in a notch compared to the missile seeker, since there is no relative motion between us again. In this case I would need to fly either up or down to come out of the notch.

IMHO that geometry gives you a momentary reprieve at best.  Think about this.   You're going to blow through that 90 deg 'straight down' angle in no time.   And while not applicable to DCS missiles, it's likely that the missile wouldn't care anyway because at short enough distances the ground won't matter (you're range-gated away from the ground) ... unless you're really close to the ground, and then you just might be safe from a close range shot under exactly correct circumstances.

 

For a longer range shot, you'll exit the notch in no time, unless you're hanging around at low speed and you know exactly where the missile is and you're able to keep yourself in the notch.   And now you're a peeled grape for whatever comes next, so probably time to get the flares out

[Cmptohocah]

5 hours ago, GGTharos said:

 Why?  These things will happily lock onto clouds IRL.  You don't want it to be binary above, but you do over here.  The missile doesn't care which 'signature' you believe it should prefer, it goes for whatever attracts it first after it loses a lock - coincidentally, why pre-emptive flares are effective ... the idea being to get them out before the seeker locks onto anything.

 

Note that missile search patters in DCS are DCSisms.  We don't really know much about what these seekers are really doing.

From what I know, and please correct me if I am wrong, the seeker will lock on to the most radiative source if there are multiple source in its field of view. If the sources have equal level of radiation, it will calculate the average and go for the center of the n (n=2, 3, 4...) sources - which could be between two aircraft, for example.

 

The issue here is that in DCS the seeker sees 3 things equally: R-27T in front of it, flares and the enemy aircraft. As far as DCS is concerned these are designated 3 points in space that could be a potential target and one is chosen. How, now that's a black box for me, but the point is that they are treated as equal. This is the core of the problem. I've posted some months ago a video where my R-73 goes directly to an incoming AIM-120 and not the target aircraft even though the AMRAAM never came into that "straw" as you have described.

Same issue is here with that R-27T: it should go for either the flares which were inside it's straw, the target which was there also or nowhere since the radiation source was lost - just like the R-27R does. 
How did it manage to find the missile in front of it and track it, is a bug in my opinion for the reasons stated above. 

[GGTharos]

6 hours ago, Cmptohocah said:

From what I know, and please correct me if I am wrong, the seeker will lock on to the most radiative source if there are multiple source in its field of view.

Sure, likely, but still 'maybe'.  Most intense from the seeker's point of view, + a bunch of factors.  Fair rule of thumb.

 

6 hours ago, Cmptohocah said:

 

If the sources have equal level of radiation, it will calculate the average and go for the center of the n (n=2, 3, 4...) sources - which could be between two aircraft, for example.

 

Absolutely not.  It doesn't calculate anything at all.  What you describe can happen, but in very specific circumstances that relate to how a spin/con-scan seeker works.  The result probably won't look quite like you're imagining it, but it can certainly lead to a miss (flares take advantage of this behavior to some extent).  In the event that the missile is just a bit smarter and stores targets, it will go for whatever it picks, but it will be a specific target.

 

6 hours ago, Cmptohocah said:

The issue here is that in DCS the seeker sees 3 things equally: R-27T in front of it, flares and the enemy aircraft. As far as DCS is concerned these are designated 3 points in space that could be a potential target and one is chosen. How, now that's a black box for me, but the point is that they are treated as equal. This is the core of the problem. I've posted some months ago a video where my R-73 goes directly to an incoming AIM-120 and not the target aircraft even though the AMRAAM never came into that "straw" as you have described.

 

I'm not saying there aren't problems, but what you're saying implies that you have a far more intense source than another.  A fighter that's gone below MIL might be much cooler than the missile, especially if it is further away (radiated power diminishes very quickly with distance).   This is simulated in DCS to some extent, nothing's perfect.

 

6 hours ago, Cmptohocah said:

Same issue is here with that R-27T: it should go for either the flares which were inside it's straw, the target which was there also or nowhere since the radiation source was lost - just like the R-27R does. 
How did it manage to find the missile in front of it and track it, is a bug in my opinion for the reasons stated above. 

 

Its lock was likely broken and it started a search for a target - this search somehow avoided putting the flares into the FoV, and the first thing it encountered was the missile.   That's not to say that there is no bug - unfortunately, we have no access to EDs tools to verify ourselves (they have tools that draw volumes and  sight lines for the seekers etc)

[Cmptohocah]

On 12/9/2020 at 4:25 PM, GGTharos said:

Absolutely not.  It doesn't calculate anything at all.

 

Cite from "Fighter Combat Tactics and Maneuvering" by R.L. Shaw:
 

Quote

"As the missile approaches the terminal phase it may simply guide on a point near the centroid of the target mass, resulting in a wide miss on any individual target. Passive seekers have a similar problem. When confronted with several hot tailpipes in close proximity, a heat seeker, for instance, may guide on the centroid of the target group based on the relative intensities of the various sources."

So it looks like it does happen.

Edited December 12, 2020 by Cmptohocah

[GGTharos]

Heat seekers don't do this (not to mention they're terminal off-the rail, barring some very modern missiles which he is obviously not describing).   Shaw is fine for describing BFM, for seeker info look elsewhere.

Edited December 12, 2020 by GGTharos

[Cmptohocah]

4 hours ago, GGTharos said:

Heat seekers don't do this (not to mention they're terminal off-the rail, barring some very modern missiles which he is obviously not describing).   Shaw is fine for describing BFM, for seeker info look elsewhere.

 

Ah, I knew you were going to say that. Would you be so kind as to share what sources?

[GGTharos]

Sure thing, here's an example:  https://www.hsdl.org/?view&did=697101

[Cmptohocah]

On 12/13/2020 at 12:02 AM, GGTharos said:

Sure thing, here's an example:  https://www.hsdl.org/?view&did=697101

Had a look a the document: nice read in deed. Could you maybe, direct me which part of it disproves the "going for the centeroid" statement?

 

[GGTharos]

So in the document no centroids are mentioned, and that you have either point targets or extended targets.  Turning a bunch of engines into an extended target would be difficult, and the closer you get the easier it is to resolve individual targets.  The opposite happens when you get extremely close (ie. as you get really, reaaaaaally close the point target looks large) but at this point you have a single target in your FoV.

 

Regarding say, a bunch of aircraft flying really close and presenting something like a single target to the missile from a large (really large) distance, as the missile got closer it would resolve those but of course you cannot guarantee which one it will choose to home in on.  It is very unlikely to go between them, but there are very specific situations where it could do either that or it could go crazy and fly off somewhere random.   This can happen very specifically because of how the detection of targets is done, but it's still not about centroids, it's technical stuff that has to do with this detection signal creating a voltage that will drive the seeker away from the target IF there are multiple targets in very specific positions in the FoV and it may not even be an issue in more modern reticle type seekers.

Edited December 17, 2020 by GGTharos

[draconus]

So WRT to AMRAAM in latest beta:

https://forums.eagle.ru/topic/170893-dcs-world-25-changelog-and-updates-of-open-beta/page/5/?tab=comments#comment-4509488

Quote

 

AIM-120 AMRAAM active radar seeker bug fixing/improvements:

• Fixed HOJ logic, missile will switch between HOJ and active modes if target is lost.
• LOS rate limit computations. Restriction on the angular rate of the line of sight has been restored.
• Fixed visual launch mode behaviour. The missile in this mode no longer receives target designation from the aircraft, but itself searches for a target after launch. The search for the target is provided inside the 15 degrees cone (the width of seeker FOV) right in front of the missile.
• Fixes in seeker target searching logics.
• Introduced last target LOS storing. When the target is lost, the seeker retains its orientation, directed to where the target was.
• Datalink. A fighter-missile line-of-sight check has been introduced.
• Fixed periodical desynchronization of chaff lock in MP.

 

 

Edited December 17, 2020 by draconus

[Cmptohocah]

2 hours ago, draconus said:

So WRT to AMRAAM in latest beta:

https://forums.eagle.ru/topic/170893-dcs-world-25-changelog-and-updates-of-open-beta/page/5/?tab=comments#comment-4509488

 

• Fixed visual launch mode behavior. The missile in this mode no longer receives target designation from the aircraft, but itself searches for a target after launch. The search for the target is provided inside the 15 degrees cone (the width of seeker FOV) right in front of the missile.

 

So I guess this is a bug then right? In the first track (and the screenshots), that I have provided, you can see that the search area is much greater than the stated 15 degree cone. Or am I missing something? It seems that the seeker covers this huge volume in front of it in no time, with the measured angles.