AIM-54 Probability of Kill

[Hornet_Driver]

Judging by many multiplayer sessions, Phoenix seems to be much easier to deceive both by Chaff and Evasive maneuvers. Do you also find it to be the case? How would you compare the probability of kill to the AIM-120?

[Skysurfer]

Judging by many multiplayer sessions, Phoenix seems to be much easier to deceive both by Chaff and Evasive maneuvers. Do you also find it to be the case? How would you compare the probability of kill to the AIM-120?

 

Yes, it is several magnitudes easier to defeat than the AMRAAM currently and it loves chaff. I have no statistics on it but simply put it's fairly easy to defeat a Phoenix if you know what you are doing. Within the same range (as long as it matches lethal AMRAAM range) the AMRAAM will usually come out on top. At very long ranges or in a chase obviously the Phoenix is superiour. I think once the improved and proper PN methods and active command guidence is finally implemented we'll see reliabilty go up - ccm is also in need of some adjustments, especially for the C model.

[BreaKKer]

 

Yes, it is several magnitudes easier to defeat than the AMRAAM currently and it loves chaff. I have no statistics on it but simply put it's fairly easy to defeat a Phoenix if you know what you are doing. Within the same range (as long as it matches lethal AMRAAM range) the AMRAAM will usually come out on top. At very long ranges or in a chase obviously the Phoenix is superiour. I think once the improved and proper PN methods and active command guidence is finally implemented we'll see reliabilty go up - ccm is also in need of some adjustments, especially for the C model.

 

Don’t forget the ED missile guidance. The missile API is still WIP on the phoenix

[Skysurfer]

 

Don’t forget the ED missile guidance. The missile API is still WIP on the phoenix

 

Has been for over a year now. And they still are changing the amraam around constantly. We shall see down the road.

[SgtPappy]

Something I noticed however is even the A-model Phoenix is far less likely to be notched when launched looking up at less than 20 nm - heck I had trouble from 30 nm trashing its seeker. I tested it online with a friend and offline against AI and I can only orthogonally dodge it, run it out of energy or die if its looking up at me within say, 15 nm. I seem to have trouble using chaff against it while its looking up even if I'm split-S'ing.. don;t know if that's just me.

 

However, it will forget about you if you beam and force it to look down at all it seems - even if you are about say, 1000' above the ground. I would think you'd need to be much closer to the ground to notch it, but then again it is old, probably has no beam sharpening capabilities and therefore has a large resolution cell.

[SgtPappy]

Just did some tests and I'm checking back - it appears if you launch the AIM-54A (also tried a test with the AIM-54C) and you're looking up at the target, it cannot be spoofed by chaff with beaming and split-S from seemingly any range. The F-14 might lose lock but the active off the rails AIM-54 will keep seeking. See the attached tacviews for reference. Of course this is not a comprehensive of completely conclusive tests, but it is consistent with what my friend and I tried online when I was above him - the AIM-54 simply will not lose track except by look-down, beam shots i.e. notching (which admittedly is still very easy, unlike for the AIM-120).

 

If this is accurate that is a big bonus for the F-14 as long as it flies really low as the bandit defends but from what little I know during my research, I'm having a rough time believing that this should be the case. The AIM-54 radar diameter is slightly smaller than the missile diameter at about d = 0.380 m. At X-band, let's say carrier frequency, f = 9GHz, then wavelength, λ = 0.033 m the angular resolution would be θ ~= 0.033/0.380 = 0.08766 radians = 5.022 deg. This is pretty big, and so the cross-range of the resolution cell at, say 5nm would be R = θ*5nm = 0.08766*5 = 0.438 nm = 0.813 km which is pretty huge. With such a large cell, I would expect chaff from, say, the standard USAF RR-170 cartridge (3 million dipoles, maybe 25% of which are X-band) would give an RCS of ~80 or more m^2 and that would be enough to pull the RCS centroid away from the aircraft at that range.

 

The AIM-54 is a very early mech-scan (i.e. no beam shaping) seeker so I don't find it sorta hard to believe that it won't eat chaff at that range. Not sure if this is the intent of the current missile modeling. But I'm up to be proven wrong, this is just my feeling based on what I know.

AIM-54A tests.zip

[dundun92]

It depends on the manuever. Both the AMRAAM and AIM-54 are easy to notch if you know how to notch properly. The 54 simply has MUCH more room for error. If you mess up notching an AMRAAM you will eat it almost 100% of the time. Ive only seen AMRAAMs notched "accidentally" once or twice. You can do a sloppy notch vs a 54 and still evade it. You can do it by accident just by panicing and spamming chaff. Describing it in % is pretty pointless barring tests under specific, controlled circumstances.

[SgtPappy]

I agree about the AMRAAM and yes, if the AIM-54 is looking down in basically any capacity, it's notched. That much I can confirm. So maybe it is just me for now but there was a time when simply beaming it even in a lookup situation would completely defeat it (probably not realistic either). Popping chaff made that easier. Now it seems chaff and beaming and even maneuvering in that beaming plane does absolutely nothing if and only if it is looking up. If you have the time, you can see the tacviews.

 

Now I'm not able to truly conclude this is unrealistic but I'm leaning towards it is not based on my limited knowledge about radar resolution and the effect of chaff on an old missile like this. But something just seems off - if the F-15, Mirage, Hornet and Viper all lose radar lock from a beaming, maneuvering plane dropping chaff at 8 nm in clear air at co-alt, the AIM-54 with its old seeker and tiny aperture/array should not be any better at 5 nm for example. It's a matter of consistency I suppose, the way I see it.

[Noctrach]

Just did some tests and I'm checking back - it appears if you launch the AIM-54A (also tried a test with the AIM-54C) and you're looking up at the target, it cannot be spoofed by chaff with beaming and split-S from seemingly any range. The F-14 might lose lock but the active off the rails AIM-54 will keep seeking. See the attached tacviews for reference. Of course this is not a comprehensive of completely conclusive tests, but it is consistent with what my friend and I tried online when I was above him - the AIM-54 simply will not lose track except by look-down, beam shots i.e. notching (which admittedly is still very easy, unlike for the AIM-120).

 

The AIM-54 is a very early mech-scan (i.e. no beam shaping) seeker so I don't find it sorta hard to believe that it won't eat chaff at that range. Not sure if this is the intent of the current missile modeling. But I'm up to be proven wrong, this is just my feeling based on what I know.

 

No missile in DCS is notchable when they're looking up even 0.1 degree above the horizon. Background clutter is simulated as "below the horizon", not based on chaff or actual background. This also means notching at 30,000 feet is just as effective as notching at 5 ft.

 

The idea that chaff will create some high-clutter background for PD sensors is a fallacy that I see oft repeated on the forums. This is absolutely true for Pulse-based radar tech, but for PD ones the effect of chaff is minimal, exclusive only to the expansion/bloom fase of the countermeasure. This lasts about half a second. Essentially what you do with a chaff release is create a very large temporary return in the hopes that the PD sensor mistakes it for your aircraft and loses the track, even if only shortly, while you execute an evasive manoeuvre trying to avoid the reacquisition search pattern when the chaff gets inevitably filtered out. Chaff without other ECM is pretty much meaningless to modern PD arrays and had very limited effectiveness against radars in even the 70s and 80s.

 

A mech-scan array might have more trouble keeping up with a fast-jinking target, but it won't change the chaff-eating tendencies. If anything it will just increase the notch-gate so chaff gets filtered out rather faster. It's still a PD sensor, not a Pulse one. Easier to notch, yes, easier to chaff, no.

Which is also the case in DCS... Phoenix notch gate is a lot larger than other missiles or planes, hence why you see people accidentally notching it.

Again with the caveat that the missile has to be looking down.

 

In DCS chaff is invisible to aircraft radars, so you won't be breaking lock. Instead it's simulated to have a % chance to attract a missile in flight towards the aircraft that launched the chaff, but only if the missile is nose down at least a fraction of a degree. (This does mean that you can complete spoof STT missiles even when the launching aircraft has a steady look-up lock, but that's a different topic...)

[TLTeo]

SgtPappy, your estimated make sense but by following that assumption (detector angular resolution being the main driver for whether a missile eats chaff or not), pretty much every other active radar homing missile should have much worse chaff resistance than the Phoenix because they are smaller missiles carrying smaller dishes. It's clear that at some point, the initial assumption must break down, and the simple modelling of CMs in DCS likely makes it very hard to capture these effects properly.

[SgtPappy]

 

No missile in DCS is notchable when they're looking up even 0.1 degree above the horizon. Background clutter is simulated as "below the horizon", not based on chaff or actual background. This also means notching at 30,000 feet is just as effective as notching at 5 ft.

 

The idea that chaff will create some high-clutter background for PD sensors is a fallacy that I see oft repeated on the forums. This is absolutely true for Pulse-based radar tech, but for PD ones the effect of chaff is minimal, exclusive only to the expansion/bloom fase of the countermeasure. This lasts about half a second. Essentially what you do with a chaff release is create a very large temporary return in the hopes that the PD sensor mistakes it for your aircraft and loses the track, even if only shortly, while you execute an evasive manoeuvre trying to avoid the reacquisition search pattern when the chaff gets inevitably filtered out. Chaff without other ECM is pretty much meaningless to modern PD arrays and had very limited effectiveness against radars in even the 70s and 80s.

 

A mech-scan array might have more trouble keeping up with a fast-jinking target, but it won't change the chaff-eating tendencies. If anything it will just increase the notch-gate so chaff gets filtered out rather faster. It's still a PD sensor, not a Pulse one. Easier to notch, yes, easier to chaff, no.

Which is also the case in DCS... Phoenix notch gate is a lot larger than other missiles or planes, hence why you see people accidentally notching it.

Again with the caveat that the missile has to be looking down.

 

In DCS chaff is invisible to aircraft radars, so you won't be breaking lock. Instead it's simulated to have a % chance to attract a missile in flight towards the aircraft that launched the chaff, but only if the missile is nose down at least a fraction of a degree. (This does mean that you can complete spoof STT missiles even when the launching aircraft has a steady look-up lock, but that's a different topic...)

 

 

What is fallacy is the idea that the chaff is a high clutter background "mask" that planes hide behind when attempting to defeat PD radars. Although I realize it is possible to still reject chaff based on the bandwidth of the return (it's all over the place compared to a plane and the aircraft will move away from a bundle quickly if not maneuvering), a maneuvering aircraft in the beam, constantly popping chaff could really create an angular pull-off given a large enough resolution cell, PROVIDED there is no fancy ECCM or beam shaping.

 

At the end of the day, I'm wondering about consistency - in the context of DCS, then no working AIM-7 or S530D should miss when I pop chaff and split-S while beaming those radars in a look-up situation yet they do. In fact, none of those radars should ever lose lock but we see that all the time, even just beaming while far away, looking up sometimes even. So even then, we are simply inconsistent, no matter what the truth is about chaff. If missiles of this class truly only can be notched then they should ALL only be notchable and ONLY in the look down situation today but that is not the case.

 

What I have shown below is not proof that chaff MUST work in the beam with a maneuver without jamming, but it is simply to show that using chaff could possibly break lock with a beam maneuver. That is, can we really conclude from what information we have today that chaff does not work against a PD radar ever looking up? I would think no but I certainly would not mind being proven wrong as this question has taken up almost the entire year for me and this plus the associated texts' calculations are what I've managed to find so far.

 

"Radar homing Guidance for Tactical Missiles" - D. A. James:

"Chaff can, however, be more effective if the target is crossing at the time of acquisition, since the target has no component of velocity towards the missile and the chaff Doppler frequency may fall within the search ambit of the Doppler frequency gate. Even under these circumstances it may still be possible to reject the chaff echo on the basis of range as the chaff separates from the target, by using pulse-Doppler; the seeker would discriminate between the target and the chaff, each in its own range interval, by the broader frequency spectrum of the wind-blown chaff. "

 

"Monopulse Principles and Techniques, 2nd Ed". - S. Sherman, D. Barton -

"An aircraft self-protection technique, when under track by a weapon-control radar, is to release one or more chaff bursts while executing a turn that brings the aircraft radial velocity to zero (relative to the air mass). If the radar cross section of the chaff exceeds that of the target, the chaff echo may capture the radar track, allowing the target to move, unseen, out of the beam. The weapon system must recognize this event and reacquire the target to restore the needed guidance data."

 

DTIC paper "Self-defense of large aircraft" - Yildirim, Z. -

"Some radars ignore a chaff cloud because its velocity decreases rapidly. To defeat this problem, aircraft should dispense a series of chaff clouds, rapidly and in a sequence according to enemy radars’ capabilities. It produces the illusion that the cloud is traveling at nearly the same speed as the aircraft. The rapidly dispensed chaff clouds will ”walk” the radar behind and off the aircraft as in Figure 52. Chaff backscatter must become larger rapidly when in the same radar resolution cell with the aircraft in order to break lock-on."

 

 

SgtPappy, your estimated make sense but by following that assumption (detector angular resolution being the main driver for whether a missile eats chaff or not), pretty much every other active radar homing missile should have much worse chaff resistance than the Phoenix because they are smaller missiles carrying smaller dishes. It's clear that at some point, the initial assumption must break down, and the simple modelling of CMs in DCS likely makes it very hard to capture these effects properly.

 

Agreed, except that other active radar missiles have much more classified ECCM and are much more modern and weren't designed during the Vietnam War and I believe that's where this breaks down. This is why my interest lies in earlier hardware because we can discuss a bit more without running into that "classified more or less forever" wall.

[Skysurfer]

Thank you for your valuable input, much appreciated! :thumbup:

[Noctrach]

@SgtPappy good points.

 

can we really conclude from what information we have today that chaff does not work against a PD radar ever looking up?

 

I feel firstly we should distinguish notching/beaming, lookup/lookdown from pure chaff effectivity.

Chaff modeling in DCS is still fundamentally RNG based, so there's always a slight chance that a missile will go for chaff instead of the target, even in a head on look-up scenario.

Notching/beaming merely pushes the balance of the diceroll to be more likely to go for the decoy.

 

Secondly, since chaff is being evaluated on the missile rather than the launching platform, a look-down on the side of the missile will make it susceptible to notching and therefore massively more likely to go for chaff, even when the STT lock is in look-up and held steadily.

This imo is the key point in this issue. Even if the launching platform never loses lock, the missile may still go for any of the "radar flares" that have been released.

Considering chaff in DCS lasts for 5-6 seconds, this means that a missile may lock onto chaff that is well outside of the scope of the STT illumination.

The SARH missiles in this game are especially sensitive to this, as they have very low chaff rejection values for some reason.

 

In my experience, I don't fly the Mirage, but no other jet I've flown will lose lock in a look-up on a beaming target. The only exception to this rule is the F-14 on a target disappearing inside the zero-doppler filter if closure drops below +-100 knots.

For missiles adhering to the old API I can absolutely confidently state they will not be notched in look-up, but this doesn't bar them from eating chaff if you get the exceptional lucky dice-roll.

[SgtPappy]

@SgtPappy good points.

 

 

 

I feel firstly we should distinguish notching/beaming, lookup/lookdown from pure chaff effectivity.

Chaff modeling in DCS is still fundamentally RNG based, so there's always a slight chance that a missile will go for chaff instead of the target, even in a head on look-up scenario.

Notching/beaming merely pushes the balance of the diceroll to be more likely to go for the decoy.

 

Secondly, since chaff is being evaluated on the missile rather than the launching platform, a look-down on the side of the missile will make it susceptible to notching and therefore massively more likely to go for chaff, even when the STT lock is in look-up and held steadily.

This imo is the key point in this issue. Even if the launching platform never loses lock, the missile may still go for any of the "radar flares" that have been released.

Considering chaff in DCS lasts for 5-6 seconds, this means that a missile may lock onto chaff that is well outside of the scope of the STT illumination.

The SARH missiles in this game are especially sensitive to this, as they have very low chaff rejection values for some reason.

 

In my experience, I don't fly the Mirage, but no other jet I've flown will lose lock in a look-up on a beaming target. The only exception to this rule is the F-14 on a target disappearing inside the zero-doppler filter if closure drops below +-100 knots.

For missiles adhering to the old API I can absolutely confidently state they will not be notched in look-up, but this doesn't bar them from eating chaff if you get the exceptional lucky dice-roll.

 

Apologies, perhaps I misremembered, but it appears you are right. I checked old tracks and found that whenever my buddy in the F-14 fired AIM-54s and AIM-7s, they were easily spoofed because he was higher than me, if even by a tiny amount. When we tested yesterday, he flew right at the deck and I could spoof them if and only if I climbed and then dove to force them into a look down state. After today's patch, the AIM-54 no longer gives a warning at all with its own radar but I guess that's a different discussion.

 

I also checked other tracks and it appears that enemies who spoofed my APG-63 had mountains at a similar altitude. What I did not realize is just how far the spoofing occurred, that is, I thought one had to be very close to the ground, say 200 ft, for this ever to work, not a few thousand feet from terrain.

 

However I am luckier than I thought then because I just tested the AIM-7s and S530 and found that I could indeed spoof them even at high altitude/look-up, however it happened a lot less than if I split-S'd towards the ground. The effect is far more pronounced for the AIM-54 where it will not at all eat chaff unless I really dive. So with the new API, it seems that the SARH missiles are still lagging behind the AIM-54 since I can never spoof the AIM-54 in a look up situation but can sometimes do so for an AIM-7 - both at very close, 3 or 4 nm range. I suppose this makes sense but I still don't know either way if chaff can be used per my previous posts .

[Noctrach]

I suppose this makes sense but I still don't know either way if chaff can be used per my previous posts .

 

I think the bottom line is, it can be used but effectiveness will be very low :) it would be a freaky instance of luck, but I've seen it happen

 

The reason it works so well against notching targets is that from a "game" perspective the missile will check every X milliseconds whether it can still see the target and whether it will go for chaff.

During a notch, the target isn't eligible as a valid result, so the only possible outcome is to go for one of the chaffs.

I feel this can still sometimes be influenced by chaff rejection, resulting in the missile finding 0 valid targets until it re-evaluates on the next tick.

 

The evaluation will still run if you're not notching, like during a lookup, but the chance of it succeeding is slim, depending on chaff rejection values.