AIM-120 and R-27 homing

[TAW_Blaze]

All his mod does is change one probability variable for countermeasures on the 3/9 line.

 

 

At current, countermeasures are more effective on the 3/9 line and less effective fore/aft.

 

His mod keeps the probability for the fore/aft the same, but makes the 3/9 line significantly less likely than a fore/aft shot.

 

Basically it makes chaffing on the notch close to pointless.

 

That sounds like some nice anti-realism. :D

 

@Ragnarok: don't take this the wrong way, I just meant it as a harmless joke.

[Breakshot]

All his mod does is change one probability variable for countermeasures on the 3/9 line.

 

 

At current, countermeasures are more effective on the 3/9 line and less effective fore/aft.

 

His mod keeps the probability for the fore/aft the same, but makes the 3/9 line significantly less likely than a fore/aft shot.

 

Basically it makes chaffing on the notch close to pointless.

 

Good, so whats needed is the exact opposite, the notch should be effective, whilst less chance of a dud on frontal and lookup aspects. Perhaps Ragnarok can shed light on his reasoning for those values?

[TAW_Blaze]

Good, so whats needed is the exact opposite, the notch should be effective, whilst less chance of a dud on frontal and lookup aspects. Perhaps Ragnarok can shed light on his reasoning for those values?

 

Yep, but maybe it's only possible to tweak the notch multiplier? I don't know, I'm in the dark with modding in DCS.

[*Rage*]

....in a look up situation. Thats what the mod changed IRC. Notching while at lower altitude/ground clutter still worked.

Edited June 15, 2017 by ///Rage

[Breakshot]

....in a look up situation. Thats what the mod changed IRC. Notching while at lower altitude/ground clutter still worked.

I suspect the .Lua files are extremely limited in their tweak parameters.

 

Is there even a "lookup" value?

 

Perhaps someone with knowledge can explain the current setup and compare say Aim 120 vs ER values. We all know the effective difference in Sim.

 

Clearly the 120 never bites on chaff unless notched, even then it reacquires pretty well. ER bites on chaff in all circumstances heavily. What SARH missiles need is perhaps to be worse in lookdown, notch situation, but at least reliable enough in optimal conditions.

 

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[*Rage*]

Well Wags said that the engineer would start improving the A-A systems after he finished reworking/making A-G guidance. So maybe after the hornet, since it is introducing a lot of A-G weapons. Or maybe if Heatblurs AIM-54 modeling is done well enough ED might let them help with other missiles.

 

The Hornet is at least a year away (in my estimatiion). Probably far longer till full release. I also doubt ED would let HB do their missile work for them. So far 3rd party modules have made their own missiles.

 

An interim fix is needed. This issue wont go away otherwise.

[wilky510]

The Hornet is at least a year away (in my estimatiion). Probably far longer till full release.

Don't say that :(

[FLANKERATOR]

I've noticed this interesting behavior of AIM-120 the other day: As I flanked it and pumped chaff out, it was kind of switching between chaff and my Su-27. It had sort of "here is chaff, here is the plane, here is another chaff, oh here is the plane again" behavior, as it was trying to stay on my Su-27 but kept getting interrupted by addition of the chaff only to turn back towards me after the chaff dispersed.

 

I was just wondering: does AIM-120 (in active homing mode) have any sort of search pattern movement by it's antenna after loosing the original lock on the target, or does it just go back to it's neutral position and wait for some other target (chaff/airplane) to get into it's radar cone?

 

This brings me to R-27: shouldn't the R-27 do the same when faced with chaff? The only difference here is the source of radiation, right? Or am I missing something?

 

Cheers.

 

What I personnaly noticed is that switching PRF post launch and adjusting it to targets aspect dramatically improves r27s guidance.

I feel like flankers radar in dcs is stuck on whatever PRF you had before launching and does not adjust automatically post launch so when targets aspect shifts because of evasive manoeuvres, it tends to break the m link although your radar may still show a lock. The radar/EOS dual tracking seems to also play a role here.

 

Adjust PRF mid-flight accordingly and you ll notice the r27 will start reacquiring like the 120.

[Svend_Dellepude]

What I personnaly noticed is that switching PRF post launch and adjusting it to targets aspect dramatically improves r27s guidance.

I feel like flankers radar in dcs is stuck on whatever PRF you had before launching and does not adjust automatically post launch so when targets aspect shifts because of evasive manoeuvres, it tends to break the m link although your radar may still show a lock. The radar/EOS dual tracking seems to also play a role here.

 

Adjust PRF mid-flight accordingly and you ll notice the r27 will start reacquiring like the 120.

 

Maybe there is something about this in the Flanker, I don't know.

I've been fiddling with the PRF thing a lot in the Eagle but in the end i couldnt make anything out of it.

In some situations it seemed like it made a difference, but 5 mins later in a similar situation it made no difference at all.

Never really could make anything conclusive out of it.

[*Rage*]

We switch to MED PRF by default within 20km. Tracking is still terrible...

[TAW_Blaze]

We switch to MED PRF by default within 20km. Tracking is still terrible...

 

I think he meant that after launch you stay in HPRF and only use MPRF if the target is getting near the beam or cold. Could be an interesting theory to test..

[*Rage*]

We tried it. MPRF works ever so slightly better.

[Breakshot]

We tried it. MPRF works ever so slightly better.

That is correct, any half competent Flanker pilot would know to do this under 25km. This certainly isn't why ERs love chaff...

 

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[Ironhand]

That is correct, any half competent Flanker pilot would know to do this under 25km. This certainly isn't why ERs love chaff...

 

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:) Paint me incompetent, then. It's something I never do because I've never been able to measure any reliable difference based on PRF nor seen any data indicating that we actually control the PRF after launch.

[Frostie]

:) Paint me incompetent, then. It's something I never do because I've never been able to measure any reliable difference based on PRF nor seen any data indicating that we actually control the PRF after launch.

 

Imagine being in Hi PRF and seeing a contact low at 20km turn to try and notch he will disappear of scope until you switch to Medium, if you repeat the situation but lock the contact up, when he turns cold you will lose lock and your system will switch to EOS lock. To alleviate this during lock you switch to Medium PRF. There is no indication to tell you this but it does work but it requires you to remember the sequence of PRFs, ILV-Hi-Med. A tip is to reset PRF to set you back to ILV so you can work the sequence.

 

It is a quirk of the sim as I believe the radar set locked onto a target should automatically set PRF and know whether the target is look down or look up.

Edited June 16, 2017 by Frostie

[Svend_Dellepude]

Does anybody have a track or tacview that conclusive shows that is has an effect changing PRF with a locked target?

[Breakshot]

:) Paint me incompetent, then. It's something I never do because I've never been able to measure any reliable difference based on PRF nor seen any data indicating that we actually control the PRF after launch.

 

Glad to be of help! :thumbup:

[Breakshot]

Does anybody have a track or tacview that conclusive shows that is has an effect changing PRF with a locked target?

 

Easy to test on your own...

 

Guys lets keep the topic on point of SARH missile tracking!

[Ironhand]

Imagine being in Hi PRF and seeing a contact low at 20km turn to try and notch he will disappear of scope until you switch to Medium, if you repeat the situation but lock the contact up, when he turns cold you will lose lock and your system will switch to EOS lock. To alleviate this during lock you switch to Medium PRF. There is no indication to tell you this but it does work but it requires you to remember the sequence of PRFs, ILV-Hi-Med. A tip is to reset PRF to set you back to ILV so you can work the sequence.

 

It is a quirk of the sim as I believe the radar set locked onto a target should automatically set PRF and know whether the target is look down or look up.

I understand concept well enough. I just haven't seen any data that conclusively demonstrates the effectiveness, that's all. Usually the "proof" is anecdotal or the test has a small sample size and few, if any, controls.

 

I mention the last bit because I remember testing (many, many, many moons ago) the pK of one of this sim's precursor's R-73s. The first 4 out of 5 hit their target. If I had stopped there, I would have concluded that the pK was 80%. But, as it turned out, after 100 trials, those were the only hits out of 100 trials. They just happened to occur right at the beginning. So the pK was actually only 4%. That's why I feel that sample size matters.

[GGTharos]

The effect, IK, is that the radar won't drop a contact that's gone cold.

 

This is a bit strange in and of itself - lock shouldn't drop at ranges shorter than the missile's Rmax at that altitude. The reason I'm saying this is that missile guidance should/would suffer, maybe even become useless if HPRF is not maintained. That's just a general rule of thumb for SARH AAMs of the time. So, the radar would always try to automatically maintain HSTT. Perhaps this is part of where the Radar/EO automation comes in at in RL as well, I don't know.

Anyway, PRF isn't something the missile itself is sensitive to in-game. It's the launching radar - thus PK increases why switching to MPRF because the launching radar wont' drop the contact.

[Breakshot]

I understand concept well enough. I just haven't seen any data that conclusively demonstrates the effectiveness, that's all. Usually the "proof" is anecdotal or the test has a small sample size and few, if any, controls.

 

 

This is a test that doesn't need any sample size, just lock something up, then let it maneuver into the notch, watch the RAD STT lock switch to EOS/IFF.

 

Repeat the same thing this time preemptively switching to MED PRF right after STT is established and watch the lock maintain a stable STT all the way (assuming target is within 25km).

 

I dont think we need to discuss the impact of this on SARH tracking as lost STT lock usually means, lost missile...

 

 

EDIT: GG pretty much explained it above ^^

Edited June 16, 2017 by Breakshot

[Ironhand]

This is a test that doesn't need any sample size, just lock something up, then let it maneuver into the notch, watch the RAD STT lock switch to EOS/IFF.

 

Repeat the same thing this time preemptively switching to MED PRF right after STT is established and watch the lock maintain a stable STT all the way (assuming target is within 25km).

 

I dont think we need to discuss the impact of this on SARH tracking as lost STT lock usually means, lost missile...

 

 

EDIT: GG pretty much explained it above ^^

I'll try that at my earliest opportunity. :)

[FLANKERATOR]

I think he meant that after launch you stay in HPRF and only use MPRF if the target is getting near the beam or cold. Could be an interesting theory to test..

 

Exactly. Although HI mode has the longest reach compared to other modes, PRF here is linked to aspect of the target not range.

 

I'll try to replicate and post again but from my experience, HI is best head on only. As soon as aspect starts building up, I usually switch to ILV and when angle off kicks past 90 deg, MED usually does a better job at tracking.

 

As Frostie said, there is no PRF indication in STT mode so keeping track of the cycle in your head is crucial (talking about pilot task load in the Flanker).

 

I will try to come up with a demo once back from holiday but countless times I noticed on Tacview how an R27 gone ballistic swings back on track after you adjust PRF.

 

I'm not claiming chaff related issues don't exist but I'm fairly certain tweaking PRF mid flight helps R27s significantly. It's not easy though to cycle it in your head under pressure while notching, dispensing CMs etc, it easy to mess up and lose track of it in the heat of the action.

[*Rage*]

As already mentiloned IN GAME missile tracking is not sensitive to PRF setting. It makes no difference. Only that you are less likely to lose STT lock in MPRF at closer ranges when the bandit starts maneuvering. Hence why it makes a marginal difference.

[FLANKERATOR]

If adjusting PRF helps with maintaining lock when aspect changes, it will affect guidance of the semi active, believe it or not. Maintaining lock and missile guidance go hand in hand.