R-27ER Experiment & Findings

Well... This all started when I got really bored, however I think these findings should be shared, discussed and possibly have action taken to improve some aspects of the missile.

I am no missile expert and thus is why I'd like to get some input from people in the know or at least educated guesses/opinions on this matter.

I have attached 5 TacView tracks that you should have a look at to determine for yourselves if the experiment is valid. I was able to get consistent results for each.

Each experiment was conducted with an Su-27 as the launching aircraft and a drone using a Mirage M2000 on a static course deploying chaff.

Basically this shows the ineffectiveness of the R-27 and I believe to an unrealistic level. Furthermore I can only assume that the modelling of how the semi-active missiles track are incorrect, possibly on part of the radar's modelling.

Behaviour of the R-27 appears to mimic the behaviour of an active missile apart from requiring constant lock from the launching aircraft. The missile recognises all chaff and can guide to chaff that are not being illuminated by radar, chaff that are outside the radar cone. If someone can clarify this and has information on the area of radar illumination when the radar is in STT mode would be much appreciated.

In a 1v1 situation all the opposing aircraft is required to do is crank on gimbal limits at low cruise speed and chaff without any evasive manoeuvre while closing for the kill.

If someone has any history documentation on the testing of the R-27 would be awesome. I would assume the R-27 in testing would have hit chaff deploying non-manoeuvring drones with ease.

Thanks for your input.

TackView Tracks.zip

The alternative to the current modeling is basically a lot of extra work for ED and you'd get a very similar result.

Chaff is treated similarly to flares with IR seekers: As if it were an active emitter - Obviously that is incorrect behavior, but it yields the right result: You pop CMs and maneuver/position the right way, the missile misses.

A better radar/EW model overall would be great for this stuff, though - It won't help SARH AAMs get any less sucky, but lets #MakeVirtualElectronicWarfareGreatAgain!

Silly remarks in spoiler:

And in all seriousness, thank you for taking the time and effort to do this. Even if it's a bit of a dead horse on here, good on ya for going through the motions AND coming to the right conclusion about what's happening in-game! :)

EDIT: Oh, by the way, the Mirage has half the RCS of the FC3 fighters. That might play into this a bit.

Thanks for a welcome reply. RCS of the Mirage is something I did not consider nor did I know the values. I'll have a test of various other aircraft to observe any difference.

By looking at Mig29 (9.12b) manual... only problem chaff could cause to R27R is activating proximity fuse... to counter that, there is a switch for fuse setting in case of attacking targets which use chaff.

I agree with pretty much everything Sweep said. Not sure about the chaff rejection algorithms of SARH missiles within the DCS code compared to actives, but I think there was some discussion about that and it was determined that they are somewhat better in that regard.

In DCS chaffs and flares are overstated.

This has been an ongoing issue for many years.

Previous threads:

https://forums.eagle.ru/showthread.php?t=155529

https://forums.eagle.ru/showthread.php?p=2470258#post2470258

https://forums.eagle.ru/showthread.php?t=152125

https://forums.eagle.ru/showthread.php?p=2193758#post2193758

In essence. DCS modelling of chaff effectiveness is totally overpowered. Drop enough chaff and you will always defeat a SARH (R27R/ER/Aim7) missile regardless. Even if the chaff is 30km away and the missile seeker isnt active yet. Even if the chaff is way beyond radar illumination - it still registers.

Until its fixed the only useful missile in game is the Aim120B/C (good/absolute chaff rejection respectively). Hence why many servers are banning use of active missiles and allowing only semiactives/IR.

Woah. I stand corrected. :noexpression:

Really believed SARH missiles had better chaff resistance than actives in the game...

The alternative to the current modeling is basically a lot of extra work for ED and you'd get a very similar result.

 

Chaff is treated similarly to flares with IR seekers: As if it were an active emitter - Obviously that is incorrect behavior, but it yields the right result: You pop CMs and maneuver/position the right way, the missile misses.

 

A better radar/EW model overall would be great for this stuff, though - It won't help SARH AAMs get any less sucky, but lets #MakeVirtualElectronicWarfareGreatAgain!

I disagree. Proper modelling would make SARHs alot less sucky.

I challenge anyone to watch the videos I posted above and tell me thats realistic modelling. Thats what they want to see in a modern air combat simulation.

Flying along happy and dumb as long as you have chaff.

Looking at Rage's video... the R27R should be on inertial/radio correction flight till 70% of range (similar as AIM120 profile), while in video they track chaff almost after the launch... haha

I disagree. Proper modelling would make SARHs alot less sucky.

 

I challenge anyone to watch the videos I posted above and tell me thats realistic modelling. Thats what they want to see in a modern air combat simulation.

 

Flying along happy and dumb as long as you have chaff.

I feel that enhanced jamming and effects of chaff would offset that most of the time. If you fly lazily and just CM/jam your way into the threat while cranking at co-altitude, probably less sucky there.

But overall, missiles are still going to miss. And that's what counts now and when discussing future modeling.

As for the videos...Unrealistic modeling but pretty realistic results.

Also, for the videos...I don't think they demonstrate what you should be doing in the sim at all. 1v4s, all aircraft shooting, etc. - And I know some of you are probably thinking "But Sweep, that isn't the point" - You know what? It IS. How you fight affects how you defend, and if you simply fly in slow like that, and the bandits spam missiles, all of you deserve the outcome.

Aaaand one other thing that I'll note here: the Flanker really doesn't like it when the bandit beams. It goes to combined primary tracking (both sensors/radar emitting) and then if it loses that it goes to IRST primary with the IFF interrogating but no radar emission. So consider that a bit, it isn't just the ER that should be looked at for any medium aspect shots.

Looking at Rage's video... the R27R should be on inertial/radio correction flight till 70% of range (similar as AIM120 profile), while in video they track chaff almost after the launch... haha

Thought the R-27(E)R m-link range was 25km, no? As in, inside of 25km it uses the seeker?

This has been an ongoing issue for many years.

 

 

 

Previous threads:

 

https://forums.eagle.ru/showthread.php?t=155529

 

https://forums.eagle.ru/showthread.php?p=2470258#post2470258

 

https://forums.eagle.ru/showthread.php?t=152125

 

https://forums.eagle.ru/showthread.php?p=2193758#post2193758

 

In essence. DCS modelling of chaff effectiveness is totally overpowered. Drop enough chaff and you will always defeat a SARH (R27R/ER/Aim7) missile regardless. Even if the chaff is 30km away and the missile seeker isnt active yet. Even if the chaff is way beyond radar illumination - it still registers.

 

Until its fixed the only useful missile in game is the Aim120B/C (good/absolute chaff rejection respectively). Hence why many servers are banning use of active missiles and allowing only semiactives/IR.

Holy crap, didn't realise it was that bad. That can't possibly be anything remotely close to realistic.

The question is, if this has been known, then why has this problem persisted for years ? The R-27 is the main armament of the Su-27 and is kinda a game breaker especially in the online arena. Why haven't they fixed it ? If it is such a large workload to fix it at least change a few values or copy the 120 model until they can fixed it ? Any quick fix would be more practical than waiting years.

Poor Flanker pilots have been humiliated for too long... :pilotfly:

AFAIK IRL shot/hit ratio for r27 is bad anyway.

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AFAIK IRL shot/hit ratio for r27 is bad anyway.

Eh, the E-E War (the only air war where R-27s were fired in anger) doesn't really provide a good indicator of how the missile should work. Lots of questions about how the fights happened, the state of the missiles (expired, not maintained, etc. - Lot of doubts on that), and other things.

Too many questions, not enough answers.

As Rage stated, this is a very old discussion here in DCS, we have written lots of pages here in the forum, looking for a better modeling of all missiles guidance, but is futile!

I agree that the R-27R have short legs, but the guidance is not that bad, even in interviews of US pilots that flew the German MIG-29G, they remark that.

AFAIK the guy you mention said something like "It's a good missile within it's kinematic capability" or something similar when discussing the R-27R.

 

Thought the R-27(E)R m-link range was 25km, no? As in, inside of 25km it uses the seeker?

AFAIK, The monopulse seeker is the only way of guidance of both the R-27R and R-27ER, they receive the rebound radar signal all the time, and his software make the corrections during flight to intercept the target.

US RWRs already knew about the guidance frequencies and details of russian radars thanks to the information adquired from a Russian Engineer since the 70s to 1985.

https://en.wikipedia.org/wiki/Adolf_Tolkachev

Thought the R-27(E)R m-link range was 25km, no? As in, inside of 25km it uses the seeker?

The m-link max range is 25km, yes... however what kind of guidance law in terms of ratio of m-link/seeker lock is used ragarding launches under 25km, I do not have any information. Screenshot I posted from manual says 70% (for 27R1), but there is ambiguity, as it does not states the ranges.

However the section I also posted, where it talkes about engaging targets which use chaffs, there are no problems for guidance. So if you keep lock, chaff makes no difference.

However the section I also posted, where it talkes about engaging targets which use chaffs, there are no problems for guidance. So if you keep lock, chaff makes no difference.

So basically you saying if the illuminating radar doesn't get spoofed on chaff the missile should guide successfully ?

The only exception would be if chaff is between the illuminated target and the seeker right ? Unless the data link corrects that ?

So basically you saying if the illuminating radar doesn't get spoofed on chaff the missile should guide successfully ?

 

The only exception would be if chaff is between the illuminated target and the seeker right ? Unless the data link corrects that ?

Read this article about how chaff works!

http://www.globalsecurity.org/military/systems/aircraft/systems/chaff.htm

So if you keep lock, chaff makes no difference.

That is another thing where the game takes a shortcut.

Chaff affects the guiding radar IRL, too...But it doesn't in-game. It doesn't drag the centroid of track aft or anything like that.

There'a a video of F-18s doing 1v1 BFM on Youtube. The defender pops chaff and the other guy's radar/gunsight goes crazy. That's an F-18 with an APG-65 or -73 at 1km!

Arguably, the whole EW model needs overhauling.

P.S. Thanks for explaining the text in the attachment. :thumbup:

That is another thing where the game takes a shortcut.

 

Chaff affects the guiding radar IRL, too...But it doesn't in-game. It doesn't drag the centroid of track aft or anything like that.

 

There'a a video of F-18s doing 1v1 BFM on Youtube. The defender pops chaff and the other guy's radar/gunsight goes crazy. That's an F-18 with an APG-65 or -73 at 1km!

 

Arguably, the whole EW model needs overhauling.

 

P.S. Thanks for explaining the text in the attachment. :thumbup:

You're right, the radar rebound signal when chaff is deployed should affect the aircraft radar! (as is IRL, but not in DCS), and yes is an AN/APG-65

Looking at Rage's video... the R27R should be on inertial/radio correction flight till 70% of range (similar as AIM120 profile), while in video they track chaff almost after the launch... haha

From the manufacturer of the R-27ER, I found this interesting note

The missiles pursue their targets in accordance with an update proportional navigation method both in the inertial/radio-corrected flight trajectory phase and in the semi-active homing phase after locking on target en route.

http://eng.ktrv.ru/production_eng/323/503/527/

As far as I can tell and this is only IMO, ED have not modeled the inertial/radio corrected phase of the flight of the R-27ER, I believe they have only modeled the semi-active homing phase. There was also a thread a long time back where the discussion was around whether the target would be alerted by a launch warning in the inertial/radio-corrected guidance phase and in that there's an interesting point made by Soviet:

A bit of a spotty subject, and would require me reading up a little more as I do not have it memorized. As far as I remember, the radar switches to STT to authorize the launch (which is not a very correct term, the Russian radars have two modes for single target tracking one provides target telemetry for launches the second even more precise/stronger for missile guidance and painting and this is only activated after launch and runs for 60 seconds) Should the lock be lost or interrupted the missile is lost as the radar will not resume this mode until another missile is launched. Will the first missile resume guidance should second missile be launched - I do not know. There is a 10 second window where the radar will attempt to resume lock automatically based on last known target vectors and OLS information provided - it is also unclear whether during this 10 second window the missile be recovered or not.

 

The seeker is passive and is only "receiving" so it is active the moment it leaves the rail. There are no set ranges here because target's reflections could be strong enough to be acquired way in advance, giving missile better terminal guidance.

https://forums.eagle.ru/showpost.php?p=1605987&postcount=28

Anyway, ED have stated that their engineer is working on improving A2G missile dynamics at the moment. Once that's done, their engineer will work on A2A missiles. There has been no update since. So one can only hope they implement the necessary changes to all A2A missiles.

The m-link max range is 25km, yes... however what kind of guidance law in terms of ratio of m-link/seeker lock is used ragarding launches under 25km, I do not have any information.

Guidance via radio correction is used until the target is within seeker acquisition range - when the seeker locks on, the obtained target data automatically overrides the radio correction data(transmitted to the inertial navigation system by the aircraft radar).

So if you launch the missile within seeker acquisition range, switch to SARH operation occurs as soon as the seeker can acquire the lock. There is a possibility(don't know), that while the missile remains within reach of radio correction(the 25 km), it may be able to revert back to this in case seeker-lock is lost momentarily.

You're right, the radar rebound signal when chaff is deployed should affect the aircraft radar! (as is IRL, but not in DCS), and yes is an AN/APG-65

Ive seen that video and the F18s radar cone is practically being showered by chaff deployed from the F18 infront. Its not surprising that at 1km range a chaff shower will play havoc with a system designed to track and engage and reject chaff from targets up to 100km away. It really has no bearing about the discussion here.

The point is the way its been modelled for the last few years has meant that its very easy to exploit and 'game' the chaff susceptibility issue. The result is that either everyone flies the platform that can be least exploited (F15s loaded to the gills with 120Cs) or Active missiles are disallowed in the major MP servers and events.

You only have to look at the current status of DCS MP. For the last few rounds Blue Flag has run SARH only. Many 104th missions are SARH only now and it appears the next red flag events are transitioning to SARH only competitions.

Its not an ideal situation but MP hosts have to work with what theyve got.