R-27ER Experiment & Findings

[Capn kamikaze]

It's a WinRAR zip file you need to extract it with a zip file extractor.

 

I did that.

[OnlyforDCS]

Can a skilled flanker pilot tell me what the max range of a tail chase, co-alt, co-speed, 5km alt, non-manevuring target shot for a 27er is please?

 

Why not set up a simple mission in the editor to test just that? I don't think most people here will know the answer to that question from the top of their head. For one thing, in the online environment, most tail shots at any altitude on a co-speed target result in a wasted missile, unless the target is well within the no-escape DLZ.

[Ironhand]

....

Can a skilled flanker pilot tell me what the max range of a tail chase, co-alt, co-speed, 5km alt, non-manevuring target shot for a 27er is please?

Easy. Zero. In a tail chase, at co-speed, he'll be notching you.

[Frostie]

Not at co-altitude.

[Ironhand]

Not at co-altitude.

If that was directed at me, he will be notched in the sim. In fact, IIRC, the notch is roughly co-speed + or - 20 km/hr or so wide.

 

And, IASGATG, the answer isn't a single number. It'll change with the variables, altitude especially.

Edited March 13, 2017 by Ironhand

[DarkFire]

If that was directed at me, he will be notched in the sim. In fact, IIRC, the notch is roughly co-speed + or - 20 km/hr or so wide.

 

And, IASGATG, the answer isn't a single number. It'll change with the variables, altitude especially.

 

I'm trying to imagine what the doppler notch 'surface' would actually look like as a 3D projection. Hemispherical possibly? Hmm, probably more complicated than that.

[OnlyforDCS]

If that was directed at me, he will be notched in the sim. In fact, IIRC, the notch is roughly co-speed + or - 20 km/hr or so wide.

 

 

Really? In most tail chase situations I've been in I rarely lose the bandit. (Iinterleave/HPRF settings) Though I do fly the Mirage usually, and the radar on the M2000C might be modeled quite differently from the Flanker (No idea really) also the co-altitude in these kinds of situations is very rare. I usually try to gain altitude on the bandit as it translates to more speed at full burner.

[Ironhand]

Really? In most tail chase situations I've been in I rarely lose the bandit. (Iinterleave/HPRF settings) Though I do fly the Mirage usually, and the radar on the M2000C might be modeled quite differently from the Flanker (No idea really) also the co-altitude in these kinds of situations is very rare. I usually try to gain altitude on the bandit as it translates to more speed at full burner.

Co-speed in the described situation is zero closure rate is the notch. You usually aren't co-speed in those situations. But if you are close to it, the notch is always there to bite you. That's when you hear people screaming that something is wrong. I had him locked and he didn't put me on his 6-9 and I still lost him.

[Cik]

sukhoi at least has EOS which can usually maintain lock through the notch in tail aspect. annoying for everyone else though.

[OnlyforDCS]

Co-speed in the described situation is zero closure rate is the notch. You usually aren't co-speed in those situations. But if you are close to it, the notch is always there to bite you. That's when you hear people screaming that something is wrong. I had him locked and he didn't put me on his 6-9 and I still lost him.

 

Oh I get the physics, its just that I've rarely encountered it in a classic tail chase scenario.

[Ironhand]

Oh I get the physics, its just that I've rarely encountered it in a classic tail chase scenario.

The described scenario is admittedly artificial. :) That's how it works in the sim. Real life might be in variance.

Edited March 14, 2017 by Ironhand

[GGTharos]

It isn't the notch - it is a blind-speed that specifically affects some older radars. Because the radar code is the same for all aircraft, you don't see much differentiation (ie. these blind speeds aren't an issue for an APG-63).

 

The notch is centered around your ground speed, not zero closure :)

 

Co-speed in the described situation is zero closure rate is the notch. You usually aren't co-speed in those situations. But if you are close to it, the notch is always there to bite you. That's when you hear people screaming that something is wrong. I had him locked and he didn't put me on his 6-9 and I still lost him.

[Ironhand]

It isn't the notch - it is a blind-speed that specifically affects some older radars. Because the radar code is the same for all aircraft, you don't see much differentiation (ie. these blind speeds aren't an issue for an APG-63).

 

The notch is centered around your ground speed, not zero closure :)

That makes sense. I knew something in my thinking wasn't quite right. I knew the effect but...

[red_coreSix]

I'm not too sure but I think it had something to do with sidelobe clutter in older radars, especially the N001/N019.

[GGTharos]

No, it doesn't. It's a blind speed. With a bit more processing power you can stagger PRFs and avoid this situation. All of that IIRC.

 

Edit: Here's a better technical explanation http://www.radartutorial.eu/11.coherent/co13.en.html

[JunMcKill]

I'm not too sure but I think it had something to do with sidelobe clutter in older radars, especially the N001/N019.

 

The N001/N019 are considered older from our perspective now, but the russian already knew all about blind speed and doppler dilemma a while ago!, and it's supposed that the SU-27S/MIG-29 radar variant simulated in DCS is from late 80s or early 90s.

[red_coreSix]

Oh right, blind speeds. I confused that with the N001/019 loosing lock at low altitude when rolling beyond 120°.

[IASGATG]

Sorry I was being vague about the tail chase stuff, I was trying to lead a horse to water. Let me get into the details.

 

Whilst most of this thread is about nagivation and radar/chaff capabilties, I'm staying clear of this because a. it's not my area and b. it's a huge fix that would require the reworkings of large parts of the DCS engine.

 

I must sound like a broken record, but I'm changing the track to talk about inadequencies in the Russian missile modelling.

 

ED believes that the graph below is accurate, and state this is what they are modelling the R-27ER on in combination with a R-27ER DLZ diagram.

 

 

The problem with this chart is that DCS doesn't actually reflect it. If we take the 5km alt at 400m/s, you won't hit a target at 14km in 40s. Feel free to test any of these shots, the missile won't make it's target.

 

I've change the aerodynamic performance of the missile to achieve these shots, and the difference in missile performance is quite telling. The graph below is for a 200m/s (close enough) shot at 5km. The drop off once the missile hits the transonic region is quite stark, however this is to be expected.

 

 

I haven't compared it to the DLZ chart yet, and I'm a bit hesitant to do so as we do not know the parameters for a successful kill in their philosophy, but for completion sake I'll do it later.

 

For now, I'm just curious to hear your thoughts.

[*Rage*]

We havent always seen eye to eye before but I can recognise and appreciate the work you put into the missile dynamics. I take it you/GG and ED have different interpretations as to what the charts actually mean.

 

Here's my problem though. I dont mean it in a flippant way but I just dont see the point. Without correcting for the guidance why all the effort to increase the range? You could give the ER twice the speed and range it has now and it still would be no different than an S8 rocket. Alternately do the same for an 120B/C and it becomes twice as effective because its the only missile in DCS with guidance worth a damn. Youre effectively widening the discrepancy in missile modelling. And its already bad enough.

 

Once the gudance is fixed ill be far far more interested in what youre suggesting. Till then...:shrug:

Edited March 14, 2017 by ///Rage

[OnlyforDCS]

Why is there such a drastic difference in countermeasure rejection between the AIM120C and the ER? I understand they are completely different missiles, but isn't CM rejection modeled as basially a % dice roll in DCS regardless of whether ARH or SARH?

[*Rage*]

CM rejection is a function of speed, aspect, chaff in the seeker FOV (and maybe relative altitude IIRC) . Its very basic (eg the seeker still sees the chaff 40km away before its even turned on).

 

The ER can be 'gamed'. Its loss of guidance is too easy to predict.

 

The 120C is basically immune to all the above. This is besides all the other issues people complain about that affect the missiles.

[IASGATG]

Why is there such a drastic difference in countermeasure rejection between the AIM120C and the ER? I understand they are completely different missiles, but isn't CM rejection modeled as basially a % dice roll in DCS regardless of whether ARH or SARH?

 

My best guess is two things. One is that the modifier number for the 120C is less than the 27ER so that gives the dice roll a lower percentage. The guess is that because it's active and locks onto a chaff bundle, once that bundle despawns after about 6 seconds it can lock onto something else.

[IASGATG]

Here's my problem though. I dont mean it in a flippant way but I just dont see the point. Without correcting for the guidance why all the effort to increase the range? You could give the ER twice the speed and range it has now and it still would be no different than an S8 rocket

 

You are right. The guidance problem does such and the countermeasure problem sucks more. Fixing it will make things scarier for both sides. That being said, i still feel like this problem should be addressed first. It's an easy problem to fix as it requires no new code (well a little more code would be nice but we can fudge it for now). The navigation problem is harder because the maths has to be rewritten and coded, but shouldn't take that long to fix. Reworking the entire radar and countermeasure system requires an overhaul of every vehicle that uses a radar. This is a huge task. Right now they have fudged it by treating chaff like flares and are doing the best they can with that.

[*Rage*]

It might be easier to alter the ranges but without the guidance fix it'll make BVR combat even more unrealistic than it is now. I see the ECCM and guidance as the core issue and I dont think it's that difficult to alter the values to make the SARH missiles less miserably predictable.

Edited March 14, 2017 by ///Rage

[OnlyforDCS]

I dont think it's that difficult to alter the values to make the SARH missiles less miserably predictable.

 

Yeah, I mean if it really is a % dice roll. Why not just increase that % for the ER? That's gotta be like what, two lines of code?

 

There is something that we are missing here. has anyone tried to "mod" the guidance system code of the missiles or is that beyond modding abilities in DCS?