correct as is Air to air radar is not able to detect an aircraft with a large RCS at a distance greater than 80 NM.

[Martin2487]

Since one of the previous updates (after version 2.7) there was a problem with the fact that the air to air radar is not able to detect an aircraft with a large RCS above a distance of 80 NM. Tested on IL-76, C-17, B-52, TU-95, E-3A aircraft. The usual detection distance for aircraft of this type is from 72 to 78 NM. That's pretty little. The APG-73 has a theoretical maximum target detection distance of 160 NM. For targets with such a large RCS that I tested, I would expect a target detection distance of around 100 NM. I also performed a test of the maximum detection distance on an aircraft from civil aircraft mode Airbus A-380 which has an RCS (set in the lua file) 80 m2 target detection distance again did not exceed 80 NM. All tests were performed on targets that had an HOT aspect at an altitude of about 30,000 ft, PRF MED / HI interleave, azimuth scan 20 °.

Hard to say where the mistake is. It almost looks as if the maximum target detection distance is set to some low value somewhere in the script. Although it is a different goal in terms of size RCS maximum detection distance fluctuates +/- several NM. It worked well in previous versions, I only see the bug in some update after version 2.7

Attached is a track file where the test target aircraft is represented by the C-17A.

AA radar range detection test airplane C-17.trk

[TLTeo]

It's not a bug. The APG-73 was grossly over-performing before 2.7, and is now more in line with what one would expect (at least in high PRF - it's pretty bad in medium PRF) from a radar in its class, e.g.

 

[Martin2487]

For standards with such a large RCS, it does not seem standard to me. Thanks for your work, but your test plane was a Su-27. The maximum target detection distances per fighter-type target can be +/- real. I don't want to speculate on that. Your Su-27 test aircraft had an RCS of 5.5 m2. I tested it on targets with an RCS of 80 m2. Of course thanks for your work, but my bug report doesn't criticize radar performance on fighter targets.

[TLTeo]

RCS is a single value hard-coded in DCS .lua files, no more, no less. Afaik the radars in the game all take it into account in the same consistent manner through the radar equation Harlikwin posted in that thread, so you're basically claiming that every radar in DCS is wrong. Personally, I'm very skeptical of that claim.

 

As the radar equation shows, detection range scales roughly as the fourth root of the RCS (ie, it's not as sensitive to it as you would imagine - that is why stealth aircraft need extremely low RCS to be effective for instance), meaning that if you change your RCS from 5.5 to 80 detection range will increase by a factor (80/5.5)^(1/4) = 1.95, given identical conditions otherwise. Knowing how far we can detect a Flanker, and assuming equal closure rate (which is not great - I would imagine in your case it was less than the 970 knots, reducing detection range somewhat), the detection range of your A-380 should be 48*1.95 = 93 nm for HPRF, 26*1.95 = 50.7 for MPRF. I would expect interleaved to be in between those two, which is exactly what you are finding.

 

Per the same data I posted, in previous versions, in RWS on a 20 bar scan, you would find 97*1.95 = 189nm in HPRF, 34*1.95 = 66 nm in MPRF, and somewhere in between in interleaved, which is what you're claiming should happen, more or less. Again, considering that the Hornet's radar in 2.5.6 was known to over-perform grossly, and that now it's where we would expect it to be, it is highly, highly unlikely that there is any bug for higher RCS targets.

 

If you want to test it more thoroughly, I suggest you a) get your closure up to 970 knots at the point when you detect the target and b) use HPRF only.

Edited June 15, 2021 by TLTeo

[dundun92]

7 hours ago, Martin2487 said:

theoretical maximum target detection distance of 160 NM.

No. Quite simply, the fact that the display scale goes to 160nm doesnt mean youll ever see a target that far out

[jwflowersii]

23 minutes ago, TLTeo said:

RCS is a single value hard-coded in DCS .lua files, no more, no less. Afaik the radars in the game all take it into account in the same consistent manner through the radar equation Harlikwin posted in that thread, so you're basically claiming that every radar in DCS is wrong. Personally, I'm very skeptical of that claim.

 

As the radar equation shows, detection range scales roughly as the fourth root of the RCS (ie, it's not as sensitive to it as you would imagine - that is why stealth aircraft need extremely low RCS to be effective for instance), meaning that if you change your RCS from 5.5 to 80 detection range will increase by a factor (80/5.5)^(1/4) = 1.95, given identical conditions otherwise. Knowing how far we can detect a Flanker, and assuming equal closure rate (which is not great - I would imagine in your case it was less than the 970 knots, reducing detection range somewhat), the detection range of your A-380 should be 48*1.95 = 93 nm for HPRF, 26*1.95 = 50.7 for MPRF. I would expect interleaved to be in between those two, which is exactly what you are finding.

 

Per the same data I posted, in previous versions, in RWS on a 20 bar scan, you would find 97*1.95 = 189nm in HPRF, 34*1.95 = 66 nm in MPRF, and somewhere in between in interleaved, which is what you're claiming should happen, more or less. Again, considering that the Hornet's radar in 2.5.6 was known to over-perform grossly, and that now it's where we would expect it to be, it is highly, highly unlikely that there is any bug for higher RCS targets.

 

If you want to test it more thoroughly, I suggest you a) get your closure up to 970 knots at the point when you detect the target and b) use HPRF only.

 

I've tested extensively, and the only thing I can see now that is wrong is the tracking within multiplayer.  In SP, the radar works pretty good.

[GumidekCZ]

7 hours ago, TLTeo said:

Afaik the radars in the game all take it into account in the same consistent manner through the radar equation Harlikwin posted in that thread, so you're basically claiming that every radar in DCS is wrong. Personally, I'm very skeptical of that claim.

Where did get that? You know what equation ED uses for detections? Im more than sure that this equation is not part of any script id DCS. Some much more simple one, may be somehow similar. It would very interesting, if ED could show us the equation, but I doubt that they will.

We all know that ED uses for its scan performance definitions hard limits. Thats also reason, why you cant have HITS on your scope (radar return of low intensity which cant be declared as contact). With hard limit value, you simply have radar contact or not.

[BIGNEWY]

As far as I am aware this is correct as is, I am getting a lock around 85nm, I have mentioned it to the team however. 

 

thanks

[Harker]

As far as I am aware this is correct as is, I am getting a lock around 85nm, I have mentioned it to the team however. 
 
thanks

Using the radar equation for Rmax and starting from the detection range of the Su-27 (~47-48 NM), with an RCS of 5.5 m2 in DCS, the terms other than the RCS are bundled together as a constant of ~31.

So, for the DCS Hornet, we can roughly use Rmax = 31 (RCS)^0.25.

Using that, a Tu-95MS (RCS 100 m2) should be detected at ~99 NM and the IL-78M (RCS 80m2) should be detected at ~92 NM.

In my test, I was flying at 18000 ft, while the targets were at 20000 ft. I was in RWS with HPRF, 20 degree azimuth, 1 bar scan. The targets were hot and closure speed was around 950-1000 knots. I detected both the Tu-95MS and the IL-78M at ~79 NM, meaning 20 NM and 13 NM below what I should have. Even a detection range of 85 NM is still well below the expected one.

Now, the RCS values for the two large planes might be a little old, but a max detection range of 79 NM corresponds to an RCS of 42, which is way too low for these planes.

So, either the RCS values are wrong or the radar detection matrix of the Hornet does not utilize the radar range equation.

[Harker]

Second test, I made sure I was in look-up mode. Own altitude, 10k ft, targets at 32k ft and 37k ft. Tu-95MS detected at 78 NM.

 

No difference from before.

 

Track attached.

 

2.7.1.7139 Open Beta

FA-18C_radar detection_78 NM for large RCS.trk

Edited June 15, 2021 by Harker

[GumidekCZ]

After lastest patch I measured distances a compared them with predicted range based or above mentioned equation with use of S/N number (Signal to noise ratio) gained from median (average) shorter range detections (S/N=1,064E-06).

From table bellow, you can clearly see, that from RCS=30 and more, the DCS Hornet is loosing its detection range more than is probably should have.

Latest patch with adjusted F-16 radar performance --- 5% avarege less detection range than Hornets radar --- . it have only 1nm shorter detection range (can be because of F-16 interleave PRF) for RCS=100 ... we can say, both radar with 5% det diff have both trimmed max range to same limit. And thats very weird - another sign supporting the idea of this Bug report.

(Hornet measurments done with smallest radar search area and HPRF).

Edited September 22, 2021 by GumidekCZ

[Ahmed]

Good find. There are indeed some odds things with the current modeling of radar physics, such as the findings in the look-down thread, that don't seem to follow the expected result from basic radar theory. DCS would really benefit from revisiting and improving this area.

[GumidekCZ]

@BIGNEWY please can you reopen this issue and try to find a reason from ED team, why the range for larger RCS (30sqm and larger) is not following calculations?

[Rissala]

+1

I think we have the evidence to at least investigate this again?

Edited September 26, 2021 by Rissala