Possibility that the RCS of R-77 is abnormally large.

[Admiral_ZIPANGU]

This is a substitute for a report given to me by a friend of mine, and was translated from Japanese using a translation tool, so please forgive me if there are inappropriate parts in the text. The report is as follows.

 

The R-77's RCS is probably too large in the current version, causing the AIM-120 and SD-10 to bite the R-77.

This phenomenon occurs with high probability when the intermediate guidance is cut off or interrupted in the middle. This phenomenon does not occur when the intermediate guidance is performed to the end or when the guidance is performed to PITBULL.

All of the Track file and Tacview file shown here were made when the intermediate induction was cut off in the middle of STT (except for "R-77_JF-17_2" below).

There is a possibility that SD-10 of JF-17 will bite even if it is guided to PITBULL (see "R-77_JF-17_2").

See below for a description of R-77's RCS

DCS World OpenBeta\Scripts\Database\Weapons\missiles_data.lua

Name = P_77, --R-77

Reflection = 0.15,

For reference, R-27ER's RCS is described as "Reflection = 0.08,".

R-77_JF-17.acmi R-77_JF-17.trk R-77_JF-17_2.acmi R-77_JF-17_2.trk R-77_F-15.acmi R-77_F-15.trk R-77_FA-18.acmi R-77_FA-18.trk

[GGTharos]

The problem isn't the RCS, the problem is that generally missiles in DCS aren't loaded with (and therefore never use) a range/angle/doppler gate.   The R-77's grid fins are likely to present an interesting RCS.

Edited February 4, 2021 by GGTharos

[Admiral_ZIPANGU]

38 minutes ago, GGTharos said:

The problem isn't the RCS, the problem is that generally missiles in DCS aren't loaded with (and therefore never use) a range/angle/doppler gate.   The R-77's grid fins are likely to present an interesting RCS.

 

Your point is probably correct, the R-77's distinctive fins can certainly produce some interesting RCS values. It is also true that the missile guidance logic of the DCS is still in its infancy. However, the current situation of AIM-120 being guided by R-77 is clearly an anomaly and should be corrected.
To add to the earlier report, my friend, the first reporter, testified that he set the Reflection of R-77 to 0.05, and this phenomenon was no longer seen. Changing the RCS value of the R-77 as a temporary measure could be very useful.
 

[GGTharos]

That's fair.

[Bankler]

I just came across this, so I'll add my experience.

 

Setup:

Client Viper or Hornet with AIM-120C

Enemy AI MiG-29 with one R-77

 

Repro:

1) Fly straight towards the enemy

2) Lock him up in STT

3) When he fires his R-77, fire an AIM-120C

4) Defend (Crank left then crank right) keeping the STT lock

5) The AIM-120 will suddenly change target and go for the R-77 missile

 

Reproducability:

Around 60%+ (!)

 

Remarks:

1) While it sounds plausible (maybe...) that a missile could hit another missile in rare occasions, it doesn't seem reasonable that it would happen this easily. Especially when constantly keeping a STT lock.

 

2) Reproducable with both Viper and Hornet. So the bug seems aircraft independent.

 

Suggestion:

If it's not easy to tweak this to behave in a reasonably way (which I'd understand), I suggest you just disable this feature completely for now. Perhaps by setting all A/A missiles' RCS to 0 or something. The few/rare/non-existing(?) cases of false negatives would be much better than having any false positives.

 

Three trks attached. 2 with Viper and 1 with Hornet.

 

AmraamVsMissile_3.trk AmraamVsMissile_1.trk AmraamVsMissile_2.trk

AmraamVsMissileBug.miz

Edited March 4, 2021 by Bankler
Added miz

[nighthawk2174]

The issue here may be less the RCS of the adder, which in all probability would be abnormally high for a missile due to the gridfins, but how active missiles work in DCS.  I very much doubt they should be grabbing locks here on each other.  Not only is it likely that in the above cases the other missile was outside each others FOV but why would it grab onto a target nowhere near the predicted intercept point?  Especially for the amraam; not only does it not make much sense for it to grab onto a target nowhere near the predicted intercept point.  But while it is getting datalink updates it should, according to real pilots, dump all other targets and guide on what the radar is locking even if the target is in the notch and even if there are multiple targets close to each other.

[GGTharos]

There is a range and doppler gate which a missile cannot fall into unless it's just being launched.  The only possibility for matching these parameters is if the missile searches for its target, finds nothing, loses all other sources of information will then throw most gates open ... I have some doubts about throwing the range gate so wide open that it would capture a missile unless it was still quite early in the launch.

Edited March 5, 2021 by GGTharos

[dorianR666]

yeah but missiles in DCS dont have any gates. its not implemented. this bug is probably result of that limited simulation.

 

some planes in DCS dont have range gates either. you can see hornet's STT sometimes switching to another target far away when the current one is lost for a second, if they are in line.

[GGTharos]

I wasn't implying that there are any in DCS.  There was discussion revolving around what the missiles should be doing.

Edited March 6, 2021 by GGTharos

[dorianR666]

im not implying you implied that, im just adding more information.

[GGTharos]

I'm not implying you're not adding more info-ok I'll stop here