correct as is HARMs not reverting to INS guidance after RADAR is turned off

[FigPucker]

In the attached track file, I launch two HARMs, targeted via the HTS, at a Tor (SA-15) that is being controlled directly by my friend. When the missiles entered the terminal portion of their attack (7-10 seconds before impact), he would turn off his RADAR.

To be clear, only one Tor turned on then off.

We performed this mission to test whether HARMs fired from the F-16 in HAD will intertially guide onto an emitter if it turns silent. Instead of flying via INS to the last known target position, as real HARMs do, we found that they simply fly off ballistically.
This is a well known and critical capability for the HARM - it's bizarre that it has been omitted and, unfortunate that it will likely go unresolved for a long time.

Bignewy or Nineline, please see what you can do about this.

Track file attached for your convenience:

 

 

server-20220404-222714.trk server-20220404-222253.trk

Edited April 4, 2022 by FigPucker

[BIGNEWY]

Hi,

the HARM hit in the general area after the emission is turned off because the INS is not as accurate and has a higher CEP. I believe this is correct as it is. 

[al531246]

1 hour ago, BIGNEWY said:

Hi,

the HARM hit in the general area after the emission is turned off because the INS is not as accurate and has a higher CEP. I believe this is correct as it is. 

If you press F6 and follow the HARM you'll notice once the emitter shuts down it flies at 1G. This indicates the HARM is not flying to a position, rather it is flying ballistically . There is no guidance being performed whatsoever upon the emitter shutting down.

This is not correct behavior. As you mentioned the INS should still guide the missile towards the last known position of the emitter. 

[FigPucker]

3 hours ago, BIGNEWY said:

Hi,

the HARM hit in the general area after the emission is turned off because the INS is not as accurate and has a higher CEP. I believe this is correct as it is. 

This cannot be the case. I have performed another two tests that allow you more time to see that the missile goes ballistic after the RADAR goes silent.
In this graph you can see that, when the RADAR is silenced, G-force drops precipitously to 1G and that turn rate flat-lines to almost 0 degrees/second, demonstrating that the HARM is ballistic and in unguided flight.

Watching the tacview file attached, you can see that both missiles are losing any guidance commands and are going ballistic within seconds of RADAR silence.
This is especially evident when you see that the missiles land up to 5nm away from the target! 

For the second test, we had the RADAR blink on and off. In this test the missile once again resumed 1G (ballistic) flight upon RADAR silence. We then turned the RADAR back on, resulting in the HARM reacquiring and pulling 18G!

 

 

This results in a DCS where IADS scripts and player-controlled SAMs render HARMs impotent.

Tacview-RADAR-Blinking.zip.acmi Tacview-RADAR_off_terminal_atk.zip.acmi server-20220404-222714.trk server-20220404-222253.trk

[BIGNEWY]

I will run it by the weapons Devs 

[BIGNEWY]

I have just had an answer from the team it is working as intended, the INS is a very simple one, using dead reckoning and the CEP for accuracy is larger. 

[FigPucker]

An INS that uses dead reckoning would use dead reckoning to navigate to the last known target position, not one 5nm away. As you can see on the graphs, the missile's guidance simply diminishes to nothing after the RADAR is lost, and the missile flies off ballistically. Yuu can see this by the fact that missile goes to 1G and nil turn rate.

With a simple INS, the missile would not go ballistic and would have a dynamic G-load and turn rate.

Please have your weapons devs review the updated track files that better demonstrate this problem.

[FigPucker]

In this track you can see the harm flies 16nm away from the target when the RADAR is shut down.
You can see that the HARM flies ballistically and makes no attempt to navigate intertially to the last known target position.

 

server-20220404-221823.trk Tacview-20220405-012834-DCS.zip.acmi

[FigPucker]

Thanks Al.

The HARM does indeed use an INS - though the exact mechanism and CEP of said inertial guidance remains classified.

ED Team -
I have demonstrated the INS in action by firing a HARM in EOM mode.

In EOM mode, the HARM uses inertial guidance to fly towards the designated steerpoint and search for the specified emitter. If the emitter is silent, as it was in this test, it will use inertial guidance to fly to the designated steerpoint. In this case the steerpoint was placed on the same location as the silent Tor. You can see that both HARMS landed within a few hundred meters of the target after having flown ~25nm, a CEP of ~200 metres and not 5-16nm!

I have attached a graph of this EOM shot. Unlike the shots where the HARM loses guidance, you can observe that the missile is being maneuvered by its inertial guidance system.

 

To be clear, the bug that needs to be addressed is that the missile, when fired upon a target that goes silent midflight, fails to switch to inertial guidance.

It is perplexing that this bug report has required such exhaustive evidence and explanation, when the physics and missile behaviour obviously demonstrate that this is not working properly. I would appreciate if Wags could take a look at this and have it addressed.

 

server-20220405-144905.trk Tacview-20220405-145014-DCS-base attack_one sam.zip.acmi

Edited April 5, 2022 by FigPucker
Attached track and tacview

[Frederf]

What about the specific glide behavior to increase loiter time for reacquire or flex logic? A loss of track HARM should neither go ballistic nor resume destination travel unless the TI/GS setting inhibits these features.

[SullyFUBAR]

Is this topic back on the table now that the thread has been unlocked? 

[84-Simba]

Has anything been worked on with this bug already ?

Thanks.

[Aries144]

Something's not right here. The purpose of the Standard ARM and HARM were to provide anti radiation missiles that continued homing on the stored location of a radar emitter if it stopped emitting. HARM used to do that in DCS, now it doesn't.

[al531246]

Shame I missed the 1 year anniversary of this bug report. Hopefully I'll make it for the 2 year anniversary. See y'all on April 4th next year!

But seriously come on ED. Whoever marked this as 'Correct as is' needs to be made redundant. 

Edited June 29, 2023 by al531246

[Hobel]

vor 24 Minuten schrieb al531246:

Shame I missed the 1 year anniversary of this bug report. Hopefully I'll make it for the 2 year anniversary. See y'all on April 4th next year!

But seriously come on ED. Whoever marked this as 'Correct as is' needs to be made redundant. 

 

Would it be possible to create a new short track that shows the behavior? 

[Hobel]

Am 29.6.2023 um 18:04 schrieb al531246:

Shame I missed the 1 year anniversary of this bug report. Hopefully I'll make it for the 2 year anniversary. See y'all on April 4th next year!

But seriously come on ED. Whoever marked this as 'Correct as is' needs to be made redundant. 

 

Again,new track pls?

Edited September 15, 2023 by Hobel

[VKing]

On 9/15/2023 at 8:11 AM, Hobel said:

Again,new track pls?

 

Here's a track showing that the underlying issue still exists in MT 2.8.8.43704.

 

[Hobel]

vor 27 Minuten schrieb VKing:

Here's a track showing that the underlying issue still exists in MT 2.8.8.43704.

 

I look at 

[Hobel]

vor 5 Stunden schrieb VKing:

Here's a track showing that the underlying issue still exists in MT 2.8.8.43704.

 

so in your link it's about the AGM-88 going active too early, in the topic here it's about INS`?

[VKing]

11 hours ago, Hobel said:

so in your link it's about the AGM-88 going active too early, in the topic here it's about INS`?

I believe the problem in this thread is an expression of the bug that causes the HARMs to go active before they are in their terminal phase.
If the HARM does no go active before the terminal dive, you won't get HARMs that miss by the width of the map if the radar turns back off again.

Edited September 22, 2023 by VKing

[Hobel]

So as far as the INS aspect is concerned, I would say that is there.

You can see in the video how I turn off the radar of the Sa-15 immediately after the AGM-88 goes active and turns off, but the AGM-88 continues to turn to the HDG from which the signal came and flies towards it , even though the radar is off.


 

 

Edited September 28, 2023 by Hobel