Aim 120 boresight mode

[Viciam1]

Hi guys

 

what is the purpose of the aim 120 boresight mode instead of slave mode and under what situation should one use it

 

thank you

[skywalker22]

As far as I understand, boresight mode should work without of use FCR, and you slew the radar on the AMRAAM on the target. This way adversary wouldn't even know it has been locked (same as Fox2 missiles). This works, but works the same way also with Slave mode.

So you can turn the radar off completely, and when selecting AMRAAM missile so ASEC (Allowable Steering Error Circle) is visible on the HUD (circle appears) and if the bandit is inside of it, you can release the AMRAAM. Cannot get it to work with JHMCS, but it should I suppose.

--

Btw, boresight mode works for the Sidewinder (aim-9), where you get that diamond symbology on the hud or jhmcs (it means it slews the seeker head on the missile to that diamond). But it does not for AMRAAM aim-120, or am I missing something.

Edited July 8, 2024 by skywalker22

[Aquorys]

11 hours ago, skywalker22 said:

As far as I understand, boresight mode should work without of use FCR, and you slew the radar on the AMRAAM on the target. This way adversary wouldn't even know it has been locked (same as Fox2 missiles).

Aah... what? That didn't make any sense

11 hours ago, skywalker22 said:

But it does not for AMRAAM aim-120, or am I missing something.

Generally speaking, an AMRAAM wants information on where a target is for initial guidance, and that information is provided through a datalink. How you got the information that you relay to the AMRAAM is not necessarily important, but traditionally, it would be obtained from the firing platform's fire control radar, and that is how it works in DCS too.

You can also fire an AMRAAM without providing any target information, and in that case, it will lock onto whatever target it can find using its terminal active mode after launch. You don't have to be in boresight mode to do that as long as you have no target bugged.

[Razor18]

Some terms are mixed up it seems to me. Boresight mode is one of the ACM radar modes to quickly lock any aircraft going through the circle on top of the hud. AMRAAM boresight mode (showing "VISUAL" on the HUD) is when you launch an AMRAAM without having a locked target (radio call for that is "Maddog"). In this case AMRAAM goes active (Pitbull) immediately, and locks onto the first target it sees. This mode doesn't care if the first aircraft is friendly, so extreme caution should be excercised to avoid friendly fire, and rather never be fired in any direction, where a friendly aircraft might be in that general direction, let alone into a furball. Sorry if I misunderstood some things above...

Edited April 10, 2023 by Razor18

[GGTharos]

On 4/9/2023 at 7:47 PM, Viciam1 said:

what is the purpose of the aim 120 boresight mode instead of slave mode and under what situation should one use it

It's a dogfight mode, intended to be used when you are in a visual fight (thus the name, VISUAL) and you don't have a radar lock.   The missile is launched without target data other than your own aircraft's motion - ie. where your lift vector is pointed and how much G you're pulling - in order to initiate its own search once launched.

[Dragon1-1]

On 4/10/2023 at 10:12 AM, skywalker22 said:

As far as I understand, boresight mode should work without of use FCR, and you slew the radar on the AMRAAM on the target. This way adversary wouldn't even know it has been locked (same as Fox2 missiles). This works, but works the same way also with Slave mode.

I think that in case of the AMRAAM, Boresight is actual boresight, as in, slaved to aircraft centerline. This is very much a backup mode, for when FCR is either not an option or outright failed, for example the antenna getting stuck in some random direction. Boresight mode gets the missile to point forward so that you can aim it at the target in front of you. It's not a HOBS missile that would have its own interface to JHMCS. 

[skywalker22]

6 hours ago, Dragon1-1 said:

I think that in case of the AMRAAM, Boresight is actual boresight, as in, slaved to aircraft centerline. This is very much a backup mode, for when FCR is either not an option or outright failed, for example the antenna getting stuck in some random direction. Boresight mode gets the missile to point forward so that you can aim it at the target in front of you. It's not a HOBS missile that would have its own interface to JHMCS. 

So actually for the boresight mode, FCR is not in use, and you can only look and lock something through the seeker (I called it a radar) on the missile it self, right?

[Razor18]

No, you can't lock it. You shoot the missile, and after launch it "opens its eye" and locks the first thing it can acquire. Hence the call "Maddog".

[skywalker22]

Boresight (BORE) mode:

1. When HMCS (Helmet -Mounted Cueing System) is not powered, the missile seeker looks ahead on the aircraft bore line. This is called a mad dog shot since the missile flies ballistically out to a point without guidance, then turns on its onboard radar and locks up and flies to the first radar contact it finds. It has no IFF (Identify Friend or Foe) system, so it doesn't distinguish between a friendly or a hostile.

2. When HMCS is powered, the seeker is boresighted to the Helmet Mounted Display’s reticle. However, the missile is limited to the restrictions of the FCR’s field of view.

[Temetre]

This sounds weird. The way I understand things is(someone please correct if otherwise):

Under normal circumstances the boresight radar (dogfight mode, TMS up or so), definitely controls and locks the FCR, regardless of weapon equipped. Both Aim-120 and Aim-9x are slaved to the FCR target (after lock). 

I also dont really understand the point of just using Aim-120 for a lock before or instantly on firing. If its missile radar is used, then it creates an RWR contact anyway? If anything the FCR might be faster at locking and providing a good solution to the Aim-120? 

To me using the missile radar directly seems more like something youd do at most when the FCR is damaged.

 

Maddog just happens when you shoot the missile without a lock. But I think the missile goes active almost instantly, and Ive never heard the JHMCS can actually cue a Maddog? I mean, that could be pretty funny, like an overly expensive cheap Aim-9x. Using Aim-120s in dogfights has potential for becoming a guilty pleasure.

Edited April 13, 2023 by Temetre

[skywalker22]

I studied about guidance modes of the AMRAAM and also with conjunction with JHMCS a bit more, here it is:

In BORE mode, the missile uses its own radar to search for and track the target. The missile is launched and guided towards the general direction of the target, and the missile's onboard radar scans the area to detect the target. Once the target is acquired, the missile's guidance system directs it towards the target.

In SLAVE mode, the missile is guided by an external radar system, such as the radar on the launching aircraft or a ground-based radar system. The external radar tracks the target and sends guidance signals to the missile, which adjusts its course accordingly.

The main difference between BORE and SLAVE mode is the source of guidance information. In BORE mode, the missile uses its own radar to search for and track the target, while in SLAVE mode, the missile relies on an external radar system to guide it towards the target. BORE mode is more autonomous and can be used in situations where the launching aircraft is not able to provide guidance, while SLAVE mode provides more accurate guidance and can be used in situations where the launching aircraft has a more advanced radar system.

 

When using JHMCS with the AIM-120C missile, there are some differences between the BORE and SLAVE guidance modes.

In BORE mode, the missile uses its own radar to search for and track the target. However, when using JHMCS, the pilot can use the helmet-mounted display to cue the missile towards a specific target. The pilot can designate a target by looking at it through the helmet-mounted display, and the missile's guidance system will direct it towards the designated target.

In SLAVE mode, the missile is guided by an external radar system, such as the radar on the launching aircraft or a ground-based radar system. When using JHMCS, the pilot can use the helmet-mounted display to cue the missile towards a specific target just like in BORE mode. However, in SLAVE mode, the external radar system provides more accurate guidance signals to the missile, allowing for more precise targeting.

The main difference between BORE and SLAVE guidance modes when using JHMCS with the AIM-120C missile is the source of guidance information. In both modes, the pilot can use JHMCS to cue the missile towards a specific target, but in SLAVE mode, the external radar system provides more accurate guidance signals to the missile.

 

The AIM-120C missile's radar has a field of view (FOV) of approximately 60 degrees on either side of the missile's centerline. This means that the radar can scan an area up to 60 degrees to the left or right of the missile's nose. If a target is outside of this 60-degree, the missile may not be able to detect it using its own radar in BORE mode.

However, when the pilot is using the JHMCS, the pilot can use the helmet-mounted display to cue the missile towards a specific target, regardless of whether it is within the radar's FOV or not. The pilot can designate the target by looking at it through the helmet-mounted display, and the missile's guidance system will direct it towards the designated target.

So, while the AIM-120C missile's radar is limited to a FOV of approximately 60 degrees on either side of the missile's centerline in BORE mode, the use of JHMCS allows the pilot to cue the missile towards targets outside of this range.

Edited April 13, 2023 by skywalker22

[Temetre]

^Good stuff. Did some testing and double checked the manual after that. Possible I missed something ofc, but:

Looks like everything written above seems to check out, except using the Aim-120s radar in bore mode, which seems to be completely missing as a feature. 

 

I couldnt find a way to lock targets with the Aim-120 without using the radar. JHMCS doesnt seem to have any ability to control Aim-120s seeker head either, let alone give off-bore cues to its computer. 

[Razor18]

That's why I do have some doubts about that part tbh. I never heard about having any direct user interaction with the amraam's own radar, pre- or post launch...

[Temetre]

Hm, WIkipedia says the Aim-120D got improved off boresight features and navigation. If that JHMCS cueing feature is a thing, then maybe its just not yet on our older 120C? Could be a followup to the Aim-9X improvements, bringing its features to AMRAAMs. (meanwhile 9X is becoming a BVR missile)

edit: Also a "two way datalink" was introduced with that missile. Sounds fitting.

vor 2 Stunden schrieb Razor18:

That's why I do have some doubts about that part tbh. I never heard about having any direct user interaction with the amraam's own radar, pre- or post launch...

Its strange that its not implemented though, most weapon systems allow you to use their own sensors. Mavericks or Heatseekers. But active radar missiles they dont allow it? Especially considering radars break a lot, and the Aim-120 being potent at WVR.

If thats not a thing, maybe its a technical reason, like limited seeker life?

Edited April 13, 2023 by Temetre

[GGTharos]

Anything that's 'AIM-120D' related, or older than AIM-120C5 does not relate to our in-game AMRAAM.

 

And yes that's correct, AIM-120 radar will not be powered while it's on the aircraft.  You have to launch it and then it turns on.  Same with AIM-7.  There are some SARH missiles that are 'active on the pylon' such as the 530, but most aren't like that.

Edited April 13, 2023 by GGTharos

[Aquorys]

On 4/13/2023 at 3:01 PM, Temetre said:

I couldnt find a way to lock targets with the Aim-120 without using the radar

You don't, it just fires in terminal active mode along the boresight line (JHMCS does nothing in DCS, and this information may generally be from another block 50 variant or a newer block altogether), and then locks onto whatever it finds.

Just tested in DCS, and it does mostly what it's supposed to do. It guides to the bugged target in SLAVE, and ignores the bugged target in BORE, instead firing along the boresight line (indicated by the diamond being centered a couple degrees below the gun cross instead of tracking the bugged target in the HUD or JHMCS display), and locks onto targets after launch. Anyhow, in DCS, it can't find anything that's not pretty much directly in front of it, so I guess the missile's radar limits are somewhat off, cause the real AMRAAMs are known to have quite good off-boresight.

[Temetre]

vor 12 Stunden schrieb Aquorys:

You don't, it just fires in terminal active mode along the boresight line (JHMCS does nothing in DCS, and this information may generally be from another block 50 variant or a newer block altogether), and then locks onto whatever it finds.

Just tested in DCS, and it does mostly what it's supposed to do. It guides to the bugged target in SLAVE, and ignores the bugged target in BORE, instead firing along the boresight line (indicated by the diamond being centered a couple degrees below the gun cross instead of tracking the bugged target in the HUD or JHMCS display), and locks onto targets after launch. Anyhow, in DCS, it can't find anything that's not pretty much directly in front of it, so I guess the missile's radar limits are somewhat off, cause the real AMRAAMs are known to have quite good off-boresight.

Yeah, I think Aim-120 is supposed to have 60 degrees? Doesnt feel that way. Tbh im using the boresight so little, I dont even know if they fixed the missles locking onto other missiles yet^^

From the limited info I could find, Skywalker might well have been talking about more modern Aim-120 variants, apparently they got off-boresight features and two way datalink.

[Aquorys]

3 hours ago, Temetre said:

Yeah, I think Aim-120 is supposed to have 60 degrees?

The exact numbers are classified, so let's say, this one isn't accurate, but it's in the right ballpark.

[GGTharos]

They aren't classified, just hard to find.  A 120 isn't going to scan its entire gimbal space, that would take too long.  The scan/search patterns are mostly classified, with few details known.

[skywalker22]

21 hours ago, Temetre said:

From the limited info I could find, Skywalker might well have been talking about more modern Aim-120 variants, apparently they got off-boresight features and two way datalink.

Regarding the guidance modes, the basic principles of BORE and SLAVE guidance are the same for the AIM-120C-5, AIM-120C-6 as for the AIM-120D. In BORE mode, the missile uses its own active radar seeker to search for and track the target. In SLAVE mode, the missile can be guided by an external radar, such as the radar on the launching aircraft or a ground-based radar system.

Comparing AIM-120C-5 and AIM-9X: in BORE mode, the AIM-120C-5 uses it's active radar seeker to search for and track the target, whereas the AIM-9X uses it's infrared seeker to track the heat signature of the target. While the basic concept of BORE guidance is similar between the two missiles, the underlying guidance technology and operating principles are different.

In DCS this works just fine. In case if you not sure how to use it, check it out here:

1. BORE MODE:

 

2. SLAVE MODE:

 

I think there is an issue here, that it also works in SLAVE mode. With no FCR, AIM-120C-5 in BORE mode should only search and fire with it's seeker head, not in SLAVE. Or am I wrong?

2nd issue, FCR on off, launching AIM-120C-5 missile in BORE mode with a use of JHMCS, currently in DCS does not work either. Not even inside of 120deg (60 on each side from the bore line). Not sure if its a bug, or a work in progress.

@BIGNEWY Am I correct?

Edited April 16, 2023 by skywalker22

[Temetre]

vor 45 Minuten schrieb skywalker22:

Regarding the guidance modes, the basic principles of BORE and SLAVE guidance are the same for the AIM-120C-5, AIM-120C-6 as for the AIM-120D. In BORE mode, the missile uses its own active radar seeker to search for and track the target. In SLAVE mode, the missile can be guided by an external radar, such as the radar on the launching aircraft or a ground-based radar system.

Comparing AIM-120C-5 and AIM-9X: in BORE mode, the AIM-120C-5 uses it's active radar seeker to search for and track the target, whereas the AIM-9X uses it's infrared seeker to track the heat signature of the target. While the basic concept of BORE guidance is similar between the two missiles, the underlying guidance technology and operating principles are different.

Hm, maybe were talking about different things? I was talking about these points you listed:

 

1. The main difference between BORE and SLAVE guidance modes when using JHMCS with the AIM-120C missile is the source of guidance information. In both modes, the pilot can use JHMCS to cue the missile towards a specific target [...]

2. However, when the pilot is using the JHMCS, the pilot can use the helmet-mounted display to cue the missile towards a specific target, regardless of whether it is within the radar's FOV or not. The pilot can designate the target by looking at it through the helmet-mounted display, and the missile's guidance system will direct it towards the designated target.

 

My current understanding is: This isnt implemented in DCS, the JHMCS doesnt seem to do anything for the Aim-120 in bore mode. And in slave mode the JHMCS controls the fire radar, not the aim-120 (which is slaved to the radar). 

Ive also not really seen anything indicating the missile should be able to do that (and IIRC someone else said the same). So I wondered if youre sure that this is even in the Aim-120C version of the missile?

Edited April 15, 2023 by Temetre

[Temetre]

vor 3 Stunden schrieb Aquorys:

The exact numbers are classified, so let's say, this one isn't accurate, but it's in the right ballpark.

vor einer Stunde schrieb GGTharos:

They aren't classified, just hard to find.  A 120 isn't going to scan its entire gimbal space, that would take too long.  The scan/search patterns are mostly classified, with few details known.

Thx, makes sense!

[skywalker22]

15 hours ago, Temetre said:

Hm, maybe were talking about different things? I was talking about these points you listed:

 

1. The main difference between BORE and SLAVE guidance modes when using JHMCS with the AIM-120C missile is the source of guidance information. In both modes, the pilot can use JHMCS to cue the missile towards a specific target [...]

2. However, when the pilot is using the JHMCS, the pilot can use the helmet-mounted display to cue the missile towards a specific target, regardless of whether it is within the radar's FOV or not. The pilot can designate the target by looking at it through the helmet-mounted display, and the missile's guidance system will direct it towards the designated target.

 

My current understanding is: This isnt implemented in DCS, the JHMCS doesnt seem to do anything for the Aim-120 in bore mode. And in slave mode the JHMCS controls the fire radar, not the aim-120 (which is slaved to the radar). 

Ive also not really seen anything indicating the missile should be able to do that (and IIRC someone else said the same). So I wondered if youre sure that this is even in the Aim-120C version of the missile?

 

FCR on off, launching AIM-120C-5 missile in BORE mode with a use of JHMCS, currently in DCS does not work either. Not even inside of 120deg (60 on each side from the bore line). Not sure if its a bug, or a work in progress.

Edited April 16, 2023 by skywalker22

[Temetre]

vor 43 Minuten schrieb skywalker22:

FCR on off, launching AIM-120C-5 missile in BORE mode with a use of JHMCS, currently in DCS does not work either. Not even inside of 120deg (60 on each side from the bore line). Not sure if its a bug, or a work in progress.

Considering it doesnt seem to be mentioned in the manual, I dont think its implemented.

[Frederf]

There is no such thing as AIM-120 supported by HMCS in BORE mode. When BORE is selected the missile diamond is centered on the HUD always and the missile launches straight ahead. There is no direction of the missile via helmet like AIM-9. In slaved mode the missile is cued by radar which may be cued by helmet e.g. ACM BORE but in bore mode the missile only looks straight ahead.