Aim120 can be trashed with a barrel roll and chaff headon

[GRY Money]

Attached are 2 tracks and 2 tacview file that show that with correct chaff usage the Aim-120 can be barrel rolled head on with a 100% success rate. Tested in Singleplayer against AI.

This is not the infamous "AoA-Roll" from multiplayer.

Tacview-20241018-170835-DCS-1v1.zip.acmi  

Tacview-20241018-170646-DCS-1v1.zip.acmi Amram can be barrel rolled F16 pov.trk Amram can be barrel rolled F16 pov2.trk

Edited October 18, 2024 by GRY Money

[stefasaki]

This has been an issue for quite some time. A 9g loaded roll will trash a head on AMRAAM even without using chaffs. It’s simply not needed. Works best at high altitude and speed against any AMRAAM with whatever energy, it actually works better if the missile is above Mach 2, so that it will be g-limited while maneuvering.  I’ve actually been exploiting this glitch for a while, I was hoping that no one would report it it’s been a fun trick to master. 

[GRY Money]

vor 8 Minuten schrieb stefasaki:

A 9g loaded roll will trash a head on AMRAAM even without using chaffs.

What you are talking about is an AoA-roll and that only works in multiplayer. This post is not about AoA-Rolling.

Please provide a track from this update where you defeat an Aim-120 shot from NEZ headon with no chaff in singleplayer. 

Edited October 18, 2024 by GRY Money

[stefasaki]

I won’t be home for a few days but I do have a video on my phone if you can’t wait. Works perfectly even in single player, it’s just harder to pull off.

[GRY Money]

vor 7 Minuten schrieb stefasaki:

I won’t be home for a few days but I do have a video on my phone if you can’t wait. Works perfectly even in single player, it’s just harder to pull off.

It's fine if AoA-Rolling does work in Singleplayer. I just want to report this so its not treated as the "AoA-Roll" desynch issue from multiplayer where the missile actually loses track because you are teleporting slightly ingame. Here the missile misses while maintaining track the whole time. 

Possible without chaff in Singleplayer:

Tacview-20241018-182915-DCS-1v1.zip.acmiAmram can be barrel rolled without chaff F16.trk 

This track here is not an "AoA-Roll" even though some people call it that. The AoA-Roll is a different issue related to multiplayer only. 

Edited October 18, 2024 by GRY Money

[stefasaki]

I think it’s a delay in the tracking logic. They did talk about introducing a delay in tracking some time ago, likely almost a year. I bet it works since then, even though I discovered it only a few months ago. Then it would be working as intended, or they need to tweak this delay. 

[GRY Money]

Without Chaff at 10000m altitude: 

Tacview-20241018-183541-DCS-1v1.zip.acmiAmram can be barrel rolled without chaff F16 high alt.trk

[Default774]

This is already reported. Unfortunately this is old news and has been like this for years. We had some slight improvements several patches ago but I wouldn't expect anything significant to change in this area in the future, I certainly don't.

[ruxtmp]

As many have said its old news and been reported with no action and it also works in single player. I stopped playing the game altogether and have started up the old late 1990s game in its newest modded form. I check back here often hoping for improvements to missile guidance logic, ECM comms etc.

Edited October 18, 2024 by ruxtmp

[Xhonas]

Hi there @Маэстро @Chizh you're the missile guys, what can be done about this? should we expect a fix? Please check this section of the forums, there is also a bug with ECM trashing new api missiles.

Edited October 19, 2024 by Xhonas

[Wlasiuk]

How are those game breaking issues being ignored for so long already, same with the notching issue.

[DCS FIGHTER PILOT]

As someone comically put it the other day, “Who needs stealth, electronic warfare, and countermeasures?! Just roll!” 

[Маэстро]

Just roll?? BTW high-g barrel roll is the worst type of maneuver to intercept. And not in DCS only, but IRL as well.

On 10/19/2024 at 10:02 PM, Xhonas said:

Hi there @Маэстро @Chizh you're the missile guys, what can be done about this? 

Unfortunately, not much. We already readjusted amraams Kalman filter twice in last two years because of reports on forum. The "problem" here is indeed lag/delay in guidance command. But any real system have such a lag(bc filtering always introduce some lag). Minimal level of filtering/smoothing(and lag) is limited by noises(mostly by glint at short distances) and excessive reducing of smooting will lead to increased missidstance because missile will react to noise inputs and twitch. So, there is always a tradeoff between missile agility and terminal guidance accuracy.

I've made some additional changes last week that should make missile a bit more agile, but should not increase much missdistance due to noise. However, missile will stay vulnerable to high-g barrel rolls anway, just will require a higher roll rate to be defeated. Current level of filtering is already quite low and its further reducing require unrealistically low level of noises. I would like to avoid such changes.

[Xhonas]

On 10/27/2024 at 10:50 AM, Маэстро said:

Just roll?? BTW high-g barrel roll is the worst type of maneuver to intercept. And not in DCS only, but IRL as well.

Unfortunately, not much. We already readjusted amraams Kalman filter twice in last two years because of reports on forum. The "problem" here is indeed lag/delay in guidance command. But any real system have such a lag(bc filtering always introduce some lag). Minimal level of filtering/smoothing(and lag) is limited by noises(mostly by glint at short distances) and excessive reducing of smooting will lead to increased missidstance because missile will react to noise inputs and twitch. So, there is always a tradeoff between missile agility and terminal guidance accuracy.

I've made some additional changes last week that should make missile a bit more agile, but should not increase much missdistance due to noise. However, missile will stay vulnerable to high-g barrel rolls anway, just will require a higher roll rate to be defeated. Current level of filtering is already quite low and its further reducing require unrealistically low level of noises. I would like to avoid such changes.

Why other missiles such as the Aim-54 or the R27 are not affected by it? Why only the Aim-120?"

"Current level of filtering is already quite low and its further reducing require unrealistically low level of noises. I would like to avoid such changes" Wouldn't be more unrealistic to have a missile like the amraam fail to intercet the target in this scenario when older missiles have no trouble? I mean no disrespect but its hard to take it serious when you can have a high g barrel roll as part of your threat reaction. 

 

However i must say that it is good to hear that there will be some changes. Thanks for that!

 

Edited October 29, 2024 by Xhonas

[Sideburns]

11 hours ago, Xhonas said:

Why other missiles such as the Aim-54 or the R27 are not affected by it? Why only the Aim-120?"

"Current level of filtering is already quite low and its further reducing require unrealistically low level of noises. I would like to avoid such changes" Wouldn't be more unrealistic to have a missile like the amraam fail to intercet the target in this scenario when older missiles have no trouble? I mean no disrespect but its hard to take it serious when you can have a high g barrel roll as part of your threat reaction. 

However i must say that it is good to hear that there will be some changes. Thanks for that!

 

It might be because the Aim54 and R27 are still on the older missile code / behaviour, whereas the AMRAAM is effectively prototyping and testing the new missile API and code? To be honest I've lost track of what things are WIP and partially implemented, we've been waiting a while for the new missile API and code.

[Default774]

14 hours ago, Xhonas said:

Why other missiles such as the Aim-54 or the R27 are not affected by it? Why only the Aim-120?"

"Current level of filtering is already quite low and its further reducing require unrealistically low level of noises. I would like to avoid such changes" Wouldn't be more unrealistic to have a missile like the amraam fail to intercet the target in this scenario when older missiles have no trouble? I mean no disrespect but its hard to take it serious when you can have a high g barrel roll as part of your threat reaction. 

 

However i must say that it is good to hear that there will be some changes. Thanks for that!

 

 

Those older missiles are still using the old APIs with simplified flight models and guidance, not really relevant to the AIM-120.

[DCS FIGHTER PILOT]

It seems to me that this problem is the result of two major issues. The first one is fairly obvious and has been the subject of much talk in the past. The Proximity Fuze. 

It is my understanding that the current proxy fuze trigger radius of the 120's warhead in game is set to around 9m. However, according to sources linked in the discussion provided here, 

the kill radius is in the neighborhood of 15m. So if this is correct, why on earth would the trigger radius be set less than the kill radius? 

As one can see in the track I provided, had the warhead from the first missile detonated at its closet point to me (approximately 43ft or 13.1m according to Tacview) , undoubtedly I would have suffered serious damage and quite possibly lost the airframe. 

 

The second major issue contributing to this problem is one I have rarely seen brought up and impacts many other areas of gameplay besides this. That is issue of the lack of overstressing consequences for many aircraft in game. As one can see in the track, in order to evade the incoming AMRAAM, I had to execute a high G barrel roll in my F-16 pulling a whopping 10.8 g's at one point. My question is, why is my airframe the same as it was before? Would I have not at least bent it to the point where it does not handle the same anymore if not wrecked it completely? Keep in mind this maneuver is more than just a simple high G turn. Now granted, I have not done a full blown stress-strain analysis on what these types of loads would do, but my gut is telling me that the vertical stabilizer(s) would be itching to outright separate from aircraft during such a maneuver. As  @Маэстро mentioned above, yes, a high G barrel roll is one of the worst types of maneuvers to for a missile to intercept, but is it also not one of the worst maneuvers for an airframe to endure? 

Also keep in mind I had no payload while executing this maneuver. In game when people do this, it is almost always done while carrying a payload (sometimes a massive one). How is it that they just get to keep flying the same as before as if nothing had happened after executing this? At the very least, I would suspect that such maneuvers would cause payloads to simply rip off the airframe, possible damaging the airframe itself during the separation process. This is however an issue worthy of a separate post but is certainly relevant to the problem we are dealing with here. 

 

In regards to the AMRAAMs Kalman filter and guidance control algorithm(s) as modeled by ED, I would be very interested to dive deep into the mathematics of that to see if there is a more optimal intercept solution than to what we currently have in game now. However, I highly doubt I will be given that privilege.  

AOA_Roll.trk

Edited October 31, 2024 by DCS FIGHTER PILOT

[Маэстро]

On 10/29/2024 at 10:14 PM, Default774 said:

Those older missiles are still using the old APIs with simplified flight models and guidance, not really relevant to the AIM-120.

Exactly.

On 10/29/2024 at 7:57 AM, Xhonas said:

Why other missiles such as the Aim-54 or the R27 are not affected by it? Why only the Aim-120?"

"Current level of filtering is already quite low and its further reducing require unrealistically low level of noises. I would like to avoid such changes" Wouldn't be more unrealistic to have a missile like the amraam fail to intercet the target in this scenario when older missiles have no trouble? I mean no disrespect but its hard to take it serious when you can have a high g barrel roll as part of your threat reaction. 

Once R-27 is moved to the new API it will be affected in more severe way than aim-120.

On 10/31/2024 at 5:59 AM, DCS FIGHTER PILOT said:

It seems to me that this problem is the result of two major issues. The first one is fairly obvious and has been the subject of much talk in the past. The Proximity Fuze. 

It is my understanding that the current proxy fuze trigger radius of the 120's warhead in game is set to around 9m. However, according to sources linked in the discussion provided here, 

the kill radius is in the neighborhood of 15m. So if this is correct, why on earth would the trigger radius be set less than the kill radius? 

As you said if this is correct... Look, it's absolutlely unclear what they mean by kill radius. What type of target and Pk corresponds to that radius? There is AIM-54 with 60kg(!) warhead and the same 15m kill radius. Do you think aim-120 warhead (BTW which one exactly? wdu-33 or wdu-41?) can provide the same Pk at 15m distance as aim-54 one?

On 10/31/2024 at 5:59 AM, DCS FIGHTER PILOT said:

The second major issue contributing to this problem is one I have rarely seen brought up and impacts many other areas of gameplay besides this. That is issue of the lack of overstressing consequences for many aircraft in game. As one can see in the track, in order to evade the incoming AMRAAM, I had to execute a high G barrel roll in my F-16 pulling a whopping 10.8 g's at one point. My question is, why is my airframe the same as it was before? Would I have not at least bent it to the point where it does not handle the same anymore if not wrecked it completely? Keep in mind this maneuver is more than just a simple high G turn. Now granted, I have not done a full blown stress-strain analysis on what these types of loads would do, but my gut is telling me that the vertical stabilizer(s) would be itching to outright separate from aircraft during such a maneuver. As  @Маэстро mentioned above, yes, a high G barrel roll is one of the worst types of maneuvers to for a missile to intercept, but is it also not one of the worst maneuvers for an airframe to endure? 

Also keep in mind I had no payload while executing this maneuver. In game when people do this, it is almost always done while carrying a payload (sometimes a massive one). How is it that they just get to keep flying the same as before as if nothing had happened after executing this? At the very least, I would suspect that such maneuvers would cause payloads to simply rip off the airframe, possible damaging the airframe itself during the separation process. This is however an issue worthy of a separate post but is certainly relevant to the problem we are dealing with here.

Sorry, I'm not in charge of aircraft damage model. Can't say anything.

On 10/31/2024 at 5:59 AM, DCS FIGHTER PILOT said:

In regards to the AMRAAMs Kalman filter and guidance control algorithm(s) as modeled by ED, I would be very interested to dive deep into the mathematics of that to see if there is a more optimal intercept solution than to what we currently have in game now. However, I highly doubt I will be given that privilege.  

Are you sure you good at math enough? Of course I can not share our model, but there are public sources on that matter you can start from. 

Overview of optimal guidance solutions 29-01-Palumbo_Homing.pdf

Kalman filtering for missile https://secwww.jhuapl.edu/techdigest/content/techdigest/pdf/V29-N01/29-01-Palumbo_Guidance.pdf

[DCS FIGHTER PILOT]

15 hours ago, Маэстро said:

Are you sure you good at math enough? Of course I can not share our model, but there are public sources on that matter you can start from. 

 

Lets just say, I should absolutely hope so given what my graduate degree is in. 

Edited November 1, 2024 by DCS FIGHTER PILOT

[Маэстро]

7 hours ago, DCS FIGHTER PILOT said:

Lets just say, I should absolutely hope so given what my graduate degree is in. 

 

I just meant that it may be quite hard to find more optimal solution, because our implementation is based on a number of works of scientists for whom this field is of primary interest.

And it's also based on some knowledge about several real systems.

[ShadowFrost]

Wrong forum....

 

Edited November 2, 2024 by ShadowFrost

[GRY Money]

Am 27.10.2024 um 14:50 schrieb Маэстро:

And not in DCS only, but IRL as well.

I understand the barrel roll maneuver from my trackfiles is legit and not some kind of bug abuse/exploit but a feature of the 120B/C and new missile API because they have realistic computing delay for the intercept and during heavy maneuvers that error accumulates causing the high G miss just short of the target. 

Maybe the community should rethink banning people for this in multiplayer? (i didn't get banned anywhere lmao)

What is your opinion on this? 

Edited November 2, 2024 by GRY Money

[Xhonas]

56 minutes ago, GRY Money said:

Maybe the community should rethink banning people for this in multiplayer? (i didn't get banned anywhere lmao)
 

 

The community decided to ban this maneuver not because it is a legit feature of the missile, but because when you do a high G barrel roll in multiplayer you start teleporting, making you invulnerable to everything. I want to report this bug (beta testers says that there is an internal report open for this, cause of this problem: netcode desync because of link16), but i need an empty server to generate a short trackfile.

[Notarobot]

On 10/18/2024 at 6:07 PM, stefasaki said:

This has been an issue for quite some time. A 9g loaded roll will trash a head on AMRAAM even without using chaffs. It’s simply not needed. Works best at high altitude and speed against any AMRAAM with whatever energy, it actually works better if the missile is above Mach 2, so that it will be g-limited while maneuvering.  I’ve actually been exploiting this glitch for a while, I was hoping that no one would report it it’s been a fun trick to master. 

It's been reported numerous times and most multiplayer servers will ban you for it. What's your in game name by the way?

[GRY Money]

vor 8 Stunden schrieb Xhonas:

The community decided to ban this maneuver not because it is a legit feature of the missile, but because when you do a high G barrel roll in multiplayer you start teleporting, making you invulnerable to everything. I want to report this bug (beta testers says that there is an internal report open for this, cause of this problem: netcode desync because of link16), but i need an empty server to generate a short trackfile.

You can outG the missile like this in multiplayer reliably without causing lag fyi. 

Edited November 3, 2024 by GRY Money