The Mistral missile for the Gazelle has a large number of inaccuracies. Here is my work (with sources) to make it more realistic. I post it here rather than in the Gazelle section, because ED is now in charge of weapons

[Mad_Shell]

Hi there. The Mistral missile suffers from several issues and inaccuracies, making it severely underperform. Here is my work, using solid sources, to correct the missile.  
Note that DCS uses the Mistral located in "./CoreMods/aircraft/SA342/SA342_Weapons.lua" (by Polychop) which is encrypted. So I used and modified the Mistral located in "./CoreMods/aircraft/AircraftWeaponPack/AA_Missiles.lua" (by ED, and with only a few different values compared to Polychop's Mistral) to make my new Mistral version. 

Here are all the changes I propose, and the sources I've used:

- the seeker field of view used in DCS is  14°. That is a ridiculous value. It's 7 times what is used for the stinger or the Igla (2°). Since a larger field of view means that flares stay longer in the field of view of the missile, that also gives an atrocious resistance to flares to the Mistral. That also leads to situations where the Mistral will switch to another aircraft while it's quite far from the intended target... In real life, the Mistral is described as having a very narrow field of view, combined with advanced algorithms, giving it an excellent resistance to flares (Janes Land Based Air Defenses 1992-1993; SAFRAN document on Mistral seeker). I recommend a value of 1°, given the Mistral is described as having a better seeker than the Stinger and Igla in "ANALISIS DEL MISIL MISTRAL INFRARROJO COMO SISTEMA ANTIMISIL Y ANTIAEREO", and the best kill probability of all MANPADS in "MANPADS A Terrorist Threat to Civilian Aviation?" (page 39).

- the proximity fuse has a radius of 5 meters in DCS. The document "ANALISIS DEL MISIL MISTRAL INFRARROJO COMO SISTEMA ANTIMISIL Y ANTIAEREO" cites a proximity fuse radius of 2 meters, more plausible for a missile with a 3kg warhead.

- the value of K = 2 used in DCS in the autopilot part, is too low. For a short range missile, many articles explain that a value of K between 3 and 5 gives better results (see the attached article "Proportionnal Navigation Guidance"). The AMRAAM in its terminal phase uses K = 4 in DCS. Based on my tests, a value of 5 gives the best results for the Mistral (https://cdn.discordapp.com/attachments/925038843399376917/955940311354454056/K_effect.mp4 ). And I know it's not definitive and documented proof, but one would wonder why MBDA would not give the better guidance to its missile...

- the flag_dist  = 150 parameter is too high. It leads to the missile brutally diverging from its target if the target is flanking (see example K = 2 in the video). A value of 50, like the one used for the Igla, combined with K = 5, gives the best hit probability (see example K = 5 in the video).

- the GimbLim parameter has a value of 30°. I propose a value of 38°, based on "Janes Land Based Air Defenses 1992-1993", which cites a gimbal limit of 38° for the Mistral 1, and the SAFRAN Mistral missile seeker document citing a >30° gimbal limit.

- for omega_max, which is the maximum angular tracking rate of the seeker, I propose a value of 20°/second, as stated in the SAFRAN document about the seeker.

- The rocket burn time should be about 2 seconds, rather than 3, based on video evidence ((https://youtu.be/KK9_Iq0AM9k?t=15 ; https://youtu.be/RY78aBlUkMQ?t=27 ).

- I add that the missile should self destruct after 14 seconds of flight time (fuse confirmed to self-destruct in the document "poste de tir Mistral", and 14 seconds max flight time cited in "ANALISIS DEL MISIL MISTRAL INFRARROJO COMO SISTEMA ANTIMISIL Y ANTIAEREO".

- As a bonus, it would be great to see tha shaped trajectory added. The Mistral is designed to have a shaped trajectory (it climbs a bit just after launch, see photo attached). This is especially important to engage enemy helicopters, as it allows the missile to continue to track them even if they try to terrain mask.

You'll find attached a lua file, which is the ED's Mistral file with all the parameters corrected with the values I propose. Some things I haven't included in the lua are the self-destruction at 14 seconds, and modifying the "SeekerSensivityDistance" and "sensitivity" parameters to match a 3.5 times better sensitivity than the Magic 2 missile seeker (according to Janes Land Based Air Defenses 1992-1993. That's for the Mistral 1, but the Mistral 2 we have in DCS basically has the same seeker.)

SAFRAN_Mistral_Seeker.pdf ANALISIS DEL MISIL MISTRAL INFRARROJO COMO SISTEMA ANTIMISIL Y ANTIAEREO.pdf Proportional_Navigation_Guidance.pdf New_mistral.lua

Edited December 20, 2022 by Mad_Shell
link to video, photo added, shorter title

[Flappie]

Fantastic job, @Mad_Shell! Thank you very much. I want to report this, but one of the document you're refering to is missing, "poste de tir Mistral". Can you add it in, please? (as you know, only public documents are authorized).

[Flappie]

Furthermore, which values do you suggest for "SeekerSensivityDistance" and "sensitivity"  and why? (sources)

[Mad_Shell]

On 12/25/2022 at 7:35 PM, Flappie said:

Furthermore, which values do you suggest for "SeekerSensivityDistance" and "sensitivity"  and why? (sources)

Oops, I forgot a doc yes, here it is! It is written:

"Une fusée de proximité qui a pour but de donner l’ordre de mise à feu de la charge militaire soit à l’impact, en détection de cible à proximité, soit en autodestruction."

Translated: 

"A proximity fuse meant to trigger the warhead, at impact, or if a target is detected at proximity, or for self-destruction"

For the parameters "SeekerSensivityDistance" and "sensitivity", hard to propose a value without knowing what they do exactly. All I know is that in "Janes Land Based Air Defenses 1992-1993" (I posted screenshots of the relevant pages in my 1st post), it is stated that the Mistral should be able to lock on a non afterburning jet at at least 6km, and on a combat helicopter with heat reduction systems (IR suppressors) at 4km. It is also written that the Mistral seeker is 3.5 times more sensitive than the Magic II seeker. In the Magic II lua file, the value used is SeekerSensivityDistance = 20000 (vs 10000 in th Mistral lua). There is no "sensitivity" parameter in the Magic II lua since it doesn't use the more modern api with a modelled seeker).

Last time I tested the Mistral the lock distance seemed quite close to what is specified in "Janes Land Based Air Defenses 1992-1993", so I suspect that it's more the Magic II seeker beeing too sensitive in DCS.

Poste_de_tir_Mistral.pdf

[AeriaGloria]

On 12/26/2022 at 1:48 PM, Mad_Shell said:

Oops, I forgot a doc yes, here it is! It is written:

"Une fusée de proximité qui a pour but de donner l’ordre de mise à feu de la charge militaire soit à l’impact, en détection de cible à proximité, soit en autodestruction."

Translated: 

"A proximity fuse meant to trigger the warhead, at impact, or if a target is detected at proximity, or for self-destruction"

For the parameters "SeekerSensivityDistance" and "sensitivity", hard to propose a value without knowing what they do exactly. All I know is that in "Janes Land Based Air Defenses 1992-1993" (I posted screenshots of the relevant pages in my 1st post), it is stated that the Mistral should be able to lock on a non afterburning jet at at least 6km, and on a combat helicopter with heat reduction systems (IR suppressors) at 4km. It is also written that the Mistral seeker is 3.5 times more sensitive than the Magic II seeker. In the Magic II lua file, the value used is SeekerSensivityDistance = 20000 (vs 10000 in th Mistral lua). There is no "sensitivity" parameter in the Magic II lua since it doesn't use the more modern api with a modelled seeker).

Last time I tested the Mistral the lock distance seemed quite close to what is specified in "Janes Land Based Air Defenses 1992-1993", so I suspect that it's more the Magic II seeker beeing too sensitive in DCS.

Poste_de_tir_Mistral.pdf 1.99 MB · 2 downloads

10000 seeker sensitivity means a non afterburning Su-27 will be locked on at 10 km. 10000 is what most missiles in this category use. 
 

My heat supressed Mi-24/8 with IR coefficient of 0.5, would be locked on at 5 km. Gazelle/Apache/Huey would only be locked at 2 km. So 10000 or a little higher is likely the correct ball park 

[Маэстро]

On 12/21/2022 at 2:08 AM, Mad_Shell said:

Hi there. The Mistral missile suffers from several issues and inaccuracies, making it severely underperform. Here is my work, using solid sources, to correct the missile.  
Note that DCS uses the Mistral located in "./CoreMods/aircraft/SA342/SA342_Weapons.lua" (by Polychop) which is encrypted. So I used and modified the Mistral located in "./CoreMods/aircraft/AircraftWeaponPack/AA_Missiles.lua" (by ED, and with only a few different values compared to Polychop's Mistral) to make my new Mistral version. 

Here are all the changes I propose, and the sources I've used:

- the seeker field of view used in DCS is  14°. That is a ridiculous value. It's 7 times what is used for the stinger or the Igla (2°). Since a larger field of view means that flares stay longer in the field of view of the missile, that also gives an atrocious resistance to flares to the Mistral. That also leads to situations where the Mistral will switch to another aircraft while it's quite far from the intended target... In real life, the Mistral is described as having a very narrow field of view, combined with advanced algorithms, giving it an excellent resistance to flares (Janes Land Based Air Defenses 1992-1993; SAFRAN document on Mistral seeker). I recommend a value of 1°, given the Mistral is described as having a better seeker than the Stinger and Igla in "ANALISIS DEL MISIL MISTRAL INFRARROJO COMO SISTEMA ANTIMISIL Y ANTIAEREO", and the best kill probability of all MANPADS in "MANPADS A Terrorist Threat to Civilian Aviation?" (page 39).

- the proximity fuse has a radius of 5 meters in DCS. The document "ANALISIS DEL MISIL MISTRAL INFRARROJO COMO SISTEMA ANTIMISIL Y ANTIAEREO" cites a proximity fuse radius of 2 meters, more plausible for a missile with a 3kg warhead.

- the value of K = 2 used in DCS in the autopilot part, is too low. For a short range missile, many articles explain that a value of K between 3 and 5 gives better results (see the attached article "Proportionnal Navigation Guidance"). The AMRAAM in its terminal phase uses K = 4 in DCS. Based on my tests, a value of 5 gives the best results for the Mistral (https://cdn.discordapp.com/attachments/925038843399376917/955940311354454056/K_effect.mp4 ). And I know it's not definitive and documented proof, but one would wonder why MBDA would not give the better guidance to its missile...

- the flag_dist  = 150 parameter is too high. It leads to the missile brutally diverging from its target if the target is flanking (see example K = 2 in the video). A value of 50, like the one used for the Igla, combined with K = 5, gives the best hit probability (see example K = 5 in the video).

- the GimbLim parameter has a value of 30°. I propose a value of 38°, based on "Janes Land Based Air Defenses 1992-1993", which cites a gimbal limit of 38° for the Mistral 1, and the SAFRAN Mistral missile seeker document citing a >30° gimbal limit.

- for omega_max, which is the maximum angular tracking rate of the seeker, I propose a value of 20°/second, as stated in the SAFRAN document about the seeker.

- The rocket burn time should be about 2 seconds, rather than 3, based on video evidence ((https://youtu.be/KK9_Iq0AM9k?t=15 ; https://youtu.be/RY78aBlUkMQ?t=27 ).

- I add that the missile should self destruct after 14 seconds of flight time (fuse confirmed to self-destruct in the document "poste de tir Mistral", and 14 seconds max flight time cited in "ANALISIS DEL MISIL MISTRAL INFRARROJO COMO SISTEMA ANTIMISIL Y ANTIAEREO".

- As a bonus, it would be great to see tha shaped trajectory added. The Mistral is designed to have a shaped trajectory (it climbs a bit just after launch, see photo attached). This is especially important to engage enemy helicopters, as it allows the missile to continue to track them even if they try to terrain mask.

You'll find attached a lua file, which is the ED's Mistral file with all the parameters corrected with the values I propose. Some things I haven't included in the lua are the self-destruction at 14 seconds, and modifying the "SeekerSensivityDistance" and "sensitivity" parameters to match a 3.5 times better sensitivity than the Magic 2 missile seeker (according to Janes Land Based Air Defenses 1992-1993. That's for the Mistral 1, but the Mistral 2 we have in DCS basically has the same seeker.)

SAFRAN_Mistral_Seeker.pdf 253.76 kB · 14 downloads ANALISIS DEL MISIL MISTRAL INFRARROJO COMO SISTEMA ANTIMISIL Y ANTIAEREO.pdf 34.7 kB · 5 downloads Proportional_Navigation_Guidance.pdf 1.05 MB · 7 downloads New_mistral.lua 5.92 kB · 6 downloads

 

Thank you for your research, it's much appreciated! I agrred with all changes you propose, except FOV and burning time. It seems like there is a kind of mistake, because FOV is 4 degrees by default(just checked both user and dev DCS versions). With probability of 90% FOV of real missile is between 2 and 4 degrees. More narrow FOV is not quite practical.
Regarding burning time it is 2.2 seconds at the moment in both DCS versions, that seems to be correct according your videos.

[Mad_Shell]

1 hour ago, Маэстро said:

Thank you for your research, it's much appreciated! I agrred with all changes you propose, except FOV and burning time. It seems like there is a kind of mistake, because FOV is 4 degrees by default(just checked both user and dev DCS versions). With probability of 90% FOV of real missile is between 2 and 4 degrees. More narrow FOV is not quite practical.
Regarding burning time it is 2.2 seconds at the moment in both DCS versions, that seems to be correct according your videos.

Thank you for the feedback! I think there is a misunderstanding though. According to the lua exporter by Quaggle, there are 2 different versions of the Mistral missile in the DCS files. The file "./CoreMods/aircraft/AircraftWeaponPack/AA_Missiles.lua" indeed uses a value of 4 degrees for the FOV, and a value of 2.2 seconds for the burn time. HOWEVER, the Gazelle in DCS uses the file located in "./CoreMods/aircraft/SA342/SA342_Weapons.lua", where the FOV is 14 degrees, and the burn time is 3 seconds. A few more values are different between the 2 files.

That's why in my first post I said that I used the  "./CoreMods/aircraft/AircraftWeaponPack/AA_Missiles.lua" file as a basis for my own lua version of the Mistral.

EDIT: also, I have a strong suspicion that the parameter of resistance to flares "ccm_k0" isn't working, and has no real effect. No idea if this could be specific to the Mistral, or if it's the case for all IR guided missiles.

Edited December 29, 2022 by Mad_Shell

[Mad_Shell]

@Маэстро do you have news about the issues I mention in my last message, in particular the Gazelle using another file than the one you thought?

[Маэстро]

On 1/13/2023 at 10:35 PM, Mad_Shell said:

@Маэстро do you have news about the issues I mention in my last message, in particular the Gazelle using another file than the one you thought?

Changes already committed, so it's up to Polychop now. They should change Gazelle's payload script.

[Flappie]

Hello @Mad_Shell. ED Mistral was fixed. Now, Polychop should use ED implementation of the Mistral. Maybe they have done so already, I haven't checked. Let me know.

[Mad_Shell]

14 hours ago, Flappie said:

Hello @Mad_Shell. ED Mistral was fixed. Now, Polychop should use ED implementation of the Mistral. Maybe they have done so already, I haven't checked. Let me know.

I asked the Gazelle developper about it, and here is his answer:

"Hey there, In the current version, the gazelle still uses our own Mistral. This has to do with the fact that the ED mistral has had a sound issue that was only resolved last week. We plan to switch to the ED missiles in an upcoming update."

And here is a pic of the upcoming updated launcher tubes he attached to his message:

Edited March 11, 2023 by Mad_Shell

[Flappie]

Excellent!

[Polychop Simulations]

I gave Mad_Shell a customized weapons lua to test the ED mistrals on the current OB version of the Gazelle in advance of the update we're working on.
With that said, when we switch over to the ED mistral, the functioning of the missile as well as the performance will be out of our hands. @Mad_Shellfeel free to post your findings on testing the ED Mistral, in the end it is what the Gazelle will soon be using. 

EDIT: Apparently I spoke too soon and assumed the mistral being mentioned in the recent change logs meant the sound issue was resolved. It however still persists. It is not game breaking but basically comes down to the sound kicking in seconds after launch. We hope this will get addressed before the release of the Gazelle update. 

Kind regards,

Dan

Edited March 11, 2023 by Polychop Simulations
closing + author name

[Mad_Shell]

@Маэстро After a bit of testing, I found some problems with the new ED's version of the missile, so here are my suggestions:

- X_back = 0 seems strange, since it should be the location of the exhaust along the X axis, and 0 should be the center of the missile. I propose X_back = -0.90, the value used for the nozzle_position parameter in the "march" section) 

- sigma = {10, 10, 10} is too high, and leads to about 15% of shots missing a static Ka-50 not launching any flares. Since MBDA advertises a 93-97% hit rate during exercises on moving targets smaller than a Ka-50, I propose sigma = {3, 3, 3}, which according to my testing should give very close results to MBDA's claims.

- Fi_start is too small. I know it's realistic, but the AI Gazelles don't manage to use the missile on any target with some angular velocity because the "cone of fire" is too small. Based on my testing, Fi_start = 10° gives good results without making it a high boresight missile for the AI.

- work_time = 0.2 is too long. On the real life videos, we can see the booster impulse is very, very short, and I propose to keep work_time = 0.048 like in Polychop's file.

- ccm_k0 doesn't have any effect (see https://forum.dcs.world/topic/321195-possible-massive-bug-affecting-many-ir-missiles-and-possibly-radar-missiles-too/#comment-5171557), giving the missile a very, very poor resistance to flares (while IRL it is reputed as having very good counter-countermeasure). If ccm_k0 works again one day, I propose a value of ccm_k0 = 0.3 (a bit worse than AIM_9X, but better than the MagicII, which is older and of which the seeker was used to design the Mistral seeker).

- we have cx_coeff = { 0.6, 1.6, 0.68, 0.55, 1.85 } in ED's file, and cx_coeff = { 0.65, 1.7, 1.6, 0.45, 0.01 } in Polychop's file. I really don't know which one is closer to reality, but given the importance of this parameter, sorting it out seems important. Maybe @Polychop Simulations  and @Маэстро can give us some insight on how they calculated those parameters for this missile?

- the ED's version doesn't spin on itself (it does IRL). The Polychop's version spins, I guess because it uses scheme="schemes/missiles/self_homing_spin_missile.sch", while ED uses scheme = "schemes/missiles/mistral_missile.sch"

@btd this one is for you: as said above in Polychop's message, when the ED Mistral file is used, there is a delay of about 2 seconds between the missile launch and the sound of the missile launch playing (and no, I wasn't looking from 700 meters away lol).

 

I attach the AA_missiles.lua modified with all the changes I suggest, excepting the "scheme" parameter (when I put scheme="self_homing_spin_missile" in ED's version, DCS crashes as soon as the missile is fired). The cx_coeff parameter is still the ED one too.

 

AA_missiles.lua

Edited March 13, 2023 by Mad_Shell

[Thorns]

I love the Gazelle...Please make the Mistral so it can be used on the Enigma Cold War Server in DCS...The Hind has missiles and Mr. Enigma says the Gazelle Mistral is not modeled correct so they won't allow it.  So, I have to kill the big bad Hind with the 20mm gun...with a lot of ammo used...Thanks!

 

[btd]

On 3/12/2023 at 3:32 AM, Mad_Shell said:

@btd this one is for you: as said above in Polychop's message, when the ED Mistral file is used, there is a delay of about 2 seconds between the missile launch and the sound of the missile launch playing (and no, I wasn't looking from 700 meters away lol).

I am not sure I can help here, it is not my playground. But I can try to ask some of developers to help. 

[Маэстро]

Hi @Mad_Shell,

Some of parameters such as X_back and sigma are legacy ones and have no effect on newer missile API.
 

Quote

Fi_start is too small. I know it's realistic, but the AI Gazelles don't manage to use the missile on any target with some angular velocity because the "cone of fire" is too small.

We'll think of it. But we should account for RL limitations if there are any.

Quote

ccm_k0 doesn't have any effect (see https://forum.dcs.world/topic/321195-possible-massive-bug-affecting-many-ir-missiles-and-possibly-radar-missiles-too/#comment-5171557), giving the missile a very, very poor resistance to flares (while IRL it is reputed as having very good counter-countermeasure). If ccm_k0 works again one day, I propose a value of ccm_k0 = 0.3 (a bit worse than AIM_9X, but better than the MagicII, which is older and of which the seeker was used to design the Mistral seeker).

Please, see answer in coresspnding topic.

Quote

work_time = 0.2 is too long. On the real life videos, we can see the booster impulse is very, very short, and I propose to keep work_time = 0.048 like in Polychop's file.

Unfortunately, it's barely possible to estimate such a short burn time by videos. We also should retain acceleration within reasonable limits. As far as we know booster gives missile about 40m/s of initial velocity, so 0.2s -> 20g axilal acceleration, 0.05s -> 80g. That's a qute hard kick. Anyway this no any difference from gaming point of view between these values.

Quote

we have cx_coeff = { 0.6, 1.6, 0.68, 0.55, 1.85 } in ED's file, and cx_coeff = { 0.65, 1.7, 1.6, 0.45, 0.01 } in Polychop's file. I really don't know which one is closer to reality, but given the importance of this parameter, sorting it out seems important.

Our drag values are correct ones, because they based on our own CFD research. That was one of the reasons why we decided to make our mistral version.

Quote

this one is for you: as said above in Polychop's message, when the ED Mistral file is used, there is a delay of about 2 seconds between the missile launch and the sound of the missile launch playing (and no, I wasn't looking from 700 meters away lol).

We aware of this problem. Booster produces no sound. Will fix.

Quote

the ED's version doesn't spin on itself (it does IRL).

Is there any solid proofs? Missile itself looks absolutely symmetrical and has two pairs of fins, so looks like there is no any reasons why it should spin.

[Mad_Shell]

4 hours ago, Маэстро said:

Some of parameters such as X_back and sigma are legacy ones and have no effect on newer missile API.

You probably have your reasons, but wouldn't the "good coding practice" be to keep the code as clean as possible and remove the now useless parameters?

4 hours ago, Маэстро said:

We'll think of it. But we should account for RL limitations if there are any.

Yes it should be carefully tuned, but I think the way the AI is flying really prevents it to effectively use the missile in many cases with such a low Fi_start value.

4 hours ago, Маэстро said:

Is there any solid proofs? Missile itself looks absolutely symmetrical and has two pairs of fins, so looks like there is no any reasons why it should spin.

Well, the document I attached in my second message in the thread mentions that the missile is put in rotation by the booster. BUT... after watching a few videos in slow motion the missile doesn't seem to spin after the booster ignition... and I agree with you that the 2 pairs of canards suggest a non rotating missile.

[AeriaGloria]

Apparently the engine is what causes the spin, from bulgarianmilitary.com