correct as is CBU-99 Zero damage unless scoring a full target hit

[Kah0tika]

After further testing I did manage to get some kills in CCRP on these non moving BMPs but it was almost impossible in CCIP.
In fact if the clusters don't directly hit the BMPs it won't even scratch them.
Is this supposed to be this way and used only against very soft targets?
I would have expected them to be effective against BMPs too.
 

 

CBU99_Bug.trk

Edited Monday at 06:13 PM by Kah0tika
Edit after further testing

[BIGNEWY]

Hi,

you are using the default airburst altitude of 300 ft, which is insufficient for proper dispersion with the FMU-140 fuze. You should use at least 1,500 ft airburst for armour penetration to be successful. Hope that helps  

 

[Spartan111sqn]

2 hours ago, BIGNEWY said:

Hi,

you are using the default airburst altitude of 300 ft, which is insufficient for proper dispersion with the FMU-140 fuze. You should use at least 1,500 ft airburst for armour penetration to be successful. Hope that helps  

 

Thanks, maybe a doc or white paper indicating some parameters for some weapons is needed, in some cases we are a bit lost on it.

[Kah0tika]

Thank you for the answer.
I should have mentioned in my edit that I did have better results with a 1500ft airburst and above.
Yet it's still extremely difficult to damage light armoured vehicles with it.
Usually it take one precise direct hit and seems in inflict no damages to other nearby vehicles and objects.
In CCIP on moving targets I can visually see the area of impact being clearly on top of the vehicles but doesn't do much more than a cloud of dust.
I'll test a little more and come back with additional results.

[Renko]

On 11/4/2025 at 9:51 AM, BIGNEWY said:

Hi,

you are using the default airburst altitude of 300 ft, which is insufficient for proper dispersion with the FMU-140 fuze. You should use at least 1,500 ft airburst for armour penetration to be successful. Hope that helps  

 

I think the issue comes from the explosions effects discrepancy

I noticed this a while ago

and today during test to report it i noticed something.
Even if i changed the Airburst Height at which the submunitions released, the effect remained the same. The visual effect of it i mean.

If you slow down the replay you can see the submunitions diferent dispersions, but the visual effect will mislead the user.
I think it will worth to update the visuals to match the dispersion. That will help the user to see what the settings and how he deployed it really does.
null

[Dragon1-1]

19 hours ago, Kah0tika said:

Usually it take one precise direct hit and seems in inflict no damages to other nearby vehicles and objects.

This is realistic, the submunition has a HEAT warhead about the size of a hand grenade. If it doesn't land directly on top of an armored vehicle, it won't do a whole lot, and it doesn't even fragment all that much. The visuals are fake because actually showing 247 distinct bomblets and corresponding explosion effects per bomb (meaning a 4-bomb ripple has almost 1000 of the buggers, and a fully loaded four ship of Hornets will dispense close to 8000) would likely bog down the sim.

[SloppyDog]

Damage effects of CBU-99s with FMU-140 are hit or miss...literally.

I've been testing them for some time, and the best results I have are with CBU-99 with Mk 339 at low altitude.

For FMU-140, as per ED's instructions on September 7th changelog, for DCS 2.9.20.15010, under the Weapons section it reads:

• Mk-20/CBU-99. Improved bombsight accuracy. Please note that using FMU-140 in low-altitude horizontal flight bombing runs will lead to poor accuracy - in these cases Mk 339 fuze must be used. FMU-140 should provide acceptable accuracy in dive bombing runs and, in specific conditions, in horizontal flight bombing runs (function altitude set to ca. 1/3 of release altitude and specific airspeed at release, e.g. function altitude - 3 kft, release altitude - 10 kft, TAS - 580 kts)
•  
• Mk-20/CBU-99. Fixed Mk 339 fuze function delay being counted down after arming instead of after release

In my testing, FMU-140 works best by flying level,dropping  at 10,000 feet, with an airburst of 3,000 feet AGL, using AUTO mode.
This way the bomblets have enough time to arm and spread. The spreadsheet below gives you an idea of various profiles for dropping these cluster munitions. (If you are asking yourself why would I spend too much time doing this and testing, the answer is: I'm a stubborn nerd).

So, the end game is that you must allow time for the bombs to separate from the aircraft, open and, most important, arm. 

However, the bomblets do cause damage only when they directly hit the targets. Funnily enough, the result is that -99s are most effective against armored than against light targets. I blame that on the lack of a proper fragmentation model, but ED said they are working on it. From the July 23rd changelog:

• Weapons. Work in progress fixes for the following bombs explosive mass: M117, Mk-80 series, and WWII AN-M GP series. This also applies to Guided Bomb Units (GBU) that use the Mk-80 series of warheads. This is connected to the changes for SAMP bombs that we did in the previous patch and will be evaluated and finalized in future patches. Most rocket warhead families (at least Hydra/Zuni/FFAR, S-5/8/13/25, and SNEB-68) are already set up with parameters that match our available sources. Actual effect on targets is subject to change along with implementation of the fragmentation model. (We missed mentioning this in June 18’s update).

Try to hit the same targets with Mark 82s, and better yet, Mark 84s. You don't need to hit light targets directly, they'll catch fire from the frag effect.

P.S.: I forgot to mention that the -99s are falling short, either in AUTO or CCIP mode.

 

 

 

 

 

  

 

CBU-99 Height of Function.xlsx

Edited 6 hours ago by SloppyDog

[Kah0tika]

6 hours ago, Dragon1-1 said:

This is realistic, the submunition has a HEAT warhead about the size of a hand grenade. If it doesn't land directly on top of an armored vehicle, it won't do a whole lot, and it doesn't even fragment all that much. The visuals are fake because actually showing 247 distinct bomblets and corresponding explosion effects per bomb (meaning a 4-bomb ripple has almost 1000 of the buggers, and a fully loaded four ship of Hornets will dispense close to 8000) would likely bog down the sim.

Interesting.
I initially thought the bomblets were not powerful enough to do any damages so I decreased the burst hight to 300 in order to have a more concentrated effect but actually had worse results.
So if it works as intended it seems these bombs are quite under powered.
 

6 hours ago, SloppyDog said:

However, the bomblets do cause damage only when they directly hit the targets. Funnily enough, the result is that -99s are most effective against armored than against light targets. I blame that on the lack of a proper fragmentation model, but ED said they are working on it. From the July 23rd changelog

That might indeed be part of the problem.
I think there might be a hit detection system/damage model  issue on some vehicles.
When I go for a gun run sometimes it destroys or realistically damage some BMPs. But sometimes I can send 200 rounds impacting directly the side of the target with zero effect. In this case it's the BMP3 which seems to be stronger than a tank.
I've notice the same issues with rockets.
Something is definitely wrong. And I suspect it's the same issue that is affecting the GBU99s.

Here's a youtube clip that illustrate the issue.
In the Debrief windows we can see it registered 153 direct hits...but zero damages.
Now I wouldn't expect a BMP to survive a 20mm canon direct hit on the side and on the top.
Even a tank would take substantial damages with repeated hits in the back or on the top.

 

Hit_detection_test.trk

Edited 2 minutes ago by Kah0tika
added content and precisions