MK 20's

[Flapjacks]

Hey all, I made a post earlier about how I couldn't get cbu-97's on target and someone pointed out its a known issue that cbu's are opening prematurely. Now I'm trying the mk-20 rockeyes and I can't get these on target either. They seem to be deploying on time but they're a good ways off to one side or the other. Does anyone else have this problem? I didn't see a mention in the changelog known issues post. I'd assume the F-15's computer would calculate for any windage, would it not?

[AvroLanc]

All CBU are suffering from multiple issues at the moment. SPIN for -87s doesn’t seem to be modelled and the MK-20 have incorrect fuze settings. 

The ballistics seem to be wrong if you set a burst altitude above 1200ft. And the dispense/coverage areas are completely different to other aircraft with similar settings. 

Hoping they get some attention soon. 

[Flapjacks]

Ah ok, well, glad its not just me. Thanks!

 

[Mr_Blastman]

5 hours ago, Flapjacks said:

Hey all, I made a post earlier about how I couldn't get cbu-97's on target and someone pointed out its a known issue that cbu's are opening prematurely. Now I'm trying the mk-20 rockeyes and I can't get these on target either. They seem to be deploying on time but they're a good ways off to one side or the other. Does anyone else have this problem? I didn't see a mention in the changelog known issues post. I'd assume the F-15's computer would calculate for any windage, would it not?

I set my 97s to 1200 ft. Burst altitude and then aim for the center point of say a dual ripple release and they hit smack dab where they should.  This is wrong, because that means I have to lead a single 97 by quite a fair to ensure a hit, but works for now, nonetheless.

I have accommodated for wind by setting up missions with zero wind, but still they are off slightly.

[Mav87th]

As far as I can find out. It's not possible to set any fuzes on the F-15E except on the mk-84. Neither of the CBU's has any fuze options in the munitions window in the mission editor. So I guess?? that each bomb has a hard coded value for time and height for now....

[Zahnatom]

13 hours ago, Mav87th said:

As far as I can find out. It's not possible to set any fuzes on the F-15E except on the mk-84. Neither of the CBU's has any fuze options in the munitions window in the mission editor. So I guess?? that each bomb has a hard coded value for time and height for now....

you change them in the PACS where you'd load the weapon types. bottom right corner should say "FUZE" and if you click that you can change the fusing for the cbu97 for example

[Mav87th]

@Zahnatom

Hi - yea i'm well aware of that, BUT that does not change the behavoir of the bomb. As others have experienced as well it does not matter if you set the fuxe to 3000 ft or 700 ft or the timer to 0.95 sec or 4.whatever. Changing Fuze settings via PACS does nothing. And that would be quite realistic, as in real life you would make the changes on the Mk-20 bomb (back in pre 1999) on the fuze it self before flight. We can not do that on the Mk-20 as it is now via Mission Editor.

[Ramsay]

On 8/13/2023 at 11:08 AM, Mav87th said:

Hi - yea i'm well aware of that, BUT that does not change the behavoir of the bomb. As others have experienced as well it does not matter if you set the fuxe to 3000 ft or 700 ft or the timer to 0.95 sec or 4.whatever. Changing Fuze settings via PACS does nothing.

Changing the PACS fuse height of the CBU-97 DOES change the burst altitude in DCS (even in flight) as is shown in the TACVIEW pictures in this post.

 

Whilst unrealistic, changing the CBU-97 burst height while in flight is required ATM as the DCS F-15E's default of 700 ft AGL will have the BLU-108's crashing into the ground if released at medium to high altitudes i.e. 16,000 ft.

With the CBU-97 burst altitude changed to 1200 ft AGL, the BLU-108 parachutes have suficient time to deaccelerate and submunitions deploy correctly.

I haven't tested the behaviour of Mk-20's

Edited August 15, 2023 by Ramsay

[Mav87th]

Yea Ramsay

 

CBU-97's seems about right in behavour. And thats funny as it should have the same fuze as the MK-20 (FZU-39). And yes it is required to set it in flight if you want to change it, but in reality it should be set on the FZU fuze on the bomb it self, and then the system in the jet (PACS for F-15E) should be set to mirror that setting, in order for the system to make the right calculations for the delivery.

 

CBU-87's behaves like the MK-20s (which is similar to "does not work")

In reality the MK-20 should not even have the option to select HEIGHT, as the fuzes it has are soly time based fuzes.

Some early MK 339 fuzes were pre-selected so that only the 4.0-second option time could be utilized. These fuzes were assembled in single function MK 20 MOD 2 (ROCKEYE II) weapons.

 

Edited August 15, 2023 by Mav87th

[Ramsay]

30 minutes ago, Mav87th said:

CBU-87's behaves like the MK-20s (which is similar to "does not work")

I can confirm the Mk-20 burst height was unaffected by fuse settings (always burst at ~650 ft)

However I've just finished testing if the CBU-87 worked and like the CBU-97, it's FZU39 proximity fuse was working (I tested 900 ft and 1200 ft settings)

CBU-87 PACS settings with FZU39 selected and a 1200 ft burst height

[Ramsay]

54 minutes ago, Mav87th said:

Some early MK 339 fuzes were pre-selected so that only the 4.0-second option time could be utilized. These fuzes were assembled in single function MK 20 MOD 2 (ROCKEYE II) weapons.

How  would that work when dropped from 12,500 ft i.e. the time of fall for the Mk-20 Rockeyes from 12,500 ft to their 650 ft AGL burst height in DCS is ~29 seconds

[Mav87th]

@Ramsay - i would suppose that droping from level flight at 12k ft. was just not an option. Burst spread pattern was selected by planning the pickle and delivery altitude pre-flight and then adhering to that plan.

[GumidekCZ]

Generaly Rockeye (MK 20) have fron fuze modelled for every module here in DCS, not just F-15E.
IRL for MK 339 MOD 1 fuze, you can load two separate values of Arming Delay corresponding to the primary (AD1 - NOSE) or secondary (AD2 - NSTL) option timers - both timers set on ground. As you cycle inflight between NSTL and NOSE, the function times change to reflect this. TAIL select = DUD.
Rockeye was fitted only with a primary and secondary timed delay fuze, which had to be both preset on the ground. Settings from 1.2 to 100 seconds.
The fuze is preset at 1.2 seconds for primary delay, and the option delay is preset at 4.0 seconds.

If you want the munition to function at a particular burst altitude (BA) to optimize coverage, you  need only load that altitude in the SMS and the pull-up anticipation cue will function to let you know when you reach that (minimum) altitude. In this sense, the pull-up anticipation cue is not trying to satisfy a minimum fuze arm constraint, but is trying to indicate the optimum release point to ensure the correct function altitude.

https://info.publicintelligence.net/USNavyRocketBombFuzeManual.pdf
 

Edited December 23, 2023 by GumidekCZ