CBU Fuze Options

[felixx75]

Hi, in the rearm & refuel menu for CBU's you can select a fuze time and/or a fuze height. I assume in the airplane I select one or the other option via the nose/tail arming switch. But which setting applies to which option?

[felixx75]

How can it be that no one can give an answer to this? As long as the bomb has not yet left the plane, and that is the case when I select the fuze option, that is Heatblur's responsibility. What happens after the weapon is dropped is, of course, ED's territory.

 

Edited January 23 by felixx75

[PawlaczGMD]

You're right, I just checked, and this weapon has both airburst delay and altitude in a single fuze. I have no idea how it works from the loadout menu information.

[Volator]

I can only check on the older CBUs, the manual I have available does not include the CBU-87 as that weapon is too new for the manual. You are probably refererring to the latter one though as the in-game CBU-52s and BL755 do not offer any fuse options in DCS, right?

So this might be of no interest to you:

Spoiler

According to the real manual, e.g. CBU-52/58 have the M907 mechanical timer fuze only that is pre-set to a value between 4 and 92 seconds on the ground. The manual doesn't say that there are any selectable options via the Nose/Tail arming switch.

Mk-20s also come with a mechanical timer fuze (Mk339) and also do not offer any selectable options via the Nose/Tail arming switch according to the manual.

The only selectable option in the air I have seen so far is the LD/HD thing for Mk.82s.

For the CBU-87 I only found this in a Chuck's guide for the F-15E (!):

 

Quote

 

CBU-87 Combined Effects Munitions (CEM) weighs 950 lbs and is an all-purpose cluster bomb.

Fuze Setting:

•N/T (Nose & Tail): Bomblets dispense using settings displayed on ARMT/PACS page

•NOSE: Bomblets dispense immediately after release

•TAIL: Dud (Disarmed)

 

 

... and Wikipedia says this:

Quote

Each CBU-87 consists of an SUU-65B canister, a fuze with 12 time delay options [...] The CBU-87 can also be equipped with an optional FZU-39/B proximity sensor with 10 altitude selections.

(Since my squadron is a Cold War Luftwaffe F-4 squadron, we do not use the CBU-87 and thus never came across this issue)

Edited January 23 by Volator

[felixx75]

Thank you very much for your help. It's almost funny that even in the Heatblur Discord, the Heatblur team themselves don't know how to...

[Zabuzard]

2 hours ago, felixx75 said:

It's almost funny that even in the Heatblur Discord, the Heatblur team themselves don't know how to...

The thing is, no one knows it ad-hoc. We can figure it out if you put a dev on, but right now we are all super busy (as usual).

Your request has been heard and you will get a detailed answer from us at some point. Most likely at the same time when we want to expand this section in the manual with said details.

Edited January 23 by Zabuzard

[felixx75]

1 hour ago, Zabuzard said:

The thing is, no one knows it ad-hoc. We can figure it out if you put a dev on, but right now we are all super busy (as usual).

Your request has been heard and you will get a detailed answer from us at some point. Most likely at the same time when we want to expand this section in the manual with said details.

Thank you for your answer. That's basically all I wanted to hear. So far it's just been “nobody knows”. That was of course not very satisfactory. But now I know more that it seems to be really difficult. So thank you very much and I'm sorry if I sounded a little indignant.

[Massun92]

2 hours ago, felixx75 said:

Thank you for your answer. That's basically all I wanted to hear. So far it's just been “nobody knows”. That was of course not very satisfactory. But now I know more that it seems to be really difficult. So thank you very much and I'm sorry if I sounded a little indignant.

Maybe we can develop a consist method of study and give a little hand to the heatblur team... make some test and share the results here. When I have some time I will try for my self

[Massun92]

Run some test. For the moment in all the fuse configurations the droplets disperse by height and not for time. Tail= height / nose= eight / nose and tail= eight / safe= spins but not open the cannister. 

BTW -- the canister should spin entirely? looks weird...

[MagicSlave]

Run some test. For the moment in all the fuse configurations the droplets disperse by height and not for time. Tail= height / nose= eight / nose and tail= eight / safe= spins but not open the cannister. 

BTW -- the canister should spin entirely? looks weird...

I don't remember the reference but I read that CBU fuze time sets the minimum time to arm (to prevent own aircraft damage) and the radio altimeter height is used to trigger the function (i.e. open the canister)

Sent from my FP4 using Tapatalk

[Massun92]

2 hours ago, MagicSlave said:

I don't remember the reference but I read that CBU fuze time sets the minimum time to arm (to prevent own aircraft damage) and the radio altimeter height is used to trigger the function (i.e. open the canister)

Sent from my FP4 using Tapatalk
 

that sounds logic to me.. thanks for the info

[MagicSlave]

Document T.O. 1-IM-34 seems to be publicly available
"The FZU-39/B (FIGURE 2-34) is a proximity sensor used on the SUU-64/B (CBU-89/B) and SUU-65/B (CBU-87/B). When activated, the FZU-39/B transmits an omnidirectional signal which it uses to measure the vertical height above ground level. When the measured height above the ground equals the preset function altitude, the sensor sends a fire pulse to the integral fuze, opening the SUU-64 dispenser (FIGURE 2-35). When the preset SUU-65/B function altitude is reached, the FZU-39/B sends a signal for fin cant, causing the dispenser to spin. Upon reaching the selected spin rate setting, the SUU-65/B opens. The pilot has the option of changing from time func tion to proximity function by arming both the nose and the tail solenoids."

If I read this correctly, pilot should be able to select either time or proximity function via nose/tail setting

Edit: so it seems that my prior statement was wrong

Sent from my FP4 using Tapatalk

[Massun92]

On 1/24/2025 at 11:22 AM, MagicSlave said:

Document T.O. 1-IM-34 seems to be publicly available
"The FZU-39/B (FIGURE 2-34) is a proximity sensor used on the SUU-64/B (CBU-89/B) and SUU-65/B (CBU-87/B). When activated, the FZU-39/B transmits an omnidirectional signal which it uses to measure the vertical height above ground level. When the measured height above the ground equals the preset function altitude, the sensor sends a fire pulse to the integral fuze, opening the SUU-64 dispenser (FIGURE 2-35). When the preset SUU-65/B function altitude is reached, the FZU-39/B sends a signal for fin cant, causing the dispenser to spin. Upon reaching the selected spin rate setting, the SUU-65/B opens. The pilot has the option of changing from time func tion to proximity function by arming both the nose and the tail solenoids."

If I read this correctly, pilot should be able to select either time or proximity function via nose/tail setting

Edit: so it seems that my prior statement was wrong

Sent from my FP4 using Tapatalk


 

Great.. I made more test. Dropping close to the height and without reaching the delay time wasn't working neither. For the moment, the time delay looks like it does nothing

[felixx75]

On 1/24/2025 at 3:22 PM, MagicSlave said:

...The pilot has the option of changing from time func tion to proximity function by arming both the nose and the tail solenoids."...

If I read this correctly, pilot should be able to select either time or proximity function via nose/tail setting

Sounds like “nose” is the time fuze and nose/tail is the height fuze. 

Edit:
After a short test, it doesn't seem to make any difference in DCS for the F-4 whether you select nose, tail or nose/tail. In any case, the time fuse is not used.

Edited January 26 by felixx75