reported CBU-99 not bursting at 1500ft with MFUZ=VT

[RndName]

Version: 2.5.6.49314 (also tested with 49718 and still exists)

TLDR:

CBU-99 is not bursting at 1500ft AGL with MFUZ=VT. It burst approx. 1.2secs after reaching the 1500ft AGL (at actually 670ft).

Detailed:

The CBU-99 is configured with MFUZ=VT; EFUZ=OFF; HT=1500.

 

• Released at 7500ft, 540 IAS and 33° dive angle
  
• The bomb flew multiple secs until reaching 1500ft, so it should be armed already.
  
• The burst occured at ~670ft MSL (only 33ft ele at this place), which should be approx. 1.2s after reaching 1500ft AGL regarding the dive angle and speed. Additional information: In the Tacview replay i see a direct distance between the cbu-99 and the target of approx 1500ft as it bursts (could be a coincidence or maybe there is a bug that the distance is used instead of the actual height?)
  
• As a result of this late activation i think the bomb is very inaccurate (ccip Pipper calculates with 1500ft???) -> Would be very interesting to have some technical detail here
  

Manual says on page 135 that it only arms 1.2 after release:

"HT Option. For the Early Access release, the Mk-20, CBU-99, and CBU-100 canister weapons default to use FMU-140 fuses. This is a fixed-setting fuse with an arming time of 1.2 seconds after release."

This behaviour is also researched and described by other users in this thread: https://forums.eagle.ru/showthread.php?t=217264&page=5

I would expect that the cbu-99 will burst at exactly 1500ft AGL once armed (1.2s after release). Or do i understand the expected behaviour completly wrong and this is the right behaviour?

I currently can only use this type of weapon to hit sth. with the PRI MFUZ Setting.. But maybe i am just too stupid to understand the CBU

Btw.: The manual is also wrong regarding the efuze settings which where already changed to efuze=off. It currently says on page 135 we have to put efuze to INST. But thats not the point in this thread here..

CBU-99_MFUZ_VT.trk

[Oilman100]

I have seen this exact same issue, with Tacview it is a very consistent burst height of about 700ft and as you stated it becomes inaccurate and the kill zone is allot less. I’ve also use PRI mode and this works as stated with a burst 1.5s after release, but requires a bit more calculation to get the right release height. Has been like this for a long time, the Rockeye has also the same issue

[Santi871]

I'll check

[Frederf]

Confirm. CBU-99 are bursting 1.2s after falling below 1,500' AGL. Depending on the angle the bomb is traveling this may be slightly below  or greatly below 1500'.

 

F18CBUFuze.trk

[uboats]

[BIGNEWY]

reported for checking 

 

thank you

[Ozone42]

I can  reproduce what's reported by "Maverick Su-35S" in this video https://youtu.be/OjtLvgA27hM, that looks like a bug: When dropping a CBU-99 from a high altitude, so that the CBU-99 turns down in a high angle (according to Maverick, about 45 degrees or more), then the bomb disperses at a very low altitude, regardless of the HT setting. I tested this by first dropping a CBU-99 from about 3000 ft with HT at 1500.  I placed a helo at 1500 ft so that I could see that it disperses at the right height. This worked as expected (the bomb was still at a low angle). I then did the same again, but released the bomb from 10000 ft. From here, the bomb always disperses at a very low altitude, regardless of the HT setting.

 

Running latest stable, 2.5.6.61527.3.

 

Track file attached.

clusterbug.trk

Edited March 8, 2021 by Ozone42
Added DCS version information

[BIGNEWY]

Merged. 

 

thanks this is already reported.