Jump to content

CBU105 against moving targets?


Two-Six

Recommended Posts

I was wondering how best to deploy a CBU 105, the GPS guided anti armor cluster munition against a moving convoy.

 

I have been putting my targeting pod into point track and designating a point on the road a good way ahead of the moving convoy so hopefully they will arrive under where it deploys its payload of skeats. It seems to work but its a bit hit and miss just guessing where the convoy will be in 15 to 20 seconds time.

 

However is there a better way like using point track to lock onto a moving vehicle so that so the calculated release point with other cluster munitions or where the system guides the bomb to with the CBU 105 will be the best place to drops its skeats?

 

How best to use cluster weapons and the CBU 105 against moving targets?

Link to comment
Share on other sites

I was wondering how best to deploy a CBU 105, the GPS guided anti armor cluster munition against a moving convoy.

 

I'm sure there are some simple rule-of-thumb ideas to gauge the speed of a vehicle and then come up with a rough estimate on where to aim the bomb, but to the best of my knowledge, it really is the pilot's job to do that; there are no calculations performed by the IFFCC to aid in aiming for a moving target.

 

Knowing the bomb's time of fall plus the time it takes for the skeets to deploy should help with that estimation, but it's still all rule-of-thumb stuff.

 

And a tiny side-note: the CBU-105 is actually INS-guided, not GPS-guided. The aircraft's GPS is used to update the bomb's INS prior to release, but after pickle, the bomb only uses its own INS (again, to the best of my knowledge).

  • Like 1
Link to comment
Share on other sites

Time Speed Distance Calc. It's kinda hard to do without a scale tho.

 

I usually use CBU 97s for convoys for this exact reason. It's a little easier to use a 97 because the splash is closer to the release time so the convoy distance isn't far off. also you can lower the burst height of the CBU down to 500 or 300 feet. It'll tighten up the pattern but make it easier because it reduces the time on target of the skeets. other option is to use MK82s and set an interval of 40-80 feet and ripple 6-12 of them. another option is to wound or kill the lead vehicle (Depending on the ROE of the convoy) and sometimes they'll scatter for a few minutes. use that time to set up a drop.

Best Complement: "You fly like a Psychotic 5 year old" :joystick:

 

[sIGPIC][/sIGPIC]

 

Link to comment
Share on other sites

That's a good answer, thanks for that.

 

Yep INS guided..that's kind of how I imagined it to work.

 

Its guess work then.

 

So how does the bomb guide it's self to the designated target point, does it have steering fins like a guided bomb or does the skeat dispensers try to go the that designated area or deploy their skeats to the designated point?

Link to comment
Share on other sites

The fins on the back I believe steer the bomb, and spin it up. I believe with the 87 and 103 you can adjust the spin rate. The guidance of the 105 works a lot like the GBU 38 and other GPS guided bombs. The skeets disperse at the input height and just randomly spin and shoot at what they see.

 

This vid kinda talks about how the BLU 108 works. It's like guided randomness.

 

Best Complement: "You fly like a Psychotic 5 year old" :joystick:

 

[sIGPIC][/sIGPIC]

 

Link to comment
Share on other sites

So how does the bomb guide it's self to the designated target point, does it have steering fins like a guided bomb or does the skeat dispensers try to go the that designated area or deploy their skeats to the designated point?

 

The CBU-103 and CBU-105 bombs (aka "dispensers", in this case) guide themselves to the designated coordinates and then start their firing sequence at the programmed height above ground level (Height Of Function, HOF in the DSMS).

 

CBU-87 and CBU-97 pretty much do the same, just without the guidance.

 

Everything after the beginning of the firing sequence should be identical between 87/103 and 97/105.

 

The fins on the back I believe steer the bomb, and spin it up.

 

Which one exactly are you talking about in this case?

 

87 and 103 do spin, yes, and the footprint of their submunition impact pattern is determined by the dispenser's rate of spin and HOF (see 476th CBU-87 footprint materials with some good estimates on that).

 

The CBU-97 and and CBU-105 don't spin or rotate. The video on the BLU-108 submunition that you posted showed that very well: the dispensers, regardless whether they're JSOW of CBU-97/CBU-105 don't spin prior to the release of the submunitions. This also means that the CBU-97 footprint doesn't depend on height of function all that much. But since the submunitions fall to the ground on parachutes and then launch their rocket motors at a preset height, the dispenser's HOF has an impact on the time it takes the skeets to go live, and thus also influences how far they may be drifted off target by the wind (the CBU-105 itself is wind-corrected, like the name says, but the submunitions are not).

 

And as always: to the best of my knowledge. ;)

Link to comment
Share on other sites

The 103/105 canister itself is guided. The submunitions are not. The 87/97 canister may spin but the 103/105 canister will not. WCMD is essentially just the tail kit which replaces the standard tail for guidance. WCMD flies the canister with the tail in a + orientation without spinning using moveable fins.

 

I've tried the following tactic against a moving target on a road:

 

  • Estimate target speed
  • Estimate weapon lead time (e.g. 60s from 25,000')
  • Determine lead distance (e.g. 1nm)
  • Select trigger point
  • Select interception point one lead distance after trigger point
  • Fly just outside LAR
  • Enter LAR and release weapon when target is at trigger point
  • Weapon and target both arrive at interception point simultaneously

This should be how artillery against moving targets is traditionally done. I've had limited success in DCS. Teamwork with wingman or others and practice could possibly improve the success rate.

Link to comment
Share on other sites

The 87/97 canister may spin but the 103/105 canister will not.

 

Just for clarification, there's a typo, right? I believe it should read:

 

The 87/103 canister may spin but the 97/105 canister will not.

 

TBH, I'm not sure how WCMD guidance works when the 103 is spinning, but if it wasn't spinning, it would work very differently from the 87 it is based on.

Link to comment
Share on other sites

Not a typo but a wrong idea. SUU-66 dispenser for any SFW uses gas bags not spin for dispersal. SUU-65/CBU-87 has it's 0-2500RPM settings.

 

SUU-65/CBU-103 is the one I don't know about. I think WCMD can't guide spinning but transitions from non-spinning to spinning immediately before dispense or something like that. It's possible theoretically it's able to steer spinning at 42 times per second but since it's INS it might be able to glide without rotation until it knows it's close and on trajectory and then cant all the fins at the last second to spin up to dispense RPM. It's a theory, I haven't found any detailed mechanization description.

 

Oh and none of the CBUs in DCS spin no matter what settings I have.

Link to comment
Share on other sites

I think WCMD can't guide spinning but transitions from non-spinning to spinning immediately before dispense or something like that. It's possible theoretically it's able to steer spinning at 42 times per second but since it's INS it might be able to glide without rotation until it knows it's close and on trajectory and then cant all the fins at the last second to spin up to dispense RPM. It's a theory, I haven't found any detailed mechanization description.

 

Good points!

 

Because of the description of the CBU-103 (that it's simply a CBU-87 fitted with an additional guidance kit), I always assumed it would start spinning right after release.

 

Now I'm not so sure any longer. TBH, I'm beginning to question my assumption that the CBU-87 begins to spin right after release. I always thought that's how it works, but I'm not sure at what point exactly the canister starts to spin up to the desired RPMs.

Link to comment
Share on other sites

CBU-87 can be time or proximity fuzed so I can't think that it would know when to spin up "just in time". Besides, spin is more stable in flight so earlier is better. It should just be an adjustable set cant in the fin that begins spinning when fins extend when lanyard pulled on separation.

 

The more I think of WCMD/103 the more it has to spin up for terminal but otherwise straight. The actuator power and movement rate to keep updating over 100 times per second as each fin would have to change its job every 90 degrees of rotation would be intense.

Link to comment
Share on other sites

  • 3 years later...
9 hours ago, gmangnall said:

I have just done a video on how to STOP the SFW being so effective against static targets

This is neat and sad at the same time.

Neat to have the AI react in a more realistic way (ignoring that 12 Tanks in the open is somewhat "gamey" to begin with), sad because you need like a gazillion triggers to make it so.

Also, I think the altitude in the ME Triggers is in meters, not feet.

 

  • Like 1

52d_Sig_Pic3.png

Link to comment
Share on other sites

Yeah - lining 12 tanks up is just for demonstration purposes. Should have checked on the metres vs feet...but as I mentioned the numbers I used are again just demonstrating the principle and you should use your own.  Ideally I would have used one of the in game functions like I do in part 2 (IsTargetDetected) but bizarrely thats limited to 3 miles for visual and optical. As for the triggers you can reduce that as I had triggers for messages and could have used "time since trigger"....but you are right...this should be part of the core functionality and not relying on fudges and triggers.

Link to comment
Share on other sites

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...