CBU-97: Height of Function and target altitude "issues"...

[Bahger]

I set my CBU-97s to deploy at 1200 ft but got a suspiciously low number of hits from a good drop, combined with an oddly early report of the few hits I did credited with. This has occurred a couple of times in the same mission and to more than one pilot who is pretty competent with CCIP bombing. We each ran in from Angels 10 and were baffled by the results.

 

We think it's to do with target altitude in the CDU and will replay the mission making sure DTS (is that what it is, I'm not near the sim, or the manual) is set in the HUD for WP altitude. But, regardless, surely HOF is set by a radar altimiter in the weapon and is therefore not dependent on MSL target altitude settings, or am I wrong about this?

 

Anyway, there appears to be some anomaly --user-created, no doubt -- in the way CBU HOF is operating in these circumstances. The 97s are either deploying too early and therefore spreading too widely for optimal effect or -- this being my hunch -- too late, possibly even not at all, and the only hit I'm getting is from a direct impact of the undeployed bomb! Can anyone comment??

[GGTharos]

Your HOF is too high.

[Fishbot]

Is the HOF relative to ground (presumably) or is it absolute? A more dumb question how do you change it anyway and what is the "optimum" above ground HOF?

 

Ta, Andy.

[zamboni]

I dunno how accurate the HOF is, but I have only used (so far) either 500 or 700 ft. Based on the results I have gotten with the 700ft, I really don't think I would want to set it any higher. I have never changed the spin settings on it either.

 

I have a feeling you will have to tweak the spin settings along with the burst height to get coverage that is satisfactory.

 

Another thing to remember is, that I get widely different burst patterns if I am doing a CCRP delivery from about 15K, compared to a CCIP run. You also have to remember that you will get a more concentrated hit with a CCRP at 15K because the bomb is going to be more vertical. On a 20-30 degree CCIP run, the bomb spread will be elongated along the fall line to have more of an elliptical pattern.

 

Probably the only way to be sure if things look like they are operating correctly is to see if there are published specs on CBU spread with X burst height and Y spin rate and compare it to what you get in the sim. I personally think that 1200ft HOF is just way to high to get any type of puck concentration over your target, and they are being even more dispersed by the angle you are dropping them in your CCIP delivery.

[Phuz]

Try holding your weapon a touch longer with each higher HOF setting.

 

In my testing it seems that the CCIP recticle may be off [short] when it comes to higher CBU HOF settings.

 

Try 300 HOF at recticle on a fixed point and check result using external views.

 

Try 700, 1200, 1500, 3000 each time deploying the weapon further and further after the ccip recticle passes the target and I think you will experience better results. This has been working consistently for me.

[nomdeplume]

Is the HOF relative to ground (presumably) or is it absolute?

Relative to the ground. There aren't enough options for it to be MSL/'absolute'.

 

A more dumb question how do you change it anyway and what is the "optimum" above ground HOF?

You change it through the DSMS inventory page (not the profile page). The optimum setting depends on what you're attacking. Basically, a higher HOF results in a wider area being affected, but at a lower density (each submunition is further apart). A lower HOF will result in a smaller but denser area being exploded.

 

Ideally you want the coverage area to match the spread of the targets, and if the area you need to cover is large you'll need to drop additional CBUs in order to maintain bomblet density.

 

Bear in mind that your speed and release altitude also affect the resultant spread of the submunitions (as mentioned above), so there's quite a few parameters at play.

 

One simple option is to set a low HOF and just treat it like a simple bomb with a really large blast radius. That's pretty much what the AI does.