KAB-500Kr optical guided bomb is unaffected by gravity

[Shark-Bait]

DCS: World KAB-500Kr bug v1.2.10.32582

 

KAB-500Kr optical guided bomb is unaffected by gravity and decelerates as it falls.

[Aginor]

Yeah, there's something borked with the bombs that still have SFM. Same with the GBU-38 for example.

[effte]

While that does not seem right, bombs do tend to decelerate somewhat as they fall into increasingly dense layers of the atmosphere.

 

Wasn't the F10 speed indication the horizontal component of TAS, or some such peculiarity, at one time? I seem to recall that from the "P-51D speed dive thread". Doesn't appear to be the case anymore anyway. :)

 

Cheers,

/Fred

[Aginor]

Nope, not the reason, I think.

We know from publicly available data that -for example- JDAMs dropped from over 10,000ft. hit their targets with almost the speed of sound. 500 knots are no problem for low-drag bombs.

The bombs in DCSW that have AFM, like the GBU-12 behave exactly like that, they get really really fast.

The GBU-38 and other bombs that don't have AFM tend to do strange things. They sometimes even drop below 200 knots. At least they did the last time I checked. You can't explain that with dense air.

 

As for your other explanation: That should be easy to check. I'll go and drop a JDAM at minimum speed at maximum altitude and see what happens. It should almost drop vertically so we can measure the speed reasonably well.

[Aginor]

I just checked it, it is still like I remembered:

 

Mission is attached. one A-10C at 20,000ft, armed with one GBU-38 and one GBU-12

Target: Two warehouses at the small airport south of Kobuleti, near waypoint 1.

Both bombs were dropped near stall speed, with flaps fully extended at 130 knots

 

Results:

GBU-12: hit the ground at 600 knots, accelerating

GBU-38: hit the ground at 200 knots, decelerating

 

Unfortunately my track is broken again, so you have to try the mission yourself.

 

 

EDIT:

Tried the same from 30,000 ft. Similar results. (I couldn't laser guide the GBU-12 from that altitude so it missed, but that doesn't matter, I could see its speed at least)

Both bombs end up hitting the ground almost in a 90 degrees dive.

The GBU-38 decelerates until it hits 194 knots.

The GBU-12 accelerates until ~600 knots, then the air becomes too dense so it doesn't continue accelerating. In my test it reached 610 knots.

bombtest1.miz

Edited November 1, 2014 by Aginor

[Aginor]

I just noticed (yeah, kind of embarassing) I mixed up the russian bombs. Again. The KAB-500Kr bomb the OP mentioned is something akin to the AGM-62 or GBU-15 glide bombs.

I did a quick test with some SU-30s dropping those things, and it seems they do indeed slow down, but IMO they stay in the speed range I would expect from a glide bomb in a flat trajectory.

The weapon I was talking about is the KAB-500L, which is something like the american GBU-10. And that one shows the same effect like the GBU-38 I was talking about earlier, it slows down. Same for its bigger sibling, the KAB-1500L.

The normal russian bombs of the FAB series drop significantly faster though, and they are still accelerating when they hit the target. No problem getting those to 500 knots.

 

EDIT: Tested again, from a higher altitude to get steeper trajectories. It looks kinda strange, and I think the KAB-500Kr is indeed too slow in the finaly phase. It even drops below 150 knots despite being in a 50 degrees dive.

From 20,000ft the FAB-1500 reach 600 knots. The KAB series bombs slow down to 250 knots.

Edited November 2, 2014 by Aginor

[Grimes]

Many of the guided bombs are still using an old scripted way of guiding to targets. In comparison the paveway series bombs have a custom definition with proper "bang-bang" guidance, thus react the way we expect them to. Suffice to say it is something that needs to be addressed.

[Shark-Bait]

While that does not seem right, bombs do tend to decelerate somewhat as they fall into increasingly dense layers of the atmosphere.

Hopefully the lads at ED recognize that magic decelerating bombs are not quite right. I remember an experiment one time, where a man dropped a big ball and a small ball to prove this point. (They both hit the ground around the same time.)

[Shark-Bait]

Suffice to say it is something that needs to be addressed.

Great.

 

It's not a major issue as most people don't use the bombs when they can use laser guided missiles from a longer range. But I'll post issues I find that aren't mentioned in the 'Bug' section of the forum.