JDAMs Impacting Short... Help?

[Stearmandriver]

For some reason, I'm having a recurrent problem with JDAMs impacting short - very short, not just a few feet.  Maybe a half mile.  I assume I must be doing something wrong here.  This happens in a pop-up type attack, but also in level flight at high altitude.  I had it happen tonight at 30,000ft and I intentionally waited about 10 seconds after I got the In Zone indication, and they still went short.

 

I've attached a short track of a test I conducted where it happened.  I do a few 360s waiting for the bombs to align, designate a waypoint as a target, then make a level delivery from about 20,000ft, pickling when I get the In Zone.  Bomb goes pretty short.  Could anyone take a look and tell me if I've done something wrong?  Thanks...

JDAM_short.trk

[Drac]

May be related to this: [ED ISSUE] JDAMs not working - Resolved Bugs - ED Forums (eagle.ru)

 

[Stearmandriver]

Man, my forum search skills must suck.  This is the second time recently I've mentioned a previously reported bug.  Thanks for the heads up though, that sounds right. 

[imacken]

Hmm, pretty sure the problem you have in the track was down to flying at too slow a speed.  I took over after you had set up, gained speed and it all works perfectly.  See attached track.

(BTW, what were all these turns for?  Getting further and further away from the max range.  I now a little time is required for the weapon to countdown, but...)

JDAM_short IM.trk

[Stearmandriver]

They were for watching my buddy doing something on his stream lol. 

 

Does speed matter?  Sure higher speed = better range, but shouldn't the In Zone indication be dynamically calculated based on current parameters?  That's why it expands rapidly to meet you if you accelerate or climb, right?

 

I think Drac is on to something.  I have to watch this track again to see if I release above 20k, but I know the problems I had in the mission were well above that. 

[Hardcard]

If you want accuracy, switch to laser-guided weapons or JSOWs.

 

JDAMs aren't reliable, regardless of launch parameters.

[imacken]

1 hour ago, Stearmandriver said:

They were for watching my buddy doing something on his stream lol. 

 

Does speed matter?  Sure higher speed = better range, but shouldn't the In Zone indication be dynamically calculated based on current parameters?  That's why it expands rapidly to meet you if you accelerate or climb, right?

 

I think Drac is on to something.  I have to watch this track again to see if I release above 20k, but I know the problems I had in the mission were well above that. 

Yes, it does matter. Did you watch my track?

[Stearmandriver]

1 hour ago, Hardcard said:

If you want accuracy, switch to laser-guided weapons or JSOWs.

 

JDAMs aren't reliable, regardless of launch parameters.

To clarify, you're talking in DCS, right?  In reality, don't JDAMs and JSOWs use the same guidance package, just with different flight parameters?

 

The goal in this particular use case was to attack SAM sites from high altitude, at the edge of their range, with a weapon they wouldn't shoot down.  They'll shoot down JSOWs but not JDAMs. 

 

From a couple quick tests, I think Drac nailed it with that bug report.  JDAMs dropped above 20k are inaccurate.  JDAMs dropped below that (excepting low-level hard pop-up type attacks) seem to be.  

[Stearmandriver]

6 minutes ago, imacken said:

Yes, it does matter. Did you watch my track?

I just did, thanks for testing it out.

 

I note that you dropped well below the 20,000ft altitude ceiling mentioned in Drac's bug report, and also, you dropped WELL in zone - almost at min range in fact. My goal was to drop them near max range, and bug out.

 

Sure I'd be faster in a mission scenario vs that test (I was in fact, and they all missed, which is what spurred this question  ), but to clarify: why do you think speed matters?  That In Zone indication is being dynamically computed based on your current flight conditions, isn't it?

[imacken]

OK, so I just can't reproduce your issue.

I tried the same track at high speed just at boundary of zone, low speed, altitude 22,000, etc. and every time there was no issue with hitting the target.

So, I don't know what is going on with you.  I was probably wrong about the speed making a difference. Thought it di, but no.

[Stearmandriver]

I did some more testing last night, against 6 targets.  I found that PP mode is more accurate than TOO, and if released above 20,000ft neither method is reliably accurate. 

 

So, the answer for now seems to be to use PP mode and keep the release under 20k, which is tactically limiting but seems to be the most reliable combination. 

 

To be clear, when I talk about accuracy I'm not griping about the expected difference in accuracy between GPS and laser guided bombs. These aren't near misses, they're off by hundreds or thousands of feet. 

[Swift.]

Just to clarify, are you guys launching in the IN RNG or the IN ZONE, because there is a bug right now where the IN ZONE is extending beyond the IN RNG so one or both are being calculated wrong. I'm just curious what the failure modes are here.

[Stearmandriver]

57 minutes ago, Swiftwin9s said:

Just to clarify, are you guys launching in the IN RNG or the IN ZONE, because there is a bug right now where the IN ZONE is extending beyond the IN RNG so one or both are being calculated wrong. I'm just curious what the failure modes are here.

I'm launching at the first indication of In Zone.  Sometimes I see In Range flicker before it changes to In Zone, and sometimes it seems to go immediately from the TMR countdown to In Zone.

 

Are you saying if I wait, the indication might change from In Zone to In Range and then BACK to In Zone?

[Swift.]

18 minutes ago, Stearmandriver said:

I'm launching at the first indication of In Zone.  Sometimes I see In Range flicker before it changes to In Zone, and sometimes it seems to go immediately from the TMR countdown to In Zone.

 

Are you saying if I wait, the indication might change from In Zone to In Range and then BACK to In Zone?

Potentially, it's this report I'm referring to:
 

As you can see, there's some funky stuff going on.

[Hardcard]

On 1/16/2021 at 1:20 AM, Stearmandriver said:

To clarify, you're talking in DCS, right?

 

Why would I be talking about real JDAMs? 

 

 

On 1/16/2021 at 1:20 AM, Stearmandriver said:

The goal in this particular use case was to attack SAM sites from high altitude, at the edge of their range, with a weapon they wouldn't shoot down.

 

Ideally you should be using HARMs for that, but if they get intercepted, use walleyes instead. 

 

I repeat, JDAMs in DCS are very unreliable, they're a waste of pylon space in most cases (specially GBU-38s), they'll miss the target half of the time (if you're lucky).

[Swift.]

17 hours ago, Hardcard said:

I repeat, JDAMs in DCS are very unreliable, they're a waste of pylon space in most cases (specially GBU-38s), they'll miss the target half of the time (if you're lucky).

Now that's a vast sweeping statement that I find hard to believe. It was not 2 weeks ago that I bore witness to 16 JDAMs being released in a majestic ballet of destruction onto a fuel farm and not one of them missed.

[Stearmandriver]

18 hours ago, Hardcard said:

 

Why would I be talking about real JDAMs? 

 

 

 

Ideally you should be using HARMs for that, but if they get intercepted, use walleyes instead. 

 

I repeat, JDAMs in DCS are very unreliable, they're a waste of pylon space in most cases (specially GBU-38s), they'll miss the target half of the time (if you're lucky).

My question was in regards to differences in guidance between JDAMs and JSOWs, because I believe in reality they use the same guidance package? 

 

I'm not sure why you think Walleyes would be useful in this scenario?  SAM sites in DCS will shoot down anything they consider a missile instead of a bomb.  That includes Walleyes as well as JSOWs.

 

I agree that JDAMs seem somewhat unreliable right now. 

[Frederf]

If it's anything like last I looked JDAMs are doing a suspicious flight path. They are diving down for a certain Mach number and then pitching to maintain that Mach to some end game trajectory. This caused (don't know if it was changed in intervening months) JDAMs released below this Mach number to rapidly descend for speed which dramatically reduced the available range compared to the release prediction. It was flying a sort of S path: steep-shallow-steep which is significantly different than even a Mk 80 type ballistic trajectory.