reported Pop Up Attacks and JDAMs

[Whiskey11]

Greetings ED and team, I come to you with a bug which may or may not have been reported.  Didn't see a post for it.

One of my favorite routines for addressing high threat SAM's like the SA-10 are pop up attacks using GBU-38's.  Nothing like a high adrenaline low altitude rush, followed by a pop up attack to get the SAM operator's asleep at their stations!!

The problem comes from lofting GBU-38's and GBU-31's.  The JDAM launch zone indicators do not accurately represent the weapon energy potential.  Specifically, when performing these bomb tosses, the weapon release staple shows you are within parameters for a weapon release and the weapon will come off the station, however it will fall VERY short if launched at the upper end of the staple.  These weapons are being launched with the default profiles in the SMS page and in PRE mode.

CBU-105's don't seem impacted by this.

Track files and Tacviews attached.  In both the GBU-38 and GBU-31 cases, the first bomb is released just under the top of the staple.  The next bomb is released with 2,000 feet more altitude.  Aircraft speed is around Mach .9 to Mach 1 at release.  Altitude is usually around 6k feet on first release and about 25 degrees nose up pitch.  Range is between 12nmi and 14nmi.

Computer Specs:
9900k OC'd to 5GHz
32gb DDR4 3400MHz
3090Ti
DCS Installed on NVME SSD
Reverb G2
TM Warthog
TM TPR

Running the latest OpenBeta

GBU-31Toss.acmi GBU-38Toss.acmi GBU-31Toss.trk GBU-38Toss.trk

[Nealius]

I use similar tactics and was curious about this as well. I don't recall getting a toss anticipation cue with the JDAMs, nor can I find a release angle setting in the SMS page. I've been having to release manually at x-nm from the target from trial and error. 

[777coletrain]

17 hours ago, Nealius said:

I don't recall getting a toss anticipation cue with the JDAMs

I'm not sure about this, but I think that stuff is only for dumb bombs. I have been having the same problem also though

[Frederf]

All the toss and CCRP stuff is for non-IAMs. IAMs (JSOW/WCMD/JDAM) get their own stuff called IAM VIS, IAM PRE, and IAM MPPRE. Paveway III gets its own special mode which is kinda in between.

You should be able to launch have have terminal criteria (zone 1 or 2) with JDAM given the display says you're in LAR1 or LAR2. In reality predictive power of launch region suffers in low environment so it's best to preplan that. Display only reflects current conditions so for genuine toss deliveries with JDAM you'd have to do the whole thing preplanned style.

[BIGNEWY]

Hi, 

as mentioned above by Frederf toss is not for IAMs. 

thanks

[Whiskey11]

19 hours ago, Frederf said:

All the toss and CCRP stuff is for non-IAMs. IAMs (JSOW/WCMD/JDAM) get their own stuff called IAM VIS, IAM PRE, and IAM MPPRE. Paveway III gets its own special mode which is kinda in between.

You should be able to launch have have terminal criteria (zone 1 or 2) with JDAM given the display says you're in LAR1 or LAR2. In reality predictive power of launch region suffers in low environment so it's best to preplan that. Display only reflects current conditions so for genuine toss deliveries with JDAM you'd have to do the whole thing preplanned style.

I'm not trying to force this into a dive toss mode... I'm merely pointing out the in range staple is incorrect when lofting JDAMs in popup attacks in PRE mode.  I find it really difficult to believe the Fire Control Computer in the F-16 can calculate the correct loft geometry for a dumb bomb but suddenly loses that ability with a guided munition using the same bomb body and guidance fins.    

Ironically enough, the CBU-105 does not suffer from this issue and the staple on the HUD is correct when lofting in nearly the same exact scenarios in spite of being significantly more draggy.

Edited September 22, 2022 by Whiskey11

[toilet2000]

2 minutes ago, Whiskey11 said:

I'm not trying to force this into a dive toss mode... I'm merely pointing out the in range staple is incorrect when lofting JDAMs in popup attacks in PRE mode.  I find it really difficult to believe the Fire Control Computer in the F-16 can calculate the correct loft geometry for a dumb bomb but suddenly loses that ability with a guided munition using the same bomb body and guidance fins.    

Ironically enough, the CBU-105 does not suffer from this issue and the staple on the HUD is correct when lofting in nearly the same exact scenarios in spite of being significantly more draggy.

 

As Fredef said, there are modes (not implemented) for LARs, but assuming that because a dumb bomb can be tossed at a certain range a similar logic applies to a guided munition is very wrong.

Control surfaces makes the bomb not follow a ballistic trajectory, and every correction has an impact on drag which slows down the bomb and waste energy. Definitely not as simple as an unguided munition.

[Whiskey11]

10 minutes ago, toilet2000 said:

assuming that because a dumb bomb can be tossed at a certain range a similar logic applies to a guided munition is very wrong.

Control surfaces makes the bomb not follow a ballistic trajectory, and every correction has an impact on drag which slows down the bomb and waste energy. Definitely not as simple as an unguided munition.

The assumption isn't that a JDAM can be lofted to the same range as a dumb bomb.  The assumption is the computer knows the impact point, it knows the flight profile (otherwise how would we have a LAR to begin with?) and it knows your own aircraft's metrics... it absolutely can calculate the max acceptable launch range given the parameters available to it at the time of release.  That's the point of CCRP bombing.  JDAM and other GPS guided weapons have an advantage in that you can launch those at a much wider array of ranges due to having the ability to guide, but the Staple being flat incorrect on the HUD is the issue.  It's not even giving the correct LAR AT ALL, to the point of being over 1.5nmi wrong, in a loft situation.  In reality though, the issue is that the staple is so wrong, that even drops well within the staple (such as the second released JDAM) still fall well short in spite of being well within the staple...

An issue which IS NOT present when lofting a CBU-105, another GPS guided weapon... for some reason.

Edited September 22, 2022 by Whiskey11

[Nealius]

CBU-105s are IAMs. They, according to OP (I haven't yet tested myself), has the "toss stuff." 

If all IAMs are not supposed to have "toss stuff," then why do the -105s have it? 

[Whiskey11]

12 minutes ago, Nealius said:

CBU-105s are IAMs. They, according to OP (I haven't yet tested myself), has the "toss stuff." 

If all IAMs are not supposed to have "toss stuff," then why do the -105s have it? 

The CBU-105 responds correctly to the staple.  Launches at the top of the staple achieve consistent hits, although I generally wait until I'm well within on the CBU-105.  I generally DO with the GBU-38 as well, but that's not the point of this thread!

I've attached a Tacview of the CBU-105 launched at the top of the staple on the same test miz.  I didn't save the track file unfortunately.  I guess I could go and get one if one is really necessary for the CBU-105 working correctly and the GBU-38 not.

Tacview-20220920-142214-DCS-testSEAD.zip.acmi

[777coletrain]

I just did some testing, dropped one from straight and level and another with the FPM 6-7 degrees up. The straight and level bomb hit the mark point, where the "tossed" bomb fell way short. It's amazing how much of an impact that has

Straight and Level.acmi 6 degrees nose up.acmi F16 JDAM 9 22 22.trk F16 JDAM2 9 22 22.trk

[llOPPOTATOll]

The JDAMs are just not implemented correctly. There should be 2 LARs, one for a LOFT and one for a level release. This is what the JDAM DLZ should look like

Edited September 23, 2022 by llOPPOTATOll

[Ignition]

Fly around mach 1 at 200-300ft, for a GBU-38 at around 9nm I believe it will be at maximum range, pull up to 20º and it will be at around 80% of LAR. It will fly with enough energy.

[Nealius]

3 hours ago, 777coletrain said:

I just did some testing, dropped one from straight and level and another with the FPM 6-7 degrees up. The straight and level bomb hit the mark point, where the "tossed" bomb fell way short. It's amazing how much of an impact that has

I need to do some more testing, but there may or may not be a wider issue in general with the GBU38 accuracy even with level deliveries. My first bomb released always hits dead on. My second bomb released always misses by about 8m (usually short). I noticed this observation jives with yours on the second bomb falling short, except in my case it was a level delivery. I'll need to test to rule that out.

[777coletrain]

I do remember that being a problem but I think this is separate. I think this is about the LAR when you aren't straight and level. The testing I did yesterday shows that pitching up 5 degrees extends the max range of the LAR by 3nm causing the bomb to fall 4nm short of the target. If there should be 2 LARs I'm kind of surprised this thread is marked as correct as is. 

[WHOGX5]

On 9/23/2022 at 8:01 PM, 777coletrain said:

I do remember that being a problem but I think this is separate. I think this is about the LAR when you aren't straight and level. The testing I did yesterday shows that pitching up 5 degrees extends the max range of the LAR by 3nm causing the bomb to fall 4nm short of the target. If there should be 2 LARs I'm kind of surprised this thread is marked as correct as is. 

I've experienced the same exact issue with GBU-31s when I've tried to loft them. I haven't used JSOWs since release as they're absolutely useless in DCS and does no damage to anything but unarmored trucks, but from what I recall I had the same guidance issues with those as well. If you try lofting them they'll fly a very strange trajectory and not impact anywhere near their target.

[Whiskey11]

On 9/22/2022 at 2:52 AM, BIGNEWY said:

Hi, 

as mentioned above by Frederf toss is not for IAMs. 

thanks

Hey BIGNEWY, there hasn't been any replies to any of the new evidence presented here.  Understand, we are not talking about DTOSS, but lofting GBU-38's and GBU-31's and the DLZ showing in range, but not actually being in range.  Can you please reexamine the new posts?  Thanks!

[NineLine]

On 9/22/2022 at 5:32 PM, llOPPOTATOll said:

The JDAMs are just not implemented correctly. There should be 2 LARs, one for a LOFT and one for a level release. This is what the JDAM DLZ should look like

 

PM what reference you have on this.

[Moonshine]

59 minutes ago, NineLine said:

PM what reference you have on this.

sent you a DM

[NineLine]

Thanks @Moonshine, I will review with the team.

[NineLine]

Ok guys, this isn't a bug, but rather a feature that hasn't been implemented, so right now I am moving it to wishlist, and it may be done at a later time. Thanks all!