[REPORTED]A-10C II - JDAM/LJDAM Range Staple and CEP Issues (DCS 2.5.6.57264)

[SJBMX]

JDAM/LJDAM DLZ Staple:

 

The DLZ Staple for GBU-38 JDAM and GBU-54 LJDAM indicates a significantly longer range than the bombs are actually capable of. In the below example, the staple indicates that you are within the launch zone at around 7.8nm when at 20,000ft, for a target near sea level, for both types of bombs. However, actually releasing from this range results in the JDAM/LJDAMs falling approximately 3/4 of a mile short of the target, as shown in the video and image below. The actual maximum range from this altitude seems to be somewhere between 5.5 and 6.0nm, from what I've seen.

 

 

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JDAM/LJDAM CEP:

 

The DCS 2.5.6.57624 patch notes indicate that the Circular Error Probable (CEP) for the GBU-38/54 is 5m (16ft) when GPS-guided, and 5 times that (25m/80ft) when inertially-guided; from my understanding, CEP means that there is a 50% probability of impact within the given radius, with increasingly lower potential for further misses (ie: bombs not landing within the CEP radius are more likely to land nearer to the target than further from it). From what I've seen, GBU-54s dropped within a reasonable range will always hit within 15m of the target, which seems somewhat reasonable (after all, there's only a 50% chance of them landing within the 5m CEP radius), but GBU-38s are considerably less accurate from what I've seen. I probably released 40 of each yesterday, and the GBU-38s consistently underperformed compared to the the GBU-54s, in some cases being off enough to miss small buildings.

 

Both bombs in the example image below were dropped from 10,000ft and 3.5nm on a steerpoint set at the center of the target and at the ground elevation, without wind conditions or modified altimeter setting. For reference, the tank pictured is approximately 10m in length. The GBU-38 landed approximately >30m from the target and the GBU-54 landed about 15m from the target location (both bombs overshot - the GBU-38 was pickled from the opposite direction). The GBU-54 in particular was observed to make an erratic last second correction that resulted in the overshoot.

 

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Edited November 5, 2020 by SJBMX

[Ryuk99]

Can agree on the CEP Part, GBU 38 and GBU 31 JDAMS are way off in the F/A-18C too

[BIGNEWY]

Hi

 

we will check, but please include a short track replay when reporting issues.

 

thank you

[BIGNEWY]

Reported,

 

it looks like the max range cue is incorrect for drops above 20k we will have the team check it out

 

thank you

[SJBMX]

Reported

 

Thank you!

 

please include a short track replay when reporting issues.

it looks like the max range cue is incorrect for drops above 20k we will have the team check it out

 

From what I've seen, it seems to be the case for all altitudes, although the degree to which the bombs came up short at maximum range was significantly less. IIRC, I had tested it at 10,000, 7,000, and 5,000 feet. I will do a test run and add tracks ASAP.

[SJBMX]

Test #2: Tested with GBU-54 and GBU-38 at maximum DLZ range from 20,000ft, 10,000ft, and 5,000ft MSL, against a steerpointed, invulnerable target at 33ft MSL, with no wind conditions and standard barometric pressure. All bombs come up very short except for the 5,000ft GBU-38, which overshoots and impacts over 50 meters past the target. Target is approximately 10m in length for reference. Test # 2 Track File

 

Test #3: Dropped three GBU-54s and three GBU-38s from 10,000ft MSL, between 4.9 and 4.1nm horizontal distance to target. Same target and conditions as above. Three bombs come up very short, and three impact within 15m of the center of the target. Test #3 Track File

 

Test #4: Dropped GBU-54s from 10,000ft MDL at 4.5, 4.0, and 3.5nm horizontal distance to target, came around, and did the same with GBU-38s. Same target and conditions as above. All three GBU-54s and one GBU-38 impact 10-15m from center of target. One GBU-38 appears to land around 5m from center of target. One GBU-38 comes up very short. Test #4 Track File

Edited November 6, 2020 by SJBMX

[SJBMX]

Test #5: Dropped 6x GBU-54 on 6x targets from 10,000ft MSL, between 4.0nm and 3.5nm horizontal distance. All bombs impact within 15m of their respective target's center (targets are about 7m in length for reference). Test #5 Track File

[jppsx]

there a trk

a-10cii gbu falling short .trk

[jppsx]

any idea on wen it will be fixed ?

[DucS2r]

It’s funny, I can consistently hit multiple (4) targets with mark points and the GBU-31(V)1/B but not with the 3/B, or the GBU 38 or 54. And I have inconsistent results with the laser guided bombs as well, though I have not tested them as much. Mavericks are fine as are laser guided rockets.

[MrFlibbles]

Well halleluiah. I have been learning the a10C II and playing the instant action missions a lot but having constant issues with the GBU-38 on the bridge targets. I have hit it once or twice in 10+ attempts so figured I must have been screwing up something. Seems I just got lucky once or twice, the rest of the times it falls short. Sticking to about 10,000 ft currently for the drop. Thanks for reporting this.

[twistking]

i want to add that while the gbu-38 can fall short, i noticed that the gbu-54's tape shows too less range. that is when doing low toss bombing.

 

example: flying 1000 feet above ground (and target), gbu-38 will show a very long range / big tape, however if you release the bomb at the start of the tape, they will fall short. if you wait a little bit longer gbu-38s will hit. The gbu-54 on the other hand will only show a range that is smaller (shorter range) by a factor of 10 or soemthing meaning that you cannot toss-bomb with the gbu-54 at all. The range is way lower than the gbu-38 even if you release the 38 later to account for the 38s notion to fall short.

 

to test, simply fly fast and low and toggle between the 38 and 54 and notice how small the 54's tape is.

[Madone]

No GPS guided bombs should be released at 1000ft AGL, it will not arm itself, no gps signal (INS calc take even longer), will flatten impact angle and you will most likely be within the frag pattern at impact, basically it's not within the enveloppe. GPS/INS or even hybrid bombs need minimum 5000ft AGL (for laser) but if you want 90° it will usually be above 18000ft-ish! Take that with a grain of salt as it's a rule of thumb for 500 pounders. But gives you the general idea. I tested yesterday, the altitude/velocity/distance ratio seems off, it landed consistently short at 18000ft but almost overshot when releasing at 12000ft, with the A10C.

[twistking]

No GPS guided bombs should be released at 1000ft AGL, it will not arm itself, no gps signal (INS calc take even longer), will flatten impact angle and you will most likely be within the frag pattern at impact, basically it's not within the enveloppe. GPS/INS or even hybrid bombs need minimum 5000ft AGL (for laser) but if you want 90° it will usually be above 18000ft-ish! Take that with a grain of salt as it's a rule of thumb for 500 pounders. But gives you the general idea. I tested yesterday, the altitude/velocity/distance ratio seems off, it landed consistently short at 18000ft but almost overshot when releasing at 12000ft, with the A10C.

yes, but i was talking specifically about toss bombing.

 

also it should still show a correct tape. my argument was msotly that 38's tape and 54's tape differ significantly.

[Belisarius]

Very glad I checked here..been going crazy with this past few days.

anything gps guided way off, lasers no problem

[EasyEB]

I’ve noted problems when releasing in the near end of release paremiters. It’s like the bomb does not account for having to take a steeper dive in a late release and struggles to pitch down in the end of its guidance stage because it overflew in the early stages.

[DucS2r]

On 11/20/2020 at 7:26 PM, DucS2r said:

It’s funny, I can consistently hit multiple (4) targets with mark points and the GBU-31(V)1/B but not with the 3/B, or the GBU 38 or 54. And I have inconsistent results with the laser guided bombs as well, though I have not tested them as much. Mavericks are fine as are laser guided rockets.

It wasn’t mentioned in the 12-17 patch but I was still hoping this had been fixed. Unfortunately it is the same. Solid hits with the GBU 31(V)1/B and misses with the GBU 38 with one falling way short. I didn’t try the 54. Figured it would be the same. 

[EasyEB]

Yeah I experience exactly the same.

[SJBMX]

Any updates on if fixes to the range and accuracy issues are being actively worked on, BN?

Edited December 18, 2020 by SJBMX

[EasyEB]

I’ve also noticed a quite big change to the GBU-12 CEP, they can now miss by quite alot even on stationary targets. They frequently miss by alot more than the advertised 1.1 meters.

[yoevro]

this is kind of a serious problem for the a-10. hope this gets the attention it deserves.

[-Condor-]

Good Evening,

 

Firstly, Congratulations on the A10C II. Love it!. I searched and couldn't find find any previously reported A10C II topics on this.

 

Secondly, down to business. I have attached two track files employing the GBU31. The bomb clearly misses its intended target. SPI set to target  for GPS co-ordinates and manual release in CCRP mode when advised on the HUD. Bomb seems to overfly and correct. Two files with similar outcomes. I hope this helps.

 

Look forward to your comments on something I may be doing wrong.

 

Happy New Year!

GBU31 Inaccuracy B.trk GBU31 Inaccuracy.trk

[SJBMX]

https://forums.eagle.ru/topic/252217-reporteda-10c-ii-jdamljdam-range-staple-and-cep-issues-dcs-25657264/?do=getNewComment

[-Condor-]

Thank you