[AS INTEDNED] JDAMs strange behaviour

[flo57100]

Hi harrier pilots !

 

A strange behaviou I noticed regarding JDAMs. Happened when releasing bombs in pre-planned and in TOO (single bomb and ripple relase in both modes):

 

- When releasing bombs from 25000 feet on pre-planned targets or targets I marked as markpoints with TPOD, no problem, fly in the circle, pickle, pickle, pickle, pickle, 4 bombs gone, 4 targets destroyed

 

- When releasing from 30000-35000 feet: bombs are overshooting over the targets, acts somehow like "waking up" when over objectives, pull like crazy when passing over (some kind of "bomb split S"), and of course miss, see youtube vidéo:

 

 

Could someone explain this ? I first thought air density (or lack of) at this altitude might trigger a poor JDAMs control surfaces response, but in that case they might fall too short, not overflying targets ?

 

[RAZBAM_ELMO]

Which JDAM. 38, 32 or 54?

[flo57100]

Hello Elmo,

 

I tried and noticed that strange behaviour with GBU-38. I will try with other jdam tomorrow morning and will post the test result

[Kappa]

Which JDAM. 38, 32 or 54?

 

did you watch the video he posted?

HUD shows J82 and F6 view shows the flight of multiple GBU-38

 

however in my opinion, even the GBU-54s have a strange flight path. They tend to fly over the target and then fall on it almost vertically.

[flo57100]

Hello again, I did quick tests before going to work:

 

- GBU-38: see initial post with the video. Strange behaviour when dropped from 35000ft, miss targets even 100% hit probability. However, hit all targets when dropped from 25000ft with 15% hit probability

 

- GBU-32: always fall miles too short when dropped from 35000ft even with 100% hit probability. When dropped from 25000, always fall miles too short if not released between 90-100% hit probability.

 

- GBU-54: Same as GBU-38

[Vakarian]

@flo57100 If by hit probability you mean that countdown you see on a HUD, that is not a hit probability.

 

Currently when flying from the outer ring of the LAR to the inner ring, you will see the countdown go like this: 0 (outer ring) -> 100 - >0 (middle of the LAR) -> 100 -> 0 (inner ring), so I really don't know what is that supposed to represent

I found that releasing JDAMs when the unwinding thingy on the HUD is somewhere between 9 and 6 o'clock, that gives best result. If you don't want to use that as a reference, then drop them when you are in the middle of the LAR by referencing EHSD

[RAZBAM_ELMO]

I will look into this later today. Feel free to stop in the RAZBAM discord if you want to have a look. alternatively I will also stream my tests on twitch elmo_the_punisher

 

[ChickenSim]

Currently when flying from the outer ring of the LAR to the inner ring, you will see the countdown go like this: 0 (outer ring) -> 100 - >0 (middle of the LAR) -> 100 -> 0 (inner ring), so I really don't know what is that supposed to represent

 

The numbers are supposed to represent how close you are to the center or heart of the computed LAR based on current aircraft position relative the target.

 

I'm not sure how they're coded to behave right now either, but they definitely shouldn't be counting up and down like that. It is probably best to ignore them altogether and go strictly off the NIRD in the HUD and your best intuition from the EHSD (since those LARs on the EHSD aren't accurate and don't give you any valuable information either).

[RAZBAM_ELMO]

Hello Elmo,

 

I tried and noticed that strange behaviour with GBU-38. I will try with other jdam tomorrow morning and will post the test result

 

I have tested this thoroughly with all GPS bombs. I have been able to get hits 100% of the time. My conclusion here is that you are either too slow ( below 500 indicated), too far out in the LAR ring releasing in the first 0-100 range, or a combination of the two. If you can try adjusting your methods as I have described here. I will leave this here until you can confirm that adjusting speed has rectified the issue.

[Wesjet]

@RAZBAM_ELMOI just wanted to add that I was doing some tests with @NeedzWD40today where I flew a Hornet and he flew the Harrier, line abreast formation attacking the same targets with GBU-32's. We have noticed that when the Harrier finishes counting up to 100, you are still slightly outside of the max range LAR for the Hornet and the difference can vary with speeds and altitude on how far outside that is. Test was conducted at 34,000ft and Mach 0.77.

 

On the short range end of the stick, if the Harrier releases close to the second zero at the end of the count down then you will pretty well get the bomb S curve. At this point the Hornet is inside of the IZLAR and closing in on the minimum launch range, but the Hornet's bomb does not do the S curve and seems to dive a bit sooner. This was done from 20,000ft and Mach 0.70.

 

In any event, the cues do not match up with the Hornet under the same release conditions.

I thought this would be worth mentioning, in case it may help.

[RAZBAM_ELMO]

The logic and symbology for the LARs right now is a stand in until we can create an elliptical zone. As for any other issues im struggling to see what the bug here is. If that cannot be identified then Ill move it to resolved.  

[RAZBAM_ELMO]

I was able to get all hits with 10 bombs

GBUall hitsTOO.trk

[Shep 2001]

On 11/22/2020 at 3:08 AM, flo57100 said:

Hi harrier pilots !

 

A strange behaviou I noticed regarding JDAMs. Happened when releasing bombs in pre-planned and in TOO (single bomb and ripple relase in both modes):

 

- When releasing bombs from 25000 feet on pre-planned targets or targets I marked as markpoints with TPOD, no problem, fly in the circle, pickle, pickle, pickle, pickle, 4 bombs gone, 4 targets destroyed

 

- When releasing from 30000-35000 feet: bombs are overshooting over the targets, acts somehow like "waking up" when over objectives, pull like crazy when passing over (some kind of "bomb split S"), and of course miss, see youtube vidéo:

 

 

 

Could someone explain this ? I first thought air density (or lack of) at this altitude might trigger a poor JDAMs control surfaces response, but in that case they might fall too short, not overflying targets ?

 

Similar issue encounters in PP mode. First hit 10 out of 10 targets from lower altitude. Then similar mission but above 32000 ft. 10 out of 10 missed, looked like all overshot. Targets did not move.

[RAZBAM_ELMO]

Still cannot reproduce. JDAM lar and range symbology is changing however to better indicate release params. Marking AS INTENDED and moving to RESOLVED.