Solved JSOW impact spacing when trailing
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@Ricky ok in TR#13 (Maverick training) you can repro this in daylight, fair wx … I didn’t think the wind would be strong enough to matter, just 15-20 kts out of the NW, but it does.
TR#13, change loadout from mavs to 4x jsows
first pair:
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lead/trail configuration, ~1200 ft separation, azimuth 315 degrees (headwind approach)
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release from ~20k ft and 20 nm SE of target (just inside the JIZ)
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observed: both pigs hit the ground about 1.3 nm short of the target
second pair:
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change azimuth to 135 degrees (downwind approach) and circle around to NW of target
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release pair from ~20k ft and 20 nm NW of target (just inside the JIZ)
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observed: good effect on target area, pigs detonate ~1200 ft apart, as expected
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to be clear I have no idea if this is a bug in any way, or expected behavior of the RL weapon system… it seems somewhat reasonable that GPS/inertial-guided munition wouldn’t be able to compensate much for crosswinds or headwinds along intended flight path, and might have a hard time following its expected path to reach target point
and even if it did compensate, to the extent possible… it still seems desirable to take a downwind-oriented attack azimuth, to get maximum spread when attacking a column
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I did just repro this “bug” or wind-effect with a single-jsow launch, too … but it seemed more 50/50.
maybe something about the path-computation for lead/trail is more susceptible to headwind / crosswind, than for singles or side-by-side pairs
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I wrote the JSOW code at ~2011, I just gone over it through the commit logs till this day and I don’t see a change that could ruin Tandem mode. I will try to reproduce it here and will see. Code seems same since the original implementation and I’m mostly sure it used to work fine back then. I will try to reproduce here, thanx!
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@I-Hawk Thank you! Let me know if I can help by testing any specific scenarios.
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Hello all,
Here my own test :
Re-doing the IAM-15 training mission, i can confirm that there is a bug with the JSOW trail releasing mode.
When you specify a feet spacing, the two bombs go to the long point.
You will see it in the ACMI below where i have set up a long distance separation (8000 fts) to show more the problem but even with a normal spacing (1500 - 2000 feets), the bug occurs.
My markpoint for the trail shot was the cross between the two columns.
Normally, one of the bombs must target a short point (at equi-distance of the spacing at the aim point) and one a long point. But in fact, the two go long point.
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For the side by side bombs, you can see that they respect the (big ) lateral spacing between them.Parameters of the bombs :
Alignment done / ready ROB : 6 NM AZ ANGLE : 270° EGEA : 2500 ft Spacing: 8000 ft
Here the ACMI : https://we.tl/t-7ZHxXfnEs2
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@ericfa2a thanks, I also tried this. I saw some spacing between lead and trail, but not sure it was really the input of 3k ft (hard to measure with tacview).
I also checked code, didnt see anything weird.
Im still checking, Ill keep you posted .
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@Seifer @ericfa2a There are several things to unpack, in TR#15 …and JSOW operation in general
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the target area is high elevation (about 1200 ft iirc)
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there’s a stiff breeze coming from the west… so the natural azimuth of attack is either against a headwind, or crosswind
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it’s night, cloudy… hard to see
Also, regarding JSOW operation in general … I think I’m seeing different results depending on how I “lock” the target. (a) just firing at stpt 6… (b) using FCR in GM mode to slew crosshairs over the column… ( c) actually hard-locking a unit with FCR… (d) using TGP through a break in the clouds
I put “lock” in quotes because there isn’t any obvious feedback moving the SPI around. It’s just always instantly “RDY” which seems a little sus.
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@airtex2019 and @ericfa2a can you test something for me?
In 3d, open chat window and type:
.priorityfix -JSOW_EGEA
Then run the IAM using trailing JSOW and report back. This will disable a fix I made last year about wrong JSOW EGEA computation. I just want to make sure it is or it is not related.
To test with the fix again, type (or simply restart falcon):
.priorityfix +JSOW_EGEA
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@Seifer , Hi ! Thanks you very much !
I Have tested with your “fix” but the bug still occurs. But it seems that there is more kills with the bombs
Edit: after typing your instruction, i had a message of “modified 114 bits” i think, something like that…Here a screen shot of the ACMI with my comments to be sure we are talking about the same thing.
I have set up a 4000 ft spacing for this try. So, according to the manual, one bomb at 2000ft after the aiming point and one bomb at 2000 ft before the aiming point. But no, the two aims for the long point :
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Some news. I wrote some unit tests where I test different situations and call the spacing code.
I still have not found anything which indicates a wrong tandem spacing computation. Bit I did found one special case in SxS configuration that is yielding wrong results (almost 0 spacing) . So it could be that we have a similar situation in tandem that I have not found yet.
I’ll keep you posted.
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@Seifer you may be on to something… it’s so hard to reliably repro, because so many factors at play… it seems like tiny changes in initial conditions result in very different weapon flights. but I’ve narrowed down my repro steps in some detail, in case it helps…
- 2d:
- TR#15, recon and set precision target-steerpoint on the low-blow radar at ppt 56
- 3d:
- wingman: RTB to eliminate distractions
- power on JSOW and wait for alignment complete, before fiddling with any weapon config
- continue north from stpt 4, fly to point roughly 30 mi east of ppt 56
- configure weapon: lead/trail pair, spacing 3000 ft, azimuth 270
- select precision stpt 99
- attack from the east; roughly FL 240, M 0.65
- launch pair when within JIZ … roughly 2:30 to 2:45 on the clock (16 to 19 nm range)
- notes: target elev is ~1500 ft; crosswind 20 kts from the south
- observed (sometimes): both jsow fall short of target, hit ground about 1-2 miles east
- observed (sometimes): both jsow follow same path into the ground, 1500 ft west of target
The difference in the two outcomes seems to be somewhere between launching at 19 nm (both wpns fall way short) and 16 nm (both fly to the “far” impact point, with no spacing)
The crosswind seems to be a factor… in that I can’t repro with azimuth=360 (gliding downwind)… trying both far (18-19 nm) and near (15-16 nm), the weapons arrive with correct spacing.
And yet, the crosswind issue seems not solely specific to the pair-spacing issue, in that it affects even single jsows dropped at 19nm.
That’s all I’ve been able to gather. Hopefully, with repro steps you, can hit a breakpoint and see what’s going on inside.
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To confirm @airtex2019
Here the training TE but this time I choose to strike the 360° column with the trail bombing method instead of the side by side and … and … tada :
The spacing and the short and long point are respected !!!
I am with you with all my heart BMS Team !!
Ah… the code development and its mysteries !! -
Thanks @ericfa2a and @airtex2019 for the help. I believe the issue is fixed for next version.
For now, as a workaround, avoid 0 azimuth in SxS and 270 in tandem configuration.
It is possible there are other values, which will also be fixed in next version. But if you find any other, let me know.
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@Seifer you rock, sir. what an amazingly narrow, hard to find bug!
Is it 0 or 360 that is problematic?
(I think 0 means fly directly to target… 360 means attack from south to north.)
I can imagine how some trig code could get tripped up dealing with that special case…
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@airtex2019 said in JSOW impact spacing when trailing:
@Seifer you rock, sir. what an amazingly narrow, hard to find bug!
Is it 0 or 360 that is problematic?
(I think 0 means fly directly to target… 360 means attack from south to north.)
I can imagine how some trig code could get tripped up dealing with that special case…
No doubt he rocks
/me Looking back at 11-12 years younger self with anger - Why you had to do it more complicated??
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@airtex2019 thanks for the kind words, but the devs who really rock are the ones that make up the cool features. Even if sometimes they overcomplicate the solution
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@Seifer said in JSOW impact spacing when trailing:
Thanks @ericfa2a and @airtex2019 for the help. I believe the issue is fixed for next version.
For now, as a workaround, avoid 0 azimuth in SxS and 270 in tandem configuration.
It is possible there are other values, which will also be fixed in next version. But if you find any other, let me know.
Great job on the workaround.( Gotta love the workarounds ) So, since 0 would seeming be the “default” setting for most Ops, would you say that if you choose to attack SXS, you would need to go into the Control page and enter a course, perhaps simply your jet’s approach course?
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@drtbkj yes
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