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BLU-108 and wind


Ignition
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I've been testing the CBU-105 and the BLU108 drift away of the target a lot (25kts of wind). Its supposed to do that? or it should also correct this.

Reducing the BA reduces the drift but also the area of effect consiredably.

I've noticed in the control sub-menu theres a "tgt wd" that its fixed at 0. I guess thats the target wind?

 

cbu105cauc.trk

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Posted (edited)

Being a WCMD I thought it would also compensate for the BLU-108.

Its a shame because its very umpredictable with moderate wind to the point were its not reliable enough to employ. I had good success while launching them against the wind, at least the 2 launches I've tried this way.

The "tgt wd" is really intriguing, maybe its the way to correct this.


Edited by Ignition
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IIRC the wind settings are used to calculate the WCMD dispense point, so that if the wind data are accurate, the dispensed munitions will drift over the target.

 

If the Wind Source setting is set to Pilot Entered (PI), then the manually entered TGT WD settings (bearing/speed) are used. If set to Mission Planning (MP), the DTC values are used. If set to Avionic System (SY), the avionics system measured or computed wind data will be used.

 

Just a simplified description (not copied from manual). For more info on wind quality, how the system extrapolates the wind speed etc., please refer to OFP tape M3.

 


Edited by LJQCN101
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WCMD is given wind info (in addition to other info) over 1760 interface before release. It combines given target location and wind info to calculate a dispense point. The same target location but different wind info will cause the WCMD to choose different dispense points.

 

As far as I'm aware the wind model is only the automatically calculated one which the pilot has no control over. There might be a SMS page to enter manual info for WCMD but I have not seen any evidence that it exists.

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I have noticed that it doesn't really matter since the general area usually is so big that you hit either way. Compared to the JSOW the WCMD is a blast.
You can even loft it far out. Not as far as a JSOW, but 10nm are possible.

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7 hours ago, TobiasA said:

I have noticed that it doesn't really matter since the general area usually is so big that you hit either way. Compared to the JSOW the WCMD is a blast.
You can even loft it far out. Not as far as a JSOW, but 10nm are possible.

If you see my track file the blu drift so much that they are at the edge of the area, it does matter. Its not the same to target something that its 1000ft away.

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vor 4 Minuten schrieb Ignition:

If you see my track file the blu drift so much that they are at the edge of the area, it does matter. Its not the same to target something that its 1000ft away.

25 kts are a lot of wind though.
Would be interesting what happens when one enters the wind... Do you have the exact mission? Or is it just a preset?

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Posted (edited)

Look above the track I posted. Its 25kts at 6600ft and 12kts at 33ft so at 1500ft (the default BA) would be around 17kts.

 

Open the track in the mission editor.


Edited by Ignition
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vor 18 Stunden schrieb Ignition:

Look above the track I posted. Its 25kts at 6600ft and 12kts at 33ft so at 1500ft (the default BA) would be around 17kts.

 

Open the track in the mission editor.

 

Well I didn't know that you can open track files. Good to know, thanks!
However it seems that the wind options are just not included currently...

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Question is does the WCMD use the DCS way of reporting wind direction ie where the wind is blowing to, or does it use the way the rest of the world reports wind direction ie where the wind is blowing from?

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Any menu in the airplane is going to be magnetic from wind.

 

In SMS CTRL page:

ATK AZ isn't editable.

AD isn't editable.

BA works.

SPIN is fixed 500RPM which is weird because CBU-105 doesn't spin. It uses gas bags to deploy the BLU-108s. CBU-103 spins up to dispense though.

"TGT WD" "0  0KTS" isn't editable.

"WD SOURSE" "MP" isn't editable.

 

Looks like this is WIP. Currently the wind data source is set to mission planning and that mission planning data is 0 heading, 0 speed regardless of actual wind. There should be two more sources of wind data to choose from: manual entry and automatic from the airplane. I released in a 25kt crosswind and the dispense point was not wind corrected as suspected from the 0-0 MP wind data and the SFWs impacted well downwind.

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1 hour ago, Frederf said:

Any menu in the airplane is going to be magnetic from wind.

 

In SMS CTRL page:

ATK AZ isn't editable.

AD isn't editable.

BA works.

SPIN is fixed 500RPM which is weird because CBU-105 doesn't spin. It uses gas bags to deploy the BLU-108s. CBU-103 spins up to dispense though.

"TGT WD" "0  0KTS" isn't editable.

"WD SOURSE" "MP" isn't editable.

 

Looks like this is WIP. Currently the wind data source is set to mission planning and that mission planning data is 0 heading, 0 speed regardless of actual wind. There should be two more sources of wind data to choose from: manual entry and automatic from the airplane. I released in a 25kt crosswind and the dispense point was not wind corrected as suspected from the 0-0 MP wind data and the SFWs impacted well downwind.

SPIN should be blanked unless you are looking at the CBU-103 SMS page but ED added it for some strange reason. ED keeps making things more work than they should be then end up having to remove them because they shouldn't actually be shown. ATK AZ should be blanked when its 0 but thats not implemented either.

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  • 2 weeks later...

I'm not flying the F-16, but the subject is the CBU-105, which I'm using i the A-10C II. This is one of the few places dugussing the CBU-105 in heavy wind situations.

 

I'm flying the CSAR VULTURE MP mission. Wind at 600 feet is 6 knts and at 1600 feet 25 knts. The mission takes us into the mountains W-NW of Kutaisi. The main valley floor is at about 1600 feet, so everywhere there is 25 knts wind.

 

Dropping a CBU-105 onto a stationary column of vehicles, the free-fall of the WCMD works like a charm and the canister diploys directly over the columns. Well, almost like a charm, because when the 10 BLU-108s deploy on their parachutes, they are immediately caught by the 25 knt wind and blown a couple hundred meters in the wind's direction. When the BLU-108s spin-up and deploy their submunitions, they are already so far away from the columns, that not a single puck is aimed at any one of the 8 vehicles in the column. I can post a video if anyone feels the need to actually see this.

 

In my mind the WCMD can only make sense if it also compensates for the drift of the BLU-108s on their parachutes, otherwise the weapon is useless in heavy winds and greatly diminished in lesser winds.

 

I would like to hear from ED whether this situation is known, whether it is WAD, and if not WAD when a fix might be forthcoming.

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1 hour ago, Xavven said:

Can you manually account for the drift and set your SPI a couple hundred meters against the wind's direction?

 The CBU-105 has the WCMD (Wind Corrected Munitions Dispenser) tail. If it only takes the hull of the weapon into the correction, but not the munitions itself, then the design is half-assed and defeats itself. The pilot could compensate for the wind without the WCMD tail attached too, but that was not what was paid for.

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You could in theory set up a TGT to VRP from a given steer point and use this as an add hoc type of visual wind indication in the HUD. Making a run in to target with the CCRP bomb fall lined up close to the VRP diamond might give you rough indication of wind direction.

 

However I've never done this myself...🤔

 


Edited by RuskyV
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On 8/24/2021 at 10:23 AM, Xavven said:

Can you manually account for the drift and set your SPI a couple hundred meters against the wind's direction?

I tried several times but its impossible, and it gets even harder at greater distances.

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Posted (edited)
6 hours ago, ZeroReady said:

It'll be better once we can set the burst height lower. I always set it to 700 feet in the Warthog, almost negates any effect the wind has on the parachutes.

 

 

You can change the altitude and it lowers the drift but it also reduces the covering area a lot.

 

It would be nice to have some word of ED about this. I also experience the same issue with JSOW.


Edited by Ignition
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