investigating GBU and wind

[USAF-Falcon87]

GBUs seem to be inordinately affected by the wind.  I could understand (maybe) if they fell short of the target when being dropped into a headwind, but it's not just that.  When dropped with a tailwind, the bombs fall long.  With a laser, and sufficient energy (which they have with a tailwind), there's no reason they shouldn't be spot on.

 

The attached track is from an F-16 with 30 kts wind, but I have had similar results since the last patch with the AV-8B and A-10C II as well. 

GBU with 30 kt wind.trk

[USAF-Falcon87]

Anyone?  Bueller?

[Fromthedeep]

As far as I'm aware, this is a very complicated topic. IRL there are certain calculations that have to be done to compensate for the wind and it also relies on the host aircraft having a proper wind model and that it compensates during the designation. 

[MARLAN_]

I don't know about other modules, but the F/A-18C doesn't even have wind data in the aircraft, it simply displays 0. That may be part of why the GBU is not compensating for wind.

[Fromthedeep]

15 hours ago, MARLAN_ said:

I don't know about other modules, but the F/A-18C doesn't even have wind data in the aircraft, it simply displays 0. That may be part of why the GBU is not compensating for wind.

So, assuming that there's good enough and accurate wind data and the release solution itself is computed accurately, the PW2 is released at the ballistic release point. In theory, even if you don't lase, the weapon should impact the target. If the jet has accurate wind data, the release point should compensate for the wind. The issue with not having a properly compensate drelease point is that during the guidance phase, the bomb wouldn't have enough energy to compensate for a headwind or it would have too much energy in a tailwind and it would blow past the seeker field of regard and wouldn't pick up the spot. 

 

To ensure even better accuracy, depending on the wind component, the lase spot should be shifted. There are calculations that shows how much you have to shift depending on the wind component (so think like 2 feet per knots of headwind or something along those lines) but you should never move the spot off of the target. If the bomb picks up the spot and simply refuses to compensate for the wind, the issue is with the guidance logic itself. If it tries to compensate but it doesn't have enough energy, the culprit is the lack of wind compensated release point. Now the devil is in the details because accurate data about the peculiarities of PW2 guidance logic is not available publically. There are a lot of nuanced interactions with the flight path, the guidance scheme, the field or regard of the seeker and the release parameters, especially in challenging conditions. 

[USAF-Falcon87]

There are a couple of issues at play here: 1) proper computation of the CCRP launch point compensating (or not) for wind, and 2) guidance to the laser designator.  

Regarding the first one, as MARLAN_ mentions above, if the aircraft doesn’t have access to proper wind data, there couldn’t be any correction for that in the CCRP computation (and honestly I don’t know if real-world systems do or not).  In that case, it would require adjusting the drop point (prior t drop, before laser is activated) to account for the wind, then moving the spot once the laser is activated to provide proper guidance.

However, when dropping downwind, the bomb should have plenty of energy, so as long as you don’t wait too long to start lasing the target, there is no reason for the weapon to miss—it would just hit with a bit more kinetic energy. So whether the drop point computation is accurate or not, laser should still guide the weapons properly to the desired target.

[28270]

You're not alone. I am experiencing the same. GBUs are terribly inaccurate on moving targets, even when it's AI attacking. I'm doing a mission test with 12 T-90s on the move and I'm only getting 3 hits out of 16 launches with the Hornet. This has never happened, I have reported it in another thread with no response from the team.

[Flappie]

Can we please have a track showing the issue?

[28270]

hace 1 hora, Flappie dijo:

Can we please have a track showing the issue?

Unfortunately it's a one hour mission and when we get to the bombing area the runway is out of sync, however I'm attaching this snippet showing the glitches. 16 GBU-12 and only two positive hits.

 

[Flappie]

I need at least the mission file to know the wind settings.

[28270]

hace 10 horas, Flappie dijo:

I need at least the mission file to know the wind settings.

[28270]

Unfortunately, I didn't save the desynchronized track and didn't save the mission in its initial configuration because we couldn't accomplish the mission with the GBU-12s and decided to replace them with the AGM-65F. But the wind settings are the ones I show in the screenshot above.

[Flappie]

Thank you. I'll give it a go today.

[USAF-Falcon87]

On 3/21/2022 at 7:07 AM, Flappie said:

Can we please have a track showing the issue?

There’s a track on the very first message in this thread.

[28270]

TEST GBU-12-WIND.zip

Here you have the mission edited, ready on the runway, four T-90s 10 miles from Vaciani and four GBU-12s.

Edited March 25, 2022 by 28270

[28270]

Edit: Right now I'm just failing T-90's on the move. The T-90 requires a direct hit and the GBU-12 hits at one to two meters with the moving target.

With static T-90 I am getting good hits.

Artificial intelligence with GBU-12 keeps failing 3 out of 4.

Edited March 25, 2022 by 28270

[28270]

GBU-12 TEST WING.zip

Here a play track

[USAF-Falcon87]

Here's yet another track.  Still a problem.

GBU with 30 kt wind again.trk

[USAF-Falcon87]

17 hours ago, USAF-Falcon87 said:

Here's yet another track.  Still a problem.

GBU with 30 kt wind again.trk 540.65 kB · 1 download

And here is the mission file

Maverick TGP test with wind.miz

[USAF-Falcon87]

Still a problem in current build.

GBU with 30 kt wind again 2022-05-02.trk

[XCNuse]

I have been learning the hornet near the beginning of this year, and I've had a heck of a time trying to get LGBs to hit their targets.

I genuinely don't recall this being an issue up through last year.

 

It doesn't make sense to me that a laser guided bomb should ever miss its target unless something went wrong during the release phase.

 

A group I fly with has been absolutely struggling hitting moving targets with GBU12s, like it has constantly missed by <5 feet, and does practically zero damage to them..... because of poor / lack of splash damage.

 

That said the person that likes to build the missions does like to add wind.

Regardless....... LGBs shouldn't end up 5ft away from a lased target that consistently, like the lasing point isn't updating fast enough.

Hitting non-moving targets, never misses.

[NineLine]

Checking. 

[NineLine]

I am checking if there is wind restrictions, I tried slightly slower winds (in your mission) and they hit good every time, but your are dropping into 24 m/s and then at GRND its 11 m/s. 

 

[NineLine]

6 hours ago, XCNuse said:

I have been learning the hornet near the beginning of this year, and I've had a heck of a time trying to get LGBs to hit their targets.

I genuinely don't recall this being an issue up through last year.

 

It doesn't make sense to me that a laser guided bomb should ever miss its target unless something went wrong during the release phase.

 

A group I fly with has been absolutely struggling hitting moving targets with GBU12s, like it has constantly missed by <5 feet, and does practically zero damage to them..... because of poor / lack of splash damage.

 

That said the person that likes to build the missions does like to add wind.

Regardless....... LGBs shouldn't end up 5ft away from a lased target that consistently, like the lasing point isn't updating fast enough.

Hitting non-moving targets, never misses.

Track?

[XCNuse]

21 hours ago, NineLine said:

Track?

None as of yet, all occurrences have been in multiplayer.

 

HOWEVER, one thing that has happened consistently, has been the release of GBU38s during the same missions.

I haven't had a moment to do basic tests, but I'm wondering if this is somehow tied into the bug with the gun pipper in AG being wrong in the Hornet when you have employed GBU38s?

That said, OP stated this was happening in Viper.

 

Other thing I can say when this has occurred, has been high altitudes; I don't mean aircraft at high altitudes, I mean the vehicles at high altitudes.

This happened in the NTTR test ranges, and this past weekend in Syria in some of the mountains.