GBU-10/12 missing moving targets

[Lord Vader]

Hi all

 

In multiplayer environment, using both the A-10C II Tank Killer and the F-16C Viper, me and my squadron were unable to hit moving targets (tanks at flank speed), missing them just barely behind.

When the targets halted movement, we resumed the attack being able to hit them without an issue. This situation only occurred when the targets were moving.

We also noticed that in MP the sync isn't working correctly as it seems the bombs miss the non-moving targets by a long shot, but he targets still explode. This is clearly a server to peer sync issue.

 

Conditions:
Airframes: F-16C Viper and A-10C II Tank Killer.
Starting point: Cold and Dark on ramp. Full INS alignment or Stored Heading, not relevant to the bug/glitch.
Map: Persian Gulf.
Weather: Surface wind at approx 10kts (shouldn't affect targeting).
Targets: Moving at flank speed and standing tanks (T-90).
Procedures: As per manual, CCRP drop with precision laser point track mode using the TPOD, laser painting a 15 seconds before impact latched and/or manual laser painting.

 

Observation:
Moving targets are missed, falling the targets path, just behind.

Standing targets are hit, but the explosion of the ordnance is registered far from the target.

I would post a track file, but the mission was over 2 hours long with multiple clients trying the same attack for an extended period. Furthermore, I think this is fairly easy to replicate with some standing and moving targets on your own.

Besides, we just want to know if this is a single case situation on our side or a global DCS glitch.

[fmedges]

What aspect did you attack the convoy from? Keep in mind that when the laser goes on it has to be in the seeker heads field of view. I’ve found that attacking very fast moving vehicles from the front or sides can (depending on the drop altitude) cause the bomb to not see the laser and just go ballistic into the ground. Check your track file, you’ll be able to see if the bomb saw the laser or not. 

[Lord Vader]

Hi

 

I tried attacking on multiple quadrants, front, sides, back, doesn't seem to affect the bomb's effectiveness.
I also noticed that by following the bomb using the F6 view, it is tracking the laser and making adjustments till impact. I am dropping it within the "keyhole", it is tracking the laser, it's just not hitting the target, barely missing it. If the target stops, then it's effective, and I am not doing anything different nor did I even encountered this issue before.

[Skarp]

I’ve had issues hitting moving targets as well.

[fagulha]

Same here, can´t get a hit with moving targets using TGP. But this is a known bug and already reported.

[Silent253]

I dont think the paveway II series lgbs have an Ins like the gbu 24 does. it thus cant predict the movement of the target. Its only capabal of doing an pursuit curve, similar to what is shown in the image.

[Svend_Dellepude]

On 3/24/2021 at 6:46 PM, Silent253 said:

I dont think the paveway II series lgbs have an Ins like the gbu 24 does. it thus cant predict the movement of the target. Its only capabal of doing an pursuit curve, similar to what is shown in the image.

 

Either that's a very fast vehicle or a very slow bomb.

[Cupra]

And don´t forget that those bombs do not fall on a perfect laser line... the following details are just my own speculations of the data that have been available in public sources. As far I understand the flight path of GBU bombs with laser they always try to get the right point. But sometime they are above flight path, somethimes the are below. They also can be left or right of the flight path... so depending on hight, way to go and kind of delivery of the bomb it will not hit the point where the laser is pointing, it will hit a litte bit left or right.. if your bomb has a cource of maybe 1m, the difference can be 2m in total.. a driving vehicle might be now out of this range...

 

But mybe I am wrong too... if that please correct me and give me valid information about the perfect guidence of the LGB stuff  

 

[Iron_physik]

On 4/2/2021 at 12:13 PM, Cupra said:

And don´t forget that those bombs do not fall on a perfect laser line... the following details are just my own speculations of the data that have been available in public sources. As far I understand the flight path of GBU bombs with laser they always try to get the right point. But sometime they are above flight path, somethimes the are below. They also can be left or right of the flight path... so depending on hight, way to go and kind of delivery of the bomb it will not hit the point where the laser is pointing, it will hit a litte bit left or right.. if your bomb has a cource of maybe 1m, the difference can be 2m in total.. a driving vehicle might be now out of this range...

 

But mybe I am wrong too... if that please correct me and give me valid information about the perfect guidence of the LGB stuff  

 

that comes down to the "Bang Bang" guidance of early LGBs like the paveway II

 

 

Paveway uses a optical array to focus the laser reflection onto a specific point on a sensor disk:

 

that sensor disk has 4 quadrants that can sense a laser:

 

depending on what quadrant the focused laser lands on different fins are deflected

 

Fin deflection is always 100%, so the laser spot dances back and forth on this disk, thats why LGBs have this "snake" like flight path.

to get better guidance in all degrees of freedom the bomb also has a very slight spin.

 

the name "bang bang" comes from the fins always switching back and forth at full deflection.

[deadpool]

You're seeing a mixture of two problems:

 

- Splash damage is not modelled correctly in DCS. Tanks just don't care that 1000lbs just went of next to them.

- The laser point update frequency has it lag behind the target at higher speeds ever so slightly. So even with the non bang-bang steering that those GBU10/12s have in DCS they hit behind the tank for that reason.

 

You can observe this by doing a continous LSS from a second plane and see it lag behind as well.

 

What I haven't tried,yet is marking laser + NVGs to see if that also lags behind at higher ground target speeds. But I wouldn't be surprised.

[deathbysybian]

Can you use a track point offset to "lead" the vehicle?

[Fri13]

On 3/24/2021 at 7:46 PM, Silent253 said:

I dont think the paveway II series lgbs have an Ins like the gbu 24 does. it thus cant predict the movement of the target. Its only capabal of doing an pursuit curve, similar to what is shown in the image.

 

That is a good presentation of the problem.

 

I had wrong understanding of that earlier as well. The key informations are already stated in this thread, a simple laser guidance and bang-bang wings guidance.

 

When example a GBU-12 is dropping, it doesn't have any other energy than altitude and release speed. 

It has limited wing sizes and control method. 

 

Changing a 250 kg bomb direction aggressively is not really possible if target distance is unknown and bomb can not know predictive trajectory to it. This is what above mentioned GBU-48 gets with a GPS+Laser+INS guidance unit.

 

The previous bang-bang unit purpose is just to keep bomb nose pointing straight to target.

And now if you think about moving target or low altitude/low angle, but high speed release the bomb is falling by gravity toward ground. It doesn't have wings to glide or really alter it's trajectory. Even if the guidance wings can turn bomb nose on target, it doesn't mean that bomb wings has enough lift to start pushing bomb toward laser spot just by having it nose pointing at it.

 

You would need a proportional navigation to it so bomb would try to intercept the laser spot by keeping it steadily in the field of view.

 

This is as well reason why you shouldn't laze the target too early after release, as the bomb needs to use it's energy for the high trajectory to gain distance to above target and then use just aerodynamica to get it pointed around the already decided drop point. 

If laser is activated too early, then bomb will start turning to keep bomb nose straight to it.

So instead high arc travel to above target, it is trying to go straight. And as more it is turning and turning toward laser spot, more drag the bomb gets and it stars to fall sideways by nose pointing at the target, and going short.

 

If laser is activated too late, then bomb is dropping at high speed by it trajectory and wings has no enough lift to turn and alter it's trajectory.

 

Relative to the targeting system, a moving target is same as a sidewind.

There was a rule of thumb about how much you needed to lead the release point to moving direction (to the wind).

It should be in the ED own bomb tutorials in youtube. But it was something similar as every knots you add a feet toward wind (direction of moving target traveling).

 

And in A-10 you can program this to computer so it calculates the lead, or you could use the targeting pod lock system to point pod manually front of the target while it keeps off-set locked on target.

 

So if a car is moving 40 km/h to east, it is same as 21 knots and so on you would need to aim 21 feet / 6 meters ahead, so about 1½-2 cars length.

 

We don't have the bang-bang modeling in DCS and that leads to situation that GBU-12 and alike are too accurate for moving targets, windy scenarios and at short relase-impact delays as the guidance would be waving it around.