GBU-12 in AUTO mode

[Bananabrai]

Hi all,

yesterday I experienced a weird issue, but it might have been a user error. I am very early in learning, was my first weapon deployment.
I had some buddies with me along explaining and dropping bombs as well...

- I was dropping GBU-12 (4x on each side) in AUTO, STEP, N/T mode from 20.000ft
- TGP was SOI, my WP 2 was target point (2. (2-dot) and triangle), and relatively close to some spread out M60 victim tanks, ELEV was set
- I slewed the TGP over a tank and initially used the HOTAS command AUTO-ACQ-PRESS to box AREA track
- (I noticed this is possibly wrong to just box ATRK or PTRK or CPTR, I later tried to sometimes box it, sometimes not)
- I slewed again, AUTO-ACQ-AFT to slave to WP, slewed over a tank again and performed TDC PRESS
- TPOD format displayed DESGINATE (I assumed now the target really must be designated)
- During my inbound section I noticed I come very close (I already felt a too late bomb drop) and the bomb fall line was also off to the side, sending me maybe 0,25 or half a mile next to the target (Wind was 4m/s at 8000 meter, 4m/s at 2000m and 0 at 0, so not much wind)
- I tried again and again, flew more outbound sometimes as well, always DESIGNATING with the TDC press, sometimes with LASER on to ensure more precise measurement... always dropped the bombs maybe 2nm too long, unable to see the LASER

My buddies were together in one bird and, apart from some TGP desync issues, were able to hit targets with GBU-12 and GBU-24
 

[Stingray87]

Did you check the laser code on the TGP? It sometimes (?) defaults to 1111 whereas the LGBs default to 1688. Speaking from expepience...

[Ramstein]

same thing happened to me... but I wasn't sure if I did something wrong... I am in VR so there's that.. it is like pulling teeth getting instructions for the F-15E... trying to learn how to use the weapons...

[lt_d4n]

I have the same problem too. It happens with all gbu. It seems that sometimes the bomb is guided by the laser and sometimes not because they fall far from the marked target. looks like a bug

[Rhinozherous]

Also experienced misses with no appearent reason - From about 10.000ft, Code was set, Master Arm on, Laser lased. But without changing anything the next bomb was right on target.

Edited July 2, 2023 by Rhinozherous

[Sarge55]

It could be your INS alignment is off. Did you do a cold start?

Just to confirm it’s not anything to do with your alignment go to options and set alignment preset to always aligned and try the mission again. If it is still a problem then you know it isn’t your alignment. 

Sorry guys... The drop down to choose type of alignment isn't there.  It was a pre-release video I saw it in. 

null

Edited July 2, 2023 by Sarge55
Correction

[Adrian858]

2 hours ago, Sarge55 said:

It could be your INS alignment is off. Did you do a cold start?

Just to confirm it’s not anything to do with your alignment go to options and set alignment preset to always aligned and try the mission again. If it is still a problem then you know it isn’t your alignment. 

I've been having an issue similar to the OP as well, but mine feels more like INS drift as the waypoints become displaced by a few hundred feet when slewing to them. Happens about 45 mins after takeoff. This was after doing both a Stored Heading, and manual GC alignment.

I can't seem to find the setting you mentioned in the options for "always aligned" though, unless I'm just blind? In the ME, I have "Cold Aircraft needs GC Alignment" ticked.

 

[Sarge55]

@Adrian858  You're right!  It's not there...  I was working from a GR video I saw pre-release and Cap showed a drop down of the three options.  Sorry about that.  I always use the start unaligned so never checked in the special tab.    Wonder why they took it out?

[Adrian858]

@Sarge55 I'm happy it's not just me than, lol! I saw it previously on a GR video as well, prior to releasing EA. I tried doing some digging to see if I can do an inflight update to the INS, but I haven't been able to find any information elsewhere. When checking the manual (pg: 131, UFC), a note states "NOTE: INS update is not implemented in the current version of the module."

[Bananabrai]

On 6/28/2023 at 6:38 PM, Stingray87 said:

Did you check the laser code on the TGP? It sometimes (?) defaults to 1111 whereas the LGBs default to 1688. Speaking from expepience...

Checked it. My buddies hit the target and talked me through

21 hours ago, lt_d4n said:

I have the same problem too. It happens with all gbu. It seems that sometimes the bomb is guided by the laser and sometimes not because they fall far from the marked target. looks like a bug

Actually in the German Forum section someone pointed out it even was mentioned in the release notes. I had more luck going into a steady 5° dive 20 seconds prior release.
No misses any more.

17 hours ago, Sarge55 said:

It could be your INS alignment is off. Did you do a cold start?

Just to confirm it’s not anything to do with your alignment go to options and set alignment preset to always aligned and try the mission again. If it is still a problem then you know it isn’t your alignment. 

Sorry guys... The drop down to choose type of alignment isn't there.  It was a pre-release video I saw it in. 

null

 

Interesting. Didn't check yet, so should have the default settings.
I am always doing the full GC align. Status was OK, 0.0.

Also I would expect drift being updated by GPS, wouldn't it?

[Sarge55]

Correct, however, it depends on the year your mission is set in. I think any mission before 1996 is pre GPS and requires INS updates which isn’t implemented yet in F-15E apparently.

There is a setting though that forces GPS on for all years. 

[Biggus]

I'm seeing this happen periodically.  A string of good bomb drops that hit their mark, one that will head off to the side for no apparent reason and then back to some more good drops.  I found that CDIP works great, but likely because I'm generally in a bit of a dive.  I'll try auto with a more nose-down attitude.

[Swift.]

5 hours ago, Sarge55 said:

Correct, however, it depends on the year your mission is set in. I think any mission before 1996 is pre GPS and requires INS updates which isn’t implemented yet in F-15E apparently.

There is a setting though that forces GPS on for all years. 

Are INS updates no implemented? I was doing INS position updates the other day, but maybe it's velocity updates that are still WIP?

[Sarge55]

Hi Swift,

I was referring to Adrian858's post.

On 7/2/2023 at 12:40 PM, Adrian858 said:

@Sarge55 I'm happy it's not just me than, lol! I saw it previously on a GR video as well, prior to releasing EA. I tried doing some digging to see if I can do an inflight update to the INS, but I haven't been able to find any information elsewhere. When checking the manual (pg: 131, UFC), a note states "NOTE: INS update is not implemented in the current version of the module."

 

[Bananabrai]

On 7/4/2023 at 8:18 AM, Sarge55 said:

Correct, however, it depends on the year your mission is set in. I think any mission before 1996 is pre GPS and requires INS updates which isn’t implemented yet in F-15E apparently.

There is a setting though that forces GPS on for all years. 

1986 in DCS. I am aware of this. 

But thanks for pointing out.

[dorianR666]

6 hours ago, Bananabrai said:

1986 in DCS

no it depends on the module.

for hornet its 1994 https://forum.dcs.world/topic/207530-psa-ins-alignment-solution-for-ob-25531917/#comment-3915166

for strike eagle its 1998.

Edited July 5, 2023 by dorianR666

[Rhayvn]

It's related to a bug with the AUTO bomb fall line incorrectly compensating for wind in most cases.  You will find that if you drop into or with the wind or with very little crosswind/wind you will have success.  You can mitigate this by looking at the TGP offset number in the upper left of the TGP display.  That shows the angle the TGP is from the nose of the jet.  Ensure you are between 2L - 0 - 2R and the LGB should guide every time.

My guess is that the reason it's less evident in a a dive is because it reduced the amount of wind correction a drop would require, therefore the erroneous offset the current system is giving you in AUTO.

Edited July 7, 2023 by Rhayvn

[Raven (Elysian Angel)]

Yes I think it's related to wind as well: I usually put a pretty decent amount of wind in my missions, based on real world weather maps and wind charts for that particular region.
The success rate of my GBU12 drops hasn't been too stellar either.