reported earlier INU drift and Lima tracking bug

[NeedzWD40]

16 hours ago, McFly0081 said:

I'll have to test if INU reset helps or possibly a full repair and reinstall of he AH-64D module.

An INU reset clears out the problem for me, but I think there may also be some map based issues along with it, because it happens more frequently on Syria than Caucasus. A good indicator is how often the PSN message shows on the TSD as it seems the INU frequently goes out of alignment, as if the GPS correction isn't happening often enough (or at all). Trying to do position updates with the PSN message doesn't work and I'm assuming such functionality is not implemented yet.

[FalcoGer]

18 hours ago, McFly0081 said:

They would take a hard left hook off the rail (sometimes right)

That's normal because of how SAR works. The higher the offset, the cleaner the radar picture gets for the seeker.

INU resets also helps for me. I still don't understand what the INU has to do with the radar missiles anyway. And even if it were involved, the offset in the INU itself and the target coordinates calculated from camera angle and laser range would cancel out anyway, even if it had 500 miles drift in it.

Edited August 11, 2023 by FalcoGer

[NeedzWD40]

28 minutes ago, FalcoGer said:

I still don't understand what the INU has to do with the radar missiles anyway.

In real terms, the ownship INU is used to align the missile INU. You're correct in that it serves as a relative reference, as the missile itself doesn't know anything except what the ownship tells it. Unless the INU is having an incredibly bad day, the space and times involved shouldn't be enough to cause an incredible miss in pure coordinate terms. My guess is that within DCS, the INU is drifting far too much for the type, is not being updated as often as it should, or there's a variance in world coordinates vs aircraft coordinates in the code that's getting mixed up.

[Mad_Shell]

10 hours ago, NeedzWD40 said:

In real terms, the ownship INU is used to align the missile INU.

I don't think this is how it works. Yes the aircraft feeds the missile INU the relative coordinates of the target, but those relative coordinates are obtained thanks to either the TADS or the FCR. The aircraft INU is not involved in the process.

[NeedzWD40]

7 hours ago, Mad_Shell said:

I don't think this is how it works. Yes the aircraft feeds the missile INU the relative coordinates of the target, but those relative coordinates are obtained thanks to either the TADS or the FCR. The aircraft INU is not involved in the process.

The missile has no way of knowing where it is without the ownship INU. During initialization, the ownship INU gives the missile the data necessary to align its own INU. Positional updates are fed every so often to keep it aligned.

[Mad_Shell]

7 hours ago, NeedzWD40 said:

The missile has no way of knowing where it is without the ownship INU. During initialization, the ownship INU gives the missile the data necessary to align its own INU. Positional updates are fed every so often to keep it aligned.

But the missile doesn't need to know where it is! It only needs to know the relative position of the target (given by the TADS or the FCR): "6km 3° on the left". The missile INU only serves for the missile to go to this relative location. No need for the missile to know its own exact location.

[NeedzWD40]

12 minutes ago, Mad_Shell said:

But the missile doesn't need to know where it is! It only needs to know the relative position of the target (given by the TADS or the FCR): "6km 3° on the left". The missile INU only serves for the missile to go to this relative location. No need for the missile to know its own exact location.

The missile uses ownship position data to correct for various parameters like velocity. Ie if your aircraft is drifting left, the missile INU is updated with that information so as to correct for it. You are correct that it's relative and the missile really doesn't care about exact coordinates, but it does need to know these parameters for a successful hit. Or that's just how Northrop Grumman/Lockheed Martin/Boeing determined the missile INU needed to work; I only know that ownship INU is used to align the missile's own INU.

[shagrat]

vor 13 Stunden schrieb Mad_Shell:

It only needs to know the relative position of the target (given by the TADS or the FCR): "6km 3° on the left".

...and its own starting position/heading/pitch etc. to know "where 3° to the left" is after launch, as the launch platform isn't necessary stable.

[Rufnax]

Hi! Same issue just happend to me today. INU drift after flying for 30-45 minutes. CAQ and Waypoints where at about 50m offset to the actual target / point.

When firing LIMA Hellfires onto the target the hellfires also missed the target at about 50m. So I would assume these two issues are somehow related.

A statement from ED would be nice to know if they are working on it already.

 

[84-Simba]

I tried yesterday on the very same mission I always do and everything was fine on my side.

The slow repair is the most probable fix for this issue.

[84-Simba]

Hi !

Since the last hotfix the Limas are broken again ; unless you do an INU reset just before you engage, the L will track something that does not exist generally short of your intended target.

Like the last time, store/slave a point will show a significant drift.

The last time a slow repair of DCS seemed to have solved the problem but not this time, unfortunately.

It really seems INU problems are impacting Limas ...

Thank you.

[84-Simba]

Thank you for the merge ... sorry that that bug is back

[Floyd1212]

We flew on a public server last night, and the flight to the AO was about 17 minutes where we then engaged two vehicles in a group of 6 with Limas at a range of around 6km.  We did not do an INU reset.  Both tracked their intended targets and destroyed them.

I'm not saying there still aren't some issues with Limas finding their intended target, but I wouldn't say it is a given that they will miss.

[84-Simba]

Weird because it is a given here.

I tried to throw 4 Limas at a Shilka, standing still, slow movment, quick movment ... the four went exactly at the very same spot, tracking something and falling short of the target.

Note that my flights are usually more than 30 minutes.

In fact, this is the very same behaviour as it was before and described earlier in this thread...

[Raptor9]

I avoided posting to this thread because I didn't want it to be misconstrued as "Working for me, so must be fine." However, in light of the recent threads that have been popping up, and since people are generally only vocal when things go wrong, not when there are no apparent issues, I wanted to share some experiences here.

I've been playing multiplayer about 4 nights a week since 2.9 dropped, to include large scale public servers like Through the Inferno, and I've had a success rate above 90% in hitting my targets with AGM-114L. When the missile did fail to strike the intended target, it was because it was very close to another target, it was near obstructions like buildings or treelines that interfered with the missile's flight path, or we started aggressive evasive maneuvers just prior to or during launch.

Most of these multiplayer sessions exceeded 2 hours in length, and on none of them did I ever reset the INU, despite the perpetual white PSN on the main TSD page.

As some advice, verify the following before launch:

1) You are keeping the TADS stable when lasing the target.

2) If the missile displays LOBL when you finish lasing, allow it to find the target so that it displays RF MSL TRACK, otherwise it didnt actually lock onto the target before launch (just like how the laser-guided missiles say PRI CHAN TRK when they actually see the laser).

3) The missile is fired within the displayed launch constraints as soon as you finish lasing the target. I've seen a lot people shooting these missiles in very bizarre ways, ranging from 90 degree off-axis shots to lasing the target and holding on to the missile for an amount of time before firing. (This is as strange as locking on to an enemy aircraft, pointing away from the enemy aircraft, and then firing an AMRAAM)

Not doing these three things will only reduce the likelihood of the missile striking the target that you want. I'm not saying anyone here is not doing these things, but I have seen a number of interesting "techniques" among some players. I bring these things up as unsolicited suggestions since on more than one occassion, even before 2.9, I will have played in multiplayer sessions exceeding several hours, firing off large numbers of the radar-guided Hellfires, after multiple trips to the FARP. One particular 3 hour session last week I fired 34 AGM-114L's and the only one that did not hit its target was the one that was blown up as it left the rail when a SAM from a Tunguska hit me at precisely the same time.

[84-Simba]

The thing is, the missile is not missing.

When you follow the trajectory with the F6 view you'll see that it turns toward the intended target, pass before it and do a quick move in the last second before impact.

It tracks and shaqs something that is not there and definitely not the intended target.

And if you lase/store a target and slave on it you'll se how much it drifts.

I know that someone will say that they are 2 different bugs but as soon as the INU is reset (just before beginning the engagment) the missiles work properly.

[Floyd1212]

37 minutes ago, Raptor9 said:

I've been playing multiplayer about 4 nights a week since 2.9 dropped

Were there changes made in 2.9 on how the Limas behave?  (I don't recall seeing anything specific mentioned in the patch notes.)  Or were changes made prior to 2.9?

I'll load up 4 full racks of Limas and see how things go.  I have been taking just a couple Limas for targeting SAMs, and I will say they have been working better for us recently.

[Raptor9]

13 minutes ago, Floyd1212 said:

Were there changes made in 2.9 on how the Limas behave?  (I don't recall seeing anything specific mentioned in the patch notes.)  Or were changes made prior to 2.9?

I don't know of any.

My response was aimed at the renewed bug report traffic about this topic after the 2.9 update, even though I hadn't encountered any issues with the -114L prior to 2.9. The intent was to provide my own recent observations of the behavior in 2.9, but to also reinforce that I wasn't having issues in 2.8 either. The 3 suggestions I posted above were more of a shot in the dark to potentially help anyone that may be struggling with their behavior, that may not be related to anything involving the INU.

[NeedzWD40]

7 hours ago, Raptor9 said:

Most of these multiplayer sessions exceeded 2 hours in length, and on none of them did I ever reset the INU, despite the perpetual white PSN on the main TSD page.

The conditions that result in needing consistent INU resets to get maximum accuracy are quite variable and I've been unable to pin down an exact cause. The only consistency I've found is faster degradation on some maps, like the Persian Gulf and Syria. With the new track system it might be worth it for a few of us to take some long single player tracks of the problem and see if that might give any hints.

As an experiment tonight, I took an aircraft out on a 30 mile trip for approximately 20 minutes before firing missiles. The targets were in defilade at the Minakh airbase, consisting of SA-8, SA-9, and ZSU-23.

A stable hover was commanded after waiting for the attitude hold to calm down, then an IAT track was achieved on a SA-8. LMC was not required.

The missile acquired a SA-9 to the right. A second shot was fired after this and the missile repeated this acquisition, striking the dead SA-9. Due to this, INU resets were commanded and once the heading was updated, the target was acquired again; a full INU alignment was not achieved at this point.

Note that the TSD still shows an empty map and the INUs have still not realigned. IAT achieved and laser ranging for data.

Third missile acquired as indicated in TADS.

I was going to ask if potentially IAT had issues, but I doubt that would be the case since the third missile hit the indicated target. Generally speaking, I've had pretty good success with the 114Ls, but I've also been prudent about manual INU resets whenever I'm nearing a position.

[QuiGon]

Since the relase of 2.9 this issue returned for me as well. First off, @Raptor9 if this issue occurs, the missile's don't just go for another nearby target or so, but hit the ground at a consistent offset to the target. So for example one missile will hit the ground 15m to the left of a target and the next missile launched at the same target will hit the exact same spot on the ground and the next one will do so as well and so on. That is even consistent over different targets, so when fired at a nother target the missiles will then hit the ground 15m to the left of that target. INS reset fixes that.

Now what causes this issue is still not entirely clear to me, but I think it's desync between both crewmember clients caused either by a temporary freeze of one of the two clients or by server lag. I think this is also the reason why I get this issue with the Lima Hellfires a lot again in 2.9, as the servers are much more unstable now.

[84-Simba]

1 minute ago, QuiGon said:

Since the relase of 2.9 this issue returned for me as well. First off, @Raptor9 if this issue occurs, the missile's don't just go for another nearby target or so, but hit the ground at a consistent offset to the target. So for example one missile will hit the ground 15m to the left of a target and the next missile launched at the same target will hit the exact same spot on the ground and the next one will do so as well and so on. That is even consistent over different targets, so when fired at a nother target the missiles will then hit the ground 15m to the left of that target. INS reset fixes that.

Now what causes this issue is still not entirely clear to me, but I think it's desync between both crewmember clients caused either by a temporary freeze of one of the two clients or by server lag. I think this is also the reason why I get this issue with the Lima Hellfires a lot again in 2.9, as the servers are much more unstable now.

Exactly that but I have it in SP as well ...

[[DE] T-Bone]

We were recently able to use the Lima in flight against ground targets without any problems, but noticed that our TG points were slightly different from the CPG to the pilot TSD display.

I created a TG on a building using a SAT card in the TSD. My CPG also saw the TG, but not on the building, but to the left of it.

To me it looks like with CPG and Pilot we have two separate INS systems communicating with each other and then with Desyncs we have this discrepancy.

[QuiGon]

3 hours ago, [RENEGADES] T-Bone said:

We were recently able to use the Lima in flight against ground targets without any problems, but noticed that our TG points were slightly different from the CPG to the pilot TSD display.

I created a TG on a building using a SAT card in the TSD. My CPG also saw the TG, but not on the building, but to the left of it.

To me it looks like with CPG and Pilot we have two separate INS systems communicating with each other and then with Desyncs we have this discrepancy.

I noticed the same with the TADS a few days ago: my CPG was pointing the TADS at a small building, while on my pilot TADS repeater it was looking ~15m to the side of the building.

Edited November 3, 2023 by QuiGon

[LuftwaffePro]

Can confirm the bug still persists. After ~30 min flight Limas hit the ground at some distance drifted from the target, and stored targets when slaving to them appear at drifted, incorrect locations.

[placsea]

Also can confirm this issue is still persisting.

Not being able  to quickly designate with the tads and fire and instead having screw around with the radar, ensure the nts is actually the target I want is obviously not ideal in time sensitive situations.