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INS only CCIP in the Hornet


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21 hours ago, toilet2000 said:

You really don't understand how the CCIP cross is computed.

I suggest looking a bit a the tutorials on the A-10C, as it only uses it's INS/GPS combined with DTED (Digital Terrain Elevation Database) to compute the slant range and point of impact.

Old Hornet models used to simply compute the CCIP slant range (and thus the cross position) using the radalt or baro altitude (like the Mi-24) or using the AGR when commanded to (Sensor Select to HUD). The radar doesn't directly need any INS data to compute slant range.

Hornets that received the TAMMAC upgrade (like ours, except for the HSI) have the integration of the DTED, meaning the aircraft, knowing its position from the INS/GPS, can infer the slant range by correlating its slant angle and INS position with the elevation database and finding the intersection of both. This gives slant range, but only if the INS is accurate. This is generally not an issue because moments without GPS coverage are often small enough that the INS won't drift enough for the accuracy to be that much lower.

The issue arises when you completely remove the GPS on a whole mission with a bird made to fly with GPS and with the DTED integration.

TL;DR Yes, the CCIP cross should depend on the INS position when not in AGR mode.

 

But if you use AGR with our current hornet in dcs. Should that fix the un-precise ccip cross due to our TAMMAC?


Edited by gregfp66
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More weirdness:

I flew 2 hops. Fast forwarded on the first on the first one to get past 30 min. and the DIL line went crooked. I followed NFM-000 procedures for position updates. I tried DSG (via HUD), AUTO and TACAN. Nothing worked. Out of curiosity I switched POS/INS to POS ADC, reset master caution and put it back to POS/INS... and the DIL pointed straight down, go figure.

That got me 'thinking'. I went to ADI to see how the attitude indicator changed on INS, it was off a small amount. I changed to STBY and the horizon was tilted 10 deg. the opposite way... OK. :confused:

Now, it also seems like I stumbled on a band-aid (if anyone wants to fly missions circa early '80s). My mission was set for 1983 and the ATFLIR was in the warehouse.:biggrin:

I loaded the ATFLIR, flew for 45 min. and the INS never got out of whack until I tried position update, just for the heck of it. My WPDSG was on runway numbers. The ATFLIR was looking exactly at the numbers but I still followed the procedures for DSG update. As expected, the DIL went almost horizontal and I could see that I still had a TGT lock somewhere. I turned toward it and saw the CCIP cross with a diamond superimposed on it... stuck on the ground point. It seemed like a random point although there is a chance this was a overfly point at the time I pressed TDC on FLIR and accepted it on HSI. I'm done testing this. Someone needs to look at this.

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INS updates should not affect the lateral position of the CCIP. CCIP is not dependent on positional data. In other words it doesn't give a dam where in the world you are.

 

As a side note the update process is not yet functional in DCS imo.... and when it is in the POSINS domain then brings in the subject of your Accept/Reject criteria.

 

As to DTED and its relevance in CCIP. I think this a red herring .... again the issue we are seeing is the lateral displacement of the CCIP DIL line. In Auto we get a similar effect with the ASL even after a point blank designation .... again with an AGR range sample. The system is currently porked without POSAINS.

 

Gripes I think your selection of POS/ADC and back to POS/INS and getting the DIL line back to vertical is a good finding and narrows down the cause of this bug. I don't see its relevance IRL but in the DCS internal calcs it seems super relevant to me.

 

Thinking this further (brain hurting). We know the DIL/ASL error gets bigger with with time. We have seen that if the erroneous CCIP DIL is displaced to the RIGHT then we designate the erroneous ASL is displaced to the LEFT even in zero wind.

BSwind.jpg

 

 

This would make sense if the DCS MC2 thought there was a significant wind from the LEFT. This would mean the CCIP + would be deflected downwind and the ASL steering reference would be displaced upwind(exactly what we are seeing) We also have seen the displacement is always Easterly for the CCIP + and westerly for the ASL. We know in the Sim the bombs still fall directly under the VV.

 

We know we don't see this bug if using POSAINS with GPS input.... so in essence any INS drift is corrected for by the mixed INS/GPS solution, so in the SIM with POSAINS there is no need to model system drift.  So ....... Is DCS using a pseudo internal wind to simulate INS drift in POSINS ?.... Perhaps the switch from POSINS to POSADC and back to POSINS resets some internal variable (zeroing the pseudo wind) to start the pseudo INS wind drift again ?? So you start from zero and everything looks ok..... keep flying and the issue accrues from that switch over time as T=0.

 

Off to test some more.

 


Edited by IvanK
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Posted (edited)
2 hours ago, Gripes323 said:

Out of curiosity I switched POS/INS to POS ADC, reset master caution and put it back to POS/INS... and the DIL pointed straight down, go figure.

 

I tried it, but couldn't make it work.

 

It will be vertical at 2 headings . in gulf map its. around 30 and 210 dgs. But the bombs will then miss long or short.


Edited by Svend_Dellepude

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INS updates should not affect the lateral position of the CCIP. CCIP is not dependent on positional data. In other words it doesn't give a dam where in the world you are.
 
As a side note the update process is not yet functional in DCS imo.... and when it is in the POSINS domain then brings in the subject of your Accept/Reject criteria.
 
As to DTED and its relevance in CCIP. I think this a red herring .... again the issue we are seeing is the lateral displacement of the CCIP DIL line. In Auto we get a similar effect with the ASL even after a point blank designation .... again with an AGR range sample. The system is currently porked without POSAINS.
 
Gripes I think your selection of POS/ADC and back to POS/INS and getting the DIL line back to vertical is a good finding and narrows down the cause of this bug. I don't see its relevance IRL but in the DCS internal calcs it seems super relevant to me.
 
Thinking this further (brain hurting). We know the DIL/ASL error gets bigger with with time. We have seen that if the erroneous CCIP DIL is displaced to the RIGHT then we designate the erroneous ASL is displaced to the LEFT even in zero wind.
BSwind.jpg
 
 
This would make sense if the DCS MC2 thought there was a significant wind from the LEFT. This would mean the CCIP + would be deflected downwind and the ASL steering reference would be displaced upwind(exactly what we are seeing) We also have seen the displacement is always Easterly for the CCIP + and westerly for the ASL. We know in the Sim the bombs still fall directly under the VV.
 
We know we don't see this bug if using POSAINS with GPS input.... so in essence any INS drift is corrected for by the mixed INS/GPS solution, so in the SIM with POSAINS there is no need to model system drift.  So ....... Is DCS using a pseudo internal wind to simulate INS drift in POSINS ?.... Perhaps the switch from POSINS to POSADC and back to POSINS resets some internal variable (zeroing the pseudo wind) to start the pseudo INS wind drift again ?? So you start from zero and everything looks ok..... keep flying and the issue accrues from that switch over time as T=0.
 
Off to test some more.
 
It makes sense for the CCIP cross to be displaced one way and the AUTO ASL the other. Both solutions are having you fly the same way. At least that's consistent...

But I agree with your post. There appears to be what I can only describe as a fake wind effect that's tied to the INS drift, since the INS attitude is not affected, but only the bombing solution is. In all cases, without wind, the CCIP line should extend towards where the INS thinks the ground is, so the INS drift would have no effect here. And if the INS attitude was truly affected, then the HUD horizon would be at an angle so that the CCIP line should be 90 degrees off that, towards wherever the INS perceives "down" to be.

After thinking about it, it seems to me that DCS is taking the drift between the coordinates in the INS and the "real" coordinates and it adds that drift into the bombing calculation. But of course, that's wrong, since the INS is the only position-keeping system here. The INS is wrong, but it doesn't know it's wrong.

Lastly, the whole thing with DTED has no bearing here, since that would only affect the bombing solution's vertical displacement.
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I tried the switch didnt do anything for me, no change.

 

Svend. Being ok on two headings with Long Short errors and displace on other headings would fit with the pseudo wind therory. When Directly into  wind DIL would be vertical, When going crosswind obviously leaning downwind.

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53 minutes ago, IvanK said:

INS updates should not affect the lateral position of the CCIP. CCIP is not dependent on positional data. In other words it doesn't give a dam where in the world you are.

 

As a side note the update process is not yet functional in DCS imo.... and when it is in the POSINS domain then brings in the subject of your Accept/Reject criteria.

 

As to DTED and its relevance in CCIP. I think this a red herring .... again the issue we are seeing is the lateral displacement of the CCIP DIL line. In Auto we get a similar effect with the ASL even after a point blank designation .... again with an AGR range sample. The system is currently porked without POSAINS.

 

Gripes I think your selection of POS/ADC and back to POS/INS and getting the DIL line back to vertical is a good finding and narrows down the cause of this bug. I don't see its relevance IRL but in the DCS internal calcs it seems super relevant to me.

 

Thinking this further (brain hurting). We know the DIL/ASL error gets bigger with with time. We have seen that if the erroneous CCIP DIL is displaced to the RIGHT then we designate the erroneous ASL is displaced to the LEFT even in zero wind.

BSwind.jpg

 

 

This would make sense if the DCS MC2 thought there was a significant wind from the LEFT. This would mean the CCIP + would be deflected downwind and the ASL steering reference would be displaced upwind(exactly what we are seeing) We also have seen the displacement is always Easterly for the CCIP + and westerly for the ASL. We know in the Sim the bombs still fall directly under the VV.

 

We know we don't see this bug if using POSAINS with GPS input.... so in essence any INS drift is corrected for by the mixed INS/GPS solution, so in the SIM with POSAINS there is no need to model system drift.  So ....... Is DCS using a pseudo internal wind to simulate INS drift in POSINS ?.... Perhaps the switch from POSINS to POSADC and back to POSINS resets some internal variable (zeroing the pseudo wind) to start the pseudo INS wind drift again ?? So you start from zero and everything looks ok..... keep flying and the issue accrues from that switch over time as T=0.

 

Off to test some more.

 

 

 

There's also an attitude drift present when you look at ADI.  I can understand the horizon slightly tilted because of INS line up degradation (?) but not as much from STBY.  The HUD doesn't seem to be effected regardless of source. Is it possible that the horizon tilt effects DIL (pointing the same way the horizon is tilted). Also, in case of error, how does ADC corelate data from standby instruments?  It's probably a lot quicker to ask here then read up on all this stuff... some day.

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On 8/4/2021 at 5:24 PM, IvanK said:

We are talking about "Old Hornet models"  pre GPS Hornet, without DTED and using AGR. That is what DCS is simulating if you have a mission date before 28 March 1994 as I see it.

 

In any case regardless of Slant range source the DIL shouldnt be displaced from the vertical nil wind and in balanced flight !

 

 

No, we don't have an "Old Hornet model", we have a Lot 20 with TAMMAC and all the bells and whistles. Choosing a 1994 date doesn't change the plane, it only makes GPS unavailable.

Same goes for the F-14. Changing the date doesn't give you an earlier model.

 

The DIL could very well be displaced horizontally due to incorrect wind calculation, incorrect attitude estimation and wrong altitude. Best example is using Snakeyes, which you will see the DIL jump left and right from each releases at low altitude due to the offset between stores, with the horizontal jump getting bigger the lower the altitude.

As I said, there is a bug nonetheless, but it's simply untrue that GPS/INS pos is supposed to have no impact on the CCIP solution.

20 hours ago, gregfp66 said:

But if you use AGR with our current hornet in dcs. Should that fix the un-precise ccip cross due to our TAMMAC?

 

Yes, that's the bug I talked about in one of my previous comment


Edited by toilet2000
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1 hour ago, toilet2000 said:

No, we don't have an "Old Hornet model", we have a Lot 20 with TAMMAC and all the bells and whistles. Choosing a 1994 date doesn't change the plane, it only makes GPS unavailable.

Same goes for the F-14. Changing the date doesn't give you an earlier model.

 

The DIL could very well be displaced horizontally due to incorrect wind calculation, incorrect attitude estimation and wrong altitude. Best example is using Snakeyes, which you will see the DIL jump left and right from each releases at low altitude due to the offset between stores, with the horizontal jump getting bigger the lower the altitude.

As I said, there is a bug nonetheless, but it's simply untrue that GPS/INS pos is supposed to have no impact on the CCIP solution.

Yes, that's the bug I talked about in one of my previous comment

 

 

AGR wouldn't fix your attitude issues. Have you looked at ADI discrepancies, bank and pitch in both, INS and STBY?  HUD attitude is in its own world on top of that. 

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8 hours ago, toilet2000 said:

The DIL could very well be displaced horizontally due to incorrect wind calculation, incorrect attitude estimation and wrong altitude.

How does an incorrect altitude affect the horizontal displacement of the Dil and CCIP + ?

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9 hours ago, toilet2000 said:

No, we don't have an "Old Hornet model", we have a Lot 20 with TAMMAC and all the bells and whistles. Choosing a 1994 date doesn't change the plane, it only makes GPS unavailable.

Same goes for the F-14. Changing the date doesn't give you an earlier model.

 

The DIL could very well be displaced horizontally due to incorrect wind calculation, incorrect attitude estimation and wrong altitude. Best example is using Snakeyes, which you will see the DIL jump left and right from each releases at low altitude due to the offset between stores, with the horizontal jump getting bigger the lower the altitude.

As I said, there is a bug nonetheless, but it's simply untrue that GPS/INS pos is supposed to have no impact on the CCIP solution.

Yes, that's the bug I talked about in one of my previous comment

 

 

You are not really being very helpful.

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More testing. Again 1985 44mins POS INS Designated then flew for 44 mins. INS Drift measured as 008T/117m .

Same Story CCIP and ASL leaning over as before.

drift44mins.jpg

 

 

Re designated same deal ASL pops up left and CCIP and DIL way out to right.

 

So then using CCIP flew around to establish where the CCIP cross and DIL were vertical under the VV

Heading 220 DIL and CCIP + Vertical

Heading 310 DIL and CCIP + Leaning way out to right

Heading 040 DIL and CCIP + Vertical

Heading 180 DIL and CCIP + Leaning way out to Left

 

So deduced that the "Pseudo Wind " error lies on the 220/040 bearing

Dropped on Heading 040 Bomb impacts well short >500m short

Dropped on Heading 220 Bomb impacts Well over the top >500m Long

(A further note on heading 220 I could not ever achieve a CCIP solution as CCIP + was off the bottom of the HUD regardless of Dive angle and IAS. AUTO solution was possible)

 

So to me if this is a "Pseudo wind" issue then the Pseudo wind is blowing or its affect is coming From 220M

 

 

 


Edited by IvanK
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Sitting on the ground same location POS INS 1985

Take a Mark point. Select MK point and selecting steering to Mark point. range obviously 0.0nm.

Do nothing 1 hour later Markpoint drifts to 039M/for 1.3nm = INS drift

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16 hours ago, IvanK said:

Sitting on the ground same location POS INS 1985

Take a Mark point. Select MK point and selecting steering to Mark point. range obviously 0.0nm.

Do nothing 1 hour later Markpoint drifts to 039M/for 1.3nm = INS drift

 

Well IvanK, I think you have enough evidence to show the things are not working right. I hope you got your report on the way. Then again... the current implementation could just be half baked, unfinished stuff.

I'd send it anyway. 


Edited by Gripes323
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A few more numbers that give magnitude to this CCIP/AUTO POS INS issue.

 

Looking at known dimensions of FA18 HUD symbolgy, and extrapolating where the CCIP cross would be based on the reflected cue. Reveals it to be 170mills displaced from the VV.

Now Looking at MK82 LD Ballistic tables for a 10deg dive 560KTAS at 2400ft Altitude gives a 1.79 Mill/Kt crosswind correction factor.

So 170mills is basically equivalent to a 95Kt cross wind component. ..... and we know actual wind is zero.

 

CCIP-Crosswind.jpg

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Posted (edited)

Not with the game right now, but i seem to remember that there is something about wind on the HSI/ DATA/ A/C page that shows a heading but no speed when no wind is present in the mission.

 

What happens if the windspeed is something else than zero?


Edited by Svend_Dellepude

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HSI AC DATA has a page that shows Wind direction and speed ... had a look it just says wind direction 045 with no velocity in this scenario.IRL it should show INS derived wind speed and direction.

 

EDIT: Just put 40Kts of wind in at all levels. Velocity doesn't show up on the AC Data page just reads 0. So yet to be implemented I think.

 

EDIT2: And of course with real wind present in AG mode the VV,Pitch ladder and all other linked symbology drifts down wind in the HUD.


Edited by IvanK
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Just a quick thanks for @IvanK for all this thorough testing work! :thumbup:

I hope the devs take notice?

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On 8/6/2021 at 5:28 PM, IvanK said:

How does an incorrect altitude affect the horizontal displacement of the Dil and CCIP + ?

 

Because the stores aren't mounted on the centerline.

 

It actually looks like the CCIP solution is using 0 altitude (like if you were on the ground) on your images. That huge offset (170 mils) looks a lot like if you were flying basically as close to the ground as possible.

 

I'd be curious to see if mounting only a bomb on the centerline gives that kind of offset too.

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8 minutes ago, toilet2000 said:

 

Because the stores aren't mounted on the centerline.

 

It actually looks like the CCIP solution is using 0 altitude (like if you were on the ground) on your images. That huge offset (170 mils) looks a lot like if you were flying basically as close to the ground as possible.

 

I'd be curious to see if mounting only a bomb on the centerline gives that kind of offset too.

 

On 8/6/2021 at 1:07 AM, Svend_Dellepude said:

 

I tried it, but couldn't make it work.

 

It will be vertical at 2 headings . in gulf map its. around 30 and 210 dgs. But the bombs will then miss long or short.

 

How do you explain this then?

 

On 8/7/2021 at 1:48 PM, IvanK said:

HSI AC DATA has a page that shows Wind direction and speed ... had a look it just says wind direction 045 with no velocity in this scenario.IRL it should show INS derived wind speed and direction.

 

EDIT: Just put 40Kts of wind in at all levels. Velocity doesn't show up on the AC Data page just reads 0. So yet to be implemented I think.

 

EDIT2: And of course with real wind present in AG mode the VV,Pitch ladder and all other linked symbology drifts down wind in the HUD.

 

 

I noticed the same. I'm also starting to think that the windspeed might not be 0 in the sim but 0,x.

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6 hours ago, toilet2000 said:

I'd be curious to see if mounting only a bomb on the centerline gives that kind of offset too.

Will test on Centrline only. However the angle the DIL leans over is a function of time, the longer you fly the more it leans over.

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