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Laser Spot Track and SPI question


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Not sure if I found a bug or if I have a procedure error during a mission with a JTAC over a target and illuminating with its laser. I have the TGP on the right MFD and it is set as SOI and is the SPI, Mavericks selected via DSMS and on the left MFD. LST code set correctly and initiate a laser spot search. The TGP will find the laser and move into spot track. So far so good, and everything seemingly working as intended.

At this point I move to the Maverick screen and set as SOI, then China Hat FWD long to slave to SPI. Instead of the seeker moving to the SPI, both the TGP and seeker shift to the current steerpoint. Very odd behavior as China Hat FWD long is supposed to slave all sensors to SPI.

If this sounds like a bug, I'll make sure to get a track and make a bug report.

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It sounds like you may not have been in TGP line of sight SPI. When doing this look at the bottom left of your HUD where it says what your steerpoint is. If you have the steerpoint as SPI china hat forward and aft long will both slave your TGP to the steerpoint. It sounds like that is what happened. If you had TGP line of sight SPI selected already it should have slewed your maverick to the TGP LOS.

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That’s the puzzling part, the TGP was already SPI before starting the laser spot search. Next time I fly it I’ll check it and try making it the SPI again after it finds the laser.

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That does sound strange. As a workaround, Unless you are trying to hit a moving target there is no reason you need to leave the laser in LST  after you find the target. the LSS/LST is a tool to get your sensors correlated onto the target after you have the target in the pod you can take it out of LST and put your pod in area track, take a mark, or put it into a steerpoint

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4 hours ago, Diesel_Thunder said:

LST code set correctly and initiate a laser spot search

When you do that, what does the lower left corner of the HUD read?

In the A-10C II in the latest OpenBeta, mine immediately jumps from "TGP" to "STPT", indicating that the SPI is no longer generated from the TGP and has reverted to the default, which is the current steerpoint. I suspect that this is old behavior and is probably the same in the A-10C I and II modules and also across different DCS versions.

Logically, it would make sense to reset the SPI from TGP to STPT when a laser spot search is started because the TGP is now scanning all over the place. One could also argue this shouldn't change the sensor that generates the SPI. Yet again, a point could be made that the TGP in LSS is not slewed by the pilot and it would be unclear whether the SPI rests on the spot that used to be SPI before LSS was engaged or if it should be updated during LSS, so to avoid any possible confusion, LSS would revert the SPI back to STPT. Either way, I don't know which of these is realistic, but in DCS it seems LSS resets the SPI Generator away from the TGP.

On a side note, in the A-10C II in OpenBeta, I could for the first time ever slew the TGP above the horizon without the SPI Generator reverting from TGP to STPT; I'm pretty sure in previous versions a SPI above the horizon was not possible with the TGP. (HUD aka TDC as SPI still reverts to STPT when slewing too high, though.)

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vor 15 Stunden schrieb Yurgon:

On a side note, in the A-10C II in OpenBeta, I could for the first time ever slew the TGP above the horizon without the SPI Generator reverting from TGP to STPT; I'm pretty sure in previous versions a SPI above the horizon was not possible with the TGP. (HUD aka TDC as SPI still reverts to STPT when slewing too high, though.)

No it has always been possible. I have often used to do that when I hae a long way to fly on our persistent server, 100nm or more. I just slewed all sensors to SPI (STPT) and then set TGP SPI. When I got there (for example Sochi from Kutaisi) it was right on point and at 40-50 nm out I got a picture. The SPI is a coordinate on the topography of the earth, nothing more. 

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2 hours ago, Ephedrin said:

No it has always been possible. I have often used to do that when I hae a long way to fly on our persistent server, 100nm or more. I just slewed all sensors to SPI (STPT) and then set TGP SPI.

That's not at all what I described. 😉

2 hours ago, Ephedrin said:

The SPI is a coordinate on the topography of the earth, nothing more. 

With the TGP pointing above said earth, what's the SPI?

When I just tested this by placing a markpoint with the TGP pointing into the sky, the markpoint ended up circa 50 NM ahead of my jet with an elevation around 286,000 feet, though I'm not sure if that's maybe missing a digit or more in the CDU display. 😄

By placing the TGP on far away ground, I was able to create markpoints farther than 50 NM out.

I'm still convinced that in earlier DCS versions, the SPI Generator would automatically switch from TGP to STPT when the TGP was slewed above the horizon, but I can't replicate that in 2.7.18 (current Stable) or 2.8 (current OB).

Sure, it doesn't make any sense to create markpoints/SPIs in the sky, so it's no big deal. I'm just surprised it's even possible, because the behavior of where that point is seems a bit undefined to me. 🤷‍♂️

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19 hours ago, Diesel_Thunder said:

That’s the puzzling part, the TGP was already SPI before starting the laser spot search. Next time I fly it I’ll check it and try making it the SPI again after it finds the laser.

For reference the ONLY datum in the cockpit that identifies the SPI sensor is in the lower left of the HUD, there is no indication anywhere else.

The wedding cake symbol denotes where that sensor is looking, but if you have multiple sensors looking there, it can be ambiguous which one is doing the pointing.

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vor 14 Stunden schrieb Yurgon:

the SPI Generator would automatically switch from TGP to STPT when the TGP was slewed above the horizon,

That‘s true, I seem to have misunderstood what you meant. There is nothing to be set as a SPI above the horizon but the A10 has to have a SPI so it reverts to the STPT (or it should at least)


Edited by Ephedrin
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I was able to test this last night, both with a JTAC and buddy lasing, while watching the bottom corner of the hud. The SPI does change to STPT each time you initiate a search. Once it detects and shifts to laser track, I can change the SPI back to the TGP and then slave the Mavs to that laser spot. 
 

Reflecting on this, I think this SPI behavior changed when 2.8 released. I don’t recall this being an issue before 2.8, and I’m not certain if this is how it’s supposed to work or if it’s a bug.

Thanks for the help guys!

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33 minutes ago, jaylw314 said:

Ergonomically, it would make more sense for the SPI to change to STPT temporarily during LSS, then switch back to TGP automatically.  No idea how it works IRL though.

The only automatic SPI Generator change that I'm aware of is when SPI reverts to STPT; this happens whenever a sensor can no longer generate a valid SPI (HUD TDC above horizon, TAD unhooked, ...).

While I think you're right that an automatic SPI change away from TGP and then back would be ergonomic, it would not be in line with the way the system behaves in any other regard. For instance, it would be nice if the HUD became SPI Generator again as soon as the TDC goes back below the horizon (provided the HUD was already SPI Generator before it reverted to STPT). But then I'm sure pilots would be even more confused about the system, especially with the SPI Generator only shown in the lower left corner of the HUD, where it's not always obvious to pilots what happens (this thread serves as a prime example 😄 ).

I think in order to keep the system simple, it makes sense to not change the SPI Generator automatically, unless a change is absolutely required, and teach pilots how to work the system to their advantage.

In all likelihood, this is an issue that we're facing in DCS because we have to figure it out ourselves, but is probably not much of a problem in real life because proper procedures are hammered into students' brains by their instructors. 😉


Edited by Yurgon
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3 hours ago, Yurgon said:

The only automatic SPI Generator change that I'm aware of is when SPI reverts to STPT; this happens whenever a sensor can no longer generate a valid SPI (HUD TDC above horizon, TAD unhooked, ...).

While I think you're right that an automatic SPI change away from TGP and then back would be ergonomic, it would not be in line with the way the system behaves in any other regard. For instance, it would be nice if the HUD became SPI Generator again as soon as the TDC goes back below the horizon (provided the HUD was already SPI Generator before it reverted to STPT). But then I'm sure pilots would be even more confused about the system, especially with the SPI Generator only shown in the lower left corner of the HUD, where it's not always obvious to pilots what happens (this thread serves as a prime example 😄 ).

I think in order to keep the system simple, it makes sense to not change the SPI Generator automatically, unless a change is absolutely required, and teach pilots how to work the system to their advantage.

In all likelihood, this is an issue that we're facing in DCS because we have to figure it out ourselves, but is probably not much of a problem in real life because proper procedures are hammered into students' brains by their instructors. 😉

 

If a pilot started LSS with the TGP as SPI, it would make ergonomic sense to return the TGP to SPI--after all, why were they doing LSS in the first place? 🙂 

Of course, since all this was probably designed when people were still using Windows 95, that might have been too much to ask...

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