Question regarding TMS fwd(up) LONG

I've seen numerous bombing/TGP how to's and they all mention setting SPI using TMS up+long

Anything I press this particular action, nothing really happens. I eventually get a SPI (labeled POINT in TGP screen) by just cycling the TMS up button.

am I doing something incorrectly, or has that changed?

thanks in advance

Sr

Are you referring to the A-10?

Are you referring to the A-10?

Yes, sorry. The A-10C

SPI is denoted on the TAD by the wedding cake symbol, the TGP will not show anything regarding this. TMS Up Short with TGP as SOI will cycle tracking modes (AREA, POINT).

SPI is denoted on the TAD by the wedding cake symbol, the TGP will not show anything regarding this. TMS Up Short with TGP as SOI will cycle tracking modes (AREA, POINT).

So is "POINT" not a SPI?

Correct, POINT is point-track mode for tracking moving objects.

Roger that... thanks for the clarification. I was certain I'd broken something.

again :doh:

TMS UP "long" means you press and hold that button for a second or so, if you are on TGP all your sensor will be looking where your TGP is looking. You can confirm this on your HUD, the square TGP marker will have a tail.

If you have Maverick on the other MFD you'll see it's seeker look at that new SPI as well.

TMS UP "long" means you press and hold that button for a second or so, if you are on TGP all your sensor will be looking where your TGP is looking. You can confirm this on your HUD, the square TGP marker will have a tail.

 

If you have Maverick on the other MFD you'll see it's seeker look at that new SPI as well.

Cool... I just kept expecting too see something on the TGP screen I was focused on.:thumbup:

A good place to begin, DCS manual, Page 87:

"Additionally, many of the buttons and switches have alternate functions if they are held down for a Short period or a Long period (1 second or more)."

I've seen numerous bombing/TGP how to's and they all mention setting SPI using TMS up+long

 

Anything I press this particular action, nothing really happens. I eventually get a SPI (labeled POINT in TGP screen) by just cycling the TMS up button.

The manual is omitting some key elements here.

What TMS Up Long really does is to set the SPI Generator. It assigns a sensor to generate the SPI, until another sensor is assigned as SPI Generator.

The current SPI Generator is always displayed on the lower left corner of the HUD.

This SPI is used for CCRP cues, and sensors can be slaved to it.

With the TGP as SPI Generator, where ever the TGP looks (more precisely: where ever TGP line of sight intersects with the ground), there's your SPI. Slewing the TGP around will automatically update the position of the SPI, so it's not necessary to assign TGP as SPI Generator again.

There's a bit of a caveat, though. When the TGP gets all tangled up because of gimbal limits, there's no use slaving the TGP back to the SPI, because where the TGP looks now is the SPI, by definition (as long as the TGP is SPI Generator, obviously).

And: When the TGP LOS goes beyond the horizon, the SPI Generator is automatically reset to STPT (Steerpoint).

So, what does that give us? First of all, the TGP is a great way to designate a target for CCRP. Just slew the TGP onto the target, make sure the TGP is SPI Generator (TMS Up Long with TGP as SOI) and verify SPI Generator on the HUD. Pickle a JDAM or whatever and egress, easy peasy.

The next brilliant thing is the option to slave all sensors to the SPI (China Hat Forward Long). A common use would be to slew the TGP on a target, make TGP SPI Generator, and then Slave All to SPI; this will include the Maverick.

Of couse, this is absolutely not limited to the TGP. No TGP on board, but a Maverick hanging under the wing? It's always an option to make MAV SPI Generator, slew it to target, Slave All to SPI, and you've got a valid CCRP solution for any bomb.

I would recommend you use a training mission and check out various SPI Generators (STPT, TGP, HUD/IFFCC, Mav, TAD) and figure out how they work, and how the various sensors react to the Slave All to SPI command. With STPT as SPI Generator, try Slave All to SPI, and then cycle waypoints. The TGP and any Mav should instantly look at the new steerpoint. :thumbup:

Another caveat: when steerpoints are above the ground (which they can be), the TGP might seem to be looking at the middle of nowhere. You may have to use the CDU to set steerpoint elevation all the way down to ground level, or if you build your own missions, make sure to set waypoint elevation to ground level after placing a waypoint.

There's more to it, but this should cover some of the basics. Yes, it seems a bit complicated at first, but once you've wrapped your head around the SOI and SPI concepts, this is surprisingly mighty!

As for POINT and AREA: these are just tracking modes. They have nothing to do with the SPI whatsoever. If you want the TGP to follow a moving target, select POINT tracking, if it's a stationary target, AREA is probably the better choice, but either one would be fine. You absolutely do not need a square (track) around a target to drop a bomb on it.

OUCH! Yurgon that is quite the convoluted confusing way to describe a SPI.

I prefer the official Airforce description:

SPI.

The SPI is defined as the point in three-dimensional space that the system uses as a unique reference for other functions, such as weapons delivery, off-board transmission, and sensor slaving.

A sensor can define the SPI only when it is the SOI, but once defined, the SPI is not necessarily confined to the SOI. For example, a change in SOI does not necessarily mean that the SPI changes. A SPI is always present unless there is an error condition such as a failed CDU. Incorporation of Datalink allows transmission of the SPI off-board.

Easiest way to think about, is the SPI is a 3d point point in space that is generated ( created/produced/updated or whatever other word you want to use and can be slewed) by a SOI .

 

There's a bit of a caveat, though. When the TGP gets all tangled up because of gimbal limits, there's no use slaving the TGP back to the SPI, because where the TGP looks now is the SPI, by definition (as long as the TGP is SPI Generator, obviously).

 

And: When the TGP LOS goes beyond the horizon, the SPI Generator is automatically reset to STPT (Steerpoint).

Are you slewing the TGP (while it's SPI) outside limits or is the plane maneuvering causing the TGP to lose LOS of the SPI?

There's a BIG difference between the two scenarios. One is manually trying to create an invalid SPI while the second one is simply a sensor losing LOS to the SPI.

The second scenario should NOT invalidate the SPI and it should remain where it was prior to the maneuver. The SPI is merely a single point with lat/long and elevation.