What is LOS?

It's an abbreviation not in the manual or in the posts I've found. Obviously it's so basic that nobody bothers to define it. It is used in the context of 'TGP LOS' as well as others.

Line os sight

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Of ^

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And to elaborate a little, the direct line between the sensor (tgp) and the target. It’s relevant in tgp conversations because of the LOS passes through your aircraft, the target is masked.

It’s also commonly used in BFM to describe how an opponent is moving relate to a fixed point on your canopy. Technically LOS rate in that context, but its said “LOS aft” if moving towards your rear half.

Line of scrimmage;)

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It's an abbreviation not in the manual or in the posts I've found. Obviously it's so basic that nobody bothers to define it. It is used in the context of 'TGP LOS' as well as others.

Line Of Sight

But you will as well find out that it is same thing as a "Slant Range" in other context.

The manual should have at the start or at the end the list of abbreviations.

Thank you to all who replied. So on the hud the LOS of the airframe is the dashed circle?

Thank you to all who replied. So on the hud the LOS of the airframe is the dashed circle?

Nope, that's the Depressible Pipper (think of it as a backup aiming aid in case all the fancy avionics get shot to pieces and you still need to put weapons on target).

Also, there's no such thing as "the aircraft's line of sight". I think what you mean would be the Zero Sight Line (ZSL), which you can think of as an imaginary line through the center of the airframe that extends out the nose of the aircraft straight ahead. There's no ZSL-symbol that I'm aware of, other than placing the Depressible Pipper at 0 mils.

Coming back to Line Of Sight, it's a term often used with regards to the TGP. The TGP can look up, right, left and down, and where ever it looks at - that's the TGP's LOS. Makes sense, right?

Now imagine you've got a target dead center in the TGP, you're descending, and the target becomes obscured by a mountain - that means the TGP no longer has LOS with the target. In other words, the TGP's LOS now intersects with the mountain in front of the target.

So LOS is not where your aircraft is pointing, but rather refers to the LOS between you, as a pilot, or the senors of your aircraft, and what you or the sensors are looking at.

Does that make sense?

Yes... but the ‘depressive pipper’ is where the gun points. Is it not the ZSL because it takes bullet drop into consideration? What is the distance is is zeroed to? I know the gun has a 5 mil accuracy - at 1000 ft it is accurate within 5 ft.

...

Now imagine ... the target becomes obscured by a mountain - that means ... the TGP's LOS now intersects with the mountain in front of the target.

 

So LOS is not where your aircraft is pointing, but rather refers to the LOS between ... the sensor ... and what ... the sensor is looking at.

 

Does that make sense?

That's it! Just consider the LOS manifested by the reticle (crosshair) of the TGP sensor.

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Yes... but the ‘depressive pipper’ is where the gun points.

As I understand it, it's "depressible", as in "it can be depressed by the pilot", not "it can be depressive".

By default, the depressible pipper is set to 0 mils, so it coincides with the ZSL. Once the pilot pushes the DEPR rocker switch up or down, the pipper can be set, well, above or below the ZSL.

Is it not the ZSL because it takes bullet drop into consideration? What is the distance is is zeroed to? I know the gun has a 5 mil accuracy - at 1000 ft it is accurate within 5 ft.

Again, it's used as a backup aiming aid. I don't have any formulas available, but in theory it would work out to do the math: height, airspeed, dive angle, ammo type (and possibly a few more variables), and then with the proper depressible pipper setting the projectiles should hit right where the pipper is placed over the ground.

As long as the CCIP gun reticule is available, you don't need the depressible pipper at all for gun runs.

Some more reading material:

STBY HUD MODE & the depressible pipper: how to get a WWII-style gunsight in A-10C

depressible pipper function

I'm sure the forum search and google can give you a lot more info on this topic.

Back to the OP's original question. In it's simplest terms, LOS is Line Of Sight. Can you draw an imaginary line between your reference point (you, your aircraft, a sensor or other device within your aircraft such as the radio) to the object in question (a target, another friendly aircraft, a communications satellite, etc.) If you can, you have LOS, if it's blocked you don't have LOS. It has nothing to do with distance. During the day, we have LOS to the sun unless there is something in the way, like clouds or smoke, and it's 98M miles away. At night we don't have LOS because the Earth is in the way.

LOS is important for more than just targeting. For example, radios are, for the most part, LOS dependent. The curvature of the Earth, among other things, will block a radio signal unless it is relayed. This is what makes satellite communications so important. The LOS between your radio and a satellite is much better than point to point near ground level. That satellite has a much broader reach than any normal radio can have as it sits so high up that the entire hemisphere beneath it becomes it's LOS. So by using it as an intermediary, you can contact any other radio in the satellite's LOS more reliably, and with much less power. Your radio won't have LOS to the other, but the satellite has LOS to both of you.

For targeting, LOS is simply, can you or your sensor "see" the target. Slant range is a distance to target, regardless of LOS, they are not the same thing. LOS is not the same as visual range either, there are weapons that can fire at targets you personally can't see (BVR, Beyond Visual Range). It's really a geometry issue, not a visual one.

LOS can be interrupted both visually or by interference with a sensor. A camera can be masked by part of the aircraft, clouds can block your view or interfere with a radio wave. Some fat dude can step between you and that hot redhead in the bar. Anything that interferes with your ability to draw that imaginary line to the target. Some defensive systems are designed to disrupt LOS, such as smoke generators, radar jammers, flares and chaff, and so forth. Again, anything that breaks that imaginary line.

Back to the OP's original question. [...]

Great explanation and good examples! :thumbup:

Some fat dude can step between you and that hot redhead in the bar..

The worst kind.

Thank you all for clear answers to a simple question.

All wrong! LOS means "Line of Spending". Used commonly when discussing graphs displaying one's annual spend on flight simulators and associated paraphernalia.

LOS aft is rarely used in this context for obvious reasons :) lol

Although Line Of Sight is the most common to me, I believe I may have seen LOS used in non-aviation / non-military to describe "Loss Of Signal". I'm not sure, but this may be limited to spacecraft, like Voyager, or re-entry signal loss from ionized air, or a sattelite no longer responding. It might also be used in maritime too, but I don't recall. And even in space communications, you can still have Line Of Sight be relevant, when a vehicle is behind the moon or other celestial object, though I'm not sure the acronym is used that way in that field of work.