GBU Guidance and Laser Designators
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When I enable my Laser Arm on - the L shows up in the TGP view screen, indicating that my laser is active.
When I drop a bomb, it stays that way for a while, until it starts flashing because the bomb has picked up the beam.
How does the TGP know when the bomb has picked up the beam?
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your plane can estimate time to impact based on a (what i assume) is a radar estimation of distance to target, your altitude and your speed, and then the bomb’s speed once it is in freefall.
the GBU is set to go active at 7 seconds to impact, so all the computer does is T-7 and then it starts flashing.
in theory, it’s possible for it to be wrong but in practice it’s right pretty much 100% of the time.
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If I’m not mistaken it starts flashing when it’s actively lasing (?lazing?). The lasing time is set in the DED/DTC. I think the default is 8 seconds. I assume the FCR calculates bomb fall time and then begins lasing based on that …. i.e. lasing the last 8 seconds (or whatever is pre-set by the user).
Edit:
:arrggghhhh: Too Slow … cik beat me to it.
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All I can do is echo what’s been said before me. The L flashing only means that the laser is firing, it doesn’t necessarily mean that the LGB has actually started guiding. Try putting the TGP on a random place and depress the trigger to the first stage, this will show you the L flashing as you’re firing the laser.
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When I enable my Laser Arm on - the L shows up in the TGP view screen, indicating that my laser is active.
When I drop a bomb, it stays that way for a while, until it starts flashing because the bomb has picked up the beam.
How does the TGP know when the bomb has picked up the beam?
Im gonna be an echo and say that the L means that the laser is ARMED, not ACTIVE. The laser fires only while the L is flashing.
If you wanna be really technical, it fires two beams, one intentionally right down the TGP sight and another inadvertently at an angle of 78 degrees to the main beam. Neither beam is eye safe, nor naked eye visible.
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That’s surprisingly low tech and un-sophisticated.
I was honestly expecting some kind of answer about the designator knowing when the beam was being blocked or even the bomb itself sending some kind of laser or radio signal back.
But to find out it’s just timer based…wow. This is like finding out there’s no Santa Clause.
So if one was, for example, buddy lasing in an F-16, would there be no L and would it never blink? For that matter, how would one even know they had picked up the other planes signal?
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the bomb would not send a laser signal back. What did I just say about it not being eye safe??
If you intend to buddy lase for another jet (not possible in BMS at present) then you would continuously lase the DMPI from his bomb release to after impact, by pulling the trigger of the HOTAS past the first detent (not past the second one).
Doing so, the L would be flashing while you fired the laser. Technically speaking, you only need to give the bomb time to glide, so if the target has laser warning receivers, and you want to give them little warning, you could only lase them for the 10 seconds or so before impact.
The F-16 by default is configured to automatically self lase 8 seconds before impact.
EDIT: as for picking up the other planes signal, you can set the laser to specific flash codes. Using the LST function, you can set a flashing laser dot which is not eye visible, to be projected. Other planes targeting pods can see this laser point.
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the bomb would not send a laser signal back. What did I just say about it not being eye safe??
Yeah I get that now, I just assumed somehow it was telling the jet what was going on.
Doing so, the L would be flashing while you fired the laser.
Just to clarify, you are speaking about the cockpit of the plane doing the lasing?
What about the plane doing the dropping? Would he see nothing?
(And yeah, I know there is (disappointingly) no buddy lasing in BMS, given what I have seen of the laser designator code in ARMA 3 I am not at all surprised. It’s amazingly more complex then even I, as a programmer, would have expected.)
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Yeah, in a buddy lasing drop, only the lasing guy sees a flashing L in his TGP.
If LST is enabled then the guy doing the drop can at least see where the bomb is going to go.
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I am slightly shocked that in this day and age our systems are still so low tech, but I suppose the aircraft are fairly old.
I will be very interested in seeing the data communication options that are available on some of the up and coming modern jet fighters to see if they can address some of this.
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eh? if you’re buddy lasing you pretty much have to talk anyway. you don’t really need a complex C3 system to say “bomb 10s to impact” “laser on” “good hit”
you’re going to be saying that anyway. that’s why you have element radio.
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Paveway IIs are very simple devices. Simple is cheap, flexible, and reliable.
After a few seconds post-release the bomb seeker looks for a coded flash of light (1688 is a code number). This is very much like how a TV remote works only more narrow. After two pulse chains it confirms that it matches the code preset on the bomb. The field of view is broken up into quadrants and every 500ms evaluates what quadrant the light source is in. Based on what quadrant it blows the tail fins to steer that way. There are only four possible positions of the fins after steering is started, fully left or right (x2 fin groups). The result is it wobbles while steering. If the laser splotch is lost for a while the bomb goes dumb and can’t continue guidance.
The bomb doesn’t care where the laser energy comes from, launching airplane, another airplane, guy on the ground, etc. It would work just fine if you threw it over the side of a hot air balloon provided you pulled the arming wires and someone was pointing the IR “flashlight” at a place on the ground. The bomb either sees the target or it doesn’t which is why there are a lot of safety rules for which direction to attack from so any misses land in OK areas. Most platforms know to release the Paveway II a little long because the bomb is better able to guide short of the ballistic path than long.
This is what makes the need for laser coding in the first place. If you want to use multiple lasers and bombs in the same area you don’t want them to cross signals. The other reason is because you don’t want the enemy to produce false laser spots to ruin your aim.
In off-board lasing coordination of the laser platform with the launching platform is verbal. If you want the laser on 10 seconds before impact then when the launching platform’s computer predicts that time before impact you tell the guy over the telephone to turn on their flashlight. For ownship lasing you can do it manually or automatically. In the F-16 there is a setting that when the CCRP fall timer reaches X the laser turns on and then turns off 4 seconds after the timer reaches 0.
To ensure that the release ballistic path is near the laser spot there has to be some previous coordination to share the location. The laser designating party obviously has an acceptable target location so it is his job to make sure launching platform chucks the rock in a suitable direction so guidance will be possible. One way is to use the designation laser to produce a laser spot and have the airborne platform use a seeking sensor to see this spot and turn it into a location for CCRP delivery.
The original A-10 had such a sensor (Pave Penny) which was not a laser but could see lasers and turn it into nav or targeting data. So an old A-10A could carry and deliver a Paveway but relied on someone else to provide the laser energy for guidance. All the modern TGPs have this sort of laser discovery feature.
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Laser time is increased to 16 seconds in my config, allowing a little bit of deviation when hitting pickle button during CCRP phase of the release. Since doing so, I don’t recall a miss with an LGB.
16 seconds might not be as per doctrine, but then we don’t have to worry about jammers, etc. in F4 so I figure what the hey…
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Okay, so now I have a whole new set of questions about Buddy Lasing:
How does MY F-16 know when the bomb drop should occur if my buddy is lasing the target?
Somehow my software must be aware of the target to calculate and display the steering and targeting information on my HUD, correct?
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Basically, what happens is (supposing you lase and your wingman drops) :
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you “agree” on a target : either via description over the radio, or via a datalink-shared markpoint, or you share directly coords via the radio (not ideal)
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your wingman either create a steerpoint on the target, use the steerpoint shared via datalink, or move his cursors/TGP on the target (if possible)
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he then drops the bomb on it and let you know when the bomb is 10s to impact
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in the meantime, you have your TGP pointed at the target, ready to lase ; when he tells you, you lase.
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Boom !
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How does MY F-16 know when the bomb drop should occur if my buddy is lasing the target?
You’d drop it the same way you drop any other bomb on a target you want to hit. Designate your target (maybe using a steerpoint, or your radar, or a targeting pod) and follow the CCRP release cues until it falls off. You could also use CCIP, but typically if you have terminal guidance you want a longer fall time, and as long as it’s reasonably close to the target the guidance system will correct for small mistakes.
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Now i have a question : what happens if i release the bombs from a low altitude does it lase on release ? also sometimes i release them with no TGP lock , do they just behave like iron bomb at that point ?
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Now i have a question : what happens if i release the bombs from a low altitude does it lase on release ? also sometimes i release them with no TGP lock , do they just behave like iron bomb at that point ?
The TGP doesnt have a ‘lock’. If you release laser guided bombs with the TGP switched off, or the laser un armed, then yes, the laser guided bombs behave like dumb bombs.
If you release lower than an 8 second time of flight, then yes the TGP will lase on release.
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The TGP doesnt have a ‘lock’. If you release laser guided bombs with the TGP switched off, or the laser un armed, then yes, the laser guided bombs behave like dumb bombs.
If you release lower than an 8 second time of flight, then yes the TGP will lase on release.
I know it doesnt have a “lock” just couldnt say it better
Thanks for the answer though