Extra Crispy | 05 Aug 2016 5:33 p.m. PST |
It's an old stand by of wargaming rules. Pick a spot then roll dice to see how far your artillery drifts. It may land just where you point but otherwise it "drifts." The funny thing is, I'm reading some Vietnam memoirs and there's never any mention of accuracy. You call in a coordinate and things go boom. Never any sense of worry that it might drift in bad ways. Ditto for seeing some documentaries about Desert Storm. Pick a spot and kiss it good bye. So, dealing with professional armies post WW2 does artillery really drift? |
Murphy | 05 Aug 2016 5:41 p.m. PST |
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Mardaddy | 05 Aug 2016 5:45 p.m. PST |
Absolutely. Nobody fires just one gun at a coordinate (unless it is to check accuracy.) Targets are saturated by a battery or more to compensate for the miniscule variables that would account for "drift" off the target coordinate. Does not change your premise – They pick a coordinate and things go "boom." |
Mute Bystander | 05 Aug 2016 5:48 p.m. PST |
Guided weapons less so (lasers are your friend) but unguided rounds can at times go over or under or deviate. There is always the problem, even with computers, that a minor miscaculation or differing grids (Grenada) can cause lethal problems. |
Dynaman8789 | 05 Aug 2016 5:49 p.m. PST |
Another question for those who actually know. How did the infamous "oops I shot at my own coordinates" happen? Did they not do spotting rounds first? |
Eumelus | 05 Aug 2016 6:12 p.m. PST |
Besides the ballistic variance mentioned above, I think that "drift" mechanisms in rules represent the reality that: (a) The observer doesn't know exactly where he is – he thinks he knows his own map coordinate perfectly, but he may be off by meters or hundreds of meters; and/or (b) The observer may have misjudged the location, direction, or distance to the target; and/or (c) The battery itself may not be where it thinks it is! Every time a battery moves it has to survey itself to establish its own location, and it may be off meters or dozens of meters. When you factor in all the possible sources of error involved in the mathematical calculations inherent in indirect fire, it's no wonder that ninety-nine times out of a hundred the first round is going to miss, quite possibly by a lot. Only fire from a battery that has been in place for some time, at a pre-registered target correctly identified by the observer, is going to hit the "called" location. Otherwise you adjust (and remember that the battery has to know where the observer is, or "right fifty, add two-hundred" won't make any sense…). |
Just Jack | 05 Aug 2016 7:02 p.m. PST |
From my experiences, Eumuelus has nailed it. The person calling for fire knowing exactly where he is is the number one culprit of the three. And it's absolutely real; anyone that's trained on call for fire will tell you that you call for one on adjust; they give you shot (they fire), you acknowledge (shot out), then watch for the impact. When it hits you call it (splash), they acknowledge, and you provide adjustments. Adjusting one round onto target is much preferable to fire for effect on the wrong spot, particularly if it's your pos. If the first round was close you might give one on adjust and then go fire for effect. If it wasn't so close you'll probably do another round on adjust. Mark – I'm quite surprised you're reading Vietnam memoirs and haven't run across a bad fire mission I can tell you it's quite embarrassing to call for one on adjust and impacts so far off you can't even hear the impact. Actually stumbling through a nine-line brief is pretty nasty too… Hey, that's what training is for, right? ;) V/R, Jack |
tberry7403 | 05 Aug 2016 7:09 p.m. PST |
This is the reason behind the term Danger Close: b. Danger Close. DANGER CLOSE is included in the method of engagement when the target is (rounds will impact) within 600 meters of friendly troops for mortar and artillery, 750 meters for naval guns 5-inch and smaller, and 1,000 meters for naval guns larger than 5-inch. For naval 16-inch ICM, danger close is 2,000 meters. Link to FM 6-30 Chapter 4: link |
79thPA | 05 Aug 2016 8:16 p.m. PST |
Absolutely. If I recall my training correctly a spotting round that lands within 100 meters is on target and good to go for a fire for effect mission. |
BattleCaptain | 05 Aug 2016 8:58 p.m. PST |
I think the variable is not accuracy, but timeliness. |
Mark Plant | 05 Aug 2016 9:54 p.m. PST |
I thought that even if both OP and battery knew exactly where they were that there issues of wind, temperature and differences of elevation to factor in before you were accurate. |
Mako11 | 05 Aug 2016 10:04 p.m. PST |
Maps aren't always accurate either. |
mckrok | 05 Aug 2016 10:21 p.m. PST |
To have accurate, predictable fires, you must have accurate: - Target Location and Size (in three planes). - Launcher Location (in three planes). - Weapon and Ammunition Information. - MET Data. - Computational Procedures. Screw one of these things up, the rounds will land some place other than intended. The pressure to perform or battle makes simple mistakes easy to occur. And yes, it is possible to accidentally call fires on to ones position. I can recall an incident where the observer transposed his (observer) location with the target location. pjm |
Wolfshanza | 05 Aug 2016 11:06 p.m. PST |
Some of our maps in RVN were based on old French maps and could be up to a click off :0 . |
nickinsomerset | 05 Aug 2016 11:06 p.m. PST |
During Telic 1 an AS90 mission ended up somewhere, where the Olympic circles landed somewhere that the FOO in the phoenix cabin did not call! Tally Ho! |
Martin Rapier | 05 Aug 2016 11:40 p.m. PST |
You can also have a duff gun firing short or long, whether by technical fault or error. One of my pals was a gunner and one gun in his battery managed to shell it's own OP by firing the wrong charge. In " Company Commander" MacDonald called in or witnessed dozens and dozens of fire missions. The only ones which were halfway accurate were pre registered one's, and in one case there was a battalion FFE landing over 1000 yards short as the OP couldn't actually see what they were firing at. |
foxweasel | 06 Aug 2016 1:45 a.m. PST |
Reasons for adjustment – Human error Altitude Meteorological Human error covers a multitude of sins, poor map reading etc. I had to call check fire in Afghanistan once as the number 1 had applied 3276 (or something like that) instead of 2376 to the sight. It was night and you don't have safety checks in war. Things like that happen all the time in training. |
freerangeegg | 06 Aug 2016 1:52 a.m. PST |
I think that artillery creep in wargames is a matter of scale, and as a mechanism to show the beaten area of a barrage and stop it being a pin point weapon in a game. Regarding the firing on your own coordinates thing,Its very easy to give the wrong coordinates when you are dog tired. I recommend reading George Blackburns book, The guns of war. He was a WW2 canadian gunner officer and recounts in there a story of falling asleep from exhaustion,and giving a fire mission to his battery whilst asleep, and waking up to frantically plot where it was going to land.Thankfully it was beyond the forward troops. |
Patrick R | 06 Aug 2016 2:44 a.m. PST |
A friend of mine was in charge of a mortar battery. During live fire training he received coordinates and replied to send them again and when he received the same ones he asked to check them. The observer in charge got mad, jumped in a jeep drove up to him and asked him why he was being such asshole. "You may want to rethink these coordinates because the rounds will land in the middle of the nearby town." He replied. |
SteelVictory | 06 Aug 2016 4:38 a.m. PST |
Most of the "drift" (dispersion) is along the gun-target line, most rounds fall either short or long from the target. There isn't really too much "drift" (dispersion) left or right of the gun-target line. This is an easy explanation (actually think I found this link here years ago) link |
Viper guy | 06 Aug 2016 7:26 a.m. PST |
I can't speak for artillery rounds but I assume they might be like bombs. Basic "dumb" bombs like a MK 82 have a dispersion factor that helps determine things like min safe distances. What that means is that even on a perfect pass which, due to the laws of physics, should place the weapon exactly on the intended target, there are enough variables that will cause a dispersion. In other words even if everything was identical in the delivery, the bomb wouldn't go in the same hole. That's before all the human and environmental factors get added in. |
Sundance | 06 Aug 2016 3:38 p.m. PST |
Let me put it to you this way, I have been assured that stories of Illinois Army National Guard units completely missing the impact area are indeed true. Now, I don't know if that counts as drift or not, but sure, why not? |
Rudysnelson | 06 Aug 2016 8:22 p.m. PST |
Yes it can. FDC errors, gunner error on the powder charge or setting the numbers and observer recording error of the target are all soldier error methods which can cause drift. Gun tube wear is another reason as is planting firing stakes incorrectly. |
Callsign 21 | 06 Aug 2016 11:26 p.m. PST |
All the above are parts of what gunners call 'the gunnery problem'. I have observed the beaten zone of rounds falling gradually creep further along the gun-target line during a long method of fire for effect as the guns heated up. If it had gone on for longer a correction would have been needed to bring the beaten zone back on to the target. Very interesting to see on tbe ground. |
LORDGHEE | 07 Aug 2016 4:10 a.m. PST |
Late 1960's a friend was with his Dad driving north of El Paso and rounds landing along the road behind them as his Dad hit the gas he watched them impact trailing them. His Dad was an ex Army artillery officer who pulled into the Range HW to inform them with clearity what had happen. the Battery commander Had pointed his guns south instead of north. Just went to dinner with a vet, who mentioned that in Iraq a few years ago the artillery unit got a new computer that they cleary did not know how to use. It was a bad day he would not commit any further on. |
jowady | 07 Aug 2016 11:49 a.m. PST |
From the US DoD; "circular error probable An indicator of the delivery accuracy of a weapon system, used as a factor in determining probable damage to a target. It is the radius of a circle within which half of a missiles projectiles are expected to fall. Also called CEP. See also delivery error; deviation; dispersion error; horizontal error."
You actually wouldn't want all of your rounds, in indirect fire, to hit the same precise point. Let's say you're firing at an infantry unit dug in on a ridge. You call out the coordinates for your Fire Mission based on the center of the enemy's position. But if all the rounds hit the same spot then you're not going to be doing the maximum damage for rounds fired, so you have to continually adjust to walk your rounds over the target. It's easier, in indirect fire, to have your circular error cover the target. In addition tis allows better use of a suppressing factor from an artillery barrage that you won't get from airdropped ordinance. |
foxweasel | 07 Aug 2016 4:07 p.m. PST |
Further to my earlier post. I take it that the OP meant drift as in the first round doesn't go where you wanted it to go, and you have to adjust it onto target. That isn't drift, just the normal adjustment process. Drift is when you are firing on a target and some of the rounds start to creep away from the target. As some have already said, it normally occurs during fire for effect and you can see the rounds going up or occasionally down the gun target line. |
Lion in the Stars | 07 Aug 2016 10:46 p.m. PST |
There's also simple random dispersion/CEP. Most guns can be assumed to have a dispersion of about 18" per 1000yds, though user error can (and does) greatly increase this. That is, the shell will land somewhere within an 18" diameter circle centered around the aim point at 1000 yards, with the circle expanding directly with the range increase. 2000yds, 36", etc. Variations in shell weight and powder charge will cause variation in impact range. Wind and other meteorological conditions will move shell impacts all over the place, but typically apply to the entire battery as a whole, unless you're firing a single round per battery (say, ranging or harassing fire). |
foxweasel | 08 Aug 2016 1:32 a.m. PST |
Commonly known as the Beaten Zone. |
Charlie 12 | 08 Aug 2016 12:14 p.m. PST |
…the Battery commander Had pointed his guns south instead of north. Classic reciprocal error. There was one just as bad done by the coast artillery unit at Ft Worden on Puget Sound back in the 1910s. Seems the 12" mortars were on a practice shoot firing at towed barges out in the sound (due NORTH) when a 800lb practice round landed square in the middle of an intersection in nearby Port Townsend (the town adjacent to the SOUTH of Ft Worden). Nobody hurt but red faces all around (and a couple of careers badly damaged). |
SteelVictory | 15 Aug 2016 6:04 a.m. PST |
"the shell will land somewhere within an 18" diameter circle centered around the aim point at 1000 yards" That looks like CEP for direct fire tank main gun rounds, is it the same for 105mm-155mm artillery? 1000 yards? |
Lion in the Stars | 15 Aug 2016 11:23 a.m. PST |
About that, though it's not like most artillery would fire at less than ~8000yards, so 8x the raw dispersion, shells landing somewhere within 4 yards of point of "aim" at 8000m. Then you get all the other causes of rounds to drift, like weather and the gun tubes heating up, which makes the dispersion even larger. Guided artillery shells like the M982 Excalibur can have an absolutely tiny dispersion, even at maximum range. 50% of all shells fired at the same GPS coordinates would land within 5m, at a range of 30,000m. Unguided rounds end up with a much larger dispersion, of course, with 50% of all shells fired landing within 150m at a range of 15,000m. So about 1% of range for a rule of thumb, 80m at 8000m for the example earlier. Then again, that's including ALL the sources of dispersion: gun variability, differences in shell and propellant weight, wind effects, operator errors, you name it. Naval guns tend to be tighter-grouping, less than 0.5% of range down to about 0.1% of range. For example, the big 16" guns on the Iowa-class could put 50% of all rounds fired with 15m of the target at a range of about 15,000m. Pretty damn good for unguided shells! |