What does VT mean?

[Juju]

Hi guys!

Okay, did a search, but nothing came up. I'd like to know what the 'VT' stands for in the 105MM VT and the 155MM VT artillery. Can anyone tell me?

Thanks, Juju

[Mannheim Tanker]

IIRC, it stands for "variable time" (meaning you can preset the rounds to detonate above ground level, or even after they impact).

[Juju]

Really? Sounds cool. I think I'll check that out right away with the editor. Thanks Tanker.

[Juju]

Well, I've tested the stuff. It doesn't seem possible to preset anything, but I noticed the majority of shells explode above ground level (very little craters).

Now, this is nice and all, but what is the advantage of spending quite a few extra points for a VT spotter? In what situation are these guys used best?

[Joe Shaw]

While I'm no expert on these rounds, the primary advantage is that they are proximity fused. Meaning that they "sense" their proximity to, in this case, the ground or trees and explode a pre-set distance from them. The advantage? Simple, you get airbursts rather than ground bursts. And airbursts,especially tree bursts, are much more devastating to troops than rounds which burst at ground level.

Joe

[Talenn]

IIRC, isnt VT the great granddaddy of the current ICM type of shell? They are useful for showering troops with fragments via airbursts. They dont do squat to armor, but the casualties they inflict on exposed troops are horrifying. I havent messed with them in the game yet, so I cant tell you how they translate, but I think thats the general idea.

Talenn

[Jarmo]

Bummer, only the fastest survivive..

<BLOCKQUOTE>quote:</font><HR>Originally posted by Juju:

Now, this is nice and all, but what is the advantage of spending quite a few extra points for a VT spotter? In what situation are these guys used best?<HR></BLOCKQUOTE>

Shrapnell raining down, deadly on infantry.

Even for those lying down.

[This message has been edited by Jarmo (edited 07-14-2000).]

[Juju]

Thanks all! Got the idea now.

[Pawatwooper]

Also so you know, VT rounds are used to collapse trench lines and fox holes by hitting the ground, digging 3 or 4 feet deep then exploding. I have not tried them in the game, but, if it's been coded in the game to work that way, try them on entrenched inf and bunkers.

[JTMauney]

"VT" originally meant "variable time" fuze. This was literally true of those used in WWII. Basically, the FDC (fire direction center) chief, after doing his plot and calculations for fire, knows to within 1/10 second how long it will take the round to intersect a level plane after firing, referred to as TOF (time of flight). From this data, he can tell the gun crews to set the fuze so that the round will--theoretically--detonate at a certain height above ground by looking at the fuze-setting tables and backing off the TOF value. I say "theoretically" because the reality is that the tables are calculated for dry air, zero wind and sea level barometric pressure, (unless you have a REALLY comprehensive set of tables or a modern fire control computer with accurate weather data to enter into it). The reality, of course, is that this set of circumstances rarely occurs. In addition, unless they're firing on a desert plain, steppe, or tundra, it's highly unlikely that the target is at the same level as the gunline. This requires that the FDC chief and his plotters coordinate the data on their plotting wheel (basically a rotating circular cartesian coordinate board) with the grid as given on the map. This, of course, takes time. The old, true "VT" was not notoriously accurate unless it had been dialed in on a RP and test-fired first.

The modern version, which is still referred to by the old "VT" terminology, more out of military tradition and momentum than any real meaning, is in reality a radio-return detonation fuze; i.e.- primitive radar. It defaults, IIRC, to a burst height of 30ft AGL for 81mm mortars. I'm not sure about artillery shells, as I was only in mortars, but the distance will be relative to the effective casualty radius of the specific shell. This system is much more reliable, (with one caveat, which I'll get to in a minute), but unless I'm mistaken was not yet available during WWII. Anyone who has solid information to the contrary, please feel free to correct me on that point.

The only big downfall of modern "VT"--outside of availability--is its senstivity. It has a habit of detonating on returns from water vapor (fog, clouds) and suspended particulates (smoke, WP, dust clouds). It is, however, very useful for attacking troops who are well dug-in to open-topped defenses such as foxholes and trenches. The modern USMC teaches you to build, when you have the time, a foxhole with both a firestep and a VT artillery shelter (basically a slit-trench dug sideways into the base of the foxhole) as well as grenade sumps and such.

To my knowledge, the only true variable-time fuzes that are still in use today are on illumination rounds (to set burst height-- much harder to do correctly than it sounds, believe me), and RP (red phosphorous), which is set to burst high and "rain" down over an area to provide an IR/TI opaque smoke screen (and start really big fires in the process, usually). The RP is VERY effective, too. With a high burst altitude, (100m or so), you can effetively build an 800m wide smokescreen in less than one minute from firing, using only four 81mm tubes at four rounds each, (traversing the guns, of course).

I'm thinking that the VT in CM is TRUE VT, not the radio-return fuzed type, so don't be too surprised if it doesn't work perfectly.

Pawatrooper: What you're thinking of is a standard fuze set to "delay". Normally, a fuze is set to "superquick", which causes surface detonation on moderately hard surfaces and up (e.g.- dry ground). With a fuze set to delay (standard fuzes have both settings), the round will penetrate a fraction of a second before detonation, causing it to create a deeper crater. This is not, however, what the setting was intended for, as an artillery round that penetrates dirt has an effective casualty radius of just about *zero*. (Remember, the best backstop in the world is dirt or water-- or both). The purpose of delay is to punch through foliage canopy and get the round close to the ground. Dense, tall pine forests, heavy deciduous growth, and double- or triple-canopy jungle can ruin a good fire for effect, especially with arty, (moreso than mortars). Remember, those arty rounds aren't falling as vertically as the mortar rounds are; hitting a treeline and detonating 1/4 second early could put your FFE off by several dozens of meters. Delay allows the round to punch through to where it's supposed to detonate. "Tree-burst" is not nearly as effective as popular lore makes it out to be. That shrapnel comes off in very large chunks and spreads rapidly. It's hard enough to actually hit someone with shrapnel when the ground is focusing the explosion into a single hemisphere; when it's a full sphere and detonating at an altitude above ground level greater than its ECR, and then having to penetrate through branches, etc. to get to the target, it's not really at its most effective. Treeburst can create a semi-effective "poor man's VT" in certain circumstances, but my normal practice when firing into a dense treeline was to call for delay fuze. I wanted that explosion as close to the enemy's noggin' as I could get it.

[Joe Shaw]

<BLOCKQUOTE>quote:</font><HR>unless I'm mistaken was not yet available during WWII.<HR></BLOCKQUOTE>

And I could be wrong as well, but I recall seeing a documentary about the development of an artillery round that I thought WAS proximity fused with electronics in the warhead that allowed it to determine ... proximity Again, I may well be wrong but I clearly recall the documentary. Whether this is the "VT" round BTS is referring to or not I couldn't say of course.

Joe

[Redleg]

Proximity fuzes (VT) were available to the US forces in WWII but were kept secret. VT fuzes are not necessarily timed to explode, but rather timed to arm. Older VT fuzes have 1 sec ticks on them which, IIRC, arm the fuze close to the target. The actual detonation is done by RF proximity roughly 50m in the air. Setting the timer to Point detonation is an option.

Modern time fuzes are used on newer WP, ILLUM, and ICM/DPICM (Cluster bombs).

This is all from memory, but on sun I can get my trusty US FM from my artillery days to verify.

[Seanachai]

This site is like owning a military Ency. Britannica. Thanks JTMauney and others for constantly exposing me to a shower of penetrating info...

A friend of mine (who served as a sargeant in Germany with US forces in the 80s), always used JT instead of his given name. Turns out his given name was John Thomas, and after serving alongside Brit troops in NATO, he refused to use anything but the initials ever after.

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After witnessing exceptional bravery from his Celtic mercenaries, Alexander the Great called them to him and asked if there was anything they feared. They told him nothing, except that the sky might fall on their heads.

[pathfinder]

JT et all, yes there is a VT or proximity fuze in artillery AND a time fuze both.

Been a long time since I been in an artillery unit but they both were in the US Army inventory last time I checked.

BTW I was in the US Army artillery so I might know what I am yakking about.

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unca pathy will show ya the path,

if only he could find it himself!

[Jager 7]

A lot of info on this thread...only some of it is correct.

VT fuze is what they used to call "proximity" fuze. It does respond to RF as it gets closer to the ground to detonate at a predetermined height above the ground. Old fuzes 20 meters above ground and current fuzes 7 meters above ground. It can be set to detonate upon impact but that would be a terrible waste of a very expensive fuze. Delay fuze is the fuze that detonates .05 of a second after impact. That means it would be underground when it detonates if it hits dirt. (To collapse trenches etc) It would also detonate at about ground level if it were fired into a forested area. Delay allows you to avoid tree bursts.

Mechanical Time fuze or Time is a "user adjustable" fuze where the FO calls in the up and down corrections and the fuze is then "dialed in" to achieve optimum height of burst above the ground. These are all fuzes not to be confused with shells. VT and Time are most often fitted to High Explosive (HE) rounds for casualty producing effects. Improved conventional munition (ICM) or more correctly Dual Purpose ICM is fitted with Mechanical Time Super Quick fuze. We still use VT, Time, Delay and of course Point Detonating (PD) fuzes.

Hope that helps.

Out here....

[kverdon]

If I recal correctly, the first use of "new" VT or radar proximity fuse in the ETO was during the Battle of the Bulge. Before that they had been forbidden to use them for fear of a dud shell falling into enemy hands. As pointed out, the air burst effect of these fuses was very effective against infantry. I think they used them earlier in the Pacific in the 5"38 AA guns. Worked pretty deadly to bring down night intruders.

Kevin

[Jager 7]

Kevin,

I believe you are correct about the first VT against ground targets being used during the Bulge. In the PTO it was during the battle for Okinawa, April thru June 45.

The nice thing about VT is that you do not have to adjust it to get an air burst like you do with Mechanical Time fuze. If you call for VT in effect you are almost guaranteed to get air bursts from the start.

Out here...