Thursday, September 19, 2013


The reason this blog is called "Graphic Firing Table" is because when I started it I was an artilleryman in the Oregon National Guard.

I explained back then what a GFT was and what it did, and it seemed like a good sort of title for something like a blog that delivers opinions and ideas like projectiles into the aether. I didn't talk about the other form of manual fire direction computation (as opposed to an actual computer, which was then and now the primary method of fire direction in use in the U.S. Army); this is a "Tabular Firing Table" or TFT, simply a book that contains table after table of information; this stuff includes things like corrections for wind, atmospheric pressue, temperature, elevation differences between the gun and the target, and barrel wear.

Eventually you get to "Table F", which, depending on projectile type, fuze type, and charge provides an elevation for the gun barrel and a setting for the fuze.

Anyway, the point of this post is that right now I'm reading the last of Rick Atkinson's "Liberation Trilogy", Guns at Last Light, and came across this bit of history buried in his discussion of the autumn battles along the German frontier:
"The shortfall partly reflected the inability of U.S. plants to meet demand: a 155mm shell required forty separate manufacturing procedures. The more common 105mm howitzer ammunition was produced and shipped under twelve hundred different lot numbers, each with minor variations in propellant that affected accuracy. (First Army was to spend 25,000 man-hours in the early fall sorting jumbled ammunition to avoid catastrophic short barrages."
I was horrified when I read this.

One of the first things you get hammered into you when you learn fire direction is that you have to know the characteristics of your projectile and propellant. Changes in ammunition type, changes in fuze type, changes in propellant type can all have enormous effects on the point of impact of the round. Shoot a high explosive round using gun data calculated for an illumination round and you might sail hundreds of meters beyond your plotted target; shoot an HE round on data calculated for a white phosphorus round and it impacts tens or hundreds of meters short. Same with propellant. One lot might send the round 10% further than another, a third 10% less.

This is the great advantage of the modern ballistic computer. It can store data from hundreds of ammunition lots, freeing the fire direction crew from having to sort through all that shit.

But in 1944 the battery FDC's didn't have a computer. They had a bunch of guys, a chart board, and a bunch of TFTs.

The idea of trying to sort out twelve hundred individual ammo lots?

Gah. Gives me the shivers just thinking about it.

Anyway, the Atkinson book is damn good, worth a read for anyone interested in the period and the command and control issues of the Allied advance on Germany through Western Europe. Not a tactical primer but terrific on limning the times and peoples and giving you a sense of what happened and why.


mike said...

Thanks for the tip on Atkinson's book Chief. I'll pick up a copy. I did read and like his first two on North Africa and Italy. But have been debating with myself about buying the third. Thinking that did I really want to read again about what Beevor, Ryan, Hastings, and D'Este have already covered?

But Atkinson does have an eye for detail that many others have missed. So I'll bite the bullet and give him and his publisher some bucks.

FDChief said...

My copy came through the public library. I like Atkinson's work but not enough to shell out for the hardcover. I'll wait 'til it comes out in paperback if I decide to buy it...

Ael said...

I think they also had plotters and GFTs in those days.

Certainly the ones I trained with looked like they were WWII surplus.

FDChief said...

I know that the FDCs of the time used plotting boards to get deflection data. The post was discussing the problems inherent in having all those propellant lots, though, and the inaccuracies produced by propellant variations are primarily that of range rather than deflection.

And I assume that if not in 1941 at least soon after some smart guy at Sill produced a GFT. The slipstick was the mechanical computer of the day, and a computer was the obvious next step for fire control.

The interesting thing to me about WW2 is that the U.S. was the ONLY field artillery branch to develop fire direction above the battery level. The notion of battalion and higher FDCs was a purely U.S. development. Almost every history of WW2 talks about the devastation of the time-on-target missions involving FA units up to corps level, and you can do with without a pretty damn slick FDC.

FDChief said...

I should note, though, that I was taught that of there was EVER a question that the TFT was the "final authority"; the data in the TFT was the basis for the GFT, and that, like any transcription, there was always the possibility of error.

Ael said...

I am not sure what you mean by fire direction above the battery level.

As you say, everyone did time on target missions with massed artillery, so what part of fire direction did they not do at brigade or divisional level?

FDChief said...

That's just the thing; the rest of the combatants couldn't do that - they were still mostly doing the WW1 pre-planned fires for everything above the battery level; there was no technical fire direction at battalion level and above - everything was tactical above battery.

That is, British, German, and Soviet FA units could deliver the equivalent of a time-on-target mission for pre-plotted targets issued to them by division-and-above level headquarters. The maneuver commander would tell them "we need to attack A at 0600 and shift to B at 0800 and from there conduct a rolling barrage to C at 10 meters a minute." Then the batteries would work out firing data and apply it.

The difference was that the U.S. FA could shoot "adjust fire" TOT missions as "on-call" fires to respond to tactical emergencies. The other nations' FA units couldn't do that; they had to issue the tactical instructions to the FA units and then the individual batteries would compute the data.

In practice it was almost impossible for the other Allies or the Germans to mass on-call fires as the U.S. did.

FDChief said...

Here's a pretty good summary of WW2 FA capabilities:

Ael said...

The Canadians(and hence the British as we followed their doctrine) could and did respond with a division's worth of guns onto an emerging tactical target. Furthermore, it could be done in a couple of minutes. The FOO would basically order fire at a certain map coordinate and every battery would compute it's own data and pull the lanyard at the appropriate second.

At least that is what I recall on old BRA telling me.

FDChief said...

The Commonwealth forces had developed a very close capacity by 1944, but as you note, the technical fire direction was still done at the battery level. It had almost an identical effect, but the mechanics were still different.

Pretty much all the developed nations have now gone to the U.S.-type system where technical fire control is centralized as high as corps. With AFATADS often the battery FDCs are no more than spectators whose job it is to double-check the gun data. The digital link between the Division and even Corps FSE goes directly to the individual gun data units and the controlling FSE's computer even fires the individual cannons.

I never learned to like that; it was frankly creepy to be sitting inside the FDC rig waiting for the firing command and all you'd get would be a buzzing from the BCS computer that indicated that the command was passing through our system and then you'd hear the cannons firing. I always felt pretty useless.

But it produces pretty devastating effects on target.

Anonymous said...

Chief I bought the first of Atkinson's books but felt it was a pale shadow of Here is Your War and Brave Men by Ernie Pyle. Two classics. My copies are 60 plus years old and falling apart in the tropics here in Taiwan. James

Dane900 said...

I know this isn't the most mature response, but I'm on-again off-again into Warhammer 40k, and I burst out laughing at the nightmare you laid out above, thinking about the extra tables you'd need to account for the wildly different gravity and atmospheres you'd encounter on different planets. Cock-ups would be more common than actual successes, which of course fits perfectly with the setting. Still, amazing to think what it took for your guys to be able to lay some emergency ordnance down on demand like that. That's a side of the war I hadn't really heard about before.