The FDC seldom receives much publicity. Pictures of it are of no comparison of those of the weapons in action. Although there are not as many personnel as are on the guns, their function is almost as vital to the effective application of artillery fire as is the ability of the weapons to hurl their rounds thousands of meters to a target.

FDC is essential

Without the firing data provided by the FDC, those rounds would seldom strike their intended targets, and artillery would revert back to its former status when it was used only against targets which could be seen from the guns.

Through studies and tests carried out over many years, the characteristics of the artillery weapons have been determined. All this information has been compiled and reproduced in the form of tables, graphs, and programs for a digital computer. That's right, a digital computer designated the Field Artillery Digital Automatic Computer or FADAC (to its friends just "Freddie"). Each battery has its own FADAC and fires using the data computed by it.

Charts, Maps. . .

Tables and graphs and even FADAC are not all the equipment utilized in the FDC. A map is required so that the altitude of the target may be obtained. The exact location of the target with respect to the battery is determined using the firing chart which has the battery located at its center and graphically presents all the ground covered by the range of the weapon in 1000 meter squares. From the firing chart the range and deflection from the battery to the target is determined.

All this equipment can be used to determine data which will send the rounds toward the target, but some more information is yet needed before really accurate fire can be obtained. How about the weather? Even an eight-inch howitzer round is affected by the wind. The flight of the rounds is affected also by the temperature, the density of the air and even the rotation of the earth.

Additional Factors

Other values which must be considered by FDC are the temperature of the propellant and the weight of the round itself. All these factors and others are considered when firing data is computed. The FADAC can figure it all out within seconds and determine the data which will place the rounds on target.

Manual computations, using the tables and graphs, take a little longer but must also be done in order to insure that "Freddie" was given the right information. Also, FDC has to be able to do its job even if the FADAC wasn't there.

The personnel in the FDC represent the duties which must be performed. Of course there must be a FADAC operator and someone to work the chart, called the chart operator or more technically the vertical control operator (VCO). Someone must talk to the outside world where the observer is so a radio-telephone operator (RTO) is needed.

In order to coordinate the actions of the other personnel and to compile the data they determine, an individual called "the computer" is required. Finally, activities of the FADAC operator, chart operator, RTO and computer are checked by the Fire Direction Officer (FDO) who is in charge of the FDC.

Since the FDC is a 24-hour operation, there must be two shifts thus identifying all those people who live and work in the now less mysterious bunker beneath the network of antennas.