Figure 14-24.--Plotting board and carrying case.
Correction factor is
of his entire unit. The FDC is normally located at or near
the firing position and maintains contact with the guns
by use of wire communications. Calls for fire are
reported from all sources directly to the FDC where the
For example, suppose the distance from the
targets are plotted on the firing chart (plotting board).
observer to the target is 1000 meters, the gun-target
From this chart, firing data is prepared by the computer
distance is 1200 meters, and the deviation of the burst
(a member of the FDC) and announced to the mortar
from the target as read by the observer is 60 mils. The
crews as fire commands. The FDC can be operated by
correction factor is
the computer alone; however, it is desirable to include a
radiotelephone operator, so the computer can be
dedicated to computing firing data and issuing fire
commands.
The change in deflection equals
PLOTTING BOARD
In this method, you should round off distances to the
The M17 plotting board is a fire-control instrument
nearest 100 meters for simplicity and speed of
that helps in computing firing data by providing the
computation.
range and direction from the mortar position to the
target. The M17 plotting board is sturdy, easy to operate,
FIRE DIRECTION CENTER
accurate, and suitable for use in the field under adverse
PROCEDURES
atmospheric conditions. The plotting board consists of
a pivoted disk of transparent plastic and a removable
range scale arm, both attached to a flat base grid. The
The FDC is located in the headquarters section of
M17 plotting board is carried in a durable nylon case, as
the mortar platoon. Through the FDC, the platoon
commander is able to control and quickly mass the fire
shown in figure 14-24.
14-19