COAST ARTILLERY, JOURNAL - Air Defense Artillery

MORTAR FIRE CONTROL 505
b. In this connection it should be noted that the determination of
a predicted point in Case III fire is prescribed in T. R. 435-221, "Fire
Control and Position Finding." In peace time training the use of a
predicted point in a thorough check-back system is useful. This practice
does, however, impose additional labor upon the plotting details
and others concerned with the application of predicted point data.
In action it is to be questioned whether these operations should be required.
The chief value of this practice in action would be to check the
orientation of the fire control system. Once this orientation had been
checked by use of several predicted points it appears desirable to discontinue
the determination and use of pred.icted point data, thus simplifying
the operation of the fire control system. It is the opinion of the
Coast Artillery Board that the determination and use of predicted point
data should be made optional by T. R. 435-221 provided a suitable
check-back system is in use by the batteries. It should be noted in this
r.egard that the setforward azimuth at target practices could be utilized
satisfactorily by safety officers.
7. In the system developed at Battery Anderson predictions were
made every thirty seconds. A dead time interval of one minute was
used. Firing data for a point midway between the latest two predictions
were obtained by interpolation on the range percentage corrector
for elevation and on the deflection board for azimuth. The data for
the end of the next fifteen and thirty seconds were displayed to the pits
on every half-minute bell by the operators of a special display board.
The time-interval system rang three bells on the minute and half-minute
and two bells at fifteen seconds and forty-five seconds. The operator
of the deflection board was connected by telephone to one of the special
display board operators and the operator of the range percentage corrector
to the other operator. It will be seen that the system, as developed,
deviates hut little from the standard system and possesses all
the required flexibility.
B-THE FIRE CO!'iTROL EQUIPME!liT WITH COC\"SIDER...\TIO~S
FOR THE IMPROVRME:"iT THEREOF
8. The following equipment was used in the plotting room:
a. Plotting Board.-A new Cloke Plotting Board, Model of 1923,
obtained from Frankford Arsenal Yiasused in some practices; the lIO°
Plotting Board, Model of 1915, in other practices. Both Yiere satisfactory.
The operation of the boards is described in T. R. 435-221.
b. Prediction Device.-The Wells predictor and the pantograph predictor
were tested by the plotting section at drill. Either of them Yiould
have been satisfactory. The plotting detail had become accustomed
to the use of a prediction scale in conjunction with a device for deter-