COAST ARTILLERY, JOURNAL - Air Defense Artillery

MORTARFIRE CONTROL 509
1924, COASTARTILLERYJOURNAL.Predictions for firing one minute
ahead were made every thirty seconds. The operation of the plotting
board was normal. The operation of the Range Correction Board, Impact
Board, Spotting Device, Wind Component Indicator, and prediction devices
was as usual; the operation of the range percentage corrector, deflection
board, and mechanical display board but slightly varied. The
detailed operations of these devices are described in T.R. 435-221, "Fire
Control and Position Finding," the report on Coast Artillery Board Project
No. 75, and references contained in that report. It will be.seen that
only in frequency of prediction and in interpolation between predictions
was there any material change from the present system.
12. For the Coast Artillery Board Universal Deflection Board, with
interpolator, two operators, A and B, were required. A, connected by
telephone to the azimuth operatOl" of the special display boards in
each pit, set the uncorrected azimuth of the setforward point. B set the
slide of the deflection board at the intersection of the proper cross
wind and drift curve with the line corresponding to the corrected elevation.
A then read the corrected azimuth of setforward point and telephoned
it to the pits; while he was doing this he was also interpolating
and he next read the interpolated azimuth and telephoned it to the
pits. A applied any azimuth corrections ordered. NOTE.-In changing
zones no interpolation was or could be made.
13. In the pit the two operators of the special display board were
stationed in rear of the board. Each was equipped with chalk and an
eraser. They were men selected for ability to make legible figures. It
will be noticed in Figure 1 that the spaces for data on the two sides of
the revolving blackboard were echeloned sp as to minimize interference
when men were writing data simultaneously. The operators will be
designated in this discussion as C and D. C recorded zone and elevation
and was connected to operator of range percentage corrector interpolator.
D recorded azimuth and was connected to operator A of paragraph
12, above. As noted, the time interval bell rang three times on
the minute and half-minute intervals and two times at fifteen seconds
and forty-five seconds. With sufficient training, all of the operations
within the range section, including the posting of data on the special
display hoard in the pit, can be completed on an average of twenty-five
seconds after the three bells on which each prediction is begun. The
special display board was turned to the pit exactly on the third note
of the three bells following the three bells on which the prediction
began, or about five seconds after the data were posted. Data received
by C and D provided for laying the mortar on the next but one ringing
of three bells, and these data were displayed thirty seconds in advance
of firing tillie by turning the board on the next 3-bell ring. Before