COAST ARTILLERY, JOURNAL - Air Defense Artillery

"77 ROUNDS FIRED, SIR" 531
inches. Below this he constructed a scale of angular heights in mils
against velocity of wind in miles per hour. The operation was as
follows: Knowing the altitude at which wind data was desired the
operator read from the first scale the time of ascension corresponding
to that altitude. A balloon was then inflated to twenty-four inches,
using a previously constructed wire hoop as a gauge, and released immediately
above an oriented instrument, which in this case was the
A. A. Telescope. At the end of the required time of observation the
azimuth and angular height of the balloon were read and recorded.
Opposite that angular height on the lower scale of the chart the operator
then read the velocity of wind and converted the azimuth of
balloon into azimuth from which the wind was blowing. The results
obtained appeared to he sufficientlyaccurate as the mils effect on deflection
checked very closely with that indicated by firing table values for
such a wind.
The graphical solution recently recommended by the Coast Artillery
Board (Project No. 415) was used both for calibration and for
trial shots before firing at towed target. This method gave the hattery
commander an excellent picture of the results of his firing and was
much more rapid than any solution previously suggested. The computation
was speeded up by having prepared beforehand a table showing
the products of various altitudes times the cotangents of various
angular heights, in other words, horizontal ranges. Having measured
the altitude and angular height to trial shot, the horizontal range was
read from the tahle and the burst quickly plotted. Having also prepared,
previous to firing, the desired section of the trajectory chart on
an enlarged scale the battery commander was able to plot his trial
shots, compute his corrections and have them set while the plane gained
its altitude. He could then open fire as soon as the target appeared
on the course, thus more nearly simulating service conditions.
During preHminary firing the regimental commander made frequent
flights in a second plane to ohserve the results heing ohtained
and on one occasion a Reserve battery commander fired a complete
practice "on his own," meanwhile permitting the regular battery commander
to observe the firing of his battery from the air.
Another unusual feature of the night firing was the illumination of
the target by hand flashlights wired in the mouth of the sleeve, an idea
which originated with one of the Air Corps officers. All who have witnessed
night antiaircraft firings remember the hours wasted while
searchlights endeavored to pick up the small sleeve trailing 1800 feet
behind and several hundred feet below the towing plane. By pointing
one flashlight back into the white sleeve, and two to the front, the
target could be seen on clear nights at an altitude of 6800 feet. 1\0