September-October - Air Defense Artillery

~ AAA NOTES No. 22, ETa
Subject: Azimuth and E]evation Indicators for 40mm pointers when using director control. (See Figure 3, B.)
Gun. By making one master scale and photostating, a complete
~ Source: AA Section, Headquarters, Twelfth Army battalion can be supplied with the necessary materials with
Group. on]ya few hours work.
a. In order to utilize the 40mm gun for unseen fire in
groundroles, AAA barrage fire, or to anticipate the direccionof
approach of enemy aircraft as reported by early
waming, it is necessary to have some means of laying the
'eapon in true azimuth and elevation. Since directors are
notnorma ]] y used by AAA A\V units wit h corps and divi-
sions,other methods must be used to accomplish this. Sev-
era]AAA units of Twe]fth Army Group have devised field
~ expedients for this purpose.
l b. (1) B]ackout Dia] Azimuth Indicator: (a) A simple
"~ethodof setting the 40mm gun in azimuth by converting
,[he b]ack] 'out dia into an azimut h indicating dia] has been (c) To mount the scale, first remove the glass cover and
h b I
rim of t e lackout dia , being careful not to damage the
waterproofing jacket. Next, attach the circular scale to the
outer dial with rubber mounting cement. Cut a small refer-
f
ence pointer rom a piece of light metal, painted black, and
h f h ]
att3c to one 0 t e setscrews ho ding the Q:]assin the un-
d ~
erneath side of the lens and rim; the pointer is to remain
stationary in the 12 o'clock position.
Cd) In order to orient, boresight the gun on a true north
stake, push in the clutch on the instrument, rotate the dial
until the reference pointer reads zero, then release the
clutch.
de\'isedby Lt. Col. James D. Caulk, Executive Officer of (e) The blackout dial azimuth scale will indicate azithe
II th AAA Group. The blackout dial remains in posi- muth accurately to the nearest 20 mils, or approximately one
tionon the gun even though directors are stored, and the degree. This is sufficiently accurate for AAA barrage firing
,addedconversion feature does not interfere with the opera- and early warning purposes, but unsuitable for unseen fire
Itionof the instrument if required later for use with director. at ground targets, which requires greater accuracy. The
(b) Since the outside movable disc in the dial (See Figure principal advantages of this type scale are simplicity of con-
3, A) makes one complete revolution as the gun is traversed struction and noninterference with normal operation of
through 360
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