Section II DESCRIPTION AND DATA

9-1290-232-34&P

D E S C R I P T I O N AND DATA

S e c t i o n Il.

PHYSICAL

DESCRIPTION

1-3.

The

Elevation

Fire

Control

Quadrants

M13A1,

M13A1C,

M13A3

and

M13B1

are

used

with

the

indirect

fire control system to show how much the weapon is elevated or depressed.

T h e quadrant is made up of an elevation knob and worm shaft, elevation micrometer, level vial tube,

reflector (except the M13A3), and elevation scale. The quadrant is used for laying the weapon in

elevation or depression during indirect fire.

The scale dial (1) is divided into 100-mil increments from minus 200 to plus 600 mils. An elevation

k n o b (2) with a micrometer attached is used to set in elevation or depression angles. A micrometer scale

(3), attached to the elevation knob is divided in 1 mil increments from 0 to 100 mils on two scales which

a r e read in opposite directions. The inner scale (black numbers) is used when setting elevation angles.

T h e outer scale (red numbers) is used when setting depression angles. The scale index (4) and level vial

t u b e (5) are mounted on the housing (6). When the elevation knob (2) is turned, the housing (6) turns

a n d moves the level vial bubble (7) off center. When the weapon has been elevated or depressed enough

to put the level vial bubble (7) back in the center, the elevation scale (1) shows the elevation or

d e p r e s s i o n angle of the weapon. Movement of the weapon is sent through linkage to the ballistic drive or

t h e gun recoil guard where the quadrant is mounted. A reflector set at a 45 degree angle over the level

v i a l tube (5) (except M13A3) allows easy viewing of the level vial tube (5) which is above eye level of

tank personnel.

II-1-2