TM-9-2350-311-10
HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5
TECHNICAL MANUAL; OPERATOR’S MANUAL
NOVEMBER 1994
TM-9-2350-311-10 - Page 504 of 775
TM 9-2350-311-10
3-7 FIRE CONTROL ALINEMENT TESTS AND MEASUREMENTS — CONTINUED
3-7.6
M117/M117A2 Panoramic Telescope Reliability Testing — Continued
a. Testing Reliability of Defections — Continued
5 Record the reading on the azimuth counter (7). Reset the reset counter (8) to 3200.
NOTE
If you pass the reference point on the second revolution in step 4, rotate the M117/M117A2
panoramic telescope at least 50 mils in the opposite direction (counterclockwise) and
reapproach the reference point from left to right. This is done to eliminate induced backlash.
6 Turn the azimuth knob (9) in a clockwise direction until you have rotated the M117/M117A2 panoramic
telescope (1) through two complete revolutions of the head and returned to the reference point (6).
NOTE
If recorded readings do not appear in steps 7, 8, and 9, the M117/M117A2 telescope is out of
adjustment and should be reported to unit maintenance.
7 The reading on the azimuth counter (7) should be the same as that recorded at the start of the test
within ± 1 mil. If not, notify unit maintenance.
8 The reading on the reset counter (8) should be 6000 ± 1 mil. If not, notify unit maintenance.
9 The reading on the gunner’s aid counters (5) should still be at 0. If not, notify unit maintenance.
b. Testing Reliability of Special Corrections
1
Center the cross-level (3) and pitch level (4) bubbles of the M145/M145A1 telescope mount (2).
NOTE
• A parallax shield can be made to prevent eye movement in two ways. One is to use a dust
cap with a pin hole in the center. The second way is to use a small opening marked off with
strips of tape.
• If the reference point is less than 55 yards (50 m) away, use a parallax shield.
2 Look through the eyepiece (10) and sight on a reference point (6) at least 55 yards (50 m) away.
3 Record the reading on the azimuth counter (7). Reset the reset counter (8) to 3200.
4 Turn the gunner’s aid knob (11) to insert 10 mils into the left gunner’s aid counter (5).
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