TM-9-2350-311-20-2
HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5
TECHNICAL MANUAL; UNIT MAINTENANCE MANUAL FOR CAB, ARMAMENT, SIGHTING AND FIRE CONTROL, ELEVATING AND TRAVERSING SYSTEMS AND ASSOCIATED COMPONENTS
DECEMBER 1993
TM-9-2350-311-20-2 - Page 39 of 828
TM 9–2350–311–20–2
1–8
Section II.
EQUIPMENT DESCRIPTION AND DATA
1–13 EQUIPMENT CHARACTERISTICS, CAPABILITIES, AND FEATURES
The self-propelled medium howitzer is air transportable. The cab receives electrical power from the batteries and transmits
this electrical power to components throughout the 6400 mils traverse by means of 3 or 5 contact arm assemblies. The cab
power pack and accumulator provide cab hydraulic power. The NBC system (on M109A4/M109A5 howitzers) provides
protection to crew members in a nuclear, biological, or chemical environment.
The cab supplies elevation and azimuth control for the 155mm cannon assembly. Refer to TM 9–2350–311–10 for operator’s
instructions.
An electrically driven hydraulic pump supplies power for the elevation and depression of the cannon assembly, for opera-
tion of the projectile rammer and for traversing the cab. The elevation and cab traversing systems also have manual
backup capabilities.
The primary armament for the howitzer is a 155MM cannon assembly. The secondary armament is a caliber 50 machine gun.
1–14 LOCATION AND DESCRIPTION OF MAJOR COMPONENTS
Refer to para 1–14.1 for location of major components inside the howitzer cab. Refer to para 1–14.2 for location of major
components on the
outside of the cab.
1–14.1
Location and Description of Major Internal Components
a.
Rammer Assembly. The rammer assembly (1) is weapon mounted and hydraulically powered, with positive ram. Its
two positions are stow and ram.
b.
Traversing Mechanism. The traversing mechanism (2) is hydraulically operated but has a manual backup in case of
system failure. The M109A2/M109A3 howitzers have automatic electric clutches, while the M109A4/M109A5 howit-
zers have hydraulic clutches. The traversing mechanism allows the cab to traverse at 6400 mils.
c.
Sighting Equipment-Optical Sighting Equipment. The sighting equipment (3) can be adjusted for cant and provides
capability for direct or indirect fire (direct not shown).
d.
Equilibrated Elevating Cylinder. The equilibrated elevating cylinder (4) provides elevation and depression for cannon
assembly.
e.
NBC System (M109A4/M109A5 Howitzers). M2A2 air purifier (5) provides filtered air to the M3 electrical air heaters
(6). Each station has its own M3 electrical air heater to control temperature for personal comfort. Hoses connect M2A2
air purifier to M25A1 masks.
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