TM-9-2350-311-10 M109 Operator's Manual for M109A2, M109A3, M109A4 and M109A5 Download
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TM 92350-311-10 1–12 DIFFERENCES BETWEEN MODELS NOTE When requesting support maintenance, properly identify the configuration of the vehicle on which work needs to be done in order to obtain the correct repair parts. Unlike the M109A2 production model, the M109A3 is converted from an M109A1 model with a series of product improvement kits. Also some M109A2 and M109A3 howitzers have been converted to an M109A4 model with product improvement kits. M109A5 models have been converted exclusively from M109A4 models. In addition to all M109A4 updates, the M109A5 model also modifies the M185 cannon assembly to an M284 cannon assembly and M178 mount to an M182 mount. Below are some differences important to operator/crew. a. b. c. d. e. f. g. h. i. j. Commander’s cupola. On earlier design vehicles, the cupola can be opened from both the inside and outside. On later design vehicles, the cupola can be opened only from the inside. Some earlier design vehicles allow rotation of the cupola by loosening a ring lock, On later design vehicles, the cupola can be rotated by pulling out a latch and by placing the latch into one of ten notches to hold the cupola in position. Gunner’s escape hatch. On later design vehicles, the gunner’s escape hatch is opened by pushing a knob and turning a handle. On some early design vehicles, the gunner’s escape hatch does not have a knob. To open hatch just turn the handle. Contact arm assemblies. Some M109A3 vehicles have three and some vehicles have five contact arm assemblies, AH M109A2/M109A4/M109A5 howitzers have five electrical contact arm assemblies. Machine gun mount, All M109A2 and some M109A3 howitzers require an arm adapter to lock the machine gun mount to the support assembly. M109A3 howitzers with the early machine gun mount design do not require the arm adapter, Protective shields, race ring. Some M109A3 howitzers do not have a turret shield behind the commander’s seat. Commander’s seat handle latch. Some early design vehicles have a short handle on the commander’s seat assembly, and some vehicles have a long handle. Driver’s instrument panel. Some vehicles have covers over the gages on the driver’s instrument panel. NBC system. NBC system is provided on M109A4/M109A5 howitzers only. Driver and cannoneer no. 2 have an M2A2 air purifier and M3 electrical air heaters mounted in hull portion of vehicle. An M2A2 air purifier and four electrical air heaters are mounted in the cab for the rest of the crew members. NBC MOPP gear stowage is provided in new cannoneer seats and stowage boxes. Traversing mechanism and clutch valve. The traversing mechanism is operated with a hydraulic clutch in M109A4/M109A5 howitzers instead of an electric clutch as in M109A2/M109A3 howitzers, A clutch valve with an override lever is also provided in M109A4 models and M109A5 models for power traversing cab in the event of an electrical failure to the clutch valve solenoid. Power pack assembly. M109A4/M109A5 howitzers have two external hydraulic filters. M109A2/M109A3 howitzers have an internal hydraulic filter. 1-18