APPENDIX B: MAC
TM 9-2350-256-20
B2 MAINTENANCE FUNCTIONS-Continued
d. ADJUST To maintain or regulate, within prescribed limits, by bringing into proper position, or by setting the operating
characteristics to specified parameters.
e. ALINE To adjust specified variable elements of an item to bring about optimum or desired performance.
f. CALIBRATE To determine and cause corrections to be made or to be adjusted on instruments or test, measuring, and
diagnostic equipment used in precision measurement. Consists of comparisons of two instruments, one of which is a
certified standard of known accuracy, to detect and adjust any discrepancy in the accuracy of the instrument being
compared.
g. REMOVE/INSTALL To remove and install the same item when required to perform services or other maintenance
functions. "Install" may be the act of emplacing, seating, or fixing into position a spare, repair part, or module (component
or assembly) in a manner to allow the proper functioning of an equipment or system.
h. REPLACE To remove an unserviceable item and install a serviceable counterpart in its place. "Replace" is authorized
by the MAC and assigned maintenance level is shown as the third position code of the Source, Maintenance, and
Recoverability (SMR) code.
i. REPAIR The application of maintenance services 1 including fault location/troubleshooting, 2 removal/installation,
disassembly/assembly 3 procedures, and maintenance actions 4 to identify troubles and restore serviceability to an item
by correcting specific damage, fault, malfunction, or failure in a part, subassembly, module (component or assembly),
end item, or system.
j. OVERHAUL That maintenance effort (service/action) prescribed to restore an item to a completely
serviceable/operational condition as required by maintenance standards in appropriate technical publications (i.e., Depot
Maintenance Work Requirement [DMWR] ). Overhaul is normally the highest degree of maintenance performed by the
Army. Overhaul does not normally return an item to like-new condition.
k. REBUILD Consists of those services/actions necessary for the restoration of unserviceable equipment to a like- new
condition in accordance with original manufacturing standards. Rebuild is the highest degree of materiel maintenance
applied to Army equipment. The rebuild operation includes the act of returning to zero those age measurements (e.g.,
hours/miles) considered in classifying Army equipment/components.
B3 EXPLANATION OF COLUMNS IN THE MAC, SECTION II
a. COLUMN 1, GROUP NUMBER This lists functional group code numbers, the purpose of which is to identify
maintenance significant components, assemblies, subassemblies, and modules with the next higher assembly.
b. COLUMN 2, COMPONENT/ASSEMBLY This contains the item names of components, assemblies, subassemblies,
and modules for which maintenance is authorized.
1
Inspect, test, service, adjust, aline, calibrate, and/or replace.
2
The process of investigating and detecting the cause of equipment malfunctioning; the act of isolating a fault within a
system or unit under test (UUT).
3 The step-by-step breakdown (taking apart) of a spare functional group coded item to the level of its least component that
is assigned an SMR code for the level of maintenance under consideration (i.e., identified as maintenance significant).
4
Welding, grinding, riveting, straightening, facing, machining, and/or resurfacing.
B-2
