TM 5-5420-280-23&P
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MAINTENANCE FUNCTIONS (Contd)
6. 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.
7. Remove/Install. To remove and install the same item when required to perform service 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.
8. 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.
NOTE
The following definitions are applicable to the repair maintenance
function:
Services -- Inspect, test, service, adjust, align, calibrate, and/or replace.
Fault location/troubleshooting -- 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).
Disassembly/assembly -- 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).
Actions -- Welding, grinding, riveting, straightening, facing,
machining, and/or resurfacing.
9. Repair. The application of maintenance services, including fault location/troubleshooting,
removal/installation, disassembly/assembly procedures, and maintenance actions 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.
10. 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. Overhaul is normally the highest degree of maintenance performed by the Army. Overhaul
does not normally return an item to like-new condition.
11. 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.
EXPLANATION OF COLUMNS IN THE MAC
Column (1) Group Number. Column (1) lists Functional Group Code (FGC) numbers, the purpose of
which is to identify maintenance significant components, assemblies, subassemblies, and modules with the
Next Higher Assembly (NHA).
Column (2) Component/ Assembly. Column (2) contains the item names of components, assemblies,
subassemblies, and modules for which maintenance is authorized.
Column (3) Maintenance Function. Column (3) lists the functions to be performed on the item
listed in column (2). (For detailed explanation of these functions refer to Maintenance Functions outlined
above.)
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