6. Calibrate. To determine and cause corrections to be made or to be adjusted on instruments of test, measuring and
diagnostic equipment used in precise 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
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.
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.
The following definitions are applicable to the "repair" function.
Services -- Inspect, test, service, adjust, align, calibrate and/or replace.
Fault location/troubleshooting -- The process of investigating and detecting the cause of
equipment malfunction; 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 a 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.
10. Overhaul. That maintenance effort (service/action) prescribed to restore an item to a completely service-
able/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
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 numbers, the purpose of which is to identify
maintenance significant components, assemblies, subassemblies, and modules to 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.)
Column (4) -- Maintenance Level. Column (4) specifies each level of maintenance authorized to perform each
function listed in column (3) by indicating work time required (expressed as man-hours in whole hours or decimals)
in the appropriate subcolumn. This work-time figure represents the active time required to perform that maintenance