TM 55-4920-431-13
h. Changes to the MAC till be based on continuing evaluation and analysis by responsible technical personnel
and on reports received from field activities.
B-3. DEFINITIONS.
a. Inspect. To detemine serviceability of an item by comparing its physical, mechanical and electrical
characteristics with established standards.
b. Test. To verify serviceability and detect incipient failure by measuring the mechanical or electrical
characteristics of an item and comparing those characteristics with prescribed standards.
c. Service. To clean, to preserve, to charge, and to add fuel, lubricants, cooling agents and air.
d. Adjust. To rectify to the extent necessary to bring into proper operating range.
e. Aline. To adjust specified variable elements of an item to bring to optimum performance.
f. Calibrate. To determine the corrections to be made in the readings of instruments or test equipment used in
precise measurement. Consists of the comparison 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 or test equipment being
compared with the certified standard.
g. Install. To set up for use in an operational environment such as an emplacement, site or vehicle.
h. Replace. To replace unserviceable items with serviceable assemblies, subassemblies or parts.
i. Repair. To restore an item to serviceable condition through correction of a specific failure or unserviceable
condition. This includes, but is not limited to, inspection, cleaning, preserving, adjusting, replacing, welding,
riveting, and strengthening.
j. Overhaul. To restore an item to a completely serviceable condition as prescribed by maintenance
serviceability standards prepared and published for the specific item to be overhauled.
k. Rebuild. To restore an item to a standard as nearly as possible to the original or new condition in
appearance, performance, and life expectancy. This is accomplished through the maintenance technique of
complete disassembly of the item, inspection of all parts or components, repair or replacement of worn or
unserviceable elements (items) using original manufacturing tolerances and specifications, and subsequent
reassembly of the item.
B-4. FUNCTIONAL GROUPS. Standard functional groupings are not considered feasible for aviation ground
support equipment due to variation and complexity. Therefore variations to functional groupings may occur.
B-5. MAINTENANCE CATEGORIES AND WORK TIMES. The maintenance categories (levels) AVUM,
AVIM, AND DEPOT are listed on the Maintenance Allocation Chart with individual columns that indicate the
work times for maintenance functions at each maintenance level. Work time presentation such as 0.1 indicate the
average time it requires a maintenance level to perform a specified maintenance function. If a work time has not
been established, the columnar presentation shall indicate "-". Maintenance levels higher than the level of
maintenance indicated are authorized to perform the indicated function.
B-6. TOOLS AND TEST EQUIPMENT (Section III). Common tool sets (not individual tools), special tools, test
and support equipment required to perform maintenance functions are listed alphabetically with a reference
number to permit cross-referencing to column 5 in the MAC. In addition, the maintenance category authorized to
use the device is listed along with the item National Stock Number (NSN) and, if applicable, the tool number to
aid in identifying the tool/device.
B-7. REMARKS (Section IV). Remarks contained in column 6, with an alphabetical code, are listed to provide a
ready reference to the definition of the remarks.
B-3
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