Functional Groups

TM 55-4920-431-13

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.

A-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.

A-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.

A-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.

A-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.

A-4