Section I. INTRODUCTION
h. Replace. The act of substituting a serviceable
This appendix provides a summary of the maintenance
like-type part, subassembly, model (component or
operations for MD-921/G. It authorizes categories of
assembly) for an unserviceable counterpart.
maintenance for specific maintenance functions on
i. Repair. The application of maintenance services
repairable items and components and the tools and
(inspect, test, service, adjust, align, calibrate, replace) or
equipment required to perform each function. This
other maintenance actions (welding, grinding, riveting,
appendix may be used as an aid in planning
straightening, facing, remachining, or resurfacing) to
restore serviceability to an item by correcting specific
damage, fault, malfunction, or failure in a part,
subassembly, module / component/assembly, end item
Maintenance functions will be limited to and defined as
or system. This function does not include the trial and
error replacement of running spare type items such as
a. Inspect. To determine the serviceability of an
fuses, lamps, or electron tubes.
item by comparing its physical, mechanical, and/or
j. Overhaul. That periodic maintenance effort
electrical characteristics with established standards
(service/action) necessary to restore an item to a
b. Test. To verify serviceability and to detect
prescribed by maintenance standards (e.g., DMWR) in
incipient failure by measuring the mechanical or
appropriate technical publications. Overhaul is normally
electrical characteristics of an item and comparing those
the highest degree of maintenance performed by the
characteristics with prescribed standards.
Army. Overhaul does not normally return an item to like-
c. Service. Operations required periodically to
keep an item in proper operating condition, i.e., to clean,
k. Rebuild. Consists of those services/actions
preserve, drain, paint, or to replenish fuel
necessary for the restoration of unserviceable equipment
lubricants/hydraulic fluids or compressed air supplies.
to a like-new condition in accordance with original
manufacturing standards. Rebuild is the highest degree
d. Adjust. Maintain within prescribed limits by
of material maintenance applied to Army equipment.
bringing into proper or exact position, or by setting the
The rebuild operation includes the act of returning to zero
operating characteristics to the specified parameters.
those age measurements (hours, miles, etc.) considered
e. Align. To adjust specified variable elements of
in classifying Army equipment/components.
an item to about optimum or desired performance. in f.
Calibrate. To determine and cause corrections to be
made or to be adjusted on instruments or test measuring
a. Column 1, Group Number. Column 1 lists group
numbers, the purpose of which is to identify components,
measurement. Consists of the comparison of two
assemblies, subassemblies and modules with the next
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. Install. The act of emplacing, seating, or fixing
into position an item, part, module (component or
assembly) in a manner to allow the proper functioning of