XA - Do not requisition an "XA"-coded item. Order its next higher assembly. (Also, refer to the NOTE below.)
XB - If an "XB" item is not available from salvage, order it using the FSCM and part number given.
XC - Installation drawing, diagram, instruction sheet, field service drawing, that is identified by manufacturer's
XD - Item is not stocked. Order an "XD"-coded item through normal supply channels using the FSCM and part
number given, if no NSN is available.
Cannibalization or controlled exchange, when authorized, may be used as a source
of supply for items with the above source codes, except for those source coded
"XA" or those aircraft support items restricted by requirements of AR 750-42
(2) Maintenance Code. Maintenance codes tell you the level(s) of maintenance authorized to USE and
REPAIR support items. The maintenance codes are entered in the third and fourth positions of the SMR code
(a) The maintenance code entered in the third position tells you the lowest maintenance level
authorized to remove, replace, and use an item. The maintenance code entered in the third position will
indicate authorization to the following levels of maintenance.
C - Crew or operator maintenance done within organizational or aviation unit maintenance.
O - Organizational or aviation unit category can remove, replace, and use the item.
F - Direct support or aviation intermediate level can remove, replace, and use the item.
H - General support level can remove, replace, and use the item.
L - Specialized repair activity can remove, replace, and use the item.
D - Depot level can remove, replace, and use the item.
(b) The maintenance code entered in the fourth position tells whether or not the item is to be repaired
and identifies the lowest maintenance level with the capability to do complete repair (i.e., perform all authorized
repair functions). NOTE: Some limited repair may be done on an item at a lower level of maintenance, if
authorized by the Maintenance Allocation Chart (MAC) and SMR codes. This position will contain one of the
following maintenance codes.
O - Organizational or (aviation unit) is the lowest level that can do complete repair of the item.
F - Direct support or aviation intermediate is the lowest level that can do complete repair of the item.