SECTION I TM 5-4310-250-24P (1) Source  Code.    The  source  code  tells  you how  to  get  an  item  needed  for  maintenance,  repair,  or overhaul   of   an   end   item/equipment.      Explanations   of source codes follows: Code Application/Explanation PA Stocked items; use the applicable NSN to PB request/requisition items with these source PC** codes.  They are authorized to the category PD indicated by the code entered in the 3d PE position of the SMR code. PF PG **Items coded PC are subject to deteriora- tion. KD Items with these codes are not to be re- KF quested/requisitioned individually.  They are KB part of a kit which is authorized to the maintenance category indicated in the 3d position of the SMR code.  The complete kit must be requisitioned and applied. MO-(Made at UM/ Items with these codes are not AVUM Level) to be requested/requisitioned individually.  They must be MF-(Made at IDS/ made from bulk material which AVUM Level) is identified by the part num- MH- (Made at IGS  ber in the DESCRIPTION Level) AND USABLE ON CODE (UOC) column and listed in ML-(Made at Spe- the Bulk Material group of the cialized Repair repair parts list in this RPSTL Act (SRA)) If the item is authorized to you by the 3d position code of the MD-(Made at Depot ) SMR code, but the source code indicates it is made at a higher level, order the item from the higher level of main- tenance. AO-(Assembled by Items with these codes are not UM/AVUM Level) to be requested/requisitioned individually.  The parts that AF-(Assembled by make up the assembled item IDS/AVIM Level) must be requisitioned or fabri- AH-(Assembled by cated and assembled at the IGS Category level of maintenance indicated by the source code.  If the 3d AL-(Assembled by position code of the SMR code SRA) authorizes you to replace the item, but the source code indi- AD-(Assembled by cates the item is assembled at Depot) a higher level, order the item from the higher level of main- tenance. 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 sal- vage, order it using the FSCM and part number given. XC - Installation drawing, diagram, instruction sheet, field service drawing, that is iden- tified by the manufacturer's part number. 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. NOTE:      Cannibalization   or   controlled   exchange, when  authorized,  may  be  used  as  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 700-42. (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 as follows: (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  one  of  the  following  levels  of maintenance. Code Application/Explanation C - Crew or operator maintenance done within unit maintenance or aviation unit main- tenance. O - Unit maintenance or aviation unit category can remove, replace, and use the item. F- Intermediate direct support or aviation in- termediate level can remove, replace, and use the item. H- Intermediate 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  the  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: 2