TM   55-4920-410-13&P any  single  maintenance  function  (e.g.,  test,  repair), then the higher maintenance level(s) that can accom- plish additional tasks will also be indicated. c. A maintenance function assigned to a maintenance level  will  automatically  be  authorized  to  be  performed at any higher maintenance level,. d.  A  maintenance  function  that  cannot  be  performed at  the  assigned  level  of  maintenance  for  any  reason may  be  evacuated  to  the  next  higher  maintenance organization. Higher maintenance levels will perform the  maintenance  functions  of  lower  maintenance  levels when  required  or  directed  by  the  appropriate  com- mander. e. The assignment of a maintenance function will not be construed as authorization to carry the associated repair  parts  in  stock.  Authority  to  requisition,  stock,  or otherwise  secure  necessary  repair  parts  will  be  as specified  in  the  repair  parts  and  special  tools  list appendix. f.  Normally  there  will  be  no  deviation  from  the assigned level of maintenance. In cases of operational necessity, maintenance functions assigned to a main- tenance  level  may,  on  a  one-time  basis  and  at  the request of the lower maintenance level, be specifically authorized by the maintenance officer of the level of maintenance  to  which  the  function  is  assigned.  The special  tools,  equipment,  etc.  required  by  the  lower level of maintenance to perform this function will be furnished by the maintenance level to which the func- tion is assigned. This transfer of a maintenance func- tion to a lower maintenance level does not relieve the higher maintenance level of the responsibility of the function.  The  higher  level  of  maintenance  will  provide technical  supervision  and  inspection  of  the  function being performed at the lower level. g. Organizational through depot maintenance of the US  Army  Electronics  Command  equipment  will  be performed by designated US Army Electronics Com- mand personnel. h. Changes to the MAC will be based on continuing evaluation and analysis by responsible technical per- sonnel and on reports received from field activities. B-3.  DEFINITIONS. a. Inspect.  To determine  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 B-2 characteristics of an item and comparing those charac- teristics 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. Align. 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 ronment such as an emplacement, site or vehicle. h.  Replace.  To  replace  unserviceable  items serviceable  assemblies,  subassemblies  or  parts. envi- with 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, inspec- tion, cleaning, preserving, adjusting, replacing, weld- ing,   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 manu- facturing  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