TM 55-4920-413-13&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 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 envi- ronment such as an emplacement, site or vehicle. h.  Replace.  To  replace  unserviceable  items  with serviceable assemblies, subassemblies or parts. 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 and DEPOT are listed on the (levels)  AVUM,  AVIM, Maintenance  Allocation B-2