TM 55-4920-413-13&P APPENDIX B MAINTENANCE ALLOCATION CHART Section L INTRODUCTION B-1.  MAINTENANCE  ALLOCATION  CHART. a.  This  Maintenance  Allocation  Chart  (MAC)  as- signs  maintenance  functions  in  accordance  with  the Three  Levels  of  Maintenance  concept  for  army  aircraft. These maintenance levels Aviation Unit Maintenance (AVUM),   Aviation   Intermediate   Maintenance (AVIM)  and  Depot  Maintenance  are  depicted  on  the MAC as: AVUM   WHICH   CORRESPONDS   TO   THE   O CODE   IN   THE   REPAIR   PARTS   AND   SPECIAL TOOLS LIST (RPSTL) AVIM   WHICH   CORRESPONDS   TO   THE   F CODE   IN   THE   REPAIR   PARTS   AND   SPECIAL TOOLS LIST (RPSTL) DEPOT  WHICH  CORRESPONDS  TO  THE  D CODE   IN   THE   REPAIR   PARTS   AND   SPECIAL TOOLS LIST (RPSTL) b.  The  maintenance  to  be  performed  below  depot and in the field is described as follows (1)   Aviation   Unit   Maintenance   (AVUM)   - AVUM   activities   will   be   staffed   and   equipped   to perform  high  frequency  “On-Equipment”  mainte- nance tasks required to retain or return equipment to a serviceable  condition.  The  maintenance  capability  of the AVUM will be governed by the MAC and limited by the amount and complexity of support equipment, facilities  required,  and  number  of  spaces  and  critical skills available. The range and quantity of authorized spare modules/components will be consistent with the mobility   requirements   dictated   by   the   air   mobility concept.  (Assignment  of  maintenance  tasks  to  divi- sional  company  size  aviation  units  will  consider  the overall  maintenance  capability  of  the  division,  the requirement   to   conserve   personnel   and   equipment resources and air mobility requirements ). (a)  Company  Size  Aviation  Units  Perform those   tasks   which   consist   primarily   of   preventive maintenance and maintenance repair and replacement functions  associated  with  sustaining  a  high  level  of equipment  operational  readiness.  Perform  maintenance inspections and servicing to include daily, intermedi- ate, periodic and special inspections as authorized by the MAC or higher headquarters. Identify the cause of equipment/system malfunctions   using   applicable technical  manual  troubleshooting  instructions,  Built-In- Test Equipment (BITE ), installed instruments, or easy to  use  Test  Measurement  and  Diagnostic  Equipment (TMDE).  Replace  worn  or  damaged  modules/comp- nents  which  do  not  require  complex  adjustments  or system alignment and which can be removed/installed with  available  skills,  tools  and  equipment.  Perform operational  and  continuity  checks  and  make  minor repairs.  Perform  servicing,  functional  adjustments,  and minor  repair/replacement.  Evacuate  unserviceable modules/components and end items beyond the repair capability of AVUM to the supporting AVIM. (b) Less than Company Size Aviation Units: Aviation elements organic to brigade, group, battalion headquarters  and  detachment  size  units  are  normally small and have less than ten aircraft assigned. Main- tenance tasks performed by the aircraft crew chief or assigned  aircraft  repairman  will  normally  be  limited  to preventive   maintenance,  inspections,  servicing,  spot painting,  stop  drilling,  minor  adjustments,  module/ component  fault  diagnosis  and  replacement  of  selected modules/components.  Repair  functions  wil  normally be accomplished by the supporting AVIM unit. B-2. USE OF THE MAINTENANCE ALLOCATION CHART. a.  The  MAC  assigns  maintenance  functions  to  the lowest level of maintenance based on past experience and the following consideration: (1) Skills available. (2) Time required. (3)  Tools  and  test available. equipment  required  and/or b. Only the lowest level of maintenance authorized to perform a maintenance function is indicated. If the lowest  level  of  maintenance  cannot  perform  all  tasks  of B-1