TM   55-4920-414-13&P APPENDIX   B MAINTENANCE  ALLOCATION  CHART Section   1.   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 (RBT) AVIM   WHICH   CORRESPONDS   TO   THE   F CODE   IN   THE   REPAIR   PARTS   AND   SPECIAL TOOLS LIST (RBT) DEPOT  WHICH  CORRESPONDS  TO  THE  D CODE   IN   THE   REPAIR   PARTS   AND   SPECIAL TOOLS  LIST  (RBT) b. The maintenance to be done below depot and in the field is described as follows: (1)   Aviation   Unit   Maintenance   (AVUM)   - AVUM activities will be staffed and equipped to do high frequency  “On-Equipment” maintenance  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 mo- bility requirements dictated by the air mobility con- cept. (Assignment of maintenance tasks to divisional 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  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/compo- 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 will normally be accomplished by the supporting AVIM unit. (2) Aviation Intermediate Maintenance (AVIM) - AVIM provides mobile, responsive “One Stop” main- tenance  support.  (Maintenance  functions  which  are  not conducive to sustaining air mobility will be assigned to depot  maintenance).  Performs  all  maintenance  func- tions  authorized  to  be  done  at  AVUM.  Repair  of equipment  for  return  to  user  will  emphasize  support  or operational readiness requirements. Authorized main- tenance includes replacement and repair of modules/ components  and  end  items  which  can  be  accomplished efficiently with available skills, tools, and equipment. Establishes  the  Direct  Exchange  (DX)  program  for AVUM units by repairing selected items for return to stock when such repairs cannot be accomplished at the AVUM  level.  Inspects,  troubleshoots,  tests,  diagnoses, repairs,  adjusts,  calibrates,  and  aligns  system  modules/ components. Module/component disassembly and re- pair will support the DX program and will normally B-1