TM  55-4920-401-13&P APPENDIX B MAINTENANCE ALLOCATION CHART Section I. 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 air- craft.  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 capa- bility of the AVUM will be governed by the MAC and limited by the amount and complexity of sup- port 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 divisional company size avi- ation units will consider the overall maintenance capability of the division, the requirement to con- serve personnel and equipment resources and air mobility   requirements). (a) Company Size Aviation Units.  Per- form  those  tasks  which  consist  primarily  of  pre- ventive maintenance and maintenance repair and replacement  functions  associated  with  sustaining  a high  level  of  equipment  operational  readiness.  Per- form maintenance inspections and sevicing to in- elude daily, intermediate, periodic and special in- spections  as  authorized  by  the  MAC  or  higher headquarters.  Identify  the  cause  of  equipment/sys- tem malfunctions using applicable technical man- ual   troubleshooting   instructions,   Built-In   Test Equipment (BITE), installed instruments, or easy to  use  Test  Measurement  and  Diagnostic  Equip- ment (TMDE). Replace worn or damaged modules/ components which do not require complex adjust- ments or system alignment and which can be re- moved/installed  with  available  skills,  tools  and equipment.  Perform  operational  and  continuity checks  and  make  minor  repairs.  Perform  servicing, functional adjustments, and minor repair/replace- ment.  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.  Maintenance  tasks  performed  by  the  air- craft  crew  chief  or  assigned  aircraft  repairman  will normally  be  limited  to  preventive  maintenance,  in- spections,  servicing,  spot  painting,  stop  drilling, minor adjustments, module/component fault diag- nosis  and  replacement  of  selected  modules/com- ponents. Repair functions will normally be accom- plished by the supporting AVIM unit. (2)  Aviation  Intermediate  Maintenance (AVIM). AVIM provides mobile, responsive “One Stop”  maintenance  support.  (Maintenance  func- tions  which  are  not  conducive  to  sustaining  air  mo- bility will be assigned to depot maintenance). Per- forms all maintenance functions authorized to be done at AVUM. Repair of equipment for return to user will emphasize support or operational readi- ness  requirements.  Authorized  maintenance  in- cludes  replacement  and  repair  of  modules/com- ponents and end items which can be accomplished efficiently  with  available  skills,  tools,  and  equip- ment. Establishes the Direct Exchange (DX) pro- gram for AVUM units by repairing selected items for  return  to  stock  when  such  repairs  cannot  be  ac- complished  at  the  AVUM  level.  Inspects,  trou- bleshoots,  tests,  diagnoses,  repairs,  adjusts,  cali- brates,  and  aligns  system  modules/components. Module/component  disassembly  and  repair  will  sup- port the DX progrmam and will normally be limited to tasks requiring cleaning and the replacement of seals, fittings and items of common hardware. Un- serviceable  reparable  modules/components  and  end items which are beyond the capability of AVIM to B-1