TM 55-2840-241-23 Section II. COMPRESSOR b.   Inspect   the   compressor   front   support vanes   and   first-stage   rotor   blades.   Replace   the engine   if   any   mechanical   damage,   bending,   or distortion   is   detected. If   the   engine   is   frequently   subject   to   sand and   dirt   ingestion,   compressor   erosion   inspec- tion   is   recommended.   (Refer   to   paragraphs   7- 10 and 7-11.) a.   Foreign   objects   or   materials   found   in inlet  during  inspection  of  the  aircraft  when  not in   operation.   If   it   can   be   determined   that   the blackage   was   not   there   during   the   last   opera- tion   of   the   engine,   remove   the   foreign   object or   material   and   leave   the   engine   in   service. Perform  engine  vibration  test  after initial   installation   of   engine   in aircraft,  after  removal  of  combus- tion   case,   when   excessive   engine vibration  is  suspected;  or  when  any maintenance   has   been   performed that  may  effect  engine  to  transmis- sion   alignment.   The   engine   vibra- tion  test  requirement  shall  apply  to all   engines   installed,   reinstalled, new,   overhauled,   same   or   dif- ferent. b.    Power    loss    encountered    following    a restriction   at   the   compressor   inlet   area   while the   engine   is   in   operation.   Blockage   in   flight can usually be verified by inspection after land- ing   (blockage   still   exists).   However,   some blockage  may  be  followed  by  ingestion  before inspection  can  take  place.  Objects  or  materials which   were   large   enough   to   have   stopped   at the   inlet   guide   vanes   before   ingestion   should be  considered  to  have  caused  compressor  inlet b l o c k a g e . 12-3.   Scope. This   section   presents   special   inspections to  be  performed  on  the  engine  when  damage has  been  sustained  due  to  operation  under  ab- normal   conditions   or   operation   in   severe climatic     conditions. 12-4.   Snow   and   Ice   Ingestion   Inspection. This   inspection   must   be   performed   follow- ing  an  inflight  flameout  in  ice  producing weather or anytime snow and ice ingestion is suspected.  Inspect  the  compressor  or  snow, ice,  or  water  damage  as  follows: a.  Obtain  access  to  the  compressor  inlet  but do  not  disassemble  any  engine  parts. 12-5.   Compressor   Inlet   Blockage   Inspec- tion. Replace  the  engine  if  it  has  been  operated with   inlet   air   restricted   due   to   foreign   objects or  materials  which  have  become  lodged  in  the compressor  relet.  Tag  the  replaced  engine  to show  that  the  cause  of    removal  was  inlet  air blockage.    Conditions    which    constitute    block- age  are  as  follows: 12-6.   Foreign   Object   Damage   (FOD)   In- spection. Power  loss  associated  with  an  increase  in engine  vibration  can  often  be  attributed  to foreign   object   damage.   Inspect   for   foreign   ob- ject   damage   as   follows: a.  Obtain  access  to  the  compressor  inlet  but do  not  disassemble  any  engine  parts. b.   Inspect   the   compressor   front   support vanes  and  first-stage  rotor  blades  and  vanes for   FOD. c.  If  the  inspection  in  step  b  is  inconclusive, remove   one   compressor   case   half   and   check for   FOD.   (Refer   to   paragraph   6-2.) d.  If  the  compressor  FOD  is  not  detected, remove   the   combustion   section   (paragraph   3- 21)  and  check  the  turbine  first-stage  vanes  and blades   for   FOD. e.   If   compressor   or   turbine   FOD   is   detected, replace   the   engine. 12-7.   Erosion   Inspection. 12-8.   Vibration   Inspection. NOTE I n   engine.   vibration   is   encountered   deter- mine  the  origin  of  the  vibration  as  follows  and repair  or  replace  the  engine  as  applicable. a .   Install   vibration   monitoring   kit,   tool   No. 171170-0104,  in  accordance  with  TM  55-4920- 243-15. b.  Run  the  engine  and  check  for  vibration  in excess  of  the  limits  specified  in  table  10-1. Note  the  origin  of  the  vibration. c.   If   the   compressor,   turbine,   or   gearbox vibration   limits   are   exceeded,   replace   the   en- gine. Change 16 12-3