TM 1-1500-204-23-1 f. Significance of Metal Particles.  Generally, when metal  particles  are  found  and  kind  of  metal  present  is determined,  serviceability  of  engine  will  depend  upon quantity and form of metal.  Granular metal particles, in any amount greater than a trace, require a very careful inspection  of  engine,  as  presence  of  these  particles  is usually an indication of an impending failure.  Each kind of     metal,     however,     must     be     judged     individually. Paragraphs  (1)  through  (5)  are  intended  as  a  guide  in judging  serviceability  of  engine  after  kind  of  metal  has been determined. (1) Steel  particles.    When  steel  particles  are found in splinter or In granular form, the engine must be removed Thin steel flakes, when found In quantities not greater than 20 flakes, may not require engine removal. A  small  quantity  of  steel  flakes  will  not  cause  engine bearing failure.  When thin steel flakes accompanied by aluminum  flakes  are  found,  these  flakes  are  probably the result of a warped piston ring land or hole burned in a   piston.      Replacement   of   a   defective   piston   and cylinder  assembly    will    correct    the    difficulty.    When not accompanied by aluminum flakes, it Is possible that steel   flakes   are   from   foreign   matter   introduced   into engine through oil tank. (a) Test  engine  in  accordance  with  the applicable    maintenance    manual    If    more    than    five additional   flakes   are   found   on   oil   screen   and   sump inspection  after  runup,  remove  engine.    If  five  or  less flakes found, the engine may be released for service in accordance with the applicable maintenance manual. (b) When  not  more  than  20  thin  steel flakes   are   found   and   they   are   accompanied   by   thin aluminum flakes, proceed as follows 1 Carefully   inspect   cylinders   by visual examination of cylinder bore and by compression check In an effort to locate faulty piston.  A bright streak along  cylinder  barrel  or  any  evidence  of  scuffing  would be an indication of a warped piston ring land.  Warped lands  are  predominant  In  winter  operations  and  occur most frequently on lower cylinders. 2 When  not  more  than  two  faulty cylinders  are  found,  replace  faulty  piston  and  cylinder assemblies   before   continuing   with   procedure.      When more  than  two  faulty  cylinders  are  found  by  inspection, remove engine. 3 After faulty cylinders have been changed   or   when   no   faulty   cylinders   are   found,   test engine  In  accordance  with  the  applicable  maintenance manual. 4 If  more  than  2  additional  steel flakes  or  15  aluminum  flakes  are  found  during  screen and sump inspection after engine runup, remove engine. If  less  than  these  quantities  are  found,  engine  may  be released  for  service  in  accordance  with  the  applicable maintenance manual. NOTE Ring fuzz may be on oil sump plug of any  normal  engine.    These  very  fine hairlike   particles   are   the   result   of normal  seating  of  piston  rings  and cylinders  and  are  not  cause  for  any concern   regarding   serviceability   of engine. (2) Tin particles.  Tin in any quantity may be disregarded.    Since  tin  is  used  only  in  plating  engine parts   and   in   thickness   not   greater   than   0.0005   inch, granular tin will not be found. (3) Aluminum      particles.    When      aluminum particles are found, perform the following procedures: (a) When  granular  aluminum  particles are found, proceed as follows: NOTE The  presence  of  aluminum  particles in granular form may be an indication of piston failure 1 Inspect cylinders by visual examination of cylinder bores and a compression check in an effort to locate a faulty piston. 2 When  not  more  than  two  faulty pistons are found, faulty pistons and cylinder assemblies will    be    changed    before    continuing    with    procedure. When    more    than    two    faulty    pistons    are    found    by inspection,   remove   engine.      After   faulty   pistons   and cylinder  assemblies  have  been  changed,  or  when  no faulty pistons are found, continue with procedure. 3 Drain  oil  system,  flush  oil  tank, and clean oil screens. 4 Test  engine  in  accordance  with the applicable maintenance manual. 7-26