TM 1-1510-218-10 2-34 2-24.  FOREIGN OBJECT DAMAGE CONTROL. The   engine   has   an   integral   air   inlet   screen designed  to  obstruct  objects  large  enough  to  damage the compressor. NOTE The   engine   anti-ice   system   (ice   vanes) should   be   on   (extended)   for   all   ground operations to minimize ingestion of ground debris.      It   may   be   necessary   to   turn   off engine anti-ice (retract ice vanes) in warm ambient  conditions  to  preclude  exceeding engine gas temperature limits.  2-25.  ENGINE ICE PROTECTION SYSTEMS. CAUTION After the vanes have been manually extended, they may be mechanically actuated  only.    No  electrical  extension  or retraction shall be attempted as damage to the electric actuator will result.  Linkage in the   nacelle   area   must   be   reset   prior   to operation of the electric system. a.   Inertial   Separator.      An   inertial   separation system  is  built  into  each  engine  air  inlet  to  prevent moisture    particles    from    entering    the    engine    inlet plenum under icing conditions.  A movable vane and a by-pass  door  are  lowered  into  the  air  stream  when operating   in   visible   moisture   at   +5°C   or   colder,   by energizing    electrical    actuators    with    the    switches, placarded  ICE  VANE  RETRACT/EXTEND    C    D    T1   and  ICE  VANE  CONTROL/ON   T2  ,  located  on  the overhead   control   panel.      Refer   to   Figure  2 -15.    A mechanical     backup     system     is     provided,     and     is actuated by pulling the T-handles just below the pilot's subpanel,   placarded   ICE   VANE   #1   ENG   and   ICE VANE #2 ENG  C D1 T2 and  ICE VALVE # 1 ENG and ICE   VALVE   #   1   ENG   T1   .      Decrease   airspeed   to 160 knots    or    less    to    reduce    forces    for    manual extension.  Normal airspeed may then be resumed. (1)   The   vane   deflects   the   ram   air   stream slightly downward to introduce a sudden turn in the air stream to the engine, causing the moisture particles to continue    on    undetected,    because    of    their    greater momentum, and to be discharged overboard. (2)   While    in    the    icing    flight    mode,    the extended  position  of  the  vane  and  by-pass  door  is indicated  by  green  annunciator  lights,   #1  VANE  EXT and #2 VANE EXT. (3)   In the non-ice protection mode, the vane and by-pass door are retracted out of the air stream by placing    the    ice    vane    switches    in    the    RETRACT position.   The  green  annunciator  lights  will  extinguish.   Retraction   should   be   accomplished   at   +15°C   and above   to   assure   adequate   oil   cooling.      The  vanes should  be  either  extended  or  retracted;  there  are  no intermediate positions. (4)   If for any reason the vane does not attain the  selected  position  within  15  seconds,  a  yellow   #1 VANE FAIL  or #2 VANE FAIL light illuminates on the caution/advisory   panel.      In   this   event,   the   manual backup  system  should  be  used.    When  the  vane  is successfully  positioned  with  the  manual  system,  the yellow    annunciator    lights    will    extinguish.        During manual system use, the electric motor switch position must  match  the  manual  handle  position  for  a  correct annunciator readout. b.  Engine Air Inlet Deice C D .  Engine exhaust heat is utilized for heating the engine air inlet lips.  Hot exhaust  is  picked  up  by  a  scoop  inside  each  engine exhaust stack and plumbed downward to connect into each  end  of  the  inlet  lip.    Exhaust  flows  through  the inside  of  the  lip  downward  to  the  bottom  where  it  is plumbed  out  through  the  bottom  of  the  nacelle.    No shut-off  or  temperature  indicator  is  necessary  for  this system. c.   Engine  Air  Inlet  Deice     T  .    A  small  duct, facing into the exhaust flow of the engine's left exhaust stack,  diverts  a  small  portion  of  the  engine  exhaust gases to the engine air inlet anti-ice lip.   The gases are circulated  through  the  engine  air  inlet  anti-ice  lip  and then  exhausted  through  a  duct  to  the  engine's  right exhaust   stack.      The  continuous  flow  of  hot  engine exhaust  gases  heats  the  engine  air  inlet  anti-ice  lip, preventing the formation of ice. d.  Fuel  Heater.    An  oil-to-fuel  heat exchanger, located    on    the    engine    accessory    case,    operates continuously    and    automatically    to    heat    the    fuel sufficiently  to  prevent  ice  from  collecting  in  the  fuel control   unit.      Each   pneumatic   fuel   control   line   is protected against ice. Fuel control heat is automatically turned on for all engine operations. 2-26.  ENGINE FUEL CONTROL SYSTEM. C D  The basic engine fuel system consists of an engine driven fuel pump, a fuel control unit, a fuel flow divider,  a  dual  fuel  manifold  and  14  fuel  nozzles.   The fuel flow  divider acts as a drain valve to clear residual fuel after engine shutdown.