TM 5-6115-593-12 TO 35C2-3-463-1 contains  four  motor-operated  louvers  which open  during  engine  operation  and  close  at engine shutdown.  Louver control relays K60 through    K63,    louver    motor    pilot    travel- limiting    switches    S60    through    S63,    and louver    motors    B10    through    B13    (each capable   of   two-way   operation)   control   the four  louver  assemblies.    When  the  engine starts,  each  louver  control  relay  energizes and 24V DC is applied, by way of the louver motor  pilot  switches,  to  the  louver  motors and  the  louvers  open.    Upon  reaching  their full-open position the louvers set the travel- limit    switches    to    their    opposite    position, deactivating    the    louver    motors.    Louver operation  at  the  shut  down  is  exactly  the same except that the motors operate in the reverse   direction   and   24V   DC   is   applied through the normally closed contacts of the deenergized louver control relays. f. Engine  Stopping.      When   it   is   required   to stop   the   engine   after   a   period   of   normal operation, the operator momentarily sets the spring  loaded  MASTER  SWITCH  S1  to  the STOP  position,  thereby  deenergizing  relay K5.      With   K5   now   deenergized,   run   pilot relay  K54  drops  out,  its  contacts  1  and  2 open  and  +24V  DC  magnetizing  voltage  is removed  from  fuel  solenoid  L1.    After  the small  amount  of  fuel  remaining  in  the  lines past the point of fuel cutoff is consumed, the engine comes to a halt. g. Emergency Stopping.  When an emergency exists,   such   as   might   pose   a   threat   to personnel or equipment, as quick a shutdown as possible is required.  To ensure this,   the   air   boxes   in   series   with   the   air intake   manifolds   are   closed   and   the   fuel supply    is    shut    off,    thus    interrupting    the engine's   air   and   fuel   supply   and   quickly bringing   the   engine   to   a   stop.   Operating EMERGENCY  SHUTDOWN  switch  S22  to ON,   energizes   emergency   stop   relay   K21 and,    when    solenoids    L2    and    L22    are actuated (through normally open contacts of K21)   the   air   boxes   close   interrupting   the stream   of   air   to   the   engine.      When   the engine shuts down, oil pressure switch OP3 opens and disconnects 24V DC from L2 and L22.  A second set of K21 contacts removes +24V DC from solenoid L1 and cuts off the engine's fuel supply. h. Engine  Protection.    Operation  will  continue as  long  as  no  fault  condition  occurs  which might  cause  damage  to  the  engine.    Once such a condition does occur, engine operation is automatically brought to a halt. The   following   subparagraphs   describe   the fault which will stop the engine and by what circuitry this stoppage is implemented. (1) Engine  Overspeed.    If  engine  speed increases   to   a   point   where   damage may occur, overspeed switch SS3 (set to    operate    at    approximately    2250 rpm) closes activating overspeed relay  K31.    As  a  result,  the  normally open contacts of K31 (in parallel with EMERGENCY SHUTDOWN SWITCH S22)   close   and   energize   relay   K21. The  action  from  this  point  on  is  the same as for emergency stopping. (2) Low  Oil  Pressure..    If  lubricating  oil pressure   falls   below   21   ±2   psi   (1.5 kg/cm  )  the  contacts  of  oil  pressure switch  OP1  open  and  remove  power from    fuel    solenoid    L1.        Because engine    oil    does    not    build    to    its required    pressure    immediately,    the engine   may   shut   down   "thinking"   a fault   has   occurred.      To   avoid   this premature operation, time delay assembly  TD3  inhibits  the  operation of   relay   K6   for   5   seconds--allowing pressure to build. (3) Oil   Temperature.      If   lubricating   oil temperature   rises   above   255    ±3°F (124  +1°   C),  damage  to  the  engine may    occur.        To    prevent    this,    oil temperature switch OT1 1-24