TM 5-6115-590-12 condition due to excessive demands for shaft poser and pneumatic   power.      Automatic   limiting   of   bleedair   is accomplished by a pneumatic thermostat installed In the turbine   exhaust   that   opens   at   a   preset   exhaust   gas temperature and bleeds control air from the load control valve  to  modulate  and  reduce  the  flow  of  compressed air    from    the    engine.    The    bleed-air    control    system consists    of    the    following    components    together    with interconnecting lines and fittings.  load control valve: air pressure  regulator;  and  load  control  thermostat.    The utilization  of  bleed-air  supplied  at  the  bleed-air  outlet from the engine for external compressed air requirements,  heated  air  in  the  conditioned  air  system, water   compartment   heating   air,   and   vacuum   system ejector air Is described in later paragraphs in the section concerning those systems. (e)    Engine  Electrical  System  (fig  1-5).    The engine   electrical   system   is   a   24V   DC   system   which provides automatic actuation in proper sequence, of the various  circuits  which  control  engine  starting,  ignition, fuel flow,  acceleration monitoring engine operation, and engine shutdown.  The engine electrical system consists of the following components together with interconnecting   wiring   and   connectors:   starter   motor, centrifugal  switch,  oil  pressure  sequencing  switch,  low oil pressure switch, ignition unit, igniter plug, fuel shutoff solenoid    valve,    load    control    valve    solenoid,    time totalizing  meter,  circuit  breaker,  oil  temperature  bulb, exhaust   gas   temperature   thermocouple,   tachometer, and   an   engine   air   blockage   alarm   system.      When energized, the starter motor rotates the engine gear train and  compressor  and  turbine  rotating  parts.    Rising  oil pressure actuates the ail pressure sequencing switch to complete   a   circuit   to   open   the   fuel   shutoff   solenoid valve and energize the ignition unit and ignite plug.  At approximately 35 percent of engine governed speed, the starter cutout switch in the centrifugal switch actuates to open  the  circuit  to  the  starter  motor.    At  approximately 95-percent of engine governed speed.  the ready to load switch  in  the  centrifugal  switch  is  actuated  and  opens the circuit to the ignition unit and closes the circuit of the tune  totalizing  meter.    If  the  engine  should  overspeed, the overspeed shutdown switch in the centrifugal switch is  actuated  at  105  to  110  percent  of  engine  governed speed, and opens the circuit to the fuel shutoff solenoid valve to stop the flow of fuel to the combustion chamber to stop the engine.  During engine starting.  the low oil pressure  switch  is  actuated  by  increasing  oil  pressure and completes a holding circuit which is opened to shut off  fuel  flow.    If  the  oil  pressure  drops  below  a  preset minimum pressure during engine operation.  The engine air blockage alarm system consists of two switches. electrically  connected  to  a  warning  light  on  the  control panel and to the engine control circuitry. If the negative pressure    in    the    air    inlet    plenum    increases    by    a determined amount past a set point, one of the switches will   light   a   lamp   on   the   control   panel   to   warn   the operator.  If the negative pre continues to increase by a determined  amount  past  the  set  point,  the  other  switch will shut down the engine (f)    Lubrication  System  (fig  1-6).    The  engine lubrication    system    provides    pressurized    spray    and splash lubrication for the gears.  shafts, and bearings m the   engine.      The   lubrication   system   consists   of   the following components together with interconnecting lines and fittings: an oil pump assembly with integral pressure and scavenge pumps and filter element, oil temperature bulb,  oil  jet  and  scavenge  fittings,  cooling  air  fan,  oil temperature   regulator   (oil   cooler),   oil   tank,   dual   pad drive  assembly  scavenge  pump,  and  low  oil  pressure switch.    The  oil  pump  assembly  pumps  oil  from  the  oil tank   through   a   filter   to   the   oil   jets   on   the   engine. Scavenge   oil   is   pumped   from   the   engine   scavenge areas to the oil temperature regulator (oil cooler), where a  thermostatic  valve  bypasses  the  oil  through  the  oil cooler  tubes,  if  required,  then  returns  the  cooled  oil  to the  oil  tank.    The  scavenge  oil  pump  on  the  dual  pad gear  box  returns  scavenge  oil  from  the  gear  box  sump to  the  oil  tank.    The  cooling  air  fan  directs  a  portion  of the cooling air flow through a duct to the tubes in the oil temperature    regulator    (oil    cooler).        The    remaining cooling air developed by the cooling fan is ducted to the 400 Hz generator.  The low oil pressure switch provides for  shutdown  of  the  engine  in  the  event  oil  pressure should   drop   below   minimum   pressure   during   engine operation. (2)    Fuel  System.    The  fuel  system  filters  fuel  from the external inlet fitting and supplies it at a constant pressure  to  the  engine  fuel  control  system  inlet.    The fuel    system    consists    of    the    following    components together  with  interconnecting  lines  and  fittings:  a  fuel boost pump to assure constant inlet pressure to the fuel control  system,  a  one  gallon  fuel  tank  for  fuel  reserve during   changeover   from   one   external   fuel   source   to another,  a  fuel  float  tank  incorporating  a  float  switch which  initiates  unit  shutdown  to  prevent  damage  to  the fuel  control  in  the  event  the  fuel  supply  is  exhausted while   the   unit   is   running,   a   manual   push   valve   for purging    air    from    the    fuel    float    tank,    a    fuel    filter assembly, and a manual push valve for purging air from the fuel inlet system.  An additional fuel filter/separator assembly    is    provided    as    a    power    plant    accessory component for filtering fuel between the external source and the power plant fuel inlet. 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