TM 5-6115-590-12 connection provisions on the enclosure provide mobility of  the  unit  by  truck,  railroad  car,  helicopter,  airplane, mobilizing transporter wheels, and by skidding. b.    Gas turbine engine power plant (fig.  1-3).  The gas  turbine  engine  power  plant  is  installed  in  the  lower left   front   corner   of   the   power   unit   and   consists   of   a pneumatic  and  shaft  power  gas  turbine  engine,  60  Hz and   400   Hz   generators,   a   fuel   system,   a   lubrication system, various air ducts, plumbing installation, electrical   wiring   installation,   and   a   skid   base.   Two electrical   rack   assemblies   are   installed   on   the   power plant   skid   base   and   contain   various   regulating   and control components for the power unit electrical system. The   gas   turbine   engine   power   plant   provides   shaft power   to   drive   the   60   Hz   and   400   Hz   generators. Compressed  air  from  the  engine  compressor  section  is used   for   external   pneumatic   power   requirements,   for heated     air     in     the     conditioned     air     system,     water compartment  heating  air,  vacuum  system  eductor  air, engine air cleaner ejector air and deicing the engine air inlet filter.  The engine exhaust heat is utilized through a heat exchanger to heat water for the water system. (1)    Pneumatic     and     Shaft     Power     Gas     Turbine Engine  (fig.    1-3).    The  gas  turbine  engine  is  a  self contained power source and requires only a fuel supply and   electrical   starting   power   to   maintain   a   constant output power and rpm (revolutions per minute).  Engine power is developed through compression of ambient air by a two-stage centrifugal compressor; the compressed air,  mixed  with  fuel  and  ignited,  drives  a  radial  inward- flow   turbine   wheel.      The   rotating   shaft   power   of   the turbine  wheel  drives  the  compressor,  the  accessories, and    the    output    drive    shafts.        A    portion    of    the compressed    air    developed    by    the    compressor    is available for external pneumatic power applications.  An internal   system   of   pneumatic   and   electro-mechanical controls  provide  automatic  and  coordinated  control  of engine  starts,  acceleration,  and  operation.    A  minimum of additional external controls are required to initiate the engine  starting  cycle,  monitor  engine  operation,  and  to stop engine operation.  The gas turbine engine consists of  a  compressor  and  turbine  section,  accessory  drive section,   fuel   control   system,   bleedair   control   system, engine electrical system, and engine lubrication system. (a)  Compressor and Turbine  Section. The compressor and turbine section is the power nucleus of the engine. The two stage centrifugal compressor develops compressed   air   for   fuel   combustion   and   for   external pneumatic power.  The single stage turbine incorporates a single combustion chamber which mixes compressed air with the fuel spray from the fuel atomizer, ignites the fuel-air mixture and directs. the  products  of  combustion  to  the  turbine  wheel.    The turbine   wheel   converts   the   power   developed   in   the combustion  chamber  to  shaft  power  which  drives  the compressor impellers and the accessory drive section. (b)    Accessory  Drive  Section.    The  accessory  drive section  is  a  reduction  gear  system  which  reduces  the high rotational speeds developed by the turbine wheel to a  usable  rpm  to  drive  the  engine  accessory  gear  box and  a  dual  pad  gear  box  for  the  60  Hz  and  400  Hz generators.    In  addition  to  mounting  pads  for  the  two generators,     the     accessory     drive     section     provides mounting    pads    and    drive    gear    connection    for    the following  accessories  oil  pump  assembly;  fuel  control unit, centrifugal switch assembly; cooling air fan; starter motor; and tachometer-generator. (c)    Fuel System (fig.  1-4).  The engine fuel system consists  of  components  which  function  automatically  to regulate   fuel   flow   to   the   combustion   chamber   and maintain    near    constant    governed    speed    and    safe operating    temperatures    under    varying    conditions    of starting,   acceleration,   and   load   application.      Control components  function  by  sensing  engine  speed,  turbine exhaust  gas  temperature  and  compressor  air  pressure, and   react   by   adjusting   fuel   flow   to   maintain   these reference indications within established limits.  The fuel system  consists  of  the  following  components  together with interconnecting lines and fittings: a one gallon fuel tank    for    fuel    reserve    during    changeover    from    one external    fuel    supply    to    another;    a    fuel    float    tank incorporating    a    float    switch    which    will    initiate    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 from the fuel float  tank;  an  external  fuel  filter  assembly;  a  fuel  boost pump  to  assure  a  constant  inlet  pressure  to  the  fuel control  unit;  a  fuel  filter  assembly  to  filter  fuel  between the fuel boost pump and fuel control unit; a manual push valve  for  purging  air  from  the  fuel  inlet  system;  a  fuel control   unit   to   regular   fuel   flow   to   the   combustion chamber in response to engine rpm and load requirements;  a  fuel  shutoff  solenoid  valve  to  provide electrically   actuated   on   and   off   control   of   fuel   flow between fuel control unit and fuel atomizer assembly; a fuel   atomizer   assembly   to   provide   a   controlled   fuel spray pattern for proper fuel combustion; an acceleration  and  overtemperature  control  thermostat  to prevent    excessive    exhaust    gas    temperature    during engine acceleration. (d)  Bleed-Air  Control  System  fig  1-4).      The   bleed-air control    system    automatically    limits    the    amount    of compressed air available for external applications, thus maintaining  a  safe  engine  operating  temperature  and preventing an overload Change 6   1-5