TM 1-1510-223-10 They   are   of   the   monobromotrifluoromethane   (CF₃Br) type.  The extinguisher is charged to a pressure of 150 to   170   PSI   and   emits   a   forceful   stream.      Use   an extinguisher   with   care   within   the   limited   area   of   the cabin to avoid severe splashing. NOTE Engine fire extinguisher systems are described in Section III. 2-15. SURVIVAL KITS. Tie-down   provisions   for   three   survival   rafts   and kits are provided just aft of the toilet on the right side of the aft cabin area. Section III. ENGINES AND RELATED SYSTEMS 2-16. ENGINES. The aircraft is powered by two PT6A-67 turboprop engines, rated at 1200 SHP (fig.  2-11).  Each engine is equipped    with    a    hydraulically    controlled,    reversible, constant-speed,    four-bladed    full-feathering    propeller. The  engines  are  reverse-flow  free  turbines,  employing four-stage axial compressors and single-stage centrifugal  compressors  in  combination,  driven  by  the gas  generator  turbine.    The  gas  generator  turbine  and the  two  power  turbines  are  in  line  with  each  other  and have    opposite    rotations.        The    power    turbines    are connected   through   planetary   reduction   gearing   to   a flanged   propeller   shaft.      The   oil   tank,   filler   cap   and dipstick are an integral part of the engine. Being  a  reverse  flow  engine,  the  ram  air  supply enters  the  lower  portion  of  the  nacelle  and  is  drawn  in through   the   aft   protective   screens.      The   air   is   then routed into the compressor.  After it is compressed, it is forced into the annular combustion chamber, and mixed with fuel that is sprayed in through 14 nozzles mounted around    the    gas    generator    case.        A    capacitance discharge  ignition  unit  and  two  spark  igniter  plugs  are used to start combustion.  After combustion, the exhaust passes  through  the  compressor  turbine  and  two  stages of  power  turbines,  then  is  routed  through  two  exhaust ports  near  the  front  of  the  engine.    A  pneumatic  fuel control system schedules fuel flow to maintain power set by  the  gas  generator  POWER  lever.    The  accessory drive  at  the  aft  end  of  the  engine  provides  power  to drive the fuel pumps, fuel control, oil pumps, refrigerant compressor   (right   engine),   starter/generator,   and   the tachometer  generator.    The  reduction  gearbox  forward of  the  power  turbine  provides  gearing  for  the  propeller and    drives    the    propeller    tachometer    generator,    the propeller overspeed governor, and the propeller primary governor. 2-17. ENGINE COMPARTMENT COOLING. The   forward   engine   compartment   including   the accessory  section  is  cooled  by  air  entering  around  the exhaust  stack  cutouts,  the  gap  between  the  propeller spinner   and   forward   cowling,   and   exhausting   through louvers in the upper forward aid aft cowling. 2-18. AIR INDUCTION SYSTEMS - GENERAL. Each   engine   and   oil   cooler   receives   ram   air, ducted  from  separate  air  inlets  located  within  the  lower section    of    the    forward    nacelle.        Induction    system components   protect   the   power   plant   from   icing   and reduce the possibility of foreign object damage. 2-19. FOREIGN OBJECT DAMAGE CONTROL. The    engine    has    an    integral    air    inlet    screen designed  to  obstruct  objects  large  enough  to  damage the compressor. 2-20. ENGINE ICE PROTECTION SYSTEMS. 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  bypass door  are  lowered  into  the  airstream  when  operating  in visible    moisture    at    5    °C    or    colder,    by    energizing electrical actuators with the switches, placarded # 1 and #    2    ICE    VANE    CONTROL    -    ON,    located    on    the overhead    control    panel    (fig.        2-13).        The    system incorporates an electrical back-up system which operates  identically  to  the  main  system.    The  back-up ice vane system is controlled by two switches placarded #1   and   #2   ICE   VANE   POWER   SELECT   -   MAIN   - STANDBY,  located  on  the  overhead  control  panel  (fig. 2-13).  If the main system fails, placing the switch in the STBY   position   will   allow   use   of   the   back-up   system. Electrical  protection  is  provided  through  two  5-ampere circuit breakers placarded ICE VANE CONTR MAIN and ICE     VANE     CONTR     AUXILIARY,     located     on     the overhead circuit breaker panel. b. Engine   Ice   Protection   Systems   Operation. The  vane  deflects  the  ram  airflow  slightly  downward  to introduce  a  sudden  turn  in  the  airflow  to  the  engine, causing the moisture particles to continue on undeflected,  because  of  their  greater  momentum,  and be discharged overboard. Once    the    ice    vane    system    is    actuated,    the extended   position   of   the   vane   and   bypass   door   is indicated  by  green  annunciators,  placarded  #  1  VANE EXT and #2 VANE EXT located on the caution/advisory panel.    If  for  any  reason  the  vane(s)  do  not  attain  the selected position within 33 seconds, an amber #1 VANE FAIL  or  #  2  VANE  FAIL  annunciator(s)  illuminates  on the caution/ advisory panel. 2-21