TM  55-1510-221-10 levers   also   control   propeller   reverse   pitch.   Distinct movement  (pulling  up  and  then  aft  on  the  power lever)   by   the   pilot   is   required   for   reverse   thrust. Placarding   beside   the   lever   travel   slots   reads POWER.   Upper   lever   travel   range   is   designated INCR   (increase),   supplemented   by   an   arrow   point- ing   forward.   Lower   travel   range   is   marked   IDLE, LIFT   and   REVERSE.   A   placard   below   the   lever slots   reads:   CAUTION   REVERSE   ONLY   WITH ENGINES   RUNNING. 2-23.  CONDITION  LEVERS. Two  condition  levers  are  located  on  the  control pedestal   (fig.   2-7).   Each   lever   starts   and   stops   the fuel  supply,  and  controls  the  idle  speed  for  its engine.   The   levers   have   three   placarded   positions: FUEL   CUTOFF,   LO   IDLE,   and   HIGH   IDLE.   In the   FUEL   CUTOFF   position,   the   condition   lever controls  the  cutoff  function  of  its  engine-mounted fuel   control   unit.   From   LO   IDLE   to   HIGH   IDLE, they  control  the  governors  of  the  fuel  control  units to   establish   minimum   fuel   flow   levels.   LO   IDLE position  sets  the  fuel  flow  rate  to  attain  52  to  55% (at  sea  level)  minimum  N₁ and   HIGH   IDLE   posi- tion   sets   the   rate   to   attain   70%   minimum   N₁.  The power  lever  for  the  corresponding  engine  can  select N₁ from  the  respective  idle  setting  to  maximum power.   An   increase   in   low   idle   N₁ will   be   experi- enced  at  high  field  elevation. 2-24. FRICTION LOCK KNOBS. Four  friction  lock  knobs  (fig.  2-7)  are  located  on the   control   pedestal   to   adjust   friction   drag.   One knob   is   below   the   propeller   levers,   one   below   the condition   levers,   and   two   under   the   power   levers. When  a  knob  is  rotated  clockwise,  friction  restraint is   increased   opposing   movement   of   the   affected lever  as  set  by  the  pilot.  Counterclockwise  rotation of  a  knob  will  decrease  friction  drag  thus  permitting free  and  easy  lever  movement.  Two  FRICTION LOCK  placards  are  located  on  the  pedestal  adjacent to  the  knobs. 2-25. ENGINE FIRE DETECTION SYSTEM. a.  Description.  A  flame  surveillance  system  is installed  on  each  engine  to  detect  external  engine fire  and  provide  alarm  to  the  pilot.  Both  nacelles  are monitored,   each   having   a   control   amplifier   and three  detectors.  Electrical  wiring  connects  all  sensors and  control  amplifiers  to  DC  power  and  to  the  cock- pit  visual  alarm  units.  In  each  nacelle,  one  detector monitors  the  forward  nacelle,  a  second  monitors  the upper  accessory  area,  and  a  third  the  lower  accessory area.   Fire   emits   an   infrared   radiation   that   will   be 2-24 sensed   by   the   detector   which   monitors   the   area   of origin.  Radiation  exposure  activates  the  relay  circuit of  a  control  amplifier  which  causes  signal  power  to be  sent  to  cockpit  warning  systems.  An  activated surveillance   system   will   return   to   the   standby   state after  the  fire  is  out.  The  system  includes  a  functional test  switch  and  has  circuit  protection  through  the FIRE   DETR   circuit   breaker.   Warning   of   internal nacelle  fire  is  provided  as  follows:  the  red  MASTER WARNING   lights   on   the   glareshield   illuminate accompanied   by   the   illumination   of   a   red   warning light   in   the   appropriate   fire   control   T-handle   plac- arded  No.  1  FIRE  PULL  or  No.  2  FIRE  PULL  (fig. 2-29).  Fire  detector  circuits  are  protected  by  a  single 5-ampere   circuit   breaker,   placarded   FIRE   DETR, located   on   the   overhead   circuit   breaker   panel   (fig. 2-26). b.   Fire   Detection   System   Test   Switch.  O n e rotary  switch  placarded  FIRE  PROTECTION  TEST on   the   copilot’s   subpanel   is   provided   to   test   the engine   fire   detection   system.   Before   checkout,   bat- tery  power  must  be  on  and  the  FIRE  DETR  circuit breaker  must  be  in.  Switch  position  DETR  1,  checks the   area   forward   of   the   air   intake   of   each   nacelle, including   circuits   to   the   cockpit   alarm   and   indica- tion   devices.   Switch   position   DETR   2,   checks   the circuits  for  the  upper  accessory  compartment  of each   nacelle.   Switch   position   DETR   3,   checks   the circuits  for  the  lower  accessory  compartment  of  each nacelle.  Each  numbered  switch  position  will  initiate the   cockpit   indications   previously   described. c.  Erroneous  Fire  Detection  System  Indica- tions.  During  ground  test  of  the  engine  fire  detection system,  an  erroneous  indication  of  system  fault  may be   encountered   if   an   engine   cowling   is   not   closed properly,  or  if  the  aircraft  is  headed  toward  a  strong external   light   source.   In   this   circumstance,   change the  aircraft  heading  to  enable  a  valid  system  check. 2-26. ENGINE FIRE EXTINGUISHER SYSTEM. a.  Description.  The   fire   extinguisher   system utilizes   an   explosive   squib,   connected   to   a   valve which,   when   opened,   allows   the   distribution   of   the pressurized   extinguishing   agent   through   a   plumbing network  of  spray  nozzles  strategically  located  in  the fire  zones  of  the  engines. b.  Fire  Pull  Handles .  The   tire   control T-handles,   which   are   used   to   arm   the   extinguisher system  are  centrally  located  on  the  pilot’s  instru- ment   panel   (fig.   2-29),   immediately   below   the glareshield.   These   controls   receive   power   from   the hot  battery  bus.  The  fire  detection  system  will  indi- cate  an  engine  fire  by  illuminating  the  master  fault warning  light  on  the  pilot’s  and  copilot’s  glareshield and  the  respective  No.  1  FIRE  PULL  or  No.  2  FIRE