cates   that   the   igniters   are   energized.   The   autoigni- tion  system  is  triggered  from  a  ready  condition  to  an operating  condition  when  engine  torque  drops  below approximately  20%.  Therefore,  when  an  autoignition system  is  armed,  the  igniters  will  be  energized  con- tinuously  during  the  time  when  an  engine  is  operat- ing  at  a  level  below  approximately  20%  torque.  The autoignition  lights  are  protected  by  5-ampere  IGNI- TOR CONTR No. 1 or No. 2 circuit breakers, located on  the  overhead  circuit  breaker  panel  (fig.  2-26). b.   Engine   Torquemeters.   Two   torquemeters on   the   instrument   panel   indicate   torque   applied   to the   propeller   shafts   of   the   respective   engines   (fig. 2-29).  Each  gage  shows  torque  in  percent  of  maxi- mum  using  2  percent  graduations  and  is  actuated  by an  electrical  signal  from  a  pressure  sensing  system located   in   the   respective   propeller   reduction   gear case.  Torquemeters  are  protected  by  individual  0.5- ampere circuit  breakers  placarded  TORQUE METER  No.  1  or  No.  2  on  the  overhead  circuit breaker  panel  (fig.  2-26). 2-31. ENGINE STARTER-GENERATORS. One  starter-generator  is  mounted  on  each  engine accessory   drive   section.   Each   is   able   to   function either  as  a  starter  or  as  a  generator.  In  the  starter function,  28  volts  DC  is  required  to  power  rotation. In  the  generator  function,  each  unit  is  capable  of 400  amperes  DC  output.  When  the  starting  function is  selected,  the  starter  control  circuit  receives  power through  the  respective  5-ampere  START  CONTR circuit  breaker  on  the  overhead  circuit  breaker  panel from  either  the  aircraft  battery  or  an  external  power source.  When  the  generating  function  is  selected,  the starter-generator  provides  electrical  power.  For  addi- tional   description   of   the   starter-generator   system, refer  to  Section  IX. c.  Turbine  Tachometers.  Two   tachometers   on the   instrument   panel   register   compressor   turbine RPM  (N₁)   for   the   respective   engine   (fig.   2-29). These  indicators  register  turbine  RPM  as  a  percent- age   of   maximum   gas   generator   RPM.   Each   instru- ment  is  slaved  to  a  tachometer  generator  attached  to the  respective  engine. 2-32.  ENGINE  INSTRUMENTS. The  engine  instruments  are  vertically  mounted near  the  center  of  the  instrument  panel  (fig.  2-29). d.  Oil  Pressure/Oil  Temperature  Indicators. Two  gages  on  the  instrument  panel  register  oil  pres- sure  in  PSI  and  oil  temperature  in  °C  (fig.  2-29).  Oil pressure  is  taken  from  the  delivery  side  of  the  main oil  pressure  pump.  Oil  temperature  is  transmitted  by a  thermal  sensor  unit  which  senses  the  temperature of the oil as it leaves the delivery side of the oil pres- sure  pump.  Each  gage  is  connected  to  pressure  trans- mitters  installed  on  the  respective  engine.  Both instruments  are  protected  by  5-ampere  circuit  break- ers,  placarded  OIL  PRESS  and  OIL  TEMP  No.  1  or No.   2,   on   the   overhead   circuit   breaker   panel   (fig. 2-26). a. Turbine  Gas  Temperature  Indicators.  Two TGT  gages  on  the  instrument  panel  are  calibrated  in degrees Celsius (fig. 2-29). Each gage is connected to thermocouple  probes  located  in  the  hot  gases between  the  turbine  wheels.  The  gages  register  the temperature  present  between  the  compressor  turbine and  power  turbine  for  the  corresponding  engine. e.   Fuel   Flow   Indicators.  Two   gages   on   the instrument  panel  (fig.  2-29)  register  the  rate  of  flow for  consumed  fuel  as  measured  by  sensing  units  cou- pled   into   the   fuel   supply   lines   of   the   respective engines.   The   fuel   flow   indicators   are   calibrated   in increments   of   hundreds   of   pounds   per   hour.   Both circuits  are  protected  by  0.5-ampere  circuit  breakers placarded  FUEL  FLOW  No.  1  or  No.  2,  on  the  over- head  circuit  breaker  panel  (fig.  2-26). Section IV. FUEL SYSTEM 2-33.  FUEL  SUPPLY  SYSTEM. The engine fuel supply system (fig. 2-13) consists of   two   identical   systems   sharing   a   common   fuel management   panel   (fig.   2-14)   and   fuel   crossfeed plumbing   (fig.   2-15).   Each   fuel   system   consists   of five  interconnected  wing  tanks,  a  nacelle  tank,  and an  auxiliary  inboard  fuel  tank.  A  fuel  transfer  pump is   located   within   each   auxiliary   tank.   Additionally, the  system  has  an  engine-driven  boost  pump,  a standby  fuel  pump  located  within  each  nacelle  tank, a  fuel  heater  (engine  oil-to-fuel  heat  exchanger  unit), a  tank  vent  system,  a  tank  vent  heating  system  and interconnecting  wiring  and  plumbing.  Refer  to  Sec- tion  IX  for  fuel  grades  and  specifications.  Fuel  tank capacity is shown in table 2-2. Gravity feed fuel flow is  shown  in  figure  2-16. TM  55-1510-221-10 2-27