TM 1-1510-218-10 2-76 gear  up-lock  switch.    When  the  system  is  activated, the  BRAKE DEICE ON light should be monitored and the     control     switch     selected     off     after     the     light extinguishes otherwise, on the next gear extension the system  will  restart  without  pilot  action.     The  control switch  should  also  be  selected  off,  if  deice  operation fails  to  self-terminate  after  about  10  minutes.    If the automatic timer has terminated brake deicer operation after the last retraction of the landing gear, the landing gear   must   be   extended   in   order   to   obtain   further operation of the system. (1)   BL   AIR   FAIL    lights    may    momentarily illuminate during simultaneous operation of the surface deice  and  brake  deice  systems  at  low  N₁  speeds.    If lights immediately extinguish, they may be disregarded. (2)   During certain ambient conditions, use of the  brake  deice  system  may  reduce  available  engine power,  and  during  flight  will  result  in  a  TGT  rise  of approximately 20°C.   Appropriate performance charts should be consulted before brake deice system use.  If specified power cannot be obtained without exceeding limits,  the  brake  deice  system  must  be  selected  off until after take-off is completed.   TGT limitations must also be observed when setting climb and cruise power.   The  brake  deice  system  is  not  to  be  operated  above 15°C  ambient  temperature.    The  system  is  not  to  be operated for longer than 10 minutes (one deicer cycle) with  the  landing  gear  retracted.   If operation does not automatically terminate after approximately 10 minutes following gear retraction, the system must be manually selected  off.    During  periods  of  simultaneous  brake deice and surface deice operation, maintain 85% N₁ or higher. If inadequate pneumatic pressure is developed   for   proper   surface   deicer   boot  inflation, select  the  break  deice  system  off.    Both  sources  of pneumatic bleed air must be in operation during brake deice system use.   Select the brake deice system off during  single-engine  operation.     Circuit  protection  is provided   by   a   5-ampere   circuit   breaker,   placarded BRAKE DEICE, on the overhead circuit breaker panel. 2-66.  FUEL SYSTEM ANTI-ICING. a.   Description.    An  oil-to-fuel  heat  exchanger, located   on   each   engine   accessory   case,   operated continuously    and    automatically    to    heat    the    fuel sufficiently to prevent freezing of any water in the fuel.   No controls are involved.   Two  external  fuel  vents  are provided  on  each  wing.    One  is  recessed  to  prevent ice  formation;  the  other  is  electrically  heated  and  is controlled   by   two   toggle   switches   on   the   overhead control  panel,  placarded   FUEL  VENT  LEFT  /  ON  / RIGHT,   Figure   2 -15.      They   are   protected   by   two 5-ampere    circuit    breakers,    placarded    FUEL   VENT HEAT   /   RIGHT   or   LEFT,  located  on  the  overhead circuit   breaker   panel.      Each   fuel   governing   line   is protected against ice  by  an  electrically  heated  jacket.   A 7.5-ampere circuit breaker located on the overhead circuit breaker panel, placarded FUEL CONTR HEAT / LEFT or   RIGHT  protects  the  heater.    The  bleed  air pneumatic    line    is    protected    against    ice    by    wrap insulation. CAUTION To prevent overheat damage to electrically heated  anti-ice   jackets,   FUEL   VENT   heat switches  should  not  be  turned  ON  unless cooling air will soon pass over the jackets.  b.  Normal   Operation.      For  normal  operation, switches   for   the   FUEL   VENTS   anti-ice   circuits  are turned   ON   as   required   during   the   Before   Takeoff procedures.  Chapter 8 contains normal operations. 2-67.  WINDSHIELD   ELECTROTHERMAL   ANTI-ICE SYSTEMS. a.   Description. Both pilot and copilot windshields     are     provided     with     an     electrothermal anti-ice    system.        Each    windshield    is    part    of    an independent   electrothermal   anti-ice   system.      Each system  is  comprised  of  the  windshield  assembly  with heating   wires   sandwiched   between   glass   panels,   a temperature sensor attached to the glass, an electrothermal controller, two relays, a control switch, and   two   circuit   breakers.      Two  switches,  placarded FAST WSHLD ANTI-ICE PILOT / COPILOT NORMAL / OFF / HI   C  D  T1  and  WSHLD  ANTI-ICE PILOT / COPILOT NORMAL / OFF / HIGH    T2   , are located  on  the  overhead  control  panel,  Figure  2-15.   Each   switch   controls   one   electrothermal   windshield system.  The  NORMAL position energizes only the low power  mode.    The  high  position  energizes  the  high power  mode.   When energized, the system cycles on at 94 ± 6°F and off at 105 ± 5°F.   The circuits of each system  are  protected  by  a  5-ampere  circuit  breaker, which  are  not  accessible  to  the  flight  crew.    The  50- ampere   circuit   breakers   are   located   in   the   power distribution  panel  under  the  floor  ahead  of  the  main spar.    The  5-ampere  circuit  breakers  are  located  on panels forward of the instrument panel. b.  Normal Operation.    Two  levels  of  heat  are provided through the three position switches placarded NORMAL   in    the    aft    position,    OFF   in    the    center position, and HIGH after lifting the switch over a detent and moving it to the forward position.   In the NORMAL position, heat is provided for the major portion of each windshield.   In the HIGH position, heat is provided at a higher    watt    density    to    a    smaller    portion    of    the windshield. The lever lock feature prevents