TM 55-1510-219-10 CHAPTER 3 AVIONICS Section I.  GENERAL 3-1.  INTRODUCTION. Except  for  mission  avionics,  this  chapter  covers  all avionics  equipment  installed  in  the  RC-12D  aircraft.    It provides  a  brief  description  of  equipment  covered,  the technical    characteristics    and    locations.        It    covers systems and controls and provides the proper techniques    and    procedures    to    be    employed    when operating the equipment.  For more detailed operational information consult the vendor manuals that accompany the aircraft loose tools. 3-2.  AVIONICS EQUIPMENT CONFIGURATION. The aircraft avionics covered is comprised of three groups  of  electronic  equipment.    The  Communication group  consists  of  the  Interphone,  UHF  command,  VHF command  and  HF  command  systems.    The  Navigation group provides the pilot and copilot with the instrumentation  required  to  establish  and  maintain  an accurate   flight   course   and   position,   and   to   make   an approach on instruments under Instrument Meteorological Conditions (IMC).  The Navigation group includes   equipment   for   determining   altitude,   attitude, position,     destination,     range     and     bearing,     heading reference, groundspeed, and drift angle. The Transponder and Radar group includes an identification, position  and  emergency  tracking  system,  and  a  radar system  to  locate  potentially  dangerous  weather  areas and a radar system to differentiate between friendly and unfriendly search radar. NOTE All  avionics  equipment  require  a 3-minute    warmup    period.        The weather   radar   has   an   automatic time delay of 3 to 4 minutes. 3-3.  POWER SOURCE. a.  DC Power.  DC power for the avionics equipment is provided by four sources: the aircraft battery, left and right  generators,  and  external  power.    Power  is  routed through   a   50-ampere   circuit   breaker   to   the   avionics power    relay    which    is    controlled    by    the    AVIONICS MASTER POWER SWITCH (fig.  2-18) on the overhead control panel.  Individual system circuit breakers and the associated   avionics   busses   are   shown   in   fig.      2-22. With  the  switch  in  the  ON  position,  the  avionics  power relay is de-energized and power is applied through both the   AVIONICS   MASTER   POWER   #1   and   #2   circuit breakers  to  the  individual  avionics  circuit  breakers  on the overhead circuit breaker panel (fig. 2-26).  In the off (aft)   position,   the   relay   is   energized   and   power   is removed   from   avionics   equipment.      When   external power is applied to the aircraft, the avionics power relay is    normally    energized,    removing    power    from    the avionics  equipment.    To  apply  external  power  to  the avionics   equipment,   move   the   AVIONICS   MASTER POWER switch to the EXT PWR position.  This will de- energize the avionics power relay and allow power to be applied to avionics equipment. b.  AC Power.  AC power for the avionics equipment is provided by two inverters.  The inverters supply  115- volt  and  26-volt  single-phase  AC  power  when  operated by the INVERTER #1 or #2 switches (fig.  2-18).  Either inverter  is  capable  of  powering  all  avionics  equipment requiring  AC  power.    AC  power  from  the  inverters  is routed through fuses in the nose avionics compartment. 3-4.  MICROPHONES, SWITCHES AND JACKS. Boom, and oxygen mask microphones can be utilized in the aircraft. a.  Microphone Switches.  The pilot and copilot are provided with individual MIC control switches, placarded MIC/INTPH/XMIT, attached to respective control wheels.  A foot-actuated mic switch is also positioned on the floorboards forward of each pilot's seat. b.  Controls  and  Functions.   Microphone switches and jack functions are as follows: (1)  Control wheel switches (fig.  2-16). CONTROL FUNCTION MIC/INTPH Keys selected facility. XMIT switch MIC (Not depressed) Microphone is disconnected. 3-1