TM 55-1510-222-10 CHAPTER 2 AIRCRAFT AND SYSTEMS DESCRIPTION AND OPERATION Section I.  AIRCRAFT 2-1. INTRODUCTION. The   purpose   of   this   chapter   is   to   describe   the aircraft, and its systems and controls which contribute to the  physical  act  of  operating  the  aircraft.      It  does  not contain  descriptions  of  avionics  or  mission  equipment covered    elsewhere    in    this    manual.        This    chapter contains  descriptive  information  and  does  not  describe procedures for operation of the aircraft. These procedures are contained within appropriate chapters in the manual.  This chapter also contains the emergency equipment  installed.    This  chapter  is  not  designed  to provide   instructions   on   the   complete   mechanical   and electrical   workings   of   the   various   systems;   therefore, each    is    described    only    in    enough    detail    to    make comprehension  of  that  system  sufficiently  complete  to allow for its safe and efficient operation. 2-2. GENERAL. The RC-12K is a pressurized, low wing, all metal aircraft,   powered   by   two   PT6A-67   turboprop   engines (fig. 2-1), having all weather capability.  Distinguishable features   of   the   aircraft   are   the   slender,   streamlined engine  nacelles,  four-bladed  propellers,  an  aft  rotating boom    antenna,    mission    antennas,    wing    tip    pods, stabilons,    a    T-tail,    and    a    ventral    fin    below    the empennage.    The  basic  mission  of  the  aircraft  is  radio reconnaissance.      Cabin   entrance   is   made   through   a stair-type door (fig. 2-1) aft of the wing on the left side of the fuselage. 2-3. DIMENSIONS. Overall aircraft dimensions are shown in figure 2- 2. 2-4. GROUND TURNING RADIUS. Minimum  ground  turning  radius  of  the  aircraft  is shown in figure 2-3. 2-5. MAXIMUM WEIGHTS. a. Takeoff.    Maximum  gross  takeoff  weight  is 16,000 pounds. b. Landing.  Maximum gross landing weight is 15,200 pounds. c. Maximum  Ramp  Weight.    Maximum  ramp weight is 16,110 pounds. d. Maximum   Zero   Fuel   Weight.      Maximum zero fuel weight is 12,700 pounds. 2-6. EXHAUST DANGER AREA. Danger  areas  to  be  avoided  by  personnel  while aircraft  engines  are  being  operated  on  the  ground  are depicted  in  figure  2-4.    Distance  to  be  maintained  with engines operating at idle are also shown.  Temperature and velocity of exhaust gases at varying locations aft of the exhaust stacks are shown for maximum power.  The danger area extends to 40 feet aft of the exhaust stack outlets.  Propeller danger areas are also shown. 2-7. LANDING GEAR SYSTEM. The retractable tricycle landing gear is electrically controlled and hydraulically actuated.  The landing gear -assemblies  are  extended  and  retracted  by  a  hydraulic power   pack,   located   in   the   left   wing   center   section, forward  of  the  main  spar.    The  power  pack  consists primarily of a hydraulic pump, a 28 VDC motor, a gear selector    valve    and    solenoid,    a    two    section    fluid reservoir, filter screens, gear-up pressure switch and low fluid  level  sensor.    Engine  bleed  air,  regulated  to  18  to 20  psi,  is  plumbed  into  the  power  pack  reservoir,  and the   system   fill   reservoir   to   prevent   cavitation   of   the pump.      The   fluid   level   sensor   activates   an   amber caution    annunciator,    placarded    HYD    FLUID    LOW located    in    the    caution/advisory    annunciator    panel, whenever the fluid level in the power pack is low.  The annunciator    is    tested    by    pressing    the    HYD    FLUID SENSOR TEST switch located in pilot's subpanel (fig. 2- 5). Power  for  the  hydraulic  power  pack  is  supplied through  a  landing  gear  motor  relay  and  a  60-ampere circuit  breaker  located  under  the  floorboard  forward  of the  main  spar.    The  motor  relay  is  energized  by  power furnished through a 2-ampere LANDING GEAR CONTROL circuit breaker located in the 2-1