TM 55-1510-220-10 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-12G   is   a   pressurized,   low   wing,   all metal    aircraft,    powered    by    two    PT6A-41    turboprop engines    (fig.        2-1    and    2-2),    and    has    all    weather capability.    Distinguishable  features  of  the  aircraft  are the    slender,    streamlined    engine    nacelles,    mission antennas, wing tip pods, 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 on the left side of the fuselage. 2-3. DIMENSIONS. Overall  aircraft  dimensions  are  shown  in  figure 2-3. 2-4. GROUND TURNING RADIUS. Minimum ground turning radius of the aircraft is shown in figure 2-4. 2-5. MAXIMUM WEIGHTS. Maximum    take    of    gross    weight    is    15,000 pounds.    Maximum  landing  weight  is  15,000  pounds. Maximum  ramp  weight  is  15,090  pounds.    Maximum zero fuel weight is 11,500 pounds. 2-6. EXHAUST DANGER AREA. Danger  area  to  be  avoided  by  personnel  while aircraft  engines  are  being  operated  on  the  ground  are depicted  in  figure  2-5.    Distance  to  be  maintained  with engines operating at idle are also shown.  Temperature and  velocity  of  exhaust  gasses  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  landing  gear  is  a  retractable,  tricycle  type, electrically operated by a single DC motor.  This motor drives  the  main  landing  gear  actuators  through  a  gear box  and  torque  tube  arrangement,  and  also  drives  a chain mechanism which controls the position of the nose gear.  Positive down-locks are installed to hold the drag brace  in  the  extended  and  locked  position.    The  down- locks are actuated by overtravel of the linear jackscrews and  are  held  in  position  by  a  spring-loaded  overcenter mechanism.    The  jackscrew  in  each  actuator  holds  all three   gears   in   the   UP   position,   when   the   gear   is retracted.  A friction clutch between the gearbox and the torque shafts protects the motor from electrical overload in   the   event   of   a   mechanical   malfunction.      A   150- ampere  current  limiter,  located  on  the  DC  distribution bus    under    the    center    floorboard,    protects    against electrical overload.  Gear doors are opened and closed through  a  mechanical  linkage  connected  to  the  landing gear.          The     nose     wheel     steering     mechanism     is automatically centered and the rudder pedals relieved of the  steering  load  when  the  landing  gear  is  retracted. Air-oil  type  shock  struts,  filled  with  compressed  air  and hydraulic  fluid,  are  incorporated  with  the  landing  gear. Gear  retraction  or  extension  time  is  approximately  six seconds. a. Landing   Gear   Control   Switch.      Landing   gear system  operation  is  controlled  by  a  manually  actuated, wheel-shaped switch placarded LDG GEAR CONTR UP DN, located on the left subpanel (fig.  2-6).  The control switch  and  associated  relay  circuits  are  protected  by  a 5ampere circuit breaker, placarded LANDING 2-1