TM 1-1510-225-10 3C-53 (6)   Radar Stabilization. The radar stabilization    system    is    designed    to    maintain    the antenna  beam  at the selected tilt angle relative to the earth's   surface.      The   stabilization   system   uses   the aircraft vertical gyros as a reference and is comprised of   electronic   amplifiers   in   the   Receiver/Transmitter interconnected with electro-mechanical components in the antenna. (7)   Level Flight.  Trim aircraft for straight and level   flight   in   smooth,   clear   air,   over   level   terrain.   Select a 50-mile range and set STAB to OFF. Rotate tilt control upward until all ground returns disappear.      Then   rotate   tilt   downward   until   ground returns  just  begin  to  appear.    After  several  antenna sweeps, check to see that ground returns are equally displayed.  If returns are only on one side of the radar screen    or    uneven    across    the    radar    screen,    this indicates     a     misalignment     of     the     radar     antenna mounting and should be corrected before proceeding.   Repeat   this   procedure   until   a   balanced   display   is achieved. Once the radar display is correct with stabilization off, select stabilization  ON and tilt upward once again to remove all returns.  Rotate tilt downward and check for even displays of ground returns.  If this test  indicates  improper  display,  possible  errors  in  the radar stabilization circuits or aircraft gyro exist. NOTE It is typical of a processing aircraft gyro to cause   ground   returns   to  first  appear  on one  side  of  the  display,  have them shift to the   opposite   side   of   the   display.      This precession   may   not   be   readily   apparent with respect to flight control instruments.  (8)   Turns. Once proper operation is established   in   level   flight,   rotate   the   TILT  control upward   in   1   increments   until   ground   returns   just disappear, rotate an additional 2 upward. Place  the  aircraft  in  a  standard  rate  turn  to  the right.    Note  the  radar  display.    It  should  be  free  of returns throughout the turn indicating proper stabilization alignment. If   returns   display   on   the   right   side   of   radar indicator, the radar system is understabilizing.  Targets on the left side of radar display indicate the system is overstabilizing. In  prolonged  turns,  gyro  precession  may  occur which  will  be  tracked  by  the  stabilization  system  and appear as undesirable ground targets on the indicator. d.    Maximum    Permissible    Exposure    Level (MPEL).      Heating   and   radiation   effects   of   weather radar  can  be  hazardous.    Personnel  should  remain  at a   distance   greater   than   5   feet   from   the   radiating antenna in order to be outside of the envelope in which radiation exposure levels equal or exceed 10 mW/cm₂.   The  distance  of  the  MPEL  boundary  is  calculated  for the  radar  system  on  the  basis  of  radiation  diameter, rated peak-power output, and duty cycle. 3C-35.  TRANSPONDER – APX-100.   Refer  to  Paragraph  3-5  for  information  on  the APX-100 Transponder. 3C-36.  LIGHTNING DETECTION SYSTEM (WX-1000E). a.     Description.          The     Stormscope     System consists of three components that detect, locate, and map    areas    of    vertical    electrical    discharge    activity contained within thunderstorms.  The antenna mounts externally     to     the     aircraft     and     detects     electrical discharges    associated    with    thunderstorms    over    a 125,000  square  mile  area  around  the  aircraft.    The processor analyzes this information to aid in identification of valid electrical discharges from lightning   and   to   determine   range   and   azimuth   for display  in  the  cockpit.    The  analysis  is  completed  in milliseconds.      The   location   of   a   vertical   electrical discharge associated with a thunderstorm is plotted on the    CRT    display    on    the    instrument    panel    as    an individual discharge point (+). b.    Controls and Functions.  (1)   Power/brightness Control.  Rotate to turn on the system and adjust the brightness of the display. (2)   Selector Buttons.  The specific function of each button is displayed adjacent to the button in each operating mode. c.     Normal Operation. (1)   Self Test.  Each time the system is turned on  it  will  automatically  cycle  through  a  series  of  self- tests    which    ensure    that    all    major    functions    are operating properly. These tests, which take approximately 15 seconds to complete, check antenna reception, processor circuitry calibration, memory and microprocessor  function,  and  proper  operation  of  the options.    After  proper  operation  has  been  verified  by the  self-test  program,  a  confirmation  message,  ALL TESTS  ARE  OK  will  display  in  reverse  video.    This message  will  remain  on  the  display  for  approximately 3 seconds and then will be replaced automatically with MAIN MENU.