TM 1-1520-218-10 3C-195 Section IV.  RADAR AND TRANSPONDER 3C-27.  WEATHER RADAR (KWX-58) SYSTEM   T1 . a.   Description.      The   KWX-58   color   weather radar   not   only   displays   in-flight   weather,   but   also permits  incorporation  of  the  KGR-358  radar  graphics unit.      The   color   weather   radar   is   used   to   detect significant   en   route   weather   formations   to   preclude undesirable    penetration    of    heavy    weather    and    its usually   associated   turbulence.      The   weather   radar system  provides  a  320  nm  display,  with  a  250  nm weather   avoidance   range   plus   weather   penetration advantages.  With the radar graphics unit in the NAV mode,   navigation   information   is   integrated   with   the weat her   display.      The   phased   array   antenna   (flat plate),   located   in   the   nose   of   the   aircraft,   is   fully stabilized to compensate for aircraft pitch and roll.  The antenna provides a full 90° scan angle, ± 12° tilt, and a 3.75   microsecond   pulse   width   in   both   weather  and ground mapping modes. (1)   Extended  Sensitivity  Time  Control  (STC) increases the displayed intensity of storms outside the normal  STC  range.    Extended  STC  relates  the  storm intensity  to  its  distance  and  assigns  a  corresponding color.      As   a   result,   the   display   presents   a   more accurate picture of storm intensity. (2)   Weather  systems  are  displayed  as  four colors,  depicting  rainfall  intensity  overlaid  with  range rings.  Bearing marks at dead ahead and 20° on either side aid the pilot in judging the bearing of storms and necessary heading changes. (3)   With   radar   graphics   interfaced,   a   circle mode  may  be  activated  by  pressing  the  page  button located on the radar graphics control panel.   Functional operation in this mode is the same as in the standard    display    mode    and    is    available    in    both weather  and  SBY  modes.    The  range  information  is displayed in the upper right corner and represents the outer    ring.        The    inside    ring    represents    half    the displayed distance.  The off screen pointer is replaced by an RMI BUG annunciation placed on the outer ring in the direction of the active waypoint and color coded to  each  navigation  system.    Position  of  the  aircraft  is indicated by the green airplane symbol in the center of the screen. (4)   Indicator     brightness     is     adjustable     to accommodate   varying  ambient  light  conditions  while automatically  maintaining  equal  brightness  between the   four   display   colors.      The   system   is   protected through a 5-ampere circuit breaker, placarded RADAR,    located    on    the    overhead    circuit    breaker panel, Figure 2-16. b.  Controls  and  Functions.     Refer  to  Figure 3C-144. (1)   Mode Selector Control Knob.  The mode selector  knob  is  used  to  turn  the  system  on/off,  and select SBY, TEST, WX, WXT, and MAP positions. (a)   SBY.    In  SBY  mode,  the  display  is blanked  and  transmitter  circuits  are  disabled  with  the magnetron heater remaining on. 1.  Mode Selector Control Knob 2.  RANGE Selector Control Knob 3.  TILT Control Knob 4.  BRIGHT / GAIN / MAX Control Knob 5.  OFF / STAB / ON Switch Figure 3C-144.  Weather Radar Control Indicator T1 (b)   TEST.    When  placed  in  the  TEST mode,  all  circuitry is activated, except the transmitter.   All  weather  colors  will  display  for  verification  in  the TEST   mode   as   well   as   the   WX,   WXT,   and   MAP modes. (c)   WX.    The  WX  mode  is  the  normal weather     mode     with     green     for     light,     yellow     for moderate,  red  for  heavy,  and  magenta  for  extremely heavy precipitation. (d)   WXT.    The  WXT  mode  is  used  to alert the pilot of weather that is beyond the displayed range.  Only returns of significant intensity between 83 and  320  nm  are  displayed  with  a  white  arc  at  the approximate azimuth of the storm.  A yellow  T on a red background  will  appear  in  the  upper  left  corner  of  the