TM 1-1510-225-10 3B-178 The  system  performs  only  the  function  of weather  detection  or  ground  mapping.    It should     be     used     nor     relied     upon     for proximity warning or anti-collision protection. CAUTION Do    not    operate    radar    system,    even    in standby   mode,   without   115-Vac,    400-Hz power,     the     receiver-transmitter     cooling blower will not operate, which could result in circuit damage and/or automatic shutdown. In weather detection mode, storm intensity levels are displayed in three bright colors contrasted against a  deep  black  background.     Areas  of  heaviest  rainfall will   appear   in   red,   less   severe   rainfall   in   yellow, moderate  rainfall  in  green,  and  little  or  no  rainfall  in black (background). Range marks and identifying numerics, displayed in cyan, are provided to facilitate evaluation of storm cells.  The cyclic function further emphasizes the heavy rainfall areas (red) of the weather display by flashing them approximately once per second. Selection   of   the   map   function   causes   system parameters to be optimized on the three lowest ranges to improve resolution and identification of small targets at   short   ranges.      The   reflected   signal   from   various ground  surfaces  is  displayed  as  magenta,  yellow,  or cyan (most-to-least reflective). The    radar    system    consists    of    three    units: Indicator,   Receiver-Transmitter,   and   Antenna.      The indicator is mounted in the cockpit and contains all the controls   used   to   operate   the   radar.      The   Receiver- Transmitter is located on the radio rack.  The Antenna, which is fully stabilized for aircraft pitch and roll, is the avionics compartment in the nose of the aircraft. b.  Radar   System   Switches   and   Functions.    Refer to Figure 3B-140. (1)   INT  /  OFF.    Rotary  control  used  to  turn system on and off, and to adjust (intensity) of display.   Turn-on, STBY, and 100 will be displayed. (2)   Display Area.  Refer to Paragraph 3B -33c for details. (3)   10 / 25 / 50 / 100 / 200 / 300.  Momentary push  buttons  used  to  select  one  of  six  ranges.    For each  selected  range,  five  range  marks  are  displayed.   At   system   turn-on,   100-mile   range   is   automatically selected.    Internal  memory  for  range  push  buttons  is always active. (4)   TILT.    Rotary  control  used  to  select  tilt angle   of   antenna   beam   with   relation   to   earth   (with stabilization   on)   or   with   relation   to   airframe   (with stabilization off).  Clockwise rotation tilts beam  upward 0 to 10°; counterclockwise rotation tilts beam downward 0 to 10°. (5)   AZ   MK.      Slide   control   used   to   either display or not display azimuth markers at 30° intervals. (6)   STAB.  Slide control used to turn antenna stabilization ON or  OFF. (7)   TGT  ALRT.    Slide  control  used  to  turn target alert function   ON or   OFF.    When  enabled,  the letter  T  in  a  red  rectangle  is  displayed  to  identify  that target  alert  function  is  active.    Target  alert  is  active only  when  radar  gain  is  calibrated;  i.e.,  in  WX  with GAIN  PRESET  and  in  CYC  or  TEST.    The  symbol TGT  é  in  a  red  rectangle  is  displayed  and  flashes once   each   second   whenever   a   red-level   target   is detected  within  the  target  alert  section  (range  from  10 to 160 nm and within ±7.5° of aircraft heading).  Target alert    is    deactivated    automatically    when    operating controls are restored to valid alert settings. (8)   GAIN.  Rotary control with one fixed-gain detented position, PRESET.  Used to adjust sensitivity of  radar  receiver,  primarily  to  resolve  nearby  strong target    signals    while    ground   mapping.      Sensitivity increases    with    clockwise    rotation.        Full    counter- clockwise  rotation  to  detent  sets  gain  at  preset  level.   When   control   is   not   in   detented   position,   VAR   is displayed  unless  preset  gain  has  been  automatically selected. (9)   FRZ.    Momentary  push  button  used  to turn  freeze  function  on  or  off  with  alternate  presses.   When  freeze  is  selected,  display  is  not  updated  with incoming target return data.  To alert pilot, FRZ label is displayed and is flashed on and off once each second.   FRZ  is  automatically  deactivated  whenever  selection of    different    control    settings    dictate    a    change    in displayed data. At system turn-on, FRZ is automatically off. (10)   TEST.    Momentary  push  button  used  to select   a   special   test   pattern   to   allow   verification   of system  operation.    In  test  position,  transmitter  is  not enabled;   100-mile  range  and  preset  range  gain  are automatically selected; and TEST is displayed. (11)   MAP.    Momentary  push  button  used  to select ground-mapping display; MAP is displayed. WARNING