TM 1-1510-223-10 (13) Groundspeed or time-to-go display. Depressing  the  GSPD/TTG  button  on  the  display  control panel will cause groundspeed or time to go to alternately be displayed. GSPD/TTG information is always referenced to the active INS waypoint (14) To-from  indicator.    An  arrowhead  (white triangular box) in the center of the EHSI indicates whether the selected course is to or from the station or waypoint. The to-from annunciator will be removed from view during localizer operation. (15) Aircraft    symbol.       The    aircraft    symbol provides  a  quick  visual  cue  as  to  the  aircraft's  position with respect to the selected course and aircraft heading. (16) Preview    course    pointer.         A    preview course pointer (magenta) is provided to enable the pilot to preview data prior to its use. The preview course pointer will be displayed if: INS   is   displayed   as   the   navigation   source   on   the EHSI. LNAV  is  the  lateral  capture  mode  (green)  displayed on the EADI. Selection of V/L or TCN on the display controller after the above two conditions have been met The  preview  course  pointer  may  be  rotated  around the  heading  dial  using  the  remote  course  knob  on  the remote  instrument  control  panel,  located  on  the  pedestal extension   (fig.   3-14).      Each   time   the   preview   course pointer  position  is  changed  on  the  heading  dial  with  the remote  course  knob,  the  EHSI  digital  course  display  will show  the  preview  course  in  magenta  for  5  seconds,  or until the course is changed again. The   preview   course   deviation   bar   will   respond   to VOR, localizer, and TACAN signals as appropriate. Once the previewed navigation source is valid, if the approach  mode  (for  localizer  or  ILS)  or  VOR  approach mode  (for  VOR  or  TACAN)  has  been  selected  on  the flight director mode selector, the appropriate LOC, ILS, or NAV annunciator will be illuminated on the EADI. When the flight director determines that the capture point for    the    previewed    mode    has    been    reached,    it    will transition   the   flight   director   from   LNAV   mode   to   the capture  mode  of  the  previewed  navigation  source.    The preview   course   pointer   will   then   be   removed   and   the standard  course  pointer  will  be  slewed  to  the  previewed selected course. (17) Course    pointer.        The    course    pointer (yellow)  is  positioned  on  the  rotating  heading  dial  by  a remote course knob on the remote heading/course control panel, located on the pedestal extension (fig.  2-12).  The course pointer is set to a magnetic bearing that coincides with   the   desired   VOR   or   TACAN   radial,   or   localizer course.      Once   set,   the   course   pointer   maintains   its position    on    the    rotating    heading    dial    to    provide    a continuous  readout  of  course  error  to  the  flight  director computer.        Pulling    out    on    the    remote    course    knob (pedestal   extension,   fig.      2-12),   will   rotate   the   course pointer to center the course deviation bar. When  long  range  navigation  (INS)  is  selected,  the course   pointer   becomes   a   desired   track   pointer.      The desired  track  pointer  will  be  positioned  on  the  rotating heading dial by the INS. (18    Heading  display.    The  heading  display  is  a digital   readout   of   of   the   heading   selected   by   the   blue heading  marker.    The  display  is  placarded  HDG  (white) with blue numerals. (19) Double-needle     bearing     pointer     source annunciator.      This   annunciator   displays   the   navigation source supplying information to the double-needle bearing pointer   (green).      This   display   is   marked   by   a   green diamond  with  the  navigation  source  displayed  in  white letters.  Possible annunciations are ADF, VOR2, INS, and TCN. (20) Single-needle bearing pointer source annunciator.      This   annunciator   displays   the   navigation source supplying information to the single-needle bearing pointer (blue).  This display is marked by a blue circle with the navigation source displayed in white letters.  Possible annunciations are ADF, VOR1, INS, and TCN. (21) Weather   radar   tilt   angle   display.      The weather  radar  tilt  angle  display  (green)  shows  the  angle that    the    weather    radar    antenna    is    tilted    upward    or downward from level in degrees plus or minus. (22)    Weather    radar    mode    annunciator.        The weather  radar  mode  annunciator  indicates  the  operating mode  of  the  radar  system  Possible  annunciations  in  the full compass format of the EISI are TX (magenta) and WX (amber).    TX  indicates  that  the  radar  is  transmitting  but not   being   displayed.      WX   indicates   a   weather   radar system   failure.      Possible   annunciations   in   the   partial compass format are standby (STBY), test  EST), weather detection    (WX),    rain    echo    attenuation    compensation technique    (RCT),    ground    mapping    (GMAP),    and    fail (FAIL).      All   partial   compass   annunciations   are   green except FAIL, which is amber. (23) Weather   radar   target   alert   and   variable gain  annunciator.   The  green  TGT  annunciator  indicates that  the  target  alert  function  of  the  weather  radar  has been 3-33