TM 1-1510-225-10 3B-20 (16)   Distance    of    Bearing    Source.        When distance  is  available  for  the  selected  bearing  source the distance source and the distance in nautical miles to the NAV source is displayed in the upper left corner of  the  MFD.    When  the  bearing  source  is  FMS  the active waypoint is displayed as the distance source.  If the bearing source  is  VOR,  DME  will  be  displayed  as the distance source. NOTE If  an  offside  FMS  is  selected  for  Bearing Data/Distance and it is not activated as the primary   NAV   source   on   the   off-side,  the distance/bearing    information    will    not    be displayed.  This is caused by the method of data importation into the EHSI displays.  If the    offside    FMS    data    is    required,    the offside     primary     NAV     source     must     be selected. The distance readout displays tenths of a mile up to 99.9 nm, and above 99.9 nm it displays whole miles.   If VOR  is the selected course source and the VOR is in  DME  hold  mode,  a  cyan  H  is  annunciated  to  the right of the DME distance. When the distance is invalid, the digital portion of the   readout   is   replaced   with   red   dashes.      If   the distance    is    unavailable    the    digital   portion   of   the readout blanks.  When the bearing source is invalid or not available, the distance source is replaced with the bearing source annunciation drawn in black on a solid red box. (17)   Bearing  Source.    The  bearing  source  is identified in cyan in the upper left corner of the EHSI below the Course Source/Distance.  When the bearing is  unavailable,  the  needle  is  removed  but  the  source annunciation  remains.    When  the  bearing  source  is invalid, the needle is removed from the display and the bearing   source   annunciation   is   replaced   with   the source abbreviation drawn in black on a solid red box. (18)   Course Source Distance Readout.  When distance is available for the selected course source the distance  source  and  the  distance  in  nautical  miles  to the NAV source is displayed in the upper left corner of the   MFD.      If   the   course   source   is   FMS   the   active waypoint  is  displayed  as  the  distance  source.    If  the course   source   is   VOR,   DME   is   displayed   as   the distance source.  If TCN is the course source, TCN is displayed as the distance source. The distance readout displays tenths of a mile up to 99.9 nm, and above 99.9 nm it displays whole miles.   If VOR is the selected course source and the VOR is in  DME  hold  mode,  a  white  H  is  annunciated  to  the right of the DME distance. When the distance is invalid the digital portion of the   readout   is   replaced   with   red   dashes   and   the distance  source  is  replaced  with  the  course  source annunciation.        If    the    distance    is    unavailable    the distance  identifier  is  replaced  with  the  course  source annunciation and digital portion of the readout blanks. (19)   Free Format Line.   The free format line is a  32-character  message  line  filled  by  the  FMS-800.   The  FMS-800  controls  the  content  of  the  message, color,  and  flashing  of  characters.    The  message  line displays the active and last tuned ARC-210 frequencies.  The left side of the message line consists of the active communication call sign and frequency in green.  The right side of the message line consists of the last-tuned communication call sign and frequency in cyan. (20)   Digital Heading Bug Readout.  Located to the  right  of  the  Course  Source/Distance.    When  the selected    heading    changes    the    selected    heading readout is displayed.  If the selected heading does not change  for  10  seconds,  the  selected  heading  readout is removed from the display.  If the heading bug is off the screen, the readout will be constantly displayed. (21)   Heading    Bug.        The    heading    bug    is magenta and travels around the aircraft symbol on the outside    edge    of    the    compass.        It    travels    in   1 increments.    The  center  of  the  heading  bug  indicates the   selected   heading   in   1  increments.    When  the heading  bug  or  heading  source  is  invalid,  the  heading bug is not displayed. (22)   Track    Indicator.        The    track    indicator shows the actual course of the aircraft.  It is drawn as a  cyan  diamond.   It  travels  around  the  aircraft  symbol on the inner edge of the compass rose, such that the bottom of the indicator points into the compass and is aligned  with  the  track  value  on  the  compass.    The track    indicator    is    removed    from    the    display   if   it becomes invalid or unavailable.  The track indicator is displayed    in    yellow    when    a    cross-side   source   is selected. (23)   Digital   Aircraft   Heading   Readout.      The compass  rose  rotates  about  the  aircraft  symbol  such that the current heading is graphically indicated below the lubber line.  Within the white lubber line symbol is a  white  digital  heading  readout.    The  lubber  line  is located  directly  above  the  aircraft  symbol  along  the outside of the compass rose. When  the  heading  is  invalid,  the  bearing  pointer and the HSI go into OBS backup modes. When the heading is invalid, the heading readout is   removed   from   the   display   and   replaced   with   the