TM 1-1510-225-10 3C-9 receivers.    Approximately  1/2  dot  difference  will  result in a fault indication. (5)   Self-Test  (MNTR).    Checks  the  monitor 26   Vac    and   28   Vdc   supply   for   a   pre-determined voltage.    The  annunciator  is  illuminated  when  either voltage falls below this preset level. 3C-14.  ATTITUDE DIRECTOR INDICATOR. a.    Description.  The Attitude Director Indicator (ADI)    combines    the    attitude    sphere    display    with computed   steering   information   to   provide   the   pilot commands    required    to    intercept    and    maintain    a desired  flight  path.    It  also  contains  an  eyelid  display, expanded localizer, glideslope, rising radio altitude bar and  inclinometer.    The  indicator  has  go-around  and decision height annunciators.  Any warning flag in view indicates  the  respective  (ATT,  GS or   FD) information is unreliable.  Refer to Figure 3C-4. (1)   Go-Around     Annunciator     –     Illuminates when the go-around mode has been selected. (2)   Flight  Director  Warning   Flag  –  When  in view, it indicates flight director information is unreliable. (3)   Bank Angle Scale – The bank angle scale has  reference  marks  at  0,  10,  20,  30,  45,  60,  and  90 degrees to indicate angle of bank. (4)   Bank   Angle   Pointer   –   The   bank   angle pointer displays  actual  roll  attitude  through  a  movable pointer  that  points  to  the  angle  on  the  Bank  Angle Scale. (5)   Attitude  Warning  Flag  –  When  in  view, this  warning  flag  indicates  that  attitude  information  is unreliable. (6)   Decision Height Annunciator  – Illuminates when aircraft descends below selected decision height as set on the radio altimeter indicator. (7)   Glideslope     Scale     –     Displays     aircraft deviation    from    glideslope    beam    center    only    when tuned to ILS frequency and a valid glideslope signal is present.    The  glideslope  dot represents approximately 0.4° deviation from the beam centerline. (8)   Glideslope  Pointer  –  Indicates  aircraft  is below  glide  path  if  pointer  is  displaced  upward  and above glide path if pointer is displaced downward. (9)   Symbolic Miniature Aircraft – Serves as a stationary symbol of the aircraft.  Aircraft pitch and roll attitudes are displayed by the relationship between the fixed  miniature  aircraft  and  the  movable  sphere.    The symbolic   aircraft   is   flown   to,   and   aligned   with,   the command  cue  to  satisfy  the  commands  of  the  flight director mode selected. (10)   Radar Altitude Display Bar (Rising Runway)   –    For    added    backup    during    the    critical approach  phase  of  flight,  absolute  altitude  above  the terrain  is  displayed  below  200  feet  by  a  barber-pole radio  altitude  bar.    The  bar  appears  at  200  feet  and moves   toward   the   miniature   aircraft   as   the   aircraft descends toward the runway, contacting the bottom of the symbolic aircraft at touchdown. (11)   Expanded    Localizer    Scale    –    A    scale whose  width  equals  1/2°  of  the  localizer  beam  signal.   The   position   of   the   localizer   indicator   indicates   the aircraft’s   position   with   respect   to   the   center   of   the localizer. (12)   Expanded    Localizer    Indicator    –    Raw localizer     displacement     data     from     the     navigation receiver (HSI display) is amplified approximately 7–1/2 times  to  permit  the  expanded  localizer  pointer  to  be used as a sensitive reference indicator of the aircraft's position with respect to the center of the localizer.  It is normally used for assessment only, since the pointer is very sensitive and difficult to fly throughout the entire approach.    During  final  approach,  the  pointer  serves as an indicator of the Category II window. (13)   Inclinometer – Gives the pilot a conventional display of aircraft slip or skid and is used as an aid to coordinated maneuvers. (14)   Attitude    Test    Switch    –    Operates    the attitude self-test.  When pressed, the sphere will show approximately   a   20°   right   bank   and   a   10°   pitch-up attitude and the ATT warning flag will display. (15)   Lower   (Brown)   Eyelid   Display  –  Always shows the relative position  of  the  ground.    Surrounds bottom half of the attitude sphere and provides positive attitude identification.  The eyelids maintain the proper ground-sky  relationship,  regardless  of  the  position  of the    sphere,    facilitating    fast    recover    from    unusual attitudes.