TM 55-1510-221-10 which  is  concentric  with  the  DH  SET  knob.  The dimming  knob  also  dims  the  distance  and  course display on the pilot’s HSI, and the altitude alert dis- play. (19.) Expanded  localizer.  Raw  localizer  dis- placement  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 posi- tion, 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. Full  scale  deflection  of  the  expanded  localizer pointer  is  equal  to  1/4  degree  of  beam  signal.  The expanded   localizer   is   displayed   by   the   localizer pointer  only  when  a  valid  localizer  signal  is  avail- able. (20.)  Inclinometer.  Gives  the  pilot  a  con- ventional display of aircraft slip or skid, and is used as an aid to coordinated maneuvers. (21.) Rate of turn. Rate of turn is displayed by the pointer at the bottom of the ADI. The marks at the extreme left and right sides of the scale repre- sent a standard rate turn. (22.)  Attitude  (ATT)  test  switch.  W h en depressed,  the  sphere  will  show  an  approximate  atti- tude  change  of  20  degrees  of  right  bank  at  10 degrees  pitch-up.  The  ATT  warning  flag  will  appear. In addition, all mode annunciator lights except DH will  illuminate. (23.) Radio altitude (RA) test switch. Press- ing the RA test button causes the following displays on the radio altitude readout: all digits display 8’s then dashes, and then the preprogrammed test alti- tude as set in the radio altimeter R/T unit, until the test button is released at which time the actual alti- tude  is  displayed.  The  DH  display  during  the  test displays  all  8’s  with  the  altitude  display  and  then displays  the  current  set  altitude  for  the  remainder  of the test. RA test is inhibited as a function of APR CAP. (24.) Decision  height  (DH)  display.  The  dig- ital DH display, displays decision height range from 0  to  990  feet  in  10  foot  increments.  The  decision height is set by the knob in the lower right corner of the ADI. (25.) 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 mov- able sphere. The symbolic aircraft is flown to align the command cue to the aircraft symbol in order to 3-26 satisfy the commands of the selected flight director mode. (26.) Glide slope scale and pointer. Displays aircraft deviation from glide slope beam center only when  tuned  to  a  ILS  frequency  and  a  valid  glide slope is present. The aircraft is below glide path if pointer  is  displaced  upward.  The  glide  slope  dot  rep- resents  approximately  0.4  degree  deviation  from  the beam  centerline. 3-20. COPILOT’S GYRO HORIZON INDICATOR. a.   Description.  The  copilot’s  gyro  horizon indicator  (fig.  3-13)  is  a  flight  aid  which  indicates the aircraft’s attitude. The attitude given is in rela- tionship to an artificial horizon. There are no front panel  fuses  or  circuit  breakers  provided  for  the  copi- lot’s gyro horizon indicator. b.  Indicators  and  Functions. (1.)  Bank  angle  scale.  Indicates   aircraft bank angle from zero to 90 degrees with marks at 10, 20, 30, 45, 60, and 90 degrees. (2.)  Bank  angle  index.  Reference   indicat- ing  zero-degree  bank. (3.) Bank angle pointer. Indicates aircraft bank angle. (4.)   Horizon   line. Affixed  to  sphere, remains parallel to the earth’s horizon at all times. (5.)  G  flag.  Presence   announces   loss   of power. (6.)  Sphere.  Indicates  orientation  with earth’s axis at all times. (7.)  Inclinometer.  Assists   the   copilot   in making  coordinated  turns. (8.)  Miniature  aircraft.  Indicates   attitude of aircraft with respect to the earth’s horizon. 3-21. TURN AND SLIP INDICATORS. a. Description.  The  pilot  and  copilot  have identical  turn  and  slip  indicators  (fig.  3-14)  pro- tected  by  the  circuit  breaker  placarded  TURN  & SLIP  on  the  overhead  circuit  breaker  panel  (fig. 2-26). b. Controls/Indicators and Functions. (1.)  Two-minute  turn  marks.  Fixed  mark- ers indicate two-minute turn rate when covered by turn  rate  indicator.