TM 55-1510-220-10 3-28.   AUTOMATIC FLIGHT CONTROL SYSTEM. a. Description. The     AP-106     is     an     integrated autopilot/flight director system that provides the following: (1) Heading mode. (2) Navigation mode. 1. Approach mode with automatic glideslope capture and track (3) Altitude hold mode. (4) Back course localizer mode. (5) Go-around mode. (6) Synchronized control wheel steering. (7) Indicated airspeed hold mode. (8) All-angle   adaptive   capture   for   VOR,   LOC, and LOC B/C. (9) Attitude display. (10) Heading display. (11) Mode selection indicators. (12) Elevator trim indicator. (13) System integrity warning flags. (14) Automatic yaw damping. (15) Turn and slip indicator. The   flight   director   and   autopilot   have   a   common computer  system.    When  the  autopilot  is  engaged,  the  flight control system controls the aircraft and the pilot monitors the flight  path  by  observing  the  information  displayed  on  the pilot's flight director indicator (FDI) and the pilot's horizontal situation indicator (HSI) (flight director system components). Autopilot/flight director commands are selected at the autopilot   mode   selector   panel   (fig.320),   located   on   the instrument  panel  (fig.    2-30).  Manual  roll  rate  and  pitch commands are inserted at the autopilot pitch-turn panel (fig. 3-23). Autopilot    operational    status    is    indicated    by    the autopilot/flight  director  annunciator  (fig.    3-22)  positioned above  the  pilot's  flight  director  indicator  on  the  instrument panel (fig.  2-30).  Two autopilot switches are also provided on each    control wheel (fig.  2-18).  One switch is placarded PITCH SYNC & CWS (pitch synchronize and control wheel steering),   and   the   other   is   placarded   DISC-TRIM-AP-YD (disconnect trim/autopilot/ yaw damp). The  automatic  flight  control  system  is  protected  by  a 10-ampere circuit breaker, placarded AP PWR, located on the overhead circuit breaker panel (fig.  2-27). b. Controls/Indicators  and  Functions.    The  following controls   and   indicators   are   provided   for   operation   of   the system. Autopilot mode selector control panel (fig.  320).  The autopilot/flight    director    commands    are    selected    by    ,the autopilot    mode    selector    control    panel,    located    on    the instrument  panel  (fig.    2-30).  Selection  is  accomplished  by pressing    the    face    of    the    appropriate    push-on/push-off annunciator  switches.    The  lateral  modes  are  HDG,  NAV, APPR  and  B/C.    When  not  in  a  lateral  mode,  the  flight director  command  bars  are  biased  out  of  view.    The  vertical modes are ALT hold, and IAS hold.  If a vertical mode is not selected,  the  pitch  hold  mode  is  automatically  operational. Selection of a mode causes the legend of that annunciator on the autopilot mode selector control panel to illuminate.  The self-test  switch  on  the  autopilot  mode  selector  control  panel acts  as  a  light  test  switch  when  depressed.    For  operation  at night,   overall   illumination   of   the   autopilot   mode   selector control panel and annunciator panel lights are adjusted by the PILOT INST LIGHTS light control, located on the overhead control panel (fig. 2-12). (1) HDG     switch. Engages     heading     mode. Commands   aircraft   to   acquire   the   heading   indicated   by heading marker on pilot's HSI. (2) NAV switch.  Engages navigation mode.  With VOR  1,  VOR  2  or  TACAN  selected,  commands  aircraft  to intercept  and  track  VOR  radial  selected  by  course  knob  on pilot's  HSI.    With  INS  selected,  commands  aircraft  to  track steering signals from INS system.  Intercept of approximately 45°  and tracking will be computed by the INS system. NOTE APPR cannot be selected with INS selected. (3) APPR    switch.        Engages    approach    mode. Commands  aircraft  to  intercept  and  track  ILS  or  localizer inbound course. 3-37