number  in  all  navigation  computations.  If  INSERT/ ADVANCE  key  is  not  pressed,  computer  will  con- tinue  using  original  numbers  in  all  navigation  com- putations;   but   distance/time   information,   based   on new  leg,  may  be  called  up  and  read  in  data  displays (in  case  of  waypoints).  When  not  in  TACAN  mix mode,  TACAN  station  number  is  inserted  to  display DIS/TIME    information. (10.)  WYPT  CHG  key.  When   pressed, enables  numbers  in FROM-TO   display   to   be changed.   If   INSERT/ADVANCE   key   is   pressed, computer  will  use  navigation  leg  defined  by  new (11.)   AUTO-MAN   TEST   switch.   This  is  a dual   purpose   control.   When   the   knob   is   pressed inward,  the  TEST  switch  function  is  engaged.  When the  knob  is  rotated  to  either  the  AUTO  or  MAN  set- ting,  the  control  serves  as  a  selector  between  those modes. (a.)  AUTO.  Selects   automatic   leg switching  mode.  Computer  switches  from  one  leg  to the  next  whenever  waypoint  in  TO  side  of  the FROM-TO  display  is  reached. (b.) MAN.  Selects  manual  leg  switch- ing  mode.  Pilot  must  make  waypoint  changes  manu- ally. (c.)   TEST.   When  pressed,  performs test   of   INS   lights   and   displays,   remote   lights   and indicators   controlled   by   INS,   and   computer   input/ output   operations. Used   with   other   controls   to   activate   display   of numerical   codes   denoting   specific   malfunctions   and resets   malfunction   warning   circuits. During   alignment,   activates   the   HSI   test.   Con- tinued  pressing  of  switch  provides  constant  INS  out- puts  to  drive  cockpit  displays  in  a  predetermined fashion. NOTE The   INS   can   provide   test   signals   to   the Horizontal   Situation   Indicator   (HSI)   and connected  displays.  Pressing  TEST  switch during   STBY,   ALIGN,   or   NAV   modes will  cause  all  digits  on  connected  digital displays  to  indicate  “S’s“  and  illuminates the  HSI  “WAYPOINT”  and  ALERT lights.  Additional  HSI  test  signals  are  pro- vided  when  INS  is  in  ALIGN  and  the data  selector  is  at  any  position  other  than DSRTK/STS.   Under   those   conditions, pressing  TEST  switch  causes  the  HSI  to indicate   heading,   drift   angle,   and   track angle  error  -  all  at  “0°“  or  “30°“.  At  the same   time,   cross   track   deviation   is   indi- cated   at   “3.75“   nautical   miles   (one   dot) TM  55-1510-221-10 right  or  left  and  INS-controlled  HSI  flags are  retracted  from  view. Output   test   signal   are   also   supplied   to   the autopilot  when  INS  steering  is  selected.  Rotating AUTO-MAN  switch  to  AUTO  and  pressing  TEST during  align  furnishes  a  15°  left  bank  steering  com- mand.   A   15°   right   bank   steering   command   is   fur- nished  when  the  AUTO/MAN  switch  is  set  to  MAN. (12.)   FROM-TO   display.   Display   numbers defining  waypoints  of  navigation  leg  being  flown  or, in  the  case  of  a  flashing  display,  displays  TACAN station  being  used.  Waypoint  numbers  automatically change   each   time   a   waypoint   is   reached.   Unless flight  plan  changes  during  flight,  the  automatic  leg switching  sequence  will  always  be  1,  2,  2  3,  3  4....8 9,  9  1,  1  2,  etc. (13.)   Data   selector.   Selects  data  to  be  dis- played  in  data  displays  or  entered  into  INS.  The rotary  selector  has  10  positions.  Five  positions  (L/L POS,  L/L  WY  PT,  UTM  POS,  UTM  WY  PT  and DSRTK/STS)  also  allow  data  to  be  loaded  into  data display   then   inserted   into   computer   memory. (a.)   TK/GS.   Displays   aircraft   track angle  in  left  display  and  ground  speed  in  right  dis- play. (b.)  HDG/DA.  Displays   aircraft   true heading  in  left  display  and  drift  angle  in  right  dis- play. (c.)   XTK/TKE.  Displays   cross   track distance  in  left  display  and  track  angle  in  right  dis- play. (d.)  L/L  POS.  Displays  or  enters present  aircraft  position  latitude  in  left  data  display and   longitude   in   right   data   display.   Both   displays indicate   degrees   and   minutes   to   nearest   tenth   of   a minute.   This   position   also   enables   the   insertion   of present  position  coordinates  during  alignment  and present   position   updates. (e.) L/L  WY  PT.  Displays   or   enters waypoint  and  TACAN  station  data,  if  used  in  con- junction  with  the  waypoint/TACAN  selector.  This position   will   also   cause   display   of   inertial   present position   data   when   the   HOLD   key   is   illuminated. (f.)  DIS/TIME.  Displays    distance from  aircraft  to  TACAN  station  or  any  waypoint,  or between  any  two  waypoints  in  left  display.  Displays time  to  TACAN  station  or  any  waypoint,  or  between any  two  waypoints,  in  right  display. (g.)   WIND.   Displays   wind   direction in  left  display  and  wind  speed  in  right  display,  when true   airspeed   is   greater   than   the   air   data   system lower  limit  (115  to  400  KIAS). 3-49