TM  55-1510-221-10 NOTE The   directions   “N“   or   “S”   and   “E”   or “W“  are  established  during  normal  coor- dinate   entry.   Either   key   may   be   used   to initiate  entry  during  extra  precision  loads and  the  values  will  be  added  to  extra  pre- cision  value  without  affecting  direction. NOTE It  is  characteristic  of  the  computer  display routine  to  add  0.2  arc-seconds  to  any  dis- play  of  59.9  arc-seconds.  The  value  in computer  is  as  loaded  by  operator. 13. 14. 15. INSERT/ADVANCE  push- button  -  Press.  Observe  that right   data   display   indicates last   previously   inserted   alti- tude,  and  left  data  display  is blank. To  indicate  the  following load  is  altitude  -  Press  key “4“ or “6“. Observe INSERT/ADVANCE  push- button   light   illuminates. To  load  altitude  first  -  Press keys   in   sequence.   Example: 1230  ft  =  1230.  Numbers appear   in   right   data   display as  keys  are  pressed. NOTE Altitude  inputs  are  limited  to  15,000  feet. 16. 17. 18. INSERT/ADVANCE  push- button -   Press.   Observe pushbutton light extin- guishes. INSERT/ADVANCE  push- button  -  Press.  Observe  that left   data   display   indicates last previously inserted channel  number,  and  right data  display  is  blank. To  indicate  the  following load  is  channel  number  - Press key “2” or “8“. Observe INSERT/ ADVANCE  pushbutton  light illuminates. 19.   To   load   channel   number   - Press   keys   in   sequence. Example:  109  =  109.  Num- bers  appear  in  left  data  dis- play  as  keys  are  pressed. 20.   INSERT/ADVANCE   push- button -  Press.  Observe pushbutton light extin- guishes. NOTE Any  number  will  be  accepted  by  the  INS; however   only   stations   with   a   channel number  within  range  of  1  through  126 will  be  used  for  TACAN  mixing. NOTE The  channel  number  has  an  implied  “X“ suffix. NOTE Decimal  points  and  degree  symbols should   be   disregarded   when   reading   alti- tude  and  channel  number  displays. 21. INSERT/ADVANCE    push- button  -  Press.  Observe  sta- tion   latitude   and   longitude reappear. 22. Repeat steps -3- through -19- for  each  TACAN  station. 23. To  return  INS  to  normal  dis- play  modes,  momentarily  set data  selector  to  L/L  POS. (7.) Designating fly-to destinations: 1. 2. 3. Data  selector   -  L/L  WY  PT  or UTM  WY  PT,  as  required. Waypoint   thumbwheel   -   Select destination number. Observe number   of   destination   waypoint appears   in “TO” part of FROM-TO  display. Data selector   - HDG/DA. Observe  present  aircraft  heading appears, t o   n e a r e s t   t e n t h   of degree,   in   left   data   display;   also drift  angle, to   nearest   degree, appears  in  right  data  display. 3-60