TM  55-1510-221-10 NOTE If   WARN   light   illuminates,   proceed   to step  7;  otherwise  proceed  to  step  8. 7. Data  selector  -  DSRTK/STS. Observe   action   code   “02” and   malfunction   code   “49“. This  indicates  that  the  radial error   between   the   loaded position  and  the  INS  posi- tion  exceeds  33  nautical miles.   Operator   must   evalu- ate  possibility  that  either INS  is  in  error  or  reference point  position  is  incorrect.  It is  possible  to  force  INS  to accept   updated   position   by setting   data   selector   to   L/L POS  and  proceeding  to  step 8). 8. If displayed values are within tolerance, press HOLD   pushbutton   to   return INS   to   normal   operation.   If one  or  both  values  are  out  of tolerance,  proceed  to  step  9. 9.  Key  “2”  -  Press.  Observe  left data   display   is   “00000   N”; INSERT/ADVANCE and HOLD  pushbutton  lights  are illuminated. 10.   INSERT/ADVANCE   push- button   -   Press.   Observe INSERT/ADVANCE and HOLD  pushbutton  lights extinguish.  Present  position appears in data displays. Pres- e n t   p o s i t i o n   c h e c k   a nd update  is  complete. N O TE Within  30  seconds,  computer  will  process correction   and   revised   present   position will  appear  in  data  display.  If  AI  prior  to position  update  is  1  or  greater,  computer will  accept  over  95  percent  of  correction shown  in  difference  display.  If  AI  is  “0“, amount  of  correction  accepted  will  be  less and  is  a  function  of  time  in  NAV  mode and  number  of  updates  which  have  been made. (b.)  Extra  precision  geographic  pres- ent position check and update: 1. Data  selector  -  DSRTK/STS. 2.   Key   “2”   -   Press.   Observe INSERT/ADVANCE    push- button light illuminates, “000002”   appears   in   right data  display. 3.  INSERT/ADVANCE  push- button  -  Press.  Observe  right data  display  is  “1-XX2“, INSERT/ADVANCE    push- button   light   is   extinguished, and  any  TACAN,  GPS  or data  link  updating  is  discon- tinued. 4.   Data   selector   -   L/L   POS. Observe  latitude  and  longi- tude   of   present   position appears  in  left  and  right  data displays,   respectively. 5.  HOLD  pushbutton  -  Press (when  aircraft  passes  over known  position  reference.) Observe   HOLD   pushbutton light   illuminates.   Latitude and  longitude  in  data  dis- plays  freeze  at  values  present when   HOLD   pushbutton was  pressed. 6.   Load   latitude   by   pressing keys   in   sequence,   starting with  “N“  or  “S”  to  indicate north  or  south.  Example: 42°54.0’  North  =  N  4  2  5  4 0.  Observe  latitude  appears in   left   data   display   as   keys are  pressed. 7.  INSERT/ADVANCE  push- b u t t o n   - Press  Observe INSERT/ADVANCE and HOLD   pushbuttons   remain illuminated. 8.  Load  longitude  by  pressing keys   in   sequence,   starting with  “W”  on  “E”  indicating w e s t   or east. Example: 87°54.9’  West  =  W  8  7  5  4 9. 9.  INSERT/ADVANCE  push- button   -   Press.   Observe INSERT/ADVANCE and HOLD  pushbutton  lights remain  illuminated. 3-67