TM 55-1510-219-10 (17) INS updating. (a) Data link updating. 1. Mode selector NAV. 2. Data selector DSRTK/STS. 3. Key "3" Press. (Observe right data display is "000003" and INSERT/ADVANCE pushbutton lamp is illuminated.) 4. INSERT/ADVANCE pushbutton Press. (Observe right data display is "1-XX3" and INSERT/ADVANCE pushbutton light is extinguished.) 5. Monitor "DAT LINK UPDATE" annunciator on mission control panel. (Observe  illumination  will  be  within  30  seconds,  if correction of less than 3 + AI nmi is being transmitted to INS.) 6. The  Accuracy  Index  (AI)  will decrement to "O" as updating progresses. (b) Normal  geographic  present  position check and update: 1. Data selector LIL POS. (Observe  latitude  and  longitude  of  present  position appear in left and right data displays, respectively.) 2. HOLD  pushbutton  Press  until illuminated. (Observe   latitude   and   longitude   in   data   displays freeze   at   values   present   when   HOLD   pushbutton   is pressed.) NOTE While   HOLD   pushbutton   light   is illuminated,  TACAN  and  data  link updates are inhibited. 3. Keys   Press   in   sequence   to load latitude of position reference, starting with "N" or "S" to indicate north or south. (Example: 4254.0' north = N 4 2 5 4 0.) (Observe INSERT/ADVANCE pushbutton light illuminates    when    first    key    is    pressed,    and    latitude appears in left data display as keys are pressed.) 4. INSERT/ADVANCE pushbutton Press. (Observe INSERT/ADVANCE pushbutton light remains   illuminated,   and   previous   value   of   latitude reappears.) 5. Keys   Press   in   sequence   to load longitude of position reference, starting with "W" or "E" to indicate west or east. (Example:  8754.9'  west  =  W  8  7  5  4  9.    Observe longitude   appears   in   right   data   display   as   keys   are pressed.) (Observe INSERT/ADVANCE and HOLD pushbutton lights remain illuminated.  North position error and east position error, in tenth of a nautical mile, will appear in left and right data displays, respectively.) NOTE If WARN lamp illuminates, proceed     to     step     8;     otherwise proceed to step 9. 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    position    exceeds    38 nautical  miles.    Operator  must  evaluate  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 (h). 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   the   step (10). 9. Key "2" Press. (Observe left data display is "00000 N"; INSERT/ADVANCE   and   HOLD   pushbutton   lights   are illuminated.) 10. INSERT/ADVANCE pushbutton Press (Observe INSERT/ADVANCE and HOLD pushbutton lights   extinguish.      Present   position   appears   in   data displays.        Present    position    check    and    update    is complete.) 3-63