TM 55-1510-222-10 4. INSERT/ADVANCE pushbutton - Press. Observe  TACAN  station  altitude,  in  feet,  will  appear  in right  data  display;  degree  symbol  and  decimal  points should be disregarded.  Left data display is blank. 5. INSERT/ADVANCE pushbutton- Press. Observe   TACAN   station   channel   number,   in   whole numbers, will appear in left data display; degree symbol and  decimal  point  should  be  disregarded.    Right  data display is blank. NOTE •    If   INSERT/ADVANCE   pushbutton is pressed, the normal coordinates   indicated   in   step   3 will be displayed. •    Waypoint     thumbwheel     may     be moved   at   any   time   and   normal coordinates for new TACAN station will be displayed. 6. Data    selector    -    Momentarily    to    any position    other    than    L/L    WY    PT,    UTM    WY    PT    or DIS/TIME.  (Returns INS to normal operation.) (u)   Magnetic heading. 1. Data selector - HDG/DA. Observe  true  heading  to  nearest  tenth  degree  appears in right data display. 2. Keys   3   and   9   -   Press   simultaneously and hold. Observe magnetic heading to nearest tenth of a degree appears in left data display.  Drift angle continues to be displayed in right data display. 3. Keys 3 and 9 - Release. Observe left data display reverts to true heading. (12) INS updating: (a)   Normal  geographic  present  position  check and update: 1. Data selector - L/L POS. Observe    latitude    and    longitude    of    present    position appear in left and right data displays, respectively. 2. Illuminated HOLD pushbutton - Press. Observe latitude and longitude in data displays freeze at values present when HOLD pushbutton is pressed. NOTE While HOLD pushbutton annunciator is illuminated, TACAN, GPS 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: 42 °  54.0' north = N 4 2 5 4 0. Observe    INSERT/ADVANCE    pushbutton    annunciator 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    annunciator 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:  87°     54.9'  west  =  W  8  7  5  4  9.    Observe longitude   appears   in   right   data   display   as   keys   are pressed. 6. INSERT/ADVANCE pushbutton - Press. Observe    INSERT/ADVANCE    and    HOLD    pushbutton annunciators  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    annunciator    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 position exceeds 33 nautical miles. Operator  must  evaluate  possibility  that  either  INS  is  in error or reference point position is 3-60