TM 55-1510-222-10 pushbutton,     any     incorrectly     loaded     data     can     be corrected    by    pressing    the    CLEAR    pushbutton    and loading correct data. a.    Data selector L/L POS. Observe    that,    prior    to    initial    load,    the    INSERT/ ADVANCE pushbutton annunciator is illuminated. b.  To load latitude data Press 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 that latitude appears in left data display as keys are pressed. c.  INSERT/ADVANCE pushbutton Press. Observe pushbutton annunciator remains illuminated. d.        To    load    longitude    data    Press    keys    in sequence,  starting  with  W  or  E  to  indicate west or east. Example:  87°  54.9' West = W 8 7 5 4 9.  Observe that longitude   appears   in   right   data   display   as   keys   are pressed. e. INSERT/ADVANCE pushbutton Press. Observe pushbutton annunciator extinguishes. f.  Data selector DSRTK/STS.  Confirm: (1)   Left   data   display   indicates   desired track angle in computer memory. (2)  Right  data  display  indicates  ---84,  --- 74,    ---64,    or    ---54,    depending    on which  alignment  state  the  computer has reached. NOTE After present position has been inserted  and  computer  has  advanced to state 7, present position cannot be reinserted    without    downmoding    to STBY and restarting alignment. g.    Data  selector  (CDU)  DSRTK/STS.    Observe left-hand  data  display  indicates  the  desired track   in   computer   memory   and   right   data display indicates status --194-. NOTE If  fourth  digit  from  right  is  blank,  a valid   heading   has   not   been   stored. Proceed with normal preflight procedure. h.      Monitor   data   display   for   system   alignment state  9  to  alignment  state  8.    Observe  right data display will be ---- 184-. i.  Monitor data display for malfunction codes. Observe  if  the  26V  400  Hz  power  is  off,  .03184  will appear in the right data display and WARN annunciator illuminates.  If magnetic compass system is off, .03184 will appear in right data display and WARN annunciator is extinguished. j.      If   there   are   malfunction   codes,   proceed   to ABNORMAL PROCEDURES in this chapter. NOTE To achieve best accuracy, engine start and  heavy  loading  activity  should  be delayed until entry into NAV mode. NOTE Way-point   data   and   TACAN   station data   may   be   loaded   any   time   after turn-on. (3) Verify UTM Grid Coefficients: 1.    Data  selector  (CDU)  -  UTM  WY PT. 2. Keys 5 and 9 - Press simultaneously. Observe  TO-FROM  display  is  blank.    Earth  flatness coefficient  appears  in  left  display.    The  relative  earth radius, in meters, appears in right display. NOTE These  values  are  retained  from  turn- on   to   turn-on   unless   changed   by operator. 3.    Verify  that  values  correspond  to those required for spheroid being used. NOTE Values    for    various    spheroids    are listed in table 3-2. 4.  If values are correct, return CDU to  normal  display  mode  by  momentarily  setting  data selector to any position except UTM WY PT.  If values are to be changed, continue with following steps: 3-48