TM 1-1510-224-10 NOTE Stored  heading  alignments  may  not be  completed  back  to  back.    Once  a stored   heading   alignment   has   been performed,  the  next  alignment  must be a normal alignment. (a) Stored heading shut down. 1. Come  to  a  complete  stop  in  desired aircraft parking position. 2. Wait     for STORED HEADING     to appear   in   the   advisory   box   on   the MFD.    This  will  take  approximately  5 minutes. 3. INS mode selector OFF. NOTE After completion of the stored heading   shutdown   the   aircraft   must not be moved until the stored heading alignment is complete. If  more  than  a  week  elapses  prior  to the  next  alignment,  a  stored  heading alignment should not be attempted. (b) Stored  heading  alignment.    This  procedure may be done before or after starting the engines.  If prior to  engine  start  (GPU),  the  complete  procedure  must  be done  before  engaging  the  starter  switch  to  ensure  the data is not dropped from the INS due to power drop. 1. INS mode selector STBY. 2. B   mode   selector   switch   Depress   to call up FPLN page. 3. R5   line   selector   switch   Depress   to call up NAV SETUP page. 4. R5   line   selector   switch   Depress   to call up INS SETUP page. 5. Valid alignment data     Enter into scratchpad "2" for last known as long as    it    reflects    the    correct    present position coordinates. 6. L1 Depress to enter position. 7. INS   mode   selector   NAV   (after   INS LOADING light goes out). 8. Wait    for    completion    of    alignment. This  will  take  7  to  8  minutes.    This can  be  confirmed  by  noting  that  the ALIGN  STATE  legend   at   L1   of   the INS SETUP page has disappeared. NOTE Do   not   move   the   aircraft   until   the alignment is complete. 3-28.    GLOBAL  POSITIONING  SYSTEM  (AN/ASN-149 ((B)3)). a. Description.    The  GPS  is  used  to  provide updated   position   information   to   the   inertial   navigation system   and   to   mission   equipment.      The   GPS   system consists  of  a  receiver-processer,  an  antenna  electronics unit,   and   an   antenna.      The   GPS   is   controlled   by   the aircraft   survivability   equipment/avionics   control   system (ASE/ACS). b. GPS Normal Operation. (1) Turn-On Procedure. 1. BATTERY switch (overhead control panel, fig.  2-15) ON. 2. AVIONICS MASTER POWER switch   (overhead   control   panel, fig. 2-15) ON. 3. #  1  3fAC  inverter  control  switch (mission  control  panel,  fig.    4-1) RESET, then ON. 4. A mode selection switch (multifunction   display,   fig.      4-2) Depress to select UTILITY page. 5. B mode selection switch (multifunction   display,   fig.      4-2) Depress to select  FLIGHT  PLAN page. 6. R5  line  selection  switch  Depress to select NAV SETUP page. 7. R4  line  selection  switch  Depress to select GPS SETUP page. NOTE On  the  GPS  SETUP  page,  data  fields are    filled    with    dashes    if    data    is unavailable   from   the   GPS   or   if   the data is invalid. 3-76