TM 55-1510-222-10 (d)   GPS   key   connector.      Connects   GPS key. (e)   Load   switch.      This   pushbutton   switch initiates loading process. (f) Load  status  indicator  light.    Illuminates to indicate load status. (g)   Dust  cap.    Covers  GPS  key  connector when not in use. (h)   Observer microphone connector. Connects observer microphone. (i) GPS time of day switch. This pushbutton  switch  is  used  to  transmit  GPS  time  of  day to Have Quick II radios. c. GPS System Modes of Operation. (1)   Off Mode.  When the PULL OFF mode has been   selected,   power   is   removed   from   the   system, except panel lighting. NOTE Critical   memory   and   other   circuits which  cannot  be  turned  off  remain powered by batteries in the receiver. (2)   Initialize  Mode.    When  the  INIT  (initialize) mode  has  been  selected,  position  and  time  estimates can be entered via the keypad.  Waypoint data may be entered and examined, and option selections made.  No navigation functions can be performed. (3)   Navigation   Mode.      Selection   of   the   NAV (navigation)    mode    enables    normal    GPS    functions (satellite     tracking     and     navigation),     including     data transfer to and from other aircraft systems. (4)   Test  Mode.    Selection  of  the  PULL  TEST mode    initiates    a    full    command    test    of    GPS    user equipment for line replaceable unit (LRU) fault identification and isolation. d. GPS Normal Operation. (1)   GPS  Start  Procedures.    The  GPS  must  be initialized prior to being used for navigation.  There are three types of start: normal, quick, and cold.  A position estimate,  time  estimate,  and  almanac  (or  ephemeris) data are required for a normal start.  A quick start uses stored position, time, and recent ephemeris information. A  cold  start  is  used  only  when  the  GPS  is  unable  to perform a normal start-up. (a) GPS Normal Start. 1. Mode selector switch - INIT.  When built-in-test is complete the display will show data corresponding     to     the     data     selector     switch position. NOTE Data  display  will  not  be  illuminated for  about  30  seconds  after  GPS  has been   turned   on.      Ensure   that   the display bright- ness control has been set  to  the  full  clockwise  position  to receive  the  INIT  display,  then  adjust as desired. NOTE If  the  GPS  has  been  OFF  for  more than   30   seconds   when   INIT   mode was selected, the set will perform the initial built-in-test which takes approximately 30 seconds. 2. Data  selector  switch  -  POS.    If  ENTER  POS message  is  displayed  press  line  select  key  3 next to message.  Position must be entered. 3. Displayed position - Check.  Verify or enter new updated position and altitude as required. 4. Data  selector  switch  -  TRK-GS.    Verify  correct track   and   groundspeed   are   displayed.      If   not valid, enter correct values. 5. Slew key - Press.  Enter current time, year, and day of year on page 2. NOTE Prior to next step; ensure all required initialization  data  has  been  entered correctly, as they cannot be changed after selection of NAV mode. 6. Mode selector switch - NAV.  GPS will begin to search for satellite signals. NOTE If  COLD  alternates  with  the  figure  of merit display, the GPS is performing a cold start. 7. Data selector switch - STAT. NOTE The number of satellites (SAT) being acquired and tracked can be observed.    Estimated  position  error (EPE) and figure of merit (FM) can be monitored.    The  GPS  will  be  ready for   use   when   SAT   3   or   SAT   4   is displayed on STAT page 1. 3-72