TM 55-1510-220-10 fore  a  low  voltage  shutdown  will  occur.  Then,  immediate corrective action must be taken. NOTE CDU  BAT  indicator will illuminate for 12 seconds   in   alignment   State   "8"   (about   5 minutes after turn-on).  This is normal and indicates  a  battery  test  is  in  progress.  No corrective action is required. NOTE During ground operation, it is recommended   that   operation   on   battery power not exceed 5 minutes. 5. To     determine     corrective     action: (Monitor  CD  U  displays  while  rotating  the  CDU  selector switch.) 1. If  displays  are  frozen  (do  not  change while   data   selector   is   being   rotated) problem  is  normally  in  the  navigation unit. 2. If displays respond normally to the data selector,     the     problem     is     normally absence of 115V AC power to INS. 6. For corrective action: Check to assure proper  settings  of  following  switches  and  circuit  breakers essential to INS operation: 1. Overhead circuit breaker panel  (fig. 2- 27) circuit breakers In. a. *AVIONICS MASTER CONTR b. *INS CONTROL c. *AVIONICS  MASTER  PWR  No. 1 d. *AVIONICS  MASTER  PWR  No. 2 2. Overhead    control    panel    (fig.    2-12): INVERTER  No.    I  or  INVERTER  No. 2 switch ON (either). 3. Mission control panel (fig. 4-1): a. 3-phase AC BUS switch ON. b. INS  POWER  &  AC  CONT  circuit breaker In. (19) Mission AC/DC Power Cabinet (fig.  4- 2).' (a) INS AC PWR circuit breaker In. NOTE CDU BAT indicator should extinguish after above   corrective   action.      If   it   remains illuminated, INS will eventually shut down when battery voltage drops below approximately 19 VDC.  Flight crew should prepare for shutdown. (20) Malfunction  indications  and  procedures:  Table  3-2 details the procedure for a Malfunction Code Check.  Table 3- 3   lists   a   number   of   malfunction   indications   which   occur under  given  modes  of  operation.    Follow  procedure  given. Table   3-4   details   action   codes   and   recommended   action. Table 3-5 lists failed test symptoms by malfunction codes and lists codes for recommended actions. (21) Reading    computer    memory    through    CDU    (look routine): (a)    WYPT CHG key Press. (b)    Keys  Enter "99".  Note  TOFROM displays "9". (c)    INSERT/ADVANCE      pushbutton Press. (d)   Data selector LIL WY  PT. (e)    CDU  Enter  "N"  followed  by  octal address    of    desired    (even    numbered) memory location. (f) Data     selector     L/L     WY          PT. Program  prevents  entry  of  an  address higher than 13777. (g)   Insure  waypoint  thumbwheel  is  at (0ls. (h)   INSERT/ADVANCE      pushbutton Press.    Observe  address  will  appear  in both data displays. (i) Data selector DST/TIME.  Observe most   significant   half   of   desired   data appears     in     left     display     and     least significant half appears in right display. Change 2       3-73