TM  55-1510-221-10 in  last  digit  of  right  display. AI  will  be  set  to  approxi- mately  three  times  the  num- ber  of  hours  in  NAV. (13.)  Flight  course  changes. (a.) tion: Manual flight plan change inser- 1. WYPT  CHG  pushbutton  - Press.  Observe  WYPT  CHG and INSERT/ADVANCE pushbuttons    illuminate. 2.   Select   new   FROM   and   TO waypoints  by sponding   keys pressing  corre- 3.  WYPT  CHG  pushbutton  - Press. Observe new waypoint  numbers  appear  in FROM-TO   data   displays   as keys  are  pressed. NOTE Selecting   zero   as   FROM   waypoint   will cause  desired  track  to  be  defined  by  com- puted   present   position   (inertial   present position  plus  fixes)  and  TO  waypoint. 4.   INSERT/ADVANCE   push- button -   Press.   Observe WYPT   CHG   and   INSERT/ ADVANCE pushbuttons extinguish. NOTE Waypoint  zero  always  contains  ramp coordinates  if  no  manual  flight  plan changes  are  made.  When  a  manual  flight plan  change  is  made,  present  position  at instant  of  insertion  is  stored  in  waypoint zero. (14.)  After  landing  procedures: If  INS  will  be  unattended  for  an  extended period,  it  should  be  shut  down. Do  not  leave  INS  operating  unless  aircraft or  ground  power  and  cooling  air  are  avail- able  to  system. NOTE The  INS  may  be  shut  down,  downmoded to  STBY  or  ALIGN  mode,  or  operated  in the   navigation   mode   after   landing.   The determining   factor   in   choosing   course   of action   is   expected   length   of   time   before the  next  takeoff. NOTE Do  not  tow  or  taxi  aircraft  during  INS alignment.   Movement   during   alignment requires   restarting   alignment. (a.)   Transient   stops. NOTE Action  to  be  taken  during  a  transient  stop depends   upon   time   available   and   on availability   of   accurate   parking   coordi- nates   (latitude   and   longitude.) 1.   Realignment   -   INS   operat- ing. (Recommended  if  sufficient  time  and  accurate parking   coordinates   are   available.) NOTE INS   can   be   downmoded   to   perform   a realignment  and  azimuth  gyro  calibration. Alignment   to   produce   an   alignment   state number  of  “5”  can  be  accomplished  in approximately  17  minutes.  During  the  17 minute  period,  an  automatic  azimuth gyro   recalibration   is   determined   on   basis of   difference   between   inertial   present position   before   downmoding   and   inserted present  position.  To  obtain  further  refine- ment   of   azimuth   gyro   drift   rate,   calcu- lated  on  basis  of  newly  computed  error data,  INS  can  be  left  in  alignment  mode for  a   longer  period,  allowing  the  align- ment   state   number   to   attain   some   value lower  than  “5“. 2.   Data   selector   -   STBY,   then to  ALIGN. 3.   Present   position   coordinates -  Insert,  according  to  proce- dure: “Geographic   Present Position I n s e r t i o n ”    or “UTM  Present Position 3-70