TM 1-1510-225-10 3D-40 OBS  mode,  the  selected  course  becomes  whatever was  set  on  the  external  indicator  prior  to  changing  to the  OBS  mode.    This  value  should  normally  be  the desired  track  to  the  active   waypoint  that  was  already set  on  the  external  indicator  if  it  was  set  pictorially correct. (b)   If  the  KLN  90B  is  interfaced  with  a compatible EFIS, electrically driven mechanical EHSI, or   is   not   displayed   on   the   external   indicator,   the selected course is chosen  by  the  KLN  90B  such  that the  deviation  from  the  selected  course  remains  the same. (c)   If the OBS value chosen by default is unacceptable,  the  pilot  may  choose  the  OBS  value  as described in paragraph 3D-20.c. e.   Switching From the OBS Mode to the LEG Mode.    The   following  mode  transition  occurs  if  the KLN  90B  is  in  the  OBS  mode  and  is  switched  to  the LEG mode. (1)   The   active   waypoint,   while   in   the   OBS mode,   remains   the   active   waypoint   when   the   LEG mode  is  activated.    The  system  does  not  attempt  to orient itself on a leg of the active flight plan unless the TO / FROM indicator is indicating FROM.  In this case, the KLN 90B will reorient on the active flight plan. (2)   The  active  selected  course  in  the  OBS mode  prior  to  switch  to  a  LEG  mode  becomes  the desired track in the  LEG mode, unless the switch was made  on  the  FROM  side,  in  which  case  the  KLN  90B will calculate the correct desired track for the new leg. (3)   With    the    exception    of    (2)    above,    the characteristics of normal DIRECT TO operation apply. f.    Going DIRECT TO a Waypoint While in the OBS Mode.    The  DIRECT  TO  function  will  select  the OBS  value  that  will  take  the  aircraft  from  the  present position  directly  to  the  active  waypoint  when  the  KLN 90B is interfaced to a compatible EFIS, an electrically driven mechanical EHSI, or when  the  KLN  90B  is  not the    displayed    navigation    source    on    the    external indicator. If    the    KLN    90B    is    the    displayed    navigation source  on  a  non-driven EHSI, it is not possible for the KLN    90B    to    change    the    OBS    value.        In    these situations,   the   KLN   90B   will   provi de   a   scratchpad message that will announce the OBS value that should be selected to go direct to the active waypoint.  Refer to Figure 3D-54. NAV 1 D  CRS 234       GGT DIS  20.0NM GS    154KT ETE     :08 BRG    234^o +    +    +    +    +        +    +    +    +    + Figure 3D-54.  OBS DIRECT TO Course g.  Activating  a  Waypoint  While  In  the  OBS Mode.    While  in  the  OBS  mode,  a  waypoint  may  be activated by using the normal  DIRECT  TO method or by  a  second  method.    This  second  method  activates another    waypoint    without    changing    the    selected course.      When   the   new   waypoint   is   activated,   the deviation bar is not centered. 1.   Press the    D        button.    The  rules for the priority  of  waypoint  selected  for  direct  to operation apply. 2.   Press the   D    button a second time.  The annunciation     DIRECT     TO     changes     to ACTIVATE.    The  right  side  still  displays the appropriate waypoint page.  Repeated presses    of    the     D        button    alternates between    DIRECT    TO    and    ACTIVATE.   Ensure ACTIVATE is displayed.  Refer to Figure 3D-55. 3.   Press    the    ENT    button    to    approve    the waypoint page and activate the waypoint.   The   selected   course   does   not   change, therefore  this  method  does  not  re-center the    deviation    bar    like    a     DIRECT    TO  operation. ACTIVATE:   FINAL INT FINAL REF:  BTV RAD: 292.8^o DIS: 11.7NM N 44^o 25.40’ W 73^o 27.20’ E N R   :   0 9 0 E N T CRSR Figure 3D-55.  Activating a Waypoint