TM 1-1510-218-10 3-42 waypoints  in  the  active  flight  plan  do  not  affect  the ESA. (f)   When  the  active  waypoint  is  a  VOR or     approach     waypoint,     the     published     magnetic variation for the VOR or approach waypoint is utilized rather than the calculated magnetic variation. (4)   Switching  From  The  LEG  Mode  To  The OBS  Mode.    The  following  mode  transition  occurs  if the  KLN  90B  is  in  the  LEG  mode  and  the  mode  is changed to OBS. (a)  The waypoint  that  was  active  in  LEG mode  prior  to  the  mode  change  remains  the  active waypoint in OBS mode. (b)  The selected course is defined by two different  methods  depending  on  the  installation  and status of the unit. 1   If   the   KLN   90B   is   the   displayed navigation  source  when  the  change  is  made  to  the 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. 2   If the KLN 90B is interfaced with a compatible EFIS, electrically driven mechanical HSI, 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 3-7al(3). (5)   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. (a)  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. (b)  The   active   selected   course   in   the OBS mode prior to switching 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. (c)  With  the  exception  of  (b)  above,  the characteristics of normal DIRECT TO operation apply. (6)   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  direct  to  the  active  waypoint  when  the  KLN 90B is interfaced to a compatible EFIS, an electrically driven  mechanical  HSI,  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  HSI,  it  is  not  possible  for  the KLN    90B    to    change    the    OBS    value.        In    these situations,   the   KLN   90B   will   provide   a   scratchpad message that will announce the OBS value that should be selected to go direct to the active waypoint.  Refer to Figure 3-54. NAV 1 D  CRS 234       GGT DIS  20.0NM GS    154KT ETE     :08 BRG    234^o +    +    +    +    +        +    +    +    +    + Figure 3-54.  OBS DIRECT TO Course (7)   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 alternate between DIRECT  TO  and  ACTIVATE.    Ensure ACTIVATE   is   displayed.      Refer   to Figure 3-55.