TM 1-1510-225-10 3D-62 The height above airport  alert feature does not   serve   the   same   function   as   a   radar altimeter.  It does not provide any warning about the aircraft’s actual height above the airport’s surrounding terrain. CAUTION The  height  above  airport  alert  feature  will only be accurate if the barometric altimeter setting   is   correct.      If   the   height   above airport   function   is   enabled,   ensure   the barometric  altimeter  setting  is  correct  on the ALT page. (1)   When the height above airport is enabled, the   KLN   90B   creates   a   5-nm    radius    cylinder    of airspace  centered  on  an  airport.    This  airport  is  any airport that is a direct to waypoint or is the to waypoint in  the  active  flight  plan.    The  height  of  the  cylinder above the airport is the height selected on the SET 5 page.    The  KLN  90B  adds  the  selected  altitude to the elevation  stored  in  the  database  for  the  airport.    The KLN   90B   provides   an   altitude   alert   light   when   the aircraft first penetrates the cylinder. (2)   To enable or disable the height above the airport alert, press the left  CRSR button.  Use the left outer knob to position the cursor over the enable/disable field.  Turn the left inner knob to select ON or  OFF.    To  select  the  height,  use  the  left  outer knob to position the cursor over the altitude field.  Turn the left inner knob to select an offset between 800 and 2000 feet.  Press the left  CRSR button to turn off the cursor function. g.  The Setup 6 Page. Turn anticipation may be enabled  or  disabled  on  the  SET  6  page.    Refer  to Figure 3D-86.  Turn on the left cursor function and use the   left   inner   knob   to   select   between   ENABLE   or DISABLE.  If turn anticipation is disabled, navigation is provided   all   the   way   to   the   waypoint   and   waypoint alerting   occurs   approximately   36   seconds   prior   to actually reaching the waypoint. SET 6    TURN ANTICIPATE   ENABLE Figure 3D-86.  SET 6 Page h.  The Setup 7 Page.  The SET 7 page is used to select whether the altimeter setting used in the KLN 90B is made in inches of Mercury or millibars.  Refer to Figure    3D-87.        To    change    the    altimeter    setting between  inches  of  Mercury  and  millibars,  select  the SET  7  page,  press  the  left   CRSR  button,  and  rotate the   left   inner   knob   to   make   the   selection.      When finished,  press  the  left   CRSR  button  to  turn  off  the cursor function. SET 7 BARO SET   UNITS     “   INCHES Figure 3D-87.  SET 7 Page i.    The    Setup    8    Page.        The    Special    Use Airspace    (SUA)    alert    feature    may    be    enabled    or disabled on the SET 8  page.    Refer  to  Figure  3D-88.   After displaying the SET 8 page on the left side, press the left CRSR button to turn on the left cursor function.   The   left   inner   knob   is   used   to   display   AIRSPACE ALERT  ENABLE  or  AIRSPACE  ALERT  DISABLE.    If the   SUA   feature   has   been   enabled,   the   KLN   90B allows   the   selection   of   a   vertical   buffer   in   order   to provide a vertical warning of SUA.  To select a vertical buffer,  ensure  the  SUA  feature  has  been  enabled.   Press  the  left  CRSR  button  to  turn  on  the  left  cursor and  then  use   the  left  outer  knob  to  move  the  cursor over the first position of the vertical buffer.  Use the left inner  knob  to  select  each  number  and  the  left  outer knob   to   position   the   cursor.      The   buffer   may   be selected   in   100-foot   increments.      After   the   desired selection has been made, press the left  CRSR button to turn off the cursor function. WARNING