TM 1-1510-225-10 3D-18 altitude  button  to  bring  up  the  NAV  4 page   on   the   right   and   the   Altitude page on the right. The identifier for the active waypoint is automatically  displayed  on  the  NAV  4  page.    Prior  to programming  a  VNAV  operation,  the  top  of  the  page displays VNV INACTV. 2.     Press  the  appropriate    CRSR  button to turn on the cursor function if it is not already on. 3.     Enter  the  desired  altitude  in  the  SEL field. 4.     Using    the    outer    knob,    move    the cursor   to   the   offset   field   adjacent  to the active waypoint identifier.   Entering an offset allows reaching the desired  altitude  a  specified  distance before reaching the waypoint. Notice  that  the  bottom  of  the  NAV  4  page  now displays an angle.  To start the descent now using the displayed    descent    angle,    use    the    outer    knob    to position   the   cursor   over   the   ANGLE   field.      VNAV operation  is  initiated  by  bringing  the  cursor  over  the ANGLE  field.    By  leaving  the  cursor  off  of  the  ANGLE field,   the   angle   will   increase   as   flight   is   continued toward   the   waypoint.      When   the   desired   angle   is reached, position the cursor over the ANGLE field and VNAV will commence.  When VNAV begins, the top of the page displays an advisory altitude. 5.     A desired angle may be programmed.   The   CAL   4   page   may   be   used   to calculate a descent angle. To program a descent angle: a.   Using   the   outer   knob,   move   the cursor    to    the    ANGLE    field    and enter the desired descent angle.  If the  time  to  begin  the  descent  is greater    than    10    minutes,    VNV ARMED  will  be  displayed  on  the top line of  the  NAV  4  page.    If  the time  is  less  than  10  minutes,  the top  line  displays  a  countdown  to the time to begin descent. b.   Return   to   any   desired   page   for now.      If   the   NAV   4   page   was selected   by   pressing   the   altitude button,   press   the   altitude   button once again   to  return  to  the  pages previously  in  view.    If  the  NAV  4 page   was   selected   by   using   the outer  and  inner  knobs,  insure  the cursor  function  is  off  and  use  the outer and inner knobs to select the desired page. Approximately 90-seconds    before    the    time    to begin   the   descent,   the   message prompt   will   flash.      The   message page   will   display   VNAV   ALERT.   This is notification to view the NAV 4  page  because  it  is  getting  close to the time to begin the descent. c.   When the countdown reaches 0:00, the time will be replaced with an   altitude   advisory.      Begin   the descent so that the altitude displayed on the altimeter matches the altitude advisory. VNAV  on  a  flight  plan  is  virtually  identical.    The NAV  4  page  will  initially  contain  the  identifier  for  the active     waypoint.          VNAV     may     be     programmed referencing this waypoint or any waypoint in the active flight plan that is still in front of the aircraft’s position.   When   another   valid   waypoint   in   the   flight   plan   is entered  on  the  NAV  4  page,  the  aircraft’s  lateral  flight path is not altered. e.   NAV  5  Page.    The  NAV  5  page  provides  a navigation   graphics   presentation.      Refer   to   Figure 3D-14. NAV 5   1:KMDT   2:LRP   3:MXE   4:KPHL   5: E N R   -   L E G FPL 0 123^o 40 2 3 4 Figure 3D-14.  NAV 5 Page (1)   In   all   KLN   90B   installations,   there   are three common map orientations that may be selected on the NAV 5 page: a true north up display, a  desired track  up  display,  or  an  actual  track  up  display.    In addition,  if  the  KLN  90B  is  interfaced  with  the  engine trend  monitoring  system,  a  heading  up  presentation may also be selected.