TM 1-1510-218-10 3-18 NOTE If  the  KLN  90B  is  in  the  OBS  mode,  the selected course (OBS) is displayed instead of the Desired Track (DTK).      D OSH DTK    303^o TK     302^o FLY L 2.7NM MSA  3300FT ESA  5500FT NAV 3 Figure 3-11.  NAV 3 Page (b)   Actual   Track   (TK).      The   aircraft's present track over the ground. (c)  Cross Track Error Correction.  This is a text means of indicating how far and which direction to get back on course.  It is consistent with the vertical deviation bar displayed on the NAV 1 page. (d)  Minimum  Safe  Altitude  (MSA).    The MSA displayed is the altitude defined by Jeppesen as Grid  Minimum  Off-Route  Altitude  (Grid  MORA).    This altitude is derived by Jeppesen for sectors that are 1° of latitude  by  1°  of  longitude  in  size.    One  degree  of latitude is 60 nm.  One degree of longitude is 60 nm at the equator and progressively less than 60 nm as one travels    away    from    the    equator.        One    degree    of longitude is approximately 50 nm at the southern most parts  of  the  U.S.  and  is  approximately  40  nm  at  the northern  most  parts  of  the  U.S.    The  MSA  altitude information    is    contained    in    the    database    and    is updated when the database cartridge is updated. The   MSA   provides   reference   point   clearance within  these  1°  latitude  by  1°  longitude  sectors.    A reference point is defined as a natural (peak, knoll, hill, etc.)  or  man-made  (tower,  stack,  tank,  building,  etc.) object.    Grid  MORA  values  clear  all  reference  points by   1000   feet   in   areas   where   the   highest   reference points  are  5000  feet  MSL  or  lower.    MORA  values clear all reference points by 2000 feet in areas where the highest reference points are above 5000 feet MSL.   The  KLN  90B  displays  dashes  for  areas  outside  the database  coverage  area  or  for  areas  where  the  Grid MORA is not defined. The MSA and ESA altitudes are advisory in nature   only.      They   should   not   be   relied upon  as  the  sole  source  of  obstacle  and terrain clearance. Refer to current aeronautical charts for appropriate minimum clearance altitudes.  (e)  Minimum    En    Route    Safe    Altitude (ESA).    When  the  KLN  90B  is  in  the  leg  mode,  the ESA  is  the  highest  MSA  from  the  present  position  to the  active  waypoint,  then  to  the  destination  waypoint via the active flight plan.  Refer to Figure 3-12.  When the  KLN  90B  is  in  the  OBS  mode,  the  ESA  is  the highest  MSA  from  the  present  position  to  the  active waypoint. Figure 3-12.  Minimum En route Safe Altitude (4)   NAV  4  Page.    The  NAV  4  page  is  used for altitude alerting and for advisory vertical navigation.   Refer to Figure 3-13. VNV INACTV IND 09000FT SEL:04000FT KMKC :-00NM ANGLE:-0.0^o ALTITUDE BARO:30.09” ALERT: ON WARN:+300FT E N R   -   L E G CRSR CRSR Figure 3-13.  Altitude Page and NAV 4 Page (a)  Altitude  alerting  allows  the  selection of  a  target  altitude  and  then  provides  a  visual  alarm 1000   feet   prior   to   reaching   the   selected   altitude, another  upon  reaching  the  altitude  and  another  for deviation from the selected altitude. WARNING