TM 1-1510-225-10 3B-142 Figure 3B-113.  Pilot Position Page Table 3B-75.  Pilot Position Page  (Continued) NO. DESCRIPTION/FUNCTION 1 Pressing  PSN  function  key will access the pilot position page. 2 Computed   magnetic   variation   at   present position. 3 This  line  select  key  is  non-operational if a computed wind speed is available or if the FMS is displaying an INU wind.   Otherwise,  the  following  three  actions  will occur: 1.   Selection   with   a   valid   entry   in   the scratchpad will enter the wind. 2.   Selection   with   an   empty   scratchpad will    copy    the    wind    entry    into    the scratchpad. 3.   Selection   with   a   -  in  the  scratchpad will set the wind speed to 0 knots. Table 3B-75.  Pilot Position Page  (Continued) NO. DESCRIPTION/FUNCTION 4 Track displays mag track. 5 Navigation source selected on pilot/copilot lateral steer pages. The status and validity of the navigational source are  indicated  on  the  title  lines  of  the  Pilot  Position pages.      Table   3B -76   lists   the   indications   and   their meanings.          Any     automatic     downgrading     of     the navigation source is annunciated on the CDU. A  nav   error   annunciation   and/or   the   HSI   flag are  provided  when  either  the  status  of  the  selected navigation   sensors   has   degraded   or   the   95%   error exceeds  a  threshold  determined  by  the  current  flight plan   guidance   mode;   EN   ROUTE,   TERMINAL,   or APPROACH.          When     these     alerts     are     provided, examine   the   current   state   of   the   GPS   navigation solution   and   compare   the   solution   to   the   other   on- board   navigation   systems.      If   necessary,   select   a different    navigation    sensor    to    provide    continued guidance of the aircraft. (a)   GPS  Display.    The  GPS  INAV  page shows    the    present    position    output    from    the    GPS receiver.  It also shows a 95% error figure of merit for the probable system accuracy, given the current GPS satellite   navigational   quality   (satellite   tracking   state and geometry) as shown in Figure 3B -114  and  Table 3B-77.    If  GPS/A/H  is  indicated  on  the  title  line,  the FMS-800 is using airspeed and heading sensor inputs to  smooth  the  GPS  data.    This  is  required  to  have  a valid  bank  (roll)  command  output  to  the  flight  director and autopilot. Table 3B-76.  Display of Navigation Mode on Position Pages SELECTED NAV SOLUTION DISPLAYED MODE CONDITIONS FOR DISPLAY GPS GPS/A/H GPS navigation data is smoothed with airspeed and heading. GPS GPS/ - /H GPS navigation data is being smoothed with GPS groundspeed and heading. GPS GPS/ - / -   GPS is not being smoothed with airspeed and heading data. GPS - - - /A/H GPS is invalid; FMS is dead reckoning with airspeed and heading data. MODEL MODEL The model aircraft function is providing the navigation solution.  This function is available only while on the ground.