TM 1-1520-218-10 3C-170 Figure 3C-122.  GPS RAIM  Table 3C-84.  GPS RAIM Procedure NO. DESCRIPTION/FUNCTION 1 Indicates    the    current    state    of    active RAIM solution. 2 Pressing     line     select     key     RAIM     will access the RAIM/prediction page. 3 Expected   state   of   RAIM  a vailability  at destination. 4 Select to disable nuisance RAIM annunciations. 5 Indicates   Estimated   Time   of   Arrival   at destination. 6 Destination of interest for RAIM The  FMS-800  provides  an  active  RAIM  solution at present position.  By tracking GPS satellite state-of- health  and  orbital  geometry,  the  FMS-800  is  capable of  determining  when  the  GPS  navigation  solution  is degraded  or  suspect  due  to  satellite  failures.    If  the GPS receiver is unable to provide a RAIM solution due to   satellite   tracking   problems  or  problems  with  the satellite constellation geometry, a NO RAIM annunciation   is   shown   to   inform   the   crew   of   the absence   of   RAIM   protection.      During   a   NO   RAIM period, the GPS navigation solution may be acceptable,  but  the  integrity  of  that  solution  will  be indeterminate.  During normal GPS navigation with an active  RAIM  solution,  if  the  GPS  receiver  determines that  there  is  an  inconsistency  in  the  GPS  navigation solution,  a  RAIM  alert  will  be  provided  to  inform  the crew  of  a  degraded  GPS  navigation  solution.    When an   alert   is   indicated,   the   crew   should   compare   the GPS-based   navigation   solution   with   other   available sensors  (INU,  TACAN,  and  VOR/DME)  to  ensure  the GPS navigational accuracy is acceptable. If unacceptable,   select   a   non-GPS   based   navigation solution on the lateral steer page, Figure 3C-118, until the integrity of the GPS navigation solution is restored. The  current  state  of  the  GPS  RAIM  solution  is provided on the Primary GPS INAV page as follows: 1.   NO    RAIM    when    RAIM    processing    is unavailable. 2.   RAIM    ACT    when    RAIM    processing    is actively performing integrity checks. 3.   RAIM  WRN  when  RAIM  has  detected  an inconsistency. The    line    select    key    next    to    RAIM    on    the RAIM/prediction  page  will  enable  or  disable  the  RAIM annunciations.          When     OFF     is     selected,     RAIM annunciations   are   inhibited   and   the   pilot   advisories regarding    GPS    integrity    performance    will    be    only available on the GPS INAV page.  RAIM annunciations should only be disabled if a failure is suspected in the GPS receiver causing nuisance annunciations.   Annunciations will be automatically re-enabled whenever   the   FMS   is   powered   on   or   enters   the terminal area. To request the availability of approach RAIM at a destination airport, enter the identifier of the airport in the  top  line  of  the  RAIM/Prediction   page.    Enter  the ETA     in     UTC.          After     performing     the     predicted calculation, the FMS-800 will display the availability of approach  RAIM  on  the  page  information  line.    This availability applies to a period from 15 minutes prior to the  entered  ETA  until  15  minutes  after  the  ETA.    A predictive RAIM solution only provides an indication of the  availability  of  RAIM  protection  that  is  expected  at the destination based on the current orbital characteristics  of  the  GPS  constellation.    It  does  not provide an actual integrity determination at the desired location. (d)   Selective Availability/Antispoofing Control  Page.      The   FMS-800  provides  access  to  a GPS  Selective  Availability/Antispoofing  control  page.   From   the   IDX   page,   select   SA/AS   to   access   the SA/AS control.  From this  page, the current status of GPS  receiver  keying  is  displayed,  with  two  selections for mission duration and SA/AS mode selection.  GPS