TM 1-1510-225-10 3B-91 Table 3B-40.  VNAV Capture and Termination Alerts NO. DESCRIPTION/FUNCTION 1 TOP     OF     DESCENT     label     flashes     10 seconds  prior  to  VNAV  capture  (same  for BOC). 2 Altitude  flashes  at  1000  feet  above/below waypoint crossing altitude. 3 V   attribute   flashes   10   seconds   prior   to VNAV capture and at 1000 feet above/below waypoint crossing altitude. i.    Flight Instrument and Autopilot/Flight Director Guidance. (1)   Flight Instrument Displays.  The FMS-800 provides    lateral    and    vertical    navigational    situation information  to  the  pilot’s  flight  displays.    The  pilot’s displays   are   driven   using   the   navigational   solutions from the CDU Pilot Steering page, Paragraph 3B-19.e.(6)(a). (2)   Horizontal   Situation   Displays   (HSI).      In order   to   display   horizontal   situational   data   on   the EHSI, the FMS source must be selected by the pilot.   The EHSI data includes the HSI course arrow (desired track), TO /  FROM pointer, and bearing pointer to the FMS-800 outputs.  These outputs always relate to the flight plan active waypoint or pattern turn point.  Refer to Figure 3B-55 and Table 3B -41.  If the EHSI distance interface     is     compatible     and     aircraft     switching     is installed,   the   distance   readout   will   also   show   great circle distance to the active waypoint. Figure 3B-55.  HSI Display Table 3B-41.  HSI Display NO. DESCRIPTION/FUNCTION 1 Course Readout/Label 2 FMS Message Alert 3 FMS Heading Bug 4 Course Deviation Scale 5 Vertical Deviation Scale 6 Vertical Deviation Pointer 7 Lateral Deviation Bar 8 Course Source 9 FMS Flight Modes 10 Selectable Navigation Data 11 Course Pointer 12 Wind Direction (Deg)/Velocity (Knots) 13 Compass Rose 14 Bearing Pointer 15 Compass Benchmark 16 Distance of Bearing Source 17 Bearing Source 18 Distance to Course Source 19 Free Format Line (ARC-210 Freq) 20 Digital HDG Bug Readout 21 Heading Bug 22 Track Indicator 23 Digital Heading Readout 24 DR or RAM Alert 25 FMS OFST 26 Wind Pointer The course/desired track readout and pointer on the EHSI show the great circle desired track at current aircraft  position  along  the  active  leg.    This  may  differ from  the  CRS  display  on  the  CDU  Flight  Plan  page when  the  distance  to  the  waypoint  is  large,  especially at  high  latitudes.    The  CRS  display  on  the  Flight Plan page  always  references  the  inbound  track  measured at the waypoint.  Refer to Figure 3B-56. When the inbound course to the active waypoint is   manually   entered   on   the   Flight   Plan   page,   the course display and course pointer on the HSI show the desired course at the waypoint.