TM 1-1510-223-10 Table 3-3.  Weather Radar Return Levels Return WX GMAP Level 1 Green Cyan Level 2 Yellow Yellow Level 3 Red Magenta Level 4 Magenta -- RCT Blue -- BT03840 g. EHSI Amber Caution or Failure Annunciations (fig. 3-18). (1)   Same  compass  source  or  navigation  source. When both the pilot and copilot select the same compass or   navigation   source,   the   source   annunciators   will   be amber. (2)   Cross-switched   navigation   sources.      If   the pilot  selects  the  copilot's  navigation  source  (VOR2)  or  if the  copilot  selects  the  pilot's  navigation  source  (VOR1), the  annunciator  will  be  amber  to  indicate  cross-switched navigation  sources.    If  both  the  pilot  and  copilot  select TACAN as the navigation source, TCN will be annunciated in amber. (3)   DME  hold.    When   DME   is   set   in   the   hold position,   an   amber   H   is   displayed   to   the   left   of   the numerical DME readout (4)   Waypoint   annunciations.      An   amber   WPT annunciation from the long range navigation system (INS) is displayed to indicate waypoint passage. (5)   Cautions  due  to  failures  of  DME,  GSPD,  or TTG.        When    distance    measuring    equipment    (DME), groundspeed (GSPD), or time-to-go (TG) systems fail, the digital   displays   will   be   replaced   by   amber   dashes.      If NAV1 distance information is not available due to TACAN selection,   an   amber   N/A   will   appear   in   the   distance position. NOTE If   one   pilot   selects   TCN   but   the   other   pilot selects  NAV1  navigation  source,  the  pilot  with the NAV1 data will have an N/A in the distance display.  If TCN is deselected, distance data will return to the NAV1 distance display. (6) Target alerts.   Weather radar target alerts are annunciated  on  the  EHSI.    A  green  TGT  annunciation indicates    an    armed    condition,    while    an    amber    TGT indicates an alert condition. (7)   Course select and heading select.   Failure of course or heading select signals will cause these displays to  be  replaced  by  amber  dashes.    They  are  also  dashed when the heading display is invalid. (8)   Weather radar failure.   Failure of the weather radar  system  is  indicated  on  the  EHSI  by  WX  FAILURE (amber). h. EHSI Red failure annunciations (fig.  3-19). (1)   Heading  failure.    A.    failure  of  the  heading system  results  in  the  removal  of  bearing  annunciators, bearing   pointers,   course   deviation   pointer,   and   course scale.      The   digital   course   readout   and   digital   heading readout   will   be   dashed,   and   a   red   HDG   FAIL   will   be displayed. (2)   Course     deviation     or     glideslope     deviation failure.   Failure of course or glideslope deviation systems will result in the removal of course and glideslope pointers and a red X will be drawn through the scale.  The letter G will appear at the zero deviation position of the glideslope scale to identify the invalid information 3-22. EADI AND EHSI COMPOSITE DISPLAY. If an EADI or EHSI display unit fails, a composite attitude and  navigation  format  (fig.    3-20),  may  be  displayed  on the remaining display.  Selection of the composite mode is made by turning the applicable DIM control to OFF.  As in normal EADI and EHSI presentations, all elements are not displayed at the same time.  The presence or absence of  each  display  element  is  determined  by  flight  phase, navigation   radio   tuning,   selected   flight   director   mode, absolute  altitude,  etc.    The  failure,  caution,  and  warning annunciations   function   is   much   the   same   as   for   the normal display mode. 3-38