TM 1-1510-218-10 3B-35 Chanute, Kansas (CNU).  It is necessary in this case to add the "K" prefix to make the letter KCNU. (2)   Navaid   ICAO   Identifiers.      Most   navaid identifiers are made up of three letters, but combinations of two or three letters and number also exist. (3)   Waypoint ICAO Identifiers. Most waypoint identifiers (high altitude, low altitude, multiple,  and  approach  intersections)  consist  of  five letters,  however,  some  waypoint  identifiers  consist  of combinations of three to five letters and numbers such as GOONI, D3N, and L121. (4)   Runway  Thresholds  and  Outer  Markers.   Runway  thresholds  and  outer  markers  are  not  stored in  the  data  base  by  ICAO  identifiers.   Access is from the appropriate airport waypoint page. (5)   On-airway  NDB  ICAO  Identifiers.    NDB's that are located on an airway are contained in the data base whenever any type of waypoint (high altitude, low altitude, DP/STAR, or approach intersection) has been loaded   into   the   data   base.      On   airway   NDB's   are accessed by the two or three character identifier plus an NB suffix, such as GNINB. h.    Dedicated Special Function Keys.    Dedicated   special   function   keys   are   physically   and visually  separated  from  the  alpha/numeric  keys  used in   the   generation   and   storage   of   flight   plans   and waypoints. i. FMS     Interface     with     the     MFD     Radar Graphics   Unit.     The  FMS  interfaces  with  the  MFD radar    graphics    unit,    providing    a    radar    graphics presentation    on    the    weather    radar    display.        This includes  such  items  as  flight  plan  waypoints,  selected course, and reference ground stations. j. Bulk   Loading   and   Saving   Using   Data Loader.    In  addition  to  updating  the  data  base,  the data loader may be used to load and save flight plans, waypoints,  and  the  user  generated  supplemental  data base. k.    FMS   Control-Display   Unit   Controls   and Functions.  (1)   Message    Key    and    Annunicator.        An alternate-action   key   placarded   MSG,   when   pressed causes the message page to be displayed.  Pressing the key once selects the message page,  pressing the key again deselects the message page.  The message annunciator    is    located    above    the    message    key.   Illumination   of   the   message   light   indicates   that   a message    will    be    displayed    on    the    FMS    control- displayed unit when the message key is pressed.   The message   key   is   used   to   acknowledge   a   message annunciator.        The    message    annunciator    will    be extinguished    only    after    the    message    has    been satisfactorily acknowledged. (2)   Cursor    Keys.        Two    cursor    keys    are provided,   -   and   ¯ ,  to  position  the  cursor  (a  bright inverse  video  rectangle)  over  information  in  a  line  or portion of a line on the control display unit, in order to approve or change that information.  If the cursor is out of view it can be brought onto the screen at the top or bottom by using the up or down cursor key. (3)   Mode  Key.    This key, placarded   MODE, allows selection of NAV, RNV ENR (RNAV en route), or  RNV  APR  (RNAV  approach)  modes  of  operation.   When  NAV  is  selected,  normal  angular  HSI  deviation bar  sensitivity  occurs  (+  10°  full  scale).    When  RNV ENR s selected the deviation bar indicates + 5 nautical mile  full  scale  and  when  in  RNV  APR  the  deviation indicates ± 1.25 nautical mile full scale.  When an ILS frequency  is  selected  the  sensor  annunciated  is  ILS.   OBS will be displayed as the method of operation and ILS   will   be   displayed   and   the   mode   of   operation.   When the OMEGA or BLEND sensor is selected, RNV ENR  is  automatically  selected  as  the  only  mode  of operation. (4)   Sensor Key.   The sensor key, placarded SNS,    selects    the    active    sensor    to    be    used    for navigation.      Alternate   key   strokes   will   select   VOR, OMEGA,  TACAN,  GPS,  or  BLEND.    When  the  VOR sensor is selected, navigation is based upon available VOR/DME signals.  When an ILS frequency has been selected as the active waypoint the sensor annunciation indicates ILS.  When the OMEGA sensor is selected, navigation is based upon available omega and VLF signals.  When the GPS sensor is selected, the NAVSTAR satellite global positioning system GPS) is used for navigation information.  When the BLEND sensor is selected, navigation is based on a computer blend of position inputs from all active sensors. (5)   OBS/LEG    Key.        The    OBS/LEG     key selects  method  of  operation.    Each  key  push  selects the next method of operation in the sequence of OBS, AUTO/LEG, then back to OBS. (6)   Frequency    Key.        The    frequency    key, placarded FREQ, selects the two frequency pages that allow frequency management of the VHF transceivers, NAV/TACAN, NAV 2, and the ADF receivers. (7)   Brightness Control Switch. The brightness  control  switch,  placarded   BRT   DIM,  is  a rocker  type  switch  which,  when  pressed  at  the  top, increases   the   picture   brightness   and   message   light