TM 1-1510-223-10 (11) ILS  approach  mode.    The  ILS  approach mode    provides    for    automatic    intercept,    capture,    and tracking   of   the   front   course   localizer   and   glideslope signals. This allows flying a fully coupled ILS approach Set-up for the ILS approach mode is as follows: 1. VHF navigation receiver control panel - Set desired localizer frequency. 2. V/L pushbutton selector switch (display controller) - Depress to select LOC1 or LOC2 3. Course pointer (EHSI) - Set inbound course on heading dial. 4. Heading marker (ESI) - Set desired intercept heading for course interception. The  ESI  will  now  display  the  relative  position  of  the aircraft to the center of the localizer beam and the desired inbound    course.        With    the    heading    marker    set    for intercept,   the   heading   select   mode   can   be   used   to perform the intercept Outside the normal capture range of the  localizer  signal  (between  one  and  two  dots  on  the EHSI),   depressing   the   APR   pushbutton   switch   on   the flight   director   mode   selector   will   cause   the   EADI   to annunciate LOC in white and HDG  in green.  The aircraft will  now  be  flying  the  desired  heading  intercept  and  the system    will    be    armed    for    automatic    localizer    beam capture. With   the   aircraft   approaching   the   selected   course interception, the lateral beam sensor (LBS) is monitoring localizer  beam  deviation,  beam  rate,  and  true  airspeed. At  the  computed  time,  the  LBS  will  trip  and  capture  the localizer  signal  The  flight  control  computer  will  drop  the heading    select    mode    and    generate    the    proper    roll command  to  bank  the  aircraft  toward  the  localizer  beam center.  When the LBS trips, the EADI will display LOC in green.  LOC will be enclosed in a white box for 5 seconds. The glideslope portion of the approach mode is used for  the  automatic  intercept,  capture,  and  tracking  of  the glideslope beam.  The beam is used to guide the aircraft down to the runway in a linear descent Typical glideslope beam  angles  vary  between  2  and  3  degrees,  depending on  terrain.    When  the  glideslope  mode  is  used  as  the vertical portion of the approach, it allows the pilot to fly a fully  coupled  ILS  approach  The  mode  is  interlocked,  so that  glideslope  capture  is  inhibited  until  localizer  capture has occurred. As  the  aircraft  approaches  the  glideslope  beam,  the vertical   beam   sensor   monitors   true   airspeed,   vertical speed,  and  glideslope  deviation  to  determine  the  correct capture  point  At  glideslope  capture,  the  computer  drops any other vertical mode that was in use, and automatically generates    a    pitch    command    to    smoothly    track    the glideslope  beam  Gain  programming  is  performed  on  the glideslope signal to compensate for the aircraft closing on the glideslope transmitter and beam convergence caused by   the   directional   properties   of   the   glideslope   antenna Glideslope  programming  is  normally  accomplished  as  a function of radio altitude and vertical speed.  If the radio altimeter   is   riot   valid,   glideslope   gain   programming   is accomplished  as  a  function  of  preset  height-  above-the- runway   estimates   and   run-down   as   a   function   of   true airspeed. The ILS approach mode is cancelled by: Depressing  NAV  or  APR  pushbutton  switch-indicator on the flight director mode selector Selecting   a   VOR   frequency   on   the   selected   VHF navigation receiver control panel Selecting go-around mode. Selecting standby mode Selecting back course mode Coupling   flight   control   computer   to   the   cross-side EFIS Selecting an alternate ATT, HDG, or NAV source  on the display controller When     the     aircraft     satisfies     the     localizer     track conditions,  the  course  error  signal  is  removed  from  the lateral  steering  command.    This  leaves  radio  deviation, roll attitude, and lateral acceleration to track the localizer signal,  and  to  compensate  for  localizer  beam  standoff  in the presence of a crosswind The system will automatically compensate  for  a  crosswind  of  up  to  45  degrees  course error. (12) Pitch    attitude    hold    mode.       The    pitch attitude   hold   mode   is   the   basic   vertical   flight   director mode.    It  is  activated  when  a  flight  director  lateral  (roll) mode is selected without an accompanying vertical (pitch) mode.      There   is   no   annunciation   for   pitch   hold   mode although   the   basic   AP   ENG   annunciation   is   available. The pitch command on the EADI provides the pilot with a pitch reference corresponding to the pitch attitude existing at the moment the lateral mode was selected.  This pitch reference can be changed with the touch control steering (TCS)    switch    located    on    the    control    wheels.        The reference pitch attitude can also be changed as a function of  the  pitch  wheel  on  the  autopilot  controller  when  the autopilot  is  engaged.    Pitch  attitude  hold  mode  may  be cancelled by selecting any vertical mode or the automatic capture of a vertical mode. (13) Vertical  speed  hold  mode.    The  vertical speed  hold  mode  is  used  to  automatically  maintain  the aircraft at a selected vertical speed reference.  To initiate the mode, the aircraft is maneuvered to the desired climb or    descent    attitude    to    establish    the    vertical    speed reference,  then  the  mode  is  engaged  by  depressing  the VS pushbutton switch-indicator on the flight director mode selector.  The reference vertical speed can be changed by pushing the 3-54