TM 1-1510-225-10 3A-19 (k)   Vertical Speed Indicator Needle.   Moves  around  vertical  speed  scale  to  indicate  vertical speed. (l)    Preset Vertical Speed Selection Indicator.  Indicates selected vertical speed. (m) Inches of Mercury/Millibar Annunciator.  Indicates units of pressure measurement for altimeter setting in HG or MB. (n)   Altimeter   Setting   Display.    Displays altimeter setting in millibars or inches of mercury. (o)   Altimeter Invalid (ALT or FAIL) Annunciator.          The     altimeter     invalid     annunciator illuminates  ALT  or  FAIL  to  ndicate  invalid  altimeter information. e.   Autopilot  Servo  Actuators  (KSA  470).    To manipulate  trim  surfaces,  as  well  as  elevator,  aileron, and   rudder   controls,   the   autopilot   employs   servo actuators   installed   in   the   aircraft's   fuselage.      Each servo     assembly     includes     a     drive     motor,     clutch mechanism, and mounting bracket. f.    Autopilot    Controller    (KMC    440).        The autopilot controller provides selection of autopilot, yaw damper, half bank, and soft ride functions.  In addition the  autopilot  also  includes  roll,  pitch,  and  yaw  axis annunciators    that    illuminate    to    indicate    failure    of individual    control    axes,    and    roll    and    vertical    trim controls.        To    engage    autopilot    modes    press    the corresponding  control  key.    To  disengage,  press  the key a second time. NOTE The   autopilot   cannot   be   activated   if   the flight director is not operating properly. Annunciator lamps illuminate above the selector keys  and  on  the  EADI  to  indicate  autopilot  mode  of operation.  In the event of system failure, annunciators corresponding  to  the  autopilot  and  yaw  damper  will flash for approximately 5 seconds before extinguishing.          An     alert     tone     will     sound     upon disengagement. (1)   Autopilot  Controller  Controls,  Indicators, and Functions.  Refer to Figure 3A-8. (a)   Autopilot    Engage/Disengage    Push- Button    Selector    Switch.        Pressing    the    autopilot engage/disengage push-button selector switch, placarded  AP,  initiates  autopilot  control  of  the  pitch, roll,    and    yaw    axes,    provided    the    system    meets preflight   test   criteria.      The   yaw   damper   and   flight director, if not previously engaged, engage automatically upon autopilot activation.  In the absence of any selected flight director modes, the autopilot will follow   basic   roll   and   pitch   attitude   hold   commands synchronized    to    the    aircraft    attitude    current    upon activation.    Pressing  the   autopilot  key  a  second  time cancels   its   operation.      The   flight   director   and   yaw damper  will  remain  engaged  until  they  are  canceled individually. (b)   Autopilot Engaged Annunciator.   Illumination of the autopilot annunciator, placarded  AP, indicates that the aut opilot is engaged. (c)   Half Bank Mode Annunciator.   Illumination    of    the    half    bank    mode    annunciator, placarded  HB,  indicates  that  the  half  bank  mode  has been selected and is engaged. (d)   Half Bank Mode Push-Button Selector  Switch.    Pressing  the  half  bank  mode  push- button     selector     switch,     placarded     HALF     BANK, reduces the autopilot maximum roll attitude command to one half the normal limit.  Roll commands of lesser magnitude  are  not  affected.     HALF   BANK  may  be engaged in conjunction with any flight director tracking mode  with  the  exception  of  approach.    HALF  BANK may be employed at the same time as approach arm, but   will   cancel   automatically   upon   initiation   of   the approach capture sequence. (e)   Autopilot  Left/Right  System  Transfer Indicator.       The    autopilot    left/right    system   transfer indicator consists of a left and right illuminated arrow.   The indicator, located above the autopilot transfer (AP XFER)    switch,    illuminates    to    show    which    side    is controlling the aircraft. (f)    Autopilot  Left/Right  System  Transfer Push-Button  Selector  Switch.    Pressing  the  autopilot left/ right transfer push-button selector switch, placarded AP XFER, changes which EFIS system (left or right) controls the aircraft. (g)   Roll/Roll     Rate     Command     Control Knob.       The   roll/roll   rate   command   control   knob, placarded L and  R, is a rotary, return-to-center control knob.    Turning  the  knob  modifies  the  flight  director's reference   attitude   during   operations   in   roll   attitude hold.  Turning the knob in either direction cancels any selected  flight  director  horizontal  mode  and  engages roll  attitude  hold.    Operating  the  roll  attitude  control does  not  affect  arm  operations  in  nav  or  approach modes, nor does it affect flight director vertical modes, with the exception of glideslope, which it cancels along with approach.