TM 1-1510-225-10 3B-26 3B-17.  STANDBY ATTITUDE REF ERENCE SYSTEM. a.   Description. (1)   T3   ANG.  The standby attitude indicator, located  below  the  TCAS  II  display,   Figure  3B-13,  is powered  by  engine  bleed  air  and  provides  a  visual reference  of  the  aircraft  pitch  and  roll.    The  attitude indicator is comprised of a self-contained gyro to erect the  sphere  providing  the  pitch  and  roll  reference,  an indicating    symbol    representing    the    aircraft,    and    a horizontal    line    behind    the    indicating    symbol    that represents    the    horizon.        The    moveable    indicating symbol    may    be    adjusted    vertically    to    correct    for variations   in   level   flight   attitudes   by   a   small   knob located on the front base of the indicator. (2)   T3  OSA . The standby attitude reference system,  comprised  of  the  attitude  indicator  located  on the  extreme  left  center  of  the  pilot's  instrument  panel and   a   28   Vdc   emergency   power   supply,   provide   a visual   indication   of   the   aircraft   flight   attitude.      The attitude   reference   system   is   designed   to   provide   a standby attitude indicator that is powered by a source independent     of     the     aircraft     electrical     generating system.      The   system   will   provide   reliable   attitude information  for  at  least  30  minutes  after  a  total  failure of the aircraft electrical system. The    power    supply    contains    sealed    lead-acid batteries  with  a  rating  of  5.0  ampere  hours.    During normal operation, the aircraft 28 Vdc system supplies power  to  the  indicator  and  power  supply  batteries.  In the   event   aircraft   electrical   power   fails,   the   power supply will take over the duties of powering the attitude indicator. The   attitude   indicator   is   a   28   Vdc   powered, electrically driven gyro and contains an inverter circuit board  for  converting  the  28  Vdc  input  to  22 Vac 400 Hz  for  indicator  operation.    The  power  warning  flag  is rotated out of sight by a flag motor that allows the flag to    display    if    one    or    more    phases    of    power    are interrupted.    The  flag  motor  also  allows  the  flag  to display  if  the  PULL  TO  CAGE  knob  is  in  the  caged position.  The rotor speed and the mechanical erection system enable the indicator to provide a minimum of 9 minutes  of  useful  attitude  information  after  complete electrical power interruption. b.  Controls and Indexes.  (1)   Standby     Attitude     Reference     Indicator Controls  and  Indexes    T3   ANG  .      Refer   to   Figure 3B-13. (a)  Attitude  Sphere.    Contains  gyro  and reference lines for pitch and roll degrees. (b)  Roll  Index.    Rotates  with  aircraft  to provide  measurement  of  angular  displacement  by  the roll pointer. (c)  Roll Pointer.  Indicates vertical in any roll attitude. (d)  Horizon Line.  Indicates earth horizon relative to aircraft pitch attitude. (e)  Pitch   Knob.      Rotated   to   adjust   the miniature aircraft. (f)   Pitch Scale. Measures pitch displacement of miniature aircraft. (g)  Miniature Aircraft. Represents aircraft   nose   and   wings.      Indicates   pitch   and   roll attitude   relative   to   the   horizon.      Adjustable   through pitch knob for varying pitch attitudes. 1.  Attitude Sphere 2.  Roll Index 3.  Roll Pointer 4.  Horizon Line 5.  Pitch Knob 6.  Pitch Scale 7.  Symbolic Miniature Aircraft Figure 3B-13.  Standby Attitude Reference Indicator  T3 ANG