TM 1-1510-225-10 3C-8 impact   switch   case,   when   illuminated,   indicates   the switch has been actuated.  Pressing the reset button located adjacent to the impact switch light causes the light to extinguish and restores power to the recorder. b.    The  recorder  system  is  powered  through  a 1-ampere 115 Vac circuit breaker, placarded RECORDER POWER  –  FLT,  located  on  the  copilot's sidewall circuit breaker panel. c.    A    battery    powered,    acoustic    underwater locator beacon assembly is mounted on the front panel of the crash data recorder.  The unit consists of a self- contained     battery,     an     electronic     module     and     a transducer.      The   battery   is   shock   mounted   and   is separated from electronic module by a bulkhead in the case.  The beacon (pinger) radiates a pulsed acoustic signal into the surrounding water upon activation of its water-sensitive  switch  and  will  activate  automatically on submersion in salt or fresh water with an operating life expectancy of 30 days to a depth of 20,000 feet. Section III.  NAVIGATION 3C-13.  ATTITUDE    AND    HEADING    REFERENCE SYSTEM. a.    Vertical   Gyro   System.      The    pilot's    and copilot's  vertical  gyro  systems  are  independent  and powered   by   the   ac   power   bus   located   in   the   nose avionics  compartment.    The  purpose  of  the  vertical gyro    systems    is    to    provide    the    pilots    with    visual indications   of   aircraft   pitch   and   roll   attitudes  on  the flight   director   indicators.      The   gyroscope   develops through synchros, pitch, and roll signals representative of the aircraft attitude. Vertical reference is established    by    two    gravity    sensitive    switches    that control a torque motor for each gyro axis.  High or low erection  rate  of  the  gyro  is  accomplished  by  applying high  or  low  voltage  to  the  respective  torque  motor.   Panel mounted switches, placarded   NO.  1 (pilot) and NO.  2 (copilot)  V  GYRO  FAST  ERECT,  provide  the means  for  fast  erection  of   the  gyros.    Pressing  the FAST  ERECT  switch  will  erect  the  gyro  to  within  1.0° of     pitch     and     roll     within     60     seconds     of     power application, and erect to within 0.5° within 2 minutes. b.    Gyro   Magnetic   Compass   System.      Two identical compass systems provide accurate directional information for the aircraft at all latitudes of the   earth.      For   heading   reference,   two   modes   of operation  are  used:  directional  gyro  (FREE)  mode,  or slaved (SLAVE) mode. (1)  In  areas  where  magnetic  references  are reliable,  the  system  is  operated   in  the  SLAVE  mode.   In   this   mode,   the   directional   gyro   is   slaved   to   the magnetic  flux  valve  that  supplies  magnetic  reference for   correction   of   the   apparent   drift   of   the   gyro.      In FREE mode, the system is operated as a free gyro.  In this mode, latitude corrections are manually introduced using the  INCREASE  /  DECREASE switches located outboard  of  each  HSI.    The  SLAVE/FREE  mode  is selected as desired using the  SLAVE / FREE switches also  located  outboard  of  each  HSI.    Both  compass systems  (No.  1  and  No.  2)  are  ac  power  dependent and are powered by the selected inverter. (2)  Gyro     compass     1     provides     heading information for the pilot's HSl and copilot's RMI.  Gyro compass 2 serves the copilot's HSl and the pilot's RMI. c.    Comparator Monitor OSA.  The comparator monitor    is    a    self-contained,    five-channel,    six-light instrumentation     comparator     used     to     monitor     and compare  the  pilot  and  copilot  flight  in  instrumentation systems   for   similar   pitch   and   roll   attitude,   heading, localizer    signal,    and    glideslope    signal.        A    pre- determined difference between the systems is indicated  by  illumination  of  the  applicable  annunciator (ROLL,  PITCH,  HDG  GS, or   LOC).    The  comparator has  a  self-monitoring  feature  that  checks  the  internal electronics of the comparator and displays any internal failure  on  an  individual  (MNTR)  annunciator.    All  six annunciators   are   located   above   the   pilot's   altimeter and are tested along with the other aircraft annunciator lights by pressing the  PUSH-TO-TEST switch located on   the   warning   annunciators   panel.      An   illuminated comparator    annunciator    may    be    extinguished    by pressing  the  light  face  or,  should  a  fault  correct  itself, the light will extinguish automatically. (1)  Attitude  Monitor  (ROLL,   PITCH).    Two separate channels of roll and pitch attitude monitoring are   provided.    Each  attitude  channel  receives  input signals  from  a  differential  resolver  synchro  located  in the attitude director indicator.  An angular difference of 6 in roll or pitch will result in a fault indication. (2)  Compass  Monitor  (HDG).    The  compass monitor  receives  input  from  synchros  in  the  HSI's.    A nominal heading difference in unbanked flight of 6° will result in a fault indication. (3)  Localizer  Deviation  (LOC).  The localizer deviation   signals   are   received   from   both   VHF   NAV receivers.    The  nominal  fault  indication  difference  is approximately 1/2 dot. (4)  Glideslope (GS). The glideslope deviation   signals   are   received   from   both   glideslope