TM 55-1510-220-10 Section XI.  FLIGHT INSTRUMENTS 2-78.  PITOT AND STATIC SYSTEM. a Description. The  pitot and static system (fig.  2- 20)  supplies  static  pressure  to  two  airspeed  indicators, two altimeters, two vertical velocity indicators, and ram air  to  the  airspeed  indicators.    This  system  consists  of two  pitot  masts  (one  located  on  each  side  of  the  lower portion   of   the   nose),   static   air   pressure   ports   in   the aircraft's  exterior  skin  on  each  side  of  the  aft  fuselage, and   associated   system   plumbing.      The   pitot   mast   is protected from ice formation by internal electric heating elements. b. Alternate  Static  Air  Source.    An  alternate  static air  line,  which  terminates  just  aft  of  the  rear  pressure bulkhead,  provides  a  source  of  static  air  for  the  pilot's instruments in the event of source failure from the pilot's static    air    line.        A    control    on    the    pilot's    subpanel placarded   PILOTS   STATIC   AIR   SOURCE,   may   be actuated to select either the NORMAL, or ALTERNATE air source by a two position selector valve.  The valve is secured   in   the   NORMAL,   position   by   a   spring   clip. Refer  to  Chapter  7  for  airspeed  indicator  and  altimeter calibration   information   when   using   the   alternate   air source. 2-79.  TURN-AND-SLIP INDICATORS. Turn-and-slip   indicators   are   installed   separately on  the  pilot  and  copilot  sides  of  the  instrument  panel (fig.  2-:30).  The pilot's indicator provides yaw damping information    to    the    autopilot.        These    indicators    are gyroscopically  operated.    They  use  DC  power  and  are protected by :,-ampere circuit breakers placarded TURN &  SLIP  PILOT  OR  COPILOT  on  the  overhead  circuit breaker panel (fig.  2-27). 2-80.  AIRSPEED INDICATORS. Airspeed indicators are installed separately on the pilot  and  copilot  sides  of  the  instrument  panel  (fig.    2- 30).      these   indicators   require   no   electrical   power   for operation.    The  indicator  dials  are  calibrated  in  knots from 40 to 300.  A striped pointer automatically displays the maximum allowable airspeed (247 KIAS, 0.47 Mach) at the aircraft's present altitude. 2-81.  PILOT'S ENCODING ALTIMETER. The  altimeter  is  located  on  the  upper  left  side  of the  instrument  panel  (fig.    2-30).    The  altimeter>  is  a self-contained     unit     which     consists     of     a     precision pressure  altimeter  combined  with  an  altitude  encoder. The    display    indicates    and    the    encoder    transmits, simultaneously,    pressure    altitude    information    to    the transponder.  Altitude is displayed on the altimeter by a 10,000  foot  counter,  a  1000  foot  counter,  and  a  single needle  pointer  which  indicates  hundreds  of  feet  on  a circular  scale  in  50  foot  increments.    Below  an  altitude of 10,000 feet, a diagonal warning symbol will appear on the  10,000  foot  counter.    A  barometic  pressure  setting knob is provided to insert the desired altimeter setting in inches Hg or millibars.  A DC powered vibrator operates inside the altimeter whenever aircraft power is on.  If l)C power   to   the   altitude   encoder   is   lost,   a   warning   flag placarded  COI)E  OFF  will  appear  in  the  upper  center portion of the instrument face, indicating that the altitude encoder   is   inoperative   and   that   the   system   is   not reporting     altitude     to     ground     stations.          Operating instructions are contained in Chapter 3. 2.82.  COPILOT'S ALTIMETER. The   copilot's   altimeter   is   located   on   the   upper right   side   of   the   instrument   panel   (fig.      2-30).      It   is similar  to  the  pilot's  altimeter  except  it  lacks  altitude reporting capability. 2-83.  VERTICAL VELOCITY INDICATORS. Vertical velocity indicators are installed separately on  the  pilot  and  copilot  sides  of  the  instrument  panel (fig.      2-30).      They   indicate   the   speed   at,   which   the aircraft   ascends   or   descends   based   on   changes   in atmospheric pressure.  'The indicator is a direct reading pressure   instrument   requiring   no   electrical   power   for operation. 2-84.  ACCELEROMETER. The   accelerometer,   located   on   the   instrument panel   registers   and   records   positive   and   negative   G loads imposed on the aircraft.  One hand moves in the direction of the G load being applied while the other two, one for positive G loads and one for negative G loads, follow the indicating pointer Change 2    2-72