TM 1-1510-218-10 2-69 d.  Rudder  Trim  Tab  Control.   The  rudder  trim tab  control  knob,  placarded   RUDDER  TAB  /  LEFT  / RIGHT,    is    on    the    control    pedestal,    and    controls adjustment of the rudder trim tab, Figures 2-7 and 2-9.   The amount of rudder tab deflection, in degrees from a neutral setting, is indicated by a position arrow. 2-49.  WING FLAPS. The all-metal slot-type  wing  flaps  are  electrically operated  and  consist  of  two  sections  for  each  wing.   These  sections  extend  from  the  inboard  end  of  each aileron   to   the   junction   of   the   wing   and   fuselage.   During  extension,  or  retraction,  the  flaps  are  operated as  a  single  unit,  each  section  being  actuated  by  a separate jackscrew actuator.  The actuators are driven through  flexible  shafts  by  a  single,  reversible electric motor.    Wing  flap  movement,  either  up  or  down,  is indicated    in    percent    of    travel    by    a    flap    position indicator   on   the   subpanel.      Full   flap   extension   and retraction time is approximately 11 seconds.  The flap control  switch  is  located  on  the  control  pedestal.    No emergency   wing   flap   actuation   system   is   provided.   With    flaps    extended    beyond    APPROACH    position regardless of power setting, the landing gear warning horn  will  sound,  and  the  landing  gear  switch  handle lights  will  illuminate  unless  the   landing  gear  is  down and  locked.    The  circuit  is  protected  by  a  20-ampere circuit breaker, placarded   FLAP  MOTOR,  located  on the overhead circuit breaker panel, Figure 2-16. a.   Wing Flap Control Switch.  Flap operation is controlled by a three-position switch with a flap-shaped handle  on  the  control  pedestal,  Figure  2-7   and   2-9.   The   handle   of   this   switch   is   placarded   FLAP  and switch positions are placarded FLAP UP / APPROACH  /   DOWN.      The   amount   of   downward extension of the flaps is established by position of the flap switch, and is as follows: UP – 0%, APPROACH – 40%, and  DOWN – 100%.  Limit switches, mounted on the   right   inboard   flap,   control   flap   travel.      The  flap control    switch,    limit    switch,    and    relay    circuits    are protected   by   a  5 -ampere   circuit   breaker,   placarded FLAP CONTR, located on the overhead circuit breaker panel,  Figure 2-16.    Flap  positions  between   UP  and APPROACH   cannot   be   selected.      For  intermediate flap positions between   APPROACH and   DOWN, the APPROACH position acts as an off position.  To return the   flaps   to   any   position   between   full   DOWN   and APPROACH  place  the  flap  switch  to  UP  and  when desired  flap  position  is  obtained,  return  the  switch  to APPROACH    detent.       In    the    event    that    any    two adjacent  flap  sections  extend  3°  to  5°  out  of  phase with   the   other,   a   safety   mechanism   is   provided   to discontinue power to the flap motor. b.  Wing Flap Position Indicator.  Flap position in percent of travel from "0" (UP ) to 100% (DOWN), is shown  on  an  indicator,  placarded   FLAPS,  below  the instrument panel, Figure 2-17.   The  APPROACH and full  DOWN  or  extended  flap  position  is  14°  and  34°, respectively.  The flap position indicator is protected by a 5-ampere circuit breaker, placarded  FLAP  CONTR, located     on     the     overhead     circuit     breaker     panel. Section VI.  PROPELLERS 2-50.  DESCRIPTION. A three-bladed aluminum propeller is installed on each  engine.    The  propeller  is  of  the  full  feathering, constant    speed,    counter-weighted,    reversing    type, controlled by engine oil pressure through single action, engine  driven  propeller  governors.    The  propeller  is flange    mounted    to    the    engine    shaft.        Centrifugal counterweights, assisted by a feathering spring, move the  blades  toward  the  low  RPM  (high  pitch)  position and   into   the   feathered   position.      Governor   boosted engine  oil  pressure  moves  the  propeller  to    the  high RPM  (low  pitch)  hydraulic  stop  and  reverse  position.   The  propellers  have  no  low  RPM  (high  pitch)  stops; this     allows     the     blades     to     feather     after     engine shutdown.    Low  pitch  propeller  position  is  determined by the low pitch stop which is a mechanically actuated, hydraulic  stop.    Beta  and  reverse  blade  angles  are controlled by the power levers in the beta and reverse range. 2-51.  FEATHERING PROVISIONS. The  aircraft  are  equipped  with  both  manual  and automatic  propeller  feathering.    Manual  feathering  is accomplished  by  pulling  the  corresponding  propeller lever   aft   past   a   friction   detent.      To   unfeather,   the propeller  lever  is  pushed  forward  into  the  governing range.  An automatic feathering system will sense loss of  torque  oil  pressure  and  will  feather  an  unpowered propeller.  Feathering springs will feather the propeller when it is not turning. a.   Automatic     Feathering.          The automatic feathering  system  provides  a  means  of  immediately dumping   oil   from   the   propeller   servo   to   enable   the feathering spring and counterweights to start feathering   action   of   the   blades   in   the   event   of   an engine   failure.    Although  the  system  is  armed  by  a switch    on    the    overhead    control    panel,    placarded AUTOFEATHER  ARM  /  OFF  /  TEST, the completion of  the  arming  phase  occurs  when  both  power  levers are   advanced   above   90%  N₁   –  at  which  time  both indicator   lights   on   the   caution/advisory   annunciator