TM  55-1510-221-10 tor  trim  should  occur  only  by  movement  of  pairs  of switches.   The   trim   system   disconnect   is   a   bi-level, pushbutton,   momentary   type   switch,   located   on   the outboard  grip  of  each  control  wheel.  Depressing  the switch   to   the   first   of   two   levels   disconnects   the autopilot   and   yaw   damp   system,   and   the   second level  disconnects  the  electric  trim  system.  The  sys- tem  can  be  reset  by  moving  the  ELEV  TRIM  switch toggle on the pedestal (fig. 2-7) to OFF RESET posi- tion,  then  back  to  ELEV  TRIM  (on)  again. c. Aileron  Trim  Tab  Control.  The  aileron  trim tab  control,  placarded  AILERON  TAB  -  LEFT, RIGHT,   is   on   the   control   pedestal   and   will   adjust the  left  aileron  trim  tab  only  (fig.  2-7).  The  amount of  aileron  tab  deflection,  from  a  neutral  setting,  as indicted  by  a  position  arrow,  is  relative  only  and  is not  in  degrees.  Full  travel  of  the  tab  control  moves the  trim  tab  7-1/2  degrees  up  and  down. 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  (fig.  2-7).  The amount  of  rudder  tab  deflection,  in  degrees  from  a neutral  setting,  is  indicated  by  a  position  arrow. 2-41.  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  oper- ated  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  is  indicated  in percent  of  travel  by  a  flap  position  indicator  on  the forward  control  pedestal.  Full  flap  extension  and retraction   time   is flap  control  switch approximately  11  seconds.  The is  located  on  the  control  pedestal. b. Wing Flap Position Indicator. Flap position in  percent  of  travel  from  “0“  percent  (UP)  to  100 percent   (DOWN),   is   shown   on   an   indicator,   plac- arded   FLAPS   located   on   the   control   pedestal   (fig. 2-7).  The  approach  and  full  down  or  extended  flap position  is  14  and  34  degrees,  respectively.  The  flap position  indicator  is  protected  by  a  5-ampere  circuit breaker,  placarded  FLAP  CONTR,  located  on  the overhead  circuit  breaker  panel  (fig.  2-26). Section VI. PROPELLERS 2-42. DESCRIPTION. A  three-blade  aluminum  propeller  is  installed  on each  engine.  The  propeller  is  of  the  full  feathering, constant   speed,   counterweighted,   reversible   type, controlled   by   engine   oil   pressure   through   single action,   engine   driven   propeller   governors.   The   pro- peller  is  flange-mounted  to  the  engine  shaft.  Centrif- ugal  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 No  emergency  wing  flap  actuation  system  is  pro- vided.  With  flaps  extended  beyond  the  APPROACH position,  the  landing  gear  warning  horn  will  sound, unless  the  landing  gear  is  down  and  locked.  The  cir- cuit  is  protected  by  a  20-ampere  circuit  breaker, placarded  FLAP  MOTOR,  located  on  the  overhead circuit  breaker  panel  (fig.  2-26). a. Wing  Flap  Control  Switch.  Flap   operation is  controlled  by  a  three-position  switch  with  a  flap- shaped  handle  on  the  control  pedestal  (fig.  2-7).  The handle  of  this  switch  is  placarded  FLAP  and  switch positions  are  placarded:  FLAP  -  UP,  APPROACH, and  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  con- trol  switch,  limit  switch,  and  relay  circuits  are  pro- tected  by  a  5-ampere  circuit  breaker,  placarded FLAP   CONTR   located   on   the   overhead   circuit breaker  panel  (fig.  2-26).  Flap  positions  between  UP and  APPROACH  cannot  be  selected.  For  intermedi- ate   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  the  APPROACH  detent.  In  the event  that  any  two  adjacent  flap  sections  extend  3  to 5  degrees  out  of  phase  with  the  other,  a  safety  mech- anism  is  provided  to  discontinue  power  to  the  flap motor. 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  mechan- ically   actuated,   hydraulic   stop.   Beta   and   reverse blade  angles  are  controlled  by  the  power  levers  in the  beta  and  reverse  range. 2-38