TM 55-1510-219-10 2-35.  FUEL SYSTEM MANAGEMENT. a. Fuel Transfer System.    When  the  auxiliary  tanks are   filled,   they   will   be   used   first.      During   transfer   of auxiliary    fuel,    which    is    automatically    controlled,    the nacelle  tanks  are  maintained  full.    A  check  valve  in  the gravity feed line from the outboard wing prevents reverse fuel  flow.    Normal  gravity  transfer  of  the  main  wing  fuel into  the  nacelle  tanks  will  begin  when  auxiliary  fuel  is exhausted.    The  system  will  gravity  feed  fuel  only  to  its respective  nacelle  tank,  i.    e.    left  or  right.    Fuel  will  not gravity feed through the crossfeed system. b. Operation With Failed Engine-Driven Boost Pump or   Standby   Pump.      Two   pumps   in   each   fuel   system provide  inlet  head  pressure  to  the  engine  driven  primary high-pressure  fuel  pump.    If  crossfeed  is  used,  a  third pump,  the  standby  fuel  pump  from  the  opposite  system, will  supply  the  required  pressure.    Operation  under  this condition  will  result  in  an  unbalanced  fuel  load  as  fuel from one system will be supplied to both engines while all fuel  from  the  system  with  the  failed  engine  driven  and standby boost pumps will remain unused.  A triple failure, which is highly unlikely, would result in the engine driven primary   pump   operating   without   inlet   head   pressure. Should   this   situation   occur,   the   affected   engine   can continue to operate from its own fuel supply on its engine- driven primary high-pressure fuel pump. 2-36.  FERRY FUEL SYSTEM. Provisions   are   installed   for   connection   to   long range fuel cells. Section V.  FLIGHT CONTROLS 2-37.  DESCRIPTION. The    aircraft's    primary    flight    control    systems consist    of    conventional    rudder,    elevator    and    aileron control  surfaces.    These  surfaces  are  manually  operated from   the   cockpit   through   mechanical   linkage   using   a control    wheel    for    the    ailerons    and    elevators,    and adjustable  rudder/brake  pedals  for  the  rudder.    Both  the pilot and copilot have flight controls.  Trim control for the rudder,  elevator  and  ailerons  is  accomplished  through  a manually   actuated   cable-drum   system   for   each   set   of control    surfaces.        The    autopilot    has    provisions    for controlling   the   position   of   the   ailerons,   elevators,   and rudder.  Chapter 3 describes the operation of the autopilot system. 2-38.  CONTROL WHEELS. Elevator and aileron control surfaces are operated by manually actuating either the pilot's or copilot's control wheel  (fig.    2-16).    Switches  are  installed  in  the  grips  of each control wheel for operation of pitch trim microphone, autopilot disconnect, transponder identification, and chaff dispenser.    A  manually  wound  8-day  clock  is  installed  in the   center   of   the   pilot's   control   wheel,   and   a   digital clock/timer is installed in the center of the copilot's control wheel.    A  map  light  switch  is  mounted  adjacent  to  each clock.        For    information    on    operation    of    the    digital clock/timer, refer to Section XI. 2-39.  RUDDER SYSTEM. a. Rudder Pedals.    Aircraft  rudder  control  and  nose wheel steering is accomplished by actuation of the rudder pedals  from  either  pilot's  or  copilot's  station  (fig.    2-9). The rudder pedals may be individually adjusted in either a forward  or  aft  position  to  provide  adequate  leg  room  for the   pilot   and   copilot.      Adjustment   is   accomplished   by depressing the lever alongside the rudder pedal arm and moving   the   pedal   forward   or   aft   until   the   locking   pin engages in the selected position. b. Yaw   Damp   System.      A   yaw   damp   system   is provided to aid the pilot in maintaining directional stability and  increase  ride  comfort.    The  system  may  be  used  at any altitude and is required for flight above 17,000 feet.  It must  be  deactivated  for  takeoff  and  landing.    The  yaw damp   system   is   a   part   of   the   autopilot.      Operating instructions  for  this  system  are  contained  in  Chapter  3. The    system    is    controlled    by    a    YAW    DAMP    switch adjacent   to   the   ELEV   TRIM   switch   on   the   pedestal extension. c. Rudder Boost System.  A rudder boost system is provided to aid the pilot in maintaining directional stability resulting  from  an  engine  failure  or  a  large  variation  of power  between  the  engines.    Incorporated  in  the  rudder cable  system  are  two  pneumatic  rudder  boosting  servos that  actuates  the  cables  to  provide  rudder  pressure  to help compensate for asymmetrical thrust. (1) During    operation,    a    differential    pressure valve   accepts   bleed   air   pressure   from   each   engine. When the pressure varies between the bleed air systems, the shuttle in the differential pressure valve moves toward the low pressure side.  As the pressure difference reaches a  preset  tolerance,  a  switch  closes  on  the  low  pressure side   which   activates   the   rudder   boost   system.      This system     is     designed     only     to     help     compensate     for asymmetrical    thrust.        Appropriate    trimming    is    to    be accomplished by the pilot. Moving 2-35