TM 55-1510-220-10 protrudes   out   from   the   wing   and   contains   a   heating element.    The  vent  line  at  the  nacelle  contains  an  inline flame arrestor. j. Engine    Oil-to-Fuel    Heat    Exchanger.        An    K engine oil-to-fuel heat exchanger, located on each engine accessory  case,  operates  continuously  and  automatically to  heat  the  fuel  delivered  to  the  engine  sufficiently  to prevent the freezing of any water which it might contain. The  temperature  of  the  delivered  fuel  is  thermostatically regulated to remain between 21°C and 32°C. 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 (fig. 2-16).  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.  Switches are installed in the outboard grip of each wheel  to  operate  the  elevator  trim  tabs.    A  microphone switch,   a   chaff   dispense   switch,   and   an   autopilot/yaw damp/ electric trim disconnect switch are also installed in the  outboard  grip  of  each  wheel.    A  transponder  ident switch   is   installed   on   top   of   the   inboard   grip   of   each control   wheel.      These   control   wheels   (fig.   2-18)   are installed   on   each   side   of   the   instrument   subpanel.      A manually  wound  8-day  clock  is  installed  in  the  center  of the  pilot's  control  wheel,  and  a  digital  electric  clock  is installed  in  the  center  of  the  copilot's  control  wheel.    A map light switch, and a pitch synchronization and control wheel  steering  switch  are  mounted  adjacent  to  the  clock in each control wheel. 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.    2-7). 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. 2-35