TM 1-1510-224-10 b.        Standby    Fuel    Pumps.          A    submerged, electrically-operated   standby   fuel   pump,   located   within each   nacelle   tank,   serves   as   a   backup   unit   for   the engine-driven   boost   pump.      The   standby   pumps   are switched    off    during    normal    system    operations.        A standby   fuel   pump   will   be   operated   during   crossfeed operation   to   pump   fuel   from   one   nacelle   tank   to   the opposite   engine.      The   correct   pump   is   automatically selected   when   the    CROSSFEED   switch   is   activated. Each standby fuel pump has an inertia switch included in the power supply circuit.  When subjected to a   5  to  6  g shock  loading,  as  in  a  crash  situation,  the  inertia  switch will    remove    electrical    power    from    the    standby    fuel pumps.    The  standby  fuel  pumps  are  protected  by  two 10-ampere circuit breakers placarded  STANDBY  PUMP #1 or  #2,  located  on  the  overhead  circuit  breaker  panel (fig.  2-9),  and  four  5-ampere  circuit  breakers  (two  each in parallel) on the hot battery bus. c.  Fuel Transfer Pumps.  The  auxiliary  tank  fuel transfer  system  automatically  transfers  the  fuel  from  the auxiliary   tank   to   the   nacelle   tank   without   pilot   action. Motive  flow  to  a  jet  pump  mounted  in  the  auxiliary  tank sump  is  obtained  from  the  engine  fuel  plumbing  system downstream   from   the   engine   driven   boost   pump   and routed   through   the   transfer   control   motive   flow   valve. The  motive  flow  valve  is  energized  to  the  open  position, by  the  control  system,  to  transfer  auxiliary  fuel  to  the nacelle  tank  to  be  consumed  by  the  engine  during  the initial  portion  of  the  flight.    When  an  engine  is  started, pressure   at   the   engine   driven   boost   pump   closes   a pressure   switch,   which,   after   a   30   to   50   second   time delay  to  avoid  depletion  of  fuel  pressure  during  starting, energizes  the  motive  flow  valve.    When  auxiliary  fuel  is depleted,    a    low    level    float    switch    de-energizes    the motive  flow  valve  after  a  30  to  60  second  time  delay. This  time  delay  function  prevents  cycling  of  the  motive flow  valve  due  to  sloshing  fuel.    If  the  motive  flow  valve or the associated control circuitry fails, the loss of motive flow  pressure  when  there  is  still  fuel  remaining  in  the auxiliary  fuel  tank  is  sensed  by  a  pressure  switch  which illuminates    a    caution    annunciator    placarded    #1    NO FUEL  XFR  or  #2  NO  FUEL  XFR.    During  engine  start, the pilot should note that the NO FUEL XFR annunciator extinguishes  30  to  50  seconds  after  engine  start.    The NO FUEL XFR  annunciator  will  not  illuminate  if  auxiliary tanks are empty.  A manual override is incorporated as a backup   for   the   automatic   transfer   system.      Manual override  is  initiated  by  placing  the   AUX  XFER  switch, located   in   the   fuel   management   panel,   to   the   OVRD position.    This  will  energize  the  transfer  control  motive flow  valve.    The  transfer  systems  are  protected  by  5- ampere circuit breakers, placarded AUXILIARY TRANSFER  #1 or   #2,  located  on  the  overhead  circuit breaker panel (fig. 2-9). NOTE In   turbulence   or   during   maneuvers, the  NO  FUEL  XFR  annunciators  may momentarily illuminate after the auxiliary fuel has completed transfer. d.        Fuel    Gaging    System.        Fuel    quantity    is measured   by   a   capacitance   type   fuel   gaging   system. Two fuel gages, one for the left and one for the right fuel system, read fuel quantity in pounds.  A maximum of 3% error may be encountered in each system; however, the system  is  compensated  for  fuel  density  changes  due  to temperature  excursions.    In  addition  to  the  fuel  gages, amber  #1  NAC  LOW or  #2  NAC  LOW  annunciators  on the  caution/advisory  annunciator  panel  illuminate  when there   is   approximately   30   minutes   (approximately   58 gallons)  of  fuel  per  engine  remaining  (on  standard  day, at sea level, maximum cruise power consumption rate). NOTE The  low  fuel  annunciators  are  level- sensing   volumetric   devices   and   are not    compensated    for    fuel    density, attitude, fuel flow, etc. The   fuel   gaging   system   is   protected   by   individual   5- ampere circuit breakers placarded   QTY  IND and   FUEL QTY, #1 and #2, located on the overhead circuit breaker panel (fig. 2-9).  A mechanical spiral float gage (fig. 2-23) is   installed   in   each   auxiliary   fuel   tank   to   provide   an indication   of   fuel   level   when   servicing   the   tank.      The gage    is    installed    on    the    auxiliary    fuel    tank    cover, adjacent  to  the  filler  neck.    A  small  sight  window  in  the upper wing skin permits observation of the gage. e. Fuel Management Panel. The fuel management  panel  is  located  overhead  in  the  cockpit between the pilot and copilot.  It contains the fuel gages, standby fuel pump switches, crossfeed valve switch, fuel gaging    system    control    switch,    and    transfer    control switches. (1)    Fuel  gaging  system  control  switch.     A switch    on    the    fuel    management    panel    (fig.    2-20) placarded    FUEL    QUANTITY,    MAIN    -    AUXILIARY, controls  the  fuel  gaging  system.    When  the  switch  is  in the  MAIN   position,   the   fuel   gages   read   the   total   fuel quantity  in  the  left  and  right  main  fuel  systems.    When the switch is in the  AUXILIARY  position,  the  fuel  gages read  the  fuel  quantity  in  the  left  and  right  auxiliary  tanks only. (2)        Standby    fuel    pump    switches.        Two switches, placarded  STANDBY PUMP - ON,  located  on the    fuel    management    panel    (fig.    2-20),    individually control a submerged fuel pump located in the corresponding    nacelle    tank.        During    normal    aircraft operation both switches should be   OFF,  so  long  as  the engine-driven fuel pumps are operative. 2-47