(2.)  Standby  fuel  pump  switches.  T w o switches,  placarded  STANDBY  PUMP  -  ON  located on  the  fuel  management  panel  (fig.  2-14)  control  a submerged   fuel   pump   located   in   the   corresponding nacelle  tank.  During  normal  aircraft  operation  both switches  are  off  so  long  as  the  engine-driven  boost pumps  function  and  during  crossfeed  operation.  The loss  of  fuel  pressure,  due  to  failure  of  an  engine driven   boost   pump   will   illuminate   the   MASTER WARNING  lights  on  the  glareshield  and  will  illumi- nate the No. 1 FUEL PRESS or No. 2 FUEL PRESS on  the  warning  annunciator  panel.  Turning  ON  the STANDBY  PUMP  will  extinguish  the  FUEL  PRESS lights.  The  MASTER  WARNING  lights  must  be manually   cleared. NOTE Both  standby  pump  switches  shall  be  off during   crossfeed   operation. (3.)   Fuel   transfer   control   switches.   Two switches  on  the  fuel  management  panel  (fig.  2-14), placarded   AUX   TRANSFER   OVERRIDE   -   AUTO control  operation  of  the  fuel  transfer  pumps  During normal  operation  both  switches  are  in  AUTO  which allows   the   system   to   be   automatically   actuated   by fuel  flow  to  the  engine.  If  either  transfer  system  fails to   operate,   the   fault   condition   is   indicated   by   two illuminated   MASTER   CAUTION   lights   on   the glareshield  and  a  steadily  illuminated  yellow  No.  1 NO  FUEL  XFR  or  No.  2  NO  FUEL  XFR  light  on the   caution   annunciator   panel. (4.)  Fuel  crossfeed  switch.  The  fuel  cross- feed  valve  is  controlled  by  a  3-position  switch  (fig. 2-14),  located  on  the  fuel  management  panel,  plac- arded   CROSSFEED   -   OFF.   Under   normal   flight conditions   the   switch   is   left   in   the   OFF   position. During   emergency   single   engine   operation,   it   may become  necessary  to  supply  fuel  to  the  operative engine   from   the   fuel   system   on   the   opposite   side. The  crossfeed  system  is  placarded  for  fuel  selection with  a  simplified  diagram  on  the  overhead  fuel  con- trol  panel.  Place  the  standby  fuel  pump  switches  in the   off   position   when   crossfeeding.   A   lever   lock switch,  placarded  CROSSFEED,  is  moved  from  the center  OFF  position  to  the  left  or  to  the  right, depending  on  direction  of  fuel  flow.  This  opens  the crossfeed  valve  and  energizes  the  standby  pump  on the  side  from  which  crossfeed  is  desired.  During crossfeed   operation   with   firewall   fuel   valve   closed, auxiliary   tank   fuel   will   not   crossfeed.   When   the crossfeed  mode  is  energized,  a  green  FUEL  CROSS- FEED  light  on  the  caution/advisory  panel  will  illu- minate.   Crossfeed   system   operation   is   described   in Chapter  9.  The  crossfeed  valve  is  protected  by  a 5-ampere   circuit   breaker   placarded   CROSSFEED TM  55-1510-221-10 located   on   the   overhead   circuit   breaker   panel   (fig. 2-26). f.   Firewall   Shutoff   Valves. Do  not  use  the  fuel  firewall  shutoff  valve to  shut  down  an  engine,  except  in  an emergency. The   engine-driven   high- pressure  fuel  pump  obtains  essential lubrication  from  fuel  flow.  When  an engine  is  operating,  this  pump  may  be severely  damaged  (while  cavitating)  if  the firewall  valve  is  closed  before  the  condi- tion   lever   is   moved   to   the   FUEL   CUT- OFF   position. The  fuel  system  incorporates  a  fuel  line  shutoff valve  mounted  on  each  engine  firewall.  The  firewall shutoff   valves   close   automatically   when   the   fire extinguisher   T-handles   on   the   instrument   panel   are pulled  out.  The  firewall  shutoff  valves  receive  elec- trical  power  from  the  main  buses  and  also  from  the hot   battery   bus   which   is   connected   directly   to   the battery.  The  valves  are  protected  by  circuit  breakers placarded FIREWALL VALVE No. 1 or No. 2 on the overhead   circuit   breaker   panel   (fig.   2-26)   and FIREWALL  SHUTOFF  No.  1  or  No.  2  on  the  hot battery  bus  circuit  breaker  board. g.  Fuel  Tank  Sump  Drains.  A   sump   drain wrench  is  provided  in  the  aircraft  loose  tools  to  sim- plify  draining  a  small  amount  of  fuel  from  the  sump drain. (1.)  There  are  five  sump  drains  and  one filter  drain  in  each  wing  (Table  2-3). (2.)  An  additional  drain  for  the  extended range  fuel  system  line  extends  through  the  bottom  of the   wing   center   section   adjacent   to   the   fuselage. Anytime  the  extended  range  system  is  in  use,  a  part of  the  preflight  inspection  would  consist  of  draining a  small  amount  of  fuel  from  this  drain  to  check  for fuel  contamination.  Whenever  the  extended  range system  is  removed  from  the  aircraft  and  the  fuel  line is  capped  off  in  the  fuselage,  the  remaining  fuel  in the  line  shall  be  drained. h.  Fuel  Drain  Collector  System.  Each  engine  is provided  with  a  fuel  drain  collector  system  to  return fuel  dumped  from  the  engine  during  clearing  and shutdown  operations  back  into  its  respective  nacelle tank.  The  system  draws  power  from  the  No.  4  feeder bus.   Fuel   transfer   is   completely   automatic.   Fuel from  the  engine  flow  divider  drains  into  a  collector tank   mounted   below   the   aft   engine   accessory   sec- 2-33