2-4.   Unit   Operation a.  General. (1)   The   tank   and   pump   unit   is   used   to dispense  all  types  of  automotive  and  aviation  fuel. However,  only  one  grade  of  fuel  should  be  carried in  and  dispensed  from  the  unit  at  a  time.  Since  the pumping   assembly   is   highly   adaptable,   dispensing with  the  tank  and  pump  unit  may  be  done  in  a variety  of  ways  to  meet  different  situations  in  the field.   This   paragraph   covers   some   common operational  procedures  for  the  tank  and  pump  unit in   the  field. All   aircraft   fuel   must   be   dispensed through  a  filter  /  separator  unit.  It  is mandatory   that   the   performance   of filter  /  separators  on  all  aircraft  refuel ing   equipment   be   checked   every   30 days   through   submission   of   samples taken   from   the   effluent   stream   of   the filter  /  separator. (2)  Upon  request,  the  petroleum    represen- tative  will  furnish  sample  containers  to  components of   the   Army,   Army   National   Guard,   or   Reserve operating   aircraft   refueling   equipment.   Samples will  be  sent  to  the  petroleum  laboratory  designated by  the  petroleum  representative.  In  the  event  that  a sample  indicates  unsatisfactory  performance  of filter   /   separator   equipment,   the   submitting   ac- tivity   will   be   notified   by   telephone   and   will   be advised   to   change   the   filter   /   separator   elements (AR  703-1,  1  Apr  1971). b.   Dispensing   from   Truck   Tanks   Through   Reels. Be   sure   proper   grounding   procedures have  been  followed  prior  to  performing any   of   the   following   operations. (1)  Lower  tailgate  and  ground  the  unit  (para 2-3).  Attach  one  end  of  the  ground  wire  to  the aircraft   or   vehicle   to   be   fueled. (2)  Pull  out  dispensing  hoses  to  desired  length. Attach  nozzle  bonding  wires  (fig.  1-3)  to  aircraft  or vehicle   before   opening   filler   caps   and   inserting nozzles. (3)  Insert  nozzles  in  vehicle  or  equipment  fuel tanks  carefully,  but  firmly,  to  form  a  bond;  observe safe  fueling  rates  stenciled  near  fuel  tanks. CAUTION When   dispensing   fuel,   attend   the nozzles  constantly;  do  not  wedge  open or  block  the  control  lever. (4)   Open   a   tank   discharge   valve   and   start pump.   Opening   a   discharge   valve   with   full   tanks should  prime  the  pump. (5)   Be   sure   that   fuel   to   be   dispensed   to   an aircraft  is  the  same  grade  as  that  stenciled  near  the aircraft  filler  caps;  note  tank  capacities  and  ask  the pilot   or   flight   engineer   for   estimate   of   quantities needed   to   avoid   spillage. NOTE When topping off small tanks, it may be necessary to reduce engine speed in order to reduce pressure surging at the hose and nozzle. Replace   filler   cap   securely   before removing  the  nozzle  bonding  wire. NOTE Recap, wind,   and secure nozzle bonding wire around  nozzles  when  through  dispensing. (6)  Open  second  discharge  valve  just  before first  tank  is  emptied,  and  close  first  discharge  valve when  the  tank  is  empty. (7)  Open  drain  valve  to  completely  drain  tank, then   close   drain   valve. (8)   Stop   pump   when   operation   is   completed; drain   hoses   if   shutting   down   for   longer   than overnight;   rewind  hoses,  rewind  ground  wire  and remove   nozzles   and   stow. (9)   Refill   tanks   at   the   end   of   the   day’s operation   to   reduce   condensation   during   overnight storage. 2-5.   Stopping Refer  to  figure  2-3  and  stop  the  engine. Figure   2-3.   Engine   stopping   instructions. 2-5