TM 1-1500-204-23-3 Table 2-7.  Mixing Ratios Liquid dye NSN Unit of issue MIL-SPEC Mixing ratio Static Fuel System Tests Red 6820-00-926-8887 2 ounces MIL-D-81298 Add 2 ounces Red 6820-00-001-4192 1 gallon MIL-D-81298 to each 100 Yellow 6820-00-412-2296 1 gallon MIL-D-81298 gallons of fuel. Runup and In-flight Fuel System Tests Yellow 6820-00-412-2296 1 gallon MIL-D-81298 Add 1.6 ounces to each 100 gallons of fuel. (c)    Mixing in servicing vehicle.    The  dye  can  be  blended  in  a  refueling  vehicle  that  has  been  reserved  for servicing dyed fuel.  The required quantity of dye should be determined before starting.  To ensure proper mixing of dye in fuel, partially fill the trailer to about 10 percent and then add the appropriate amount of dye slowly to the contents of the trailer while the trailer is filled with remaining fuel. (d)    Static leak detection in fuel cells.  Use a diagram of the leaking fuel cell which slows all connections. 1    Transfer the fuel into another cell or defuel as necessary.  Pour the liquid dye into the leaking cell and fill to the 1/3 level with JP-4 fuel.  Allow the dye solution to set in the cell for approximately 6 hours or until the dye solution comes through the drain.  Should the dye appear, there is a leak within this level. NOTE One third level is determined from the known capacity of the cell; for example, 100 gallons added to a 300 gallon cell. 2    Repeat the procedure at the 2/3 level and full level, as necessary.  A full cell should be allowed to set for approximately 12 hours. 3    When  a  leak  is  detected,  connections  should  be  checked,  the  cell  defueled,  and  residual  fuel removed  with  cloths  and  drained  from  the  sump.    Type  MA-1  explosion  proof  blower  may  be  used  to  remove  fumes. Remove  all  connections,  pull  fuel  cell  down,  and  check  for  dye  stains  on  exterior  of  the  cell.    These  stains  are  easily detected,  thus  pinpointing  the  leak.    Rarely  is  any  maintenance  necessary  other  than  replacing  seals  and  retorquing connections. 4 Check for defective cells (blisters, layer separations, etc.) in accordance with the applicable fuel cell and/or aircraft maintenance manual. 5 After  closing  the  fuel  cell,  the  dye  solution  may  be  transferred  into  the  fuel  cell  once  more  to  the three levels: 1/3, 2/3, and full, thereby ascertaining whether or not the cell still leaks. 6 After completion of fuel cell leak detection operation, the aircraft may be flown with yellow dyed fuel. Red dyed fuel can be used provided it is diluted 10 parts to 1 part with undyed fuel in the fuel cell or cells.  If dilution is not possible, the aircraft will be defueled of dyed fuel which will be stored in a bulk storage tank. (e)    Static leak detection for fuel system including lines and engines.  Leakage checks of airframe mounted lines and connectors, and of integral wing and auxiliary fuel tanks may be undertaken using any of the dyes authorized herein.  However, when red dye is used the engine shall not be operated, and the aircraft shall be defueled of the dye fuel following testing.  Residual yellow dyed fuel need not be removed. (f)    Static-leak   detection   in   airframe   lines   and   fuel   cells.      If   only   the   airframe   mounted   fuel   lines   and connectors, or integral wing and auxiliary fuel cells are to be tested, allow the dyed fuel to stand in the aircraft 6 to 8 hours before performing leakage testing. 2-29